Search Publications
The Radius of PSR J0740+6620 from NICER with NICER Background Estimates
Remillard, Ronald A.; Bogdanov, Slavko; Salmi, Tuomo +15 more
We report a revised analysis for the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740+6620, studied previously with joint fits to NICER and XMM-Newton data by Riley et al. (2021) and Miller et al. (2021). We perform a similar Bayesian estimation for the pulse-profile model parameters, except that instead of fitting…
The Coma Cluster at LOFAR Frequencies. II. The Halo, Relic, and a New Accretion Relic
Simionescu, A.; Zhang, X.; Brunetti, G. +26 more
We present LOw Frequency ARray observations of the Coma Cluster field at 144 MHz. The cluster hosts one of the most famous radio halos, a relic, and a low surface brightness bridge. We detect new features that allow us to make a step forward in the understanding of particle acceleration in clusters. The radio halo extends for more than 2 Mpc, whic…
The X-Ray Polarization View of Mrk 421 in an Average Flux State as Observed by the Imaging X-Ray Polarimetry Explorer
Wu, Kinwah; Enoto, Teruaki; Turolla, Roberto +100 more
Particle acceleration mechanisms in supermassive black hole jets, such as shock acceleration, magnetic reconnection, and turbulence, are expected to have observable signatures in the multiwavelength polarization properties of blazars. The recent launch of the Imaging X-Ray Polarimetry Explorer (IXPE) enables us, for the first time, to use polariza…
Exploring the AGN-Ram Pressure Stripping Connection in Local Clusters
Fritz, Jacopo; Vulcani, Benedetta; Poggianti, Bianca M. +8 more
Ram pressure stripping (RPS) by the intracluster medium is one of the most advocated mechanisms that affect the properties of cluster galaxies. A recent study based on a small sample has found that many galaxies showing strong signatures of RPS also possess an active galactic nucleus (AGN), suggesting a possible correlation between the two phenome…
The X-Ray and Radio Loud Fast Blue Optical Transient AT2020mrf: Implications for an Emerging Class of Engine-driven Massive Star Explosions
Kulkarni, S. R.; Chandra, Poonam; Perley, Daniel A. +9 more
We present AT2020mrf (SRGe J154754.2+443907), an extra-galactic (z = 0.1353) fast blue optical transient (FBOT) with a rise time of t g,rise = 3.7 days and a peak luminosity of M g,peak = -20.0. Its optical spectrum around peak shows a broad (v ~ 0.1c) emission feature on a blue continuum (T ~ 2 × 104 K), which b…
A Disk Instability Model for the Quasi-periodic Eruptions of GSN 069
Li, Shuang-Liang; Miniutti, Giovanni; Cao, Xinwu +2 more
GSN 069 is a recently discovered quasi-periodic eruption (QPE) source recurring about every 9 hr. The mechanism for the QPEs of GSN 069 is still unclear. In this work, a disk instability model is constructed to explain GSN 069 based on Pan et al. (PLC21), where the authors proposed a toy model for the repeating changing-look active galactic nuclei…
X-Ray Coronal Properties of Swift/BAT-selected Seyfert 1 Active Galactic Nuclei
Ricci, Claudio; Stern, Daniel; Urry, C. Megan +9 more
The corona is an integral component of active galactic nuclei (AGNs) which produces the bulk of the X-ray emission above 1-2 keV. However, many of its physical properties and the mechanisms powering this emission remain a mystery. In particular, the temperature of the coronal plasma has been difficult to constrain for large samples of AGNs, as con…
The Tidal Disruption Event AT2021ehb: Evidence of Relativistic Disk Reflection, and Rapid Evolution of the Disk-Corona System
Kulkarni, S. R.; Sunyaev, R.; Cenko, S. Bradley +29 more
We present X-ray, UV, optical, and radio observations of the nearby (≈78 Mpc) tidal disruption event AT2021ehb/ZTF21aanxhjv during its first 430 days of evolution. AT2021ehb occurs in the nucleus of a galaxy hosting a≈107 M ⊙ black hole (M BH inferred from host galaxy scaling relations). High-cadence Swift and Neut…
Intracluster Magnetic Filaments and an Encounter with a Radio Jet
Brunetti, G.; Forman, W.; Jones, T. W. +6 more
Thin synchrotron-emitting filaments are increasingly seen in the intracluster medium (ICM). We present the first example of a direct interaction between a magnetic filament, a radio jet, and a dense ICM clump in the poor cluster A194. This enables the first exploration of the dynamics and possible histories of magnetic fields and cosmic rays in su…
Evolution of a Relativistic Outflow and X-Ray Corona in the Extreme Changing-look AGN 1ES 1927+654
Fabian, Andrew C.; Remillard, Ronald A.; Ricci, Claudio +8 more
1ES 1927+654 is a paradigm-defying active galactic nucleus (AGN) and one of the most peculiar X-ray nuclear transients. In early 2018, this well-known AGN underwent a changing-look event, in which broad optical emission lines appeared and the optical flux increased. Yet, by 2018 July, the X-ray flux had dropped by over two orders of magnitude, ind…