In this work we present a robust quantification of X-ray selected AGN in local ($z \leq 0.25$) dwarf galaxies ($M_\mathrm{*} \leq 3 \times 10^9 \mathrm{M_\odot}$). We define a parent sample of 4,331 dwarf galaxies found within the footprint of both the MPA-JHU galaxy catalogue (based on SDSS DR8) and 3XMM DR7, performed a careful review of the data to remove misidentifications and produced a sample of 61 dwarf galaxies that exhibit nuclear X-ray activity indicative of an AGN. We examine the optical emission line ratios of our X-ray selected sample and find that optical AGN diagnostics fail to identify 85% of the sources. We then calculated the growth rates of the black holes powering our AGN in terms of their specific accretion rates ($\propto L_\mathrm{X}/M_\mathrm{*}$, an approximate tracer of the Eddington ratio). Within our observed sample, we found a wide range of specific accretion rates. After correcting the observed sample for the varying sensitivity of 3XMM, we found further evidence for a wide range of X-ray luminosities and specific accretion rates, described by a power law. Using this corrected AGN sample we also define an AGN fraction describing their relative incidence within the parent sample. We found the AGN fraction increases with host galaxy mass (up to $\approx$ 6%) for galaxies with X-ray luminosities between $10^{39} \mathrm{erg/s}$ and $10^{42} \mathrm{erg/s}$, and by extrapolating the power law to higher luminosities, we found evidence to suggest the fraction of luminous AGN ($L_\mathrm{X} \geq 10^{42.4} \mathrm{erg/s}$) is constant out to $z \approx 0.7$.
In the manuscript, the composite galaxy SDSS J103911-000057 (=SDSS J1039) is reported as a better candidate of true Type-2 AGN without hidden BLRs. None broad but only narrow emission lines detected in SDSS J1039 can be well confirmed both by the F-test technique and by the expected broad emission lines with EW smaller than 13.5Å~ with 99\% confidence level. Meanwhile, a reliable AGN power law component is preferred with confidence level higher than 7sigma in SDSS J1039. Furthermore, the long-term variability of SDSS J1039 from CSS can be well described by the DRW process with intrinsic variab…
In the manuscript, we discuss properties of the SDSS J1042-0018 which is a broad line AGN but mis-classified as a HII galaxy in the BPT diagram (SDSS J1042-0018 called as a mis-classified broad line AGN). The emission lines around H$α$ and around H$β$ are well described by different model functions, considering broad Balmer lines to be described by Gaussian or Lorentz functions. Different model functions lead to different determined narrow emission line fluxes, but the different narrow emission line flux ratios lead the SDSS J1042-0018 as a HII galaxy in the BPT diagram. In order to explain th…
In this Letter, we report further evidence to support a tidal disruption event (TDE) in the known changing-look AGN SDSS J0159, through the unique variabilities of asymmetric broad H$α$: broader but redder in 2010 than in 2000. Accepted the broad H$α$ emission regions tightly related to accreting debris in a central TDE, the well-known relativistic accretion disk origination can be applied to well explain the asymmetric broad H$α$ variabilities in SDSS J0159. Moreover, the model determined broad H$α$ emission regions have the sizes not follow the empirical R-L relation valid in normal broad li…
SDSS 1257+5428 is a white dwarf in a close orbit with a companion that has been suggested to be a neutron star. If so, it hosts the closest known neutron star, and its existence implies a great abundance of similar systems and a rate of white-dwarf neutron-star mergers similar to that of the type Ia supernova rate. Here, we present high signal-to-noise spectra of SDSS 1257+5428, which confirm an independent finding that the system is in fact composed of two white dwarfs, one relatively cool and with low mass, and the other hotter and more massive. With this, the demographics and merger rate ar…
We quantify the frequency of companions of low redshift ($0.013 < z < 0.0252$), dwarf galaxies ($2 \times 10^8$ M$_\odot <$ M$_{*} < 5 \times 10^9$ M$_\odot$) that are isolated from more massive galaxies in SDSS and compare against cosmological expectations using mock observations of the Illustris simulation. Dwarf multiples are defined as 2 or more dwarfs that have angular separations > 55'', projected separations r$_p < 150$ kpc and relative line-of-sight velocities $ΔV_{\rm LOS} < 150$ km/s. While the mock catalogs predict a factor of 2 more isolated dwarfs than observed in SDSS, the mean n…
In the Letter, an interesting method is proposed to estimate size of narrow emission lines regions (NLRs) of a Type-2 AGN SDSS J083823.91+490241.1 (=SDSS J0838) at a redshift of 0.101, by comparing spectroscopic properties through the SDSS fiber (MJD=51873) (diameter of 3 arcseconds) and through the eBOSS fiber (MJD=55277) (diameter of 2 arcseconds). After subtractions of pPXF method determined host galaxy contributions, the narrow emission lines of SDSS J0838 in the SDSS spectrum and in the eBOSS spectrum can be well measured by Gaussian functions, leading more than 90\% of [O~{\sc iii}] emis…
We have collected all available spectra and photometric data from SDSS catalogue for bright AGNs complied from the first three months of the Fermi large area telescope all-sky survey. Based on the 106 high-confidence and 11 low-confidence association bright AGN list, the photometry data are collected from SDSS DR7 for 28 sources (12 BL Lacs and 16 FSRQs), two of which are low-confidence association bright AGNs. Among these 28 SDSS photometric sources, SDSS spectra are available for 20 sources (6 BL Lacs and 14 FSRQs). The black hole mass M_BH and the broad line region (BLR) luminosity were obt…
We report the discovery of a new detached, double white dwarf system with an orbital period of 39.8 min. We targeted SDSS J163030.58+423305.8 (hereafter J1630) as part of our radial velocity program to search for companions around low-mass white dwarfs using the 6.5m MMT. We detect peak-to-peak radial velocity variations of 576 km/s. The mass function and optical photometry rule out main-sequence companions. In addition, no milli-second pulsar companions are detected in radio observations. Thus the invisible companion is most likely another white dwarf. Unlike the other 39 min binary SDSS J010…
As the third installment in a series systematically searching dual active galactic nuclei (AGN) amongst merging galaxies, we present the results of 20 dual AGNs found by using the SDSS fiber spectra. To reduce the flux contamination from both the fiber aperture and seeing effects, the angular separation of two cores in our merging galaxy pairs sample is restricted at least larger than 3 arcsec. By careful analysis of the emission lines, 20 dual AGNs are identified from 61 merging galaxies with their two cores both observed by the SDSS spectroscopic surveys. 15 of them are identified for the fi…
During galaxy merger events, the supermassive black holes in the center of the galaxies may form a pair of active galactic nuclei (AGN) with kpc-scale or even pc-scale separation. Recently, optical observations revealed a promising dual AGN candidate at the center of the galaxy SDSS J101022.95$+$141300.9 (hereafter J1010$+$1413). The presence of two distinct [O III]-emitting point sources with a projected separation of $\sim 430$ pc indicates a dual AGN system. To search for AGN-dominated radio emission originating from the Hubble Space Telescope (HST) point sources, we carried out very long b…
We study how AGN activity changes across environments from galaxy pairs to clusters using $143\, 843$ galaxies with $z<0.2$ from the Sloan Digital Sky Survey (SDSS). Using a refined technique, we apply a continuous measure of AGN activity, characteristic of the ionization state of the narrow-line emitting gas. Changes in key emission-line ratios ([NII]$\lambda6548$/H$α$, [OIII]$\lambda5007$/H$β$) between different samples allow us to disentangle different environmental effects while removing contamination. We confirm that galaxy interactions enhance AGN activity. However, conditions in the cen…
We present Bayesian AGN Decomposition Analysis for SDSS Spectra (BADASS), an open source spectral analysis code designed for automatic detailed deconvolution of AGN and host galaxy spectra, implemented in Python, and designed for the next generation of large scale surveys. BADASS simultaneously fits all spectral components, including power-law continuum, stellar line-of-sight velocity distribution, FeII emission, as well as forbidden (narrow), permitted (broad), and outflow emission line features, all performed using Markov Chain Monte Carlo to obtain robust uncertainties and autocorrelation a…
We examine whether galaxy environments directly affect triggering nuclear activity in Sloan Digital Sky Survey (SDSS) local spiral galaxies using a volume-limited sample with the $r$-band absolute magnitude $M_{r} < -19.0$ and $0.02 < z < 0.055$ selected from the SDSS Data Release 7. To avoid incompleteness of the central velocity dispersion $σ$ of the volume-limited sample and to fix the black hole mass affecting AGN activity, we limit the sample to a narrow $σ$ range of $130$ km s$^{-1}<σ<200$ km s$^{-1}$. We define a variety of environments as a combination of neighbour interactions and loc…
This is the first paper in a dedicated series to study the properties of the optically selected BLR-less AGNs (Active Galactic Nuclei with no-hidden central broad emission line regions). We carried out a systematic search for the BLR-less AGNs through the Sloan Digital Sky Survey Legacy Survey (SDSS Stripe82 Database). Based on the spectral decomposition results for all the 136676 spectroscopic objects (galaxies and QSOs) with redshift less than 0.35 covered by the SDSS Stripe82 region, our spectroscopic sample for the BLR-less AGNs includes 22693 pure narrow line objects without broad emissio…
We report the discovery of a kiloparsec-scale triple supermassive black hole system at $z=0.256$: SDSS J1056+5516, discovered by our systematic search for binary quasars. The system contains three strong emission-line nuclei, which are offset by $<250~{\rm km~s^{-1}}$ and by 15-18 kpc in projected separation, suggesting that the nuclei belong to the same physical structure. The system includes a tidal arm feature spanning $\sim100$ kpc in projected distance at the systems' redshift, inhabiting an ongoing or recent galaxy merger. Based on our results, such a structure can only satisfy one of th…
We use the Wide-field Infrared Survey Explorer (WISE) and the Sloan Digital Sky Survey (SDSS) to confirm a connection between dust-obscured active galactic nuclei (AGNs) and galaxy merging. Using a new, volume-limited (z <= 0.08) catalog of visually-selected major mergers and galaxy-galaxy interactions from the SDSS, with stellar masses above 2x10^10 Msun, we find that major mergers (interactions) are 5-17 (3-5) times more likely to have red [3.4]-[4.6] colors associated with dust-obscured or `dusty' AGNs, compared to non-merging galaxies with similar masses. Using published fiber spectral dia…
We explore X-ray evidence for the presence of active galactic nuclei (AGNs) in the two most actively star-forming Green Pea galaxies (GPs), SDSS J0749+3337 and SDSS J0822+2241, which have star-formation rates (SFRs) of $123~M_\odot$ yr$^{-1}$ and $78~M_\odot$ yr$^{-1}$, respectively. The GPs have red mid-infrared (MIR) spectral energy distributions and higher 22 $μ$m luminosities than expected from a proxy of the SFR (H$α$ luminosity), consistent with hosting AGNs with 2-10 keV luminosities of $\sim10^{44}$ erg s$^{-1}$. We thus obtain and analyze the first hard ($>$ 10 keV) X-ray data observe…
Systematic research of low redshift optically selected SDSS Type-2 AGN but with apparent long-term optical variabilities from Catalina Sky Survey, I: data sample and basic results
Aims. We try to identify ultra-cool dwarfs from the seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7) with SDSS i-z and r-z colors. We also obtain proper motion data from SDSS, 2MASS, and UKIDSS and improve spectral typing from SDSS and 2MASS photometric colors. Methods. We selected ultra-cool dwarf candidates from the SDSS DR7 with new photometric selection criteria, which are based on a parameterization study of known L and T dwarfs. The objects are then cross-identified with the Two Micron All Sky Survey and the Fourth Data Release of the UKIRT Infrared Deep Sky Survey (UKIDSS…
We present colour transformations for the conversion of the W1 and W2 magnitudes of WISE photometric system to the Johnson-Cousins' BVRI, SDSS (gri), and 2MASS (JHK_s) photometric systems, for dwarfs. The W3 and W4 magnitudes were not considered due to their insufficient signal to noise ratio (S/N). The coordinates of 825 dwarfs along with their BVRI, gri, and JHK_s data, taken from Bilir et al. (2008) were matched with the coordinates of stars in the preliminary data release of WISE (Wright et al., 2010) and a homogeneous dwarf sample with high S/N ratio have been obtained using the following…
We investigate the relationship between host galaxies' stellar content and active galactic nuclei (AGN) for optically selected QSOs with z$<$0.5. There are total 82 QSOs we select from Sloan Digital Sky Survey (SDSS) . These 82 QSOs both have Wide-field Infrared Survey Explorer (WISE) data and measurable stellar content. With the help of the stellar population synthesis code STARLIGHT, we determine the luminosity fraction of AGN ,stellar population ages and star-formation history (SFH) of host galaxies. We find out there is a correlation between the star formation history and AGN property whic…
We identify 806 ultra-cool dwarfs from their SDSS riz photometry (of which 34 are newly discovered L dwarfs) and obtain proper motions through cross matching with UKIDSS and 2MASS. Proper motion and distance constraints show that nine of our ultra-cool dwarfs are members of widely separated binary systems; SDSS 0101 (K5V+M9.5V), SDSS 0207 (M1.5V+L3V), SDSS 0832 (K3III+L3.5V), SDSS 0858 (M4V+L0V), SDSS 0953 (M4V+M9.5V), SDSS 0956 (M2V+M9V), SDSS 1304 (M4.5V+L0V), SDSS 1631 (M5.5V+M8V), SDSS 1638 (M4V+L0V). One of these (SDSS 0832) is shown to be a companion to the bright K3 giant Eta Cancri. Su…
We announce the discovery of the Aquarius~2 dwarf galaxy, a new distant satellite of the Milky Way, detected on the fringes of the VST ATLAS and the SDSS surveys. The object was originally identified as an overdensity of Red Giant Branch stars, but chosen for subsequent follow-up based on the presence of a strong Blue Horizontal Branch, which was also used to measure its distance of $\sim 110$ kpc. Using deeper imaging from the IMACS camera on the 6.5m Baade and spectroscopy with DEIMOS on Keck, we measured the satellite's half-light radius $5.1\pm 0.8$ arcmin, or $\sim 160$ pc at this distanc…
Environment is one of the key external drivers of the galaxies, while active galactic nucleus (AGN) is one of the key internal drivers. Both of them play fundamental roles in regulating the formation and evolution of galaxies. We explore the interrelationship between environment and AGN in SDSS. At a given stellar mass, the specific star formation rate distribution of the AGN host galaxies remains unchanged with over-density, with the peak of the distribution around the Green Valley. We show that, at a given stellar mass, the AGN fraction that has been commonly used in previous studies (define…
We report on the result of an ongoing campaign to determine chemical abundances in extremely metal poor (EMP) turn-off (TO) stars selected from the Sloan Digital Sky Survey (SDSS) low resolution spectra. This contribution focuses principally on the largest part of the sample (18 stars out of 29), observed with UVES@VLT and analyzed by means of the automatic abundance analysis code MyGIsFOS to derive atmosphere parameters and detailed compositions. The most significant findings include i) the detection of a C-rich, strongly Mg-enhanced star ([Mg/Fe]=1.45); ii) a group of Mn-rich stars ([Mn/Fe]>…
In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) (i) on the mid-infrared (MIR) luminosity and (ii) on the redshift. We constructed 12- and 22-micron luminosity functions (LFs) at 0.006 < z < 0.3 using the Wide-field Infrared Survey Explorer} (WISE) data. Combining the WISE catalog with the Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 micron and 25,721 galaxies at 22 micron for spectroscopic classification. We then identified 16,355 AGNs at 12 micron and 4,683 AGNs at 22 micron by their optical emi…
We explore the significance of bars in triggering central star formation (SF) and AGN activity for spiral galaxy evolution using a volume-limited sample with $0.020<z<0.055$, $M_{\rm r}<-19.5$, and $σ>70\rm km s^{-1}$ selected from SDSS DR7. On a central SF rate-$σ$ plane, we measure the fraction of galaxies with strong bars in our sample and also the AGN fractions for barred and non-barred galaxies, respectively. The comparison between the bar and AGN fractions reveals a causal connection between the two phenomena of SF quenching and AGN activity. A massive BH and abundant gas fuels are suffi…
The levels of heavy elements in stars are the product of enhancement by previous stellar generations, and the distribution of this metallicity among the population contains clues to the process by which a galaxy formed. Most famously, the "G-dwarf problem" highlighted the small number of low-metallicity G-dwarf stars in the Milky Way, which is inconsistent with the simplest picture of a galaxy formed from a "closed box" of gas. It can be resolved by treating the Galaxy as an open system that accretes gas throughout its life. This observation has classically only been made in the Milky Way, but…
Aims: WISE provides an infrared all-sky survey which aims at completing our knowledge on the possibly dramatically increasing number of brown dwarfs with lower temperatures. We search for the nearest representatives of the coolest brown dwarfs, which will be very interesting for detailed follow-up observations, once they haven been discovered. Methods: We have used the preliminary data release from WISE, selected bright candidates with colours typical of late-T dwarfs, tried to match them with faint 2MASS and SDSS objects, to determine their proper motions, and to follow-up them spectroscopica…
We present results from a multi-wavelength analysis searching for multiple AGN systems in nearby (z<0.077) triple galaxy mergers. Combining archival Chandra, SDSS, WISE, and VLA observations, we quantify the rate of nearby triple AGN, as well as investigate possible connections between SMBH accretion and merger environments. Analyzing the multi-wavelength observations of 7 triple galaxy mergers, we find that 1 triple merger has a single AGN (NGC 3341); we discover, for the first time, 4 likely dual AGN (SDSS J1027+1749, SDSS J1631+2352, SDSS J1708+2153, and SDSS J2356-1016); we confirm one tri…
This work presents the catalogue of optical spectral properties for all X-ray selected SPIDERS active galactic nuclei (AGN) up to SDSS DR14. SPIDERS (SPectroscopic IDentification of eROSITA Sources) is an SDSS-IV programme that is currently conducting optical spectroscopy of the counterparts to the X-ray selected sources detected in the ROSAT all-sky survey and the XMM-Newton slew survey in the footprint of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS). The SPIDERS DR14 sample is the largest sample of X-ray selected AGN with optical spectroscopic follow-up to date. The catalogue…
Using the LOWZ and CMASS samples of the ninth data release (DR9) from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), I investigate properties of star forming galaxies and AGNs. The CMASS sample seriously suffers from the radial selection effect, even within the redshift 0.44<z<0.6, which will lead to statistical conclusions in the CMASS sample being less likely robust. In the LOWZ sample, the fraction of star-forming galaxies is nearly constant from the lowest density regime to the densest regime; the AGN fraction is also insensitive to the local environment. In addition, I note …
We present the first results from BAYMAX (Bayesian AnalYsis of Multiple AGN in X-rays), a tool that uses a Bayesian framework to quantitatively evaluate whether a given Chandra observation is more likely a single or dual point source. Although the most robust method of determining the presence of dual AGNs is to use X-ray observations, only sources that are widely separated relative to the instrument PSF are easy to identify. It becomes increasingly difficult to distinguish dual AGNs from single AGNs when the separation is on the order of Chandra's angular resolution (<1''). Using likelihood m…
We present a new catalog of spectroscopically-confirmed white dwarf stars from the Sloan Digital Sky Survey Data Release 7 spectroscopic catalog. We find 20,407 white dwarf spectra, representing 19,712 stars, and provide atmospheric model fits to 14,120 DA and 1011 DB white dwarf spectra from 12,843 and 923 stars, respectively. These numbers represent a more than factor of two increase in the total number of white dwarf stars from the previous SDSS white dwarf catalog based on DR4 data. Our distribution of subtypes varies from previous catalogs due to our more conservative, manual classificati…
We selected brown dwarf candidates from the seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7) with new photometric selectioncriteria based on a parameteriaztion of well-known L and T dwarfs. Then we confirmed their status with SDSS spectra. The candidates without SDSS spectra are cross matched in the Two Micron All Sky Survey (2MASS) and the Fourth Data Release of the UKIRT Infrared Deep Sky Survey (UKIDSS DR4). With the help of colors based on SDSS, 2MASS and UKIDSS, we are able to estimate spectral types of our candidates. We obtain reliable proper motions using positional and …
We report the discovery of two field brown dwarfs, ULAS J0128-0041 and ULAS J0321+0051, and the rediscovery of ULAS J0226+0051 (IfA 0230-Z1), in the Sloan Digital Sky Survey (SDSS) southern equatorial stripe. They are found in the course of our follow-up observation program of 1 um excess sources in the United Kingdom Infrared Telescope Infrared Deep Sky Survey. The Gemini Multi-Object Spectrographs spectra at red optical wavelengths (6500-10500 A) are presented, which reveal that they are early-T dwarfs. The classification is also supported by their optical to near-infrared colors. It is note…
The white dwarf SDSS J124043.01+671034.68 (SDSS J1240+6710) was previously found to have an oxygen-dominated atmosphere with significant traces of neon, magnesium, and silicon. A possible origin via a violent late thermal pulse or binary interactions have been suggested to explain this very unusual photospheric composition. We report the additional detection of carbon, sodium, and aluminium in far-ultraviolet and optical follow-up spectroscopy. No iron-group elements are detected, with tight upper limits on iron, cobalt and nickel, suggesting that the star underwent partial oxygen burning, but…
We derive the local dark matter density by applying the integrated Jeans equation method from Silverwood et al. (2016) to SDSS-SEGUE G-dwarf data processed and presented by Büdenbender et al. (2015). We use the MultiNest Bayesian nested sampling software to fit a model for the baryon distribution, dark matter and tracer stars, including a model for the 'tilt term' that couples the vertical and radial motions, to the data. The $α$-young population from Büdenbender et al. (2015) yields the most reliable result of $ρ_{\rm DM} = 0.46^{+0.07}_{-0.09}\, {{\rm GeV\, cm}^{-3}} = 0.012^{+0.001}_{-0.002…
We present follow-up spectroscopy of 711 white dwarfs within 100 pc, and present a detailed model atmosphere analysis of the 100 pc white dwarf sample in the SDSS footprint. Our spectroscopic follow-up is complete for 83% of the white dwarfs hotter than 6000 K, where the atmospheric composition can be constrained reliably. We identify 1508 DA white dwarfs with pure hydrogen atmospheres. The DA mass distribution has an extremely narrow peak at $0.59~M_{\odot}$, and reveals a shoulder from relatively massive white dwarfs with $M=0.7$-$0.9~M_{\odot}$. Comparing this distribution with binary popul…
We report the discovery of the ninth pre-polar, consisting of a late-type ZAMS secondary and a magnetic white dwarf. The white dwarf accretes at extreme low rate, dot{M} ~ 10**-14 Msun/yr, from the wind of the companion donor star. The source was found in our systematic search for WD/MS binaries within SDSS/SEGUE. Based on seven Sloan-spectra we estimate a binary period of ~200, 230, or 270 min. The UV to IR spectral energy distribution was decomposed into a dM3-dM4 ZAMS secondary and a cool white dwarf, ~9000 K, which consistently imply a distance between 360 and 420 pc. The optical spectrum …
In a sample of 476931 NELGs obtained from the SDSS DR5 data we find that in 22% of the galaxies the emission line [OIII]$λ$5007, H$β$, or both, are missing. The nature of the activity in these galaxies was determined using a diagnostic diagram comparing the equivalent width of [NII]$λ$6584 with the ratio [NII]$λ$6584/H$α$. The majority of these galaxies are AGN. The H$α$ emission lines have a mean FWHM of 400 km s$^{-1}$ and mean luminosity of 5.6$\times$10$^{39}$ erg s$^{-1}$, which justify their classification as LLAGN. A study of their star formation histories using STARLIGHT reveals no tra…
We detect and study the properties of faint radio AGN in Luminous Red Galaxies (LRGs). The LRG sample comprises 760,000 objects from a catalog of LRG photometric redshifts constructed from the Sloan Digital Sky Survey (SDSS) imaging data, and 65,000 LRGs from the SDSS spectroscopic sample. These galaxies have typical 1.4 GHz flux densities in the 10s-100s of microJy, with the contribution from a low-luminosity AGN dominating any contribution from star formation. To probe the radio properties of such faint objects, we employ a stacking technique whereby FIRST survey image cutouts at each optica…
We study the effects of radio jets on galaxies in their vicinity (satellites) and the role of satellites in triggering radio-loud active galactic nuclei (AGNs). The study compares the aggregate properties of satellites of a sample of 7,220 radio AGNs at z < 0.3 (identified by Best & Heckman 2012 from the SDSS and NVSS+FIRST surveys) to the satellites of a control sample of radio-quiet galaxies, which are matched in redshift, color, luminosity, and axis ratio, as well as by environment type: field galaxies, cluster members and brightest cluster galaxies (BCGs). Remarkably, we find that radio AG…
We report the discovery of the first pulsating extremely low mass (ELM) white dwarf (WD), SDSS J184037.78+642312.3 (hereafter J1840). This DA (hydrogen-atmosphere) WD is by far the coolest and the lowest-mass pulsating WD, with Teff = 9100 \pm 170 K and log g = 6.22 \pm 0.06, which corresponds to a mass ~ 0.17 Msun. This low-mass pulsating WD greatly extends the DAV (or ZZ Ceti) instability strip, effectively bridging the log g gap between WDs and main sequence stars. We detect high-amplitude variability in J1840 on timescales exceeding 4000 s, with a non-sinusoidal pulse shape. Our observatio…
We present results from our X-ray analysis of the first systematic search for triple AGN in nearby (z<0.077) triple galaxy mergers. We analyze archival Chandra observations of 7 triple galaxy mergers with BAYMAX (Bayesian Analysis of Multiple AGN in X-rays), fitting each observation with single, dual, and triple X-ray point source models. In doing so, we conclude that 1 triple merger has one X-ray point source (SDSS J0858+1822, although it's unlikely to be an AGN); 5 triple mergers are likely composed of two X-ray point sources (NGC 3341, SDSS J1027+1749, SDSS J1631+2352, SDSS J1708+2153, and …
