A5076006347- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Adaptive optics and wavefront sensing
- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Relativity and Gravitational Theory
- Scientific Research and Discoveries
- Advanced X-ray Imaging Techniques
- Particle Accelerators and Free-Electron Lasers
- Advanced Measurement and Metrology Techniques
- Crystallography and Radiation Phenomena
- Cosmology and Gravitation Theories
- Astro and Planetary Science
- Advanced optical system design
- History and Theory of Mathematics
- Dark Matter and Cosmic Phenomena
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Medical Imaging Techniques and Applications
University of Alabama
2016-2025
Seoul National University
2017-2018
Harvard University Press
2013
University of Michigan
2001-2010
Institute of Astronomy
2006
University of Cambridge
2006
University of Virginia
1996-1998
Abstract Fast X-ray transients (FXTs) are a new observational class of phenomena with no clear physical origin. This is at least partially consequence limited multiwavelength follow-up this in real time. Here we present deep optical ( g - and i -band) photometry Keck, prompt radio observations the Very Large Array FXT 210423 obtained δ t ≈ 14–36 days since trigger. We use these multiband observations, combined publicly available data sets, to constrain presence properties on-axis off-axis...
We have investigated the X-ray spectral properties of a collection low-mass binaries (LMXBs) within sample 15 nearby early-type galaxies using proprietary and archival data from Chandra X-Ray Observatory. find that spectrum sum sources in given galaxy is remarkably similar to when only with luminosities less than 1039 ergs s-1 (0.3-10 keV) are considered. Fitting these lower luminosity all simultaneously power-law model led best-fit exponent Γ = 1.56 ± 0.02 (90% confidence), thermal...
A Chandra ACIS S3 observation of the X-ray faint elliptical galaxy NGC 4697 resolves much emission (61% counts from within one effective radius) into 90 point sources, which ~80 are low-mass binaries (LMXBs) associated with this galaxy. The dominance LMXBs indicates that early-type galaxies have lost their interstellar gas. On other hand, a modest portion is due to hot Of unresolved emission, it likely about half fainter LMXBs, while (~23% total count rate) X-ray-emitting gas in has rather...
(Abridged) A high fraction of the Low Mass X-ray Binaries (LMXBs) in early-type galaxies are associated with globular clusters (GCs). Here, we discuss correlations between LMXBs and GCs a sample four galaxies. There is some evidence that (f_X-GC) increases along Hubble sequence from spiral bulges to S0s Es cDs. On other hand, which contain sources appears be roughly constant at f_GC-X ~ 4%. strong tendency for optically more luminous GCs. However, this correlation consistent probability...
We analyze X-ray spatial and spectral data on the giant elliptical galaxy NGC 4472, brightest in Virgo cluster. The contours of 4472 are elongated northeast-southwest direction, perhaps as a result motion through intracluster gas. A bow shock-like structure is evident galaxy's north side. temperature at given radius this shock region slightly higher than same southwest Away from region, surface brightness profile can be traced out to 260 kpc direction. Beyond kpc, we find evidence for...
Chandra observations of the X-ray-faint elliptical galaxy NGC 4697 resolve much X-ray emission (61% within one effective radius) into ~80 point sources, which most are low-mass binaries (LMXBs). These LMXBs provide bulk hard and soft as well. Of remaining unresolved emission, it is likely that about half from fainter LMXBs, while other (~23% total emission) interstellar gas. Three resolved sources supersoft sources. In outer regions 4697, eight (about 25%) coincident with candidate globular...
We report [O III] 5007 Angstrom and [N II] 6583 emission from a globular cluster harboring the ultraluminous X-ray source (ULX) CXOJ033831.8-352604 in Fornax elliptical galaxy NGC1399. No accompanying Balmer lines are present spectrum. One possibility is that forbidden emanate illuminated debris of star has been tidally-disrupted by an intermediate-mass black hole (IMBH), with this also feeding leading to observed emission. The line strengths indicate minimum size emitting region ~10^15 cm,...
Gas undergoing Bondi accretion onto a supermassive black hole (SMBH) becomes hotter toward smaller radii. We searched for this signature with Chandra observation of the hot gas in NGC 3115, which optical observations show has very massive SMBH. Our analysis suggests that we are resolving, first time, flow within radius an temperature is rising galaxy center as expected all models gravitationally capturing ambient gas. There no hard central point source could cause such apparent rise...
Very few galactic nuclei are found to show significant X-ray quasi-periodic oscillations (QPOs). After carefully modeling the noise continuum, we find that ∼3.8 hr QPO in ultrasoft active nucleus candidate 2XMM J123103.2+110648 was significantly detected (∼5σ) two XMM-Newton observations 2005, but not one 2003. The root mean square (rms) is very high and increases from ∼25% 0.2–0.5 keV ∼50% 1–2 keV. probably corresponds low-frequency type Galactic black hole binaries, considering its large...
Observational confirmation of hot accretion model predictions has been hindered by the challenge to resolve spatially Bondi radii black holes with X-ray telescopes. Here, we use Megasecond Chandra Visionary Project (XVP) observation NGC~3115 supermassive hole place first direct observational constraints on and spectroscopically resolved structures emitting gas inside radius a hole. We measured temperature density profiles from fraction out tens (R_B = 2.4-4.8 arcsec 112-224 pc). The...
Abstract Dual active galactic nuclei (DAGN) are important for understanding galaxy-merger-triggered fueling of black holes and the hierarchical growth structures. The least explored type DAGN those associated with mergers two dwarf galaxies. According to observations cosmological simulations, galaxies most abundant in early universe galaxy-merger rate is dominated by dwarfs. However, these generally too distant be directly observed, low-redshift dwarf-dwarf merger-related notoriously hard...
We have spatially and spectrally resolved the sources of X-ray emission from X-ray-faint S0 galaxy NGC 1553 using an observation Chandra X-Ray Observatory. The majority (70%) in 0.3-10.0 keV band is diffuse, remaining 30% into 49 discrete sources. Most associated with appear to be low-mass binaries (LMXBs). luminosity function LMXB well fitted by a broken power law break comparable Eddington for 1.4 M☉ neutron star. It likely that those luminosities above are accreting black holes, below...
The X-ray populations of Local group galaxies have been classified in detail by Einstein, ROSAT and ASCA revealing a mix binaries, supernova remnants HII regions. However, these observatories were unable to resolve sources beyond the local group. With Chandra's exquisite spatial resolution we are able sample nearby galaxies. We show that there highly significant differences colors bulge disk systems. These can be used as basis classify low high mass supersoft sources. While it is impossible...
We have searched for ultraluminous X-ray sources (ULXs) in a sample of 28 elliptical and S0 galaxies observed with Chandra. find that the number detected at flux level would correspond to 0.3-10 keV luminosity ~2 × 1039 ergs s-1 or greater (for which we used designation very [VULXs]) distance each galaxy is equal expected foreground/background objects. In addition, VULXs are uniformly distributed over Chandra field view rather than like optical light galaxies, strengthening argument...
We report on the discovery of an ultrasoft X-ray transient source, 3XMM J152130.7+074916. It was serendipitously detected in XMM-Newton observation 2000 August 23, and its location is consistent with center galaxy SDSS J152130.72+074916.5 (z=0.17901 d_L=866 Mpc). The high-quality spectrum can be fitted a thermal disk apparent inner temperature 0.17 keV rest-frame 0.24-11.8 unabsorbed luminosity ~5e43 erg/s, subject to fast-moving warm absorber. Short-term variability also clearly observed,...
We present the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X), a probe-class mission concept selected study by NASA. It combines huge collecting area, high throughput, broad energy coverage, and excellent spectral temporal resolution in single facility. STROBE-X offers an enormous increase sensitivity X-ray timing, extending these techniques to extragalactic targets first time. is also agile capable of rapid response transient events, making it essential...
Abstract We recently discovered the X-ray/optical outbursting source 3XMM J215022.4−055108. It was best explained as tidal disruption of a star by an intermediate-mass black hole mass few tens thousand solar masses in massive cluster at outskirts large barred lenticular galaxy D L = 247 Mpc. However, we could not completely rule out Galactic cooling neutron alternative explanation for source. In order to further pin down nature source, have obtained new multiwavelength observations...
Abstract We investigate the role of galaxy mergers in triggering active galactic nuclei (AGN) nearby universe. Our analysis is based on a sample 79 post-merger remnant galaxies with deep X-ray observations from Chandra/XMM-Newton capable detecting low-luminosity AGN ≥10 40.5 erg s −1 . This derived visually classified, volume-limited 807 post-mergers identified Sloan Digital Sky Survey Data Release 14 log M * / ⊙ ≥ 10.5 and 0.02 ≤ z 0.06. find that fraction this 55.7% ± 5.6% compared to...
Post-starburst galaxies (PSBs) are transition showing evidence of recent rapid star formation quenching. To understand the role galaxy mergers in triggering quenching, we investigate incidence PSBs and resolved PSB properties post-merger using both SDSS single-fiber spectra MaNGA IFU spectra. We find post-mergers have a excess 10 - 20 times that relative to their control diagnostics. A similar ~ 19 is also found fraction central (C)PSBs ring-like (R)PSBs diagnostic. However, 60% CPSBs +...
Abstract The existence of high- z overmassive supermassive black holes represents a major conundrum in our understanding hole evolution. In this Letter, we probe from the observational point view how early Universe environmental conditions could have acted as an evolutionary mechanism for accelerated growth first holes. Under assumption that is dominated by dwarf galaxies, investigate hypothesis dwarf–dwarf galaxy interactions trigger accretion. We present discovery 82 pairs and 11 groups...
We present new multi-wavelength observations of two ultraluminous X-ray sources (ULXs) hosted by globular clusters (GCs) in the giant elliptical NGC 1399, focusing on CXO J0338318-352604 (GCU7), only second GC ULX known to have luminous optical emission lines. Notably, NII and OIII is observed spectra, suggesting H-poor material. Previous work suggested possibility that properties GCU7 could be explained tidal disruption a horizontal branch star an intermediate-mass black hole. use data show...