Frequency of Hot Jupiters and Very Hot Jupiters from the OGLE-III Transit Surveys Toward the Galactic Bulge and Carina

TL;DR

This study estimates the frequency of hot and very hot Jupiters in the OGLE-III survey, finding rates comparable to radial velocity studies and highlighting biases in different detection methods.

Contribution

It provides the first frequency estimates of hot Jupiters and very hot Jupiters from OGLE-III data, accounting for detection sensitivities and biases.

Findings

Hot Jupiter frequency is about 1 in 310 stars.

Very hot Jupiter frequency is about 1 in 690 stars.

Detection rates are consistent with radial velocity surveys.

Abstract

We derive the frequencies of hot Jupiters (HJs) with 3--5 day periods and very hot Jupiters (VHJs) with 1-3 day periods by comparing the planets actually detected in the OGLE-III survey with those predicted by our models. The models are constructed following Gould & Morgan (2003) by populating the line of sight with stars drawn from the Hipparcos catalog. Using these, we demonstrate that the number of stars with sensitivity to HJs and VHJs is only 4--16% of those in the OGLE-III fields satisfying the spectroscopic-followup limit of V_max<17.5. Hence, the frequencies we derive are much higher than a naive estimate would indicate. We find that at 90% confidence the fraction of stars with planets in the two period ranges is (1/310)(1^{+1.39}_{-0.59}) for HJs and (1/690)(1^{+1.10}_{-0.54}) for VHJs. The HJ rate is statistically indistinguishable from that found in radial velocity (RV) studies. However, we note that magnitude-limited RV samples are heavily biased toward metal-rich (hence, planet-bearing) stars, while transit surveys are not, and therefore we expect that more sensitive transit surveys should find a deficit of HJs as compared to RV surveys. The detection of 3 transiting VHJs, all with periods less than 2 days, is marginally consistent with the complete absence of such detections in RV surveys. The planets detected are consistent with being uniformly distributed between 1.00 and 1.25 Jovian radii, but there are too few in the sample to map this distribution in detail.