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Title: FLIP-FLOP ACTIVITY ON THE W UMa-TYPE BINARY SYSTEM HH UMa

Abstract

We report the discovery of flip-flop activity in a W UMa-type binary. A long-term multi-color photometric surveillance of HH UMa was carried out with three sets of light curves obtained over six weeks. The light curves of the eclipsing binary presented marked asymmetry and rapid interchange between the two light maxima. During the observations from 2014 February to 2014 April, the spot distortion phase jumped between phases 0.25 and 0.75 twice, a typical indication of flip-flop activity. We applied the Wilson–Devinney method to analyze the three light curves. The results indicate that HH UMa is a partially eclipsing contact system of A subtype with an obviously asymmetric light curve. The observed light curves can be modeled by assuming that there are two dark spots on the massive primary component that are almost persistently located around phases 0.25 and 0.75, but can interchange their intensities. We further suggest that a plausible scenario for explaining the properties of those dark spots is strong surface magnetic activity with a sudden reversal of the more active longitude. We therefore conclude that HH UMa is very likely a W UMa-type system displaying flip-flop activity.

Authors:
; ; ; ;  [1];  [2]
  1. Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)
  2. Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)
Publication Date:
OSTI Identifier:
22522410
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 805; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMMETRY; BINARY STARS; COLOR; DIAGRAMS; ECLIPSE; MONITORING; PHOTOMETRY; STARSPOTS; SURFACES; VISIBLE RADIATION

Citation Formats

Wang, Kun, Zhang, Xiaobin, Deng, Licai, Luo, Changqing, Luo, Yangping, and Zhang, Jun, E-mail: kwang@bao.ac.cn. FLIP-FLOP ACTIVITY ON THE W UMa-TYPE BINARY SYSTEM HH UMa. United States: N. p., 2015. Web. doi:10.1088/0004-637X/805/1/22.
Wang, Kun, Zhang, Xiaobin, Deng, Licai, Luo, Changqing, Luo, Yangping, & Zhang, Jun, E-mail: kwang@bao.ac.cn. FLIP-FLOP ACTIVITY ON THE W UMa-TYPE BINARY SYSTEM HH UMa. United States. doi:10.1088/0004-637X/805/1/22.
Wang, Kun, Zhang, Xiaobin, Deng, Licai, Luo, Changqing, Luo, Yangping, and Zhang, Jun, E-mail: kwang@bao.ac.cn. Wed . "FLIP-FLOP ACTIVITY ON THE W UMa-TYPE BINARY SYSTEM HH UMa". United States. doi:10.1088/0004-637X/805/1/22.
@article{osti_22522410,
title = {FLIP-FLOP ACTIVITY ON THE W UMa-TYPE BINARY SYSTEM HH UMa},
author = {Wang, Kun and Zhang, Xiaobin and Deng, Licai and Luo, Changqing and Luo, Yangping and Zhang, Jun, E-mail: kwang@bao.ac.cn},
abstractNote = {We report the discovery of flip-flop activity in a W UMa-type binary. A long-term multi-color photometric surveillance of HH UMa was carried out with three sets of light curves obtained over six weeks. The light curves of the eclipsing binary presented marked asymmetry and rapid interchange between the two light maxima. During the observations from 2014 February to 2014 April, the spot distortion phase jumped between phases 0.25 and 0.75 twice, a typical indication of flip-flop activity. We applied the Wilson–Devinney method to analyze the three light curves. The results indicate that HH UMa is a partially eclipsing contact system of A subtype with an obviously asymmetric light curve. The observed light curves can be modeled by assuming that there are two dark spots on the massive primary component that are almost persistently located around phases 0.25 and 0.75, but can interchange their intensities. We further suggest that a plausible scenario for explaining the properties of those dark spots is strong surface magnetic activity with a sudden reversal of the more active longitude. We therefore conclude that HH UMa is very likely a W UMa-type system displaying flip-flop activity.},
doi = {10.1088/0004-637X/805/1/22},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 805,
place = {United States},
year = {2015},
month = {5}
}