Search Publications
A precise HST parallax of the cataclysmic variable EX Hydrae, its system parameters, and accretion rate
Gänsicke, B. T.; Beuermann, K.; McArthur, B. E. +2 more
Using the HST Fine Guidance Sensor, we have measured a high precision astrometric parallax of the cataclysmic variable EX Hydrae, π=15.50 +/- 0.29 mas. From the wavelength-integrated accretion-induced energy flux, we derive a quiescent accretion luminosity for EX Hya of Lacc =(2.6+/- 0.6)× 1032 erg s-1. The quiesce…
Ultraviolet and Optical Properties of Narrow-Line Seyfert 1 Galaxies
Shields, Joseph C.; Constantin, Anca
Narrow-line Seyfert 1 galaxies (NLS1s) are remarkable for their extreme continuum and emission-line properties, which are not well understood. New results bearing on the spectroscopic characteristics of these objects are presented here, with the aim of establishing their typical UV and optical spectral behavior. We employ Hubble Space Telescope ob…
The Tully-Fisher relation of cluster spirals at z= 0.83
Aragón-Salamanca, Alfonso; Hjorth, Jens; Milvang-Jensen, Bo +2 more
We present the rest-frame B-band Tully-Fisher relation for a sample of 8 cluster spiral galaxies at z= 0.83 and 19 field spirals at z= 0.15-0.90 based on Very Large Telescope (VLT) spectroscopy and Hubble Space Telescope (HST) photometry. No strong difference is detected between the cluster and the field galaxies, but we find some evidence that th…
Observational Evidence of a Magnetic Flux Rope Eruption Associated with the X3 Flare on 2002 July 15
Zhang, Hongqi; Liu, Yu; Wang, Haimin +2 more
We present the study of an eruption from the low solar atmosphere (photosphere/chromosphere) as seen in Transition Region and Coronal Explorer 1600 Å images and with the Solar and Heliospheric Observatory Michelson Doppler Imager. The eruption reached its maximum at 20:08 UT on 2002 July 15 in the NOAA Active Region 10030 (N19°, W01°), accompanied…
Cassini between Venus and Earth: Detection of interstellar dust
Dikarev, V.; Kempf, S.; Krüger, H. +5 more
We report the successful in situ measurement of interstellar dust particles inside the orbit of the Earth with the Cosmic Dust Analyzer (CDA) on the Cassini spacecraft. The impact ionization subsystem of the CDA is similar to the instruments on Ulysses and Galileo. As the heliocentric velocity and the direction of the interstellar dust flux are we…
On the Origin of the Basal Emission from Stellar Atmospheres: Analysis of Solar C II Lines
Judge, Philip G.; Carlsson, Mats; Stein, Robert F.
Combining a variety of data with radiation hydrodynamic simulations, we examine the heating of the Sun's internetwork chromosphere and the hypothesis that the chromospheric ``basal'' emission arises because of acoustic wave dissipation. We focus on the 2s2p22D-2s22p2Po multiplet of C II near 1…
The Sun and Heliosphere at Solar Maximum
Krupp, N.; Balogh, A.; Geiss, J. +9 more
Recent Ulysses observations from the Sun's equator to the poles reveal fundamental properties of the three-dimensional heliosphere at the maximum in solar activity. The heliospheric magnetic field originates from a magnetic dipole oriented nearly perpendicular to, instead of nearly parallel to, the Sun's rotation axis. Magnetic fields, solar wind,…
XMM-Newton observations of two black hole X-ray transients in quiescence
Motch, C.; McClintock, J. E.; Barret, D. +5 more
We report on XMM-Newton observations of GRO J1655-40 and GRS 1009-45, which are two black hole X-ray transients currently in their quiescent phase. GRO J1655-40 was detected with a 0.5-10 keV luminosity of 5.9 x 1031 erg s-1 with 20% accuracy, taking into account both statistical errors and uncertainty on the distance. This l…
Damped Lyα Gas Metallicities at Redshifts z=0.9-2.0 from Sloan Digital Sky Survey Spectra
Turnshek, David A.; Rao, Sandhya M.; Vanden Berk, Daniel +1 more
Using Sloan Digital Sky Survey early data release spectra, we have identified 370 Mg II absorption systems with Mg II λ2796 rest equivalent widths >=1 Å and redshifts z=0.9-2.2. From our previous and ongoing Hubble Space Telescope UV spectroscopic studies, we estimate that the mean neutral hydrogen column density of a system selected in this ma…
An Extended Burst Tail from SGR 1900+14 with a Thermal X-Ray Spectrum
Hurley, Kevin; Kouveliotou, Chryssa; Göǧüş, Ersin +6 more
The soft gamma repeater SGR 1900+14 entered a new phase of activity in 2001 April initiated by the intermediate flare recorded on April 18. Ten days following this flare, we discovered an abrupt increase in the source flux between consecutive Rossi X-Ray Timing Explorer (RXTE) orbits. This X-ray flux excess decayed over the next several minutes an…