TIC 378898110: a bright, short-period AM CVn binary in TESS
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Published version
Date
2023-11-09
Authors
Green, Matthew J.
Hermes, J.J.
Barlow, Brad N.
Marsh, T.R.
Pelisoli, Ingrid
Gänsicke, Boris T.
Kaiser, Ben C.
Romero, Alejandra
Amaral, Larissa Antunes
Corcoran, Kyle
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Published version
OA Version
Citation
M.J. Green, J.J. Hermes, B.N. Barlow, T.R. Marsh, I. Pelisoli, B.T. Gänsicke, B.C. Kaiser, A. Romero, L.A. Amaral, K. Corcoran, D. Grupe, M.R. Kennedy, S.O. Kepler, J. Munday, R.P. Ashley, A.S. Baran, E. Breedt, A.J. Brown, V.S. Dhillon, M.J. Dyer, P. Kerry, G.W. King, S.P. Littlefair, S.G. Parsons, D.I. Sahman. 2023. "TIC 378898110: A bright, short-period AM CVn binary in <i>TESS</i>" Monthly Notices of the Royal Astronomical Society, Volume 527, Issue 2, pp.3445-3458. https://doi.org/10.1093/mnras/stad3412
Abstract
AM CVn-type systems are ultracompact, helium-accreting binary systems that are evolutionarily linked to the progenitors of thermonuclear supernovae and are expected to be strong Galactic sources of gravitational waves detectable to upcoming space-based interferometers. AM CVn binaries with orbital periods ≲20–23 min exist in a constant high state with a permanently ionized accretion disc. We present the discovery of TIC 378898110, a bright (G = 14.3 mag), nearby (309.3 ± 1.8 pc), high-state AM CVn binary discovered in TESS two-minute-cadence photometry. At optical wavelengths, this is the third-brightest AM CVn binary known. The photometry of the system shows a 23.07172(6) min periodicity, which is likely to be the ‘superhump’ period and implies an orbital period in the range 22–23 min. There is no detectable spectroscopic variability. The system underwent an unusual, year-long brightening event during which the dominant photometric period changed to a shorter period (constrained to 20.5 ± 2.0 min), which we suggest may be evidence for the onset of disc-edge eclipses. The estimated mass transfer rate, $\log (\dot{M} / \mathrm{M_\odot } \, \mathrm{yr}^{-1}) = -6.8 \pm 1.0$, is unusually high and may suggest a high-mass or thermally inflated donor. The binary is detected as an X-ray source, with a flux of $9.2 ^{+4.2}_{-1.8} \times 10^{-13}$ erg cm−2 s−1 in the 0.3–10 keV range. TIC 378898110 is the shortest-period binary system discovered with TESS, and its large predicted gravitational-wave amplitude makes it a compelling verification binary for future space-based gravitational wave detectors.
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© The Author(s) 2023. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.