Search Publications
The Dynamical State of the Globular Cluster M10 (NGC 6254)
Dalessandro, E.; Trenti, M.; Beccari, G. +3 more
Studying the radial variation of the stellar mass function (MF) in globular clusters (GCs) has proved a valuable tool to explore the collisional dynamics leading to mass segregation and core collapse. Recently, Pasquato et al. (2009) used the mass segregation profile to investigate the presence of an intermediate-mass black hole (IMBH) in NGC 2298…
AEGIS: A Multiwavelength Study of Spitzer Power-law Galaxies
Barmby, P.; Ivison, R. J.; Georgakakis, A. +8 more
This paper analyzes a sample of 489 Spitzer/Infrared Array Camera (IRAC) sources in the Extended Groth Strip (EGS), whose spectral energy distributions fit a red power law (PL) from 3.6 to 8.0 µm. The median redshift for sources with known redshifts is langzrang = 1.6. Though all or nearly all of the sample galaxies are likely to be active g…
First Earth-based Detection of a Superbolide on Jupiter
Djorgovski, S. G.; Hueso, R.; Sánchez-Lavega, A. +14 more
Cosmic collisions on planets cause detectable optical flashes that range from terrestrial shooting stars to bright fireballs. On 2010 June 3 a bolide in Jupiter's atmosphere was simultaneously observed from the Earth by two amateur astronomers observing Jupiter in red and blue wavelengths. The bolide appeared as a flash of 2 s duration in video re…
RR Lyrae Variables in M33. II. Oosterhoff Properties and Radial Trends
Yang, S. -C.; Sarajedini, Ata; Holtzman, Jon A. +1 more
We present the results of an extensive survey of RR Lyrae (RRL) stars in three fields along the major axis of the Triangulum Galaxy (M33). From images taken with the Advanced Camera for Surveys (ACS) Wide Field Channel on board the Hubble Space Telescope through two passbands (F606W and F814W), we have identified and characterized a total of 119 R…
On the Nature of the Compact Object in SS 433: Observational Evidence of X-ray Photon Index Saturation
Titarchuk, Lev; Seifina, Elena
We present an analysis of the X-ray spectral properties observed from the black hole candidate (BHC) binary SS 433. We have analyzed Rossi X-ray Timing Explorer data from this source, coordinated with Green Bank Interferometer/RATAN-600. We show that SS 433 undergoes an X-ray spectral transition from the low hard state to the intermediate state (I…
Tadpole Galaxies in the Hubble Ultra Deep Field
Elmegreen, Bruce G.; Elmegreen, Debra Meloy
Tadpole galaxies have a head-tail shape with a large clump of star formation at the head and a diffuse tail or streak of stars off to one side. We measured the head and tail masses, ages, surface brightnesses, and sizes for 66 tadpoles in the Hubble Ultra Deep Field (UDF) and looked at the distribution of neighbor densities and tadpole orientation…
The Anomalous Accretion Disk of the Cataclysmic Variable RW Sextantis
Szkody, Paula; Sion, Edward M.; Godon, Patrick +2 more
Synthetic spectra covering the wavelength range 900-3000 Å provide an accurate fit, established by a χ2 ν analysis, to a combined observed spectrum of RW Sextantis. Two separately calibrated distances to the system establish the synthetic spectrum comparison on an absolute flux basis but with two alternative scaling factors, …
Spin-Down of the Long-Period Accreting Pulsar 4U 2206+54
Patel, Sandeep K.; Finger, Mark H.; Wilson-Hodge, Colleen A. +1 more
4U 2206+54 is a high-mass X-ray binary which has been suspected to contain a neutron star accreting from the wind of its companion, BD +53° 2790. Reig et al. have recently detected 5560 s period pulsations in both Rossi X-ray Timing Explorer (RXTE) and International Gamma-ray Astrophysics Laboratory observations which they conclude are due to the …
The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer. II. Evidence for High Luminosity in Holmberg II ULX
Kallman, T. R.; Weaver, K. A.; Berghea, C. T. +1 more
This is the second of two papers examining Spitzer Infrared Spectrograph observations of the ultraluminous X-ray source (ULX) in Holmberg II. Here, we perform detailed photoionization modeling of the infrared lines. Our analysis suggests that the luminosity and morphology of the [O IV] 25.89 µm emission line is consistent with photoionizatio…
The Advanced Camera for Surveys Nearby Galaxy Survey Treasury. IV. The Star Formation History of NGC 2976
Williams, Benjamin F.; Gilbert, Karoline M.; Dolphin, Andrew +8 more
We present resolved stellar photometry of NGC 2976 obtained with the Advanced Camera for Surveys (ACS) as part of the ACS Nearby Galaxy Survey Treasury (ANGST) program. The data cover the radial extent of the major axis of the disk out to 6 kpc, or ~6 scale lengths. The outer disk was imaged to a depth of M F606W ~ 1, and an inner field…