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Paper: Planets in the Galactic Bulge: Results from the SWEEPS Project
Volume: 398, Extreme Solar Systems
Page: 93
Authors: Sahu, K.C.; Casertano, S.; Valenti, J.; Bond, H.E.; Brown, T.M.; Smith, T.E.; Clarkson, W.; Minniti, D.; Zoccali, M.; Livio, M.; Renzini, A.; Rich, R.M.; Panagia, N.; Lubow, S.; Brown, T.; Piskunov, N.
Abstract: The exoplanets discovered so far have been mostly around relatively nearby and bright stars. As a result, the host stars are mostly (i) in the Galactic disk, (ii) relatively massive, and (iii) relatively metal rich. The aim of the SWEEPS project is to extend our knowledge to stars which (i) are in a different part of the Galaxy, (ii) have low masses, and (iii) have a large range of metallicities. To achieve this goal, we used the Hubble Space Telescope and its Advanced Camera for Surveys to look for transiting planets around F, G, K, and and M dwarfs in the Galactic bulge. We photometrically monitored ∼180,000 stars in a dense stellar field in the Galactic bulge continuously for 7 days. We discovered 16 candidate transiting extrasolar planets with periods of 0.6 to 4.2 days, including a new class of ultra-short period planets (USPPs) with P < 1.2 days. Radial velocity observations of two brightest candidates support the planetary nature. These results suggest that planets are equally abundant in the Galactic bulge and around low-mass stars (within a factor ∼2), and the metallicity distribution holds even for the stars in the Galactic bulge. The USPPs occur only around low-mass stars which suggest that close-in planets around higher-mass stars are either irradiately evaporated, or that the size of the inner disk hole decreases with decreasing mass of the host stars.
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