Search Publications
Progressive Star Formation in the Young Galactic Super Star Cluster NGC 3603
McCarthy, Patrick J.; Calzetti, Daniela; Whitmore, Bradley C. +22 more
Early Release Science observations of the cluster NGC 3603 with the WFC3 on the refurbished Hubble Space Telescope allow us to study its recent star formation history. Our analysis focuses on stars with Hα excess emission, a robust indicator of their pre-main sequence (PMS) accreting status. The comparison with theoretical PMS isochrones shows tha…
Low-Latitude Coronal Holes at the Minimum of the 23rd Solar Cycle
Yurchyshyn, Vasyl; Abramenko, Valentyna; Lee, Christina O. +3 more
Low- and mid-latitude coronal holes (CHs) observed on the Sun during the current solar activity minimum (from 2006 September 21, Carrington rotation (CR) 2048, to 2009 June 26, CR 2084) were analyzed using Solar and Heliospheric Observatory/Extreme ultraviolet Imaging Telescope and STEREO-A SECCHI EUVI data. From both the observations and Potentia…
Superdense Massive Galaxies in the ESO Distant Cluster Survey (EDisCS)
Fritz, J.; Moretti, A.; Vulcani, B. +9 more
We find a significant number of massive and compact galaxies in clusters from the ESO Distant Clusters Survey (EDisCS) at 0.4 < z < 1. They have similar stellar masses, ages, sizes, and axial ratios to local z ~ 0.04 compact galaxies in WIde field Nearby Galaxy clusters Survey (WINGS) clusters, and to z = 1.4-2 massive and passive galaxies f…
Implications of a High Angular Resolution Image of the Sunyaev-Zel'Dovich Effect in RXJ1347-1145
Ade, P.; Aguirre, J. E.; Devlin, M. J. +11 more
The most X-ray luminous cluster known, RXJ1347-1145 (z = 0.45), has been the object of extensive study across the electromagnetic spectrum. We have imaged the Sunyaev-Zel'dovich effect (SZE) at 90 GHz (λ = 3.3 mm) in RXJ1347-1145 at 10'' resolution with the 64 pixel MUSTANG bolometer array on the Green Bank Telescope, confirming a previously repor…
Quiescent X-ray Emission From Cen X-4: A Variable Thermal Component
Miller, Jon M.; Cackett, Edward M.; Wijnands, Rudy +1 more
The nearby neutron star low-mass X-ray binary, Cen X-4, has been in a quiescent state since its last outburst in 1979. Typically, quiescent emission from these objects consists of thermal emission (presumably from the neutron star surface) with an additional hard power-law tail of unknown nature. Variability has been observed during quiescence in …
The Sudden Death of the Nearest Quasar
Schawinski, Kevin; Józsa, Gyula I. G.; Keel, William C. +13 more
Galaxy formation is significantly modulated by energy output from supermassive black holes at the centers of galaxies which grow in highly efficient luminous quasar phases. The timescale on which black holes transition into and out of such phases is, however, unknown. We present the first measurement of the shutdown timescale for an individual qua…
Recent X-ray Variability of η Carinae: The Quick Road to Recovery
Corcoran, M. F.; Owocki, S. P.; Russell, C. M. P. +4 more
We report continued monitoring of the superluminous binary system η Car by the Proportional Counter Array on the Rossi X-ray Timing Observatory (RXTE) through the 2009 X-ray minimum. The RXTE campaign shows that the minimum began on 2009 January 16, consistent with the phasings of the two previous minima, and overall, the temporal behavior of the …
New Insights into the Problem of the Surface Gravity Distribution of Cool DA White Dwarfs
Tremblay, P. -E.; Bergeron, P.; Kalirai, J. S. +1 more
We review at length the longstanding problem in the spectroscopic analysis of cool hydrogen-line (DA) white dwarfs (T eff< 13,000 K) where gravities are significantly higher than those found in hotter DA stars. The first solution that has been proposed for this problem is a mild and systematic helium contamination from convective mix…
The Origin of the Hot Gas in the Galactic Halo: Confronting Models with XMM-Newton Observations
Henley, David B.; Shelton, Robin L.; Mac Low, Mordecai-Mark +2 more
We compare the predictions of three physical models for the origin of the hot halo gas with the observed halo X-ray emission, derived from 26 high-latitude XMM-Newton observations of the soft X-ray background between l = 120° and l = 240°. These observations were chosen from a much larger set of observations as they are expected to be the least co…
Evidence for Steady Heating: Observations of an Active Region Core with Hinode and TRACE
Winebarger, Amy R.; Warren, Harry P.; Brooks, David H.
The timescale for energy release is an important parameter for constraining the coronal heating mechanism. Observations of "warm" coronal loops (~1 MK) have indicated that the heating is impulsive and that coronal plasma is far from equilibrium. In contrast, observations at higher temperatures (~3 MK) have generally been consistent with steady hea…