Dynamical confirmation of a black hole in the X-ray transient Swift J1727.8−1613
Aug 23, 20247 pages
Published in:
- Astron.Astrophys. 693 (2025) A129,
- Astron.Astrophys. 693 (2025) A129
- Published: Jan 1, 2025
e-Print:
- 2408.13310 [astro-ph.HE]
View in:
Citations per year
Abstract: (EDP Sciences)
The X-ray transient Swift J1727.8−1613 ended its 10-month discovery outburst in June of 2024, when it reached an optical brightness comparable to pre-discovery magnitudes. With the aim of performing a dynamical study, we launched an optical spectroscopy campaign with the GTC telescope. We detected the companion star and constructed its radial velocity curve, yielding a binary orbital period of Porb = 10.8038 ± 0.0010 h and a radial velocity semi-amplitude of K2 = 390 ± 4 km s−1. This results in a mass function of f(M1) = 2.77 ± 0.09 M⊙. Combined with constraints on the binary inclination, it sets a lower limit on the compact object mass of M1 > 3.12 ± 0.10 M⊙, dynamically confirming the black hole nature of the accretor. A comparison of the average spectrum in the rest frame of the companion with synthetic stellar templates supports a K4V donor that is partially (74%) veiled by the accretion disc. A refined distance measurement of 3.4 ± 0.3 kpc, together with the astrometric proper motion and the systemic velocity derived from the radial velocity curve (γ = 181 ± 4 km s−1), supports a natal kick velocity of vkick = 210−50+40 km s−1, at the upper end of the observed distribution.Key words: accretion, accretion disks / stars: black holes / stars: individual: J1727.8−1613 / X-rays: binariesNote:
- 6 (+2 appendix) pages, 3 (+1) figures, 2 tables. Submitted to A&A on the 22th of August 2024, accepted on the 12th of November 2024. Updated final distance values after fixing a bug affecting the spectroscopic distance determination
References(59)
Figures(4)