Phase-Resolved Spectroscopy of Gaia14aae: Line Emission From Near the White Dwarf Surface

Abstract

AM CVn binaries are a class of ultracompact, hydrogen-deficient binaries, each consisting of a white dwarf accreting helium-dominated material from a degenerate or semi-degenerate donor star. Of the 56 known systems, only Gaia14aae undergoes complete eclipses of its central white dwarf, allowing the parameters of its stellar components to be tightly constrained. Here, we present phase-resolved optical spectroscopy of Gaia14aae. We use the spectra to test the assumption that the narrow emission feature known as the `central spike' traces the motion of the central white dwarf. We measure a central spike velocity amplitude of $13.8\pm 3.2$ km/s, which agrees at the 1 $\sigma$ level with the predicted value of $17.6\pm 1.0$ km/s based on eclipse-derived system parameters. The orbital phase offset of the central spike from its expected position is $4\pm 15$ ${}^{\circ }$, consistent with 0 ${}^{\circ }$. Doppler maps of the He I lines in Gaia14aae show two accretion disc bright spots, as seen in many AM CVn systems. The formation mechanism for the second spot remains unclear. We detect no hydrogen in the system, but we estimate a 3 $\sigma$ limit on H$\alpha$ emission with an equivalent width of -1.14 Å. Our detection of nitrogen and oxygen with no corresponding detection of carbon, in conjunction with evidence from recent studies, mildly favours a formation channel in which Gaia14aae is descended from a cataclysmic variable with a significantly evolved donor.

arXiv comment16 pages, accepted by MNRAS

References in corpus (38)

• A Comprehensive Spectroscopic Analysis of DB White Dwarfs
• The Donor Stars of Cataclysmic Variables
• Superhumps in Cataclysmic Binaries. XXV. q_crit, epsilon(q), and Mass-Radius
• Prospects for detection of detached double white dwarf binaries with Gaia, LSST and LISA
• LISA verification binaries with updated distances from Gaia Data Release 2
• The chemical composition of donors in AM CVn stars and ultra-compact X-ray binaries: observational tests of their formation
• Black hole formation and fallback during the supernova explosion of a $40{\mathrm{M}}_{\odot }$ star
• Population Synthesis of Cataclysmic Variables: I. Inclusion of Detailed Nuclear Evolution
• Evolution of Low-Mass Helium Stars in Semidetached Binaries
• Hydrodynamics of the stream-disk impact in interacting binaries
• The physical properties of AM CVn stars: new insights from Gaia DR2
• The Thermal Evolution of the Donors in AM CVn Binaries
• New Method to Estimate Binary Mass Ratios by Using Superhumps
• Ultracompact AM CVn Binaries from the Sloan Digital Sky Survey: Three Candidates Plus the First Confirmed Eclipsing System
• A search for the hidden population of AM CVn binaries in the Sloan Digital Sky Survey
• Kinematics of the ultra-compact helium accretor AM Canum Venaticorum
• One thousand cataclysmic variables from the Catalina Real-time Transient Survey
• Characterizing accreting double white dwarf binaries with the Laser Interferometer Space Antenna and Gaia
• SDSS J0926+3624: The shortest period eclipsing binary star
• Kinematics of the helium accretor GP Com
• CSS100603:112253-111037: A helium-rich dwarf nova with a 65 minute orbital period
• Total eclipse of the heart: The AM CVn Gaia14aae / ASSASN-14cn
• New results on GP Com
• High-Speed Photometry of Gaia14aae: An Eclipsing AM CVn That Challenges Formation Models
• Phase-resolved spectroscopy of the helium dwarf nova 'SN 2003aw' in quiescence
• On the orbital periods of the AM CVn stars HP Librae and V803 Centauri
• UVES and X-Shooter spectroscopy of the emission line AM CVn systems GP Com and V396 Hya
• Precision ephemerides for gravitational-wave searches -- III. Revised system parameters of Sco X-1
• Phase resolved spectroscopy and Kepler photometry of the ultracompact AM CVn binary SDSS J190817.07+394036.4
• HST and Optical Data Reveal White Dwarf Cooling, Spin and Periodicities in GW Librae 3-4 Years after Outburst
• Orbital periods and Accretion disc structure of four AM CVn systems
• A 15.7-Minute AM CVn Binary Discovered in K2
• A New Sub-Period-Minimum CV with Partial Hydrogen Depletion and Evidence of Spiral Disk Structure
• System mass constraints for the accreting millisecond pulsar XTE J1814-338 using Bowen fluorescence
• The long-period AM CVn star SDSS J155252.48+320150.9
• Superoutburst of SDSS J090221.35+381941.9: First Measurement of Mass Ratio in an AM CVn-Type Object using Growing Superhumps
• Are Superhumps Good Measures of the Mass Ratio for AM CVn Systems?
• The photometric period in ES Ceti

Cited by in corpus (8)

• Discovery and characterization of five new eclipsing AM CVn systems
• Spectroscopic and Photometric Periods of Six Ultracompact Accreting Binaries
• Reversing the verdict: Cataclysmic variables could be the dominant progenitors of AM CVn binaries after all
• A 9-Hr CV With One Outburst in 4 Years of Kepler Data
• Evolved cataclysmic variables as progenitors of AM CVn stars
• A Catalogue of Ultracompact Mass-Transferring White Dwarf Binaries
• New insights into the helium star formation channel of AM CVn systems with explanations of Gaia14aae and ZTFJ1637+49
• Spectroscopy of the helium-rich binary ES Ceti reveals accretion via a disc and evidence for eclipse