Survey for Transiting Extrasolar Planets in Stellar Systems. III. A Limit on the Fraction of Stars with Planets in the Open Cluster NGC 1245

Abstract

We analyze a 19 night photometric search for transiting extrasolar planets in the open cluster NGC 1245. An automated transit search algorithm with quantitative selection criteria finds six transit candidates; none are bona fide planetary transits. We characterize the survey detection probability via Monte Carlo injection and recovery of realistic limb-darkened transits. We use this to derive upper limits on the fraction of cluster members with close-in Jupiter radii, R J , companions. The survey sample contains $870 cluster members, and we calculate 95% confidence upper limits on the fraction of these stars with planets by assuming that the planets have an even logarithmic distribution in semimajor axis over the Hot Jupiter (HJ; 3:0 < P day À1 < 9:0) and Very Hot Jupiter ( VHJ; 1:0 < P day À1 < 3:0) period ranges. For 1.5R J companions we limit the fraction of cluster members with companions to <6.4% and <52% for VHJ and HJ companions, respectively. For 1.0R J companions we find that <24% have VHJ companions. We do not reach the sensitivity to place any meaningful constraints on 1.0R J HJ companions. From a careful analysis of the random and systematic errors of the calculation, we show that the derived upper limits contain a þ13% /À7% relative error. For photometric noise and weather properties similar to those of this survey, observing NGC 1245 twice as long results in a tighter constraint on HJ companions than observing an additional cluster of richness similar to that of NGC 1245 for the same length of time as this survey. If 1% of stars have 1.5R J HJ companions (as measured in radial velocity surveys), we expect to detect one planet for every 5000 dwarf stars observed for a month. To reach an $2% upper limit on the fraction of stars with 1.5R J companions in the 3:0 < P day À1 < 9:0 range, we conclude that a total sample size of $7400 dwarf stars observed for at least a month will be needed. Results for 1.0R J companions, without substantial improvement in the photometric precision, will require a small factor larger sample size.

Very Low Mass Stellar and Substellar Companions to Solar-Like Stars From Marvels. Ii. A Short-Period Companion Orbiting an F Star With Evidence of a Stellar Tertiary and Significant Mutual Inclination

“…We find similar or larger improvements in χ 2 when we consider arbitrary phases for the transit and when we consider "anti-transits" (signals with the same shape as transits but corresponding to positive deviations; see Burke et al 2006). As before, these formally significant signals likely arise from systematics in the photometric data.…”

KELT-11b: A Highly Inflated Sub-Saturn Exoplanet Transiting the V = 8 Subgiant HD 93396

“…The host star properties can be seen in Table 1. We use the Box-fitting Least-squares algorithm (BLS; Kovács et al 2002) as implemented in the VAR-TOOLS software package (Hartman & Bakos 2016) to identify transit candidates, making use of statistics that come from the VARTOOLS package, as well as from Pont et al (2006) and Burke et al (2006). The associated selection criteria and the corresponding values for KELT-11b are shown in Table 2.…”

Kelt-17b: A Hot-Jupiter Transiting an a-Star in a Misaligned Orbit Detected With Doppler Tomography

“…The box-fitting least squares (BLS) (Kovács et al 2002) periodicity algorithm was used to search for candidates in KJ06. Candidates are selected according to statistics produced with the VARTOOLS (Hartman & Bakos 2016) implementation of BLS, and from statistics calculated as per Pont et al (2006) and Burke et al (2006). Table 2 shows the criteria and results for the KELT-17b candidate selection.…”