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A survey for variable young stars with small telescopes: III. Warm spots on the active star V1598Cyg

Froebrich, Dirk, Scholz, Aleks, Eisloffel, Jochen, Stecklum, Bringfried (2020) A survey for variable young stars with small telescopes: III. Warm spots on the active star V1598Cyg. Monthly Notices of the Royal Astronomical Society, 497 (4). pp. 4602-4613. ISSN 0035-8711. E-ISSN 1365-2966. (doi:10.1093/mnras/staa2275) (KAR id:82343)

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Magnetic spots on low-mass stars can be traced and characterised using multi-band photometric light curves. Here we analyse an extensive data set for one active star, V1598Cyg, a known variable K dwarf which is either pre-main sequence and/or in a close binary system. Our light curve contains 2854 photometric data points, mostly in V, Rc, Ic, but also in U, B and Hα, with a total baseline of about 4yr, obtained with small telescopes as part of the HOYS project. We find that V1598Cyg is a very fast rotator with a period of 0.8246 days and varying amplitudes in all filters, best explained as a signature of strong magnetic activity and spots. We fit the photometric amplitudes in V, Rc, Ic and use them to estimate spot properties, using a grid-based method that is also propagating uncertainties. We verify the method on a partial data set with high cadence and all five broad-band filters. The method yields spot temperatures and fractional spot coverage with typical uncertainties of 100K and 3-4%, respectively. V1598Cyg consistently exhibits spots that are a few hundred degrees warmer than the photosphere, most likely indicating that the light curve is dominated by chromospheric plage. The spot activity varies over our observing baseline, with a typical time scale of 0.5-1yr, which we interpret as the typical spot lifetime. Combining our light curve with archival data, we find a six year cycle in the average brightness, that is probably a sign of a magnetic activity cycle.

Item Type: Article
DOI/Identification number: 10.1093/mnras/staa2275
Uncontrolled keywords: Solar and Stellar Astrophysics
Subjects: Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Divisions > Division of Natural Sciences > Physics and Astronomy
Depositing User: Dirk Froebrich
Date Deposited: 03 Aug 2020 10:09 UTC
Last Modified: 03 Sep 2021 14:00 UTC
Resource URI: (The current URI for this page, for reference purposes)
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