HDE 245059: A WEAK-LINED T TAURI BINARY REVEALED BY CHANDRA AND KECK

Journal Article · Wed May 20 00:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/697/1/493; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21300549

Baldovin-Saavedra, C; Audard, M ^[1]; Duchene, G ^[2]; Guedel, M ^[3]; Skinner, S L ^[4]; Paerels, F B. S. ^[5]; Ghez, A ^[6]; McCabe, C ^[7]

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1. ISDC, Universite de Geneve, Chemin d'Ecogia 16, 1290 Versoix (Switzerland)
2. Laboratoire d'Astrophysique de l'Observatoire de Grenoble, 414 Rue de la Piscine, Domaine Universitaire, BP 53, 38041, Grenoble Cedex 09 (France)
3. Institute of Astronomy, ETH Zuerich, CH-8092 Zuerich (Switzerland)
4. CASA, University of Colorado, 389 UCB, Boulder, CO 80309-0389 (United States)
5. Columbia Astrophysics Laboratory, 550 West 120th Street, New York, NY 10027 (United States)
6. UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States)
7. IPAC, California Institute of Technology, 1200 East California Boulevard Pasadena, CA 91125 (United States)

We present the Chandra High Energy Transmission Grating Spectrometer and Keck observations of HDE 245059, a young weak-lined T Tauri star (WTTS), member of the pre-main-sequence group in the {lambda} Orionis Cluster. Our high spatial resolution, near-infrared observations with Keck reveal that HDE 245059 is in fact a binary separated by 0.''87, probably composed of two WTTS based on their color indices. Based on this new information we have obtained an estimate of the masses of the binary components; {approx}3 M {sub sun} and {approx}2.5 M {sub sun} for the north and south components, respectively. We have also estimated the age of the system to be {approx}2-3 Myr. We detect both components of the binary in the zeroth-order Chandra image and in the grating spectra. The light curves show X-ray variability of both sources and in particular a flaring event in the weaker southern component. The spectra of both stars show similar features: a combination of cool and hot plasma as demonstrated by several iron lines from Fe XVII to Fe XXV and a strong bremsstrahlung continuum at short wavelengths. We have fitted the combined grating and zeroth-order spectrum (considering the contribution of both stars) in XSPEC. The coronal abundances and emission measure distribution for the binary have been obtained using different methods, including a continuous emission measure distribution and a multi-temperature approximation. In all cases we have found that the emission is dominated by plasma between {approx}8 and {approx}15 MK a soft component at {approx}4 MK and a hard component at {approx}50 MK are also detected. The value of the hydrogen column density was low, N {sub H} {approx} 8 x 10{sup 19} cm{sup -2}, likely due to the clearing of the inner region of the {lambda} Orionis cloud, where HDE 245059 is located. The abundance pattern shows an inverse first ionization potential effect for all elements from O to Fe, the only exception being Ca. To obtain the properties of the binary components, a 3-T model was fitted to the individual zeroth-order spectra using the abundances derived for the binary. We have also obtained several line fluxes from the grating spectra. The fits to the triplets show no evidence of high densities. In conclusion, the X-ray properties of the weak-lined T Tau binary HDE 245059 are similar to those generally observed in other weak-lined T Tau stars. Although its accretion history may have been affected by the clearing of the interstellar material around {lambda} Ori, its coronal properties appear to not have been strongly modified.

• OSTI ID: 21300549
• Journal Information: Astrophysical Journal, Vol. 697, Issue 1; Other Information: DOI: 10.1088/0004-637X/697/1/493; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ABUNDANCE
APPROXIMATIONS
BREMSSTRAHLUNG
COLOR
EMISSION
FLARING
HARD COMPONENT
HOT PLASMA
HYDROGEN
IONIZATION POTENTIAL
IRON
MASS
SOFT COMPONENT
SPATIAL RESOLUTION
SPECTRA
SPECTROMETERS
T TAURI STARS
X RADIATION