Astronomy and Astrophysics – Astronomy
Scientific paper
May 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...210.7804r&link_type=abstract
American Astronomical Society Meeting 210, #78.04; Bulletin of the American Astronomical Society, Vol. 39, p.185
Astronomy and Astrophysics
Astronomy
Scientific paper
In general, low-mass Main Sequence and Brown Dwarf (BD) objects are rapid rotators, with rotational periods averaging approximately 4 hours. If there are any longitudinal spatial variations in the flux emitted from their atmospheres, either due to star spot-like patches or cloud features, the total flux should show some periodic variability on these time scales, assuming that the view angle is not pole-on. There may also be longer time-scale non-periodic variability if the star-spots or clouds change in size over time. We have a program to use the IRS instrument on Spitzer to further investigate the question of temporal variability in the mid-infrared flux from Brown Dwarfs. Although there have been earlier attempts with mixed success to see temporal variations in BD photometric fluxes, there are certain advantages to looking for temporal variations in the spectrum of an object rather than photometrically. Our program consists of time series observations of four L or T-type Brown Dwarfs that have been previously observed with the IRS instrument and whose mid-infrared spectra are well-characterized. Each target is observed for almost 4 hours at a time over three different epochs spaced a few days apart within one IRS campaign. Observations over these time bases allows studies both at typical BD rotation periods of hours, as well as checking for longer-period changes over periods of days. Two of our targets have now been observed, and the results are presented here.
This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407.
Cushing Michael
Houck James R.
Kirkpatrick David
Leggett Sandy K.
Mainzer Amanda K.
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