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Active galactic nuclei (AGNs) show a correlation between the size of thebroad line region (BLR) and the monochromatic continuum luminosity at 5100 \AA,allowing black hole mass estimation based on single-epoch spectra. However, thevalidity of the correlation is yet to be clearly tested for high-luminosityAGNs. We present the first reverberation-mapping results of the Seoul NationalUniversity AGN monitoring program (SAMP), which is designed to focus onluminous AGNs for probing the high end of the size-luminosity relation. Wereport time lag measurements of two AGNs, namely, 2MASS J10261389+5237510 andSDSS J161911.24+501109.2, using the light curves obtained over a $\sim$1000 dayperiod with an average cadence of $\sim$10 and $\sim$20 days, respectively forphotometry and spectroscopy monitoring. Based on a cross-correlation analysisand H$\beta$ line width measurements, we determine the H$\beta$ lag as$41.8^{+4.9}_{-6.0}$ and $52.6^{+17.6}_{-14.7}$ days in the observed-frame, andblack hole mass as $3.65^{+0.49}_{-0.57} \times 10^7 M_{\odot}$ and$23.02^{+7.81}_{-6.56} \times 10^7 M_{\odot}$, respectively for 2MASS J1026 andSDSS J1619.

We conduct one of the largest systematic investigations of bright X-ray binaries (XRBs) in both young star clusters and ancient globular clusters (GCs) using a sample of six nearby star-forming galaxies. Combining complete CXO X-ray source catalogs with optical Physics at High Angular Resolution in Nearby Galaxies-Hubble Space Telescope cluster catalogs, we identify a population of 33 XRBs within or near their parent clusters. We find that GCs that host XRBs in spiral galaxies appear to be brighter, more compact, denser, and more massive than the general GC population. However, these XRB hosts do not appear to be preferentially redder or more metal-rich, pointing to a possible absence of the metallicity-boosted formation of low-mass X-ray binaries (LMXBs) that is observed in the GCs of older galaxies. We also find that a smaller fraction of LMXBs is found in spiral GC systems when compared with those in early-type galaxies: between 8% and 50%, or an average of 20% across galaxies in our sample. Although there is a non-negligible probability of a chance superposition between an XRB and an unrelated young cluster, we find that among clusters younger than 10 Myr, which most likely host high-mass XRBs, the fraction of clusters associated with an XRB increases at higher cluster masses and densities. The X-ray luminosity of XRBs appears to increase with the mass of the cluster host for clusters younger than ∼400 Myr, while the inverse relation is found for XRBs in GCs. [ABSTRACT FROM AUTHOR]

We present the results of a high-cadence spectroscopic and imaging monitoring campaign of the active galactic nucleus (AGN) of NGC 4395. High signal-to-noise-ratio spectra were obtained at the Gemini-N 8 m telescope using the GMOS integral field spectrograph (IFS) on 2019 March 7 and at the Keck I 10 m telescope using the Low-Resolution Imaging Spectrometer with slit masks on 2019 March 3 and April 2. Photometric data were obtained with a number of 1 m-class telescopes during the same nights. The narrow-line region (NLR) is spatially resolved; therefore, its variable contributions to the slit spectra make the standard procedure of relative flux calibration impractical. We demonstrate that spatially resolved data from the IFS can be effectively used to correct the slit-mask spectral light curves. While we obtained no reliable lag owing to the lack of a strong variability pattern in the light curves, we constrain the broad-line time lag to be less than 3 hr, consistent with the photometric lag of ∼80 minutes reported by Woo et al. By exploiting the high-quality spectra, we measure the second moment of the broad component of the H α emission line to be 586 ± 19 km sâˆ'1, superseding the lower value reported by Woo et al. Combining the revised line dispersion and the photometric time lag, we update the black hole mass to (1.7 ± 0.3) Ă— 104 M ⊙. [ABSTRACT FROM AUTHOR]

Building on recent work by Chandar et al., we construct X-ray luminosity functions (XLFs) for different classes of X-ray binary (XRB) donors in the nearby star-forming galaxy M83 through a novel methodology. Rather than classifying low- versus high-mass XRBs based on the scaling of the number of X-ray sources with stellar mass and star formation rate, respectively, we utilize multiband Hubble Space Telescope imaging data to classify each Chandra-detected compact X-ray source as a low-mass (i.e., donor mass ≲3 M⊙), high-mass (donor mass ≳8M⊙), or intermediate-mass XRB based on either the location of its candidate counterpart on optical color–magnitude diagrams or the age of its host star cluster. In addition to the standard (single and/or truncated) power-law functional shape, we approximate the resulting XLFs with a Schechter function. We identify a marginally significant (at the 1σ-to-2σ level) exponential downturn for the high-mass XRB XLF, at (in log CGS units). In contrast, the low- and intermediate-mass XRB XLFs, as well as the total XLF of M83, are formally consistent with sampling statistics from a single power law. Our method suggests a non-negligible contribution from low- and possibly intermediate-mass XRBs to the total XRB XLF of M83, i.e., between 20% and 50%, in broad agreement with X-ray-based XLFs. More generally, we caution against considerable contamination from X-ray emitting supernova remnants to the published, X-ray-based XLFs of M83, and possibly all actively star-forming galaxies. [ABSTRACT FROM AUTHOR]

About half of nearby galaxies have a central surface brightness ≥1 mag below that of the sky. The overall properties of these low-surface-brightness galaxies (LSBGs) remain understudied, and in particular we know very little about their massive black hole population. This gap must be closed to determine the frequency of massive black holes at z = 0 as well as to understand their role in regulating galaxy evolution. Here we investigate the incidence and intensity of nuclear, accretion-powered X-ray emission in a sample of 32 nearby LSBGs with the Chandra X-ray Observatory. A nuclear X-ray source is detected in four galaxies (12.5%). Based on an X-ray binary contamination assessment technique developed for normal galaxies, we conclude that the detected X-ray nuclei indicate low-level accretion from massive black holes. The active fraction is consistent with that expected from the stellar mass distribution of the LSBGs, but not their total baryonic mass, when using a scaling relation from an unbiased X-ray survey of normal galaxies. This suggests that their black holes co-evolved with their stellar population. In addition, the apparent agreement nearly doubles the number of galaxies available within ∼100 Mpc for which a measurement of nuclear activity can efficiently constrain the frequency of black holes as a function of stellar mass. We conclude by discussing the feasibility of measuring this occupation fraction to a few percent precision below ≲1010M⊙ with high-resolution, wide-field X-ray missions currently under consideration. [ABSTRACT FROM AUTHOR]

Ultraluminous X-ray sources (ULXs) are some of the brightest phenomena found outside of a galaxy's nucleus, and their explanation typically invokes accretion of material onto a black hole. Here, we perform the largest population study to date of ULXs in early-type galaxies, focusing on whether a galaxy's large-scale environment can affect its ULX content. Using the AMUSE survey, which includes homogeneous X-ray coverage of 100 elliptical galaxies in the Virgo cluster and a similar number of elliptical galaxies in the field (spanning stellar masses of 108-1012M☼), we identify 37.9 ± 10.1 ULXs in Virgo and 28.1 ± 8.7 ULXs in the field. Across both samples, we constrain the number of ULXs per unit stellar mass, i.e., the ULX specific frequency, to be 0.062 ± 0.013 ULXs per 1010M☼ (or about 1 ULX per 1.6 × 1011M☼ of galaxy stellar mass). We find that the number of ULXs, the specific frequency of ULXs, and the average ULX spectral properties are all similar in both cluster and field environments. Contrary to late-type galaxies, we do not see any trend between specific ULX frequency and host galaxy stellar mass, and we show that dwarf ellipticals host fewer ULXs than later-type dwarf galaxies at a statistically meaningful level. Our results are consistent with ULXs in early-type galaxies probing the luminous tail of the low-mass X-ray binary population, and are briefly discussed in context of the influence of gravitational interactions on the long-term evolution of a galaxy's (older) stellar population. [ABSTRACT FROM AUTHOR]

We present new Chandra х-ray observations of the transient black hole х-ray binary MAхI J1659-152 in quiescence. These observations were made more than one year after the end of the source's 2010-2011 outburst. We detect the source at a 0.5-10 keV flux of 2.8(8) × 10-15 erg s-1 cm-2, which corresponds to a luminosity of ∼1.2 × 1031 (d/6 kpc)2 erg s-1. This level, while being the lowest at which the source has been detected, is within factors of ∼2 of the levels seen at the end of the initial decay of the outburst and soon after a major reflare of the source. The quiescent luminosity of MAхI J1659-152, which is the shortest-orbital-period black hole х-ray binary (∼2.4 hr), is lower than that of neutron-star х-ray binaries with similar periods. However, it is higher than the quiescent luminosities found for black hole х-ray binaries with orbital periods ∼2-4 times longer. This could imply that a minimum quiescent luminosity may exist for black hole х-ray binaries, around orbital periods of ∼5-10 hr, as predicted by binary-evolution models for the mass transfer rate. Compared to the hard state, we see a clear softening of the power-law spectrum in quiescence, from an index of 1.55(4) to an index of 2.5(4). We constrain the luminosity range in which this softening starts to (0.18-6.2)×10-5 (d/6 kpc)2 (M/8M_) LEdd, which is consistent with the ranges inferred for other sources. [ABSTRACT FROM AUTHOR]

Most transient black hole X-ray binaries (BHXBs) spend the bulk of their time in a quiescent state, where they accrete matter from their companion star at highly sub-Eddington luminosities (we define quiescence here as a normalized Eddington ratio lx = L0.5-10 keV/LEdd < 10-5). Here, we present Chandra X-ray imaging spectroscopy for three BHXB systems (H 1743-322, MAXI J1659-152, and XTE J1752-223) as they fade into quiescence following an outburst. Multiple X-ray observations were taken within one month of each other, allowing us to track each individual system's X-ray spectral evolution during its decay. We compare these three systems to other BHXB systems. We confirm that quiescent BHXBs have softer X-ray spectra than low-hard-state BHXBs, and that quiescent BHXB spectral properties show no dependence on the binary system's orbital parameters. However, the observed anti-correlation between X-ray photon index (Г) and lx in the low-hard state does not continue once a BHXB enters quiescence. Instead, Γ plateaus to an average {Γ} = 2.08 ± 0.07 by the time lx reaches ~10-5. lx ~ 10-5 is thus an observationally motivated upper limit for the beginning of the quiescent spectral state. Our results are discussed in the context of different accretion flow models and across the black hole mass scale. [ABSTRACT FROM AUTHOR]

We present the first results from AMUSE-Field, a Chandra survey designed to characterize the occurrence and intensity of low-level accretion onto supermassive black holes (SMBHs) at the center of local early-type field galaxies. This is accomplished by means of a Large Program targeting a distance-limited (<30 Mpc) sample of 103 early types spanning a wide range in stellar masses. We acquired new ACIS-S observations for 61 objects down to a limiting (0.3-10 keV) luminosity of 2.5 x 1038 erg s-1, and we include an additional 42 objects with archival (typically deeper) coverage. A nuclear X-ray source is detected in 52 out of the 103 galaxies. After accounting for potential contamination from low-mass X-ray binaries, we estimate that the fraction of accreting SMBHs within the sample is 45% ± 7%, which sets a firm lower limit on the occupation fraction within the field. The measured nuclear X-ray luminosities are invariably highly sub-Eddington, with LX/LEdd ratios between ~10-4 and 10-8. As also found in a companion survey targeting Virgo early types, the active fraction increases with increasing host galaxy stellar mass, reflective of "Eddington incompleteness" within the lower-mass objects. For the Field sample, the average nuclear X-ray luminosity scales with the host stellar mass as Mstar0.71 ± 0.10, with an intrinsic scatter of 0.73 ± 0.09 dex. Qualitatively similar results hold for morphologically homogeneous (type E) or uniform sensitivity (new observations only) subsets. A majority of the AMUSE-Field galaxies (78%) inhabit groups, enabling us to investigate the influence of group richness on nuclear activity. We see no evidence for a positive correlation between nuclear X-ray luminosity, normalized to host properties, and galaxy density. Rather, while the scatter is substantial, it appears that the Eddington-scaled X-ray luminosity of group members may be slightly lower than for isolated galaxies, and that this trend continues to cluster early types. [ABSTRACT FROM AUTHOR]

We complete our census of low-level nuclear activity in Virgo Cluster early-type galaxies by searching for obscured emission using Spitzer Space Telescope mid-infrared (MIR) imaging at 24 µm. Of a total sample of 95 early-type galaxies, 53 objects are detected, including 16 showing kiloparsec-scale dust in optical images. One-dimensional and two-dimensional surface photometry of the 37 detections without extended dust features reveals that the MIR light is more centrally concentrated than the optical light as traced by Hubble Space Telescope F850LP-band images. No such modeling was performed for the sources with dust detected in the optical images. We explore several possible sources of the MIR excess emission, including obscured nuclear emission. We find that radial metallicity gradients in the stellar population appear to be a natural and most likely explanation for the observed behavior in a majority of the sources. Alternatively, if the concentrated MIR emission were due to nuclear activity, it would imply a MIR-to-X luminosity ratio ~5-10 for the low-luminosity active galactic nucleus (AGN) detected in X-rays by our survey. This ratio is an order of magnitude larger than that of typical low-luminosity AGNs and would imply an unusual spectral energy distribution. We conclude that the black holes found by our survey in quiescent early-type galaxies in Virgo have low bolometric Eddington ratios arising from low accretion rates and/or highly radiatively inefficient accretion. [ABSTRACT FROM AUTHOR]

We investigate whether magnetic interaction between close-in giant planets and their host stars produce observable statistical enhancements in stellar coronal or chromospheric activity. New Chandra observations of 12 nearby (d < 60 pc) planet-hosting solar analogs are combined with archival Chandra, XMM-Newton, and ROSAT coverage of 11 similar stars to construct a sample inoculated against inherent stellar class and planet-detection biases. Survival analysis and Bayesian regression methods (incorporating both measurements errors and X-ray upper limits; 13/23 stars have secure detections) are used to test whether “hot Jupiter” hosts are systematically more X-ray luminous than comparable stars with more distant or smaller planets. No significant correlations are present between common proxies for interaction strength (MP/a2 or 1/a) versus coronal activity (LX or LX/Lbol). In contrast, a sample of 198 FGK main-sequence stars does show a significant (∼99% confidence) increase in X-ray luminosity with MP/a2. While selection biases are incontrovertibly present within the main-sequence sample, we demonstrate that the effect is primarily driven by a handful of extreme hot-Jupiter systems with MP/a2 > 450 MJup AU–2, which here are all X-ray luminous but to a degree commensurate with their Ca II H and K activity, in contrast to presented magnetic star-planet interaction scenarios that predict enhancements relatively larger in LX. We discuss these results in the context of cumulative tidal spin-up of stars hosting close-in gas giants (potentially followed by planetary infall and destruction). We also test our main-sequence sample for correlations between planetary properties and UV luminosity or Ca II H and K emission, and find no significant dependence. [ABSTRACT FROM AUTHOR]

Distinct seed formation mechanisms are imprinted upon the fraction of dwarf galaxies currently containing a central supermassive black hole. Seeding by Population III remnants is expected to produce a higher occupation fraction than is generated with direct gas collapse precursors. Chandra observations of nearby early-type galaxies can directly detect even low-level supermassive black hole activity, and the active fraction immediately provides a firm lower limit to the occupation fraction. Here, we use the volume-limited AMUSE surveys of ∼200 optically selected early-type galaxies to characterize simultaneously, for the first time, the occupation fraction and the scaling of LX with Mstar, accounting for intrinsic scatter, measurement uncertainties, and X-ray limits. For early-type galaxies with Mstar < 1010M☼, we obtain a lower limit to the occupation fraction of >20% (at 95% confidence), but full occupation cannot be excluded. The preferred dependence of log LX upon log Mstar has a slope of ∼0.7-0.8, consistent with the “downsizing” trend previously identified from the AMUSE data set, and a uniform Eddington efficiency is disfavored at ∼2σ. We provide guidelines for the future precision with which these parameters may be refined with larger or more sensitive samples. [ABSTRACT FROM AUTHOR]

The optical light profiles of nearby early-type galaxies are known to exhibit a smooth transition from nuclear light deficits to nuclear light excesses with decreasing galaxy mass, with as much as 80% of the galaxies with stellar masses below 1010M☼ hosting a massive nuclear star cluster (NSC). At the same time, while all massive galaxies are thought to harbor nuclear supermassive black holes (SMBHs), observational evidence for SMBHs is slim at the low end of the mass function. Here, we explore the environmental dependence of the nucleation fraction by comparing two homogeneous samples of nearby field versus cluster early-type galaxies with uniform Hubble Space Telescope (HST) coverage. Existing Chandra X-ray Telescope data for both samples yield complementary information on low-level accretion onto nuclear SMBHs. Specifically, we report on dual-band (F475W and F850LP) Advanced Camera for Surveys (ACS) imaging data for 28 out of the 103 field early-type galaxies that compose the AMUSE-Field Chandra survey, and compare our results against the companion HST and Chandra surveys for a sample of 100 Virgo Cluster early-types (ACS Virgo Cluster and AMUSE-Virgo surveys, respectively). We model the two-dimensional light profiles of the field targets to identify and characterize NSCs, and find a field nucleation fraction of (at the 1σ level), consistent with the measured Virgo nucleation fraction across a comparable mass distribution (). Coupled with the Chandra result that SMBH activity is higher for the field, our findings indicate that, since the last epoch of star formation, the funneling of gas to the nuclear regions has been inhibited more effectively for Virgo galaxies, arguably via ram pressure stripping. [ABSTRACT FROM AUTHOR]

Magnetic (or tidal) interactions between “hot Jupiters” and their host stars can potentially enhance chromospheric and coronal activity. An ideal test bed for investigating this effect is provided by the extreme WASP-18 system, which features a massive (∼10 times Jupiter) close-in (≲1 day period) transiting planet orbiting a young F6 star. Optical and X-ray observations of WASP-18 were conducted in 2011 November. The high-resolution echelle spectrograph Magellan Inamori Kyocera Echelle was used on the 6.5 m Magellan Clay Telescope to obtain 13 spectra spanning planetary orbital phases of 0.7-1.4, while the X-ray Telescope on Swift provided contemporaneous monitoring with a stacked exposure of ∼50 ks. The cores of the Ca II H and K lines do not show significant variability over multiple orbits spanning ∼8 days, in contrast to the expectation of phase-dependent chromospheric activity enhancements for efficient star-planet interaction. The star is also X-ray faint, with log LX < 27.6, indicating that coronal activity is likewise low. The lack of detectable star-planet interaction in this extreme system requires that any such effect here must be transient, if indeed present. We demonstrate that searches for Ca II H and K variability can potentially mistake a stellar hotspot, if observed over a short segment of the rotation period, for planet-induced activity. Taken together, these results suggest that the utility of star-planet interaction as a robust method of estimating exoplanet magnetic field strengths may be limited. [ABSTRACT FROM AUTHOR]