J/MNRAS/546/G058 High-velocity X-ray sources (Zhao+, 2026)
A comprehensive search for high-velocity X-ray sources:
new compact object binary candidates in the Gaia era.
Zhao, Y., Gandhi, P., Knigge, C., Charles, P.A, Stern, D., Boorman P.,
Nuchvanichakul P., Dashwood Brown C., Buckley D.A.H.
<Mon. Not. R. Astron. Soc. 546, G058 (2026)>
=2026MNRAS.546ag058Z (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, X-ray ; X-ray sources
Keywords: binary: close - stars: black hole - stars: neutron -
supernova: general - X-rays: binaries
Abstract:
We perform a comprehensive search for high-velocity X-ray sources with
large X-ray/optical flux ratios (FX/FG), identifying candidates
for interacting black hole or neutron star binaries potentially
accelerated by supernova natal kicks. We cross-match X-ray points
sources from a variety of catalogues (Chandra, XMM-Newton, Swift and
eROSITA) with Gaia DR3. Using Gaia coordinates, parallaxes, and proper
motions, we compute peculiar velocities (vpec) relative to Galactic
disc rotation. Remaining agnostic about radial velocities (RVs), we
vary RVs to find the minimum possible vpec values (vpecmin).
Uncertainties on vpecmin are estimated via Monte Carlo resampling,
and we select X-ray sources that have 1 sigma lower limits on
vpecmin≥200km/s and high FX/FG values. We show that this velocity
threshold excludes most contaminants (e.g., cataclysmic variables and
active binaries) while retaining a sensible fraction of compact object
binaries, demonstrating that vpec could serve as an effective
indicator for the presence of a neutron star or black hole companion.
Our selection yields a sample of 2372 sources, from which we construct
a gold sample of 7 sources that have relatively well-constrained
astrometry and confident optical counterparts. Follow-up is necessary
to confirm and characterise their high-energy emission, as well as a
Galactic disc vs. halo origin.
Description:
Catalog of the high-velocity X-ray sources (HVXS) and the control
samples. The HVXS sample contains X-ray sources with 1 sigma lower
limit of minimum peculiar velocity greater than 200km/s and cleaned,
following the steps in Section 2.9; the control sample was established
following the same cleaning steps as the HVXS and then was taken to be
the complement to the HVXS sample (Section 2.11).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
hvxs.dat 267 2372 High-velocity X-ray sources (Sect 2.9)
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
I/352 : Distances to 1.47 billion stars in Gaia EDR3 (Bailer-Jones+, 2021)
IX/70 : Chandra Source Catalog Release 2 (CSC 2.1) (Evans+, 2024)
IX/59 : XMM-Newton Serendipitous Source Catalogue 4XMM-DR9 (Webb+, 2020)
IX/58 : 2SXPS Swift X-ray telescope point source catalogue (Evans+, 2020)
J/A+A/682/A34 : SRG/eROSITA all-sky survey catalogs (eRASS1) (Merloni+, 2024)
Byte-by-byte Description of file: hvxs.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Name X-ray designation
25- 43 A19 --- GaiaDR3 Gaia source_id
45- 56 F12.8 deg RAdeg X-ray right ascension (ICRS)
58- 69 F12.8 deg DEdeg X-ray declination (ICRS)
71- 90 F20.16 deg RAGdeg Gaia right ascension (ICRS) at Ep=2016.0
92-111 F20.16 deg DEGdeg Gaia declination (ICRS) at Ep=2016.0
113-121 E9.3 arcsec Sep X-ray/Gaia angular separation
123-126 F4.2 arcsec PosErr X-ray error radius (1 Mahalanobis radius)
128-135 E8.2 kpc Dist Distance used for computing velocities
137-144 E8.2 kpc e_Dist 1-sigma lower uncertainty on Dist
146-153 E8.2 kpc E_Dist 1-sigma upper uncertainty on Dist
155-163 E9.3 mW/m2 FX X-ray flux
165-173 E9.3 mW/m2 e_FX Uncertainty on FX
175-183 F9.6 --- Gmag Gaia G-band magnitude
185-195 F11.8 --- BP-RP Gaia Bp-Rp colour
197-205 E9.3 --- FX-FG X-ray/Gaia G band flux ratio
207-215 E9.3 --- e_FX-FG Uncertainty on FX-FG
217-224 F8.3 km/s gamma-min Systemic RV corresponding to vpec-min
226-231 F6.3 km/s e_gamma-min 1-sigma lower uncertainty on gamma-min
233-238 F6.3 km/s E_gamma-min 1-sigma upper uncertainty on gamma-min
240-247 F8.3 km/s vpec-min Minimum peculiar velocity
249-256 F8.3 km/s e_vpec-min 1-sigma lower uncertainty on vpec-min
258-265 F8.3 km/s E_vpec-min 1-sigma upper uncertainty on vpec-min
267 A1 --- Quality [01234567] Quality flag (see Sect 2.10) (1)
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Note (1): Quality flag as follows:
0 = all OK
1 = |dinv-d21|/db21≤0.2 : db21 within 20% of dmv
2 = ϖ/sigmaϖ≥5 : ϖ uncertainty less than 20%
3 = |dinv-d21|/db21≤0.2 : db21 within 20% of dmv and
ϖ/sigmaϖ≥5 : ϖ uncertainty less than 20%
4 = δx.b≤rerr,x : Gaia counterpart within the 1σ X-ray error
circle
5 = δx.b≤rerr,x : Gaia counterpart within the 1σ X-ray error
circle AND |dinv-d21|/db21≤0.2: db21 within 20% of dmv
6 = δx.b≤rerr,x : Gaia counterpart within the 1σ X-ray error
circle AND ϖ/sigmaϖ≥5 : ϖ uncertainty less than 20%
7 = δx.b≤rerr,x : Gaia counterpart within the 1σ X-ray error
circle AND ϖ/sigmaϖ≥5 : ϖ uncertainty less than 20%
AND |dinv-d21|/db21≤0.2 : db21 within 20% of dmv
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Acknowledgements:
Yue Zhao, yue.zhao(at)soton.ac.uk
(End) Patricia Vannier [CDS] 14-Jan-2026