On P-Mode Oscillations in Stars from 1 M⊙ to 2 M⊙

Audard, N.; Provost, J.

doi:10.1007/978-94-011-0950-5_50

Cited by 11 publications

(15 citation statements)

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“…Episodic accretion plays an important role in star formation (Audard et al 2014). In the episodic accretion scenario, a protostellar system stays in a quiescent accretion phase most of the time, and accretion bursts occasionally occur to deliver material onto the central protostar.…”

Section: Introductionmentioning

confidence: 99%

Chronology of Episodic Accretion in Protostars—An ALMA Survey of the CO and H₂O Snowlines

Hsieh

Murillo

Беллоче

et al. 2019

ApJ

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Episodic accretion has been used to explain the wide range of protostellar luminosities, but its origin and influence on the star forming process are not yet fully understood. We present an ALMA survey of N 2 H + (1 − 0) and HCO + (3 − 2) toward 39 Class 0 and Class I sources in the Perseus molecular cloud. N 2 H + and HCO + are destroyed via gas-phase reactions with CO and H 2 O, respectively, thus tracing the CO and H 2 O snowline locations. A snowline location at a much larger radius than that expected from the current luminosity suggests that an accretion burst has occurred in the past which has shifted the snowline outward. We identified 18/18 Class 0 and 9/10 Class I post-burst sources from N 2 H + , and 7/17 Class 0 and 1/8 Class I post-burst sources from HCO + . The accretion luminosities during the past bursts are found to be ∼ 10 − 100 L . This result can be interpreted as either evolution of burst frequency or disk evolution. In the former case, assuming that refreeze-out timescales are 1000 yr for H 2 O and 10,000 yr for CO, we found that the intervals between bursts increases from 2400 yr in the Class 0 to 8000 yr in the Class I stage. This decrease in the burst frequency may reflect that fragmentation is more likely to occur at an earlier evolutionary stage when the young stellar object is more prone to instability.

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Section: Introductionmentioning

confidence: 99%

Chronology of Episodic Accretion in Protostars—An ALMA Survey of the CO and H₂O Snowlines

Hsieh

Murillo

Беллоче

et al. 2019

ApJ

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“…We recall that EXors are pre-main sequence sources that are characterised by outburst events (with typical flux variations of 3−4 mag) that last one year or shorter, with a recurrence time of months to years and present emission line spectra (e.g. Herbig 2008;Lorenzetti et al 2009;Audard et al 2014). One of the targets of the EXORCISM project is V1180 Cas, a young source that belongs to the L1340 star-forming cloud; it Optical and NIR spectra (FITS files) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/565/L7 was first recognised to be a Hα emitter by Kun et al (1994) and was identified as [KOS94] HA11.…”

Section: Introductionmentioning

confidence: 99%

Recent outburst of the young star V1180 Cassiopeiae

Antoniucci

Arkharov

Paola

et al. 2014

A&A

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Aims. We report on the ongoing outburst of the young variable V1180 Cas, which is known to display characteristics in common with EXor eruptive variables. We present results that support the scenario of an accretion-driven nature of the brightness variations of the object and provide the first evidence of jet structures around the source. Methods. We monitored the recent flux variations of the target in the R C , J, H, and K bands. New optical and near-IR spectra taken during the current high state of V1180 Cas are presented, in conjunction with H 2 narrow-band imaging of the source. Results. Observed near-IR colour variations are analogous to those observed in EXors and consistent with excess emission originating from an accretion event. The spectra show numerous emission lines, which indicates accretion, ejection of matter, and an active disc. Using optical and near-IR emission features we derive a mass accretion rate of ∼3 × 10 −8 M yr −1 , which is an order of magnitude lower than previous estimates. In addition, a mass loss rate of ∼4 × 10 −9 and ∼4 × 10 −10 M yr −1 are estimated from atomic forbidden lines and H 2 , respectively. Our H 2 imaging reveals two bright knots of emission around the source and the nearby optically invisible star V1180 Cas B, clearly indicative of mass-loss phenomena. Higher resolution observations of the detected jet will help to clarify whether V1180 Cas is the driving source and to determine the relation between the observed knots.

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“…A number of theories have been proposed to explain the origin of episodic accretion (Audard et al 2014). Of these, the favored origin is accretion bursts driven by disk instability.…”

Section: Introductionmentioning

confidence: 99%

“…YSOs undergoing luminosity outbursts (e.g., FU Orionis and EX Orionis events; Herbig 1966Herbig , 1977 are considered to be direct evidence for episodic accretion (Audard et al 2014). Direct detection of an accretion burst is difficult because of the relatively long time interval between bursts ( 5 10 5 10 3 4´-yr; Scholz et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Probing Episodic Accretion in Very Low Luminosity Objects

Hsieh

Murillo

Беллоче

et al. 2018

ApJ

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Episodic accretion has been proposed as a solution to the long-standing luminosity problem in star formation; however, the process remains poorly understood. We present observations of line emission from N 2 H + and CO isotopologues using the Atacama Large Millimeter/submillimeter Array (ALMA) in the envelopes of eight very low luminosity objects (VeLLOs). In five of the sources the spatial distribution of emission from N 2 H + and CO isotopologues shows a clear anticorrelation. It is proposed that this is tracing the CO snow line in the envelopes: N 2 H + emission is depleted toward the center of these sources, in contrast to the CO isotopologue emission, which exhibits a peak. The positions of the CO snow lines traced by the N 2 H + emission are located at much larger radii than those calculated using the current luminosities of the central sources. This implies that these five sources have experienced a recent accretion burst because the CO snow line would have been pushed outward during the burst because of the increased luminosity of the central star. The N 2 H + and CO isotopologue emission from DCE161, one of the other three sources, is most likely tracing a transition disk at a later evolutionary stage. Excluding DCE161, five out of seven sources (i.e., ∼70%) show signatures of a recent accretion burst. This fraction is larger than that of the Class 0/I sources studied by Jørgensen et al. and Frimann et al., suggesting that the interval between accretion episodes in VeLLOs is shorter than that in Class 0/I sources.

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On P-Mode Oscillations in Stars from 1 M⊙ to 2 M⊙

Cited by 11 publications

References 1 publication

Chronology of Episodic Accretion in Protostars—An ALMA Survey of the CO and H₂O Snowlines

Chronology of Episodic Accretion in Protostars—An ALMA Survey of the CO and H₂O Snowlines

Recent outburst of the young star V1180 Cassiopeiae

Probing Episodic Accretion in Very Low Luminosity Objects

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On P-Mode Oscillations in Stars from 1 M⊙ to 2 M⊙

Cited by 11 publications

References 1 publication

Chronology of Episodic Accretion in Protostars—An ALMA Survey of the CO and H2O Snowlines

Chronology of Episodic Accretion in Protostars—An ALMA Survey of the CO and H2O Snowlines

Recent outburst of the young star V1180 Cassiopeiae

Probing Episodic Accretion in Very Low Luminosity Objects

Contact Info

Product

Resources

About

Chronology of Episodic Accretion in Protostars—An ALMA Survey of the CO and H₂O Snowlines

Chronology of Episodic Accretion in Protostars—An ALMA Survey of the CO and H₂O Snowlines