Microlensing of Elliptical Sources by Fold Caustics
| dc.creator | Gaudi, B. Scott | |
| dc.creator | Haiman, Zoltan | |
| dc.date | 2004-01-05 | |
| dc.date.accessioned | 2026-07-07T02:11:47Z | |
| dc.date.available | 2026-07-07T02:11:47Z | |
| dc.description | We consider microlensing of an elliptical source crossing a fold caustic. We derive a simple expression for the light curve of a source with uniform surface brightness that is accurate to third order in the ellipticity e (yielding errors of <1% for e<0.3). We consider caustic crossings of a rotating star, an oblate giant extrasolar planet, and an inclined standard thin accretion disk, and find the following results. (1) If most stars have rotation periods similar to chromospherically-active (i.e. spotted) giant stars in the bulge, than ~15% should be sufficiently oblate (e>0.25) to produce detectable (>1%) deviations with current observations. The form of the deviation due to ellipticity is qualitatively similar to that due to limb-darkening. Thus stellar oblateness may have to be taken into account in interpretations of precise limb-darkening measurements with microlensing. (2) Giant planets will generally not produce a detectable oblateness signal, either because they rotate too slowly (if they are close-in and tidally locked), or because they are too faint (if they are farther away from the parent star). (3) There is a near-degeneracy between ellipticity and position angle for equal-area sources with scale-free intensity profiles and elliptical isophotes. This degeneracy results in a factor of ~2 uncertainty in the measurement of the scale-length of a standard thin accretion disk using observations of a single, linear fold crossing quasar microlensing event in passbands probing the outer parts of the disk. Higher-frequency observations can reduce this uncertainty. | |
| dc.description | 9 pages, 8 figures, submitted to ApJ | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0401035 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0401035 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/7221 | |
| dc.subject | Astrophysics | |
| dc.title | Microlensing of Elliptical Sources by Fold Caustics | |
| dc.type | text |