A very long baseline interferometry detection of the class I protostar IRS 5 in Corona Australis

¹ The Netherlands Institute for Radio Astronomy (ASTRON), 7990- AA Dwingeloo The Netherlands
e-mail: deller@astron.nl
² University of Vienna, Department of Astrophysics, Türkenschanzstraße 17, 1180 Vienna, Austria
³ Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁴ Centro de Radiostronomía y Astrofísica, Universidad Nacional Autónoma de México, 58089 Morelia, Michoacán, Mexico
⁵ Max-Planck–Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Received: 11 January 2013
Accepted: 8 February 2013

Abstract

Aims. Very long baseline interferometry yields physical constraints on the compact radio emission of young stellar objects. At the same time, such measurements can be used for precise astrometric measurements of parallaxes and proper motions. Here, we aimed to make the first detections of very compact radio emission from class I protostars in the Corona Australis star-forming region.

Methods. We have used the Long Baseline Array (LBA) to observe the protostars IRS 5 and IRS 7 in the Corona Australis star-forming region in three separate epochs.

Results. We report the first firm radio detection of a class I protostar using very long baseline interferometry. We have detected the previously known non-thermal source IRS 5b, part of a binary system. IRS 5a and IRS 5N were undetected, as were all sources in the IRS 7 region.

Conclusions. These results underline the unusual nature of IRS 5b as a genuine protostar with confirmed non-thermal radio emission. Also, these observations highlight the potential of the LBA as a tool to provide precision astrometric measurements of individual young stellar objects in southern star-forming regions that are not accessible to the Very Long Baseline Array in the northern hemisphere.