SETI bioastro: Giant Planets are Rare at Large Separations v3

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Constraints on Extrasolar Planet Populations from VLT NACO/SDI and MMT SDI
and Direct Adaptive Optics Imaging Surveys: Giant Planets are Rare at Large
Separations

Authors: Eric L. Nielsen (1), Laird M. Close (1), Beth A. Biller (1), Elena
Masciadri (2), Rainer Lenzen (3) ((1) Steward Observatory, University of
Arizona, (2) INAF-Osservatorio Astrofisico di Arcetri, Italy, (3)
Max-Planck-Institut fur Astronomie, Hiedelberg, Germany)

(Submitted on 28 Jun 2007 (v1), last revised 10 Oct 2007 (this version, v3))

Abstract: We examine the implications for the distribution of extrasolar
planets based on the null results from two of the largest direct imaging
surveys published to date. Combining the measured contrast curves from 22 of
the stars observed with the VLT NACO adaptive optics system by Masciadri et
al. (2005), and 48 of the stars observed with the VLT NACO SDI and MMT SDI
devices by Biller et al. (2007) (for a total of 60 unique stars; the median
star for our survey is a 30 Myr K2 star at 25 pc), we consider what
distributions of planet masses and semi-major axes can be ruled out by these
data, based on Monte Carlo simulations of planet populations. We can set
this upper limit with 95% confidence: the fraction of stars with planets
with semi-major axis from 20 to 100 AU, and mass greater than 4 M_Jup, is
20% or less. Also, with a distribution of planet mass of dN/dM ~ M^-1.16
between 0.5-13 M_Jup, we can rule out a power-law distribution for
semi-major axis (dN/da ~ a^alpha) with index 0 and upper cut-off of 18 AU,
and index -0.5 with an upper cut-off of 48 AU. For the distribution
suggested by Cumming et al. (2007), a power-law of index -0.61, we can place
an upper limit of 75 AU on the semi-major axis distribution. At the 68%
confidence level, these upper limits state that fewer than 8% of stars have
a planet of mass greater than 4 M_Jup between 20 and 100 AU, and a power-law
distribution for semi-major axis with index 0, -0.5, and -0.61 cannot have
giant planets beyond 12, 23, and 29 AU, respectively. In general, we find
that even null results from direct imaging surveys are very powerful in
constraining the distributions of giant planets (0.5-13 M_Jup) at large
separations, but more work needs to be done to close the gap between planets
that can be detected by direct imaging, and those to which the radial
velocity method is sensitive.

Comments: 46 pages, 17 figures, accepted to ApJ

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0706.4331v3 [astro-ph]

Submission history

From: Eric Nielsen [view email]

[v1] Thu, 28 Jun 2007 22:08:04 GMT (489kb)

[v2] Sun, 1 Jul 2007 11:23:24 GMT (480kb)

[v3] Wed, 10 Oct 2007 01:24:36 GMT (488kb)

http://arxiv.org/abs/0706.4331

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