On the origin of the O and B-type stars with high velocities

Abstract

Abstract. We use milli-arcsecond accuracy astrometry (proper motions and parallaxes) from Hipparcos and from radio observations to retrace the orbits of 56 runaway stars and nine compact objects with distances less than 700 pc, to identify the parent stellar group. It is possible to deduce the specific formation scenario with near certainty for two cases. (i) We find that the runaway star ζ Ophiuchi and the pulsar PSR J1932+1059 originated about 1 Myr ago in a supernova explosion in a binary in the Upper Scorpius subgroup of the Sco OB2 association. The pulsar received a kick velocity of ∼350 km s −1 in this event, which dissociated the binary, and gave ζ Oph its large space velocity. (ii) Blaauw & Morgan and Gies & Bolton already postulated a common origin for the runaway-pair AE Aur and µ Col, possibly involving the massive highly-eccentric binary ι Ori, based on their equal and opposite velocities. We demonstrate that these three objects indeed occupied a very small volume ∼2.5 Myr ago, and show that they were ejected from the nascent Trapezium cluster. We identify the parent group for two more pulsars: both likely originate in the ∼50 Myr old association Per OB3, which contains the open cluster α Persei. At least 21 of the 56 runaway stars in our sample can be linked to the nearby associations and young open clusters. These include the classical runaways 53 Arietis (Ori OB1), ξ Persei (Per OB2), and λ Cephei (Cep OB3), and fifteen new identifications, amongst which a pair of stars running away in opposite directions from the region containing the λ Ori cluster. Other currently nearby runaways and pulsars originated beyond 700 pc, where our knowledge of the parent groups is very incomplete.

Radio and infrared study of the star-forming region IRAS 20286+4105

“…The derived age is considerably shorter than the main-sequence lifetime of (12 − 16.4) × 10 6 yr (Mottram et al 2011) of the ionizing star which is estimated to be of spectral type between B0 -B05. This difference in the ages is consistent with the fact that runaway stars acquire high velocities after an initial evolutionary phase as member of a close binary system in which the primary evolves for several million years before it explodes as a supernova and the runaway is ejected out of the system (Hoogerwerf, de Bruijne & de Zeeuw 2001). The above analysis suggests that the radio emission seen in the IRAS 20286+4105 cloud is due to a possible runaway star which was likely associated with SNR G079.8+01.2 in the past.…”

“…The other mechanism involves dynamical ejection from a dense cluster (Poveda, Ruiz & Allen 1967;Gies & Bolton 1986). Hoogerwerf, de Bruijne & de Zeeuw (2001) give evidences for both mechanisms based on accurate astrometry observations. Our aim is to first quantitatively attribute the bow-shock mechanism with the observed cometary morphology.…”

To see or not to see a bow shock

“…As for HD 149757, it is a long known runaway star (cf. Hoogerwerfer et al 2001). The determined spacial velocities of HD 24431 and HD 158186 are much lower than the runaway limit, thus the runaway character is uncertain.…”

THE FIRST SPECTROPOLARIMETRIC MONITORING OF THE PECULIAR O4 Ief SUPERGIANT ζ PUPPIS

“…The O4 Ief supergiant ζ Pup (=HD 66811) is the brightest O-type star in the sky with a magnitude V = 2.25. Similar to ζ Ophiuchi, it rotates rather fast with = v i sin 208 km s −1 (Conti & Ebbets 1977), and is a runaway star, which may be a product of a past binary interaction, possibly having had an encounter with the cluster Trumper 10 some 2 Myr ago (Hoogerwerf et al 2001;Schilbach & Röser 2008). The most recent periodicity analysis was presented by Howarth & Stevens (2014), who determined = P  1.780938 0.000093 day using optical photometry obtained with the SMEI (Solar Mass Ejection Imager) instrument on the Coriolis satellite between 2003 and 2006.…”