Search Publications
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…
Polar and Equatorial Coronal Hole Winds at Solar Minima: From the Heliosphere to the Inner Corona
Zhao, L.; Landi, E.
Fast solar wind can be accelerated from at least two different sources: polar coronal holes and equatorial coronal holes. Little is known about the relationship between the wind coming from these two different latitudes and whether these two subcategories of fast wind evolve in the same way during the solar cycle. Nineteen years of Ulysses observa…
Another Short-burst Host Galaxy with an Optically Obscured High Star Formation Rate: The Case of GRB 071227
Palazzi, E.; Greiner, J.; Hunt, L. K. +9 more
We report on radio continuum observations of the host galaxy of the short gamma-ray burst 071227 (z = 0.381) with the Australia Telescope Compact Array. We detect the galaxy in the 5.5 GHz band with an integrated flux density of F ν = 43 ± 11 µJy, corresponding to an unobscured star-formation rate of about 24 M ⊙ yr
XMM-Newton Observations of Young and Energetic Pulsar J2022+3842
Pavlov, G. G.; Kargaltsev, O.; Arumugasamy, P.
We report on XMM-Newton EPIC observations of the young pulsar J2022+3842, with a characteristic age of 8.9 kyr. We detected X-ray pulsations and found the pulsation period P ≈ 48.6 ms, and its derivative \dot{P}\approx 8.6\times 10^{-14}, which is two times larger than previously reported values. The pulsar exhibits two very narrow (FWHM ~1.2 ms) …