Detection of a Variable Infrared Excess Around SDSS 121209.31+013627.7

Abstract

We present near-infrared $JH{K}_s$ photometry and light curves of the candidate magnetic white dwarf+brown dwarf binary SDSS J121209.31+013627.7 and report on the detection of near-infrared excess and variability in the $K_s-$band. The observed near-infrared excess can be explained by the presence of an L7 brown dwarf and an extra emission source. The $J$ and $H$ light curves appear flat, which rules out eclipses deeper than 0.2 mag and the presence of an accretion hot spot on the white dwarf. From the variable $K_s$ lightcurve, we get a refined period for the system of 88$\pm$1 minutes. We show that the observed variability in $K_s-$band can be explained by cyclotron emission, which can be modeled by a small spot on the surface of the white dwarf. SDSS 1212 exhibits similarities to the ultra-short period polar EF Eridani, however the lack of evidence for Roche-lobe overflow accretion suggests it may be a pre-polar.

arXiv comment13 pages, 2 figures, accepted to ApJL

References in corpus (6)

• Color Transformations for the 2MASS Second Incremental Data Release
• Preliminary Parallaxes of 40 L and T Dwarfs from the U.S. Naval Observatory Infrared Astrometry Program
• Magnetic White Dwarfs from the SDSS. The First Data Release
• New Low Accretion-Rate Magnetic Binary Systems and their Significance for the Evolution of Cataclysmic Variables
• Discovery of a Magnetic White Dwarf/Probable Brown Dwarf Short-Period Binary
• Phase-Resolved Infrared H- and K-band Spectroscopy of EF Eridani

Cited by in corpus (17)

• DA white dwarfs in SDSS DR7 and a search for infrared excess emission
• The WIRED Survey II: Infrared Excesses in the SDSS DR7 White Dwarf Catalog
• The chemical diversity of exo-terrestrial planetary debris around white dwarfs
• Magnetic fields in isolated and interacting white dwarfs
• Analysis of hydrogen-rich magnetic white dwarfs detected in the Sloan Digital Sky Survey
• White dwarfs in the UKIDSS Large Area Survey: The Substellar Companion Fraction
• New Close Binary Systems from the SDSS-I (Data Release Five) and the Search for Magnetic White Dwarfs in Cataclysmic Variable Progenitor Systems
• The nature of the close magnetic white dwarf + probable brown dwarf binary SDSS J121209.31+013627.7
• Two Additions to the New Class of Low Accretion-Rate Magnetic Binaries
• A Near-Infrared Spectroscopic Study of the Accreting Magnetic White Dwarf SDSS J121209.31+013627.7 and its Substellar Companion
• The evolutionary state of short period magnetic white dwarf binaries
• Enigmas from the Sloan Digital Sky Survey DR7 Kleinman White Dwarf Catalog
• X-ray orbital modulation of a white dwarf accreting from an L dwarf: The system SDSS J121209.31+013627.7
• Dynamical determination of the quadrupole mass moment of a white dwarf
• GALEX and Optical Light Curves of WX LMi, SDSSJ103100.5+202832.2 and SDSSJ121209.31+013627.7
• CSS1603+19: a low-mass polar near the cataclysmic variable period minimum
• SRGe2149+6736 -- the new candidate to AM~Her type variables discovered by eROSITA telescope on "Spectrum--Roentgen--Gamma" orbital observatory