The variability of Sun-like stars : reproducing observed photometric trends

Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.; Schmutz, W. K.; Ball, W. T.; Knaack, Reto; Rozanov, E. V.; Unruh, Y. C.

doi:10.1051/0004-6361/201323086

Publication type:	Article in scientific journal
Type of review:	Peer review (publication)
Title:	The variability of Sun-like stars : reproducing observed photometric trends
Authors:	Shapiro, A. I. Solanki, S. K. Krivova, N. A. Schmutz, W. K. Ball, W. T. Knaack, Reto Rozanov, E. V. Unruh, Y. C.
DOI:	10.1051/0004-6361/201323086
Published in:	Astronomy & Astrophysics
Volume(Issue):	569
Issue:	A38
Issue Date:	10-Jun-2014
Publisher / Ed. Institution:	EDP Sciences
ISSN:	0004-6361 1432-0746
Language:	English
Subjects:	Astro-ph.SR; Sun: activity; Stars: activity; Stars: solar-type; Stars: variables: general; Solar-terrestrial relations; Sun: atmosphere
Subject (DDC):	500: Natural sciences
Abstract:	Context: The Sun and stars with low magnetic activity levels become photometrically brighter when their activity increases. Magnetically more active stars display the opposite behavior and become fainter when their activity increases. Aims: We reproduce the observed photometric trends in stellar variations with a model thattreats stars as hypothetical suns with coverage by magnetic features different from that of the Sun. Methods: The model attributes the variability of stellar spectra to the imbalance between the contributions from different components of the solar atmosphere, such as dark starspots and bright faculae. A stellar spectrum is calculated from spectra of the individual components by weighting them with corresponding disk-area coverages. The latter are obtained by extrapolating the solar dependences of spot and facular disk-area coverages on chromospheric activity to stars with different levels of mean chromospheric activity. Results: We find that the contribution by starspots to the variability increases faster with chromospheric activity than the facular contribution. This causes the transition from faculae-dominated variability and direct activity-brightness correlation to spot-dominated variability and inverse activity-brightness correlation with increasing chromospheric activity level. We show that the regime of the variability also depends on the angle between the stellar rotation axis and the line-of-sight and on the latitudinal distribution of active regions on the stellar surface. Our model can be used as a tool for extrapolating the observed photometric variability of the Sun to Sun-like stars at different activity levels, which makes a direct comparison between solar and stellar irradiance data possible.
URI:	https://digitalcollection.zhaw.ch/handle/11475/13289
Fulltext version:	Published version
License (according to publishing contract):	Licence according to publishing contract
Departement:	School of Engineering
Organisational Unit:	Institute of Computational Physics (ICP)
Appears in collections:	Publikationen School of Engineering

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Shapiro, A. I., Solanki, S. K., Krivova, N. A., Schmutz, W. K., Ball, W. T., Knaack, R., Rozanov, E. V., & Unruh, Y. C. (2014). The variability of Sun-like stars : reproducing observed photometric trends. Astronomy & Astrophysics, 569(A38). https://doi.org/10.1051/0004-6361/201323086

Shapiro, A.I. et al. (2014) ‘The variability of Sun-like stars : reproducing observed photometric trends’, Astronomy & Astrophysics, 569(A38). Available at: https://doi.org/10.1051/0004-6361/201323086.

A. I. Shapiro et al., “The variability of Sun-like stars : reproducing observed photometric trends,” Astronomy & Astrophysics, vol. 569, no. A38, Jun. 2014, doi: 10.1051/0004-6361/201323086.

SHAPIRO, A. I., S. K. SOLANKI, N. A. KRIVOVA, W. K. SCHMUTZ, W. T. BALL, Reto KNAACK, E. V. ROZANOV und Y. C. UNRUH, 2014. The variability of Sun-like stars : reproducing observed photometric trends. Astronomy & Astrophysics. 10 Juni 2014. Bd. 569, Nr. A38. DOI 10.1051/0004-6361/201323086

Shapiro, A. I., S. K. Solanki, N. A. Krivova, W. K. Schmutz, W. T. Ball, Reto Knaack, E. V. Rozanov, and Y. C. Unruh. 2014. “The Variability of Sun-like Stars : Reproducing Observed Photometric Trends.” Astronomy & Astrophysics 569 (A38). https://doi.org/10.1051/0004-6361/201323086.

Shapiro, A. I., et al. “The Variability of Sun-like Stars : Reproducing Observed Photometric Trends.” Astronomy & Astrophysics, vol. 569, no. A38, June 2014, https://doi.org/10.1051/0004-6361/201323086.