Related papers: Chandra grating spectroscopy of three hot white dw…
Recent studies of the stellar population in the solar neighborhood (<20 pc) suggest that there are undetected white dwarfs (WDs) in multiple systems with main sequence companions. Detecting these hidden stars and obtaining a more complete…
Nova SMC 2016 has been the most luminous nova known in the direction of the Magellanic Clouds. It turned into a very luminous supersoft X-ray source between day 16 and 28 after the optical maximum. We observed it with Chandra, the HRC-S…
We present CHANDRA X-ray data of the nearby Magellanic Irregular dwarf starburst galaxy NGC4449. Contributions to the X-ray emission come from discrete point sources and extended diffuse emission. The extended emission has a complex…
We present spectroscopic observations confirming the identification of hot white dwarfs among UV-bright sources from the Sandage Two-color Survey of the Galactic plane and listed in the Lanning (Lan) catalog of such sources. A subsample of…
Super Soft X-ray Sources (SSS) are powered by nuclear burning on the surface of an accreting white dwarf, they are seen around 0.1-1 keV (thus in the soft X-ray regime), depending on effective temperature and the amount of intervening…
We report the identification, in an Extreme Ultraviolet Explorer (EUVE) spectrum, of a hot white dwarf companion to the 3rd magnitude late-B star Theta Hya (HR3665, HD79469). This is the second B star + white dwarf binary to be conclusively…
Hot, compact, hydrogen-deficient pre-white dwarfs (pre-WDs) with effective temperatures of Teff > 70,000 K and a surface gravity of 5.0 < log g < 7.0 are rather rare objects despite recent and ongoing surveys. It is believed that they are…
The relatively high abundance of carbon in the hot DO white dwarf RE0503-289 indicates that it is a descendant of a PG1159 star. This is corroborated by the recent detection of the extremely high abundances of trans-Fe elements which stem…
We present some early results on AGN from the Chandra X-ray Observatory, highlighting high resolution spectroscopy using the High Energy Transmission Grating Spectrometer (HETGS). The quasar PKS 0637-752 was found to have a very bright…
We present a method for measuring the physical parameters of the coldest T-type brown dwarfs using low resolution near infrared spectra. By comparing H_2O- and H_2-sensitive spectral ratios between empirical data and theoretical atmosphere…
As they evolve, white dwarfs undergo major changes in surface composition, a phenomenon known as spectral evolution. In particular, some stars enter the cooling sequence with helium atmospheres (type DO) but eventually develop hydrogen…
The X-ray emission from most accreting white dwarfs (WDs) in symbiotic binary stars is quite soft. Several symbiotic WDs, however, produce strong X-ray emission at energies greater than ~20 keV. The Swift BAT instrument has detected hard…
For a long time, no hydrogen-deficient white dwarfs have been known that have effective temperature between 30 kK and < 45 kK, i.e. exceeding those of DB white dwarfs and having lower ones than DO white dwarfs. Therefore, this temperature…
We review the X-ray observations of hot subdwarf stars. While no X-ray emission has been detected yet from binaries containing B-type subdwarfs, interesting results have been obtained in the case of the two luminous O-type subdwarfs HD…
PG0948+534 is currently one of the hottest DA white dwarf stars, and is also one of the most mysterious. Attempts to model the sharp, deep absorption features of this star have been unsuccessful. In these proceedings we describe our…
Brown dwarfs are compact objects that do not reach temperatures high enough to produce sustained hydrogen fusion. Consequently, they cool over time, gradually evolving through later spectral types. In fact, three new spectral types (L, T,…
Low mass white dwarfs are the remnants of disrupted red giant stars in binary millisecond pulsars and other exotic binary star systems. Some low mass white dwarfs cool rapidly, while others stay bright for millions of years due to stable…
H1504+65 is a young white dwarf with an effective temperature of 200,000 K and is the hottest post-AGB star ever analysed with detailed model atmospheres. Chandra LETG+HRC-S spectra have revealed the richest X-ray absorption line spectrum…
We present an analysis of all single white dwarf stars known to exhibit spectroscopic signatures of neutral helium line splitting due to the presence of a strong magnetic field. Using state-of-the-art models taking into account the effects…
We report on variations in important X-ray emission lines in a series of Chandra grating spectra of the supermassive colliding wind binary star Eta Carinae, including key phases around the X-ray minimum/periastron passage in 2003.5. The…