Search Publications
A Variable Ultraluminous X-Ray Source in a Globular Cluster in NGC 4649
Zezas, A.; Luo, B.; Gallagher, J. S. +9 more
We report the discovery of a new ultraluminous X-ray source associated with a globular cluster in the elliptical galaxy NGC 4649. The X-ray source was initially detected with a luminosity below 5 × 1038 erg s-1, but in subsequent observations 7 and 11 years later it had brightened substantially to 2-3 × 1039 erg s<…
Solar Radio Type-I Noise Storm Modulated by Coronal Mass Ejections
Misawa, H.; Shiota, D.; Inoue, S. +6 more
The first coordinated observations of an active region using ground-based radio telescopes and the Solar Terrestrial Relations Observatory (STEREO) satellites from different heliocentric longitudes were performed to study solar radio type-I noise storms. A type-I noise storm was observed between 100 and 300 MHz during a period from 2010 February 6…
Characterizing Io’s Pele, Tvashtar and Pillan plumes: Lessons learned from Hubble
Spencer, John R.; Jessup, Kandis Lea
Hubble Space Telescope/Wide Field and Planetary Camera 2 (HST/WFPC2) images of Io obtained between 1995 and 2007 between 0.24 and 0.42 µm led to the detection of the Pele plume in reflected sunlight in 1995 and 1999; imaging of the Pele plume via absorption of jovian light in 1996 and 1999; detection of the Prometheus-type Pillan plume in re…
XMM-Newton Finds That SAX J1750.8-2900 May Harbor the Hottest, Most Luminous Known Neutron Star
Heinke, C. O.; Chaty, S.; Tomsick, J. A. +6 more
We have performed the first sensitive X-ray observation of the low-mass X-ray binary (LMXB) SAX J1750.8-2900 in quiescence with XMM-Newton. The spectrum was fit to both a classical blackbody model, and a non-magnetized, pure hydrogen neutron star (NS) atmosphere model. A power-law component was added to these models, but we found that it was not r…
WR 38/38a and the ratio of total-to-selective extinction in Carina
Turner, David G.
A reanalysis of the (seemingly very distant) open cluster Shorlin 1, the group of stars associated with WR 38 and WR 38a, is made on the basis of existing UBV and JHKs observations for cluster members. The 2MASS observations, in particular, imply a mean cluster reddening of EB‑V=1.45±0.07 and a distance of 2.94±0.12 kpc. The …
Multiwavelength analysis of the Lyman-α emitting galaxy Haro 2: relation between the diffuse Lyman-α and soft X-ray emissions
Schaerer, D.; Östlin, G.; Hayes, M. +5 more
Context. Lyman-α emission is commonly used as star formation tracer in cosmological studies. Nevertheless, resonant scattering strongly affects the resulting luminosity, leading to variable and unpredictable escape fractions in different objects.
Aims: To understand how the Lyα escape fraction depends on the properties of the star-forming reg…
Clear Detection of Chromospheric Evaporation Upflows with High Spatial/Temporal Resolution by Hinode XRT
Yamamoto, T. T.; Imada, S.; Nitta, S.
We find clear evidence for typical chromospheric evaporation associated with small transient brightenings, using the data from the X-ray Telescope (XRT) onboard Hinode. We found 13 events, each having a pair of evaporation upflows arising almost symmetrically from both foot points of a magnetic loop. These facts strongly support the standard flare…
Ultraviolet Spectroscopy of Rapidly Rotating Solar-Mass Stars: Emission-line Redshifts as a Test of the Solar-Stellar Connection
France, Kevin; Linsky, Jeffrey L.; Ayres, Tom +1 more
We compare high-resolution ultraviolet spectra of the Sun and thirteen solar-mass main-sequence stars with different rotational periods that serve as proxies for their different ages and magnetic field structures. In this, the second paper in the series, we study the dependence of ultraviolet emission-line centroid velocities on stellar rotation p…
Entropy Generation across Earth's Collisionless Bow Shock
Dandouras, I.; Cao, J. B.; Parks, G. K. +9 more
Earth’s bow shock is a collisionless shock wave but entropy has never been directly measured across it. The plasma experiments on Cluster and Double Star measure 3D plasma distributions upstream and downstream of the bow shock allowing calculation of Boltzmann’s entropy function H and his famous H theorem, dH/dt≤0. The collisionless Boltzmann (Vla…
Flows at the Edge of an Active Region: Observation and Interpretation
Vial, J. -C.; Régnier, S.; Buchlin, E. +1 more
Upflows observed at the edges of active regions have been proposed as the source of the slow solar wind. In the particular case of Active Region (AR) 10942, where such an upflow has been already observed, we want to evaluate the part of this upflow that actually remains confined in the magnetic loops that connect AR 10942 to AR 10943. Both active …