Large-amplitude photometric variability of the candidate protoplanet TMR-1C

¹ Instituto de Astrofisíca de Canarias, 38200 La Laguna, Tenerife, Spain
e-mail: ege@cab.inta-csic.es
² Centro de Astrobiologa (CSIC/INTA), 28850 Torrejón de Ardoz, Madrid, Spain

Received: 17 January 2010
Accepted: 6 August 2010

Abstract

Context. TMR-1C is a candidate protoplanet that lies at a separation of about 10″ (~1000 AU) from the Class I protobinary TMR-1 (IRAS 04361+2547) located in the Taurus molecular cloud. A narrow filament-like structure was observed in the discovery HST/NICMOS images, extending southeast from the central proto-binary system towards TMR-1C, suggesting a morphology in which the candidate protoplanet may have been ejected from the TMR-1 system. Follow-up low-resolution spectroscopy, however, could not confirm if this object is a protoplanet or a low-luminosity background star.

Aims. We present two epochs of near-infrared photometric observations obtained at the CFHT of TMR-1C. The time span of ~7 years between the two sets of observations provides an opportunity to (a) check for any photometric variability similar to that observed among young stellar objects, which would indicate the youth of this source, and to (b) determine the proper motion.

Results. TMR-1C displays large photometric variability between 1 and 2 mag in both the H- and K_s-bands. From our 2002 observations, we find a (H − K_s) color of 0.3 mag, which is much bluer than the value of 1.3 mag reported by T98 from HST observations. Also, we observe brightening in both the H- and K_s-bands when the colors are bluer; i.e., the object gets redder as it becomes fainter. We have explored the possible origins for the observed variability, and find extinction due to the presence of circumstellar material to be the most likely scenario. The observed large-amplitude photometric variations and the possible presence of a circumstellar disk are strong arguments against this object being an old background star.