Contribution by Dr. Gerold Holtkamp, June 2025
The measurements were taken from 9:27 PM UTC on March 6, 2025, to 2:20 AM UTC on March 7, 2025, in Osnabrück, Sonnenhügel. The moon was 54% illuminated and 46° distant. It set around 2:15 AM UTC.
The measurement technique used:
Telescope: Skywatcher Newton 250/1200 mm
Mount: Skywatcher AZ-EQ6
Filter: Luminanz (Antlia)
Camera: QHY268M with gain 60, offset 20, chip temperature -10° C
Guiding: Skywatcher Guidescope Evoguide 50 ED with camera ZWO ASI120mm
NINA was used for camera and mount control.
The present measurement and the subsequent evaluation with the hops software of the Exoclock-Project resulted in:
Rp/Rs = 0.1148 +/- 0.0033 (expected 0.11 +/- 0.006) *
–> Rp = 0,1148 x 1.004.819 = 115.353 +/- 3.316 km. [1]
The exoplanet XO-6b is considerably larger than Jupiter (radius = 69,911 km). The system is 766 light-years from Earth.
The value of the transit's midpoint, which is important for the Exoclock project and is expressed as the difference between the observed and expected values, agrees well with the expected value at O-C = -0.35 +/- 2.59 minutes**, albeit with a rather large error. Therefore, our own measurement lies almost at the zero line in the diagram above.
The measurement of the transit light curve of the exoplanet XO-6b was published on the Exoclock project website. [2]
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* [Rp = Rplanet, Rs = Rstar]
If the star's radius is known, the planet's radius is determined directly from the dip in the light curve. (see also https://kosmos-os.de/messung-der-transitlichtkurven-der-exoplaneten-wasp-84b-und-kps-1b-am-7-und-8-maerz-2024)
** [O = Observed, C = Calculated]
[1]
Data on the star system and the exoplanet at
https://exoplanetarchive.ipac.caltech.edu/overview/XO-6b
The radius value used was 1.443 +0.044/-0.167 (Gaia DR2) x the radius of the Sun. The radius of the Sun was assumed to be 696,340 km.
[2]
https://www.exoclock.space/database/observations/XO-6b_2442_2025-03-06_Gerold_1561_Lum
