Infrared Spectroscopic Survey of Class I Sources: Magnetic field measurements of protostars

Christian Flores^1,2*, Michael Connelley², Bo Reipurth², Adwin Boogert²

¹Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
²Institute for Astronomy, University of Hawaii at Manoa, Honolulu, USA

* Presenter:Christian Flores, email:caflores@asiaa.sinica.edu.tw

In the early phases of stellar evolution, magnetic fields play a fundamental role in the star-disk interaction. Although magnetic fields have been measured for T Tauri stars, little is known about the magnetic fields of protostellar sources. We perform the first magnetic field survey of Class I sources, obtaining spectra of 53 protostars. We modeled their spectra and measured magnetic field strengths, temperatures, and gravities. These physical properties are put in context by comparing them to the properties of T Tauri stars. Our findings are: 1) the protostars' average magnetic field strength is similar to the average magnetic field strength of T Tauri sources; 2) the average gravity of protostars is lower than that of T Tauri stars. Using evolutionary models, we deduce that Class I protostars have a median age of ~0.6 Myr and are, as a group, younger than the T Tauri sources with a median age of 3 Myr. Our measurements show that magnetic field strength does not change between the protostellar and the young T Tauri phases. These results confirm that protostellar sources have strong magnetospheres, and they accrete disk material similarly to their more evolved T Tauri counterparts.

Keywords: Stellar magnetic fields, Pre-main sequence stars, High resolution spectroscopy