Black holes, neutron stars, white dwarfs and their local environment

    General
    Description

    Accreting black-holes and neutron stars in X-ray binaries provide an ideal laboratory for exploring the physics of compact objects, yielding not only confirmation of the existence of stellar mass black holes via dynamical mass measurements, but also the best opportunity for probing high-gravity environments and the physics of accretion; the most efficient form of energy production known. The latter is an essential physical process to understand the universe, playing a crucial role in galactic and extra-galactic astronomy.

    This project has the following scientific goals:

    - X-ray binaries offer the opportunity to study accretion as its best, since their relevant changes occur on convenient time-scales for human beings. This project focuses on the universal relation between black-hole accretion and ejection processes in the form of collimated jets and wide-angle winds. We will focus on the general properties and astrophysical impact of the cold optical accretion disc wind that our group has discovered. We want to understand how frequent these winds are, which is their impact in the black-hole accretion process, and what is their relation with jets and hot X-ray winds. Likewise, we carry out very detailed X-ray spectral studies on the different accretion states and geometries and their evolution with luminosity.

    - We want to define the mass distribution of black-holes and neutron stars. Thus, we continue our contribution to one of the fundamental experiments in modern astrophysics by measuring dynamical masses in X-ray binaries. We expect to significantly improve the observed mass distribution of compact objects. This will allow testing models of supernovae explosions and close binary evolution as well as setting constraints on the equation of state of nuclear matter. We will measure masses in newly discovered or known transient X-ray binaries. In addition, we will also search for the large number of dormant X-ray binaries expected in the Galaxy and suitable for dynamical studies.

    - To study the structure of accretion discs in different energy bands (optical-X rays). The high energy spectral distribution and time variability during outburst is important to constrain the eruption models and accretion disc properties (e.g. radius of advective disc) as well as to constrain the contribution of the jet to the optical and infrared emission of the system.

     

    see group web page:  https://research.iac.es/proyecto/compactos/pages/en/introduction.php

    Principal investigator
    1. Our team has led the multi-wavelength study of the two 2015 outbursts of the Black-hole transient V404 Cyg. In 2018, we published a global paper which include all the spectroscopy taken during the 1989 and 2015 campaigns.
    2. We have presented solid evidence for the presence of very similar wind to that found in V404 Cyg in another black hole transient, V4641 Sgr.
    3. We published the final paper as well as a pilot study on a novel method developed by the group. It aims at discovering and measuring masses of black hole transient in quiescence. This method has the potential of increasing the known population of these systems by a factor of three.
    4. We measured the mass of the neutron star in PSR J2215+5135 and found it is one of the heaviest known to date.
    5. We presented the first detailed study on the ultra-compact system SLX 1737-282.

    Related publications

    • Evidence of coupling between the thermal and nonthermal emission in the gamma-ray binary LS I +61 303
      The gamma-ray binary LS I +61 303 is composed of a Be star and a compact companion orbiting in an eccentric orbit. Variable flux modulated with the orbital period of ~26.5 d has been detected from radio to very high-energy gamma rays. In addition, the system presents a superorbital variability of the phase and amplitude of the radio outbursts with
      Paredes-Fortuny, X. et al.

      Advertised on:

      3
      2015
      Citations
      19
    • Mass constraints to Sco X-1 from Bowen fluorescence and deep near-infrared spectroscopy
      More than 50 years after the dawn of X-ray astronomy, the dynamical parameters of the prototypical X-ray binary Sco X-1 are still unknown. We combine a Monte Carlo analysis, which includes all the previously known orbital parameters of the system, along with the K-correction to set dynamical constraints to the masses of the compact object (M1 1.73
      Acosta Pulido, J. A. et al.

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      4
      2015
      Citations
      19
    • Precision Ephemerides for Gravitational-wave Searches. I. Sco X-1
      Rapidly rotating neutron stars are the only candidates for persistent high-frequency gravitational wave emission, for which a targeted search can be performed based on the spin period measured from electromagnetic (e.g., radio and X-ray) observations. The principal factor determining the sensitivity of such searches is the measurement precision of
      Galloway, D. K. et al.

      Advertised on:

      4
      2014
      Citations
      34
    • Chemical abundances of the secondary star in the neutron star X-ray binary Cygnus X-2
      We present Utrecht Echelle Spectrograph@William Herschel Telescope high-resolution spectra of the low-mass X-ray binary (LMXB) Cygnus X-2. We have derived the stellar parameters of the secondary star using χ2 minimization procedure, and taking into account any possible veiling from the accretion disc. We determine a metallicity higher than solar (
      Suárez-Andrés, L. et al.

      Advertised on:

      3
      2015
      Citations
      8
    • Polarimetric and spectroscopic optical observations of the ultra-compact X-ray binary 4U 0614+091
      Aims: We present a polarimetric and spectroscopic study of the persistent ultra-compact X-ray binary 4U 0614+091 aimed at searching for the emission of a relativistic particle jet and at unveiling the orbital period Porb of the system. Methods: We obtained r-band polarimetric observations with the Telescopio Nazionale Galileo (TNG) equipped with
      Baglio, M. C. et al.

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      12
      2014
      Citations
      16
    • Stellar occultation by (119951) 2002 KX14 on April 26, 2012
      Context. Trans-Neptunian objects (TNOs) are important bodies, but very little is known about their basic physical properties such as size, density, and albedo. Aims: We intend to determine sizes, albedos, and even densities of a good sample of TNOs, especially those of the largest TNOs because they can be studied the best with different
      Alvarez-Candal, A. et al.

      Advertised on:

      11
      2014
      Citations
      14
    • Suppression of cooling by strong magnetic fields in white dwarf stars
      Isolated cool white dwarf stars more often have strong magnetic fields than young, hotter white dwarfs, which has been a puzzle because magnetic fields are expected to decay with time but a cool surface suggests that the star is old. In addition, some white dwarfs with strong fields vary in brightness as they rotate, which has been variously
      Valyavin, G. et al.

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      11
      2014
      Citations
      55
    • A Strongly Heated Neutron Star in the Transient Z Source MAXI J0556-332
      We present Chandra, XMM-Newton, and Swift observations of the quiescent neutron star in the transient low-mass X-ray binary MAXI J0556-332. Observations of the source made during outburst (with the Rossi X-ray Timing Explorer) reveal tracks in its X-ray color-color and hardness-intensity diagrams that closely resemble those of the neutron-star Z
      Homan, J. et al.

      Advertised on:

      11
      2014
      Citations
      51
    • Multiwavelength observations of the black hole transient Swift J1745-26 during the outburst decay
      We characterized the broad-band X-ray spectra of Swift J1745-26 during the decay of the 2013 outburst using INTEGRAL ISGRI, JEM-X and Swift XRT. The X-ray evolution is compared to the evolution in optical and radio. We fit the X-ray spectra with phenomenological and Comptonization models. We discuss possible scenarios for the physical origin of an
      Kalemci, E. et al.

      Advertised on:

      12
      2014
      Citations
      13
    • A mass of less than 15 solar masses for the black hole in an ultraluminous X-ray source
      Most ultraluminous X-ray sources have a typical set of properties not seen in Galactic stellar-mass black holes. They have luminosities of more than 3 × 1039 ergs per second, unusually soft X-ray components (with a typical temperature of less than about 0.3 kiloelectronvolts) and a characteristic downturn in their spectra above about 5
      Motch, C. et al.

      Advertised on:

      10
      2014
      Citations
      202
    • X-Ray States of Redback Millisecond Pulsars
      Compact binary millisecond pulsars with main-sequence donors, often referred to as "redbacks," constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100
      Linares, M.

      Advertised on:

      11
      2014
      Citations
      86
    • Discovery of the Near-infrared Counterpart to the Luminous Neutron-star Low-mass X-Ray Binary GX 3+1
      Using the High Resolution Camera on board the Chandra X-ray Observatory, we have measured an accurate position for the bright persistent neutron star X-ray binary and atoll source GX 3+1. At a location that is consistent with this new position, we have discovered the near-infrared (NIR) counterpart to GX 3+1 in images taken with the PANIC and
      van den Berg, Maureen et al.

      Advertised on:

      10
      2014
      Citations
      11
    • Unveiling the redback nature of the low-mass X-ray binary XSS J1227.0-4859 through optical observations
      The peculiar low-mass X-ray binary XSS J12270-4859, associated with the Fermi/LAT source 2FGL J1227.7-4853, was in an X-ray, gamma-ray and optical low-luminosity persistent state for about a decade until the end of 2012, when it entered into the dimmest state ever observed. The nature of the compact object has been controversial until the detection
      de Martino, D. et al.

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      11
      2014
      Citations
      46
    • Roche tomography of cataclysmic variables - VI. Differential rotation of AE Aqr - not tidally locked!
      We present Roche tomograms of the K4V secondary star in the cataclysmic variable AE Aqr, reconstructed from two data sets taken 9 d apart, and measure the differential rotation of the stellar surface. The tomograms show many large, cool starspots, including a large high-latitude spot and a prominent appendage down the trailing hemisphere. We find
      Hill, C. A. et al.

      Advertised on:

      10
      2014
      Citations
      18
    • Spectral state transitions of the Ultraluminous X-ray Source IC 342 X-1
      We observed the Ultraluminous X-ray Source (ULX) IC 342 X-1 simultaneously in X-ray and radio with Chandra and the JVLA to investigate previously reported unresolved radio emission coincident with the ULX. The Chandra data reveal a spectrum that is much softer than observed previously and is well modelled by a thermal accretion disc spectrum. No
      Marlowe, H. et al.

      Advertised on:

      10
      2014
      Citations
      16
    • Swift J1357.2-0933: the faintest black hole?
      Swift J1357.2-0933 is a confirmed very faint black hole X-ray transient and has a short estimated orbital period of 2.8 h. We observed Swift J1357.2-0933 for ˜50 ks with XMM-Newton in 2013 July during its quiescent state. The source is clearly detected at a 0.5-10 keV unabsorbed flux of ˜3 × 10-15 erg cm-2 s-1. If the source is located at a
      Armas Padilla, M. et al.

      Advertised on:

      10
      2014
      Citations
      35
    • Absorption at the dust sublimation radius and the dichotomy between X-ray and optical classification in the Seyfert galaxy H0557-385
      In this work, the analysis of multi-epoch (1995-2010) X-ray observations of the Seyfert 1 galaxy H0557-385 is presented. The wealth of data presented in this analysis show that the source exhibits dramatic spectral variability, from a typical unabsorbed Seyfert 1 type spectrum to a Compton-thin absorbed state, on time-scales of ˜5 yr. This extreme
      Coffey, D. et al.

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      9
      2014
      Citations
      8
    • Broad iron emission line and kilohertz quasi-periodic oscillations in the neutron star system 4U 1636-53
      Both the broad iron (Fe) line and the frequency of the kilohertz quasi-periodic oscillations (kHz QPOs) in neutron star low-mass X-ray binaries (LMXBs) can potentially provide independent measures of the inner radius of the accretion disc. We use XMM-Newton and simultaneous Rossi X-ray Timing Explorer observations of the LMXB 4U 1636-53 to test
      Sanna, A. et al.

      Advertised on:

      4
      2014
      Citations
      11
    • Discovery of X-Ray Emission from the First Be/Black Hole System
      MWC 656 (=HD 215227) was recently discovered to be the first binary system composed of a Be star and a black hole (BH). We observed it with XMM-Newton, and detected a faint X-ray source compatible with the position of the optical star, thus proving it to be the first Be/BH X-ray binary. The spectrum analysis requires a model fit with two components
      Munar-Adrover, P. et al.

      Advertised on:

      5
      2014
      Citations
      27

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