A deep VLA map of the gamma-ray binary LS I +61303 and its environment

MUNOZ-ARJONILLA, A.; ZABALZA, V.; MARTí, J.; PAREDES, J. M.; SANCHEZ-SUTIL, J.; COMBI, J. A.; LUQUE-ESCAMILLA, P.

University of Manchester, UK

Congreso; From Planets to Dark Energy: the Modern Radio Universe; 2007

The University of Manchester, UK

LS I +61 303 is a gamma-ray binary first detected in 1977 (Gregory & Taylor 1978). It has been studied for last three decades by many authors, with very interesting properties of this system being revealed, ranging from the historically observed 26.5 d periodic radio outbursts of nonthermal nature (Taylor & Gregory 1982) to the recent detection of variable TeV emission with the MAGIC Cherenkov telescope (Albert et al. 2006). There are two main competing models to explain the spectral energy distribution observed in gamma-ray binaries: a microquasar X-ray binary and a non-accreting pulsar interacting with the envelope of the rapidly rotating Be star. In this work, our original motivation was to search for very extended radio features of any kind associated to this system which could help to solve microquasar / pulsar debate. We present a new radio map of LS I +61 303 obtained after combining VLA archive data at 6 cm and covering a field of view of about 12 arc-minute, which probably is the deepest centimetric radio image of this system reported up to date at this wavelength (rms noise about 13 ìJy beam−1). It shows no extended radio features which could be associated to LS I +61 303 at this level of sensitivity. This fact allows us to establish upper limits to the energy content of any possible faint bipolar radio lobes at parsec scales in case they existed. We also report a list of the compact radio sources in the field, some of them not catalogued before, as well as an improved radio image of the planetary nebula WeBo1 (Bond et al. 2003) also observed in this field.ìJy beam−1). It shows no extended radio features which could be associated to LS I +61 303 at this level of sensitivity. This fact allows us to establish upper limits to the energy content of any possible faint bipolar radio lobes at parsec scales in case they existed. We also report a list of the compact radio sources in the field, some of them not catalogued before, as well as an improved radio image of the planetary nebula WeBo1 (Bond et al. 2003) also observed in this field.