A study of the Orion cometary cloud L1616

With its cometary appearance and a reflection nebula near its edge facingsome bright Orion stars, the Lynd's cloud L1616 shows ample evidence for beingaffected by one or more of these massive stars. To estimate its mass and starformation efficiency as well as to determine if it is gravitationally bound, wemapped this cloud in J=1${\rightarrow}$0 transitions of $^{12}$CO and$^{13}$CO. It is found that the distribution of the emission in the line {\itwings} show clear evidence for substantial mass motions. Also, the ``virial''mass of the cloud is found to be five times the actual cloud mass determinedfrom the $^{13}$CO column density map. It is argued that this cloud hasabnormally high star formation efficiency and is possibly disintegrating. Themorphology and the location of the cloud indicate that it is being affected bythe star ${\epsilon}$ Orionis which is also possibly responsible for thecloud's unusual star formation efficiency. Over a range of values of therelevant parameters, the star is found to quantitatively satisfy therequirements of being the cause of the observed characteristics of the cloud.Comment: 13 pages,latex,8 figures in self-unpacking, uuencoded, compressed postscript; accepted by MNRA