Bridging the Gap—The Disappearance of the Intermediate Period Gap for Fully Convective Stars, Uncovered by New ZTF Rotation Periods

Lu, Yuxi; Curtis, Jason L.; Angus, Ruth; Hattori, Soichiro

doi:10.3847/1538-3881/ac9bee

Cited by 25 publications

(34 citation statements)

References 71 publications

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“…Having completed the coupling (reaching the slow-rotating population), the stellar surface would start to spin down again following the Skumanich law. Recently, evidence supporting this interpretation of the intermediate-P rot gap was found in ground-based photometric data by Lu et al (2022). The authors find that the gap is absent in the regime of fully convective stars, while it is still found for the partially convective stars.…”

Section: Introductionmentioning

confidence: 63%

“…In this context, stars would transition from spot-to faculae-dominated and the "gap" in the rotation distribution would be an artifact resulting from a lack of rotation detections due to the cancelation between the dark spots and the bright faculae (Reinhold et al 2019). Another interpretation of the bimodal rotation distribution has also been proposed: a broken spin-down law (McQuillan et al 2014;Angus et al 2020;Spada & Lanzafame 2020;Gordon et al 2021;Lu et al 2022). While decoupled from the core, the surface of stars on the fast-rotating population spins down due to magnetic braking, following the Skumanich law.…”

Section: Introductionmentioning

confidence: 99%

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Temporal variation of the photometric magnetic activity for the Sun andKeplersolar-like stars

Santos

Mathur

García

et al. 2023

A&A

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Context. The photometric time series of solar-like stars can exhibit rotational modulation, that is, brightness variations due to active regions co-rotating with the stellar surface. These signatures allow us to constrain properties of stellar rotation and magnetic activity. Aims. In this work we investigate the behavior, particularly the variability in terms of strength, of the photometric magnetic activity of Kepler solar-like stars and compare it with that of the Sun. Methods. We adopted the photometric magnetic activity proxy, Sph, which was computed with a cadence of five times the rotation period (Prot). The average Sph was taken as the mean activity level, and the standard deviation was taken as a measure of the temporal variation of the magnetic activity over the Kepler observations. We also analyzed Sun-as-a-star photometric data from VIRGO (Variability of Solar Irradiance and Gravity Oscillations). Sun-like stars were selected from a very narrow parameter space around the solar properties, according to the recent Gaia-Kepler stellar properties catalog and the latest Kepler rotation catalog. We also looked into KIC 8006161 (HD 173701), a very active metal-rich G dwarf, and we compared its magnetic activity to that of stars with similar stellar fundamental parameters. Results. We find that the amplitude of Sph variability is strongly correlated with its mean value, independent of spectral type. An equivalent relationship has previously been found for ground-based observations of chromospheric activity emission and magnetic field strength, but in this work we show that photometric Kepler data also present the same behavior. While, depending on the phase of the cycle, the Sun is among the less active stars, we find that the Sph⊙ properties are consistent with those observed in Kepler Sun-like stars. KIC 8006161 is, however, among the most active of its peers, which tend to be metal-rich. This results from an underlying relationship between Prot and metallicity and supports the following interpretation of the magnetic activity of KIC 8006161: its strong activity is a consequence of its high metallicity, which affects the depth of the convection zone and, consequently, the efficiency of the dynamo.

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Section: Introductionmentioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Temporal variation of the photometric magnetic activity for the Sun andKeplersolar-like stars

Santos

Mathur

García

et al. 2023

A&A

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“…Stellar activity and rotation or flares are known to have a broken power-law relation (Reiners et al 2014;Newton et al 2017;Wright et al 2018;Reinhold & Hekker 2020;Namekata et al 2021). To further understand their relations, we select two recent works 7 from Lu et al (2022), and Reinhold & Hekker (2020) that contain a large number of rotation periods from two different projects.…”

Section: Rotation and Hα Emission Relative To The Activity Dipmentioning

confidence: 99%

Mind the Gap. I. Hα Activity of M Dwarfs Near the Partially/Fully Convective Boundary and a New Hα Emission Deficiency Zone on the Main Sequence

Jao 饒,

Henry,

White

et al. 2023

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Since identifying the gap in the H-R Diagram (HRD) marking the transition between partially and fully-convective interiors, a unique type of slowly pulsating M dwarf has been proposed. These unstable M dwarfs provide new laboratories in which to understand how changing interior structures can produce potentially observable activity at the surface. In this work, we report the results of the largest high-resolution spectroscopic Hα emission survey to date spanning this transition region, including 480 M dwarfs observed using the CHIRON spectrograph at CTIO/SMARTS 1.5 m. We find that M dwarfs with Hα in emission are almost entirely found 0–0.5 mag above the top edge of the gap in the HRD, whereas effectively no stars in and below the gap show emission. Thus, the top edge of the gap marks a relatively sharp activity transition, and there is no anomalous Hα activity for stars in the gap. We also identify a new region at 10.3 < M G < 10.8 on the main sequence where fewer M dwarfs exhibit Hα emission compared to M dwarfs above and below this magnitude range. Careful evaluation of the results in the literature indicates that (1) rotation and Hα activity distributions on the main-sequence are closely related, and (2) fewer stars in this absolute magnitude range rotate in less than ∼13 days than populations surrounding this region. This result suggests that the most massive fully-convective stars lose their angular momentum faster than both partially convective stars and less massive fully-convective stars.

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“…For some analysis steps, the irregular cadence is converted to a regular cadence with 1.0 day bin width. Note that we did not attempt to use the more sophisticated custom ZTF data reduction method by Lu et al (2022), which involves considering archival ZTF light curves for multiple stars located near the target star to remove the systematics that are common to all of these stars.…”

Section: Photometric Rotational Periods From Ztf Light Curvesmentioning

confidence: 99%

Magnetic Activity–Rotation–Age–Mass Relations in Late-pre-main-sequence Stars

Getman

Feigelson

Garmire

2023

ApJ

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We study the four-dimensional relationships between magnetic activity, rotation, mass, and age for solar-type stars in the age range 5–25 Myr. This is the late-pre-main-sequence (l-PMS) evolutionary phase when rapid changes in a star's interior may lead to changes in the magnetic dynamo mechanisms. We carefully derive rotational periods and spot sizes for 471 members of several l-PMS open clusters using photometric light curves from the Zwicky Transient Facility. Magnetic activity was measured in our previous Chandra-based study, and additional rotational data were obtained from other work. Several results emerge. Mass-dependent evolution of rotation through the l-PMS phase agrees with astrophysical models of stellar angular momentum changes, although the data suggest a subpopulation of stars with slower initial rotations than commonly assumed. There is a hint of the onset of unsaturated tachoclinal dependency of X-ray activity on rotation, as reported by Argiroffi et al., but this result is not confidently confirmed. Both X-ray luminosity and starspot area decrease approximately as t −1 for solar-mass stars, suggesting that spot magnetic fields are roughly constant and l-PMS stars follow the universal solar-scaling law between the X-ray luminosity and surface magnetic flux. Assuming convective dynamos are dominant, theoretical magnetic fluxes fail to reveal the universal law for l-PMS stars that enter late Henyey tracks. Altogether we emerge with a few lines of evidence suggesting that the transition from the turbulent to solar-type dynamo occurs at the later stages of l-PMS evolution as stars approach the zero-age main sequence.

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Bridging the Gap—The Disappearance of the Intermediate Period Gap for Fully Convective Stars, Uncovered by New ZTF Rotation Periods

Cited by 25 publications

References 71 publications

Temporal variation of the photometric magnetic activity for the Sun andKeplersolar-like stars

Temporal variation of the photometric magnetic activity for the Sun andKeplersolar-like stars

Mind the Gap. I. Hα Activity of M Dwarfs Near the Partially/Fully Convective Boundary and a New Hα Emission Deficiency Zone on the Main Sequence

Magnetic Activity–Rotation–Age–Mass Relations in Late-pre-main-sequence Stars

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