2010/02/25 by Guido De Marchi, N. Panagia, Nino Panagia +2
Physics and Astronomy · #Accretion (finance) #Astro and Planetary Science #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Emission spectrum #Photometry (optics) #Physics #Spectral line #Stars #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/715/1/1
18 pages, 18 figures, accepted for publication in the Astrophysical Journal
arxiv created 2010/02/25 · openalex publication_date 2010/04/23 · arxiv updated 2015/05/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We have developed and successfully tested a new self-consistent method to reliably identify pre-main-sequence (PMS) objects actively undergoing mass accretion in a resolved stellar population, regardless of their age. The method does not require spectroscopy and combines broadband V and I photometry with narrowband Hα imaging to (1) identify all stars with excess Hα emission, (2) convert the excess Hα magnitude into Hα luminosity L (Hα), (3) estimate the Hα emission equivalent width, (4) derive the accretion luminosity L acc from L (Hα), and finally (5) obtain the mass accretion rate from L acc and the stellar parameters (mass and radius). By selecting stars with an accuracy of 15% or better in the Hα photometry, the statistical uncertainty on the derived is typically ≲17% and is dictated by the precision of the Hα photometry. Systematic uncertainties, of up to a factor of 3 on the value of , are caused by our incomplete understanding of the physics of the accretion process and affect all determinations of the mass accretion rate, including those based on a spectroscopic Hα line analysis. As an application of our method, we study the accretion process in a field of 9.16 arcmin 2 around SN 1987A, using existing Hubble Space Telescope photometry. We identify as bona fide PMS stars a total of 133 objects with a Hα excess above the 4σ level and a median age of 13.5 Myr. Their median mass accretion rate of 2.6 × 10 −8 M ☉ yr −1 is in excellent agreement with previous determinations based on the U -band excess of the stars in the same field, as well as with the value measured for G-type PMS stars in the Milky Way. The accretion luminosity of these PMS objects shows a strong dependence on their distance from a group of hot massive stars in the field and suggests that the ultraviolet radiation of the latter is rapidly eroding the circumstellar disks around PMS stars.