Search Publications
O-star mass-loss and wind momentum rates in the Galaxy and the Magellanic Clouds Observations and theoretical predictions.
Lennon, D. J.; Herrero, A.; Pauldrach, A. W. A. +8 more
A new, very fast approximate method is presented to determine mass-loss rates of O-stars from Halpha_ line profiles. The method uses H and HeII departure coefficients from unified model atmospheres parametrized in a simple way as function of wind velocity together with photospheric NLTE line profiles as the inner boundary condition for …
The Sombrero galaxy. II. Colours, kinematics and line strengths of the central region.
Emsellem, E.; Bacon, R.; Monnet, G. +1 more
We present photometric (pre-COSTAR HST and ground-based) and new two-dimensional TIGER spectrographic data of the central region of the Sombrero galaxy (NGC 4594, M 104). This gives B-V and V-R_C_ images, as well as 2D line strengths and kinematical maps (LOSVDs). Analysis of these data lets us draw a clearer picture of the morphology of the Sombr…
The mass distribution of CL0939+4713 obtained from a `weak' lensing analysis of a WFPC2 image.
Kneib, J. -P.; Schneider, P.; Seitz, S. +1 more
The image distortions of high-redshift galaxies caused by gravitational light deflection of foreground clusters of galaxies can be used to reconstruct the two-dimensional surface mass density of these clusters. We apply an unbiased parameter-free reconstruction technique to the cluster CL0939+4713 (Abell 851), observed with the WFPC2 on board of t…
The interstellar D/H ratio toward G191-B2B from GHRS observations.
Ferlet, R.; Vidal-Madjar, A.; Lallement, R. +3 more
We have observed the DA white dwarf G191-B2B using HST-GHRS to measure the interstellar D/H ratio. In order to derive an accurate structure of the line of sight, we have observed and analysed using a profile fitting procedure the interstellar lines of MgII (2800. and FeII (2344. high resolution using the Echelle B grating, and SiII (1190... (1206.…
High resolution UV spectroscopy of two hot (pre-) white dwarfs with the Hubble Space Telescope. KPD0005+5106 and RXJ2117+3412.
Rauch, T.; Werner, K.; Dreizler, S. +4 more
High resolution UV spectra of KPD0005+5106 and RXJ2117+3412 have been obtained with the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope. The data were subject to a non-LTE model atmosphere analysis. For KPD0005+5106, the hottest known helium-rich white dwarf, the C and N abundances as well as an upper limit for O have been d…
Star formation history of the POST starburst galaxy NGC 1569.
Bomans, D. J.; Vallenari, A.
We discuss the star formation history in the post-starburst galaxy NGC 1569 using colour-magnitude diagrams derived from HST WPFC images in the F555W and F785LP filters. This galaxy has experienced a global burst of star formation from 1x10^8^yr to about 4Myr ago. Evidence has been found of older episodes of star formation from 1.5Gyr to 1.5x10^8^…
HST and groundbased observations of the `Hubble-Sandage' variables in M 31 and M 33.
Stahl, O.; Davidson, K.; Humphreys, R. M. +4 more
The small group of peculiar stars known as the Hubble-Sandage variables in M 31 and M 33 belong to the class of stars we now call the Luminous Blue Variables - highly unstable, evolved massive stars found in many spiral and irregular galaxies. We have used the Hubble Space Telescope to obtain UV imaging and spectroscopy of several of the LBVs in M…
PU Vulpeculae: an eclipsing symbiotic nova.
Vogel, M.; Nussbaumer, H.
A series of IUE observation from 1992 to 1995 has definitely established PU Vul as an eclipsing binary. The outburst of this symbiotic nova began in 1977. An extended fading in 1980 gave rise to various interpretations, the eclipse scenario being one of them, dust formation being another. From AFOEV and AAVSO observations we find a period of 4900+…
CIV absorption from hot gas inside the supergiant shell LMC4 observed with HST and IUE.
Bomans, D. J.; de Boer, K. S.; Grebel, E. K. +1 more
High resolution ultraviolet spectra obtained with the HST-GHRS of two stars in the direction of the supergiant shell LMC4 unambiguously show absorption by substantial quantities of CIV gas at velocities near the the systemic velocity of the LMC. In combination with the detection of diffuse X-rays from the LMC4 by ROSAT and other supporting data, t…
A damped Lyα candidate at z~0.1 towards Q0439-433.
Petitjean, P.; Smette, A.; Theodore, B. +1 more
We report on the detection of a Z_gal_=0.101 galaxy projected on the sky at 4.2arcsec (or 5.2h^-1^_100_kpc for q_0_=0.5) from the quasar Q 0439-433 (z_em_=0.594). The HST spectrum of the quasar shows strong Mg II, Fe II, Si II, Al II and C IV absorption lines at the same redshift as the galaxy. The equivalent width ratios of the low ionization lin…