The secondary eclipses of WASP-19b as seen by the ASTEP 400 telescope from Antarctica-猫眼课题宝

DOI：

10.1051/0004-6361/201220351

发表时间：

2013-03

期刊：

Astronomy and Astrophysics

影响因子：

6.5

通讯作者：

中科院分区：

物理与天体物理2区

文献类型：

作者：

L. Abe;I. Gonccalves;A. Agabi;A. Alapini;T. Guillot;D. M'ekarnia;J. Rivet;F. Schmider;N. Crouzet;J. Fortney;F. Pont;M. Barbieri;J. Daban;Y. Fantei-caujolle;C. Gouvret;Y. Bresson;A. Roussel;S. Bonhomme;A. Robini;M. Dugu'e;E. Bondoux;S. P'eron;P.-Y. Petit;J. Szul'agyi;T. Fruth;A. Erikson;H. Rauer;F. Fressin;F. Valbousquet;P. Blanc;A. L. V. Suu;S. Aigrain

ASTEP(南极洲搜索凌日系外行星)计划最初的目的是探测南极洲圆顶C的质量，以用光度法发现和表征系外行星。在40厘米ASTEP 400望远镜运行的第一年(2010年南半球冬季)，我们瞄准了已知的凌日行星WASP-19b，试图在可见光中探测到它的第二次凌日。这是由于入库数据具有极高的亚毫米级成像精度。在2010年5月的24个晚上观察到了WASP-19系统。由恒星黑子引起的光度学变化水平约为1.8%(峰间)，与SuperWASP 2007年的数据(1.4%)一致，但高于2008年的数据(0.07%)。我们发现WASP-19的自转周期为10.7+/-0.5天，与SuperWASP测定的10.5+/-0.2天一致。理论模型表明，这只能在恒星内的潮汐耗散很弱时才能解释，即潮汐耗散因子Q‘star&gt；3.10^7。另外，我们还发现了深度为390+/-190ppm的二次日食的证据，具有2.0西格玛意义，相位与圆形轨道一致，假阳性概率为3%。在给定观测波长范围(420至950 nm)的情况下，二次过境深度转换为日侧亮度温度2690(-220/+150)K，与z‘和K波段的测量结果一致。可见光中观察到的白天辐射可能是由于极热的白天辐射，将热量重新分配到夜间，或者是由于最大几何反照率为Ag=0.27+/-0.13的恒星光的直接反射。我们还报告了在行星轨道周期有一个很好的同相低频振荡，但其下限幅度不能单独归因于行星的相位，并且可能被残留的光曲线趋势所污染。

The ASTEP (Antarctica Search for Transiting ExoPlanets) program was originally aimed at probing the quality of the Dome C, Antarctica for the discovery and characterization of exoplanets by photometry. In the first year of operation of the 40 cm ASTEP 400 telescope (austral winter 2010), we targeted the known transiting planet WASP-19b in order to try to detect its secondary transits in the visible. This is made possible by the excellent sub-millimagnitude precision of the binned data. The WASP-19 system was observed during 24 nights in May 2010. The photometric variability level due to starspots is about 1.8% (peak-to-peak), in line with the SuperWASP data from 2007 (1.4%) and larger than in 2008 (0.07%). We find a rotation period of WASP-19 of 10.7 +/- 0.5 days, in agreement with the SuperWASP determination of 10.5 +/- 0.2 days. Theoretical models show that this can only be explained if tidal dissipation in the star is weak, i.e. the tidal dissipation factor Q'star > 3.10^7. Separately, we find evidence for a secondary eclipse of depth 390 +/- 190 ppm with a 2.0 sigma significance, a phase consistent with a circular orbit and a 3% false positive probability. Given the wavelength range of the observations (420 to 950 nm), the secondary transit depth translates into a day side brightness temperature of 2690(-220/+150) K, in line with measurements in the z' and K bands. The day side emission observed in the visible could be due either to thermal emission of an extremely hot day side with very little redistribution of heat to the night side, or to direct reflection of stellar light with a maximum geometrical albedo Ag=0.27 +/- 0.13. We also report a low-frequency oscillation well in phase at the planet orbital period, but with a lower-limit amplitude that could not be attributed to the planet phase alone, and possibly contaminated with residual lightcurve trends.

The secondary eclipses of WASP-19b as seen by the ASTEP 400 telescope from Antarctica

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