Messung der Transitlichtkurve des Exoplaneten TOI-1516b am 20./21. März 2025

Measurement of the transit light curve of the exoplanet TOI-1516b on March 20/21, 2025

Contribution by Dr. Gerold Holtkamp, June 2025

The measurements were taken from 10:39 PM UTC on March 20, 2025, to 3:34 AM UTC on March 21, 2025, in Osnabrück, Sonnenhügel. The moon was 64% illuminated and 115° distant. It rose at approximately 1:15 AM UTC on March 21, 2025, but only reached a maximum altitude of 9° above the horizon. It was therefore of little relevance for the measurement.

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 measured transit light curve in the exoclock representation*

The present measurement and the subsequent evaluation with the hops software of the Exoclock-Project resulted in:

Rp/Rs = 0.1243 +/- 0.0045 (expected 0.1224 +/- 0.0005) *
–> Rp = 0,1243 x 793.828 = 98.673 +/- 3.572 km. [1]

The exoplanet TOI-1516b is more than a third larger than Jupiter (radius = 69,911 km). The system is 805 light-years from Earth.

*The own measurement of the transit center together with the other values available at Exoclock*

The value of the temporal center of the transit, which is important for the Exoclock project and is expressed as the difference between the observed and the expected value, is O-C = 1.94 +/- 2.45 minutes**, which is above the expected value but still within the error limits.

The measurement of the transit light curve of the exoplanet TOI-1516b 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/toi-1516
The radius of the parent star was taken as 1.14 +0.02/-0.02 (Kabáth et al. 2022) x the radius of the Sun. The radius of the Sun was assumed to be 696,340 km. The parent star therefore has a radius of 793,828 km.

[2]
https://www.exoclock.space/database/observations/TOI-1516b_4479_2025-03-21_Gerold_1561_Lum/