Search Publications
Stellar Populations in the Outer Reaches of M31 and M32 from WFPC2 Photometry
Mateo, Mario; Alonso-García, Javier; Worthey, Guy +1 more
Hubble Space Telescope Wide Field Planetary Camera 2 photometry in a field 7 effective radii from the nucleus of M32 and a comparison field in the outer disk of M31, already examined for the presence of RR Lyrae variable stars, are further compared. No relative distance difference between the two fields could be measured using the luminosity of re…
Composite Accretion Disk and White Dwarf Photosphere Analyses of the FUSE and Hubble Space Telescope Observations of EY Cygni
Sion, Edward M.; Orio, M.; Gänsicke, Boris T. +4 more
We explore the origin of FUSE and Hubble Space Telescope STIS far-UV spectra of the dwarf nova EY Cygni during its quiescence using combined high-gravity photosphere and accretion disk models, as well as model accretion belts. The best-fitting single-temperature white dwarf model to the FUSE plus STIS spectrum of EY Cyg has Teff=24,000 …
Shock wave driven by an expanding system of loops
Solanki, S. K.; Mierla, M.; Inhester, B. +5 more
We report on a Coronal Mass Ejection (CME) observed on June 27, 1999 by the UltraViolet Coronagraph Spectrometer (UVCS) telescope operating on board the SOHO spacecraft. The CME was also observed by the Large Angle Spectroscopic Coronagraph (LASCO). Emission of hot material has been recorded by UVCS propagating in front of an opening system of loo…
Kinematics and Parameters of the Gas in the Vicinity of TW Hya
Lamzin, S. A.; Kravtsova, A. S.; Romanova, M. M. +1 more
The following conclusions about the kinematics and parameters of the gas in the vicinity of TW Hya have been drawn from an analysis of optical and ultraviolet line profiles and intensities. The accreting matter rises in the magnetosphere to a distance z>R* above the disk plane and falls to the star near its equator almost perpendicul…
Observations of Nonthermal and Thermal Hard X-Ray Spikes in an M-Class Flare
Qiu, Jiong; Wang, Haimin; Ji, Haisheng +2 more
We report a study of an M2.3 flare, which occurred on 2002 September 9 in NOAA Active Region 0105. The observation was made at Big Bear Solar Observatory (BBSO) at the wavelength of Hα-1.3 Å, with a cadence of 40 ms. The flare was also observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Three kernels appear in Hα-1.3 Å i…
Time-resolved photometry and spectroscopy of the new deeply-eclipsing SW Sextantis star HS 0728+6738
Gänsicke, B. T.; Hagen, H. -J.; Engels, D. +2 more
We present time-resolved optical spectroscopy and photometry, and far-ultraviolet spectroscopy of
X-ray spectroscopy of the W UMa-type binary 44 Bootis
Gondoin, P.
44 Boo B, a W UMa-type binary system, was observed in June 2001 during one entire revolution period with the XMM-Newton observatory. The count rate in the 0.3 to 2 keV band is constant in average with 5 to 20% count rate increases reminiscent of flares. Spectral fitting of the EPIC spectra indicates a corona configuration with little contribution …
XMM-Newton observations of the two X-ray weak quasars PG 1411+442 and Mrk 304
Papadakis, I. E.; Brinkmann, W.; Ferrero, E.
We present the results of XMM-Newton observations of two X-ray weak quasars, PG 1411+442 and Mrk 304. In both cases the spectra can basically be represented by hard power laws with photon indices typical for radio-quiet quasars, heavily intrinsically absorbed by column densities of ∼2×1023 cm-2 in PG 1411+442 and ∼4×1022…
Statistical comparison of transition region blinkers and explosive events
Peter, H.; Brković, A.
Explosive events and blinkers are two observational classes of transients seen on the quiet Sun and an investigation of the significance of and relationship between such events may be critical for understanding basic processes at work in the solar atmosphere. We analysed five time-series spectra of the quiet Sun of transition region O XV 629 Å, O …
Accommodating electric propulsion on SMART-1
Rathsman, Peter; Kugelberg, Joakim; Bodin, Per +1 more
This paper focuses on the technical challenges that arise when electric propulsion is used on a small spacecraft such as SMART-1. The choice of electric propulsion influences not only the attitude control system and the power system, but also the thermal control as well as the spacecraft structure. A description is given on how the design of the a…