Abstract:
The Lynds’ Dark Nebula (LDN) 1615/1616 and CB 28 (hereafter L1616) together form a cometary globule located at an angular
distance of about 8◦ west of the Orion OB1 association, aligned roughly along the east–west direction, and showing a distinct
head–tail structure. The presence of massive stars in the Orion belt has been considered to be responsible for the radiation-driven
implosion mode of star formation in L1616. Based on the latest Gaia Early Data Release 3 (EDR3) measurements of the
previously known young stellar objects (YSOs) associated with L1616, we find the distance to this cloud to be 384 ± 5 pc.
We present optical polarimetry towards L1616 that maps the plane-of-sky component of the ambient magnetic field (BPOS)
geometry. Based on the proper motion of the YSOs associated with L1616, we investigate their plane-of-sky motion relative
to the exciting star Ori. Using the Gaia EDR3 measurements of the distances and proper motions of the YSOs, we find two
additional sources comoving with the known YSOs. One comoving source is HD 33056, a B9 star, and the other might be a
young pre-main-sequence star not reported in previous studies. The mean direction of BPOS is found to follow the cloud structure.
This could be the effect of dragging of the magnetic field lines by the impact of the ionizing radiation from Ori. Based on the
pressure exerted on L1616, and the ages of the associated YSOs, we show that it could possibly be the main source of ionization
in L1616, and thus the star formation in it.
