Monday, June 3, 2013

1305.7260 (Diana Dragomir et al.)

A warm, likely volatile-rich super-Earth: HD 97658b transits, but not quite when expected    [PDF]

Diana Dragomir, Jaymie M. Matthews, Jason D. Eastman, Chris Cameron, Andrew W. Howard, David B. Guenther, Rainer Kuschnig, Anthony F. J. Moffat, Jason F. Rowe, Slavek M. Rucinski, Dimitar Sasselov, Werner W. Weiss
Through photometric monitoring of the extended transit window of HD 97658b with the MOST space telescope, we have found that this exoplanet transits with an ephemeris consistent with that predicted from radial velocity measurements. The mid-transit times are 6$\sigma$ earlier than those of the unverified transit-like signals reported in 2011, and we find no connection between the two sets of events. The transit depth indicates a 2.34$^{+0.18}_{-0.15}$ $R_\earth$ super-Earth. When combined with the radial velocity determined mass of 7.86 $\pm 0.73$ $M_\earth$, our radius measure allows us to derive a planet density of 3.44$^{+0.91}_{-0.82}$ g cm$^{-3}$. Models suggest that a planet with our measured density has a rocky core that is enveloped in an atmosphere composed of lighter elements. The star of the HD 97658 system is the second brightest known to host a transiting super-Earth, facilitating folllow-up studies of this not easily daunted, warm and likely volatile-rich exoplanet.
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