Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2010-02-25
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
18 pages, 18 figures, accepted for publication in the Astrophysical Journal
Scientific paper
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 broad-band V and I photometry with narrow-band Halpha imaging to: (1) identify all stars with excess Halpha emission; (2) derive their Halpha luminosity L(Halpha); (3) estimate the Halpha emission equivalent width; (4) derive the accretion luminosity L_acc from L(Halpha); and finally (5) obtain the mass accretion rate M_acc from L_acc and the stellar parameters (mass and radius). By selecting stars with photometric accuracy in Halpha better than 15%, the statistical uncertainty on the derived M_acc is typically <17% and is dictated by the precision of the Halpha photometry. Systematic uncertainties, of up to a factor of 3 on the value of M_acc, 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 Halpha line analysis. As an application of our method, we study a field of 9.16 arcmin2 around SN1987A, using existing HST photometry. We identify as bona-fide PMS stars a total of 133 objects with a Halpha excess above the 4 sigma level and a median age of 13.5 Myr. Their median mass accretion rate of 2.6x10-8 Msolar/yr is in excellent agreement with previous determinations based on the U-band excess of the stars in this field, and with the value measured for G-type PMS stars in the Milky Way. Their L_acc shows a strong dependence on their distance from a group of hot massive stars in the field and suggests that the UV radiation of the latter is rapidly eroding the circumstellar discs around PMS stars.
de Marchi Guido
Panagia Nino
Romaniello Martino
No associations
LandOfFree
Photometric determination of the mass accretion rates of pre-main sequence stars. I. Method and application to the SN1987A field does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Photometric determination of the mass accretion rates of pre-main sequence stars. I. Method and application to the SN1987A field, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photometric determination of the mass accretion rates of pre-main sequence stars. I. Method and application to the SN1987A field will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-288678