Search Publications
On the Origin of the Supergiant H I Shell and Putative Companion in NGC 6822
Cannon, John M.; Dolphin, Andrew E.; Skillman, Evan D. +6 more
We present new Hubble Space Telescope Advanced Camera for Surveys imaging of six positions spanning 5.8 kpc of the H I major axis of the Local Group dIrr NGC 6822, including both the putative companion galaxy and the large H I hole. The resulting deep color-magnitude diagrams show that NGC 6822 has formed >50% of its stars in the last ~5 Gyr. T…
The Y SZ-YX Scaling Relation as Determined from Planck and Chandra
Vikhlinin, Alexey; More, Surhud; Rozo, Eduardo
Sunyaev-Zeldovich (SZ) clusters surveys, such as Planck, the South Pole Telescope, and the Atacama Cosmology Telescope, will soon be publishing several hundred SZ-selected systems. The key ingredient required to transport the mass calibration from current X-ray-selected cluster samples to these SZ systems is the Y SZ-YX scali…
A New Code for Nonlinear Force-free Field Extrapolation of the Global Corona
Feng, Xueshang; Jiang, Chaowei; Xiang, Changqing
Reliable measurements of the solar magnetic field are still restricted to the photosphere, and our present knowledge of the three-dimensional coronal magnetic field is largely based on extrapolations from photospheric magnetograms using physical models, e.g., the nonlinear force-free field (NLFFF) model that is usually adopted. Most of the current…
V900 Mon and Thommes' Nebula: A New FUor in Monoceros
Reipurth, Bo; Aspin, Colin; Herbig, G. H.
Detailed observations of a recently recognized eruptive variable, V900 Mon, are presented. The star is located in the small cloud L1656, a little-studied region of modest star formation activity in Monoceros, and is presently at a magnitude of r ~ 16, surrounded by a bright compact reflection nebula, where only a 20th magnitude star was seen on th…
Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk around HD 32297
Currie, Thayne; Debes, John; Robitaille, Thomas +8 more
We present Keck/NIRC2 Ks -band high-contrast coronagraphic imaging of the luminous debris disk around the nearby, young A star HD 32297 resolved at a projected separation of r = 0farcs3-2farcs5 (≈35-280 AU). The disk is highly warped to the north and exhibits a complex, "wavy" surface brightness (SB) profile interior to r ≈ 110 AU, wher…
High-resolution X-Ray Spectroscopy Reveals the Special Nature of Wolf-Rayet Star Winds
Hamann, W. -R.; Oskinova, L. M.; Ignace, R. +3 more
We present the first high-resolution X-ray spectrum of a putatively single Wolf-Rayet (WR) star. 400 ks observations of WR 6 by the XMM-Newton telescope resulted in a superb quality high-resolution X-ray spectrum. Spectral analysis reveals that the X-rays originate far out in the stellar wind, more than 30 stellar radii from the photosphere, and t…
The Nature of the Bright ULX X-2 in NGC 3921: A Chandra Position and HST Candidate Counterpart
Fabian, A. C.; Miniutti, G.; Miller-Jones, J. C. A. +6 more
We report on Chandra observations of the bright ultraluminous X-ray (ULX) source in NGC 3921. Previous XMM-Newton observations reported in the literature show the presence of a bright ULX at a 0.5-10 keV luminosity of 2 × 1040 erg s-1. Our Chandra observation finds the source at a lower luminosity of ≈8 × 1039 erg …
Determination of the Heliospheric Radial Magnetic Field from the Standoff Distance of a CME-driven Shock Observed by the STEREO Spacecraft
Gopalswamy, Nat; Yashiro, Seiji; Kwon, Ryun-Young +2 more
We report on the determination of radial magnetic field strength in the heliocentric distance range from 6 to 120 solar radii (R ⊙) using data from Coronagraph 2 (COR2) and Heliospheric Imager I (HI1) instruments on board the Solar Terrestrial Relations Observatory spacecraft following the standoff-distance method of Gopalswamy & Ya…
Discovery of a Kiloparsec-scale X-Ray/Radio Jet in the z = 4.72 Quasar GB 1428+4217
Cheung, C. C.; Stawarz, Ł.; Siemiginowska, A. +4 more
We report the discovery of a one-sided 3farcs6 (24 kpc, projected) long jet in the high-redshift, z = 4.72, quasar GB 1428+4217 in new Chandra X-ray and Very Large Array (VLA) radio observations. This is the highest redshift kiloparsec-scale X-ray/radio jet known. Analysis of archival very long baseline interferometry 2.3 and 8.6 GHz data reveal a…
A Search for an Intermediate-mass Black Hole in the Core of the Globular Cluster NGC 6266
Harrison, Thomas E.; Baumgardt, Holger; McNamara, Bernard J. +1 more
It has long been thought that intermediate-mass black holes (IMBHs) might be located in the cores of globular clusters. However, studies attempting to confirm this possibility have been inconclusive. To refine the search for these objects, Baumgardt et al. completed a series of N-body simulations to determine the observational properties that a ho…