TY - JOUR
T1 - Can microlensing fold caustics reveal a second stellar limb-darkening coefficient?
AU - Dominik, M
PY - 2004/8/21
Y1 - 2004/8/21
N2 - Dense high-precision photometry of microlensed stars during a fold-caustic passage can be used to reveal their brightness profiles, from which the temperature of the stellar atmosphere as a function of fractional radius can be derived. While the capabilities of current microlensing follow-up campaigns such as PLANET allowed for several precise measurements of linear limb-darkening coefficients, all attempts to reveal a second limb-darkening coefficient from such events have failed. It is shown that the residual signal of a second coefficient characterizing square-root limb darkening is similar to25 times smaller, which prevents a proper determination except for unlikely cases of very high caustic-peak-to-outside magnification ratios with no adequate event being observed so far or for source stars passing over a cusp singularity. Although the presence of limb darkening can be well established from the data, a reliable measurement of the index of an underlying power law cannot be obtained.
AB - Dense high-precision photometry of microlensed stars during a fold-caustic passage can be used to reveal their brightness profiles, from which the temperature of the stellar atmosphere as a function of fractional radius can be derived. While the capabilities of current microlensing follow-up campaigns such as PLANET allowed for several precise measurements of linear limb-darkening coefficients, all attempts to reveal a second limb-darkening coefficient from such events have failed. It is shown that the residual signal of a second coefficient characterizing square-root limb darkening is similar to25 times smaller, which prevents a proper determination except for unlikely cases of very high caustic-peak-to-outside magnification ratios with no adequate event being observed so far or for source stars passing over a cusp singularity. Although the presence of limb darkening can be well established from the data, a reliable measurement of the index of an underlying power law cannot be obtained.
KW - gravitational lensing
KW - stars : atmospheres
KW - PLANET PHOTOMETRY
KW - STAR
UR - http://www.scopus.com/inward/record.url?scp=4344669463&partnerID=8YFLogxK
U2 - 10.1111/j.1365-2966.2004.08019.x
DO - 10.1111/j.1365-2966.2004.08019.x
M3 - Article
SN - 0035-8711
VL - 352
SP - 1315
EP - 1318
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
ER -