A survey for variable young stars with small telescopes - III. Warm spots on the active star V1598 Cyg
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Magnetic spots on low-mass stars can be traced and characterized using multiband photometric light curves. Here, we analyse an extensive dataset for one active star, V1598 Cyg, 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 4 yr, obtained with small telescopes as part of the HOYS project. We find that V1598 Cyg is a very fast rotator with a period of 0.8246 d and varying amplitudes in all filters, best explained as a signature of strong magnetic activity and spots. We fit the photometric amplitudes inV, 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 of100 K and 3-4 per cent, respectively. V1598 Cyg 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 0.5-1 yr, 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.
Froebrich , D , Scholz , A , Eislöffel , J & Stecklum , B 2020 , ' A survey for variable young stars with small telescopes - III. Warm spots on the active star V1598 Cyg ' , Monthly Notices of the Royal Astronomical Society , vol. 497 , no. 4 , pp. 4602-4613 . https://doi.org/10.1093/mnras/staa2275
Monthly Notices of the Royal Astronomical Society
Copyright © 2020 the Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at https://doi.org/10.1093/mnras/staa2275.
DescriptionFunding: AS acknowledges support through STFC grant ST/R000824/1.
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