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A search for variability in exoplanet analogues and low-gravity brown dwarfs
Stockholm University, Faculty of Science, Department of Astronomy.
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Number of Authors: 212019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 483, no 1, p. 480-502Article in journal (Refereed) Published
Abstract [en]

We report the results of a J-band survey for photometric variability in a sample of young, low-gravity objects using the New Technology Telescope (NTT) and the United Kingdom Infrared Telescope (UKIRT). Surface gravity is a key parameter in the atmospheric properties of brown dwarfs and this is the first large survey that aims to test the gravity dependence of variability properties. We do a full analysis of the spectral signatures of youth and assess the group membership probability of each target using membership tools from the literature. This results in a 30 object sample of young low-gravity brown dwarfs. Since we are lacking in objects with spectral types later than L9, we focus our statistical analysis on the L0-L8.5 objects. We find that the variability occurrence rate of L0-L8.5 low-gravity brown dwarfs in this survey is 30(-8)(+16) per cent. We reanalyse the results of Radigan (2014) and find that the field dwarfs with spectral types L0-L8.5 have a variability occurrence rate of 11(-4)(+13) per cent. We determine a probability of 98 per cent that the samples are drawn from different distributions. This is the first quantitative indication that the low-gravity objects are more likely to be variable than the field dwarf population. Furthermore, we present follow-up J(S) and K-S observations of the young, planetary-mass variable object PSO 318.5-22 over three consecutive nights. We find no evidence of phase shifts between the J(S) and K-S bands and find higher J(S) amplitudes. We use the J(S) light curves to measure a rotational period of 8.45 +/- 0.05 h for PSO 318.5-22.

Place, publisher, year, edition, pages
2019. Vol. 483, no 1, p. 480-502
Keywords [en]
brown dwarfs, stars: variables: general
National Category
Physical Sciences Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-168452DOI: 10.1093/mnras/sty3123ISI: 000462251000032OAI: oai:DiVA.org:su-168452DiVA, id: diva2:1313259
Available from: 2019-05-02 Created: 2019-05-02 Last updated: 2019-05-02Bibliographically approved

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