Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2010-08-13
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
To appear in ApJ. 11 pages, 5 figures
Scientific paper
We present high-resolution Keck optical spectra of the very young substellar eclipsing binary 2MASS J05352184-0546085, obtained during eclipse of the lower-mass (secondary) brown dwarf. The observations yield the spectrum of the higher-mass (primary) brown dwarf alone, with negligible (~1.6%) contamination by the secondary. We perform a simultaneous fine-analysis of the TiO-epsilon band and the red lobe of the KI doublet, using state-of-the-art PHOENIX Dusty and Cond synthetic spectra. Comparing the effective temperature and surface gravity derived from these fits to the {\it empirically} determined surface gravity of the primary (logg=3.5) then allows us to test the model spectra as well as probe the prevailing photospheric conditions. We find that: (1) fits to TiO-epsilon alone imply Teff=2500 \pm 50K; (2) at this Teff, fits to KI imply logg=3.0, 0.5 dex lower than the true value; and (3) at the true logg, KI fits yield Teff=2650 \pm 50K, ~150K higher than from TiO-epsilon alone. On the one hand, these are the trends expected in the presence of cool spots covering a large fraction of the primary's surface (as theorized previously to explain the observed Teff reversal between the primary and secondary). Specifically, our results can be reproduced by an unspotted stellar photosphere with Teff=2700K and (empirical) logg=3.5, coupled with axisymmetric cool spots that are 15% cooler (2300K), have an effective logg=3.0 (0.5 dex lower than photospheric), and cover 70% of the surface. On the other hand, the trends in our analysis can also be reproduced by model opacity errors: there are lacks in the synthetic TiO-epsilon opacities, at least for higher-gravity field dwarfs. Stringently discriminating between the two possibilities requires combining the present results with an equivalent analysis of the secondary (predicted to be relatively unspotted compared to the primary).
Doppmann Greg W.
Mohanty Subhanjoy
Stassun Keivan G.
No associations
LandOfFree
High Resolution Spectroscopy during Eclipse of the Young Substellar Eclipsing Binary 2MASS 0535-0546. I. Primary Spectrum: Cool Spots versus Opacity Uncertainties does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with High Resolution Spectroscopy during Eclipse of the Young Substellar Eclipsing Binary 2MASS 0535-0546. I. Primary Spectrum: Cool Spots versus Opacity Uncertainties, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High Resolution Spectroscopy during Eclipse of the Young Substellar Eclipsing Binary 2MASS 0535-0546. I. Primary Spectrum: Cool Spots versus Opacity Uncertainties will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-503176