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Characterizing the X-Ray Emission of Intermediate-mass Pre-main-sequence Stars

Nuñez, Evan H. and Povich, Matthew S. and Binder, Breanna A. and Townsley, Leisa K. and Broos, Patrick S. (2021) Characterizing the X-Ray Emission of Intermediate-mass Pre-main-sequence Stars. Astronomical Journal, 162 (4). Art. No. 153. ISSN 0004-6256. doi:10.3847/1538-3881/ac0af8.

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We use X-ray and infrared observations to study the properties of three classes of young stars in the Carina Nebula: intermediate-mass (2–5 M_⊙) pre-main-sequence stars (IMPS; i.e., intermediate-mass T Tauri stars), late-B and A stars on the zero-age main sequence (AB), and lower-mass T Tauri stars (TTS). We divide our sources among these three subclassifications and further identify disk-bearing young stellar objects versus diskless sources with no detectable infrared (IR) excess emission using IR (1–8 μm) spectral energy distribution modeling. We then perform X-ray spectral fitting to determine the hydrogen-absorbing column density (N_H), absorption-corrected X-ray luminosity (L_X), and coronal plasma temperature (kT) for each source. We find that the X-ray spectra of both IMPS and TTS are characterized by similar kT and N_H, and on average L_X/L_(bol) ∼ 4 × 10−4. IMPS are systematically more luminous in X-rays (by ∼0.3 dex) than all other subclassifications, with median L_X = 2.5 × 10³¹ erg s⁻¹, while AB stars of similar masses have X-ray emission consistent with TTS companions. These lines of evidence converge on a magnetocoronal flaring source for IMPS X-ray emission, a scaled-up version of the TTS emission mechanism. IMPS therefore provide powerful probes of isochronal ages for the first ∼10 Myr in the evolution of a massive stellar population, because their intrinsic, coronal X-ray emission decays rapidly after they commence evolving along radiative tracks. We suggest that the most luminous (in both X-rays and IR) IMPS could be used to place empirical constraints on the location of the intermediate-mass stellar birth line.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Nuñez, Evan H.0000-0001-5595-757X
Povich, Matthew S.0000-0001-9062-3583
Binder, Breanna A.0000-0002-4955-0471
Townsley, Leisa K.0000-0001-8081-9152
Broos, Patrick S.0000-0002-7872-2025
Additional Information:© 2021. The American Astronomical Society. Received 2021 March 23; revised 2021 June 3; accepted 2021 June 8; published 2021 September 21. We thank K. V. Getman, L. A. Hillenbrand, and E. Alecian for helpful discussions that improved this paper. We thank our referee for thoughtful and helpful comments that improved this paper. This work was supported by the NSF under award CAREER-1454333 and by NASA under Chandra awards G07-18003A/B, GO7-18003A/B, and GO8-9131X and the ACIS Instrument Team contract SV4-74018; these were issued by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. E.H.N. acknowledges prior support from the Cal–Bridge program through NSF award DUE-1356133. E.H.N. acknowledges the support of the NSF Graduate Research Fellowship Program. The scientific results are based in part on observations made by the Chandra X-ray Observatory and published previously in cited articles. This work is based in part on archival data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This publication makes use of data products from the Two-Micron All-Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by NASA and the NSF. Facility: CXO (ACIS); Spitzer (IRAC); CTIO:2MASS. -
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:Young stellar objects; Pre-main sequence stars; T Tauri stars; Single x-ray stars
Issue or Number:4
Classification Code:Unified Astronomy Thesaurus concepts: Young stellar objects (1834); Pre-main sequence stars (1290); T Tauri stars (1681); Single x-ray stars (1461)
Record Number:CaltechAUTHORS:20211011-181259828
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Official Citation:Evan H. Nuñez et al 2021 AJ 162 153
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111354
Deposited By: Tony Diaz
Deposited On:11 Oct 2021 18:31
Last Modified:11 Oct 2021 18:31

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