Open AccessThe abundance of Galactic planets from OGLE‐III 2002 microlensing data
Author(s) -
Snodgrass Colin,
Horne Keith,
Tsapras Yiannis
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07839.x
Subject(s) - physics , gravitational microlensing , planet , astrophysics , exoplanet , einstein radius , planetary system , astronomy , hot jupiter , gravitational lens , light curve , radius , bulge , stars , galaxy , redshift , computer security , computer science
From the 389 OGLE‐III 2002 observations of Galactic bulge microlensing events, we select 321 that are well described by a point‐source point‐lens light‐curve model. From this sample we identify one event, 2002‐BLG‐055, that we regard as a strong planetary lensing candidate, and another, 2002‐BLG‐140, that is a possible candidate. If each of the 321 lens stars has one planet with a mass ratio q = m / M = 10 −3 and orbit radius a = R E , the Einstein ring radius, analysis of detection efficiencies indicates that 14 planets should have been detectable with Δχ 2 > 25 . Assuming our candidate is due to planetary lensing, then the abundance of planets with q = 10 −3 and a = R E is n p ≈ n /14 = 7 per cent. Conversion to physical units (Jupiter masses, M Jup , and astronomical units, au) gives the abundance of ‘cool Jupiters’ ( m ≈ M Jup , a ≈ 4 au) per lens star as n p ≈ n /5.5 = 18 per cent. The detection probability scales roughly with q and (Δχ 2 ) −1/2 , and drops off from a peak at a ≈ 4 au like a Gaussian with a dispersion of 0.4 dex.