Post-outburst radio observation of the region around McNeil's nebula (V1647 Ori)

Abstract

We present post-outburst (~ 100 days after outburst) radio continuum observation of the region (~ 30' x 30') around McNeil's nebula (V1647 Orionis). The observations were carried out using the Giant Metrewave Radio Telescope (GMRT), India, at 1272 MHz on 2004 Feb 14.5 UT. Although 8 sources have been detected within a circular diameter of 25' centred on V1647 Ori, we did not detect any radio continuum emission from McNeil's nebula. We assign a 5-sigma upper limit of 0.15 mJy/beam for V1647 Ori where the beam size is 5.6" x 2.7". Even at higher frequencies of 4.9 and 8.5 GHz (VLA archival data), no radio emission has been detected from this region. Three scenarios namely, emission from homogeneous HII region, ionised stellar wind and shock ionised gas, are explored in the light of our GMRT upper-limit. For the case of homogeneous HII region, the radius of the emitting region is constrained to be <~ 26 AU corresponding to a temperature >~ 2,500 K, which is consistent with the reported radio and H-alpha emission. In the ionised stellar wind picture, our upper limit of radio emission translates to the ratio of mass loss rate and terminal velocity, (M_dot/v_infinity) < 1.2-1.8 x 10^(-10) (M_sun/yr)/(km/s). On the other hand, if the stellar wind shocks the dense neutral (molecular) cloud, the radio upper limit implies that the fraction of the wind encountering the dense obstacle is <50%. Based on a recent measurement of X-ray outburst and later monitoring, the expected radio emission has been estimated. Using our radio limit, the radius (<~ 36 AU) and electron density (>~ 7.2 x 10^7 cm^(-3) of the radio emitting plasma have been constrained using a two phase medium in pressure equilibrium for a volume filling factor of 0.9.

arXiv commentTo appear in Astronomy and Astrophysics (8 pages including 1 Table and 3 Figures)

References in corpus (11)

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• Mc Neil's Nebula in Orion: The Outburst History
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• The X-ray Luminosities of HH Objects
• Mid-Infrared and Submillimeter Observations of the Illuminating Source of McNeil's Variable Nebula
• Near-Infrared Spectroscopy of McNeil's Nebula Object
• The infrared properties of the new outburst star IRAS 05436-0007 in quiescent phase
• V1647 Ori (IRAS 05436-0007) in Outburst: the First Three Months
• The V1647 Ori (IRAS 05436-0007) Protostar and its Environment
• Enhanced X-ray variability from V1647 Ori, the young star in outburst illuminating McNeil's Nebula
• V1647 Orionis (IRAS 05436-0007) : A New Look at McNeil's Nebula

Cited by in corpus (5)

• V1647 Orionis: One Year into Quiescence
• V1647 Ori: The X-ray Evolution of a Pre-main Sequence Accretion Burst
• V1647 Orionis: Optical Photometric and Spectroscopic Monitoring Through the 2003-2006 Outburst
• Post-Outburst Phase of McNeil's Nebula (V1647 Orionis)
• Re-appearance of McNeil's nebula (V1647 Orionis) and its outburst environment