A Portrait of the Rotation of Ultra-cool Dwarfs Revealed by TESS

• Published in: The Astrophysical journal Vol. 973; no. 2; pp. 106 - 118
• Main Authors: Fontinele, D. O., de Lima, P. D. S., Messias, Y. S., Gomes, R. L., Ferreira Lopes, C. E., Canto Martins, B. L., Leão, I. C., De Araújo, J. M., Janot Pacheco, E., De Medeiros, J. R.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-10-2024; IOP Publishing
• Subjects: Brown dwarfs; Light curve; Low mass stars; M stars; Periodic variations; Periodicities; Rotation; Signatures; Space observatories; Stars; Stellar age; Stellar astronomy; Stellar photometry; Stellar rotation
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ad64d6

Abstract This study presents the results of a search for rotation signatures in 250 Gaia Data Release 3 ultra-cool dwarfs (UCDs) with TESS light curves (LCs). We identified 71 targets with unambiguous periodicities, of which 61 present rotation signatures and a single-source behavior, with periods between 0.133 and 5.81 days. Five UCDs show double-dip features, namely variations with two periods, one approximately double or half the other. The remaining 10 UCDs with unambiguous variability present a likely nonsingle behavior. We also found 20 UCDs showing complex behavior in their LCs, with noticeable fluctuations and irregular structure, with a few exhibiting apparent changes in their temporal structure. The remaining 159 targets show noisy LCs corresponding to low-amplitude signals, whose temporal variation cannot be easily identified. The distribution of the UCDs with rotation signature in a color–magnitude diagram points to a lack of rotating objects within about 11.5 < M G < 12.5 and G – G RP < 1.5, separating them into two regimes, one mainly composed of less massive late-M stars with P rot ≥ 1.0 day, and another mainly composed of more massive early-M stars with P rot < 1.0 day. It is important to emphasize that by separating stars into age intervals, one observes that UCDs with P rot ≥ 1.0 day tend to be located in regions of younger objects, and, in contrast, those with P rot < 1.0 day are mainly concentrated in regions of older objects. Whether this trend of stars contrasting the sample separation is physical or produced by observational biases is a question to be verified in future studies.