X-ray orbital modulation of a white dwarf accreting from an L dwarf. The system SDSS J121209.31+013627.7
Journal
Date Issued
2017
Author(s)
Abstract
In an XMM-Newton observation of the binary SDSS J121209.31+013627.7, consisting of a white dwarf and an L dwarf, we detect X-ray orbital modulation as proof of accretion from the substellar companion onto the magnetic white dwarf. We constrain the system geometry (inclination as well as magnetic and pole-cap angle) through modelling of the X-ray light curve, and we derive a mass accretion rate of 3.2 × 10-14M☉/ yr from the X-ray luminosity ( 3 × 1029 erg/s). From X-ray studies of L dwarfs, a possible wind driven from a hypothesized corona on the substellar donor is orders of magnitude too weak to explain the observed accretion rate, while the radius of the L dwarf is comparable to its Roche lobe (0.1 R☉), making Roche-lobe overflow the likely accretion mechanism in this system.
Volume
598
Start page
L6
Issn Identifier
0004-6361
Ads BibCode
2017A&A...598L...6S
Rights
open.access
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