Search Publications
X- and γ-Ray Pulsations of the Nearby Radio-faint PSR J1741-2054
Belfiore, A.; Camilo, F.; Marelli, M. +6 more
We report the results of a deep XMM-Newton observation of the radio-faint γ-ray pulsar J1741-2054 and its nebula together with the analysis of five years of Fermi Large Area Telescope (LAT) data. The X-ray spectrum of the pulsar is consistent with an absorbed power law plus a blackbody, originating at least partly from the neutron star cooling. Th…
Near-UV Absorption in Very Cool DA White Dwarfs
Saumon, D.; Holberg, J. B.; Kowalski, P. M.
The atmospheres of very cool, hydrogen-rich white dwarfs (WDs) (T eff < 6000 K) are challenging to model because of the increased complexity of the equation of state, chemical equilibrium, and opacity sources in a low-temperature, weakly ionized dense gas. In particular, many models that assume relatively simple models for the broade…
Low-mass X-Ray Binaries and Globular Clusters Streamers and Arcs in NGC 4278
Fabbiano, G.; D'Abrusco, R.; Brassington, N. J.
We report significant inhomogeneities in the projected two-dimensional spatial distributions of low-mass X-ray binaries (LMXBs) and globular clusters (GCs) of the intermediate mass elliptical galaxy NGC 4278. In the inner region of NGC 4278, a significant arc-like excess of LMXBs extending south of the center at ~50'' in the western side of the ga…
Deep VLA Images of the HH 124 IRS Radio Cluster and Its Surroundings, and a New Determination of the Distance to NGC 2264
Rodríguez, Luis F.; Loinard, Laurent; Dzib, Sergio A. +1 more
We present new deep (σ ~ 6 µJy) radio images of the HH 124 IRS radio cluster at 4.8 and 7.5 GHz. We detect a total of 50 radio sources, most of them compact. Variability and spectral indices were analyzed in order to determine the nature of the sources and of their radio emission. A proper motion study was also performed for several of these…
Origin of Multi-band Emission from the Microquasar Cygnus X-1
Zhang, Jianfu; Xu, Bing; Lu, Jufu
We study the origin of non-thermal emissions from the Galactic black hole X-ray binary Cygnus X-1, which is a confirmed high-mass microquasar. By analogy with the methods used in studies of active galactic nuclei, we propose a two-dimensional, time-dependent radiation model from the microquasar Cygnus X-1. In this model, the evolution equation for…
Near-infrared Detection of WD 0806-661 B with the Hubble Space Telescope
Luhman, K. L.; Morley, C. V.; Burgasser, A. J. +2 more
WD 0806-661 B is one of the coldest known brown dwarfs (T eff = 300-345 K) based on previous mid-infrared photometry from the Spitzer Space Telescope. In addition, it is a benchmark for testing theoretical models of brown dwarfs because its age and distance are well constrained via its primary star (2 ± 0.5 Gyr, 19.2 ± 0.6 pc). We prese…
Constraints on Two Active Galactic Nuclei in the Merger Remnant COSMOS J100043.15+020637.2
Comerford, J. M.; Wrobel, J. M.; Middelberg, E.
COSMOS J100043.15+020637.2 is a merger remnant at z = 0.36 with two optical nuclei, NW and SE, offset by 500 mas (2.5 kpc). Prior studies suggest two competing scenarios for these nuclei: (1) SE is an active galactic nucleus (AGN) lost from NW due to a gravitational-wave recoil. (2) NW and SE each contain an AGN, signaling a gravitational-slingsho…
A Seyfert-2-like Spectrum in the High-mass X-Ray Binary Microquasar V4641 Sgr
Miller, Jon M.; Reynolds, M. T.; Maitra, Dipankar +1 more
We present an analysis of three archival Chandra observations of the black hole V4641 Sgr, performed during a decline into quiescence. The last two observations in the sequence can be modeled with a simple power law. The first spectrum, however, is remarkably similar to spectra observed in Seyfert-2 active galactic nuclei, which arise through a co…
Search for Higgs Shifts in White Dwarfs
Onofrio, Roberto; Wegner, Gary A.
We report on a search for differential shifts between electronic and vibronic transitions in carbon-rich white dwarfs BPM 27606 and Procyon B. The absence of differential shifts within the spectral resolution and taking into account systematic effects such as space motion and pressure shifts allows us to set the first upper bound of astrophysical …
The Vela Pulsar with an Active Fallback Disk
Ginski, Christian; Werner, Klaus; Neuhäuser, Ralph +4 more
Fallback disks are expected to form around young neutron stars. The presence of these disks can be revealed by their blackbody spectrum in the infrared, optical, and UV bands. We present a re-reduction of the archival optical and infrared data of the Vela pulsar, together with the existing infrared and UV spectrum of Vela, and model their unpulsed…