arXiv 1005.09662010-05-06astro-ph.SR

OGLE 2008-- BLG --290：通过微透镜空间分辨的银河系K巨星边缘变暗的精确测量

OGLE 2008--BLG--290: An accurate measurement of the limb darkening of a Galactic Bulge K Giant spatially resolved by microlensing

P. Fouque, D. Heyrovsky, S. Dong, A. Gould, A. Udalski, M. D. Albrow, V. Batista, J. -P. Beaulieu, D. P. Bennett, I. A. Bond, D. M. Bramich, S. Calchi Novati, A… 展开作者

P. Fouque, D. Heyrovsky, S. Dong, A. Gould, A. Udalski, M. D. Albrow, V. Batista, J. -P. Beaulieu, D. P. Bennett, I. A. Bond, D. M. Bramich, S. Calchi Novati, A. Cassan, C. Coutures, S. Dieters, M. Dominik, D. Dominis Prester, J. Greenhill, K. Horne, U. G. Jorgensen, S. Kozlowski, D. Kubas, C. -H. Lee, J. -B. Marquette, M. Mathiasen, J. Menzies, L. A. G. Monard, S. Nishiyama, I. Papadakis, R. Street, T. Sumi, A. Williams, J. C. Yee, S. Brillant, J. A. R. Caldwell, A. Cole, K. H. Cook, J. Donatowicz, N. Kains, S. R. Kane, R. Martin, K. R. Pollard, K. C. Sahu, Y. Tsapras, J. Wambsganss, M. Zub, D. L. DePoy, B. S. Gaudi, C. Han, C. -U. Lee, B. -G. Park, R. W. Pogge, M. Kubiak, M. K. Szymanski, G. Pietrzynski, I. Soszynski, O. Szewczyk, K. Ulaczyk, L. Wyrzykowski, F. Abe, A. Fukui, K. Furusawa, A. C. Gilmore, J. B. Hearnshaw, Y. Itow, K. ~Kamiya, P. M. Kilmartin, A. V. Korpela, W. Lin, C. H. Ling, K. Masuda, Y. Matsubara, N. Miyake, Y. Muraki, M. Nagaya, K. Ohnishi, T. Okumura, Y. Perrott, N. J. Rattenbury, To. Saito, T. Sako, S. Sato, L. Skuljan, D. Sullivan, W. Sweatman, P. J. Tristram, P. C. M. Yock, A. Allan, M. F. Bode, M. J. Burgdorf, N. Clay, S. N. Fraser, E. Hawkins, E. Kerins, T. A. Lister, C. J. Mottram, E. S. Saunders, C. Snodgrass, I. A. Steele, P. J. Wheatley, T. Anguita, V. Bozza, K. Harpsoe, T. C. Hinse, M. Hundertmark, P. Kjaergaard, C. Liebig, L. Mancini, G. Masi, S. Rahvar, D. Ricci, G. Scarpetta, J. Southworth, J. Surdej, C. C. Thone, A. Riffeser, S. ~Seitz, R. Bender

备注：: Astronomy & Astrophysics in press
DOI：: 10.1051/0004-6361/201014053

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摘要：

引力微透镜不仅是发现遥远系外行星的成功工具，而且还可以描述透镜事件中涉及的透镜和源星。在高放大倍率事件中，透镜焦散可能会穿过源盘，这允许确定源的角尺寸，并测量其临边变暗。当这种扩展光源效应出现在最大放大率附近时，所产生的光变曲线与典型的Paczynski点光源曲线不同。接近峰值的光变曲线的确切形状取决于光源的临边暗化。密集的光度覆盖允许测量各自的边缘变暗系数。在微透镜事件OGLE 2008-BLG-290中，K巨星源星达到了大约100倍的峰值放大率。十三台不同的望远镜在八个不同的光度波段覆盖了这一事件。随后的光变曲线分析产生的线性边缘变暗系数的来源在六个光度带的测量。最佳测量系数导致源有效温度的估计约为4700 + 100 - 200 K。然而，根据色星等图的光度估计，更倾向于4200 ± 100 K的较冷温度。由于边缘暗化测量，至少在CTIO/SMARTS 2 V和I波段，是最准确的获得，上述分歧需要理解。提出了一个解决办法，这可能适用于以前的事件，这种差异也出现了。

英文摘要：

Gravitational microlensing is not only a successful tool for discovering distant exoplanets, but it also enables characterization of the lens and source stars involved in the lensing event. In high magnification events, the lens caustic may cross over the source disk, which allows a determination of the angular size of the source and additionally a measurement of its limb darkening. When such extended-source effects appear close to maximum magnification, the resulting light curve differs from the characteristic Paczynski point-source curve. The exact shape of the light curve close to the peak depends on the limb darkening of the source. Dense photometric coverage permits measurement of the respective limb-darkening coefficients. In the case of microlensing event OGLE 2008-BLG-290, the K giant source star reached a peak magnification of about 100. Thirteen different telescopes have covered this event in eight different photometric bands. Subsequent light-curve analysis yielded measurements of linear limb-darkening coefficients of the source in six photometric bands. The best-measured coefficients lead to an estimate of the source effective temperature of about 4700 +100-200 K. However, the photometric estimate from colour-magnitude diagrams favours a cooler temperature of 4200 +-100 K. As the limb-darkening measurements, at least in the CTIO/SMARTS2 V and I bands, are among the most accurate obtained, the above disagreement needs to be understood. A solution is proposed, which may apply to previous events where such a discrepancy also appeared.

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