Activity cycles of M dwarfs

Саванов, И. С.

doi:10.1134/s1063772912090077

Cited by 42 publications

(53 citation statements)

References 10 publications

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“…As noted in Section 1, Kiraga & Stepień (2007), Savanov (2012), andSuárez Mascareño et al (2016) measured rotation periods of around 83 d using ASAS-3 data, in good agreement with the 83.5 d period measured by Benedict et al (1998) using Hubble data. Guinan (2010) cites a period of 83.7 d and an activity cycle of ∼7.6 yr derived from an unpublished analysis of ASAS data, and also says that ROSAT , XMM-Newton, and Chandra data show a 'corresponding coronal Xray cycle with an expected minimum during 2010/11.'…”

Section: Optical Datasupporting

confidence: 77%

“…Using five years of Vband data from ASAS-3 supplemented with UV data from the IUE and FUSE missions, Jason et al (2007) saw indications of a 'probable' cycle of 6.9±0.5 years in Prox Cen, later revised to 7.6 years in a Chandra observing proposal by Guinan (2010). Savanov (2012) later calculated amplitude power spectra using nine years of ASAS data and also saw a broad peak around 8 yr, along with several other peaks at shorter periods. (We learned shortly before acceptance of this paper that Suárez Mascareño et al 2016 (in press) also analyzed ASAS-3 data and found cycles in seven and perhaps as many as nine stars of type M4 or later, including Prox Cen with P rot = 6.8 ± 0.3 yr.)…”

Section: Introductionmentioning

confidence: 97%

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Optical, UV, and X-ray evidence for a 7-yr stellar cycle in Proxima Centauri

Wargelin¹,

Saar²,

Pojmański³

et al. 2016

Mon. Not. R. Astron. Soc.

103

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Stars of stellar type later than about M3.5 are believed to be fully convective and therefore unable to support magnetic dynamos like the one that produces the 11-year solar cycle. Because of their intrinsic faintness, very few late M stars have undergone long-term monitoring to test this prediction, which is critical to our understanding of magnetic field generation in such stars. Magnetic activity is also of interest as the driver of UV and X ray radiation, as well as energetic particles and stellar winds, that affect the atmospheres of close-in planets that lie within habitable zones, such as the recently discovered Proxima b. We report here on several years of optical, UV, and X-ray observations of Proxima Centauri (GJ 551; dM5.5e): 15 years of ASAS photometry in the V band (1085 nights) and 3 years in the I band (196 nights), 4 years of Swift XRT and UVOT observations (more than 120 exposures), and 9 sets of X-ray observations from other X-ray missions (ASCA, XMM-Newton, and three Chandra instruments) spanning 22 years. We confirm previous reports of an 83-day rotational period and find strong evidence for a 7-year stellar cycle, along with indications of differential rotation at about the solar level. X-ray/UV intensity is anti-correlated with optical V -band brightness for both rotational and cyclical variations. From comparison with other stars observed to have X-ray cycles we deduce a simple empirical relationship between X-ray cyclic modulation and Rossby number, and we also present Swift UV grism spectra covering 2300-6000Å.

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Section: Optical Datasupporting

confidence: 77%

Section: Introductionmentioning

confidence: 97%

Optical, UV, and X-ray evidence for a 7-yr stellar cycle in Proxima Centauri

Wargelin¹,

Saar²,

Pojmański³

et al. 2016

Mon. Not. R. Astron. Soc.

103

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“…The periodicity of these quantities are well known to be in good agreement with the MAC derived via photometric modulations generated by stellar spots for the Sun, solar-type, and low-mass stars (e.g. Basri et al 2010;Savanov 2012;Mathur et al 2014;Montet et al 2017;He et al 2018).…”

Section: Flare Analysissupporting

confidence: 71%

Orbital Period Variation of KIC 10544976: Applegate Mechanism versus Light Travel Time Effect

Almeida

Almeida²,

Damineli

et al. 2019

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In recent years, several close post-common-envelope eclipsing binaries have been found to show cyclic eclipse timing variations (ETVs). This effect is usually interpreted either as the gravitational interaction among circumbinary bodies and the host binary -known as the light travel time (LTT) effect -or as the quadrupole moment variations in one magnetic active component -known as Applegate mechanism. In this study, we present an analysis of the ETV and the magnetic cycle of the close binary KIC 10544976. This system is composed of a white dwarf and a red dwarf in a short orbital period (0.35 days) and was monitored by ground-based telescopes between 2005 and 2017 and by the Kepler satellite between 2009 and 2013. Using the Kepler data, we derived the magnetic cycle of the red dwarf by two ways: the rate and energy of flares and the variability due to spots. Both methods resulted in a cycle of ∼600 days, which is in agreement with magnetic cycles measured for single low-mass stars. The orbital period of KIC 10544976 shows only one long-term variation which can be fitted by an LTT effect with period of ∼16.8 yr. Hence, one possible explanation for the ETVs is the presence of a circumbinary body with minimal mass of ∼13.4 M Jup . In the particular scenario of coplanarity between the external body and the inner binary, the third body mass is also ∼13.4 M Jup . In this case, the circumbinary planet must either have survived the evolution of the host binary or have been formed as a consequence of its evolution.

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“…First we discuss the possible physical causes giving rise to the periodic component of the O-C variation. There could be three possible causes of this type of variation: (i) change in the stellar structure due to stellar magnetic cycles (the so-called Applegateeffect -see Applegate 1992); (ii) apsidal motion mainly due to the finite size and non-spherical shape of the components (e.g., Savanov (2012) and Vida et al (2013Vida et al ( , 2014 to see if our target follows the relation between the rotation frequency and the magnetic cycle length. We make the obviously non-stringent assumption that the orbital period is a good proxy of the rotation period.…”

Section: Physical Interpretationmentioning

confidence: 99%

The hierarchical triple nature of the former red nova precursor candidate KIC 9832227

Kovács

Hartman

Bakos

2019

A&A

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We revisit the issue of period variation of the recently claimed red nova precursor candidate KIC 9832227. By using the data gathered during the main mission of the Kepler satellite, those collected by ground-based wide-field surveys and other monitoring programs (such as ASAS-SN), we find that the currently available timing data strongly support a model consisting of the known W UMa binary and a distant low-mass companion with an orbital period of ∼ 13.5 years. The period of the W UMa component exhibits a linear period decrease with a pace of (1.10 ± 0.05) × 10 −6 days per year, within the range of many other similar systems. This rate of decrease is several orders of magnitude lower than that of V1309 Sco, the first (and so far the only) well-established binary precursor of a nova observed a few years before the outburst. The high-fidelity fit of the timing data and the conformity of the derived minimum mass of (0.38 ± 0.02) M ⊙ of the outer companion from these data with the limit posed by the spectroscopic non-detection of this component, are in agreement with the suggested hierarchical nature of this system.

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Activity cycles of M dwarfs

Cited by 42 publications

References 10 publications

Optical, UV, and X-ray evidence for a 7-yr stellar cycle in Proxima Centauri

Optical, UV, and X-ray evidence for a 7-yr stellar cycle in Proxima Centauri

Orbital Period Variation of KIC 10544976: Applegate Mechanism versus Light Travel Time Effect

The hierarchical triple nature of the former red nova precursor candidate KIC 9832227

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