Search Publications
The Radius of PSR J0740+6620 from NICER and XMM-Newton Data
Guillemot, L.; Kerr, M.; Ray, P. S. +25 more
PSR J0740+6620 has a gravitational mass of 2.08 ± 0.07 M⊙, which is the highest reliably determined mass of any neutron star. As a result, a measurement of its radius will provide unique insight into the properties of neutron star core matter at high densities. Here we report a radius measurement based on fits of rotating hot spot patte…
A NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton Spectroscopy
Remillard, Ronald A.; Okajima, Takashi; Bogdanov, Slavko +27 more
We report on Bayesian estimation of the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740+6620, conditional on pulse-profile modeling of Neutron Star Interior Composition Explorer X-ray Timing Instrument event data. We condition on informative pulsar mass, distance, and orbital inclination priors derived from the jo…
ASASSN-14ko is a Periodic Nuclear Transient in ESO 253-G003
Holoien, Thomas W. -S.; Vallely, Patrick J.; Auchettl, Katie +24 more
We present the discovery that ASASSN-14ko is a periodically flaring active galactic nucleus at the center of the galaxy ESO 253-G003. At the time of its discovery by the All-Sky Automated Survey for Supernovae (ASAS-SN), it was classified as a supernova close to the nucleus. The subsequent 6 yr of V- and g-band ASAS-SN observations revealed that A…
Possible X-Ray Quasi-periodic Eruptions in a Tidal Disruption Event Candidate
Miniutti, Giovanni; Kara, Erin; Giustini, Margherita +3 more
X-ray quasi-periodic eruptions (QPEs) are a recently discovered phenomenon associated with supermassive black holes at the centers of galaxies. They are high-amplitude soft X-ray flares that recur on timescales of hours, but what causes these flares remains uncertain. In the two years since their original discovery, four known QPE-hosting galaxies…
AGN STORM 2. I. First results: A Change in the Weather of Mrk 817
Gorjian, Varoujan; Treu, Tommaso; Kaspi, Shai +71 more
We present the first results from the ongoing, intensive, multiwavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this active galactic nucleus was, in part, selected for its historically unobscured nature, we discovered that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad, and narrow UV absorp…
The Panchromatic Afterglow of GW170817: The Full Uniform Data Set, Modeling, Comparison with Previous Results, and Implications
Frail, D. A.; Hallinan, G.; Murphy, E. J. +35 more
We present the full panchromatic afterglow light-curve data of GW170817, including new radio data as well as archival optical and X-ray data, between 0.5 and 940 days post-merger. By compiling all archival data and reprocessing a subset of it, we have evaluated the impact of differences in data processing or flux determination methods used by diff…
A Family Tree of Optical Transients from Narrow-line Seyfert 1 Galaxies
Duev, Dmitry A.; Rusholme, Ben; Stern, Daniel +18 more
The Zwicky Transient Facility (ZTF) has discovered five events (0.01 < z < 0.4) belonging to an emerging class of active galactic nuclei (AGNs) undergoing smooth, large-amplitude, and rapidly rising flares. This sample consists of several transients initially classified as supernovae with narrow spectral lines. However, upon closer inspectio…
Rapid Accretion State Transitions following the Tidal Disruption Event AT2018fyk
Wevers, T.; Uttley, P.; Miller-Jones, J. C. A. +7 more
Following a tidal disruption event (TDE), the accretion rate can evolve from quiescent to near-Eddington levels and back over timescales of months to years. This provides a unique opportunity to study the formation and evolution of the accretion flow around supermassive black holes (SMBHs). We present 2 yr of multiwavelength monitoring observation…
Improving Damped Random Walk Parameters for SDSS Stripe 82 Quasars with Pan-STARRS1
Ivezić, Željko; MacLeod, Chelsea; Suberlak, Krzysztof L.
We use the Panoramic Survey Telescope and Rapid Response System 1 Survey (Pan-STARRS1, PS1) data to extend the Sloan Digital Sky Survey (SDSS) Stripe 82 quasar light curves. Combining PS1 and SDSS light curves provides a 15 yr baseline for 9248 quasars—5 yr longer than prior studies that used only SDSS. We fit the light curves with the damped rand…
On the Observational Difference between the Accretion Disk-Corona Connections among Super- and Sub-Eddington Accreting Active Galactic Nuclei
Brandt, W. N.; Luo, B.; Gallagher, S. C. +5 more
We present a systematic X-ray and multiwavelength study of a sample of 47 active galactic nuclei (AGNs) with reverberation mapping measurements. This sample includes 21 super-Eddington accreting AGNs and 26 sub-Eddington accreting AGNs. Using high-state observations with simultaneous X-ray and UV/optical measurements, we investigate whether super-…