<i>Kepler</i>observations of A–F pre-main-sequence stars in Upper Scorpius: discovery of six new δ Scuti and one γ Doradus stars

Ripepi, V.; Balona, L. A.; Catanzaro, G.; Marconi, M.; Palla, F.; Giarrusso, M.

doi:10.1093/mnras/stv2221

Cited by 20 publications

(31 citation statements)

References 52 publications

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“…If there is just one period, we do not have enough information to classify it as a pulsator beyond just its very short period; none of the objects like this are members. Ripepi et al (2015) identifies EPICs 203931628, 204175508, and 204494885 as δ Scutis and EPIC 204054556 as a γ Dor; these are also identified as pulsators here. Ripepi et al also identify EPIC 204638251 as a δ Scuti, so we have tagged it as a pulsator here.…”

Section: Multiple Periodsmentioning

confidence: 62%

Rotation of Low-mass Stars in Upper Scorpius and ρ Ophiuchus with K2

et al. 2018

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We present an analysis of K2 light curves (LCs) for candidate members of the young Upper Sco (USco) association (∼8 Myr) and the neighboring ρ Oph embedded cluster (∼1 Myr). We establish ∼1300 stars as probable members, ∼80% of which are periodic. The phased LCs have a variety of shapes which can be attributed to physical causes ranging from stellar pulsation and stellar rotation to disk-related phenomena. We identify and discuss a number of observed behaviors. The periods are ∼0.2-30 days with a peak near 2 days and the rapid period end nearing breakup velocity. M stars in the young USco region rotate systematically faster than GK stars, a pattern also present in K2 data for the older Pleiades and Praesepe systems. At higher masses (types FGK), the well-defined period-color relationship for slowly rotating stars seen in the Pleiades and Praesepe systems is not yet present in USco. Circumstellar disks are present predominantly among the more slowly rotating M stars in USco, with few disks in the subday rotators. However, M dwarfs with disks rotate faster on average than FGK systems with disks. For four of these disked M dwarfs, we provide direct evidence for disk locking based on the K2 LC morphologies. Our preliminary analysis shows a relatively mass-independent spin-up by a factor of ∼3.5 between USco and the Pleiades, then mass-dependent spin-down between Pleiades and Praesepe.

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Section: Multiple Periodsmentioning

confidence: 62%

Rotation of Low-mass Stars in Upper Scorpius and ρ Ophiuchus with K2

et al. 2018

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“…They may thus represent "normal" discrete accretion variations and bursts, in contrast to the FU Ori and EX Lup outbursts described above. The NASA K2 mission Campaign 2 observations included the young ρ Ophiuchus molecular cloud region at <1-2 Myr, and the adjacent Upper Scorpius OB association, which is debated from analysis of HR diagrams to be either ∼3-5 Myr based on the low mass stellar population (e.g., Preibisch et al 2002;Herczeg & Hillenbrand 2015) or ∼11 Myr based on the solar and super-solar mass population (Pecaut et al 2012); the latter age is beginning to be favored by results on eclipsing binaries David et al 2016) and asteroseismology (Ripepi et al 2015). By sampling stars with ages comparable to and extending to much older than NGC 2264 (in ρ Oph and Upper Sco, respectively), the K2 time series data can be used to compare accretion burst behavior as a function of age and therefore presumably disk properties which are expected to evolve with time.…”

Section: Introductionmentioning

confidence: 99%

A Continuum of Accretion Burst Behavior in Young Stars Observed by K2

Cody

Hillenbrand

David

et al. 2017

ApJ

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We present 29 likely members of the young ρ Oph or Upper Sco regions of recent star formation that exhibit "accretion burst" type light curves in K2 time series photometry. The bursters were identified by visual examination of their ∼80 day light curves, though all satisfy the M < −0.25 flux asymmetry criterion for burst behavior defined by Cody et al. (2014). The burst sources represent ≈9% of cluster members with strong infrared excess indicative of circumstellar material. Higher amplitude burster behavior is correlated with larger inner disk infrared excesses, as inferred from WISE W 1 − W 2 color. The burst sources are also outliers in their large Hα emission equivalent widths. No distinction between bursters and non-bursters is seen in stellar properties such as multiplicity or spectral type. The frequency of bursters is similar between the younger, more compact ρ Oph region, and the older, more dispersed Upper Sco region. The bursts exhibit a range of shapes, amplitudes (∼10-700%), durations (∼1-10 days), repeat time scales (∼3-80 days), and duty cycles (∼10-100%). Our results provide important input to models of magnetospheric accretion, in particular by elucidating the properties of accretion-related variability in the low state between major longer duration events such as EX Lup and FU Ori type accretion outbursts. We demonstrate the broad continuum of accretion burst behavior in young stars -extending the phenomenon to lower amplitudes and shorter timescales than traditionally considered in the theory of pre-main sequence accretion history.

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“…The advent of continuous, high-cadence, wide-field surveys has transformed our ability to comprehensively and systematically study these systems. The re-purposed Kepler mission, K2 (Howell et al 2014), has already supplied the community with high-precision photometry of the young stellar associations Upper Sco and ρ Oph (Ripepi et al 2015;Ansdell et al 2016b;Scaringi et al 2016;Cody et al 2017;Stauffer et al 2017). Unfortunately, observations from K2 are only taken in one bandpass, and the data are not available until months after they are taken.…”

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confidence: 99%

Identification of Young Stellar Variables with KELT for K2. I. Taurus Dippers and Rotators

Rodriguez

Ansdell

Oelkers

et al. 2017

ApJ

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One of the most well-studied young stellar associations, Taurus-Auriga, was observed by the extended Kepler mission, K2, in the spring of 2017. K2 Campaign 13 (C13) is a unique opportunity to study many stars in this young association at high photometric precision and cadence. Using observations from the Kilodegree Extremely Little Telescope (KELT) survey, we identify "dippers", aperiodic and periodic variables among K2 C13 target stars. This release of the KELT data (lightcurve data in e-tables) provides the community with long-time baseline observations to assist in the understanding of the more exotic variables in the association. Transient-like phenomena on timescales of months to years are known characteristics in the light curves of young stellar objects, making contextual pre-and post-K2 observations critical to understanding their underlying processes. We are providing a comprehensive set of the KELT light curves for known Taurus-Auriga stars in K2 C13. The combined data sets from K2 and KELT should permit a broad array of investigations related to star formation, stellar variability, and protoplanetary environments.

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Keplerobservations of A–F pre-main-sequence stars in Upper Scorpius: discovery of six new δ Scuti and one γ Doradus stars

Cited by 20 publications

References 52 publications

Rotation of Low-mass Stars in Upper Scorpius and ρ Ophiuchus with K2

Rotation of Low-mass Stars in Upper Scorpius and ρ Ophiuchus with K2

A Continuum of Accretion Burst Behavior in Young Stars Observed by K2

Identification of Young Stellar Variables with KELT for K2. I. Taurus Dippers and Rotators

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