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Published April 20, 2013 | Published
Journal Article Open

Weather on Other Worlds. I. Detection of Periodic Variability in the L3 Dwarf DENIS-P J1058.7-1548 with Precise Multi-wavelength Photometry

Abstract

Photometric monitoring from warm Spitzer reveals that the L3 dwarf DENIS-P J1058.7-1548 varies sinusoidally in brightness with a period of 4.25^(+0.26)_(-0.16) hr and an amplitude of 0.388% ± 0.043% (peak-to-valley) in the 3.6 μm band, confirming the reality of a 4.31 ± 0.31 hr periodicity detected in J-band photometry from the SOAR telescope. The J-band variations are a factor of 2.17 ± 0.35 larger in amplitude than those at 3.6 μm, while 4.5 μm Spitzer observations yield a 4.5 μm/3.6 μm amplitude ratio of only 0.23 ± 0.15, consistent with zero 4.5 μm variability. This wide range in amplitudes indicates rotationally modulated variability due to magnetic phenomena and/or inhomogeneous cloud cover. Weak Hα emission indicates some magnetic activity, but it is difficult to explain the observed amplitudes by magnetic phenomena unless they are combined with cloud inhomogeneities (which might have a magnetic cause). However, inhomogeneous cloud cover alone can explain all our observations, and our data align with theory in requiring that the regions with the thickest clouds also have the lowest effective temperature. Combined with published vsin (i) results, our rotation period yields a 95% confidence lower limit of R_* ≥ 0.111 R_☉, suggesting upper limits of 320 Myr and 0.055 M_☉ on the age and mass. These limits should be regarded cautiously because of ~3σ inconsistencies with other data; however, a lower limit of 45° on the inclination is more secure. DENIS-P J1058.7-1548 is only the first of nearly two dozen low-amplitude variables discovered and analyzed by the Weather on Other Worlds project.

Additional Information

© 2013 American Astronomical Society. Received 2012 December 19; accepted 2013 March 11; published 2013 April 8. We thank Didier Saumon for supplying us with files containing the model spectra of Saumon & Marley (2008), which we have used to construct our two-phase models of DENIS 1058. This research was supported by NASA through the Spitzer Exploration Science Program Weather on Other Worlds (program GO 80179) and ADAP award NNX11AB18G. This research is also based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU). The SOAR observations reported herein were made under Chilean program CN2012A-055. Radostin Kurtev acknowledges support from Proyecto DIUV23/2009, Centro de Astrofísica de Valparaíso, and FONDECYT through grant 1130140. We thank Nikole Lewis for supplying us with IDL code to measure the noise pixel parameter of our data, for allowing us to read the draft version of her paper describing uses of this parameter in IRAC photometry, and for additional helpful advice. This publication makes use of the SIMBAD online database, operated at CDS, Strasbourg, France, and the VizieR online database (see Ochsenbein et al. 2000). This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. We have also made extensive use of information and code from Press et al. (1992). We have used digitized images from the Palomar Sky Survey (available from http://stdatu.stsci.edu/cgi-bin/dss_form), which were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. Facilities: SOAR, Spitzer

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Created:
August 19, 2023
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October 23, 2023