Mass transport from the envelope to the disk of V346 Nor: a case study for the luminosity problem in an FUor-type young eruptive star

Abstract

A long-standing open issue of the paradigm of low-mass star formation is the luminosity problem: most protostars are less luminous than theoretically predicted. One possible solution is that the accretion process is episodic. FU Ori-type stars (FUors) are thought to be the visible examples for objects in the high accretion state. FUors are often surrounded by massive envelopes, which replenish the disk material and enable the disk to produce accretion outbursts. However, we have insufficient information on the envelope dynamics in FUors, about where and how mass transfer from the envelope to the disk happens. Here we present ALMA observations of the FUor-type star V346 Nor at 1.3 mm continuum and in different CO rotational lines. We mapped the density and velocity structure of its envelope and analyze the results using channel maps, position-velocity diagrams, and spectro-astrometric methods. We found that V346 Nor is surrounded by gaseous material on 10000 au scale in which a prominent outflow cavity is carved. Within the central $\sim$700 au, the circumstellar matter forms a flattened pseudo-disk where material is infalling with conserved angular momentum. Within $\sim$350 au, the velocity profile is more consistent with a disk in Keplerian rotation around a central star of 0.1 $M_{\odot }$. We determined an infall rate from the envelope onto the disk of 6$\times$10${}^{-6}{M}_{\odot }$yr${}^{-1}$, a factor of few higher than the quiescent accretion rate from the disk onto the star, hinting for a mismatch between the infall and accretion rates as the cause of the eruption.

16 pages, 8 figures, published in ApJ

References in corpus (17)

• The Burst Mode of Protostellar Accretion
• Variable protostellar accretion with episodic bursts
• ALMA Observations of Infalling Flows toward the Keplerian Disk around the Class I Protostar L1489 IRS
• Accretion Outbursts in Self-gravitating Protoplanetary Disks
• Circumstellar disks around Herbig Be stars
• ALMA Results of the Pseudodisk, Rotating disk, and Jet in Continuum and HCO+ in the Protostellar System HH 212
• Spitzer-IRS Observations of FU Orionis Objects
• Evolution of dust and ice features around FU Orionis objects
• Transition from the Infalling Envelope to the Keplerian Disk around L1551 IRS 5
• Long-wavelength excesses of FU Orionis objects: flared outer disks or infalling envelopes?
• Multi-wavelength study of the low-luminosity outbursting young star HBC 722
• The ALMA Early Science View of FUor/EXor objects. II. The Very Wide Outflow Driven by HBC 494
• V346 Normae: First post-outburst observations of an FU Orionis star
• Brightness variations of the FUor-type eruptive star V346 Nor
• The Herschel/PACS Point Source Catalogue Explanatory Supplement
• Cold CO gas in the envelopes of FU Orionis-type young eruptive stars
• The Role for the Inner Disk in Mass Accretion to the Star in the Early Phase of Star Formation

Cited by in corpus (14)

• How do stars gain their mass? A JCMT/SCUBA-2 Transient Survey of Protostars in Nearby Star Forming Regions
• Luminosity outburst chemistry in protoplanetary discs: going beyond standard tracers
• Massive compact disks around FU Orionis-type young eruptive stars revealed by ALMA
• V346 Nor: the post-outburst life of a peculiar young eruptive star
• Molecular Mapping of DR Tau's Protoplanetary Disk, Envelope, Outflow, and Large-Scale Spiral Arm
• ALMA Observations of Young Eruptive Stars: continuum disk sizes and molecular outflows
• The outbursting protostar 2MASS~22352345+7517076 and its environment
• An APEX study of molecular outflows in FUor-type stars
• Grain growth in newly discovered young eruptive stars
• Resolving the Binary Components of the Outbursting Protostar HBC 494 with ALMA
• Turn up the light: Radiative efficiency of protostars at birth
• The hot corino-like chemistry of four FUor-like protostars
• Quiescence of an Outburst of a Low-Mass Young Stellar Object: LDN1415-IRS
• Envelope-to-disk mass transport in the FUor-type young eruptive star V346 Normae