Search Publications
A Radio-loud Semiregular Variable
Luque-Escamilla, Pedro L.; Martí, Josep
As a byproduct of our search for Galactic stellar systems with gamma-ray emission, we have identified an unrelated cool and evolved star (IRC-10412) that attracted our attention due to its strong radio emission level with a spectral index matching, almost perfectly, the canonical +0.6 value expected from an ionized stellar wind. A follow-up observ…
Historical Fermi All-sky Variability Analysis of Galactic Flares
Ajello, M.; Buehler, R.; Kocevski, D. +2 more
The Fermi All-sky Variability Analysis (FAVA) provides a photometric alternative for identifying week-long gamma-ray flares across the entire sky while being independent of any diffuse Galactic or isotropic emission model. We reviewed 779 weeks of Fermi Large Area Telescope data analyzed by FAVA to estimate the rate and origin of Galactic gamma-ra…
A Multiwavelength Approach to Constraining the Merger Properties of ACT-CL J0034.4+0225
Hilton, Matt; Sifón, Cristóbal; Hughes, John P. +10 more
ACT-CL J0034.4+0225 is a previously unrecognized merging galaxy cluster at z = 0.38588 ± 0.00068. Our primary evidence is provided by a 21 ks Chandra image that shows two surface brightness peaks separated by ∼49″ (259 kpc) surrounded by an extended cluster gas distribution. Each gas peak contains a brightest cluster galaxy, offset from the gas pe…
Escape Velocity Mass of A1063
Miller, Christopher J.; Kremin, Anthony; Rodriguez, Alexander +1 more
We measure the radius–velocity phase-space edge profile of A1063 using galaxy redshifts from Karman et al. and Mercurio et al. Combined with a cosmological model and after accounting for interlopers and sampling effects, we infer the escape velocity profile. Using the Poisson equation, we then directly constrain the gravitational potential profile…
Classification of Wolf–Rayet Stars Using Ensemble-based Machine Learning Algorithms
Das, Ramkrishna; Bhattacharya, Rajorshi; Lewis, Megan O. +2 more
We develop a robust machine learning classifier model utilizing the eXtreme-Gradient Boosting (XGB) algorithm for improved classification of Galactic Wolf–Rayet (WR) stars based on IR colors and positional attributes. For our study, we choose an extensive data set of 6555 stellar objects (from 2MASS and AllWISE data releases) lying in the Milky Wa…
X-Ray Observations of the Enigmatic Wolf–Rayet System θ Mus: Two's Company but Three's a Crowd
Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel +1 more
θ Mus is a remarkable spectroscopic binary (SB) consisting of a carbon-type Wolf–Rayet star and OV companion (WC6+O6–7V) in a ≈19 days orbit. In addition an O-supergiant is visually detected at a small offset of 46 mas and if gravitationally bound to the SB system would have an orbital period of many decades. θ Mus is X-ray bright and a nonthermal…
A Tale of Three: Magnetic Fields along the Orion Integral-shaped Filament as Revealed by the JCMT BISTRO Survey
Zhang, Yapeng; Pattle, Kate; Karoly, Janik +152 more
As part of the B-fields In Star-forming Region Observations survey, we present James Clerk Maxwell Telescope (JCMT) 850 µm polarimetric observations toward the Orion integral-shaped filament (ISF) that covers three portions known as OMC-1, OMC-2, and OMC-3. The magnetic field threading the ISF seen in the JCMT POL-2 map appears as a tale of …
Multi-epoch UV–X-Ray Spectral Study of NGC 4151 with AstroSat
Papadakis, I. E.; Singh, K. P.; Dewangan, G. C. +8 more
We present a multiwavelength spectral study of NGC 4151 based on five epochs of simultaneous AstroSat observations in the near-ultraviolet (NUV) to hard X-ray band (∼0.005–80 keV) during 2017–2018. We derived the intrinsic accretion disk continuum after correcting for internal and Galactic extinction, contributions from broad- and narrow-line regi…
The Nature of a Recently Discovered Wolf–Rayet Binary: Archetype of Stripping?
Massey, Philip; Morrell, Nidia I.; Penny, Laura R. +2 more
LMCe055-1 was recently discovered in a survey for Wolf–Rayets (WRs) in the Large Magellanic Cloud, and classified as a WN4/O4, a lower-excitation version of the WN3/O3 class discovered as part of the same survey. Its absolute magnitude precluded it from being a WN4+O4 binary. Optical Gravitational Lensing Experiment photometry shows shallow primar…
Investigation of the Nonthermal X-Ray Emission from the Supernova Remnant CTB 37B Hosting the Magnetar CXOU J171405.7-381031
An, Hongjun; Mori, Kaya; Safi-Harb, Samar +4 more
We present a detailed X-ray investigation of a region (S1) exhibiting nonthermal X-ray emission within the supernova remnant (SNR) CTB 37B hosting the magnetar CXOU J171405.7‑381031. Previous analyses modeled this emission with a power law (PL), inferring various values for the photon index (Γ) and absorbing column density (N H). Based …