Search Publications
Strong Soft X-Ray Excess in 2015 XMM-Newton Observations of BL Lac OJ 287
Dewangan, G. C.; Pal, Main; Kushwaha, Pankaj +1 more
We report a strong soft X-ray excess in the BL Lacartae γ-ray blazar OJ 287 during long exposure in 2015 May, among two of the latest XMM-Newton observations performed in 2015 and 2018 May. In the case of the 2015 May observation, a log parabola model fits the EPIC-pn data well, while a log parabola plus a power law describes the overall simultane…
NuSTAR Perspective on High-redshift MeV Blazars
Ajello, M.; Gasparrini, D.; Marchesi, S. +7 more
With bolometric luminosities exceeding 1048 erg s-1, powerful jets, and supermassive black holes at their center, MeV blazars are some of the most extreme sources in the universe. Recently, the Fermi-Large Area Telescope detected five new γ-ray emitting MeV blazars beyond redshift z = 3.1. With the goal of precisely character…
Toward a Direct Measure of the Galactic Acceleration
De Rosa, Robert J.; Huber, Daniel; Rhode, Katherine L. +9 more
High-precision spectrographs can enable not only the discovery of exoplanets, but can also provide a fundamental measurement in Galactic dynamics. Over about 10 year baselines, the expected change in the line-of-sight velocity due to the Galaxy's gravitational field for stars at ∼kiloparsec scale distances above the Galactic midplane is ∼few tens …
Mapping Outflowing Gas in the Fermi Bubbles: A UV Absorption Survey of the Galactic Nuclear Wind
Jenkins, Edward B.; Savage, Blair D.; Lockman, Felix J. +5 more
Using new ultraviolet (UV) spectra of five background quasars from the Cosmic Origins Spectrograph on the Hubble Space Telescope, we analyze the low-latitude ( $| b| =20^\circ \mbox{--}30^\circ $ ) regions of the Fermi Bubbles, the giant gamma-ray-emitting lobes at the Galactic Center. We combine these data with previous UV and atomic hydrogen (H …
CTCV J2056-3014: An X-Ray-faint Intermediate Polar Harboring an Extremely Fast-spinning White Dwarf
Mukai, K.; Oliveira, A. S.; Rodrigues, C. V. +2 more
We report on XMM-Newton X-ray observations that reveal CTCV J2056-3014 to be an unusual accretion-powered, intermediate polar (IP) system. It is a member of the class of X-ray-faint IPs whose space density remains unconstrained but potentially very high, with Lx,0.3-12 keV of 1.8 × 1031 erg s-1. We discovered a coh…
Evidence for a Coronal Shock Wave Origin for Relativistic Protons Producing Solar Gamma-Rays and Observed by Neutron Monitors at Earth
Kouloumvakos, Athanasios; Rouillard, Alexis P.; Papaioannou, Athanasios +4 more
We study the solar eruptive event on 2017 September 10 that produced long-lasting >100 MeV γ-ray emission and a ground level enhancement (GLE72). The origin of the high-energy ions producing late-phase gamma-ray emission (LPGRE) is still an open question, but a possible explanation is proton acceleration at coronal shocks produced by coronal ma…
The Magnetic Field of the Active Planet-hosting M Dwarf AU Mic
Kochukhov, Oleg; Reiners, Ansgar
AU Mic is a young, very active M dwarf star with a debris disk and at least one transiting Neptune-size planet. Here we present a detailed analysis of the magnetic field of AU Mic based on previously unpublished high-resolution optical and near-infrared spectropolarimetric observations. We report a systematic detection of circular and linear polar…
A Microlensing Accretion Disk Size Measurement in the Lensed Quasar WFI 2026-4536
Millon, Martin; Bonvin, Vivien; Bentz, Misty C. +4 more
We use 13 seasons of R-band photometry from the 1.2 m Leonard Euler Swiss Telescope at La Silla to examine microlensing variability in the quadruply imaged lensed quasar WFI 2026-4536. The lightcurves exhibit ∼0.2 mag of uncorrelated variability across all epochs and a prominent single feature of ∼0.1 mag within a single season. We analyze this va…
Amplification of Brightness Variability by Active-region Nesting in Solar-like Stars
Solanki, Sami K.; Shapiro, Alexander I.; Krivova, Natalie A. +1 more
Kepler observations revealed that hundreds of stars with near-solar fundamental parameters and rotation periods have much stronger and more regular brightness variations than the Sun. Here we identify one possible reason for the peculiar behavior of these stars. Inspired by solar nests of activity, we assume that the degree of inhomogeneity of act…
A Supernova Candidate at z = 0.092 in XMM-Newton Archival Data
Mereghetti, Sandro; Esposito, Paolo; Tiengo, Andrea +14 more
During a search for X-ray transients in the XMM-Newton archive within the EXTraS project, we discovered a new X-ray source that is detected only during an ∼5 min interval of an ∼21 hr-long observation performed on 2011 June 21 (EXMM 023135.0-603743, probability of a random Poissonian fluctuation: ∼1.4 × 10-27). With dedicated follow-up …