Tidal forces close to massive black holes can violently disrupt stars that make a close approach. These extreme events are discovered via bright X-ray and optical/ultraviolet flares in galactic centres. Prior studies based on modelling decaying flux trends have been able to estimate broad properties, such as the mass accretion rate. Here we report the detection of flows of hot, ionized gas in high-resolution X-ray spectra of a nearby tidal disruption event, ASASSN-14li in the galaxy PGC 043234. Variability within the absorption-dominated spectra indicates that the gas is relatively close to the black hole. Narrow linewidths indicate that the gas does not stretch over a large range of radii, giving a low volume filling factor. Modest outflow speeds of a few hundred kilometres per second are observed; these are below the escape speed from the radius set by variability. The gas flow is consistent with a rotating wind from the inner, super-Eddington region of a nascent accretion disk, or with a filament of disrupted stellar gas near to the apocentre of an elliptical orbit. Flows of this sort are predicted by fundamental analytical theory and more recent numerical simulations.

We present the Chandra Multiwavelength Project (ChaMP) X-ray point source catalog with $6800 X-ray sources detected in 149 Chandra observations covering $10 deg 2 . The full ChaMP catalog sample is 7 times larger than the initial published ChaMP catalog. The exposure time of the fields in our sample ranges from 0.9 to 124 ks, corresponding to a deepest X-ray flux limit of f 0:5Y8:0 ¼ 9 ; 10 À16 ergs cm À2 s À1. The ChaMP X-ray data have been uniformly reduced and analyzed with ChaMP-specific pipelines and then carefully validated by visual inspection. The ChaMP catalog includes X-ray photometric data in eight different energy bands as well as X-ray spectral hardness ratios and colors. To best utilize the ChaMP catalog, we also present the source reliability, detection probability, and positional uncertainty. To quantitatively assess those parameters, we performed extensive simulations. In particular, we present a set of empirical equations: the flux limit as a function of effective exposure time and the positional uncertainty as a function of source counts and off-axis angle. The false source detection rate is $1% of all detected ChaMP sources, while the detection probability is better than $95% for sources with counts k30 and off-axis angle <5 0 . The typical positional offset between ChaMP X-ray source and their SDSS optical counterparts is 0:7 00 AE 0:4 00 , derived from $900 matched sources.

Theory suggests that a star making a close passage by a supermassive black hole at the center of a galaxy can under most circumstances be expected to emit a giant flare of radiation as it is disrupted and a portion of the resulting stream of shock-heated stellar debris falls back onto the black hole itself. We examine the first results of an ongoing archival survey of galaxy clusters using Chandra and XMM-Newton-selected data, and report a likely tidal disruption flare from SDSS J131122.15-012345.6 in Abell 1689. The flare is observed to vary by a factor of 30 over at least 2 years, to have maximum L X (0.3 − 3.0 keV) 5 × 10 42 erg s −1 and to emit as a blackbody with kT ∼ 0.12 keV. From the galaxy population as determined by existing studies of the cluster, we estimate a tidal disruption rate of 1.2 × 10 −4 galaxy −1 year −1 if we assume a contribution to the observable rate from galaxies whose range of luminosities corresponds to a central black hole mass (M • ) between 10 6 and 10 8 M ⊙ .We reprocessed the ACIS event files using CIAO to remove pixel randomization. According to standard CIAO data processing threads, we also applied TGAIN and CTI

We present narrow-and medium-band HST imaging, with additional supporting ground-based imaging, spectrophotometry, and Fabry-Perot interferometric data, for eight galaxies identified as hosting fading AGN. These are selected to have AGN-ionized gas projected > 10 kpc from the nucleus, and energy budgets with a significant shortfall of ionizing radiation between the requirement to ionize the distant gas and the AGN as observed directly, indicating fading of the AGN on ≈ 50, 000-year timescales. This paper focuses on the host-galaxy properties and origin of the gas. In every galaxy, we identify evidence of ongoing or past interactions, including tidal tails, shells, and warped or chaotic dust structures; a similarly-selected sample of obscured AGN with extended ionized clouds shares this high incidence of disturbed morphologies. Several systems show multiple dust lanes in different orientations, broadly fit by differentially precessing disks of accreted material viewed ∼ 1.5 Gyr after its initial arrival. The host systems are of early Hubble type; most show nearly pure de Vaucouleurs surface-brightness profiles and Sersic indices appropriate for classical bulges, with one S0 and one SB0 galaxy. The gas has systematically lower metallicity than the nuclei; three systems have abundances uniformly well below solar, consistent with an origin in tidally disrupted low-luminosity galaxies, while some systems have more nearly solar abundances (accompanied by such signatures as multiple Doppler components), which may suggest redistribution of gas by outfows within the host galaxies themselves. These aspects are consistent with a tidal origin for the extended gas in most systems, although the ionized gas and stellar tidal features do not always match closely. Unlike extended emission regions around many radio-loud AGN, these clouds are kinematically dominated by rotation, in some cases in warped disks. Outflows can play important kinematic roles only in localized regions near some of the AGN. We find only a few sets of young star clusters potentially triggered by 1 Visiting astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.2 SARA Observatory 2 AGN outflows. In UGC 7342 and UGC 11185, multiple luminous star clusters are seen just within the projected ionization cones, potentially marking star formation triggered by outflows. As in the discovery example Hanny's Voorwerp/IC 2497, there are regions in these clouds where lack of a strong correlation between Hα surface brightness and ionization parameter indicates that there is unresolved fine structure in the clouds. Together with thin coherent filaments spanning several kpc, persistence of these structures over their orbital lifetimes may require a role for magnetic confinement. Overall, we find that the sample of fading AGN occurs in interacting and merging systems, that the very extended...

We present a Hubble Space Telescope Space Telescope Imaging Spectrograph spectrum of ASASSN-14li, the first rest-frame ultraviolet (UV) spectrum of a tidal disruption flare (TDF). The underlying continuum is well fit by a blackbody with T 3.5 10=´K, an order of magnitude smaller than the temperature inferred from X-ray spectra (and significantly more precise than previous efforts based on optical and near-UV photometry). Superimposed on this blue continuum, we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad (∼2000-8000 km s −1 ) emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by Δv=−(250-400) km s −1 . Due both to this velocity offset and the lack of common low-ionization features (Mg II, Fe II), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N III], N IV], and He II are quite prominent, while the common quasar emission lines of C III] and Mg II are weak or entirely absent. Detailed modeling of this spectrum will help elucidate fundamental questions regarding the nature of the emission processes at work in TDFs, while future UV spectroscopy of ASASSN-14li would help to confirm (or refute) the previously proposed connection between TDFs and "N-rich" quasars.