Post-Outburst Observations of V1647 Ori: Detection of a Brief Warm, Molecular Outflow

TL;DR

This study reports the detection of a brief warm molecular outflow in V1647 Ori following its outburst, revealing transient blue-shifted CO absorption lines that provide insights into post-outburst stellar activity.

Contribution

First detection of a short-lived warm molecular outflow in V1647 Ori using CO spectra, highlighting transient outflow phenomena after stellar outbursts.

Findings

Blue-shifted CO absorption lines observed in 2006 February

Outflow velocity of approximately 30 km/s

Outflow temperature around 700 K

Abstract

We present new observations of the fundamental ro-vibrational CO spectrum of V1647 Ori, the young star whose recent outburst illuminated McNeil's Nebula. Previous spectra, acquired during outburst in 2004 February and July, had shown the CO emission lines to be broad and centrally peaked-similar to the CO spectrum of a typical classical T Tauri star. In this paper, we present CO spectra acquired shortly after the luminosity of the source returned to its pre-outburst level (2006 February) and roughly one year later (2006 December and 2007 February). The spectrum taken in 2006 February revealed blue-shifted CO absorption lines superimposed on the previously observed CO emission lines. The projected velocity, column density, and temperature of this outflowing gas was 30 km/s, 3^{+2}_{-1}E18 cm^{-2$, and 700^{+300}_{-100} K, respectively. The absorption lines were not observed in the 2006 December and 2007 February data, and so their strengths must have decreased in the interim by a factor of 9 or more. We discuss three mechanisms that could give rise to this unusual outflow.