B. T. Gansicke

The University of Warwick, Coventry, England, United Kingdom

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Publications (39)54.5 Total impact

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    ABSTRACT: We report the discovery of an extremely close white dwarf plus F dwarf main-sequence star in a 12 hour binary identified by combining data from the RAdial Velocity Experiment (RAVE) survey and the Galaxy Evolution Explorer (GALEX) survey. A combination of spectral energy distribution fitting and optical and Hubble Space Telescope ultraviolet spectroscopy allowed us to place fairly precise constraints on the physical parameters of the binary. The system, TYC 6760-497-1, consists of a hot Teff~21,500K, M~0.65Ms white dwarf and an F8 star (M~1.23Ms, R~1.35Rs) seen at a low inclination (i~35 deg). The system is likely the descendent of a binary that contained the F star and a ~2Ms A-type star that filled its Roche-lobe on the second asymptotic giant branch, initiating a common envelope phase. The F star is extremely close to Roche-lobe filling and there is likely to be a short phase of thermal timescale mass-transfer onto the white dwarf. During this phase it will grow in mass by up to 20 per cent, until the mass ratio reaches close to unity, at which point it will appear as a standard cataclysmic variable star. Therefore, TYC 6760-497-1 is the first known progenitor of a super-soft source system, but will not undergo a supernova Ia explosion. Once an accurate distance to the system is determined by Gaia, we will be able to place very tight constraints on the stellar and binary parameters.
    Monthly Notices of the Royal Astronomical Society 03/2015; 452(2). DOI:10.1093/mnras/stv1395 · 5.23 Impact Factor
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    ABSTRACT: Building on the experience of the high-resolution community with the suite of VLT high-resolution spectrographs, which has been tremendously successful, we outline here the (science) case for a high-fidelity, high-resolution spectrograph with wide wavelength coverage at the E-ELT. Flagship science drivers include: the study of exo-planetary atmospheres with the prospect of the detection of signatures of life on rocky planets; the chemical composition of planetary debris on the surface of white dwarfs; the spectroscopic study of protoplanetary and proto-stellar disks; the extension of Galactic archaeology to the Local Group and beyond; spectroscopic studies of the evolution of galaxies with samples that, unlike now, are no longer restricted to strongly star forming and/or very massive galaxies; the unraveling of the complex roles of stellar and AGN feedback; the study of the chemical signatures imprinted by population III stars on the IGM during the epoch of reionization; the exciting possibility of paradigm-changing contributions to fundamental physics. The requirements of these science cases can be met by a stable instrument with a spectral resolution of R~100,000 and broad, simultaneous spectral coverage extending from 370nm to 2500nm. Most science cases do not require spatially resolved information, and can be pursued in seeing-limited mode, although some of them would benefit by the E-ELT diffraction limited resolution. Some multiplexing would also be beneficial for some of the science cases. (Abridged)
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    ABSTRACT: The three tables contain the photometry from different observatories as plotted with different colours in Figure 6 of the paper. (3 data files).
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    ABSTRACT: We outline the purpose, strategy and first results of a deep, high cadence, photometric survey of the Kepler field using the Isaac Newton Telescope on La Palma and the MDM 1.3m Telescope on Kitt Peak. Our goal was to identify sources located in the Kepler field of view which are variable on a timescale of a few mins to 1 hour. The astrophysically most interesting sources would then have been candidates for observation using Kepler using 1 min sampling. Our survey covered ~42% of the Kepler field of view and we have obtained light curves for 7.1x10^5 objects in the range 13<g<20. We have discovered more than 100 variable sources which have passed our two stage identification process. As a service to the wider community, we make our data products and cleaned CCD images available to download. We obtained Kepler data of 18 sources which we found to be variable using our survey and we give an overview of the currently available data here. These sources include a pulsating DA white dwarf, eleven delta Sct stars which have dominant pulsation periods in the range 24 min to 2.35 hrs, three contact binaries, and a cataclysmic variable (V363 Lyr). One of the delta Sct stars is in a contact binary.
    Monthly Notices of the Royal Astronomical Society 10/2013; 437(1). DOI:10.1093/mnras/stt1863 · 5.23 Impact Factor
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    ABSTRACT: We present an ultraviolet spectrum and light curve of the short orbital period cataclysmic variable EZ Lyn obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope 14 months after its dwarf nova outburst, along with ground-based optical photometry. The UV spectrum can be fit with a 13,100K, log g=8 white dwarf using 0.5 solar composition, while fits to the individual lines are consistent with solar abundance for Si and Al, but only 0.3 solar for C. The Discrete Fourier Transforms of the UV and optical light curves at 14 months following outburst show a prominent period at 256 sec. This is the same period reported by Pavlenko in optical data obtained 7 months and one year after outburst, indicating its long term stability over several months, but this period is not evident in the pre-outburst data and is much shorter than the 12.6 min period that was seen in observations obtained during an interval from 8 months to 2.5 years after the 2006 outburst. In some respects, the long and short periods are similar to the behavior seen in GW Lib after its outburst but the detailed explanation for the appearance and disappearance of these periods and their relation to non-radial pulsation modes remain to be explored with theoretical models.
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    R. C. Reis · P. J. Wheatley · B. T. Gansicke · J. P. Osborne
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    ABSTRACT: By studying Swift X-ray spectra of an optically selected, non-magnetic sample of nearby cataclysmic variables (CVs), we show that there is a population with X-ray luminosity much lower than accounted for in existing studies. We find an average 0.5–10.0 keV luminosity of $8\times 10^{29}{\,{\rm erg \,s^{-1}}}$ which is an order of magnitude lower than observed in previous samples. Looking at the co-added X-ray spectrum of 20 CVs, we show that the spectral properties of this optically selected, low X-ray luminosity sample – likely characteristic of the dominant population of CVs – resemble that of their brighter counterpart, as well as the X-ray emission originating in the Galactic ridge. It is argued that if the space density of CVs is greater than the current estimates, as it is indeed predicted by population synthesis models, then CVs can significantly contribute to the Galactic ridge emission.
    Monthly Notices of the Royal Astronomical Society 01/2013; 430(3). DOI:10.1093/mnras/stt025 · 5.23 Impact Factor
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    ABSTRACT: To determine the spectral type, the rotational velocity and the radial velocity amplitude of the primary, we obtained 46 high-resolution (R~85000) echelle spectra using the HERMES spectrograph at the 1.2-m Mercator telescope (La Palma, Canary Islands). These were reduced using the standard instrument-specific data reduction pipeline. Additionally, we obtained 29 spectra with the ISIS spectrograph mounted on the 4.2-m William Herschel Telescope (La Palma, Canary Islands). The Kepler data from Q0 (quarter 0), Q1, Q2 and Q3 were retrieved from the public archive (http://archive.stsci.edu/kepler/). The data span 229-d, resulting in a data set of 212-d of observations excluding the gaps. (6 data files).
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    ABSTRACT: UVEX is a double-pass survey in the Johsnon-U, Sloan-g, Sloan-r filters, and a narrow-band filter centered on the HeI5875Å line. (3 data files).
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    ABSTRACT: We present the results of the first spectroscopic follow-up of 132 optically blue UV-excess sources selected from the UV-excess survey of the Northern Galactic Plane (UVEX). The UV-excess spectra are classified into different populations and grids of model spectra are fit to determine spectral types, temperatures, surface gravities and reddening. From this initial spectroscopic follow-up 95% of the UV-excess candidates turn out to be genuine UV-excess sources such as white dwarfs, white dwarf binaries, subdwarfs type O and B, emission line stars and QSOs. The remaining sources are classified as slightly reddened main-sequence stars with spectral types later than A0V. The fraction of DA white dwarfs is 47% with reddening smaller than E(B-V)<0.7 mag. Relations between the different populations and their UVEX photometry, Galac- tic latitude and reddening are shown. A larger fraction of UVEX white dwarfs is found at magnitudes fainter than g>17 and Galactic latitude smaller than |b|<4 compared to main-sequence stars, blue horizontal branch stars and subdwarfs.
    Monthly Notices of the Royal Astronomical Society 06/2012; 426(2). DOI:10.1111/j.1365-2966.2012.21615.x · 5.23 Impact Factor
  • J. Girven · B. T. Gansicke · D. Steeghs · D. Koester
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    ABSTRACT: These tables show the objects from the spectroscopic and photometric-only samples in "spec.dat" and "phot.dat" respectively. The table ire.dat shows all objects classified as having an infrared excess from its SDSS and UKIDSS spectral energy distribution. Finally posqso.dat lists the objects believed to be quasars from their SDSS and UKIDSS spectral energy distribution. (4 data files).
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    ABSTRACT: We have obtained radial velocity information spanning at least two nights from our follow-up observations of several hundred SDSS WDMS binaries (e.g. Rebassa-Mansergas et al. 2008MNRAS.390.1635R; Schreiber et al. 2008A&A...484..441S, 2010, Cat. J/A+A/513/L7) supplemented by the SDSS sub-spectra (all SDSS spectra are the result of combining at least three individual sub-exposures; see Rebassa-Mansergas et al. 2007, Cat. J/MNRAS/382/1377, 2010, Cat. J/MNRAS/402/620). (1 data file).
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    ABSTRACT: We present an updated version of the spectroscopic white dwarf-main sequence (WDMS) binary catalogue from the Sloan Digital Sky Survey (SDSS). 395 new systems are serendipitous discoveries from the spectroscopic SDSSI/II Legacy targets. As part of SEGUE, we have carried out a dedicated and efficient (64 per cent success rate) search for WDMS binaries with a strong contribution of the companion star, which were underrepresented by all previous surveys, identifying 251 additional systems. In total, our catalogue contains 2248 WDMS binaries, and includes, where available, magnitudes from the GALEX All Sky Survey in the ultraviolet and from the UKIRT Infrared Sky Survey (UKIDSS) in the near-infrared. We also provide radial velocities of the companion stars, measured from the SDSS spectroscopy using the NaI8183.27,8194.81 absorption doublet and/or the Halpha emission. Using an updated version of our spectral decomposition/fitting technique we determine/update the white dwarf effective temperatures, surface gravities and masses, as well as the spectral type of the companion stars for the entire catalogue. Comparing the distributions of white dwarf mass, temperature, and companion spectral type, we confirm that our SEGUE survey project has been successful in identifying WDMS binaries with cooler and more massive white dwarfs, as well as earlier spectral types than found previously. Finally, we have developed a publicly available interactive on-line data base for spectroscopic SDSS WDMS binaries containing all available stellar parameters, radial velocities and magnitudes which we briefly describe.
    Monthly Notices of the Royal Astronomical Society 10/2011; 419. DOI:10.1111/j.1365-2966.2011.19923.x · 5.23 Impact Factor
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    ABSTRACT: For the survey phase of the Kepler Mission, three groups submitted proposals containing candidate hot subdwarf and white dwarf stars. Of the stars included in these proposals, 142 were accepted into the list of KASC survey stars. Of these, six were observed during the 9.7d commissioning run, and 57 were observed during the first four (out of 10) survey months. All 63 stars are listed in Table 1. (1 data file).
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    ABSTRACT: For the survey phase of the Kepler Mission, three groups submitted proposals containing candidate hot subdwarf and white dwarf stars. Of the stars included in these proposals, 142 were accepted into the list of KASC survey stars. Of these, six were observed during the 9.7d commissioning run, and 57 were observed during the first four (out of 10) survey months. All 63 stars are listed in Table 1. (1 data file).
  • Ryan K. Campbell · Paula Szkody · Boris T. Gansicke · Anjum Mukadam
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    ABSTRACT: Oribital phase‐resolved spectra of EF Eri were obtained with the Solar Blind Channel on the Hubble Space Telescope during its low state. The specta peaked at 1500 and 1700 Å, and the integrated UV light curves displayed quasi‐sinusoidal modulations. WD hotspot and cyclotron emission models were computed in an attempt to fit the spectroscopic morphology throughout the orbit.
    12/2010; 1314(1):206-207. DOI:10.1063/1.3536368
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    ABSTRACT: We present VLT spectroscopy and NTT photometry of the faint cataclysmic binary SDSS J003941.06+005427.5. This object shows triple-peaked Halpha emission with all three peaks variable in both strength and velocity. We measure an orbital period of 91.395 ± 0.093 min from the velocity variations of the wings of the Halpha emission line. Using the GALEX and SDSS photometry of this object, we determine a white dwarf temperature of 15 000 K and a very late (&gap;L2) spectral type for the companion star. These measurements, plus the relatively long orbital period, suggest that SDSS J003941.06+005427.5 may be a post-bounce cataclysmic variable. Doppler maps of the Halpha and He I 6678 Å emission features show an accretion disc with a non-uniform brightness and departures from Keplerian flow. The third emission peak is detected only in Halpha and at a relatively low velocity amplitude of 202 ± 3 km s-1. We are unable to explain this emission as arising from either the white dwarf, the secondary star, or the accretion disc. We tentatively attribute this mysterious central peak to a coronal loop anchored at the secondary star. If confirmed, this would be the first example of a slingshot prominence in a CV with a low mass-transfer rate and/or a fully convective secondary star. Reduced data (photometry and spectroscopy) are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/viz-bin/qcat?J/A+A/524/A86
    Astronomy and Astrophysics 09/2010; DOI:10.1051/0004-6361/201015633 · 4.48 Impact Factor
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    ABSTRACT: Long-slit spectroscopy (29 spectra obtained over two nights) and differential photometry (167 datapoints obtained over two nights) are presented for the cataclysmic variable SDSS J003941.06+005427.5. (3 data files).
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    ABSTRACT: To interpret the UVEX observations, simulations of the colours of stars and the effect of reddening are a very powerful and important tool. In obtaining the simulated colours, we follow the procedure as outlined in Drew et al. (2005MNRAS.362..753D) for the IPHAS. (6 data files).
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    ABSTRACT: Time-resolved low resolution Hubble Space Telescope ultraviolet spectra together with ground-based optical photometry and spectra are used to constrain the temperatures and pulsation properties of six cataclysmic variables containing pulsating white dwarfs. Combining our temperature determinations for the five pulsating white dwarfs that are several years past outburst with past results on six other systems shows that the instability strip for accreting pulsating white dwarfs ranges from 10,500-15,000K, a wider range than evident for ZZ Ceti pulsators. Analysis of the UV/optical pulsation properties reveals some puzzling aspects. While half the systems show high pulsation amplitudes in the UV compared to their optical counterparts, others show UV/optical amplitude ratios that are less than one or no pulsations at either wavelength region. Comment: 19 pages, 6 tables 14 figs; accepted in ApJ
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    John Southworth · C. M. Copperwheat · B. T. Gansicke · S. Pyrzas
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    ABSTRACT: We present photometry of nine cataclysmic variable stars identified by the Sloan Digital Sky Survey, aimed at measuring the orbital periods of these systems. Four of these objects show deep eclipses, from which we measure their orbital periods. The light curves of three of the eclipsing systems are also analysed using the LCURVE code, and their mass ratios and orbital inclinations determined. SDSS J075059.97+141150.1 has an orbital period of 134.1564 +/- 0.0008 min, making it a useful object with which to investigate the evolutionary processes of cataclysmic variables. SDSS J092444.48+080150.9 has a period of 131.2432 +/- 0.0014 min and is probably magnetic. The white dwarf ingress and egress phases are very deep and short, and there is no clear evidence that this object has an accretion disc. SDSS J115207.00+404947.8 and SDSS J152419.33+220920.1 are nearly identical twins, with periods of 97.5 +/- 0.4 and 93.6 +/- 0.5 min and mass ratios of 0.14 +/- 0.03 and 0.17 +/- 0.03, respectively. Their eclipses have well-defined white dwarf and bright spot ingress and egress features, making them excellent candidates for detailed study. All four of the orbital periods presented here are shorter than the 2-3 hour period gap observed in the known population of cataclysmic variables. Comment: Accepted for publication in A&A. 9 pages, with 10 figures and 5 tables
    Astronomy and Astrophysics 12/2009; DOI:10.1051/0004-6361/200913576 · 4.48 Impact Factor