Simultaneous optical and near-IR photometry of 4U 1957+115 - a missing secondary star

Abstract

We report the results of quasi-simultaneous optical and NIR photometry of the low-mass X-ray binary, 4U 1957+115. Our observations cover B, V, R, I, J, H and K-bands and additional time-series NIR photometry. We measure a spectral energy distribution, which can be modelled using a standard multi-temperature accretion disc, where the disc temperature and radius follow a power-law relation. Standard accretion disc theory predicts the power law exponent to be -3/4, and this yields, perhaps surprisingly, acceptable fits to our SED. Given that the source is a persistent X-ray source, it is however likely that the accretion disc temperature distribution is produced by X-ray heating, regardless of its radial dependence. Furthermore, we find no evidence for any emission from the secondary star at any wavelength. However, adding a secondary component to our model allows us to derive a 99\% lower limit of 14 or 15 kpc based on Monte Carlo simulations and using either an evolved K2 or G2V secondary star respectively. In $>$60\% of cases the distance is $>$80kpc. Such large distances favor models with a massive ($>$15 M${}_{\odot }$) black hole primary. Our quasi-simultaneous J and V-band time-series photometry, together with the SED, reveals that the optical/NIR emission must originate in the same region i.e. the accretion disc. The likely extreme mass ratio supports suggestions that the accretion disc must be precessing which, depending on the length of the precession period, could play a major part in explaining the variety of optical light curve shapes obtained over the last two decades.

arXiv comment7 pages, 4 figures, accepted for publication in MNRAS

References in corpus (20)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The Donor Stars of Cataclysmic Variables
• X-ray irradiation in low mass binary systems
• Global optical/infrared - X-ray correlations in X-ray binaries: quantifying disc and jet contributions
• Northern JHK Standard Stars for Array Detectors
• Revisiting a fundamental test of the disc instability model for X-ray binaries
• Testing the jet quenching paradigm with an ultradeep observation of a steadily soft state black hole
• The Evolving Accretion Disc in the Black Hole X-ray Transient XTE J1859+226
• Suzaku Observations of 4U 1957+11: Potentially the Most Rapidly Spinning Black Hole in (the Halo of) the Galaxy
• Disk Dominated States of 4U 1957+11: Chandra, XMM, and RXTE Observations of Ostensibly the Most Rapidly Spinning Galactic Black Hole
• Outbursts of Irradiated Accretion Discs
• Multiwavelength Observations of EXO 0748--676 -- II. Emission Line Behavior
• On the multi-periodicities in the X-ray dipper XB 1916-053
• 4U 1957+11: a persistent low-mass X-ray binary and black-hole candidate in the high state?
• On the enigmatic X-ray Source V1408 Aql (=4U 1957+11)
• A long-term optical - X-ray correlation in 4U 1957+11
• A 420 day X-ray/optical modulation and extended X-ray dips in the short-period transient Swift J1753.5-0127
• The Optical Orbital Light Curve of the Low-mass X-ray Binary V1408 Aquilae (= 4U 1957+115)
• The origin of the tilted disk in the low mass X-ray binary GR Mus (XB 1254-690)
• Light Curve Morphology Study of UW CrB -- Evidence for a 5 d Superorbital Period

Cited by in corpus (4)

• BlackCAT: A catalogue of stellar-mass black holes in X-ray transients
• The Case for a Low Mass Black Hole in the Low Mass X-ray Binary V1408 Aquilae (= 4U 1957+115)
• NICER/NuSTAR Characterization of 4U 1957+11: A Near Maximally Spinning Black Hole Potentially in the Mass Gap
• Optical polarization signatures of black hole X-ray binaries