Binary Stars

Start year
1988
Organizational Unit

Grants related:

    General
    Description

    The study of binary stars is essential to stellar astrophysics. A large number of stars form and evolve within binary systems. Therefore, their study is fundamental to understand stellar and galactic evolution. Particularly relevant is that binary systems are still the best source of precise stellar mass and radius measurements.

    Research lines:

    • Determination of absolute parameters of Algol-type eclipsing binaries. In 2006 we started a new project to derive accurate masses and radii of low-mass eclipsing binaries of spectral type M. These will be confronted with theoretical predictions for the lower main sequence.
    • Study of the structure and evolution of cataclysmic variables (CVs). Among the main goals we highlight a fundamental test of the current evolution theory, which will observationally prove or discard several of its predictions. In doing so, population studies on both the observed minimum orbital period region (~ 80 min) and the upper boundary of the period gap (in the 3-4.5 hour orbital period range) are being performed. On the other hand, our research has demonstrated the existence of a huge pile-up of intrinsically very luminous CVs (with the highest mass transfer rates known), with orbital periods just above 3 hours, in apparent contradiction to theoretical expectations. The masses of these systems are being determined using ToO time in 8-m class telescopes as VLT and Gemini, and the 10.4-m GTC when a system falls into a low brightness state characterised by the quenching of the mass transfer from the donor star to the white dwarf.
    • Study of central binary stars of planetary nebulae. One plausible effect leading to bipolar shapes in planetary nebulae is the presence of a progenitor binary star in their centres, containing at least one white dwarf. This project is aimed at finding a significant "bipolarity-binarity" correlation within bipolar planetary nebulae. Further, the history of the mass ejection episodes will give clues to the common-envelope stage, still poorly understood.
    • In mid-2017 we started another research line in the field of white dwarfs: the study of post-planetary remnants around these stars, which can greatly benefit from our studies of accretion discs in cataclysmic variables.
    Principal investigator
    1. Many white dwarf stars show signs of having accreted smaller bodies, implying that they may host planetary systems. A small number of these systems contain gaseous debris discs, visible through emission lines. We found a stable 123.4-minute periodic variation in the strength and shape of the Ca II emission line profiles originating from the debris disc around the white dwarf SDSS J122859.93+104032.9. We interpret this short-period signal as the signature of a solid-body planetesimal held together by its internal strength. Results published in Science.
    2. Discovery of a giant bubble-like shell around M31N 2008–12a, the recurrent nova with the shortest eruption recurrence period (one year). Results published in Nature.
    3. A fast GTC/OSIRIS spectrophotometric study of the white dwarf WD 1145+017 has been published in Monthly Notices of the Royal Astronomical Society that reports confirmation of the evolution of the periodic transits that occur every 4.5 hours. The deepest transit detected to date has been modelled with six equally spaced fragments of the disrupting planetesimal.
    4. In 2018 an International Time Programme for follow-up of gravitational wave events was awarded (PI Jonker, SRON, The Netherlands). Several members of the projects are co-Is. Rodríguez-Gil will serve as chair on the Executive Committee.

    Related publications

    • The Pre-He White Dwarf in the Post-mass Transfer Binary EL CVn
      EL CVn is the prototype of a class of eclipsing binaries that consist of an A- or F-type main-sequence star and a hot, low-mass, pre-He white dwarf (pre-He WD), the stripped down remains of the former mass donor. Here we present the first direct detection and characterization of the spectrum of the pre-He WD in EL CVn that was made possible through
      Wang, Luqian et al.

      Advertised on:

      1
      2020
      Citations
      15
    • Absolute dimensions of the low-mass eclipsing binary system NSVS 10653195
      Context. Low-mass stars in eclipsing binary systems show radii larger and effective temperatures lower than theoretical stellar models predict for isolated stars with the same masses. Eclipsing binaries with low-mass components are hard to find due to their low luminosity. As a consequence, the analysis of the known low-mass eclipsing systems is
      Iglesias-Marzoa, Ramón et al.

      Advertised on:

      7
      2019
      Citations
      3
    • Short-period Variable Stars in Young Open Cluster Stock 8
      We present time-series photometry in the field of Stock 8 and identified 130 short-period variable stars. Twenty-eight main-sequence and 23 pre-main-sequence variables are found to be part of cluster Stock 8. The main-sequence variables are classified as slow pulsators of the B-type, β Cep, and δ Scuti stars. Fourteen main-sequence stars could be
      Lata, Sneh et al.

      Advertised on:

      8
      2019
      Citations
      7
    • The binary millisecond pulsar PSR J1023+0038 - II. Optical spectroscopy
      We present time-resolved optical spectroscopy of the `redback' binary millisecond pulsar system PSR J1023+0038 during both its radio pulsar (2009) and accretion disc states (2014 and 2016). We provide observational evidence for the companion star being heated during the disc state. We observe a spectral type change along the orbit, from ˜G5 to ˜F6
      Shahbaz, T. et al.

      Advertised on:

      9
      2019
      Citations
      16
    • The evolutionary status of Cataclysmic Variables: eclipse modelling of 15 systems
      We present measurements of the component masses in 15 Cataclysmic Variables (CVs) - 6 new estimates and 9 improved estimates. We provide new calibrations of the relationship between superhump period excess and mass ratio, and use this relation to estimate donor star masses for 225 superhumping CVs. With an increased sample of donor masses we
      McAllister, M. et al.

      Advertised on:

      7
      2019
      Citations
      55
    • A new study of the variable star population in the Hercules globular cluster (M13; NGC 6205)★
      We present the results from VI CCD time-series photometry of the globular cluster M13 (NGC 6205). From the Fourier decomposition of the light curves of RRab and RRc stars we found an average metallicity of [Fe/H]zw = -1.58 ± 0.09. The distance to the cluster was estimated as 7.1 ± 0.1 kpc from independent methods related to the variable star
      Deras, D. et al.

      Advertised on:

      6
      2019
      Citations
      27
    • A planetesimal orbiting within the debris disc around a white dwarf star
      Many white dwarf stars show signs of having accreted smaller bodies, implying that they may host planetary systems. A small number of these systems contain gaseous debris discs, visible through emission lines. We report a stable 123.4-minute periodic variation in the strength and shape of the Ca II emission line profiles originating from the debris
      Manser, C. J. et al.

      Advertised on:

      4
      2019
      Citations
      120
    • A recurrent nova super-remnant in the Andromeda galaxy
      The accretion of hydrogen onto a white dwarf star ignites a classical nova eruption1,2—a thermonuclear runaway in the accumulated envelope of gas, leading to luminosities up to a million times that of the Sun and a high-velocity mass ejection that produces a remnant shell (mainly consisting of insterstellar medium). Close to the upper mass limit of
      Darnley, M. J. et al.

      Advertised on:

      1
      2019
      Citations
      28
    • 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 56 known systems, only Gaia14aae undergoes complete eclipses of its central white dwarf, allowing the parameters of its stellar components to be
      Green, M. J. et al.

      Advertised on:

      5
      2019
      Citations
      12
    • The short orbital period binary star at the heart of the planetary nebula M 3-1★
      We present the discovery of a 3h5m orbital-period binary star at the heart of the planetary nebula M 3-1 - the shortest period photometrically variable central star known and second only to V458 Vul, in general. Combined modelling of light and radial velocity curves reveals both components to be close to Roche lobe filling, strongly indicating that
      Jones, D. et al.

      Advertised on:

      1
      2019
      Citations
      31
    • Evidence for mass accretion driven by spiral shocks onto the white dwarf in SDSS J123813.73-033933.0
      We present high-time-resolution photometry and phase-resolved spectroscopy of the short-period ({P_orb}= 80.52 min) cataclysmic variable SDSS J123813.73-033933.0, observed with the Hubble Space Telescope (HST), the Kepler/K2 mission, and the Very Large Telescope (VLT). We also report observations of the first detected superoutburst. SDSS J1238-0339
      Pala, A. F. et al.

      Advertised on:

      2
      2019
      Citations
      17
    • When nature tries to trick us. An eclipsing eccentric close binary superposed on the central star of the planetary nebula M 3-2
      Bipolar planetary nebulae (PNe) are thought to result from binary star interactions and, indeed, tens of binary central stars of PNe have been found, in particular using photometric time-series that allow for the detection of post-common envelope systems. Using photometry at the NTT in La Silla we have studied the bright object close to the centre
      Boffin, H. M. J. et al.

      Advertised on:

      11
      2018
      Citations
      12
    • First light with HiPERCAM on the GTC
      HiPERCAM is a quintuple-beam imager that saw first light on the 4.2 m William Herschel Telescope (WHT) in October 2017 and on the 10.4 m Gran Telescopio Canarias (GTC) in February 2018. The instrument uses re- imaging optics and 4 dichroic beamsplitters to record ugriz (300-1000 nm) images simultaneously on its five CCD cameras. The detectors in
      Dhillon, Vik et al.

      Advertised on:

      7
      2018
      Citations
      14
    • A Large Ground-based Observing Campaign of the Disintegrating Planet K2-22b
      We present 45 ground-based photometric observations of the K2-22 system collected between 2016 December and 2017 May, which we use to investigate the evolution of the transit of the disintegrating planet K2-22b. Last observed in early 2015, in these new observations we recover the transit at multiple epochs and measure a typical depth of
      Colón, Knicole D. et al.

      Advertised on:

      11
      2018
      Citations
      8
    • Fourier time lags in the dwarf nova SS Cygni
      To understand the physical processes governing accretion discs we can study active galactic nuclei (AGNs), X-ray binary systems (XRBs), and cataclysmic variables (CVs). It has been shown that XRBs and CVs show similar observational properties such as recurrent outbursts and aperiodic variability. The latter has been extensively studied for XRBs
      Aranzana, E. et al.

      Advertised on:

      12
      2018
      Citations
      6
    • The 1989 and 2015 outbursts of V404 Cygni: a global study of wind-related optical features
      The black hole transient V404 Cygni exhibited a bright outburst in June 2015 that was intensively followed over a wide range of wavelengths. Our team obtained high time resolution optical spectroscopy (! ˜ ! 90 s), which included a detailed coverage of the most active phase of the event. We present a data base consisting of 651 optical spectra
      Mata Sánchez, D. et al.

      Advertised on:

      12
      2018
      Citations
      26
    • Pulsations and eclipse-time analysis of HW Vir
      We analysed recent K2 data of the short-period eclipsing binary system HW Vir, which consists of a hot subdwarf-B type primary with an M-dwarf companion. We determined the mid-times of eclipses, calculated O-C diagrams, and an average shift of the secondary minimum. Our results show that the orbital period is stable within the errors over the
      Baran, A. S. et al.

      Advertised on:

      12
      2018
      Citations
      20
    • Fast spectrophotometry of WD 1145+017
      WD 1145+017 is currently the only white dwarf known to exhibit periodic transits of planetary debris as well as absorption lines from circumstellar gas. We present the first simultaneous fast optical spectrophotometry and broad-band photometry of the system, obtained with the Gran Telescopio Canarias (GTC) and the Liverpool Telescope, respectively
      Izquierdo, P. et al.

      Advertised on:

      11
      2018
      Citations
      29
    • The scatter of the M dwarf mass-radius relationship
      M dwarfs are prime targets in the hunt for habitable worlds around other stars. This is due to their abundance as well as their small radii and low masses and temperatures, which facilitate the detection of temperate, rocky planets in orbit around them. However, the fundamental properties of M dwarfs are difficult to constrain, often limiting our
      Parsons, S. G. et al.

      Advertised on:

      11
      2018
      Citations
      85
    • A 15.7-minAM CVn binary discovered in K2
      We present the discovery of SDSS J135154.46-064309.0, a short-period variable observed using 30-mincadence photometry in K2 Campaign 6. Follow-up spectroscopy and high-speed photometry support a classification as a new member of the rare class of ultracompact accreting binaries known as AM CVn stars. The spectroscopic orbital period of 15.65 ± 0.12
      Green, M. J. et al.

      Advertised on:

      7
      2018
      Citations
      20

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