6533b836fe1ef96bd12a01bf
RESEARCH PRODUCT
UV variability and accretion dynamics in the young open cluster NGC 2264
Laura VenutiLaura VenutiLaura VenutiJonathan IrwinLynne A. HillenbrandJerome BouvierJerome BouvierGiuseppina MicelaJohn R. StaufferLuisa RebullSilvia H. P. AlencarGiovanni PeresEttore FlaccomioAnn Marie CodyAnn Marie Codysubject
AccretionAstrophysics::High Energy Astrophysical PhenomenaFOS: Physical sciencesAstrophysicsAstrophysics::Cosmology and Extragalactic AstrophysicsSettore FIS/05 - Astronomia E AstrofisicaStars: low-maAstrophysics::Solar and Stellar Astrophysicsaccretion diskAstrophysics::Galaxy AstrophysicsSolar and Stellar Astrophysics (astro-ph.SR)Stars: variables: T TauriPhysicsPhotosphereHerbig Ae/BeAstronomy and AstrophysicsAstronomy and AstrophysicUltraviolet: starAccretion (astrophysics)StarsWavelengthAmplitudeAstrophysics - Solar and Stellar AstrophysicsSpace and Planetary ScienceOpen clusters and associations: individual: NGC 2264Stars: pre-main sequenceAstrophysics::Earth and Planetary AstrophysicsOpen clusterdescription
We explore UV and optical variability signatures for several hundred members of NGC 2264 (3 Myr). We performed simultaneous u- and r-band monitoring over two full weeks with CFHT/MegaCam. About 750 young stars are probed; 40% of them are accreting. Statistically distinct variability properties are observed for accreting and non-accreting cluster members. The accretors exhibit a significantly higher level of variability than the non-accretors, especially in the UV. The amount of u-band variability correlates statistically with UV excess in disk-bearing objects, which suggests that accretion and star-disk interaction are the main sources of variability. Cool magnetic spots, several hundred degrees colder than the photosphere and covering from 5 to 30% of the stellar surface, appear to be the leading factor of variability for the non-accreting stars. In contrast, accretion spots, a few thousand degrees hotter than the photosphere and covering a few percent of the stellar surface, best reproduce the variability of accreting objects. The color behavior is also found to be different between accreting and non-accreting stars. Typical variability amplitudes for accreting members rapidly increase from r to u, which indicates a much stronger contrast at short wavelengths; a lower color dependence in the amplitudes is instead measured for diskless stars. We find that u-band variability on hour timescales is typically about 10% of the peak-to-peak variability on day timescales, while longer term (years) variability is consistent with amplitudes measured over weeks. We conclude that for both accreting and non-accreting stars, the mid-term rotational modulation by spots is the leading timescale for a variability of up to several years. In turn, this suggests that the accretion process is essentially stable over years, although it exhibits low-level shorter term variations in single accretion events.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2015-09-01 |