Search Publications
Cosmological Fast Optical Transients with the Zwicky Transient Facility: A Search for Dirty Fireballs
Kulkarni, S. R.; Filippenko, Alexei V.; Riddle, Reed +35 more
Dirty fireballs are a hypothesized class of relativistic massive-star explosions with an initial Lorentz factor Γinit below the Γinit ~ 100 required to produce a long-duration gamma-ray burst (LGRB), but which could still produce optical emission resembling LGRB afterglows. Here we present the results of a search for on-axis …
Jet Parameters in the Black Hole X-Ray Binary MAXI J1820+070
Zdziarski, Andrzej A.; Sikora, Marek; Tetarenko, Alexandra J.
We study the jet in the hard state of the accreting black hole (BH) binary MAXI J1820+070. From the available radio-to-optical spectral and variability data, we put strong constraints on the jet parameters. We find while it is not possible to uniquely determine the jet Lorentz factor from the spectral and variability properties alone, we can estim…
Classifying Unidentified X-Ray Sources in the Chandra Source Catalog Using a Multiwavelength Machine-learning Approach
Kargaltsev, Oleg; Chen, Steven; Yang, Hui +3 more
The rapid increase in serendipitous X-ray source detections requires the development of novel approaches to efficiently explore the nature of X-ray sources. If even a fraction of these sources could be reliably classified, it would enable population studies for various astrophysical source types on a much larger scale than currently possible. Clas…
Insight-HXMT, NuSTAR, and INTEGRAL Data Show Disk Truncation in the Hard State of the Black Hole X-Ray Binary MAXI J1820+070
Zdziarski, Andrzej A.; You, Bei; Szanecki, Michał +2 more
We study X-ray and soft gamma-ray spectra from the hard state of the accreting black hole binary MAXI J1820+070. We perform an analysis of joint spectra from HXMT, NuSTAR, and INTEGRAL. We find an overall agreement between the spectra from all three satellites. Satisfactory fits to the data require substantial spectral complexity, with our models …
Light-curve Evolution of the Nearest Tidal Disruption Event: A Late-time, Radio-only Flare
Yuan, Qiang; Perlman, Eric S.; Meyer, Eileen T. +7 more
Tidal disruption events (TDEs) occur when a star passes close enough to a galaxy's supermassive black hole to be disrupted by tidal forces. We discuss new observations of IGRJ12580+0134, a TDE observed in NGC 4845 (d = 17 Mpc) in 2010 November, with the Karl G. Jansky Very Large Array (VLA 9 9 The National Radio Astronomy Obs…
Discovery of Three Candidate Magnetar-powered Fast X-Ray Transients from Chandra Archival Data
Berger, Edo; Lin, Dacheng; Irwin, Jimmy A. +1 more
It was proposed that a remnant stable magnetar could be formed in a binary neutron-star merger, leading to a fast X-ray transient (FXT) that can last for thousands of seconds. Recently, Xue et al. suggested that CDF-S XT2 was exactly such a kind of source. If confirmed, such emission can be used to search for electromagnetic counterparts to gravit…
The First Short GRB Millimeter Afterglow: The Wide-angled Jet of the Extremely Energetic SGRB 211106A
Kilpatrick, Charles D.; Bhandari, Shivani; Fong, Wen-fai +14 more
We present the discovery of the first millimeter afterglow of a short-duration γ-ray burst (SGRB) and the first confirmed afterglow of an SGRB localized by the GUANO system on Swift. Our Atacama Large Millimeter/Sub-millimeter Array (ALMA) detection of SGRB 211106A establishes an origin in a faint host galaxy detected in Hubble Space Telescope ima…
First Observation of the MeV Gamma-Ray Universe with Bijective Imaging Spectroscopy Using the Electron-tracking Compton Telescope on Board SMILE-2+
Hamaguchi, Kenji; Takada, Atsushi; Kubo, Hidetoshi +12 more
MeV gamma-rays provide a unique window for the direct measurement of line emissions from radioisotopes, but observations have made little significant progress since COMPTEL on board the Compton Gamma-ray Observatory (CGRO). To observe celestial objects in this band, we are developing an electron-tracking Compton camera (ETCC) that realizes both bi…
Photospheric Prompt Emission From Long Gamma Ray Burst Simulations. II. Spectropolarimetry
Lazzati, Davide; Parsotan, Tyler
Although gamma ray bursts (GRBs) have been detected for many decades, the lack of knowledge regarding the radiation mechanism that produces the energetic flash of radiation, or prompt emission, from these events has prevented the full use of GRBs as probes of high-energy astrophysical processes. While there are multiple models that attempt to desc…
Limits on X-Ray Polarization at the Core of Centaurus A as Observed with the Imaging X-Ray Polarimetry Explorer
Wu, Kinwah; Enoto, Teruaki; Turolla, Roberto +96 more
We present measurements of the polarization of X-rays in the 2-8 keV band from the nucleus of the radio galaxy Centaurus A (Cen A), using a 100 ks observation from the Imaging X-ray Polarimetry Explorer (IXPE). Nearly simultaneous observations of Cen A were also taken with the Swift, NuSTAR, and INTEGRAL observatories. No statistically significant…