Introduction
Qatar-1 b is positioned approximately at (J2000) R.A. = 20h13m32s, De. = + 65°09'43", in Draco, the host of which has 12.84 Vmag. According to the Exoplanet Transit Database (ETD), the transit leads to a decrease in brightness of its star seen from the earth is 0.0204 mag, and the duration is about 96.7-min.
The equipment used for the monitor was 14" SCT f/6.9 + QHY9 CCD.
Overall 500 images with individual exposure 15-s were remotely taken by Xing Gao, from Urumqi, China at predawn on Sep 28 local time, which were later callibrated with bias, dark, and flat frames in MaxIm DL by me. Subsequently I sorted these individual images into quintuplets, which were stacked in Astrometrica by means of median. I employed both MPO Canopus and MaxIm DL to measure the lightcurve, and found that the latter prevailed the former a bit and therefore only the results measured by MaxIm DL were performed.
Here comes the data:
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J.D. Qatar-1 b Err
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2455832.17932291 13.213 0.001
2455832.18093171 13.214 0.001
2455832.18252893 13.213 0.001
2455832.18390625 13.221 0.001
2455832.18528356 13.214 0.001
2455832.18666087 13.217 0.001
2455832.18806134 13.213 0.001
2455832.18945023 13.204 0.001
2455832.19082754 13.211 0.001
2455832.19220486 13.216 0.001
2455832.19358217 13.214 0.001
2455832.19497106 13.211 0.001
2455832.19634837 13.223 0.001
2455832.19772569 13.215 0.001
2455832.19911458 13.231 0.001
2455832.20050347 13.220 0.001
2455832.20188078 13.221 0.001
2455832.20326967 13.227 0.001
2455832.20464699 13.227 0.001
2455832.20602430 13.225 0.001
2455832.20741319 13.233 0.001
2455832.20880208 13.233 0.001
2455832.21020254 13.242 0.001
2455832.21160300 13.250 0.001
2455832.21299189 13.243 0.001
2455832.21438078 13.252 0.001
2455832.21578125 13.250 0.001
2455832.21715856 13.257 0.001
2455832.21855902 13.262 0.001
2455832.21994791 13.254 0.001
2455832.22133680 13.256 0.001
2455832.22272569 13.252 0.001
2455832.22412615 13.260 0.001
2455832.22552662 13.258 0.001
2455832.22692708 13.263 0.001
2455832.22832754 13.263 0.001
2455832.22973958 13.260 0.001
2455832.23114004 13.255 0.001
2455832.23254050 13.254 0.001
2455832.23395254 13.264 0.001
2455832.23536458 13.259 0.001
2455832.23676504 13.270 0.001
2455832.23817708 13.270 0.001
2455832.23958912 13.267 0.001
2455832.24098958 13.254 0.001
2455832.24239004 13.277 0.001
2455832.24379050 13.267 0.001
2455832.24519097 13.260 0.001
2455832.24659143 13.272 0.001
2455832.24799189 13.269 0.001
2455832.24939236 13.263 0.001
2455832.25079282 13.272 0.001
2455832.25220486 13.262 0.001
2455832.25361689 13.259 0.001
2455832.25501736 13.270 0.001
2455832.25642939 13.267 0.001
2455832.25782986 13.263 0.001
2455832.25925347 13.261 0.001
2455832.26066550 13.261 0.001
2455832.26208912 13.249 0.001
2455832.26350115 13.255 0.001
2455832.26491319 13.245 0.001
2455832.26631365 13.258 0.001
2455832.26772569 13.249 0.001
2455832.26913773 13.247 0.001
2455832.27054976 13.258 0.001
2455832.27196180 13.249 0.001
2455832.27338541 13.249 0.001
2455832.27479745 13.246 0.001
2455832.27622106 13.254 0.001
2455832.27764467 13.247 0.001
2455832.27905671 13.253 0.001
2455832.28046875 13.248 0.001
2455832.28188078 13.252 0.001
2455832.28330439 13.249 0.001
2455832.28473958 13.247 0.001
2455832.28615162 13.253 0.001
2455832.28757523 13.239 0.001
2455832.28899884 13.252 0.001
2455832.29041088 13.258 0.001
2455832.29183449 13.242 0.001
2455832.29324652 13.253 0.001
2455832.29467013 13.255 0.001
2455832.29608217 13.254 0.001
2455832.29750578 13.250 0.001
2455832.29894097 13.249 0.001
2455832.30035300 13.250 0.001
2455832.30178819 13.265 0.001
2455832.30322337 13.256 0.001
2455832.30462384 13.240 0.001
2455832.30605902 13.255 0.001
2455832.30748263 13.266 0.001
2455832.30890625 13.248 0.001
2455832.31032986 13.265 0.001
2455832.31175347 13.246 0.001
2455832.31317708 13.244 0.001
2455832.31460069 13.254 0.001
2455832.31603587 13.261 0.001
2455832.31745949 13.261 0.001
2455832.31889467 13.251 0.001
The following plots were generated in the course of ETD. The upper one plots raw data, whereas the lower one plots data with correction to systematic errors by means of both linear power and parabolic fit.
The following figure plots the residuals after the fit correction.
The plots shows the airmass versus time. As seen from the graph, the altitude of the target was setting lower during the observation in that the airmass kept in a tendency of incline.
Overall 5 reference stars were taken adjacent to the target, as shown in the following image. Magnitude sources were taken from USNO-A 2.0 star catalog in V band, rendered in Canopus.
The following graph plots the lightcurves of all of the comparison stars, symbolized in squares, along with the two checked stars, shaped in triangles. The lightcurve atop the graph is the one of the transiting star. I suspect if some of the comparison stars actually are variable stars since their tendencies deviate from each other. It may well be imperfection due to poor quality of the flatfield images containing stars from different portions of the sky as well, which were taken at dawn when the sky was brightening rapidly.
ETD measures the mid-transit time, duration and depth for me, respectively JD 2455832.23528 ± 0.00085, 98.9 ± 3.6 min, 0.0271 ± 0.0021 mag. The radius of the exoplanet is also estimated: Rp = 1.261 -0.049+0.047 RJup, where RJup denotes the radius of Jupiter, whereas the currently acknowledged value is Rp = 1.164 ± 0.045 RJup. Besides, the inclination was measured to be i = 83.47 -0.49|1.11+0.55|1.30 deg, compared to the currently recognized value i = 83.47 ± 0.38 deg, relatively close.
More observations are needed to remove occasional errors before the calculation in good accuracy.
Copyright © Man-To Hui 2011/10/02
Feel free to e-mail me with any doubts or questions.