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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…
Million-Degree Plasma Pervading the Extended Orion Nebula
Skinner, Stephen L.; Güdel, Manuel; Rebull, Luisa +3 more
Most stars form as members of large associations within dense, very cold (10 to 100 kelvin) molecular clouds. The nearby giant molecular cloud in Orion hosts several thousand stars of ages less than a few million years, many of which are located in or around the famous Orion Nebula, a prominent gas structure illuminated and ionized by a small grou…
Origin of Saturn's aurora: Simultaneous observations by Cassini and the Hubble Space Telescope
Coates, A. J.; Dougherty, M. K.; Nichols, J. D. +9 more
Outer planet auroras have been imaged for more than a decade, yet understanding their physical origin requires simultaneous remote and in situ observations. The first such measurements at Saturn were obtained in January 2007, when the Hubble Space Telescope imaged the ultraviolet aurora, while the Cassini spacecraft crossed field lines connected t…
Quantitative studies of the optical and UV spectra of Galactic early B supergiants. I. Fundamental parameters
Massa, D.; Prinja, R. K.; Searle, S. C. +1 more
Aims: We undertake an optical and ultraviolet spectroscopic analysis of a sample of 20 Galactic B0-B5 supergiants of luminosity classes Ia, Ib, Iab, and II. Fundamental stellar parameters are obtained from optical diagnostics and a critical comparison of the model predictions to observed UV spectral features is made.
Methods: Fundamental param…
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…
The Fermi Gamma-Ray Space Telescope Discovers the Pulsar in the Young Galactic Supernova Remnant CTA 1
Ozaki, M.; Caraveo, P. A.; Orlando, E. +182 more
Energetic young pulsars and expanding blast waves [supernova remnants (SNRs)] are the most visible remains after massive stars, ending their lives, explode in core-collapse supernovae. The Fermi Gamma-Ray Space Telescope has unveiled a radio quiet pulsar located near the center of the compact synchrotron nebula inside the supernova remnant CTA 1. …
Solid tidal friction above a liquid water reservoir as the origin of the south pole hotspot on Enceladus
Sotin, C.; Tobie, G.; Čadek, O.
Earth, Jupiter's moon Io and Saturn's tiny moon Enceladus are the only solid objects in the Solar System to be sufficiently geologically active for their internal heat to be detected by remote sensing. Interestingly, the endogenic activity on Enceladus is only located on a specific region at the south pole, from which jets of water vapor and ice p…