High-resolution polarimetry of Parsamian 21: revealing the structure of an edge-on FUOri disc

Abstract

We present the first high spatial resolution near-infrared direct and polarimetric observations of Parsamian 21, obtained with the Nasmyth Adaptive Optics System-CONICA instrument at the Very Large Telescope (VLT). We complemented these measurements with archival infrared observations, such as Hubble Space Telescope (HST)/Wide Field Planetary Camera 2 (WFPC2) imaging, HST/Near Infrared Camera and Multi-Object Spectrometer (NICMOS) polarimetry, photometry with the Spitzer Space Telescope's Infrared Array Camera (IRAC) and Multiband Imaging Photometer (MIPS), spectroscopy with Spitzer's Infrared Spectrograph (IRS), as well as Infrared Space Observatory (ISO) photometry. Our main conclusions are as follows: (1) we argue that Parsamian 21 is probably an FUOrionis-type object (FUor); (2) Parsamian 21 is not associated with any rich cluster of young stars; (3) our measurements reveal a circumstellar envelope, a polar cavity and an edge-on disc; the disc seems to be geometrically flat and extends from approximately 48 to 360 au from the star; (4) the spectral energy distribution (SED) can be reproduced with a simple model of a circumstellar disc and an envelope; (5) within the framework of an evolutionary sequence of FUors proposed by Green et al. and Quanz et al., Parsamian 21 can be classified as an intermediate-aged object. The results published in this paper are based on data collected at the European Southern Observatory in the frame of the programme P073.C-0721(A). E-mail: kospal@konkoly.hu