11 research outputs found
Heavy metals in a light white dwarf: abundances of the metal-rich, extremely low-mass GALEX J1717+6757
Using the Hubble Space Telescope, we detail the first abundance analysis enabled by farultraviolet
spectroscopy of a low-mass (0.19 M) white dwarf (WD), GALEX J1717+6757,
which is in a 5.9-h binary with a fainter, more-massive companion. We see absorption from
nine metals, including roughly solar abundances of Ca, Fe, Ti, and P. We detect a significantly
sub-solar abundance of C, and put upper limits on N and O that are also markedly sub-solar.
Updated diffusion calculations indicate that all metals should settle out of the atmosphere
of this 14 900 K, log g = 5.67 WD in the absence of radiative forces in less than 20 yr,
orders of magnitude faster than the cooling age of hundreds of Myr. We demonstrate that
ongoing accretion of rocky material that is often the cause of atmospheric metals in isolated,
more massive WDs is unlikely to explain the observed abundances in GALEX J1717+6757.
Using new radiative levitation calculations, we determine that radiative forces can counteract
diffusion and support many but not all of the elements present in the atmosphere of this WD;
radiative levitation cannot, on its own, explain all of the observed abundance patterns, and
additional mechanisms such as rotational mixing may be required. Finally, we detect both
primary and secondary eclipses using ULTRACAM high-speed photometry, which we use to
constrain the low-mass WD radius and rotation rate as well as update the ephemeris from the
discovery observations of this WD+WD binary
WD1032+011, an inflated brown dwarf in an old eclipsing binary with a white dwarf
We present the discovery of only the third brown dwarf known to eclipse a non-accreting white dwarf. Gaia parallax information and multicolour photometry confirm that the white dwarf is cool (9950 ± 150 K) and has a low mass (0.45 ± 0.05 M⊙), and spectra and light curves suggest the brown dwarf has a mass of 0.067 ± 0.006 M⊙ (70MJup) and a spectral type of L5 ± 1. The kinematics of the system show that the binary is likely to be a member of the thick disc and therefore at least 5-Gyr old. The high-cadence light curves show that the brown dwarf is inflated, making it the first brown dwarf in an eclipsing white dwarf-brown dwarf binary to be so
Discovery of the Closest Hot Subdwarf Binary with White Dwarf Companion
Contains fulltext :
117396.pdf (preprint version ) (Open Access
The not-so-extreme white dwarf of the CV GD 552
GD 552 is a cataclysmic binary which was previously believed to be composed of an M-star and a white dwarf, the latter having an extreme mass of 1.4 solar masses. In a recent paper we showed that this is not compatible with new observational evidence and presented an alternative model in which the white dwarf has a typical mass and the companion is a brown dwarf, making the system a likely member of the elusive group of CVs which have already evolved through minimum orbital period. Here we present additional spectroscopical evidence supporting this conclusion by means of skew mapping
IGR J17303-0601 is a new intermediate polar
Item does not contain fulltextWe have identified IGR J17303-0601 (1RXS J173021.5-055933) as an intermediate polar (IP). The optical counterpart is USNOA2.0 0825_10606993 (RA=17h30m21.9s Dec=-05d59m31s). Using optical photometry obtained in 2003 at the JKT and at the OGS we determine the white dwarf spin period to be 120s, which is the second-shortest spin period discovered so far (after AE Aqr, Pspin=33s). The spin folded light curve has a double-pulse structure, suggesting that both accreting poles / accretion curtains contribute to the optical light
RX J1313.2-3259, a missing link in CV evolution?
SIGLEAvailable from: www.mpa-garching.mpg.de / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
A planetary nebula around Nova V458 Vulpeculae undergoing flash ionization
Original article can be found at: http://www.iop.org/EJ/journal/apjl Copyright American Astronomical Society [Full text of this article is not available in the UHRA]Peer reviewe