Search Publications
Time-resolved Hubble Space Telescope Spectroscopy of Four Eclipsing Magnetic Cataclysmic Variables
Schmidt, Gary D.; Stockman, H. S.
Time-resolved, multiepoch, Hubble Space Telescope ultraviolet eclipse spectrophotometry is presented for the magnetic cataclysmic variables (MCVs) V1309 Ori, MN Hya, V2301 Oph, and V1432 Aql. Separation of the eclipse light curves into specific wavebands allows the multiple emission components to be distinguished. Accretion-heated photospheric spo…
Optical spectroscopy of X-Mega targets - II. The massive double-lined O-type binary HD 93205
Morel, T.; Rauw, G.; Barbá, R. H. +8 more
A new high-quality set of orbital parameters for the O-type spectroscopic binary HD 93205 has been obtained combining échelle and coudé CCD observations. The radial velocity orbits derived from the Heii λ4686Å (primary component) and Hei λ4471Å (secondary component) absorption lines yield semi-amplitudes of 133+/-2 and 314+/-2kms-1 for …
Differences in the Sun's Radiative Output in Cycles 22 and 23
de Toma, Giuliana; White, Oran R.; Chapman, Gary A. +4 more
Analysis of the current solar cycle 23 shows a greater increase in total solar irradiance (TSI) for the early phase of this cycle than expected from measurements of the total magnetic flux and traditional solar activity indices, which indicate that cycle 23 is weaker than cycle 22. In contrast, space observations of TSI from the Solar and Heliosph…
Sky confusion noise in the far-infrared: Cirrus, galaxies and the cosmic far-infrared background
Juvela, M.; Ábrahám, P.; Lemke, D. +2 more
We examined the sky confusion noise in 40 sky regions by analysing 175 far-infrared (90-200 mu m) maps obtained with ISOPHOT, the photometer on-board the Infrared Space Observatory. For cirrus fields with < B > > 5 MJy sr-1 the formula based on IRAS data (Helou & Beichman \cite{Helou+Beichman_90}) predicts confusion noise v…
Large Magellanic Cloud stellar clusters. I. 21 HST colour magnitude diagrams
Brocato, E.; Di Carlo, E.; Menna, G.
We present WFPC2 photometry of 21 stellar clusters of the Large Magellanic Cloud obtained on images retrieved from the Hubble Space Telescope archive. The derived colour magnitude diagrams (CMDs) are presented and discussed. This database provides a sample of CMDs representing, with reliable statistics, simple stellar populations with a large spre…
Near-Infrared Coronagraphic Imaging of the Circumstellar Disk around TW Hydrae
Barnes, J. W.; Brown, R. H.; Koerner, D. W. +2 more
We present ground-based near-infrared (H-band) imaging of the circumstellar disk around the nearby classical T Tauri star TW Hydrae. The scattered-light image shows a face-on disk with a radius of 4" (corresponding to 225 AU) and a morphology that agrees with recent images from the Hubble Space Telescope and the Very Large Array. The best-fit powe…
An XMM-Newton observation of the extreme narrow-line Seyfert 1 galaxy Mrk 359
O'Brien, P. T.; Reeves, J. N.; Pounds, K. +3 more
We present XMM-Newton observations of Mrk 359, the first narrow-line Seyfert 1 galaxy (NLS1) discovered. Even among NLS1s, Mrk 359 is an extreme case with extraordinarily narrow optical emission lines. The XMM-Newton data show that Mrk 359 has a significant soft X-ray excess which displays only weak absorption and emission features. The (2-10)keV …
Emission profiles of neutral oxygen and sulfur in Io's exospheric corona
Feldman, P. D.; Moos, H. W.; Strobel, D. F. +4 more
Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) observations of Io acquired in 1997 [Roesler et al., 1999] provided the first simultaneous spatially resolved measurements of emission from neutral sulfur and oxygen, the dominant atomic species in Io's exospheric corona. Previous measurements of Io's corona relied primarily …
Linear drift and periodic variations observed in long time series of polar motion
Schuh, H.; Nagel, S.; Seitz, T.
Two long time series were analysed: the C01 series of the International Earth Rotation Service and the pole series obtained by re-analysis of the classical astronomical observations using the HIPPARCOS reference frame. The linear drift of the pole was determined to be 3.31 - 0.05 milliarcseconds/year towards 76.1 - 0.80° west longitude. For the le…
Young star clusters in the Large Magellanic Cloud: NGC 1805 and 1818
Santiago, B. X.; Tanvir, N. R.; Gilmore, G. F. +4 more
We present colour-magnitude diagrams for two rich (~104Msolar) Large Magellanic Cloud star clusters with ages ~107yr, constructed from optical and near-infrared data obtained with the Hubble Space Telescope. These data are part of an HST project to study LMC clusters with a range of ages. In this paper we investiga…