Recurring sets of recurring starspots on exoplanet-host Qatar-2

Močnik, T. ; Southworth, J.; Hellier, C.

Abstract

We announce the detection of recurring sets of recurring starspot occultation events in the short-cadence K2 light curve of Qatar-2, a K dwarf star transited every 1.34 d by a hot Jupiter. In total, we detect 34 individual starspot occultation events, caused by five different starspots, occulted in up to five consecutive transits or after a full stellar rotation. The longest recurring set of recurring starspot occultations spans over three stellar rotations, setting a lower limit for the longest starspot lifetime of 58 d. Starspot analysis provided a robust stellar rotational period measurement of 18.0 ± 0.2 d and indicates that the system is aligned, having a skyprojected obliquity of 0? ± 8?. A pronounced rotational modulation in the light curve has a period of 18.2 ± 1.6 d, in agreement with the rotational period derived from the starspot occultations. We tentatively detect an ellipsoidal modulation in the phase curve, with a semiamplitude of 18 ppm, but cannot exclude the possibility that this is the result of red noise or imperfect removal of the rotational modulation. We detect no transit-timing and transitduration variations with upper limits of 15 s and 1 min, respectively. We also reject any additional transiting planets with transit depths above 280 ppm in the orbital period region 0.5–30 d.

Citation

Močnik, T., Southworth, J., & Hellier, C. (2017). Recurring sets of recurring starspots on exoplanet-host Qatar-2. Monthly Notices of the Royal Astronomical Society, 471(1), 394-403. https://doi.org/10.1093/mnras/stx1557

• Journal Article Type: Article
• Acceptance Date: Jun 20, 2017
• Online Publication Date: Jun 22, 2017
• Publication Date: 2017-10
• Publicly Available Date: May 26, 2023
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 471
• Issue: 1
• Pages: 394-403
• DOI: https://doi.org/10.1093/mnras/stx1557
• Keywords: stars, fundamental parameters, individual, Qatar-2, planetary systems, starspots
• Publisher URL: http://dx.doi.org/10.1093/mnras/stx1557