2010/06/01 by E. Flaccomio, G. Micela, F. Favata +2
Physics and Astronomy · #Astro and Planetary Science #Astrophysics #Astrophysics and Star Formation Studies #Correlation #Light curve #Optics #Physics #Stars #Stellar, planetary, and galactic studies #T Tauri star #X-ray #astro-ph.SR
paper · pdf · doi:10.1051/0004-6361/201014914
4 pages, 1 figure, letter accepted for publication on A&A
arxiv created 2010/06/01 · openalex publication_date 2010/06/01 · arxiv updated 2015/05/19 · openalex created_date 2022/10/01 · openalex updated_date 2026/08/05
<i>Aims. <i/>Optical and X-ray emission from classical T Tauri stars (CTTSs) has long been known to be highly variable. Our long, uninterrupted optical observation of the NGC 2264 region with CoRoT [The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programs, Austria, Belgium, Brazil, Germany, and Spain.] allows the optical variability in CTTS to be studied with unprecedented accuracy and time coverage. Two short Chandra observations obtained during the CoRoT pointing with a separation of 16 days allow us to study whether there is a correlation between optical and X-ray variability on this timescale, thus probing the physical mechanisms driving the variability in both bands.<i>Methods. <i/>We have computed the optical and X-ray fractional variability between the two 30 ks duration windows covered by both the Chandra and CoRoT observations, for a sample of classical and weak line T Tauri stars (WTTSs) in NGC 2264. A scatter plot clearly shows that the variability of CTTSs in the optical and soft X-ray (0.5–1.5 keV) bands is correlated, while no correlation is apparent in the hard (1.5–8.0 keV) band. Also, no correlation in either band is present for WTTSs.<i>Results. <i/>We show that the correlation between soft X-ray and optical variability of CTTSs can be naturally explained in terms of time-variable shading (absorption) from circumstellar material orbiting the star, in a scenario rather similar to the one invoked to explain the observed phenomenology in the CTTS AA Tau. The slope of the observed correlation implies (in the hypothesis of homogeneous shading) a significant dust depletion in the circumstellar material (with a gas-to-dust ratio approximately 5 times lower than the standard value for interstellar material).