Open AccessAn infrared proper motion study of the Orion bullets
Author(s) -
Lee J.K.,
Burton M. G.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03345.x
Subject(s) - physics , proper motion , astrophysics , infrared , motion (physics) , astronomy , stars , classical mechanics
We report the first infrared proper motion measurements of the Herbig–Haro objects in OMC‐1 using a 4‐yr time baseline. The [Fe ii ]‐emitting bullets are moving of the order of 0.08 arcsec per year, or at about 170 km s −1 . The direction of motion is similar to that inferred from their morphology. The proper motions of H 2 ‐emitting wakes behind the [Fe ii ] bullets, and of newly found H 2 bullets, are also measured. H 2 bullets have smaller proper motion than [Fe ii ] bullets, while H 2 wakes with leading [Fe ii ] bullets appear to move at similar speeds to their associated bullets. A few instances of variability in the emission can be attributed to dense, stationary clumps in the ambient cloud being overrun, setting up a reverse‐oriented bullet. Differential motion between [Fe ii ] bullets and their trailing H 2 wakes is not observed, suggesting that these are not separating, and also that they have reached a steady‐state configuration over at least 100 yr. The most distant bullets have, on average, larger proper motions, but are not consistent with free expansion. Nevertheless, an impulsive, or short‐lived (<<1000 yr), duration for their origin seems likely.