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.

    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

    • The Observed Mass Distribution of Galactic Black Hole LMXBs Is Biased against Massive Black Holes

      The discovery of gravitational-wave radiation from merging black holes (BHs) also uncovered BHs with masses in the range of ≍20-160 M⊙. In contrast, the most massive Galactic stellar-mass BH currently known has a mass of ≍21 M⊙. While low-mass X-ray binaries (LMXBs) will never independently evolve into a binary BH system, and binary evolution

      Jonker, Peter G. et al.

      Advertised on:

      11
      2021
    • Searching for Fermi GRB optical counterparts with the prototype Gravitational-wave Optical Transient Observer (GOTO)

      The typical detection rate of ~1 gamma-ray burst (GRB) per day by the Fermi Gamma-ray Burst Monitor (GBM) provides a valuable opportunity to further our understanding of GRB physics. However, the large uncertainty of the Fermi localization typically prevents rapid identification of multiwavelength counterparts. We report the follow-up of 93 Fermi

      Mong, Y. -L. et al.

      Advertised on:

      11
      2021
    • A new radio census of neutron star X-ray binaries

      We report new radio observations of a sample of 36 neutron star (NS) X-ray binaries, more than doubling the sample in the literature observed at current-day sensitivities. These sources include 13 weakly magnetized (B < 1010 G) and 23 strongly magnetized (B ≥ 1010 G) NSs. 16 of the latter category reside in high-mass X-ray binaries, of which only

      van den Eijnden, J. et al.

      Advertised on:

      11
      2021
    • Failed-transition outbursts in black hole low-mass X-ray binaries

      Black hole low-mass X-ray binaries (BH LMXBs) evolve in a similar way during outburst. Based on the X-ray spectrum and variability, this evolution can be divided into three canonical states: low/hard, intermediate, and high/soft state. BH LMXBs evolve from the low/hard to the high/soft state through the intermediate state in some outbursts (here

      Alabarta, K. et al.

      Advertised on:

      11
      2021
    • Optical photometry of two transitional millisecond pulsars in the radio pulsar state

      We present ULTRACAM multiband optical photometry of two transitional millisecond pulsars (tMSPs), PSR J1023+0038 and PSR J1227-4853, taken while both were in their radio pulsar states. The light curves show significant asymmetry about the flux maxima in all observed bands, suggesting an asymmetric source of heating in the system. We model the light

      Stringer, J. G. et al.

      Advertised on:

      10
      2021
    • X-ray observations of two candidate symbiotic binaries in the galactic bulge

      This paper analyses X-ray observations by the Chandra X-ray Observatory of CXOGBS J174614.3-321949 (CXB3) and CXOGBS J173620.2-293338 (CX332), two symbiotic binary star candidates identified by the Galactic Bulge Survey. Using new Chandra observations, we improved their X-ray positional uncertainties to 0.24 and 0.92 arcsec, respectively

      Wetuski, Joshua et al.

      Advertised on:

      10
      2021
    • Gaia Early Data Release 3. Gaia photometric science alerts

      Context. Since July 2014, the Gaia mission has been engaged in a high-spatial-resolution, time-resolved, precise, accurate astrometric, and photometric survey of the entire sky. Aims: We present the Gaia Science Alerts project, which has been in operation since 1 June 2016. We describe the system which has been developed to enable the discovery and

      Hodgkin, S. T. et al.

      Advertised on:

      8
      2021
    • Multiwavelength observations reveal a faint candidate black hole X-ray binary in IGR J17285-2922

      IGR J17285-2922 is a known X-ray binary with a low peak 2-10 keV X-ray luminosity of ~ 1036 erg s-1 during outburst. IGR J17285-2922 exhibited two outbursts in 2003 and 2010 and went into outburst again in 2019. We have monitored this ~ 4-month long 2019 outburst with Swift in X-ray and the Very Large Array in radio. We have also obtained four

      Stoop, M. et al.

      Advertised on:

      10
      2021
    • HiPERCAM: a quintuple-beam, high-speed optical imager on the 10.4-m Gran Telescopio Canarias

      HiPERCAM is a portable, quintuple-beam optical imager that saw first light on the 10.4-m Gran Telescopio Canarias (GTC) in 2018. The instrument uses re-imaging optics and four dichroic beamsplitters to record $u_{\rm s}\, g_{\rm s}\, r_{\rm s}\, i_{\rm s}\, z_{\rm s}$ (320-1060 nm) images simultaneously on its five CCD cameras, each of 3.1-arcmin

      Dhillon, V. S. et al.

      Advertised on:

      10
      2021
    • Dynamical confirmation of a stellar mass black hole in the transient X-ray dipping binary MAXI J1305-704

      MAXI J1305-704 has been proposed as a high-inclination candidate black hole X-ray binary in view of its X-ray properties and dipping behaviour during outburst. We present photometric and spectroscopic observations of the source in quiescence that allow us to reveal the ellipsoidal modulation of the companion star and absorption features consistent

      Mata Sánchez, D. et al.

      Advertised on:

      9
      2021
    • Measuring fundamental jet properties with multiwavelength fast timing of the black hole X-ray binary MAXI J1820+070

      We present multiwavelength fast timing observations of the black hole X-ray binary MAXI J1820+070 (ASASSN-18ey), taken with the Karl G. Jansky Very Large Array (VLA), Atacama Large Millimeter/Sub-Millimeter Array (ALMA), Very Large Telescope (VLT), New Technology Telescope (NTT), Neutron Star Interior Composition Explorer (NICER), and XMM-Newton

      Tetarenko, A. J. et al.

      Advertised on:

      7
      2021
    • The evolution of rapid optical/X-ray timing correlations in the initial hard state of MAXI J1820+070

      We report on a multiepoch campaign of rapid optical/X-ray timing observations of the superbright 2018 outburst of MAXI J1820+070, a black hole low-mass X-ray binary system. The observations spanned 80 d in the initial hard state and were taken with NTT/ULTRACAM and GTC/HiPERCAM in the optical (usgsrsiszs filters at time resolutions of 8-300 Hz) and

      Paice, J. A. et al.

      Advertised on:

      8
      2021
    • Light-curve classification with recurrent neural networks for GOTO: dealing with imbalanced data

      The advent of wide-field sky surveys has led to the growth of transient and variable source discoveries. The data deluge produced by these surveys has necessitated the use of machine learning (ML) and deep learning (DL) algorithms to sift through the vast incoming data stream. A problem that arises in real-world applications of learning algorithms

      Burhanudin, U. F. et al.

      Advertised on:

      8
      2021
    • Optical nebular emission following the most luminous outburst of Aquila X-1

      Aquila X-1 is a prototypical neutron star low mass X-ray binary and one of the most studied X-ray transients. We present optical spectroscopy obtained with the Gran Telescopio Canarias (10.4 m) during the 2016 outburst, the brightest recorded in recent times and which showed a standard evolution with hard and soft accretion states. Our dataset

      Panizo-Espinar, G. et al.

      Advertised on:

      6
      2021
    • Processing GOTO survey data with the Rubin Observatory LSST Science Pipelines II: Forced Photometry and lightcurves

      We have adapted the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) Science Pipelines to process data from the Gravitational-wave Optical Transient Observer (GOTO) prototype. In this paper, we describe how we used the LSST Science Pipelines to conduct forced photometry measurements on nightly GOTO data. By comparing the photometry

      Makrygianni, L. et al.

      Advertised on:

      6
      2021
    • X-ray binary accretion states in active galactic nuclei? Sensing the accretion disc of supermassive black holes with mid-infrared nebular lines

      Accretion states, which are universally observed in stellar mass black holes in X-ray binaries, might be expected in active galactic nuclei (AGN). This is the case at low luminosities, when the jet-corona coupling dominates the energy output in both populations. Previous attempts to extend this framework to a wider AGN population have been

      Fernández-Ontiveros, Juan A. et al.

      Advertised on:

      7
      2021
    • Evidence of intra-binary shock emission from the redback pulsar PSR J1048+2339

      We present simultaneous multiwavelength observations of the 4.66 ms redback pulsar PSR J1048+2339. We performed phase-resolved spectroscopy with the Very Large Telescope (VLT) searching for signatures of a residual accretion disk or intra-binary shock emission, constraining the companion radial velocity semi-amplitude (K2), and estimating the

      Miraval Zanon, A. et al.

      Advertised on:

      5
      2021
    • Dips and eclipses in the X-ray binary Swift J1858.6-0814 observed with NICER

      We present the discovery of eclipses in the X-ray light curves of the X-ray binary Swift J1858.6-0814. From these, we find an orbital period of $P=76841.3_{-1.4}^{+1.3}$ s (≍21.3 h) and an eclipse duration of $t_{\rm ec}=4098_{-18}^{+17}$ s (≍1.14 h). We also find several absorption dips during the pre-eclipse phase. From the eclipse duration to

      Buisson, D. J. K. et al.

      Advertised on:

      6
      2021
    • Transient-optimized real-bogus classification with Bayesian convolutional neural networks - sifting the GOTO candidate stream

      Large-scale sky surveys have played a transformative role in our understanding of astrophysical transients, only made possible by increasingly powerful machine learning-based filtering to accurately sift through the vast quantities of incoming data generated. In this paper, we present a new real-bogus classifier based on a Bayesian convolutional

      Killestein, T. L. et al.

      Advertised on:

      5
      2021
    • Exploring the tilted accretion disc of AQ Men with TESS

      AQ Men is a nova-like variable that is presumed to have a tilted, precessing accretion disc. Grazing eclipses in this system have been speculated to be useful in exploring the geometry of its accretion disc. In this work, we analysed Transiting Exoplanet Survey Satellite (TESS) observations of AQ Men, which provide the best light curve of this

      Iłkiewicz, Krystian et al.

      Advertised on:

      5
      2021

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