DETERMINING THE ACCRETION CRITERION FOR YOUNG ACCRETING LATE-M DWARFS IN NEARBY ASSOCIATIONS
Main Article Content
Abstract
Studying young accreting very low-mass objects (late-M and brown dwarfs) in nearby associations will shed lights into their formation mechanism at different stages. Therefore, the identification of these bona-fide accreting objects is the first important step for further studies. The 10% width of Hα emission profile with a value of about 200 km.s^-1 has widely been used to detect young accreting brown dwarfs in star-forming regions. However, there has not been any independent criterion to verify the accreting and non-accreting nature of the detected objects, especially objects detected in young nearby associations. Based on the Wide Infrared Survey Explorer data, a small sample of previously identified accreting and non-accreting late-M and brown dwarfs in starforming regions and young nearby associations was collected to construct their spectral energy distribution. The results of this study which were based on infrared excesses are aligned with the previous works. It is suggested that the Hα 10% velocity width at 200 km.s^-1 could be applied for identifying accreting very low-mass objects in young associations.
Keywords
brown dwarfs, accretion phase, infrared excess, star formation, very low-mass stars
Article Details
References
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Scholz, A., & Jayawardhana, R. (2006). Variable accretion and outflow in young brown dwarfs. The Astrophysical Journal, 638(2), 1056-1069.
Silverberg, S. M., & Kuchner, M. J. et al. (2016). A New M Dwarf Debris Disk Candidate in a Young Moving Group Discovered with Disk Detective. The Astrophysical Journal Letter, 830(2), L28, 5pp.
White, R. J., & Basri, B. (2003). Very low mass stars and brown dwarfs in Taurus-Auriga. The Astrophysical Journal, 582(2), 1109-1122.
Boucher, A., & Lafrenière, D. et al. (2016). Banyan VIII. New Low-mass stars and Brown Dwarfs with Candidate Circumstellar Disks. The Astrophysical Journal, 832(1), 50, 11pp.
Chabrier, G., & Baraffe, I. (2000). Theory of Low-Mass Stars and Substellar Objects. Annual Review of Astronomy and Astrophysics, 38(1), 337-377.
Fedele, D., & Van den Ancker, M. E. et al. (2010). Timescale of mass accretion in pre-main-sequence stars. Astrophysics and Astronomy, 510, A72, 7pp.
Hartmann, L. W., & Kenyon, S. J. (1990). Optical Veiling, Disk Accretion, and the Evolution of T Tauri Stars. The Astrophysical Journal, 349, 190-196.
Kirkpatrick, J. D., Henry, T. J., & McCarthy, Jr, D. W. (1991). A standard stellar spectral sequence in the red/near-infrared Classes K5 to M9. The Astrophysical Journal Supplement Series, 77, 417-440.
Mohanty, S., Jayawardhana, R., & Barsi, G. (2005). The T Tauri phase down to nearly planetary masses: Echelle spectra of 82 very low mass and brown dwarfs. The Astrophysical Journal, 626(1), 498-522.
Murphy, S. J., Mamajek, E. E., & Bell, C. P. M. (2018). WISE J080822.18-644357.3 - a 45 Myr-old accreting M dwarf hosting a primordial disc. Monthly Notices of the Royal Astronomical Society, 476(3), 3290-3302.
Murphy, S. J., Lawson, W. A., & Bento, J. (2015). New members of the TW Hydrae Association and two accreting M-dwarfs in Scorpius-Centarus. Monthly Notices of the Royal Astronomical Society, 453(3), 2220-2231.
Murphy, S. J., & Lawson, W. A. et al. (2011). Episodic disc accretion in the halo of the “old” premain-sequence cluster η Chamaeleontis. Monthly Notices of the Royal Astronomical Society: Letters, 411(1), L51-L55.
Jayawardhana, R., Mohanty, S. & Basri, G. (2003). Evidence for a T Tauri phase in young brown dwarfs. The Astrophysical Journal, 592(1), 282-287
Jayawardhana, R., & Coffey, J. et al. (2006). Accretion disks around young stars: Lifetimes, disk locking, and variability. The Astrophysical Journal, 648(2), 1206-1218.
Riviere-Marichalar, P., & Elliott, P. et al. (2105), Herschel-PACS obervations of discs in the η Chamaeleontis association. Astronomy and Astrophysics, 584, A22, 15pp.
Scholz, A., & Jayawardhana, R. (2006). Variable accretion and outflow in young brown dwarfs. The Astrophysical Journal, 638(2), 1056-1069.
Silverberg, S. M., & Kuchner, M. J. et al. (2016). A New M Dwarf Debris Disk Candidate in a Young Moving Group Discovered with Disk Detective. The Astrophysical Journal Letter, 830(2), L28, 5pp.
White, R. J., & Basri, B. (2003). Very low mass stars and brown dwarfs in Taurus-Auriga. The Astrophysical Journal, 582(2), 1109-1122.