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arXiv · 1911.07713

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

L. N. Driessen·I. McDonald·D. A. H. Buckley·M. Caleb·E. J. Kotze·S. B. Potter·K . M. Rajwade·A. Rowlinson·B. W. Stappers·E. Tremou·P. A. Woudt·R. P. Fender·R. Armstrong·P. Groot·I. Heywood·A. Horesh·A. J. van der Horst·E. Koerding·V. A. McBride·J. C. A. Miller-Jones·K. P. Mooley·R. A. M. J. Wijers
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Abstract

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.

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L. N. Driessen, I. McDonald, D. A. H. Buckley, M. Caleb, E. J. Kotze, S. B. Potter, K . M. Rajwade, A. Rowlinson, B. W. Stappers, E. Tremou, P. A. Woudt, R. P. Fender, R. Armstrong, P. Groot, I. Heywood, A. Horesh, A. J. van der Horst, E. Koerding, V. A. McBride, J. C. A. Miller-Jones, K. P. Mooley, R. A. M. J. Wijers. 2019-11-18. MKT J170456.2-482100: the first transient discovered by MeerKAT. https://doi.org/10.1093/mnras%2Fstz3027

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