Related papers: Turning cool star X-ray spectra upside down
We observed Circinus X-1 twice during a newly reached low-flux phase near zero orbital phase using the High-Energy Transmission Grating Spectrometer (HETGS) onboard Chandra. In both observations the source did not show the P Cygni lines we…
For the first time, we have identified NeVIII absorption lines in far-UV spectra of the hottest known (Teff>150,000 K) hydrogen-deficient (pre-) white dwarfs of spectral type PG1159. They are of photospheric origin and can be matched by…
We present new cooling sequences, color-magnitude diagrams, and color-color diagrams for cool white dwarfs with pure hydrogen atmospheres down to an effective temperature $\te=1500$ K. We include a more detailed treatment of the physics of…
We report the first discovery of argon in hot evolved stars and white dwarfs. We have identified the ArVII 1063.55A line in some of the hottest known (Teff=95000-110000 K) central stars of planetary nebulae and (pre-) white dwarfs of…
Hot methane is found in many "cool" sub-stellar astronomical sources including brown dwarfs and exoplanets, as well as in combustion environments on Earth. We report on the first high-resolution laboratory absorption spectra of hot methane…
The Chandra / LETG spectrum of SS Cyg in outburst shows broad (\approx 5 A) spectral features that have been interpreted as a large number of absorption lines on a blackbody continuum with a temperature of 250 kK (Mauche 2004). It is most…
We present a detailed analysis of all the known Hot DQ white dwarfs in the Fourth Data Release of the Sloan Digital Sky Survey (SDSS) recently found to have carbon dominated atmospheres. Our spectroscopic and photometric analysis reveals…
A detailed analysis of the very cool white dwarfs SDSS 1337+00 and LHS 3250 is presented. Model atmosphere calculations with improved collision-induced absorptions by molecular hydrogen indicate that a pure hydrogen composition can be ruled…
We have performed soft X-ray spectroscopy of two hot white dwarfs with the Chandra observatory using the Low Energy Transmission Grating. The first target is the hot DA white dwarf LB1919 (Teff=69000 K). This star is representative of a…
We present X-ray spectral analysis of the accreting young star TW Hydrae from a 489 ks observation using the Chandra High Energy Transmission Grating. The spectrum provides a rich set of diagnostics for electron temperature T_e, electron…
We present a series of systematic abundance measurements for 89 hot DA white dwarfs drawn from the FUSE observation archive. These stars span the temperature range ~ 20000-70000K, and form the largest sample to-date, exceeding our earlier…
Cool core clusters of galaxies require strong feedback from their central AGN to offset cooling. We present a study of strong cool core, highly-luminous (most with L_x > 10^(45) erg/s), clusters of galaxies in which the mean central AGN jet…
Cool white dwarfs with Teff < 6000 K are the remnants of the oldest stars that existed in our Galaxy. Their atmospheres, when properly characterized, can provide valuable information on white dwarf evolution and ultimately star formation…
We present $Spitzer$ IRS 5--14 $\mu$m spectra and 16 $\mu$m and 22 $\mu$m photometry of the T2.5 companion to the $\sim$300 Myr-old G0V star HN Peg. We incorporate previous 0.8--5 $\mu$m observations to obtain the most comprehensive…
High-resolution soft X-ray spectroscopic observations of single hot white dwarfs are scarce. With the Chandra Low-Energy Transmission Grating, we have observed two white dwarfs, one is of spectral type DA (LB 1919) and the other is a non-DA…
We investigate an archival XMM-Newton observation of LHS 2065, an ultracool dwarf with spectral type M9. We clearly detect LHS 2065 at soft X-ray energies in less than 1 h effective exposure time above the 3 sigma level with the PN and MOS1…
The Chandra X-ray Observatory grating spectrometers allow study of stellar spectra at resolutions on the order of 1000. Prior x-ray observatories' low resolution data have shown that nearly all classes of stars emit x-rays. Chandra reveals…
(abridged) We present an analysis of Chandra X-ray observations of a sample of eight dwarf starburst galaxies (I Zw 18, VII Zw 403, NGC 1569, NGC 3077, NGC 4214, NGC 4449, NGC 5253, and He 2-10). Extended, diffuse X-ray emission is detected…
(abridged) Non-degenerate stars of essentially all spectral classes are soft X-ray sources. Low-mass stars on the cooler part of the main sequence and their pre-main sequence predecessors define the dominant stellar population in the galaxy…
We report observations with the Chandra X-ray Observatory of the single, cool, magnetic white dwarf GD 356. For consistent comparison with other X-ray observations of single white dwarfs, we also re-analyzed archival ROSAT data for GD 356…