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

Creators: 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, Evangelia; Woudt, P. A.; Fender, R. P.; Armstrong, R.; Groot, P.; Heywood, I.; Horesh, A.; van der Horst, A. J.; Koerding, E.; McBride, V. A.; Miller-Jones, J. C. A.; Mooley, K. P.; Wijers, R. A. M. J.

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±0.11mJy on 2019 October 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 ∼18yr of archival optical photometry of the star shows that it varies with a period of 21.25±0.04d⁠. 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 43kms⁻¹⁠. We also observe a spectral feature in antiphase with the K-type sub-giant, with a line-of-sight radial velocity amplitude of ∼12±10kms⁻¹⁠, whose origins cannot currently be explained. Further observations and investigation are required to determine the nature of the MKT J170456.2–482100 system.

Additional Information

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2019 October 18. Received 2019 October 18; in original form 2019 August 14. Published: 30 October 2019. LND, MC, KMR, and BWS acknowledge support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 694745). This work was partly funded by the United Kingdom's Science and Technologies Facilities Council (STFC) grant ST/P000649/1. DAHB acknowledges research support from the South African National Research Foundation. ET acknowledges financial support from the UnivEarthS Labex program of Sorbonne Paris Cité (ANR-10-LABX-0023 and ANR-11-IDEX-0005-02). PAW acknowledges support from the National Research Foundation (NRF) and the University of Cape Town (UCT). This research was supported by a Grant from the GIF, the German-Israeli Foundation for Scientific Research and Development. AH acknowledges support from GIF. JCAM-J is the recipient of an Australian Research Council Future Fellowship (FT140404082), funded by the Australian Government. We acknowledge use of the Inter-University Institute for Data Intensive Astronomy (IDIA) data intensive research cloud for data processing. IDIA is a South African university partnership involving the University of Cape Town, the University of Pretoria and the University of the Western Cape. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory (SARAO), which is a facility of the National Research Foundation, an agency of the Department of Science and Technology. We would like to thank the operators, SARAO staff and ThunderKAT Large Survey Project team. The Parkes radio telescope is part of the Australia Telescope National Facility, which is funded by the Commonwealth of Australia for operation as a National Facility managed by the Commonwealth Scientific and Industrial Research Organisation (CSIRO). Some of these observations were obtained with the Southern African Large Telescope under the Large Science Programme on transients, 2018-2-LSP-001 (PI: DAHB). This work makes use of observations from the Las Cumbrés Observatory (LCO) network. Kilodegree Extremely Little Telescope (KELT) data are made available to the community through the Exoplanet Archive on behalf of the KELT project team, kindly provided by Rudi Kuhn. This work has made use of data from the European Space Agency (ESA) mission Gaia.11 Funding for the Data Processing and Analysis Consortium (DPAC) has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research made use of ASTROPY,12 a community-developed core PYTHON package for Astronomy (Astropy Collaboration et al. 2013; Price-Whelan et al. 2018). This research made use of APLPY, an open-source plotting package for PYTHON (Robitaille & Bressert 2012). LND would like to thank Colin Clark, Mark Kennedy, and Daniel Mata for useful and interesting discussions. We would like to thank the referee for their constructive comments on the manuscript.

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