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X-ray properties of protostars in the Orion Nebula

Prisinzano, L. and Micela, G. and Flaccomio, E. and Stauffer, J. R. and Megeath, T. and Rebull, L. and Robberto, M. and Smith, K. and Feigelson, E. D. and Grosso, N. and Wolk, S. (2008) X-ray properties of protostars in the Orion Nebula. Astrophysical Journal, 677 (1). pp. 401-424. ISSN 0004-637X.

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The origin and evolution of the X-ray emission in very young stellar objects (YSOs) are not yet well understood because it is very hard to observe YSOs in the protostellar phase. Using COUP data, we study the X-ray properties of stars in the ONC in different evolutionary classes: luminosities, hydrogen column densities N_H, effective plasma temperatures, and time variability are compared to understand if the interaction between the circumstellar material and the central object can influence the X-ray emission. We have assembled the deepest and most complete photometric catalog of objects in the ONC region from the UV to 8 µm using data from the HST Treasury Program; deep and almost simultaneous UBVI and JHK images taken, respectively, with WFI at ESO 2.2 m and ISPI at CTIO 4 m telescopes; and Spitzer IRAC imaging. We select high-probability candidate Class 0-I protostars, a sample of "bona fide" Class II stars, and a set of Class III stars with IR emission consistent with normal photospheres. Our principal result is that Class 0-Ia objects are significantly less luminous in X-rays, in both the total and hard bands, than the more evolved Class II stars with mass larger than 0.5M⊙; the latter show X-ray luminosities similar to those of Class 0-Ib stars. This result supports the hypothesis that the onset of X-ray emission occurs at a very early stage of star formation. Spectral properties of Class 0-I stars are similar to those of the more evolved Class II and III objects, except for a larger absorption likely due to gas in the envelope or disk of the protostellar objects. Our data suggest that the three different classes have similar X-ray temporal variability.

Item Type:Article
Related URLs:
URLURL TypeDescription
Micela, G.0000-0002-9900-4751
Flaccomio, E.0000-0002-3638-5788
Stauffer, J. R.0000-0003-3595-7382
Megeath, T.0000-0001-7629-3573
Rebull, L.0000-0001-6381-515X
Feigelson, E. D.0000-0002-5077-6734
Wolk, S.0000-0002-0826-9261
Additional Information:© 2008 The American Astronomical Society. Received 2007 November 5; accepted 2007 December 17. This work is based on observations made with Hubble Space Telescope and the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory (JPL), California Institute of Technology under a contract with NASA. Partial support for this work was provided by ASI-INAF I/088/06/0 contract and by NASA through an award issued by JPL/Caltech. E. D. F. is supported by NASA contract NAS8-38252. This research has made use of NASA’s Astrophysics Data System (ADS) Abstract Service and of the SIMBAD database, operated at CDS, Strasbourg, France. This research has also made use of data products from the Two Micron All Sky Survey (2MASS), which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, funded by the National Aeronautics and Space Administration and the National Science Foundation. These data were served by the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We wish to thank Francesco Damiani and Konstantin Getman for helpful discussions. We also thank the anonymous referee for suggestions that helped improve this paper.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Agenzia Spaziale Italiana (ASI)I/088/06/0
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Subject Keywords:open clusters and associations: general; open clusters and associations: individual (Orion Nebula Cluster); stars: activity; stars: pre-main-sequence; X-rays: stars
Issue or Number:1
Record Number:CaltechAUTHORS:PRIapj08
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13399
Deposited By: Tony Diaz
Deposited On:07 May 2009 22:36
Last Modified:02 Nov 2019 17:20

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