Search results for "T Tauri"
showing 9 items of 79 documents
Rotationally modulated X-ray emission from the accretion shock in CTTS
2011
To study the accretion shocks of classical T Tauri stars (CTTS) we obtained high-resolution X-ray spectra of two CTTS, V2129 Oph and V4046 Sgr, to look for phase-resolved X-ray signatures of shock-heated plasma. The 200 ks Chandra/HETGS observation of V2129 Oph (a 1.35 M sun star, rotating in 6.5 d) covered 0.5 stellar rotation. The 360 ks XMM/RGS observation of V4046 Sgr (a binary system, with two 0.9 M sun components, synchronously rotating in 2.42 d) monitored 2.2 system rotations. The stellar photosphere, magnetic field, and accretion geometry of both stars were constrained by quasi-simultaneous optical monitoring (photometry, spectroscopy, and spectropolarimetry). The cool plasma compo…
Coordinated Optical/X-ray observations of the CTTS V2129 Oph The Chandra View
2011
Young low-mass accreting stars (classical T Tauri stars; CTTSs) possess strong magnetic fields that are responsible for the regulation of the accretion and outflow processes, and the confinement and heating of coronal plasma. Understanding the physics of CTTS magnetospheres and of their interaction with circumstellar disks can elucidate the history and evolution of our own Sun and Solar System, at the stage when planets were being formed. In June 2009 we have conducted an extensive multi-wavelength observing campaign of V2129 Oph, a K5 CTTS in the ρ Ophiuchi molecular cloud, with the goal of obtaining a synoptic view of its photosphere, magnetic field, coronal plasma, and of its accretion s…
Observational diagnostics of accretion on young stars and brown dwarfs
2010
I present a summary of recent observational constraints on the accretion properties of young stars and brown dwarfs with focus on the high-energy emission. In their T Tauri phase young stars assemble a few percent of their mass by accretion from a disk. Various observational signatures of disks around pre-main sequence stars and the ensuing accretion process are found in the IR and optical regime: e.g. excess emission above the stellar photosphere, strong and broad emission lines, optical veiling. At high energies evidence for accretion is less obvious, and the X-ray emission from stars has historically been ascribed to magnetically confined coronal plasmas. While being true for the bulk of…
New view of the corona of classical T Tauri stars: Effects of flaring activity in circumstellar disks
2019
Classical T Tauri stars (CTTSs) are young low-mass stellar objects accreting mass from their circumstellar disks. They are characterized by high levels of coronal activity as revealed by X-ray observations. This activity may affect the disk stability and the circumstellar environment. Here we investigate if an intense coronal activity due to flares occurring close to the accretion disk may perturb the inner disk stability, disrupt the inner part of the disk and, possibly, trigger accretion phenomena with rates comparable with those observed. We model a magnetized protostar surrounded by an accretion disk through 3D magnetohydrodinamic simulations. We explore cases characterized by a dipole …
The magnetosphere of the close accreting PMS binary V4046 Sgr
2013
V4046 Sagittarii AB is a close short-period classical T Tauri binary. It is a circularised and synchronised system accreting from a circumbinary disk. In 2009 it was observed as part of a coordinated program involving near-simultaneous spectropolarimetric observations with ESPaDOnS at the Canada-France-Hawai'i Telescope and high-resolution X-ray observations with XMM-Newton. Magnetic maps of each star were derived from Zeeman-Doppler imaging. After briefly highlighting the most significant observational findings, we present a preliminary 3D model of the binary magnetosphere constructed from the magnetic maps using a newly developed binary magnetic field extrapolation code. The large-scale f…
Surface and Atmospheric Structure on the T Tauri Star V2129 Oph
2011
We provide an overview of a multi-wavelength observing campaign focusing on the accretion and coronal processes in the young star V2129 Oph. V2129 Oph is a classical T Tauri star with a 6.5 day rotation period in the ρ Oph star forming region. On 27-29 June 2009 we obtained two 100 ksec Chandra HETG exposures, aiming at opposite hemispheres of the star. We discuss the X-ray data elsewhere. In order to place the coronal X-ray emission in context, we obtained contemporaneous optical and near-IR photometry and high dispersion optical spectroscopy. The photometry shows the existence of dark photospheric spots. The Hα line profiles show a modulation of the mean Hα velocity and the presence of re…
Stochastic gravito-inertial modes discovered by CoRoT in the hot Be star HD 51452
2012
International audience; Context. Be stars are rapidly rotating stars with a circumstellar decretion disk. They usually undergo pressure and/or gravity pulsation modes excited by the κ-mechanism, i.e. an effect of the opacity of iron-peak elements in the envelope of the star. In the Milky Way, p-modes are observed in stars that are hotter than or equal to the B3 spectral type, while g-modes are observed at the B2 spectral type and cooler. Aims. We observed a B0IVe star, HD 51452, with the high-precision, high-cadence photometric CoRoT satellite and high-resolution, ground-based HARPS and SOPHIE spectrographs to study its pulsations in great detail. We also used the lower resolution spectra a…
High Energy Emission and its Variability in Young Stellar Objects
2019
Young stars show a variety of highly energetic phenomena, from accretion and outflow processes to hot coronal plasmas confined in their outer atmosphere, all regulated by the intense stellar magnetic fields. Many aspects on each of these phenomena are debated, but, most notably, their complex mutual interaction remains obscure. In this work I report how these phenomena are simultaneously responsible for the high-energy emission from young stars, with a special focus on the expected and observed variability in the X-ray band. Investigating variations in the X-ray emission from young stars allows us to pose constraints on flare and coronal plasma properties, coronal heating, accretion stream …
CSI 2264: Simultaneous optical and X-ray variability in the pre-main sequence stars of NGC 2264
2019
Context. Pre-main sequence stars are variable sources. In diskless stars this variability is mainly due to the rotational modulation of dark photospheric spots and active regions, as in main sequence stars even if associated with a stronger magnetic activity.Aims. We aim at analyzing the simultaneous optical and X-ray variability in these stars to unveil how the activity in the photosphere is connected with that in the corona, to identify the dominant surface magnetic activity, and to correlate our results with stellar properties, such as rotation and mass.Methods. We analyzed the simultaneous optical and X-ray variability in stars without inner disks (e.g., class III objects and stars with…