MKT J170456.2-482100: the first transient discovered by MeerKAT

• Published in: arXiv.org
• Main Authors: Driessen, L N, McDonald, I, Buckley, D A H, Caleb, M, Kotze, E J, Potter, S B, Rajwade, K M, Rowlinson, A, Stappers, B W, Tremou, E, Woudt, P A, Fender, R P, Armstrong, R, Groot, P, Heywood, I, Horesh, A, A J van der Horst, Koerding, E, McBride, V A, Miller-Jones, J C A, Mooley, K P, R A M J Wijers
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 18.11.2019
• Subjects: Amplitudes; Binary stars; Flux density; Light curve; Line of sight; Photometry; Physics - High Energy Astrophysical Phenomena; Physics - Solar and Stellar Astrophysics; Radial velocity; X ray binaries; X ray stars
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1911.07713

We report the discovery of the first transient with MeerKAT, MKT J170456.2\(-\)482100, discovered in ThunderKAT images of the low mass X-ray binary GX339\(-\)4. MKT J170456.2\(-\)482100 is variable in the radio, reaching a maximum flux density of \(0.71\pm0.11\,\mathrm{mJy}\) on 2019 Oct 12, and is undetected in 15 out of 48 ThunderKAT epochs. MKT J170456.2\(-\)482100 is coincident with the chromospherically active K-type sub-giant TYC 8332-2529-1, and \(\sim18\,\mathrm{years}\) of archival optical photometry of the star shows that it varies with a period of \(21.25\pm0.04\,\mathrm{days}\). The shape and phase of the optical light curve changes over time, and we detect both X-ray and UV emission at the position of MKT J170456.2\(-\)482100, which may indicate that TYC 8332-2529-1 has large star spots. Spectroscopic analysis shows that TYC 8332-2529-1 is in a binary, and has a line-of-sight radial velocity amplitude of \(43\,\mathrm{km\,s^{-1}}\). We also observe a spectral feature in anti-phase with the K-type sub-giant, with a line-of-sight radial velocity amplitude of \(\sim12\pm10\,\mathrm{km\,s^{-1}}\), whose origins cannot currently be explained. Further observations and investigation are required to determine the nature of the MKT J170456.2\(-\)482100 system.