Observations of V838 Monocerotis in the CO rotational transitions^*

¹ Department for Astrophysics, N. Copernicus Astronomical Centre, Rabiańska 8, 87-100 Toruń, Poland e-mail: tomkam@ncac.torun.pl
² I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany

Received: 31 May 2007
Accepted: 21 September 2007

Abstract

Aims.We investigate the structure of a field around the position of V838 Mon as seen in the lowest CO rotational transitions. We also measure and analyse emission in the same lines at the position of V838 Mon.

Methods.Observations have primarily been done in the ¹²CO 1 and 2 lines using the KOSMA telescope. A field of 3.4 squared degrees has been mapped in the on-the-fly mode in these transitions. Longer integration spectra in the on-off mode have been obtained to study the emission at the position of V838 Mon. Selected positions in the field have also been observed in the ¹²CO 0 transition using the Delingha telescope.

Results.In the observed field we have identified many molecular clouds. They can be divided into two groups from the point of view of their observed radial velocities. One, having V_LSR in the range 18-32 km s^-1, can be identified with the Perseus Galactic arm. The other one, having V_LSR between 44-57 km s^-1, probably belongs to the Norma-Cygnus arm. The radial velocity of V838 Mon is within the second range but the object does not seem to be related to any of the observed clouds. We did not find any molecular buble of a 1° dimension around the position of V838 Mon claimed in van Loon et al. An emission has been detected at the position of the object in the ¹²CO J = 2 1 and 2 transitions. The emission is very narrow (FWHM  1.2 km s^-1) and at V_LSR = 53.3 km s^-1. Our analysis of the data suggests that the emission is probably extended.