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Large-scale extreme-ultraviolet (EUV) waves commonly exhibit as single wavefront and are believed to be caused by coronal mass ejections (CMEs). Utilizing high spatiotemporal resolution imaging observations from the Solar Dynamics Observatory, we present two sequentially generated wave trains originating from the same active region: a narrow quasiperiodic fast-propagating (QFP) wave train that propagates along the coronal loop system above the jet and a broad QFP wave train that travels along the solar surface beneath the jet. The measurements indicate that the narrow QFP wave train and the accompanying flare's quasiperiodic pulsations (QPPs) have nearly identical onsets and periods. This result suggests that the accompanying flare process excites the observed narrow QFP wave train. However, the broad QFP wave train starts approximately 2 minutes before the QPPs of the flare, but consistent with the interaction between the unwinding jet and the solar surface. Moreover, we find that the \zxperiod of the broad QFP wave train, approximately 130\u2009s, closely matches that of the unwinding jet. This period is significantly longer than the 30\u2009s period of the accompanying flare's QPPs. Based on these findings, we propose that the intermittent energy release of the accompanying flare excited the narrow QFP wave train confined propagating in the coronal loop system. The unwinding jet, rather than the intermittent energy release in the accompanying flare, triggered the broad QFP wave train propagating along the solar surface.

This paper presents a detailed study of the physical properties of seven C IV absorbers identified at z_abs = 0.68-1.28 along the line of sight toward QSO PG 1522+101 (z_QSO = 1.330). The study leverages high-quality QSO spectra from HST COS and STIS, and Keck HIRES to resolve component structures and to constrain the gas density and elemental abundances of individual components. Under the assumption of photoionization equilibrium (PIE), five of the 12 C IV components require a mixture of high- and low-density phases to fully explain the observed relative abundances between low-, intermediate-, and high-ionization species. In addition, galaxy surveys carried out using VLT MUSE and Magellan LDSS3C are utilized to characterize the galaxy environments. The results of this analysis are summarized as follows: (1) no luminous galaxies (> 0.1 L*) are found within 100 kpc in projected distance from the C IV absorbers; (2) the C IV selection preferentially targets high-metallicity (near solar) and chemically-evolved gas (~ solar [C/O] elemental abundances) in galaxy halos; (3) the observed narrow line widths of individual C IV components, places a stringent limit on the gas temperature (< 5e4 K) and supports a photoionization origin; (4) additional local ionizing sources beyond the UV ionizing background may be necessary for at least one absorber based on the observed deficit of He I relative to H I; and (5) a PIE assumption may not apply when the gas metallicity exceeds the solar value and the component line width implies a warmer temperature than expected from PIE models.

The shallow potential wells of star-forming dwarf galaxies make their surrounding circumgalactic and intergalactic medium (CGM/IGM) sensitive laboratories for studying the inflows and outflows thought to regulate galaxy evolution. We present new absorption-line measurements in quasar sightlines probing within projected distances of $<300$ kpc from 91 star-forming field dwarf galaxies with a median stellar mass of $\log{M_\star/\rm{M_\odot}} \approx 8.3$ at $0.077 < z < 0.73$ from the Cosmic Ultraviolet Baryon Survey (CUBS). In this redshift range, the CUBS quasar spectra cover a suite of transitions including H I, low and intermediate metal ions (e.g., C II, Si II, C III, and Si III), and highly ionized O VI. This CUBS-Dwarfs survey enables constraints with samples 9$\times$ larger than past dwarf CGM/IGM studies with similar ionic coverage. We find that low and intermediate ionization metal absorption is rare around dwarf galaxies, consistent with previous surveys of local dwarfs. In contrast, highly ionized O VI is commonly observed in sightlines that pass within the virial radius of a dwarf, and O VI detection rates are non-negligible at projected distances of 1$-$2$\times$ the virial radius. Based on these measurements, we estimate that the O VI-bearing phase of the CGM/IGM accounts for a dominant share of the metal budget of dwarf galaxies. The absorption kinematics suggest that a relatively modest fraction of the O VI-bearing gas is formally unbound. Together, these results imply that low-mass systems at $z\lesssim 1$ effectively retain a substantial fraction of their metals within the nearby CGM and IGM.

We update the HI surface density measurements for a subset of 17 THINGS galaxies by dealing with the short-spacing problem of the original VLA HI images. It is the same sample that Bigiel et al. (2010) used to study the relation between HI surface densities and star formation rate surface densities in galaxy outer disks, which are beyond the optical radius r25. For ten galaxies, the update is based on combining original THINGS VLA HI images with HI images taken by the single-dish FAST in the FEASTS program. The median increment of HI surface densities in outer disks is 0.15 to 0.4 dex at a given new HI surface density. Several galaxies change significantly in the shape of radial profiles HI surface densities, and seven galaxies are now more than 1-$\sigma$ below the HI size-mass relation. We update the HI star formation laws in outer disks. The median relation between HI surface densities and star formation rate surface densities based on pixelwise measurements shifts downward by around 0.15 dex because the HI surface density values shift rightward, and the scatter increases significantly. The scatter of the relation, indicating the star forming efficiency, exhibits a much stronger positive correlation with the stellar mass surface density than before. Thus, detecting the previously missed, diffuse HI due to short-spacing problem of the VLA observation is important in revealing the true condition and variation of star formation possibly regulated by stellar feedbacks in localized environment of outer disks.

No progenitor of a Type Ia supernova is known, but in old population early-type galaxies, one may find SN Ia associated with globular clusters, yielding a population age and metallicity. It also provides insight into the formation path and the SN enhancement rate in globular clusters. We sought to find such associations and identified SN 2019ein to be within the ground-based optical positional uncertainty of a globular cluster candidate within the early-type galaxy NGC 5353 at about 30 Mpc distance. We reduced the positional uncertainties by obtaining Hubble Space Telescope images with the Advanced Camera for Surveys, using filters F475W and F814W and obtained in June 2020. We find that the globular cluster candidate has a magnitude, color, and angular extent that are consistent with it being a typical globular cluster. The separation between the globular cluster and SN 2019ein is 0.43'', or 59 pc in projection. The chance occurrence with a random globular cluster is about 3%, favoring but not proving an association. If the SN progenitor originated in the globular cluster, one scenario is that SN 2019ein was previously a double degenerate white dwarf binary that was dynamically ejected from the globular cluster and exploded within 10 Myr; models do not predict this to be common. Another, but less likely scenario is where the progenitor remained bound to the globular cluster, allowing the double degenerate binary to inspiral on a much longer timescale before producing a SN.

This paper presents three distinct wave trains that occurred on 2023 April 21: a broad quasi-periodic fast-propagating (QFP) wave train and a bi-directional narrow QFP wave train. The broad QFP wave train expands outward in a circular wavefront, while bi-directional narrow QFP wave trains propagate in the northward and southward directions, respectively. The concurrent presence of the wave trains offers a remarkable opportunity to investigate their respective triggering mechanisms. Measurement shows that the broad QFP wave train's speed is 300- 1100 km/s in different propagating directions. There is a significant difference in the speed of the bi-directional narrow QFP wave trains: the southward propagation achieves 1400 km/s, while the northward propagation only reaches about 550 km/s accompanied by a deceleration of about 1- 2 kms-2. Using the wavelet analysis, we find that the periodicity of the propagating wave trains in the southward and northward directions closely matches the quasi-periodic pulsations (QPPs) exhibited by the flares. Based on these results, the narrow QFP wave trains were most likely excited by the intermittent energy release in the accompanying flare. In contrast, the broad QFP wave train had a tight relationship with the erupting filament, probably attributed to the unwinding motion of the erupting filament or the leakage of the fast sausage wave train inside the filament body.

Solar corona has been judged to consist of free electrons and highly ionized ions with extremely high temperature as a widely accepted knowledge. This view is changed by our eclipse observations. Distributions of cool matter represented by neutral iron atoms in hot inner solar corona are presented via derived global maps of solar Fraunhofer(F-) and Emission(E-) coronae, compared with those of continuum(Kontinuierlich, K-) corona formed by free electrons. The maps are obtained from simultaneous observations of dual filtering bands centered respectively at 659.4nm and 660.1nm, performed from twin telescopes during the total solar eclipse on April 20, 2023 at Com town of East Timor, assisted for judgement via spectral images obtained by a portable spectrograph. They show respectively presences of these neutral iron atoms yielding 659.3nm and 659.4nm lines in both the quiet sun and active regions. The distribution of the cool matter in form of line depression forms an inner F-corona, different from that of the cool matter in form of line enhancement. Both the distributions show a crucial difference from that of the free electrons represented by the K-corona map. It is also found that intensities of the F-corona and the E-corona induced by these neutral atoms are only small fractions of the K-corona, and the diffusion can be seen clearly in all these maps. They uncover also that the coronal heating resources do not distribute pervasively but likely form a thermodynamic griddle where minor photospheric neutral atoms can escape from the heating into the corona globally.

The extraplanar diffuse ionized gas (eDIG) represents ionized gases traced by optical/UV lines beyond the stellar extent of galaxies. We herein introduce a novel multi-slit narrow-band spectroscopy method to conduct spatially resolved spectroscopy of the eDIG around a sample of nearby edge-on disk galaxies (eDIG-CHANGES). In this paper, we introduce the project design and major scientific goals, as well as a pilot study of NGC 3556 (M108). The eDIG is detected to a vertical extent of a few kpc above the disk, comparable to the X-ray and radio images. We do not see significant vertical variation of the [N II]/H$\alpha$ line ratio. A rough examination of the pressure balance between different circum-galactic medium (CGM) phases indicates the magnetic field is in a rough pressure balance with the X-ray emitting hot gas, and may play an important role in the global motion of both the eDIG and the hot gas in the lower halo. At the location of an HST/COS observed UV bright background AGN $\sim29\rm~kpc$ from the center of NGC 3556, the magnetic pressure is much lower than that of the hot gas and the ionized gas traced by UV absorption lines, although the extrapolation of the pressure profiles may cause some biases in this comparison. By comparing the position-velocity diagrams of the optical and CO lines, we also find the dynamics of the two gas phases are consistent with each other, with no evidence of a global inflow/outflow and a maximum rotation velocity of $\sim150\rm~km~s^{-1}$.

We report the discovery of large ionized, [O II] emitting circumgalactic nebulae around the majority of thirty UV luminous quasars at $z=0.4-1.4$ observed with deep, wide-field integral field spectroscopy (IFS) with the Multi-Unit Spectroscopy Explorer (MUSE) by the Cosmic Ultraviolet Baryon Survey (CUBS) and MUSE Quasar Blind Emitters Survey (MUSEQuBES). Among the 30 quasars, seven (23%) exhibit [O II] emitting nebulae with major axis sizes greater than 100 kpc, twenty greater than 50 kpc (67%), and 27 (90%) greater than 20 kpc. Such large, optically emitting nebulae indicate that cool, dense, and metal-enriched circumgalactic gas is common in the halos of luminous quasars at intermediate redshift. Several of the largest nebulae exhibit morphologies that suggest interaction-related origins. We detect no correlation between the sizes and cosmological dimming corrected surface brightnesses of the nebulae and quasar redshift, luminosity, black hole mass, or radio-loudness, but find a tentative correlation between the nebulae and rest-frame [O II] equivalent width in the quasar spectra. This potential trend suggests a relationship between ISM content and gas reservoirs on CGM scales. The [O II]-emitting nebulae around the $z\approx1$ quasars are smaller and less common than Ly$\alpha$ nebulae around $z\approx3$ quasars. These smaller sizes can be explained if the outer regions of the Ly$\alpha$ halos arise from scattering in more neutral gas, by evolution in the cool CGM content of quasar host halos, by lower-than-expected metallicities on $\gtrsim50$ kpc scales around $z\approx1$ quasars, or by changes in quasar episodic lifetimes between $z=3$ and $1$.

Spectropolarimetric results of Fraunhofer lines between 516.3nm and 532.6nm are presented in local upper solar chromosphere, transition zone and inner corona below a height of about 0.04 solar radius above the solar limb. The data were acquired on Nov.3, 2013 during a total solar eclipse in Gabon by the prototype Fiber Arrayed Solar Optical Telescope(FASOT). It is found that the polarization amplitudes of the Fraunhofer lines in these layers depend strongly on specific spectral lines. Fraunhofer line at MgI$b_{1}$518.4nm can have a polarization amplitude up to 0.36$\%$ with respective to the continuum polarization level, while the polarizations of some lines like FeI/CrI524.7nm and FeI525.0nm are often under the detection limit 6.0$\times 10^{-4}$. The polarizations of the Fraunhofer lines, like the emission lines and the continuum, increase with height as a whole trend. The fractional linear polarization amplitudes of inner F-corona can be close to those of inner E-corona, and in general larger than those of inner K-corona. Rotation of the polarization direction of Fraunhofer line is often accompanied with variations in their polarization amplitudes and profile shapes. It is also judged from these polarimetric properties, along with evidences, that neutral atoms exist in these atmospheric layers. Thus the inner F-corona described here is induced by the neutral atoms, and the entropy of the inner corona evaluated becomes larger than those in the underneath layers due to more microstates found.

This paper presents the multi-scale temperature structures in the Milky Way (MW) hot gas, as part of the XMM-Newton Line Emission Analysis Program (X-LEAP), surveying the O VII, O VIII, and Fe-L band emission features in the XMM-Newton archive. In particular, we define two temperature tracers, $I_{\rm OVIII}/I_{\rm OVII}$ (O87) and $I_{\rm FeL}/(I_{\rm OVII}+I_{\rm OVIII})$ (FeO). These two ratios cannot be explained simultaneously using single-temperature collisional ionization models, which indicates the need for multi-temperature structures in hot gas. In addition, we show three large-scale features in the hot gas: the eROSITA bubbles around the Galactic center (GC); the disk; and the halo. In the eROSITA bubbles, the observed line ratios can be explained by a log-normal temperature distribution with a median of $\log T/{\rm K} \approx 6.4$ and a scatter of $\sigma_T \approx 0.2$ dex. Beyond the bubbles, the line ratio dependence on the Galactic latitude suggests higher temperatures around the midplane of the MW disk. The scale height of the temperature variation is estimated to be $\approx$2 kpc assuming an average distance of $5$ kpc for the hot gas. The halo component is characterized by the dependence on the distance to the GC, showing a temperature decline from $\log\,T/{\rm K}\,\approx\, 6.3$ to $5.8$. Furthermore, we extract the auto-correlation and cross-correlation functions to investigate the small-scale structures. O87 and FeO ratios show a consistent auto-correlation scale of $\approx$$ 5^\circ$ (i.e., $\approx$$ 400$ pc at 5 kpc), which is consistent with expected physical sizes of X-ray bubbles associated with star-forming regions or supernova remnants. Finally, we examine the cross-correlation between the hot and UV-detected warm gas, and show an intriguing anti-correlation.

We investigate the group-scale environment of 15 luminous quasars (luminosity $L_{\rm 3000}>10^{46}$ erg s$^{-1}$) from the Cosmic Ultraviolet Baryon Survey (CUBS) at redshift $z\approx1$. Using the Multi Unit Spectroscopic Explorer (MUSE) integral field spectrograph on the Very Large Telescope (VLT), we conduct a deep galaxy redshift survey in the CUBS quasar fields to identify group members and measure the physical properties of individual galaxies and galaxy groups. We find that the CUBS quasars reside in diverse environments. The majority (11 out of 15) of the CUBS quasars reside in overdense environments with typical halo masses exceeding $10^{13}{\rm M}_{\odot}$, while the remaining quasars reside in moderate-size galaxy groups. No correlation is observed between overdensity and redshift, black hole (BH) mass, or luminosity. Radio-loud quasars (5 out of 15 CUBS quasars) are more likely to be in overdense environments than their radio-quiet counterparts in the sample, consistent with the mean trends from previous statistical observations and clustering analyses. Nonetheless, we also observe radio-loud quasars in moderate groups and radio-quiet quasars in overdense environments, indicating a large scatter in the connection between radio properties and environment. We find that the most UV luminous quasars might be outliers in the stellar mass-to-halo mass relations or may represent departures from the standard single-epoch BH relations.

The XMM-Newton Line Emission Analysis Program (X-LEAP) is designed to study diffuse X-ray emissions from the Milky Way (MW) hot gas, as well as emissions from the foreground solar wind charge exchange (SWCX). This paper reports an all-sky survey of spectral feature intensities corresponding to the O VII, O VIII, and iron L-shell (Fe-L) emissions. These intensities are derived from 5418 selected XMM-Newton observations with long exposure times and minimal contamination from point or extended sources. For 90% of the measured intensities, the values are within $\approx$ 2-18 photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$ (line unit; L.U.), $\approx$ 0-8 L.U., and $\approx$ 0-9 L.U., respectively. We report long-term variations in O VII and O VIII intensities over 22 years, closely correlating with the solar cycle and attributed to SWCX emissions. These variations contribute $\sim30\%$ and $\sim20\%$ to the observed intensities on average and peak at $\approx$ 4 L.U. and $\approx$ 1 L.U. during solar maxima. We also find evidence of short-term and spatial variations in SWCX, indicating the need for a more refined SWCX model in future studies. In addition, we present SWCX- and absorption-corrected all-sky maps for a better view of the MW hot gas emission. These maps show a gradual decrease in oxygen intensity moving away from the Galactic center and a concentration of Fe-L intensity in the Galactic bubbles and disk.

This paper presents a newly established sample of 103 unique galaxies or galaxy groups at $0.4\lesssim z\lesssim 0.7$ from the Cosmic Ultraviolet Baryon Survey (CUBS) for studying the warm-hot circumgalactic medium (CGM) probed by both O VI and Ne VIII absorption. The galaxies and associated neighbors are identified at $< 1$ physical Mpc from the sightlines toward 15 CUBS QSOs at $z_{\rm QSO}\gtrsim 0.8$. A total of 30 galaxies or galaxy groups exhibit associated O VI $\lambda\lambda$ 1031, 1037 doublet absorption within a line-of-sight velocity interval of $\pm250$ km/s, while the rest show no trace of O VI to a detection limit of $\log N_{\rm OVI}/{\rm cm^{-2}}\approx13.7$. Meanwhile, only five galaxies or galaxy groups exhibit the Ne VIII $\lambda\lambda$ 770,780 doublet absorption, down to a limiting column density of $\log N_{\rm NeVIII}/{\rm cm^{-2}}\approx14.0$. These O VI- and Ne VIII-bearing halos reside in different galaxy environments with stellar masses ranging from $\log M_{\rm star}/M_\odot \approx 8$ to $\approx11.5$. The warm-hot CGM around galaxies of different stellar masses and star formation rates exhibits different spatial profiles and kinematics. In particular, star-forming galaxies with $\log M_{\rm star}/M_\odot\approx9-11$ show a significant concentration of metal-enriched warm-hot CGM within the virial radius, while massive quiescent galaxies exhibit flatter radial profiles of both column densities and covering fractions. In addition, the velocity dispersion of O VI absorption is broad with $\sigma_v > 40$ km/s for galaxies of $\log M_{\rm star}/M_\odot>9$ within the virial radius, suggesting a more dynamic warm-hot halo around these galaxies. Finally, the warm-hot CGM probed by O VI and Ne VIII is suggested to be the dominant phase in sub-$L^*$ galaxies with $\log M_{\rm star}/M_\odot\approx9-10$ based on their high ionization fractions in the CGM.

All-sky maps of the thermal Sunyaev-Zel'dovich effect (SZ) tend to suffer from systematic features arising from the component separation techniques used to extract the signal. In this work, we investigate one of these methods known as needlet internal linear combination (NILC) and test its performance on simulated data. We show that NILC estimates are strongly affected by the choice of the spatial localization parameter ($\Gamma$), which controls a bias-variance trade-off. Typically, NILC extractions assume a fixed value of $\Gamma$ over the entire sky, but we show there exists an optimal $\Gamma$ that depends on the SZ signal strength and local contamination properties. Then we calculate the NILC solutions for multiple values of $\Gamma$ and feed the results into a neural network to predict the SZ signal. This extraction method, which we call Deep-NILC, is tested against a set of validation data, including recovered radial profiles of resolved systems. Our main result is that Deep-NILC offers significant improvements over choosing fixed values of $\Gamma$.

We present a flare star catalog from four years of non-targeted millimeter-wave survey data from the South Pole Telescope (SPT). The data were taken with the SPT-3G camera and cover a 1500-square-degree region of the sky from $20^{h}40^{m}0^{s}$ to $3^{h}20^{m}0^{s}$ in right ascension and $-42^{\circ}$ to $-70^{\circ}$ in declination. This region was observed on a nearly daily cadence from 2019-2022 and chosen to avoid the plane of the galaxy. A short-duration transient search of this survey yields 111 flaring events from 66 stars, increasing the number of both flaring events and detected flare stars by an order of magnitude from the previous SPT-3G data release. We provide cross-matching to Gaia DR3, as well as matches to X-ray point sources found in the second ROSAT all-sky survey. We have detected flaring stars across the main sequence, from early-type A stars to M dwarfs, as well as a large population of evolved stars. These stars are mostly nearby, spanning 10 to 1000 parsecs in distance. Most of the flare spectral indices are constant or gently rising as a function of frequency at 95/150/220 GHz. The timescale of these events can range from minutes to hours, and the peak $\nu L_{\nu}$ luminosities range from $10^{27}$ to $10^{31}$ erg s$^{-1}$ in the SPT-3G frequency bands.

Double-decker filaments and their eruptions have been widely observed in recent years, but their physical formation mechanism is still unclear. Using high spatiotemporal resolution, multi-wavelength observations taken by the New Vacuum Solar Telescope and the Solar Dynamics Observatory, we show the formation of a double-decker pair of flux rope system by two successive tether-cutting eruptions in a bipolar active region. Due to the combined effect of photospheric shearing and convergence motions around the active region's polarity inversion line (PIL), the arms of two overlapping inverse-S-shaped short filaments reconnected at their intersection, which created a simultaneous upward-moving magnetic flux rope (MFR) and a downward-moving post-flare-loop (PFL) system striding the PIL. Meanwhile, four bright flare ribbons appeared at the footpoints of the newly formed MFR and the PFL. As the MFR rose, two elongated flare ribbons connected by a relatively larger PFL appeared on either side of the PIL. After a few minutes, another MFR formed in the same way at the same location and then erupted in the same direction as the first one. Detailed observational results suggest that the eruption of the first MFR might experienced a short pause before its successful eruption, while the second MFR was a failed eruption. This implies that the two newly formed MFRs might reach a new equilibrium at relatively higher heights for a while, which can be regarded as a transient double-decker flux rope system. The observations can well be explained by the tether-cutting model, and we propose that two successive confined tether-cutting eruptions can naturally produce a double-decker flux rope system, especially when the background coronal magnetic field has a saddle-like distribution of magnetic decay index profile in height.

The decay of sunspot plays a key role in magnetic flux transportation in solar active regions (ARs). To better understand the physical mechanism of the entire decay process of a sunspot, an \alpha-configuration sunspot in AR NOAA 12411 was studied. Based on the continuum intensity images and vector magnetic field data with stray light correction from Solar Dynamics Observatory/Helioseismic and Magnetic Imager, the area, vector magnetic field and magnetic flux in the umbra and penumbra are calculated with time, respectively. Our main results are as follows: (1) The decay curves of the sunspot area in its umbra, penumbra, and whole sunspot take the appearance of Gaussian profiles. The area decay rates of the umbra, penumbra and whole sunspot are -1.56 MSH/day, -12.61 MSH/day and -14.04 MSH/day, respectively; (2) With the decay of the sunspot, the total magnetic field strength and the vertical component of the penumbra increase, and the magnetic field of the penumbra becomes more vertical. Meanwhile, the total magnetic field strength and vertical magnetic field strength for the umbra decrease, and the inclination angle changes slightly with an average value of about 20\deg; (3) The magnetic flux decay curves of the sunspot in its umbra, penumbra, and whole sunspot exhibit quadratic patterns, their magnetic flux decay rates of the umbra, penumbra and whole sunspot are -9.84 * 10^19 Mx/day, -1.59 * 10^20 Mx/day and -2.60 * 10^20 Mx/day , respectively. The observation suggests that the penumbra may be transformed into the umbra, resulting in the increase of the average vertical magnetic field strength and the reduction of the inclination angle in the penumbra during the decay of the sunspot.

The relationship between the decay of sunspots and moving magnetic features (MMFs) plays an important role in understanding the evolution of active regions. We present observations of two adjacent sunspots, the gap between them, and a lot of MMFs propagating from the gap and the sunspots' outer edges in NOAA Active Region 13023. The MMFs are divided into two types based on their magnetic field inclination angle: vertical (0\deg<\gamma<45\deg) and horizontal (45\deg<\gamma<90\deg) MMFs (V-MMFs and H-MMFs, respectively). The main results are as follows: (1) the mean magnetic flux decay rates of the two sunspots are -1.7*10^20 and -1.4*10^20 Mx/day; (2) the magnetic flux generation rate of all MMFs is calculated to be -1.9 *10^21 Mx/day, which is on average 5.6 times higher than the total magnetic flux loss rate of the sunspots; (3) the magnetic flux of V-MMFs (including a pore separated from the sunspots) is 1.4 times larger than the total lost magnetic flux of the two sunspots, and in a later stage when the pore has passed through the reference ellipse, the magnetic flux generation rate of the V-MMFs is almost the same as the magnetic flux loss rate of the sunspots; and (4) within the gap, the magnetic flux of V-MMFs is one third of the total magnetic flux. Few V-MMFs stream out from the sunspots at the nongap region. All observations suggest that MMFs with vertical magnetic fields are closely related to the disintegration of the sunspot, and most of the MMFs from the gap may originate directly from the sunspot umbra.

Turbulent motions in the circumgalactic medium (CGM) play a critical role in regulating the evolution of galaxies, yet their detailed characterization remains elusive. Using two-dimensional velocity maps constructed from spatially-extended [OII] and [OIII] emission, Chen et al. (2023b) measured the velocity structure functions (VSFs) of four quasar nebulae at $z\approx\!0.5$--1.1. One of these exhibits a spectacular Kolmogorov relation. Here we carry out an ensemble study using an expanded sample incorporating four new nebulae from three additional QSO fields. The VSFs measured for all eight nebulae are best explained by subsonic turbulence revealed by the line-emitting gas, which in turn strongly suggests that the cool gas ($T\!\sim\!10^4$ K) is dynamically coupled to the hot ambient medium. Previous work demonstrates that the largest nebulae in our sample reside in group environments with clear signs of tidal interactions, suggesting that environmental effects are vital in seeding and enhancing turbulence within the gaseous halos, ultimately promoting the formation of the extended nebulae. No discernible differences are observed in the VSF properties between radio-loud and radio-quiet QSO fields. We estimate the turbulent heating rate per unit volume, $Q_{\rm turb}$, in the QSO nebulae to be $\sim 10^{-26}$--$10^{-22}$ erg cm$^{-3}$ s$^{-1}$ for the cool phase and $\sim 10^{-28}$--$10^{-25}$ erg cm$^{-3}$ s$^{-1}$ for the hot phase. This range aligns with measurements in the intracluster medium and star-forming molecular clouds but is $\sim10^3$ times higher than the $Q_{\rm turb}$ observed inside cool gas clumps on scales $\lesssim1$ kpc using absorption-line techniques. We discuss the prospect of bridging the gap between emission and absorption studies by pushing the emission-based VSF measurements to below $\approx\!10$ kpc.

The core-collapse supernova (CCSN) is considered one of the most energetic astrophysical events in the universe. The early and prompt detection of neutrinos before (pre-SN) and during the supernova (SN) burst presents a unique opportunity for multi-messenger observations of CCSN events. In this study, we describe the monitoring concept and present the sensitivity of the system to pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton liquid scintillator detector currently under construction in South China. The real-time monitoring system is designed to ensure both prompt alert speed and comprehensive coverage of progenitor stars. It incorporates prompt monitors on the electronic board as well as online monitors at the data acquisition stage. Assuming a false alert rate of 1 per year, this monitoring system exhibits sensitivity to pre-SN neutrinos up to a distance of approximately 1.6 (0.9) kiloparsecs and SN neutrinos up to about 370 (360) kiloparsecs for a progenitor mass of 30 solar masses, considering both normal and inverted mass ordering scenarios. The pointing ability of the CCSN is evaluated by analyzing the accumulated event anisotropy of inverse beta decay interactions from pre-SN or SN neutrinos. This, along with the early alert, can play a crucial role in facilitating follow-up multi-messenger observations of the next galactic or nearby extragalactic CCSN.

This paper reports the first measurement of the relationship between turbulent velocity and cloud size in the diffuse circumgalactic medium (CGM) in typical galaxy halos at redshift z~0.4-1. Through spectrally-resolved absorption profiles of a suite of ionic transitions paired with careful ionization analyses of individual components, cool clumps of size as small as l_cl~1 pc and density lower than nH = 0.001 cm^-3 are identified in galaxy halos. In addition, comparing the line widths between different elements for kinematically matched components provides robust empirical constraints on the thermal temperature T and the non-thermal motions bNT, independent of the ionization models. On average, bNT is found to increase with l_cl following bNT ∝l_cl^0.3 over three decades in spatial scale from l_cl~1 pc to l_cl~1 kpc. Attributing the observed bNT to turbulent motions internal to the clumps, the best-fit bNT-l_cl relation shows that the turbulence is consistent with Kolmogorov at <1 kpc with a roughly constant energy transfer rate per unit mass of epsilon~0.003 cm^2 s^-3 and a dissipation time scale of <~ 100 Myr. No significant difference is found between massive quiescent and star-forming halos in the sample on scales less than 1 kpc. While the inferred epsilon is comparable to what is found in CIV absorbers at high redshift, it is considerably smaller than observed in star-forming gas or in extended line-emitting nebulae around distant quasars. A brief discussion of possible sources to drive the observed turbulence in the cool CGM is presented.

The Hot Universe Baryon Surveyor (HUBS) is a proposed space-based X-ray telescope for detecting X-ray emissions from the hot gas content in our universe. With its unprecedented spatially-resolved high-resolution spectroscopy and large field of view, the HUBS mission will be uniquely qualified to measure the physical and chemical properties of the hot gas in the interstellar medium, the circumgalactic medium, the intergalactic medium, and the intracluster medium. These measurements will be valuable for two key scientific goals of HUBS, namely to unravel the AGN and stellar feedback physics that governs the formation and evolution of galaxies, and to probe the baryon budget and multi-phase states from galactic to cosmological scales. In addition to these two goals, the HUBS mission will also help us solve some problems in the fields of galaxy clusters, AGNs, diffuse X-ray backgrounds, supernova remnants, and compact objects. This paper discusses the perspective of advancing these fields using the HUBS telescope.

In this paper, we explore the possibility of measuring the complete polarizations of cosmic photons $\gamma$ and the polarizations of cosmic electrons $e^{-}$ and positrons $e^{+}$. Our innovative Vector Meson Photo-production induced polarimetry enables people to measure the circular plarization compoent of a $GeV$ $\gamma$ and to improve its linear polarization measurement, and thus enables people to measure the polarization of $GeV$ $e^{+}/e^{-}$ for the first time. We calculate the production process of $\pi^{+}\pi^{-}$ by a generally polarized photon near nucleon's field in a generalized VPD-SDMEs Factorization with the fitted experimental data, so that it's partially model-independent. We also propose the observables and approach to measure their polarizations based on our calculations. Our new polarimetry of high-energy cosmic $\gamma,e^{+},e^{-}$ will open a new window to reveal the mysteries and solve the puzzles of BSM new physics in particle physics and cosmology.

Focal Ratio Degradation (FRD) in fibres is a crucial factor to control in astronomical instruments in order to minimize light loss. As astronomical instrumentation has advanced, the integration of large populations of fibres has become common. However, determining FRD in multiplexed fibre systems has become a challenging and time-consuming task. The Integral Field Unit for the Fiber Arrayed Solar Optical Telescope (FASOT-IFU) represents the most densely arranged fibre-based IFU in a single unit. Due to the close packing of fibres in the V-groove of the slit end, measuring FRD is particularly challenging as the output spots are prone to overlapping with adjacent fibres. In this paper, a novel method based on the quasi-near field model is proposed to enable rapid FRD measurement in highly multiplexed fibre systems like IFUs and multi-object observation systems. The principle and uncertainties associated with the method are investigated. The method's validity is demonstrated by applying it to determine the FRD in FASOT-IFU, with the achieved FRD performance meeting the acceptable requirements of FASOT-IFU, where the output focal ratio primarily falls within the range of 5.0-7.0. The results indicate that the proposed method offers several advantages, including the simultaneous and rapid measurement of FRD in multiple fibres with high accuracy (error smaller than 0.35 in F-ratio). Furthermore, besides FRD, the method exhibits potential for extensive measurements of throughput, scrambling, and spectral analysis.

We introduce the New-ANGELS program, an XMM-Newton survey of $\sim7.2\rm~deg^2$ area around M 31, which aims to study the X-ray populations in M 31 disk and the X-ray emitting hot gas in the inner halo of M 31 up to 30 kpc. In this first paper, we report the catalogue of 4506 detected X-ray sources, and attempt to cross-identify or roughly classify them. We identify 352 single stars in the foreground, 35 globular clusters and 27 supernova remnants associated with M 31, as well as 62 AGNs, 59 galaxies, and 1 galaxy clusters in the background. We uniquely classify 236 foreground stars and 17 supersoft sources based on their X-ray colors. X-ray binaries (83 LMXBs, 1 HMXBs) are classified based on their X-ray colors and X-ray variabilities. The remaining X-ray sources either have too low S/N to calculate their X-ray colors or do not have a unique classification, so are regarded as unclassified. The X-ray source catalogue is published online. Study of the X-ray source populations and the contribution of X-ray sources in the unresolved X-ray emissions based on this catalogue will be published in companion papers.

This paper presents a new sample of 19 unique galaxies and galaxy groups at $z\approx1$ from the CUBS program, which is designated as the CUBSz1 sample. In this CUBSz1 sample, nine galaxies or galaxy groups show absorption features, while ten systems do not have detectable absorption with 2-$\sigma$ upper limits of log$N$(HeI)/cm$^{-2}\lesssim 13.5$ and log$N$(OV)/cm$^{-2}\lesssim 13.3$. Environmental properties of the galaxies, including galaxy overdensities, the total stellar mass and gravitational potential summed over all nearby neighbors, and the presence of local ionizing sources, are found to have a significant impact on the observed CGM absorption properties. Specifically, massive galaxies and galaxies in overdense regions exhibit a higher rate of incidence of absorption. At the same time, the observed CGM absorption properties in galaxy groups appear to be driven by the galaxy closest to the QSO sightline, rather than by the most massive galaxy or by mass-weighted properties. We introduce a total projected gravitational potential $\psi$, defined as $-\psi/G =\sum M_{{\rm halo}}/d_{{\rm proj}}$ summed over all group members, to characterize the overall galaxy environment. This projected gravitational potential correlates linearly with the maximum density detected in each sightline, consistent with higher-pressure gas being confined in deeper gravitational potential wells. In addition, we find that the radial profile of cool gas density exhibits a general decline from the inner regions to the outskirts, being in pressure balance with the hot halo. Finally, we note that the ionizing flux from nearby galaxies can generate an elevated $N$(HI)/$N$(HeI) ratio, which in turn provides a unique diagnostic of possible local sources contributing to the ionizing radiation field.

The extraplanar diffuse ionized gas (eDIG) represents the cool/warm ionized gas reservoir around galaxies. We present a spatial analysis of H$\alpha$ images of 22 nearby edge-on spiral galaxies from the CHANG-ES sample (the eDIG-CHANGES project), taken with the APO 3.5m telescope, in order to study their eDIG. We conduct an exponential fit to the vertical intensity profiles of the sample galaxies, of which 16 can be decomposed into a thin disk plus an extended thick disk component. The median value of the scale height (h) of the extended component is $1.13\pm 0.14$ kpc. We find a tight sublinear correlation between h and the SFR. Moreover, the offset of individual galaxies from the best-fit SFR-h relation shows significant anti-correlation with SFR_SD. This indicates that galaxies with more intense star formation tend to have disproportionately extended eDIG. Combined with data from the literature, we find that the correlations between the eDIG properties and the galaxies' properties extend to broader ranges. We further compare the vertical extension of the eDIG to multi-wavelength measurements of other CGM phases. We find the eDIG to be slightly more extended than the neutral gas (HI 21-cm line), indicating the existence of some extended ionizing sources. Most galaxies have an X-ray scale height smaller than the h, suggesting that the majority of the X-ray emission detected in shallow observations are actually from the thick disk. The h is comparable to the L-band radio continuum scale height, both slightly larger than that at higher frequencies (C-band), where the cooling is stronger and the thermal contribution may be larger. The comparable H$\alpha$ and L-band scale height indicates that the thermal and non-thermal electrons have similar spatial distributions. This further indicates that the thermal gas, the cosmics rays, and the magnetic field may be close to energy equipartition.

About the driven mechanisms of the quasi-periodic fast-propagating (QFP) wave trains, there exist two dominant competing physical explanations: associated with the flaring energy release or attributed to the waveguide dispersion. Employing Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) 171 A images, we investigated a series of QFP wave trains composed of multiple wavefronts propagating along a loop system during the accompanying flare on 2011 November 11. The wave trains showed a high correlation in start time with the energy release of the accompanying flare. Measurements show that the wave trains phase speed is almost consistent with its group speed with a value of about 1000 km s-1, indicating that the wave trains should not be dispersed waves. The period of the wave trains was the same as that of the oscillatory signal in X ray emissions released by the flare. Thus we propose that the QFP wave trains were most likely triggered by the flare rather than by dispersion. We investigated the seismological application with the QFP waves and then obtained that the magnetic field strength of the waveguide was about 10 Gauss. Meanwhile, we also estimated that the energy flux of the wave trains was about 1.2X105 erg cm-2 s-1.

We present the first empirical constraints on the turbulent velocity field of the diffuse circumgalactic medium around four luminous QSOs at $z\!\approx\!0.5$--1.1. Spatially extended nebulae of $\approx\!50$--100 physical kpc in diameter centered on the QSOs are revealed in [OII]$\lambda\lambda\,3727,3729$ and/or [OIII]$\lambda\,5008$ emission lines in integral field spectroscopic observations obtained using MUSE on the VLT. We measure the second- and third-order velocity structure functions (VSFs) over a range of scales, from $\lesssim\!5$ kpc to $\approx\!20$--50 kpc, to quantify the turbulent energy transfer between different scales in these nebulae. While no constraints on the energy injection and dissipation scales can be obtained from the current data, we show that robust constraints on the power-law slope of the VSFs can be determined after accounting for the effects of atmospheric seeing, spatial smoothing, and large-scale bulk flows. Out of the four QSO nebulae studied, one exhibits VSFs in spectacular agreement with the Kolmogorov law, expected for isotropic, homogeneous, and incompressible turbulent flows. The other three fields exhibit a shallower decline in the VSFs from large to small scales. However, with a limited dynamic range in the spatial scales in seeing-limited data, no constraints can be obtained for the VSF slopes of these three nebulae. For the QSO nebula consistent with the Kolmogorov law, we determine a turbulence energy cascade rate of $\approx\!0.2$ cm$^{2}$ s$^{-3}$. We discuss the implication of the observed VSFs in the context of QSO feeding and feedback in the circumgalactic medium.

This paper presents a systematic study of the photoionization and thermodynamic properties of the cool circumgalactic medium (CGM) as traced by rest-frame ultraviolet absorption lines around 26 galaxies at redshift $z\lesssim1$. The study utilizes both high-quality far-ultraviolet and optical spectra of background QSOs and deep galaxy redshift surveys to characterize the gas density, temperature, and pressure of individual absorbing components and to resolve their internal non-thermal motions. The derived gas density spans more than three decades, from $\log (n_{\rm H}/{\rm cm^{-3}}) \approx -4$ to $-1$, while the temperature of the gas is confined in a narrow range of $\log (T/{\rm K})\approx 4.3\pm 0.3$. In addition, a weak anti-correlation between gas density and temperature is observed, consistent with the expectation of the gas being in photoionization equilibrium. Furthermore, decomposing the observed line widths into thermal and non-thermal contributions reveals that more than 30% of the components at $z\lesssim 1$ exhibit line widths driven by non-thermal motions, in comparison to $<20$% found at $z\approx 2$-3. Attributing the observed non-thermal line widths to intra-clump turbulence, we find that massive quenched galaxies on average exhibit higher non-thermal broadening/turbulent energy in their CGM compared to star-forming galaxies at $z\lesssim 1$. Finally, strong absorption features from multiple ions covering a wide range of ionization energy (e.g., from Mg II to O IV) can be present simultaneously in a single absorption system with kinematically aligned component structure, but the inferred pressure in different phases may differ by a factor of $\approx 10$.

Quasi-periodic fast-propagating (QFP) magnetosonic wave trains are commonly observed in the low corona at extreme ultraviolet wavelength bands. Here, we report the first white-light imaging observation of a QFP wave train propagating outwardly in the outer corona ranging from 2 to 4 solar Radii. The wave train was recorded by the Large Angle Spectroscopic Coronagraph on board the Solar and Heliospheric Observatory, and it was associated with a GOES M1.5 flare in NOAA active region AR12172 at the southwest limb of the solar disk. Measurements show that the speed and period of the wave train were about 218 km/s and 26 minutes, respectively. The extreme ultraviolet imaging observations taken by the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory reveals that in the low corona the QFP wave train was associated with the failed eruption of a breakout magnetic system consisting of three low-lying closed loop systems enclosed by a high-lying large-scale one. Data analysis results show that the failed eruption of the breakout magnetic system was mainly because of the magnetic reconnection occurred between the two sided low-lying closed-loop systems. This reconnection enhances the confinement capacity of the magnetic breakout system because the upward-moving reconnected loops continuously feed new magnetic fluxes to the high-lying large-scale loop system. For the generation of the QFP wave train, we propose that it could be excited by the intermittent energy pulses released by the quasi-periodic generation, rapid stretching and expansion of the upward-moving, strongly bent reconnected loops.

Solar wind charge exchange (SWCX) is the primary contamination to soft X-ray emission lines from the Milky Way (MW) hot gas. We report a solar-cycle ($\approx 10$ yr) temporal variation of observed \ionO7 and \ionO8 emission line measurements in the \it XMM-Newton archive, which is tightly correlated with the solar cycle traced by the sunspot number (SSN). This temporal variation is expected to be associated with the heliospheric SWCX. Another observed correlation is that higher solar wind (SW) fluxes lead to higher O VII or O VIII fluxes, which is due to the magnetospheric SWCX. We construct an empirical model to reproduce the observed correlation between the line measurements and the solar activity (i.e., the SW flux and the SSN). With this model we discovered a lag of $0.91_{-0.22}^{+0.20}$ yr between the O VII flux and the SSN. This time lag is a combination of the SW transit time within the heliosphere, the lag of the neutral gas distribution responding to solar activity, and the intrinsic lag between the SSN and the launch of a high-energy SW (i.e., $\rm O^{7+}$ and $\rm O^{8+}$). MW O VII and O VIII fluxes have mean values of 5.4 L.U. and 1.7 L.U., which are reduced by $50\%$ and $30\%$, compared to studies where the SWCX contamination is not removed. This correction also changes the determination of the density distribution and the temperature profile of the MW hot gas.

Dwarf galaxies are missing nearly all of their baryons and metals from the stellar disk, presumed to be in a bound halo or expelled beyond the virial radius. The virial temperature for galaxies with $M_{\rm h} \sim 10^9 - 10^{10}$ $M_{\odot}$ is similar to the collisional ionization equilibrium temperature for the C IV ion. We searched for UV absorption from C IV in six sightlines toward three dwarf galaxies in the anti-M31 direction and at the periphery of the Local Group ($D \approx$ 1.3 Mpc; Sextans A, Sextans B, and NGC 3109). The C IV doublet is detected in only one of six sightlines, toward Sextans A, with $\log N({\rm C IV})$ = $13.06 \pm 0.08$. This is consistent with our gaseous halo models, where the halo gas mass is determined by the cooling rate, feedback, and the star formation rate; the inclusion of photoionization is an essential ingredient. This model can also reproduce the higher detection rate of O VI absorption in other dwarf samples (beyond the Local Group), and with C IV only detectable within $\sim 0.5R_{\rm vir}$.

We compose a 265-sight line MW C IV line shape sample using the HST/COS archive, which is complementary to the existing Si IV samples. C IV has a higher ionization potential ($47 - 64$ eV) than Si IV ($33 - 45$ eV), so it also traces warm gas, which is roughly cospatial with Si IV. The spatial density distribution and kinematics of C IV is identical with Si IV within $\approx 2 \sigma$. C IV is more sensitive to the warm gas density distribution at large radii with a higher element abundance. Applying the kinematical model to the C IV sample, we find two possible solutions of the density distribution, which are distinguished by the relative extension along the disk mid-plane and the normal-line direction. Both two solutions can reproduce the existing sample, and suggest a warm gas disk mass of $\log M(M_\odot) \approx 8$ and an upper limit of $\log M(M_\odot) < 9.3$ within 250 kpc, which is consistent with Si IV. There is a decrease of the C IV/Si IV column density ratio from the Galactic center to outskirts by $0.2-0.3$ dex, which may suggest a phase transition or different ionization mechanisms for C IV and Si IV. Also, we find that the difference between C IV and Si IV is an excellent tracer of small-scale features, and we find a typical size of $5^\circ-10^\circ$ for possible turbulence within individual clouds ($\approx 1\rm~kpc$).

Most of the baryons in L* galaxies are unaccounted for and are predicted to lie in hot gaseous halos (T ~ 3E6 K) that may extend beyond R200. A hot gaseous halo will produce a thermal Sunyaev-Zeldovich signal that is proportional to the product of the gas mass and the mass-weighted temperature. To best detect this signal, we used a Needlet Independent Linear Combination all-sky Planck map that we produced from the most recent Planck data release, also incorporating WMAP data. The sample is 12 L* spiral galaxies with distances of 3-10 Mpc, which are spatially resolved so that contamination from the optical galaxy can be excluded. One galaxy, NGC 891, has a particularly strong SZ signal, and when excluding it, the stack of 11 galaxies is detected at about 4sigma (declining with radius) and is extended to at least 250 kpc (~R_200) at > 99% confidence. The gas mass within a spherical volume to a radius of 250 kpc is 9.8 +/- 2.8 E10 Msun, for Tavg = 3E6 K. This is about 30% of the cosmic baryon content of the average galaxy (3.1E11 Msun), and about equal to the mass of stars, disk gas, and warm halo gas. The remaining missing baryons (~ 1.4E11 Msun, 40-50% of the total baryon content) are likely to be hot and extend to the 400-500 kpc volume, if not beyond. The result is higher than predictions, but within the uncertainties.

Outflows from super-massive black holes (SMBHs) play an important role in the co-evolution of themselves, their host galaxies, and the larger scale environments. Such outflows are often characterized by emission and absorption lines in various bands and in a wide velocity range blueshifted from the systematic redshift of the host quasar. In this paper, we report a strong broad line region (BLR) outflow from the z~4.7 quasar BR 1202-0725 based on the high-resolution optical spectrum taken with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph installed on the 6.5m Magellan/Clay telescope, obtained from the `Probing the He II re-Ionization ERa via Absorbing C IV Historical Yield' (HIERACHY) project. This rest-frame ultraviolet (UV) spectrum is characterized by a few significantly blueshifted broad emission lines from high ions; the most significant one is the C IV line at a velocity of -6500 km/s relative to the H\alpha emission line, which is among the highest velocity BLR outflows in observed quasars at z > 4. The measured properties of UV emission lines from different ions, except for O I and Ly\alpha, also follow a clear trend that higher ions tend to be broader and outflow at higher average velocities. There are multiple C IV and Si IV absorbing components identified on the blue wings of the corresponding emission lines, which may be produced by either the outflow or the intervening absorbers.

Much of the baryons in galaxy groups are thought to have been driven out to large distances ($\gtrsim$$R_{500}$) by feedback, but there are few constraining observations of this extended gas. This work presents the resolved Sunyaev--Zel'dovich (SZ) profiles for a stacked sample of 10 nearby galaxy groups within the mass range log$_{10}(M_{500}[M_{\odot}]) = 13.6 -13.9$. We measured the SZ profiles using the publicly available $y$-map from the Planck Collaboration as well as our own $y$-maps constructed from more recent versions of $Planck$ data. The $y$-map extracted from the latest data release yielded a significant SZ detection out to 3 $R_{500}$. In addition, the stacked profile from these data were consistent with simulations that included AGN feedback. Our best-fit model using the latest $Planck$ data suggested a baryon fraction $\approx 5.6\%$ within $R_{500}$. This is significantly lower than the cosmic value of $\approx 16\%$, supporting the idea that baryons have been driven to large radii by AGN feedback. Lastly, we discovered a significant ($\sim 3\sigma$) "bump" feature near $\sim 2$ $R_{500}$ that is most likely the signature of internal accretion shocks.

We report a large-scale ($r\approx 20^\circ$) X-ray and Sunyaev-Zeldovich (SZ)-bright diffuse enhancement toward M31, which might be a Local Hot Bridge connecting the Milky Way (MW) with M31. We subtract the Galactic emission from the all-sky O VII and O VIII emission line measurement survey, and find that the emission of these two ions is enhanced within $r\approx20^\circ$ around M31. The mean emission enhancements are $5.6\pm 1.3$ L.U., and $2.8\pm0.6$ L.U. for O VII and O VIII, respectively ($>4\sigma$ for both ions). We also extract the SZ signal around M31, which suggests a surface brightness $y$ of $2-4\times10^{-7}$, an enhancement $>2.5\sigma$ (and a best fit of $5.9\sigma$). These three measurements trace the hot gas with a temperature $\log~T({\rm K})> 6$, showing similar plateau shapes (flat within $\approx15^\circ$, and zero beyond $\approx30^\circ$). A single-phase assumption leads to a temperature of $\log~T({\rm K})=6.34\pm0.03$, which is determined by the O VII/O VIII line ratio. Combining X-ray and SZ measurements, we suggest that this feature is unlikely to be the hot halo around M31 (too massive) or in the MW (too high pressure and X-ray bright). The plateau shape may be explained by a cylinder connecting the MW and M31 (the Local Hot Bridge). We constrain its length to be about 400 kpc, with a radius of 120 kpc, a density of $\approx 2\times10^{-4}-10^{-3} ~\rm cm^{-3}$, and a metallicity of $0.02-0.1~ Z_\odot$. The baryon mass is $\gtrsim10^{11}~M_\odot$, and the oxygen mass is about $\gtrsim10^8~M_\odot$, which contribute to the baryon or metal budget of the Local Group.

A light bridge is a prominent structure commonly observed within a sunspot. Its presence usually triggers a wealth of dynamics in a sunspot, and has a lasting impact on sunspot evolution. However, the fundamental structure of light bridges is still not well understood. In this study, we used the high-resolution spectropolarimetry data obtained by the Solar Optical Telescope onboard the Hinode satellite to analyze the magnetic and thermal structure of a light bridge at \AR. We also combined the high-cadence $1700\unit{\AA}$ channel data provided by the Atmospheric Imaging Assembly onboard the Solar Dynamic Observatory to study the dynamics on this bridge. We found that a pair of blue and red Doppler shift patches at two ends of this bridge, this pattern appears to be the convective motion directed by the horizontal component of the magnetic field aligned with the spine of this bridge. Paired upward and downward motions implies that the light bridge could have a two-legged or undulate magnetic field. Significant four minute oscillations in the emission intensity of the $1700\unit{\AA}$ bandpass were detected at two ends, which had overlap with the paired blue and red shift patches. The oscillatory signals at the light bridge and the penumbra were highly correlated with each other. Although they are separated in space at the photosphere, the periodicity seems to have a common origin from the underneath. Therefore, we infer that the light bridge and penumbra could share a common magnetic source and become fragmented at the photosphere by magneto-convection.

We develop a kinematical model for the Milky Way Si IV-bearing gas to determine its density distribution and kinematics. This model is constrained by a column density line shape sample extracted from the \it HST/COS archival data, which contains 186 AGN sight lines. We find that the Si IV ion density distribution is dominated by an extended disk along the $z$-direction (above or below the midplane), i.e., $n(z)=n_0\exp(-(z/z_0)^{0.82})$, where $z_0$ is the scale height of $6.3_{-1.5}^{+1.6}$ kpc (northern hemisphere) and $3.6_{-0.9}^{+1.0}$ kpc (southern hemisphere). The density distribution of the disk in the radial direction shows a sharp edge at $15-20$ kpc given by, $n(r_{\rm XY})=n_0\exp(-(r_{\rm XY}/r_0)^{3.36})$, where $r_0 \approx 12.5\pm0.6$ kpc. The difference of density distributions over $r_{\rm XY}$ and $z$ directions indicates that the warm gas traced by \ionSi4 is mainly associated with disk processes (e.g., feedback or cycling gas) rather than accretion. We estimate the mass of the warm gas (within 50 kpc) is $\log (M(50 {\rm kpc})/M_\odot)\approx8.1$ (assuming $Z\approx0.5Z_\odot$), and a $3\sigma$ upper limit of $\log (M(250 {\rm kpc})/M_\odot)\approx9.1$ (excluding the Magellanic system). Kinematically, the warm gas disk is nearly co-rotating with the stellar disk at $v_{\rm rot}=215\pm3\rm~km~s^{-1}$, which lags the midplane rotation by about $8\rm~km~s^{-1}~kpc^{-1}$ (within 5 kpc). Meanwhile, we note that the warm gas in the northern hemisphere has significant accretion with $v_{\rm acc}$ of $69\pm 7\rm ~km~s^{-1}$ at 10 kpc (an accretion rate of $-0.60_{-0.13}^{+0.11}~M_\odot\rm~yr^{-1}$), while in the southern hemisphere, there is no measurable accretion, with an upper limit of $0.4~M_\odot\rm~yr^{-1}$.

A solar jet on 2014 July 31, which was accompanied by a GOES C1.3 flare and a mini-filament eruption at the jet base, was studied by using observations taken by the New Vacuum Solar Telescope and the Solar Dynamic Observatory. Magnetic field extrapolation revealed that the jet was confined in a fan-spine magnetic system that hosts a null point at the height of about 9 Mm from the solar surface. An inner flare ribbon surrounded by an outer circular ribbon and a remote ribbon were observed to be associated with the eruption, in which the inner and remote ribbons respectively located at the footprints of the inner and outer spines, while the circular one manifested the footprint of the fan structure. It is interesting that the circular ribbon's west part showed an interesting round-trip slipping motion, while the inner ribbon and the circular ribbon's east part displayed a northward slipping motion. Our analysis results indicate that the slipping motions of the inner and the circular flare ribbons reflected the slipping magnetic reconnection process in the fan quasi-separatrix layer, while the remote ribbon was associated with the magnetic reconnection at the null point. In addition, the filament eruption was probably triggered by the magnetic cancellation around its south end, which further drove the slipping reconnection in the fan quasi-separatrix layer and the reconnection at the null point.

The ubiquitous solar jets or jet-like activities are generally regarded as an important source of energy and mass input to the upper solar atmosphere and the solar wind. However, questions about their triggering and driving mechanisms are not completely understood. By taking advantage of high temporal and high spatial resolution stereoscopic observations taken by the Solar Dynamic Observatory (SDO) and the Solar Terrestrial Relations Observatory (STEREO), we report an intriguing two-sided-loop jet occurred on 2013 June 02, which was dynamically associated with the eruption of a mini-filament below an overlying large filament, and two distinct reconnection processes are identified during the formation stage. The SDO observations reveals that the two-sided-loop jet showed a concave shape with a projection speed of about 80 - 136. From the other view angle, the STEREO ahead observations clearly showed that the trajectory of the two arms of the two-sided-loop were along the cavity magnetic field lines hosting the large filament. Contrary to the well-accepted theoretical model, the present observation sheds new light on our understanding of the formation mechanism of two-sided-loop jets. Moreover, the eruption of the two-sided-loop jet not only supplied mass to the overlying large filament, but also provided a rare opportunity to diagnose the magnetic structure of the overlying large filament via the method of three-dimensional reconstruction.

The warm ($\log~T\approx5$) gas is an important gaseous component in the galaxy baryonic cycle. We built a 2-dimension disk-CGM model to study the warm gas distribution of the Milky Way (MW) using the absorption line surveys of Si IV and O VI. In this model, the disk component of both ions has the same density profile ($n(r, z)=n_0\exp(-|z|/z_0)\exp(-r/r_0)$) with a scale height of $z_0=2.6\pm0.4\rm~kpc$ and a scale length of $r_0=6.1\pm1.2\rm~kpc$. For this disk component, we calculate the warm gas mass of $\log(M/M_\odot)=(7.6\pm0.2)-\log\frac{Z}{Z_\odot}$. The similar disk density profiles and total masses of Si IV and O VI-bearing gas set constraints on the ionization mechanisms. We suggest that the warm gas disk might be dominated by the Galactic fountain mechanism, which ejects and recycles gas to set both the scale height and the scale length of the warm gas disk. The CGM component in our model has a dependence on Galactic latitude with a higher column density along the direction perpendicular to the Galactic plane ($b=90^\circ$) than the column density along the radial direction ($b=0^\circ$). The column density difference between these two directions is $0.82\pm0.32\rm~dex$ at $6.3\sigma$ for both ions. This difference may be due to the enrichment of Galactic feedback to the entire CGM, or an additional interaction layer between the warm gas disk and the CGM; existing data cannot distinguish between these two scenarios. If this higher column density at $b=90^\circ$ is for the entire CGM, the total warm CGM mass is $\log(M/M_\odot)\approx(9.5-9.8)-\log\frac{Z}{0.5Z_\odot}$ within the MW virial radius of $250\rm~kpc$.

The metallicity of galactic gaseous halos provides insights into accretion and feedback of galaxies. The nearby edge-on galaxy NGC 891 has a multi-component gaseous halo and a background AGN (LQAC 035+042 003) projected 5 kpc above the disk near the minor axis. Against the UV continuum of this AGN, we detect lines from 13 ions associated with NGC 891 in new \it HST/COS spectra. Most of the absorption is from the warm ionized gas with $\log T=4.22\pm0.04$, $\log n_{\rm H}=-1.26\pm0.51$, and $\log N_{\rm H}=20.81\pm 0.20$. The metallicity of volatile elements (i.e., C, N, and S) is about half solar ($\rm[X/H] \approx -0.3\pm 0.3$), while Mg, Fe, and Ni show lower metallicities of $\rm[X/H]\approx-0.9$. The absorption system shows the depletion pattern seen for warm Galactic diffuse clouds, which is consistent with a mixture of ejected solar metallicity disk gases and the hot X-ray emitting halo ($Z=0.1-0.2Z_\odot$). The warm ionized gases are about 5 times more massive than the cold \ionH1 emitting gases around the galactic center, which might lead to accretion with a mean rate of $10^2~M_\odot\rm~yr^{-1}$ for a period of time. We also detect low metallicity ($\approx 0.1~Z_\odot$) gases toward LQAC 035+042 003 at $110\rm~km~s^{-1}$ (a high velocity cloud) and toward another sight line (3C 66A; 108 kpc projected from NGC 891) at $30\rm~km~s^{-1}$. This low metallicity material could be the cold mode accretion from IGM or the tidal disruption of satellites in the NGC 891 halo.

We present a formation process of a filament in active region NOAA 12574 during the period from 2016 August 11 to 12. Combining the observations of GONG H$\alpha$, Hida spectrum and SDO/AIA 304 A, the formation process of the filament is studied. It is found that cool material ($T\sim10^4$ K) is ejected by a series of jets originating from the western foot-point of the filament. Simultaneously, the magnetic flux emerged from the photosphere in the vicinity of the western foot-point of the filament. These observations suggest that cool material in the low atmosphere can be directly injected into the upper atmosphere and the jets are triggered by the magnetic reconnection between pre-existing magnetic fields and new emerging magnetic fields. Detailed study of a jet at 18:02 UT on August 11 with GST/BBSO TiO observations reveals that some dark threads appeared in the vicinity of the western foot-point after the jet and the projection velocity of plasma along the filament axis was about 162.6$\pm$5.4 km/s. Using with DST/Hida observations, we find that the injected plasma by a jet at 00:42 UT on August 12 was rotating. Therefore, we conclude that the jets not only supplied the material for the filament, but also injected the helicity into the filament simultaneously. Comparing the quantity of mass injection by the jets with the mass of the filament, we conclude that the estimated mass loading by the jets is sufficient to account for the mass in the filament.

The high ionization-state ions trace the hot gases in the universe, of which gaseous halos around galaxies are a major contributor. Following Qu & Bregman (2018), we calculate the gaseous halo contribution to the observed column density distributions for these ions by convolving the gaseous halo model with the observed stellar mass function. The predicted column density distribution reproduces the general shape of the observed column density distribution -- a broken power law with the break point at $\log N=14.0$ for \OVI. Our modeling suggests that the high column density systems originate from galaxies for which the virial temperature matches the temperature of the ionization fraction peak. Specifically, this mass range is $\log M_\star=8.5-10$ for \OVI, $\log M_\star=9.5-10.5$ for \NeVIII, and higher for higher ionization state ions (assuming $T_{\rm max}=2T_{\rm vir}$). A comparison with the observed \OVI column density distribution prefers a large radius model, where the maximum radius is twice the virial radius. This model may be in conflict with the more poorly defined \NeVIII column density distribution, suggesting further observations are warranted. The redshift evolution of the high column density systems is dominated by the change of the cosmic star formation rate, which decreases from $z=1.0$ to the local universe. Some differences at lower columns between our models and observations indicate that absorption by the intra-group (cluster) medium and intergalactic medium are also contributors to the total column density distributions.

We present an investigation of a coronal cavity observed above the western limb in the coronal red line Fe X 6374 Å using a telescope of Peking University and in the green line Fe XIV 5303 Å using a telescope of Yunnan Observatories, Chinese Academy of Sciences during the total solar eclipse on 2017 August 21. A series of magnetic field models are constructed based on the magnetograms taken by the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO) one week before the eclipse. The model field lines are then compared with coronal structures seen in images taken by the Atmospheric Imaging Assembly on board SDO and in our coronal red line images. The best-fit model consists of a flux rope with a twist angle of 3.1$\pi$, which is consistent with the most probable value of the total twist angle of interplanetary flux ropes observed at 1 AU. Linear polarization of the Fe XIII 10747 Å line calculated from this model shows a "lagomorphic" signature that is also observed by the Coronal Multichannel Polarimeter of the High Altitude Observatory. We also find a ring-shaped structure in the line-of-sight velocity of Fe XIII 10747 Å, which implies hot plasma flows along a helical magnetic field structure, in the cavity. These results suggest that the magnetic structure of the cavity is a highly twisted flux rope, which may erupt eventually. The temperature structure of the cavity has also been investigated using the intensity ratio of Fe XIII 10747 Å and Fe X 6374 Å.

The galactic gaseous halo is a gas reservoir for the interstellar medium in the galaxy disk, supplying materials for star formation. We developed a gaseous halo model connecting the galaxy disk and the gaseous halo by assuming the star formation rate on the disk is balanced by the radiative cooling rate of the gaseous halo, including stellar feedback. In addition to a single-temperature gaseous halo in collisional ionization equilibrium, we also consider the photoionization effect and a steady-state cooling model. Photoionization is important for modifying the ion distribution in low-mass galaxies and outskirts of massive galaxies due to the low densities. The multi-phase cooling model dominates the region within the cooling radius, where t_cooling=t_Hubble. Our model reproduces most of the observed high ionization state ions for a wide range of galaxy masses (i.e., OVI, OVII, NeVIII, MgX, and OVIII). We find that the OVI column density has a narrow range around ~10^14 cm^-2 for halo masses from M_star ~ 3 * 10^10 Msun to 6*10^12 Msun, which is consistent with some but not all observational studies. For galaxies with halo masses <~ 3 * 10^11 Msun, photoionization produces most of the OVI, while for more massive galaxies, the OVI is from the medium that is cooling from higher temperatures. Fitting the Galactic (Milky-Way) OVII and OVIII suggests a gaseous halo model where the metallicity is ~0.55 Zsun and the gaseous halo has a maximum temperature of ~ 1.9 * 10^6 K. This gaseous halo model does not close the census of baryonic material within R200.

We present observations of a small-scale Extreme-ultraviolet (EUV) wave that was associated with a mini-filament eruption and a GOES B1.9 micro-fare in the quiet Sun region. The initiation of the event was due to the photospheric magnetic emergence and cancellation in the eruption source region, which first caused the ejection of a small plasma ejecta, then the ejecta impacted on a nearby mini-filament and thereby led to the filament's eruption and the associated fare. During the filament eruption, an EUV wave at a speed of 182 317 km/s was formed ahead of an expanding coronal loop, which propagated faster than the expanding loop and showed obvious deceleration and refection during the propagation. In addition, the EUV wave further resulted in the transverse oscillation of a remote filament whose period and damping time are 15 and 60 minutes, respectively. Based on the observational results, we propose that the small-scale EUV wave should be a fast-mode magnetosonic wave that was driven by the the expanding coronal loop. Moreover, with the application of filament seismology, it is estimated that the radial magnetic field strength is about 7 Gauss. The observations also suggest that small-scale EUV waves associated with miniature solar eruptions share similar driving mechanism and observational characteristics with their large-scale counterparts.

We present the observations of a blowout jet that experienced two distinct ejection stages. The first stage started from the emergence of a small positive magnetic polarity, which cancelled with the nearby negative magnetic field and caused the rising of a mini-filament and its confining loops. This further resulted in a small jet due to the magnetic reconnection between the rising confining loops and the overlying open field. The second ejection stage was mainly due to the successive removal of the confining field by the reconnection. Thus that the filament erupted and the erupting cool filament material directly combined with the hot jet originated form the reconnection region and therefore formed the cool and hot components of the blowout jet. During the two ejection stages, cool H\alpha jets are also observed cospatial with their coronal counterparts, but their appearance times are earlier than the hot coronal jets a few minutes. Therefore, the hot coronal jets are possibly caused by the heating of the cool H\alpha jets, or the rising of the reconnection height from chromosphere to the corona. The scenario that magnetic reconnection occurred between the confining loops and the overlying open loops are supported by many observational facts, including the bright patches on the both sides of the mini-filament, hot plasma blobs along the jet body, and periodic metric radio type III bursts at the very beginnings of the two stages. The evolution and characteristics of these features manifest the detailed non-linear process in the magnetic reconnection.

The hot gas in galaxy halos may account for a significant fraction of missing baryons in galaxies, and some of these gases can be traced by high ionization absorption systems in QSO UV spectra. Using high S/N ratio $ HST$/COS spectra, we discovered a high ionization state system at $z=1.1912$ in the sightline toward \objectLBQS 1435-0134, and two-components absorption lines are matched for Mg X, Ne VIII, Ne VI, O VI, Ne V, O V, Ne IV, O IV, N IV, O III, and H I. Mg X, detected for the first time ($5.8 \sigma$), is a particularly direct tracer of hot galactic halos, as its peak ion fraction occurs near $10^{6.1}\rm~ K$, about the temperature of a virialized hot galaxy halo of mass $\sim 0.5 M^*$. With Mg X and NeVIII, a photoionization model cannot reproduce the observed column densities with path lengths of galaxy halos. For collisional ionization models, one or two temperature models do not produce acceptable fits, but a three temperature model or a power law model can produce the observed results. In the power law model, ${\rm d}N/{\rm d}T = 10^{4.4\pm 2.2-[Z/X]} T^{1.55\pm 0.41}$ with temperatures in the range $10^{4.39\pm0.13} {\rm~K} < T < 10^{6.04\pm0.05}~ {\rm K}$, the total hydrogen column density is $8.2 \times 10^{19} (0.3Z_{\odot}/Z) \rm~ cm^{-2}$ and the positive power law index indicates most of the mass is at the high temperature end. We suggest that this absorption system is a hot volume-filled galaxy halo rather than interaction layers between the hot halo and cool clouds. The temperature dependence of the column density is likely due to the local mixture of multiple phase gases.

On 2012 July 11, two solar filaments were observed in the northeast of the solar disk and their eruptions due to the interaction between them are studied by using the data from the Solar Dynamics Observatory (SDO), Solar TErrestrial RElations Observatory (STEREO) and Global Oscillation Network Group (GONG). The eastern filament (F1) first erupted toward the northeast. During the eruption of F1, some plasma from F1 fell down and was injected to the North-East part of another filament (F2), and some plasma of F1 fell down to the northern region close to F2 and caused the plasma to brighten. Meanwhile, the North-East part of F2 first started to be active and rise, but did not erupt finally. Then the South-West part of F2 erupted successfully. Therefore, the F2's eruption is a partial filament eruption. Two associated CMEs related to the eruptions were observed by STEREO/COR1. We find two possible reasons that lead to the instability and the eruption of F2. One main reason is that the magnetic loops overlying the two filaments were partially opened by the eruptive F1 and resulted in the instability of F2. The other is that the downflows from F1 might break the stability of F2.

Photospheric radius expansion (PRE) bursts have already been used to constrain the masses and radii of neutron stars. RXTE observed three PRE bursts in 4U 1746-37, all with low touchdown fluxes. We discuss here the possibility of low mass neutron star in 4U 1746-37 because the Eddington luminosity depends on stellar mass. With typical values of hydrogen mass fraction and color correction factor, a Monte-Carlo simulation was applied to constrain the mass and radius of neutron star in 4U 1746-37. 4U 1746-37 has a high inclination angle. Two geometric effects, the reflection of the far side accretion disc and the obscuration of the near side accretion disc have also been included in the mass and radius constraints of 4U 1746-37. If the reflection of the far side accretion disc is accounted, a low mass compact object (mass of $0.41\pm0.14~M_{\odot}$ and radius of $8.73\pm1.54~\rm km$ at 68% confidence) exists in 4U 1746-37. If another effect operated, 4U 1746-37 may contain an ultra low mass and small radius object ($M=0.21\pm0.06~M_{\odot},~R=6.26\pm0.99~\rm km$ at 68% confidence). Combined all possibilities, the mass of 4U 1746-37 is $0.41^{+0.70}_{-0.30}~M_\odot$ at 99.7% confidence. For such low mass NS, it could be reproduced by a self-bound compact star, i.e., quark star or quark-cluster star.

We analyzed temporal and spectral properties, focusing on the short bursts, for three anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs), including SGR 1806-20, 1E 1048-5937 and SGR 0501+4516. Using the data from XMM-Newton, we located the short bursts by Bayesian blocks algorithm. The short bursts' duration distributions for three sources were fitted by two lognormal functions. The spectra of shorter bursts ($< 0.2~\rm s$) and longer bursts ($\geq 0.2~\rm s$) can be well fitted in two blackbody components model or optically thin thermal bremsstrahlung model for SGR 0501+4516. We also found that there is a positive correlation between the burst luminosity and the persistent luminosity with a power law index $\gamma = 1.23 \pm 0.18 $. The energy ratio of this persistent emission to the time averaged short bursts is in the range of $10 - 10^3$, being comparable to the case in Type I X-ray burst.

Kink instability is a possible mechanism for solar filament eruption. However, the twist of a solar filament is very difficult to directly measure from observation. In this paper, we carried out the measurement of the twist of a solar filament by analyzing its leg rotation. An inverse S-shaped filament in active region NOAA 11485 was observed by the Atmospheric Imaging Assembly (AIA) of Solar Dynamics Observatory (SDO) on 2012 May 22. During its eruption, the leg of the filament exhibited a significant rotation motion. The 304 Å images were used to uncurl along the circles, whose centers are the axis of the filament's leg. The result shows that the leg of the filament rotated up to about 510 degrees (about 2.83$\pi$) around the axis of the filament within twenty-three minutes. The maximal rotation speed reached 100 degrees per minute (about 379.9 km/s at radius 18$^\prime$$^\prime$), which is the fastest rotation speed that has been reported. We also calculated the decay index along the polarity inversion line in this active region and found that the decline of the overlying field with height is not so fast enough to trigger the torus instability. According to the condition of kink instability, it is indicating that the kink instability is the trigger mechanism for the solar filament eruption.

With the data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO), we present a magnetic interaction between an isolated coronal hole (CH) and an emerging active region (AR). The AR emerged nearby the CH and interacted with it. Bright loops constantly formed between them, which led to a continuous retreat of the CH boundaries (CHBs). Meanwhile, two coronal dimmings respectively appeared at the negative polarity of the AR and the east boundary of the bright loops, and the AR was partly disturbed. Loop eruptions followed by a flare occurred in the AR. The interaction was also accompanied by many jets and an arc-shaped brightening that appeared to be observational signatures of magnetic reconnection at the CHBs. By comparing the observations with the derived coronal magnetic configuration, it is suggested that the interaction between the CH and the AR excellently fitted in with the model of interchange reconnection. It appears that our observations provide obvious evidences for interchange reconnection.

We find that a sunspot with positive polarity had an obvious counter-clockwise rotation and resulted in the formation and eruption of an inverse S-shaped filament in NOAA active region (AR) 08858 from 2000 February 9 to 10. The sunspot had two umbrae which rotated around each other by 195 degrees within about twenty-four hours. The average rotation rate was nearly 8 degrees per hour. The fastest rotation in the photosphere took place during 14:00UT to 22:01UT on February 9, with the rotation rate of nearly 16 degrees per hour. The fastest rotation in the chromosphere and the corona took place during 15:28UT to 19:00UT on February 9, with the rotation rate of nearly 20 degrees per hour. Interestingly, the rapid increase of the positive magnetic flux just occurred during the fastest rotation of the rotating sunspot, the bright loop-shaped structure and the filament. During the sunspot rotation, the inverse S-shaped filament gradually formed in the EUV filament channel. The filament experienced two eruptions. In the first eruption, the filament rose quickly and then the filament loops carrying the cool and the hot material were seen to spiral into the sunspot counterclockwise. About ten minutes later, the filament became active and finally erupted. The filament eruption was accompanied with a C-class flare and a halo coronal mass ejection (CME). These results provide evidence that sunspot rotation plays an important role in the formation and eruption of the sigmoidal active-region filament.

To better understand the dynamical process of active-region filament eruptions and associated flares and CMEs, we carried out a statistical study of 120 events observed by BBSO, TRACE, and t(SOHO/EIT) from 1998 to 2007 and combined filament observations with the NOAA's flare reports, MDI magnetograms, and LASCO data, to investigate the relationship between active-region filament eruptions and other solar activities. We found that 115 out of 120 filament eruptions are associated with flares. 56 out of 105 filament eruptions are found to be associated with CMEs except for 15 events without corresponding LASCO data. We note the limitation of coronagraphs duo to geometry or sensitivity, leading to many smaller CMEs that are Earth-directed or well out of the plane of sky not being detected by near-Earth spacecraft. Excluding those without corresponding LASCO data, the CME association rate of active-region filament eruptions clearly increases with X-ray flare class from about 32% for C-class flares to 100% for X-class flares. The eruptions of active-region filaments associated with Halo CMEs are often accompanied by large flares. About 92% events associated with X-class flare are associated with Halo CMEs. Such a result is due to that the Earth-directed CMEs detected as Halo CMEs are often the larger CMEs and many of the smaller ones are not detected because of the geometry and low intensity. The average speed of the associated CMEs of filament eruptions increases with X-ray flare size from 563.7 km/s for C-class flares to 1506.6 km/s for X-class flares. Moreover, the magnetic emergence and cancellation play an important role in triggering filament eruptions. These findings may be instructive to not only in respect to the modeling of active-region filament eruptions but also in predicting flares and CMEs.

To better understand long-term flare activity, we present a statistical study on soft X-ray flares from May 1976 to May 2008. It is found that the smoothed monthly peak fluxes of C-class, M-class, and X-class flares have a very noticeable time lag of 13, 8, and 8 months in cycle 21 respectively with respect to the smoothed monthly sunspot numbers. There is no time lag between the sunspot numbers and M-class flares in cycle 22. However, there is a one-month time lag for C-class flares and a one-month time lead for X-class flares with regard to sunspot numbers in cycle 22. For cycle 23, the smoothed monthly peak fluxes of C-class, M-class, and X-class flares have a very noticeable time lag of one month, 5 months, and 21 months respectively with respect to sunspot numbers. If we take the three types of flares together, the smoothed monthly peak fluxes of soft X-ray flares have a time lag of 9 months in cycle 21, no time lag in cycle 22 and a characteristic time lag of 5 months in cycle 23 with respect to the smoothed monthly sunspot numbers. Furthermore, the correlation coefficients of the smoothed monthly peak fluxes of M-class and X-class flares and the smoothed monthly sunspot numbers are higher in cycle 22 than those in cycles 21 and 23. The correlation coefficients between the three kinds of soft X-ray flares in cycle 22 are higher than those in cycles 21 and 23. These findings may be instructive in predicting C-class, M-class, and X-class flares regarding sunspot numbers in the next cycle and the physical processes of energy storage and dissipation in the corona.

Ways to give medium- and short-term predictions of solar flares are proposed according to the statistical analysis of events during solar cycle 23. On one hand, the time distribution of both C and M class flares shows two main periods of 13.2 and 26.4 months in this cycle by wavelet analysis. On the other hand, active regions of specific magnetic configurations and their evolutions give high productivity of C class flares but relatively low productivity of energetic (M and X class) flares. Furthermore, by considering the measurable kinetic features of active regions, i.e., the rotation of the sunspots, some active regions of specified types are observed to have high energetic flare productivity, above 66%. The periodicity of the activity revealed can be used for medium-term C and M class flare forecasting and the high productivity of active regions forms the basis for short-term prediction of individual energetic flares.