Related papers: Hard X-ray and Infrared Emission from Apparently S…
We report the results of the first X-ray observation of the luminous and helium-rich O-type subdwarf BD+37 442, carried out with the XMM-Newton satellite in August 2011. X-ray emission is detected with a flux of about 3x10^(-14) erg/cm2/s…
We report Spitzer Space Telescope photometry of eleven externally-polluted white dwarfs. Of the nine stars for which we have IRAC photometry, we find that GD 40, GD 133 and PG 1015+161 each has an infrared excess that can be understood as…
We report the X-ray detection of the brown dwarf (BD) companion TWA 5B in a $\simeq 12$ Myr old pre-main sequence binary system. We clearly resolve the faint companion (35 photons) separated from the X-ray luminous primary by 2 arcsec in a…
We have detected an ionized nebula around the hot DO white dwarf KPD 0005+5106, and used the [OIII]/H-alpha ratios and nebular velocities to separate this nebula from the background HII region of AO Cas. The angular size of the [OIII]…
The presence of infrared excess flux observed in white dwarfs (WDs) is related to the existence of debris disks or substellar companions. These systems provide important clues in the study of extrasolar planetary material and binary…
The Chandra X-ray Observatory has detected relatively hard X-ray emission from the central stars of several planetary nebulae (PNe). A subset have no known late-type companions, making it very difficult to isolate which of several competing…
Identification of white dwarfs (WD) with main-sequence (MS) companions and characterization of their properties can put important constraints on our understanding of binary stellar evolution and guide the theoretical predictions for a wide…
For the first time, we have identified photospheric emission lines in the far-UV spectrum of a white dwarf. They were discovered in the Far Ultraviolet Spectroscopic Explorer spectrum of the hot (Teff~200,000 K) DO white dwarf KPD0005+5106…
A recent analysis of Chandra X-ray data of the metal-polluted white dwarf (WD) G29-38 has revealed X-ray emission that can be attributed to the accretion of debris from a planetary body. In the light of this detection we revisit here…
In a dwarf nova, the accretion disk around the white dwarf is a source of ultraviolet, optical, and infrared photons, but is never hot enough to emit X-rays. Observed X-rays instead originate from the boundary layer between the disk and the…
Symbiotic stars are a heterogeneous class of interacting binaries. Among them, RT Cru has been classified as prototype of a subclass that is characterised by hard X-ray spectra extending past ~20 keV. We analyse ~8.6 Ms of archival INTEGRAL…
The origin of the hard (2-10 keV) X-ray background has remained mysterious for over 35 years. Most of the soft (0.5-2 keV) X-ray background has been resolved into discrete sources, which are primarily quasars; however, these sources do not…
We have used the excellent sensitivity of XMM-Newton to obtain the first high-quality X-ray spectrum of a Wolf-Rayet (WR) star which is not known to be a member of a binary system. Our target, the nitrogen-type star WR 110 (= HD 165688) was…
We report on the X-ray spectral and spatial evolution of the Symbiotic star R Aqr. Through a multi-epoch observational campaign performed with Chandra between 2017 and 2022, we study the X-ray emission of this binary system, composed of an…
The central star of NGC 2392 shows the hardest X-ray emission among central stars of planetary nebulae (CSPNe). The recent discovery of a spectroscopic companion with an orbital period of 1.9 days could provide an explanation for its hard…
Low mass axion-like particles could be produced in abundance within the cores of hot, compact magnetic white dwarf (MWD) stars from electron bremsstrahlung and converted to detectable X-rays in the strong magnetic fields surrounding these…
A recent cross-correlation between the SDSS DR7 White Dwarf Catalog with the Wide-Field Infrared Survey Explorer ($WISE$) all-sky photometry at 3.4, 4.6, 12, and 22 microns performed by Debes et al. (2011) resulted in the discovery of 52…
In recent years, the number of white dwarfs (WDs) showing infrared (IR) excesses, attributed to circumstellar dust disks, has grown significantly. Gaseous disks have also been detected in some WDs with dust. We obtained optical spectra with…
The Galactic plane is a strong hard x-ray emitter and the emission forms a narrow continuous ridge. The currently known hard x-ray sources are far too few to explain the ridge x-ray emission, and the fundamental question as to whether the…
Spitzer Space Telescope IRAC 3-8 micron and AKARI IRC 2-4 micron photometry are reported for ten white dwarfs with photospheric heavy elements; nine relatively cool stars with photospheric calcium, and one hotter star with a peculiar high…