FORMATION OF THE UNEQUAL-MASS BINARY PROTOSTARS IN L1551NE BY ROTATIONALLY DRIVEN FRAGMENTATION

ABSTRACT We present observations at 7 mm that fully resolve the two circumstellar disks and a reanalysis of archival observations at 3.5 cm that resolve along their major axes the two ionized jets of the Class I binary protostellar system L1551NE. We show that the two circumstellar disks are better...

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Bibliographic Details
Published in:The Astrophysical journal 2016-11, Vol.831 (1), p.90
Main Authors: Lim, Jeremy, Hanawa, Tomoyuki, Yeung, Paul K. H., Takakuwa, Shigehisa, Matsumoto, Tomoaki, Saigo, Kazuya
Format: Article
Language:English
Subjects:
Accretion disks
Angular momentum
Astrophysics
binaries: close
binaries: visual
Circular orbits
circumstellar matter
Forecasting
Fragmentation
Power law
Protostars
Star formation
stars: formation
stars: jets
stars: protostars
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Summary:ABSTRACT We present observations at 7 mm that fully resolve the two circumstellar disks and a reanalysis of archival observations at 3.5 cm that resolve along their major axes the two ionized jets of the Class I binary protostellar system L1551NE. We show that the two circumstellar disks are better fit by a shallow inner and steep outer power law than a truncated power law. The two disks have very different transition radii between their inner and outer regions of ∼18.6 au and ∼8.9 au, respectively. Assuming that they are intrinsically circular and geometrically thin, we find that the two circumstellar disks are parallel with each other and orthogonal in projection to their respective ionized jets. Furthermore, the two disks are closely aligned if not parallel with their circumbinary disk. Over an interval of ∼10 yr, source B (possessing the circumsecondary disk) has moved northward with respect to and likely away from source A, indicating an orbital motion in the same direction as the rotational motion of their circumbinary disk. All the aforementioned elements therefore share the same axis for their angular momentum, indicating that L1551NE is a product of rotationally driven fragmentation of its parental core. Assuming a circular orbit, the relative disk sizes are compatible with theoretical predictions for tidal truncation by a binary system having a mass ratio of ∼0.2, in agreement with the reported relative separations of the two protostars from the center of their circumbinary disk. The transition radii of both disks, however, are a factor of 1.5 smaller than their predicted tidally truncated radii.
ISSN:0004-637X
1538-4357
DOI:10.3847/0004-637X/831/1/90