Abstract
We report the detection of eclipses in LSPM J1112+7626, which we find to be a moderately bright (I_C = 12.14 +/- 0.05) very low-mass binary system with an orbital period of 41.03236 +/- 0.00002 days, and component masses M_1 = 0.395 +/- 0.002 Msol and M_2 = 0.275 +/- 0.001 Msol in an eccentric (e = 0.239 +/- 0.002) orbit. A 65 day out of eclipse modulation of approximately 2% peak-to-peak amplitude is seen in I-band, which is probably due to rotational modulation of photospheric spots on one of the binary components. This paper presents the discovery and characterization of the object, including radial velocities sufficient to determine both component masses to better than 1% precision, and a photometric solution. We find that the sum of the component radii, which is much better-determined than the individual radii, is inflated by 3.8 +0.9 -0.5 % compared to the theoretical model predictions, depending on the age and metallicity assumed. These results demonstrate that the difficulties in reproducing observed M-dwarf eclipsing binary radii with theoretical models are not confined to systems with very short orbital periods. This object promises to be a fruitful testing ground for the hypothesized link between inflated radii in M-dwarfs and activity.
Highlights
Detached, double-lined eclipsing binaries (EBs) provide a largely model-independent means to precisely and accurately measure fundamental stellar properties, masses and radii
The observation of inflated radii for M-dwarf binaries at the 5%–10% level, and effective temperatures 3%–5% lower than the models predict, is nearly ubiquitous among the best-characterized objects (e.g., Torres et al 2010, and references therein; Morales et al 2010; Kraus et al 2011), it is interesting to note that Carter et al (2011) find a smaller inflation for KOI-126B and C, members of a fascinating system containing a short-period M-dwarf binary orbiting a K star, where the system undergoes mutual eclipses allowing a precise determination of the radii of both M-dwarfs
We present the discovery of eclipses in LSPM J1112+7626, a nearby double-lined M-dwarf system with an extremely long orbital period of approximately 41 days
Summary
Double-lined eclipsing binaries (EBs) provide a largely model-independent means to precisely and accurately measure fundamental stellar properties, masses and radii. Despite the ubiquity of M-dwarfs in the solar neighborhood, their fundamental properties are poorly understood This is the case below 0.35 M , the boundary at which field stars are thought to become fully convective (e.g., Chabrier & Baraffe 1997). The observation of inflated radii for M-dwarf binaries at the 5%–10% level, and effective temperatures 3%–5% lower than the models predict, is nearly ubiquitous among the best-characterized objects (e.g., Torres et al 2010, and references therein; Morales et al 2010; Kraus et al 2011), it is interesting to note that Carter et al (2011) find a smaller inflation for KOI-126B and C, members of a fascinating system containing a short-period M-dwarf binary orbiting a K star, where the system undergoes mutual eclipses allowing a precise determination of the radii of both M-dwarfs
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