New results on GP Com

  title={New results on GP Com},
  author={Luisa Morales-Rueda and Thomas R. Marsh and D Steeghs and Eduardo Unda-Sanzana and Janet H. Wood and R. C. North University of Southampton and Cfa and Keele University and Met Office},
  journal={Astronomy and Astrophysics},
We present high resolution optical and UV spectra of the 46 min orbital period, helium binary, GP Com. Our data contains simultaneous photometric correction which confirms the flaring behaviour observed in previous optical and UV data. In this system all lines show a triple peaked structure where the outer two peaks are associated with the accretion disc around the compact object. The main aim of this paper is to constrain the origin of the central peak, also called "central spike". We find… 
Optical spectroscopy of the dwarf nova U Geminorum
The dwarf nova U Gem is unique in having a direct measurement of the K velocity of its white dwarf from Hubble Space Telescope (HST) spectra (K-1 = 107 +/- 2 km s(-1) from Long et al.). We present
Time-resolved spectroscopy of the pulsating CV GW Lib
We present time-resolved optical spectroscopy of the dwarf nova GW Librae during its rare 2007 April superoutburst and compare these with quiescent epochs. The data provide the first opportunity to
SDSS J124058.03-015919.2: a new AM CVn star with a 37-min orbital period
We present high time-resolution spectroscopy with the Very Large Telescope of SDSS J124058.03−015919.2, a new helium-transferring binary star identified in the Sloan Digital Sky Survey. We measure an
Discovery of a high state AM CVn binary in the Galactic Bulge Survey
We report on the discovery of a hydrogen-deficient compact binary (CXOGBS J175107.6-294037) belonging to the AM CVn class in the Galactic Bulge Survey. Deep archival X-ray observations constrain the
The long-period AM CVn star SDSS J155252.48+32 0150.9
The Sloan Digital Sky Survey has been instrumental in obtaining a homogeneous sample of the rare AM CVn stars: mass-transferring binary white dwarfs. As part of a campaign of spectroscopic follow-up
Orbital periods and accretion disc structure of four AM CVn systems
Phase-resolved spectroscopy of four AM CVn systems obtained with the William Herschel Telescope and the Gran Telescopio de Canarias is presented. SDSS J120841.96+355025.2 was found to have an orbital
Phase-resolved spectroscopy of Gaia14aae: line emission from near the white dwarf surface
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
A Census of AM CVn Stars: Three New Candidates and One Confirmed 48.3-Minute Binary
We present three new candidate AM CVn binaries, and one confirmed new system, from a spectroscopic survey of color-selected objects from the Sloan Digital Sky Survey (SDSS). All four systems were
The photometric period in ES Ceti
We present ULTRACAM photometry of ES Cet, an ultracompact binary with a 620-s orbital period. The mass transfer in systems such as this one is thought to be driven by gravitational radiation, which
UVES and X-Shooter spectroscopy of the emission line AM CVn systems GP Com and V396 Hya
We present time-resolved spectroscopy of the AM CVn-type binaries GP Com and V396 Hya obtained with VLT/X-Shooter and VLT/UV-Visual Echelle Spectrograph (UVES). We fully resolve the narrow central


Kinematics of the helium accretor GP Com
I present and analyse time-resolved B-band spectra of the double-degenerate binary star GP Com. The spectra confirm the presence and period (46.5 min) of the `S'-wave feature found by Nather,
The discovery of high-velocity flares in NV and the detection of carbon in the double degenerate binary GP Com
We present time-resolved ultraviolet spectra of the ultrashort-period binary GP Com taken with the Hubble Space Telescope. During our observations GP Com displayed spectacular variability in the
The Lick Planet Search: Detectability and Mass Thresholds
We present an analysis of 11 yr of precision radial velocity measurements of 76 nearby solar-type stars from the Lick radial velocity survey. For each star, we report on variability, periodicity, and
CE 315: A New Interacting Double-Degenerate Binary Star*
We present spectroscopic observations of object CE 315 revealing a blue continuum with strong emission lines. Most of the detected lines are identified with He I or He II in emission, with a handful
Population synthesis for double white dwarfs. II. Semi-detached systems: AM CVn stars
We study two models for AM CVn stars: white dwarfs accreting (i) from a helium white dwarf companion and (ii) from a helium-star donor. We show that in the first model possibly no accretion disk
Spectroscopic Studies of DB White Dwarfs: Improved Stark Profiles for Optical Transitions of Neutral Helium
New Stark profiles for 21 He I lines and their forbidden components have been calculated for electron densities ranging from 1014 to 6 × 1017 cm-3, and for temperatures ranging from 10,000 K to
The ultraviolet spectrum of the twin-degenerate interacting binary G61-29
A low-resolution IUE spectrum (1200 A-1900 A) of the twin-degenerate white-dwarf binary star G61-29 is presented. A comparison is made to similar IUE spectra of the old novae DQ Her and V603 Aql.
The Optical Spectrum of Extreme Helium Stars: A Hotbed of Forbidden Components of Neutral Helium
We develop a simple criterion, based on the general properties of weakly excited forbidden components in neutral helium, to predict which forbidden components should be observable in the He I
The apparent nebulosity in the region around the twin degenerate interacting binary G61-29 is studied. It has been assumed that this nebulosity represents material ejected from the system. However, a
Digital spectra of point sources can be extracted with maximum signal-to-noise ratio by applying appropriate weights across the profile of the object. The first stage in computing these weights