Search Publications
X-Ray Observations of Parsec-scale Tails behind Two Middle-Aged Pulsars
Garmire, G. P.; Pavlov, G. G.; Kargaltsev, O. +2 more
Chandra and XMM-Newton resolved extremely long tails behind two middle-aged pulsars, J1509-5850 and J1740+1000. The tail of PSR J1509-5850 is discernible up to 5.6' from the pulsar, which corresponds to the projected length l⊥ = 6.5d4 pc, where d = 4d4 kpc is the distance to the pulsar. The observed tail flux is 2 …
High-Ionization Mid-Infrared Lines as Black Hole Mass and Bolometric Luminosity Indicators in Active Galactic Nuclei
Lutz, D.; Sturm, E.; Helou, G. +6 more
We present relations of the black hole mass and the optical luminosity with the velocity dispersion and the luminosity of the [Ne V] and the [O IV] high-ionization lines in the mid-infrared (MIR) for 28 reverberation-mapped active galactic nuclei. We used high-resolution Spitzer Infrared Spectrograph and Infrared Space Observatory Short Wavelength…
The Formation of Coronal Loops by Thermal Instability in Three Dimensions
Linker, Jon A.; Mikić, Zoran; Mok, Yung +1 more
Plasma loops in solar active regions have been observed in EUV and soft X-rays for decades. Their formation mechanism and properties, however, are still not fully understood. Predictions by early models, based on 1D hydrostatic equilibria with uniform plasma heating, are not consistent with high-resolution measurements. In this Letter, we demonstr…
A New Determination of the High-Redshift Type Ia Supernova Rates with the Hubble Space Telescope Advanced Camera for Surveys
Wang, L.; Lidman, C.; Amanullah, R. +28 more
We present a new measurement of the volumetric rate of SNe Ia up to a redshift of 1.7, using the HST GOODS data combined with an additional HST data set covering the GOODS-North field collected in 2004. We employ a novel technique that does not require spectroscopic data for identifying SNe Ia (although spectroscopic measurements of redshifts are …
Relativistic Iron Line Emission from the Neutron Star Low-Mass X-Ray Binary 4U 1636-536
Kaaret, Philip; Pandel, Dirk; Corbel, Stephane
We present an analysis of XMM-Newton and RXTE data from three observations of the neutron star LMXB 4U 1636-536. The X-ray spectra show clear evidence of a broad, asymmetric iron emission line extending over the energy range 4-9 keV. The line profile is consistent with relativistically broadened Fe Kα emission from the inner accretion disk. The Fe…
Outbursts Large and Small from EXO 2030+375
Finger, Mark H.; Wilson, Colleen A.; Camero-Arranz, Ascensión
During the summer of 2006, the accreting X-ray pulsar EXO 2030+375 underwent its first giant outburst since its discovery in 1985. Our observations include the first ever of the rise of a giant outburst of EXO 2030+375. EXO 2030+375 was monitored daily with the Rossi X-Ray Timing Explorer (RXTE) from 2006 June to 2007 May. During the giant outburs…
Effects of Scattering on Radio Emission from the Quiet Sun at Low Frequencies
MacDowall, R. J.; Thejappa, G.
The observations of the quiet Sun at meter and decameter wavelengths show that its brightness temperatures can be ~1 order of magnitude lower than the expected values of 106 K and the apparent diameters can be very large. We examine whether this unusual behavior is due to refraction in the smoothly varying coronal plasma and scattering …
Detection of a Hot Subdwarf Companion to the Be Star FY Canis Majoris
Gies, Douglas R.; Peters, Geraldine J.; Grundstrom, Erika D. +1 more
The rapid rotation of Be stars may be caused in some cases by past mass and angular momentum accretion in an interacting binary in which the mass donor is currently viewed as a small, hot subdwarf stripped of its outer envelope. Here we report on the spectroscopic detection of such a subdwarf in the Be binary system FY Canis Majoris from the analy…
Understanding the 8 µm versus Paα Relationship on Subarcsecond Scales in Luminous Infrared Galaxies
Colina, Luis; Alonso-Herrero, Almudena; Díaz-Santos, Tanio +3 more
This work explores in detail the relation between the 8 µm and the Paα emissions for 122 H II regions identified in a sample of 10 low-z LIRGs with nearly constant metallicity [12 + log (O/H) ~ 8.8]. We use Gemini T-ReCS high spatial resolution (lesssim0.4''~120 pc for the average distance of 60 Mpc of our sample) mid-infrared imaging (at 8.…
Solar Magnetic Tracking. II. The Apparent Unipolar Origin of Quiet-Sun Flux
Lamb, D. A.; DeForest, C. E.; Hagenaar, H. J. +2 more
We investigate the origin of small-scale flux concentrations in the quiet Sun. In apparent violation of the physical requirement for flux balance, 94% of the features containing newly detected flux are unipolar at a resolution of 1.2''. We analyze 2619 of these apparent unipolar emergences in an image sequence from the SOHO MDI magnetograph and co…