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

Journal article

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.

Authors: Driessen, LN; McDonald, I; Buckley, DAH; Caleb, M; Kotze, EJ

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 491
• Issue: 1
• Pages: 560-575
• Publication date: 2019-10-30
• Acceptance date: 2019-10-18
• DOI: 10.1093/mnras/stz3027
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: FFR; binaries: spectroscopic; stars: peculiar; stars: flare; stars: activity