J/A+A/683/A239 Spot modeling of V1298 Tau using SpotCCF tool (Di Maio+, 2024) ================================================================================ The GAPS programme at TNG. LII. Spot modeling of V1298 Tau using SpotCCF tool. Di Maio C., Petralia A., Micela G., Lanza A.F., Rainer M., Malavolta L., Benatti S., Affer L., Maldonado J., Colombo S., Damasso M., Maggio A., Biazzo K., Bignamini A., Borsa F., Boschin W., Cabona L., Cecconi M., Claudi R., Covino E., Di Fabrizio L., Gratton R., Lorenzi V., Mancini L., Messina S., Molinari E., Molinaro M., Nardiello D., Poretti E., Sozzetti A. =2024A&A...683A.239D (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Stars, variable ; Stars, activity ; Spectroscopy Keywords: techniques: radial velocities - techniques: spectroscopic - stars: activity - starspots Abstract: The intrinsic variability due to the magnetic activity of young active stars is one of the main challenges in detecting and characterising exoplanets. The stellar activity is responsible for jitter effects observed both in photometric and spectroscopic observations that could impact our planetary detection sensitivity. We present a method able to model the stellar photosphere and its surface inhomogeneities (starspots) in young/active and fast-rotating stars, based on the cross-correlation function (CCF) technique, to extract information about the spot configuration of the star. We developed SpotCCF, a tool able to model the deformation of the CCF profile due to the presence of multiple spots on the stellar surface. Within the Global Architecture of Planetary Systems (GAPS) Project at the Telescopio Nazionale Galileo, we analysed more than 300 spectra of the young planet-hosting star V1298 Tau provided by HARPS-N high-resolution spectrograph. By applying the SpotCCF model to the CCFs we extracted the spot configuration (latitude, longitude and projected filling factor) of this star, and also provided the new RVs time series of this target. We find that the features identified in the CCF profiles of V1298 Tau are modulated by the stellar rotation, supporting our assumption that they are caused by starspots. The analysis suggests a differential rotation velocity of the star with lower rotation at higher latitudes. Also, we find that SpotCCF provides an improvement in RVs extraction with a significantly lower dispersion with respect to the commonly used pipelines, with consequent mitigation of the stellar activity contribution modulated with stellar rotation. A detection sensitivity test, by the direct injection of a planetary signal into the data, confirmed that the SpotCCF model improves the sensitivity and ability to recover planetary signals. Our method enables the modelling of the stellar photosphere, extracting the spot configuration of young/active and rapidly rotating stars. It also allows for the extraction of optimised RV time series, thereby enhancing our detection capabilities for new exoplanets and advancing our understanding of stellar activity. Description: Table B1 provides the derived properties of the spots by using SpotCCF. Objects: ------------------------------------------------------- RA (2000) DE Designation(s) ------------------------------------------------------- 04 05 19.59 +20 09 25.6 V1298 Tau = V* V1298 Tau ------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file tableb1.dat 140 308 Spot parameters derived by the two-spots model -------------------------------------------------------------------------------- See also: J/AJ/163/247 : V1298 Tau HIRES, PEPSI + TRES radial velocities (Johnson+, 2022) Byte-by-byte Description of file: tableb1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 12 F12.4 d Time Time of the observation (BJD) 14- 18 F5.2 deg lat1 Latitude of the spot 1 20- 24 F5.2 deg E_lat1 Upper uncertainty of lat1 26- 29 F4.2 deg e_lat1 Lower uncertainty of lat1 31- 36 F6.2 deg lon1 Longitude of the spot 1 38- 41 F4.2 deg E_lon1 Upper uncertainty of lon1 43- 46 F4.2 deg e_lon1 Lower uncertainty of low1 48- 53 F6.4 --- rr1 Radius of spot 1, in stellar radius 55- 60 F6.4 --- E_rr1 Upper uncertainty of rr1, in stellar radius 62- 67 F6.4 --- e_rr1 Lower uncertainty of rr1, in stellar radius 69- 73 F5.3 --- ffp1 Projected filling factor of spot 1 75- 79 F5.2 --- lat2 Latitude of spot 2 81- 85 F5.2 deg E_lat2 Upper uncertainty of lat2 87- 90 F4.2 deg e_lat2 Lower uncertainty of lat2 92- 97 F6.2 deg lon2 Longitude of spot 2 99-102 F4.2 deg E_lon2 Upper uncertainty of lon2 104-107 F4.2 deg e_lon2 Lower uncertainty of lon2 109-114 F6.4 --- rr2 Radius of spot 2, in stellar radius 116-121 F6.4 --- E_rr2 Upper uncertainty of rr2, in stellar radius 123-128 F6.4 --- e_rr2 Lower uncertainty of rr2, in stellar radius 130-134 F5.3 --- ffp2 Projected filling factor of spot 2 136-140 F5.3 --- ffptot Total projected filling factor -------------------------------------------------------------------------------- Acknowledgements: Claudia Di Maio, claudia.dimaio(at)inaf.it References: Covino et al., Paper I 2013A&A...554A..28C, Cat. 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