Evidence of the Evolved Nature of the B[e] Star MWC137

MURATORE, M. F.; CIDALE, L.; ARIAS, M. L.; KRAUS, M.; OKSALA M. E.; BORGES FERNANDES, M.

ASTRONOMICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2015 vol. 149 p. 1 - 9

0004-6256

The evolutionary phase of B[e] stars is difficult to establish dueto the un certainties in their fundamental parameters. For instance,possible classications for the Galactic B[e] starMWC 137 include pre-main-sequence and post-main-sequence phases, with a large range inluminosity. Our goal is to clarify the evolutionary stage of this peculiarobject, and to study the CO molecular component of its circumstellarmedium. To this purpose, we modeled the CO molecular bands usinghigh-resolution K-band spectra. We nd that MWC137 is surroundedby a detached cool  and dense ring of CO gas orbiting the star with a rotational velocity, projectedto the line of sight, of 84 2 kms -1. We also nd that the molec-ular gas is enriched in the isotope 13C, excluding the classicationof the star as a Herbig Be. The observed isotopic abundance ratio(12C=13C = 25) derived from our modeling is compatible with aproto-PN, main-sequence or supergiant evolutionary phase. However,based on some observable characteristics of MWC137, we proposethat the supergiant scenario seems to be the most plausible. Hence,we suggest that MWC137 could be in an extremely short-lived phase,evolving from a B[e] supergiant to a blue supergiant with a bipolarring nebula.