Research Mentor(s)
Kevin Covey
Description
In the process of accumulating mass (accretion), young stars channel ionized gas from the protoplanetary disk to the stellar surface along magnetic field lines. Upon impacting the photosphere, the gas cools down, recombining and emitting hydrogen spectral lines. Measuring these emission lines allows us to determine the temperature and density of the gas in those accretion streams. This then enables us to test whether those parameters depend on the accretion rate. We present measurements of equivalent widths and line ratios for Brackett (Br) 11 – 20 lines for 3366 observations of 940 pre-main sequence stars observed with APOGEE as of Data Release 17. We identify the subset of stars with strong detections down to Br20, and fit the resulting line ratios to predictions of radiative transfer models. We also estimate physical properties inferred from the strongest accretors, such as electron densities between 1011 and 1012 cm-3. Their temperatures appear to be less constrained, but model fits suggest the excitation temperature is inversely proportional to the electron density. Finally, we describe plans for future work to calibrate the flux within Br11 line as a proxy for the mass accretion rate.
Document Type
Event
Start Date
May 2022
End Date
May 2022
Location
Carver Gym (Bellingham, Wash.)
Department
CSE - Physics and Astronomy
Genre/Form
student projects; posters
Type
Image
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Language
English
Format
application/pdf
Measuring properties of accretion streams from APOGEE spectra
Carver Gym (Bellingham, Wash.)
In the process of accumulating mass (accretion), young stars channel ionized gas from the protoplanetary disk to the stellar surface along magnetic field lines. Upon impacting the photosphere, the gas cools down, recombining and emitting hydrogen spectral lines. Measuring these emission lines allows us to determine the temperature and density of the gas in those accretion streams. This then enables us to test whether those parameters depend on the accretion rate. We present measurements of equivalent widths and line ratios for Brackett (Br) 11 – 20 lines for 3366 observations of 940 pre-main sequence stars observed with APOGEE as of Data Release 17. We identify the subset of stars with strong detections down to Br20, and fit the resulting line ratios to predictions of radiative transfer models. We also estimate physical properties inferred from the strongest accretors, such as electron densities between 1011 and 1012 cm-3. Their temperatures appear to be less constrained, but model fits suggest the excitation temperature is inversely proportional to the electron density. Finally, we describe plans for future work to calibrate the flux within Br11 line as a proxy for the mass accretion rate.