Search Publications
A Multisite Campaign to Measure Solar-like Oscillations in Procyon. I. Observations, Data Reduction, and Slow Variations
Reffert, Sabine; Butler, R. Paul; Bertaux, Jean-Loup +45 more
We have carried out a multisite campaign to measure oscillations in the F5 star Procyon A. We obtained high-precision velocity observations over more than three weeks with 11 telescopes, with almost continuous coverage for the central 10 days. This represents the most extensive campaign so far organized on any solar-type oscillator. We describe in…
X-Ray and Optical Microlensing in the Lensed Quasar PG 1115+080
Morgan, Nicholas D.; Dai, Xinyu; Morgan, Christopher W. +2 more
We analyzed the microlensing of the X-ray and optical emission of the lensed quasar PG 1115+080. We find that the effective radius of the X-ray emission is 1.3+ 1.1-0.5 dex smaller than that of the optical emission. Viewed as a thin disk observed at inclination angle i, the optical accretion disk has a scale length, defined b…
The X-Ray Spectral Evolution in X-Ray Binaries and Its Application to Constrain the Black Hole Mass of Ultraluminous X-Ray Sources
Wu, Qingwen; Gu, Minfeng
We investigate the relationship between the hard X-ray photon index Γ and the Eddington ratio [ξ = LX(0.5-25 keV)/LEdd] in six X-ray binaries (XRBs) with well-constrained black hole masses and distances. We find that different XRBs follow different anticorrelations between Γ and ξ when ξ is less than a critical value, while Γ…
Double Coronal Hard and Soft X-Ray Source Observed by RHESSI: Evidence for Magnetic Reconnection and Particle Acceleration in Solar Flares
Liu, Wei; Dennis, Brian R.; Jiang, Yan Wei +1 more
We present data analysis and interpretation of an M1.4 class flare observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) on 2002 April 30. This event, with its footpoints occulted by the solar limb, exhibits a rarely observed, but theoretically expected, double-source structure in the corona. The two coronal sources, obse…
The Recent Star Formation Histories of M81 Group Dwarf Irregular Galaxies
Cannon, John M.; Dolphin, Andrew E.; Skillman, Evan D. +4 more
We present observations and analysis of nine dwarf irregular galaxies (dIs) in the M81 Group taken with the Advanced Camera for Surveys aboard the Hubble Space Telescope. The nine galaxies (the Garland, M81 Dwarf A, DDO 53, Ho IX, Ho I, DDO 165, NGC 2366, Ho II, and IC 2574) span 6 mag in luminosity, a factor of 1000 in current star formation rate…
Extrasolar Giant Planets and X-Ray Activity
Drake, Jeremy J.; Kashyap, Vinay L.; Saar, Steven H.
We have carried out a survey of X-ray emission from stars with giant planets, combining both archival and targeted surveys. Over 230 stars have been currently identified as possessing planets, and roughly one-third of these have been detected in X-rays. We carry out detailed statistical analysis on a volume-limited sample of main-sequence star sys…
Multiwavelength Observations of the Powerful Gamma-Ray Quasar PKS 1510-089: Clues on the Jet Composition
Kataoka, J.; Kawai, N.; Tosti, G. +16 more
We present the results from a multiwavelength campaign conducted in 2006 August of the powerful γ-ray quasar PKS 1510-089 (z = 0.361). This campaign commenced with a deep Suzaku observation lasting 3 days for a total exposure time of 120 ks and continued with Swift monitoring over 18 days. Besides Swift observations, the campaign included ground-b…
The Physical Scale of the Far-Infrared Emission in the Most Luminous Submillimeter Galaxies
Wilner, David J.; Yun, Min S.; Fazio, Giovanni G. +10 more
We present high-resolution submillimeter interferometric imaging of two of the brightest high-redshift submillimeter galaxies known: GN 20 and AzTEC1 at 0.8'' and 0.3'' resolution, respectively. Our data—the highest resolution submillimeter imaging of high-redshift sources accomplished to date—were collected in three different array configurations…
Discovery of a Very Bright Strongly Lensed Galaxy Candidate at z ≈ 7.6
Ford, H. C.; Frye, B. L.; Infante, L. +11 more
Using Hubble Space Telescope (HST) and Spitzer IRAC imaging, we report the discovery of a very bright strongly lensed Lyman break galaxy (LBG) candidate at z ~ 7.6 in the field of the massive galaxy cluster Abell 1689 (z = 0.18). The galaxy candidate, which we refer to as A1689-zD1, shows a strong z850 - J110 break of at leas…
A Massive Neutron Star in the Globular Cluster M5
Freire, Paulo C. C.; Hessels, Jason W. T.; van den Berg, Maureen +1 more
We report the results of 19 years of Arecibo timing for two pulsars in the globular cluster NGC 5904 (M5), PSR B1516+02A (M5A) and PSR B1516+02B (M5B). This has resulted in the measurement of the proper motions of these pulsars and, by extension, that of the cluster itself. M5B is a 7.95 ms pulsar in a binary system with a >0.13 M⊙ c…