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A period-dependent spatial scatter of Galactic black hole transients

A period-dependent spatial scatter of Galactic black hole transients
A period-dependent spatial scatter of Galactic black hole transients
There remain significant uncertainties in the origin and evolution of black holes in binary systems, in particular regarding their birth sites and the influence of natal kicks. These are long-standing issues, but their debate has been reinvigorated in the era of gravitational wave detections and the improving precision of astrometric measurements. Using recent and archival characterization of Galactic black hole X-ray binaries (BHXBs), we report here an apparent anticorrelation between Porb (system orbital periods) and scatter in z (elevation above the Galactic plane). The absence of long-period sources at high z is not an obvious observational bias, and two possible explanatory scenarios are qualitatively explored: (1) a disc origin for BHXBs followed by natal kicks producing the scatter in z⁠, with only the tightest binaries preferentially surviving strong kicks; and (2) a halo origin, with Porb shortening through dynamical interactions in globular clusters (GCs). For the latter case, we show a correspondence in z-scatter between BHXBs and the GCs with most compact core radii of <0.1 pc. However, the known absence of outbursting BHXB transients within Galactic GCs remains puzzling in this case, in contrast to the multitude of known GC neutron star XRBs. These results provide an interesting observational constraint for any black hole binary evolutionary model to satisfy.
1745-3925
L22-L27
Gandhi, P.
5bc3b5af-42b0-4dd8-8f1f-f74048d4d4a9
Rao, A.
48e0dfb7-cd0d-4055-a40f-b5cab3789bb4
Charles, P.A.
0429b380-0754-4dc1-8def-885c7fa6a086
Belczynski, K.
1c9afedb-121c-4151-af65-939932c3f4c5
Maccarone, T.J.
5d8ee27f-a174-424c-b3b7-a6739bfeea50
Arur, K.
c5315487-8445-4240-b87f-c64f3ace724d
Corral-Santana, J.M.
fb4e6141-b9db-4962-a80e-c040783bd902
Gandhi, P.
5bc3b5af-42b0-4dd8-8f1f-f74048d4d4a9
Rao, A.
48e0dfb7-cd0d-4055-a40f-b5cab3789bb4
Charles, P.A.
0429b380-0754-4dc1-8def-885c7fa6a086
Belczynski, K.
1c9afedb-121c-4151-af65-939932c3f4c5
Maccarone, T.J.
5d8ee27f-a174-424c-b3b7-a6739bfeea50
Arur, K.
c5315487-8445-4240-b87f-c64f3ace724d
Corral-Santana, J.M.
fb4e6141-b9db-4962-a80e-c040783bd902

Gandhi, P., Rao, A., Charles, P.A., Belczynski, K., Maccarone, T.J., Arur, K. and Corral-Santana, J.M. (2020) A period-dependent spatial scatter of Galactic black hole transients. Monthly Notices of the Royal Astronomical Society: Letters, 496 (1), L22-L27. (doi:10.1093/mnrasl/slaa081).

Record type: Article

Abstract

There remain significant uncertainties in the origin and evolution of black holes in binary systems, in particular regarding their birth sites and the influence of natal kicks. These are long-standing issues, but their debate has been reinvigorated in the era of gravitational wave detections and the improving precision of astrometric measurements. Using recent and archival characterization of Galactic black hole X-ray binaries (BHXBs), we report here an apparent anticorrelation between Porb (system orbital periods) and scatter in z (elevation above the Galactic plane). The absence of long-period sources at high z is not an obvious observational bias, and two possible explanatory scenarios are qualitatively explored: (1) a disc origin for BHXBs followed by natal kicks producing the scatter in z⁠, with only the tightest binaries preferentially surviving strong kicks; and (2) a halo origin, with Porb shortening through dynamical interactions in globular clusters (GCs). For the latter case, we show a correspondence in z-scatter between BHXBs and the GCs with most compact core radii of <0.1 pc. However, the known absence of outbursting BHXB transients within Galactic GCs remains puzzling in this case, in contrast to the multitude of known GC neutron star XRBs. These results provide an interesting observational constraint for any black hole binary evolutionary model to satisfy.

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A period-dependent spatial scatter of Galactic black hole transients - Accepted Manuscript
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Accepted/In Press date: 29 April 2020
e-pub ahead of print date: 7 May 2020
Published date: July 2020

Identifiers

Local EPrints ID: 442907
URI: http://eprints.soton.ac.uk/id/eprint/442907
ISSN: 1745-3925
PURE UUID: 0be0a74f-8f25-4815-84fe-22daa752986e
ORCID for P. Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

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Date deposited: 31 Jul 2020 16:30
Last modified: 07 Oct 2020 02:06

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Contributors

Author: P. Gandhi ORCID iD
Author: A. Rao
Author: P.A. Charles
Author: K. Belczynski
Author: T.J. Maccarone
Author: K. Arur
Author: J.M. Corral-Santana

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