An Extraordinary Outburst in the Massive Protostellar System NGC 6334I-MM1: Quadrupling of the Millimeter Continuum

Hunter, T. R.; Brogan, C. L.; MacLeod, G. C.; Cyganowski, C. J.; Chandler, Claire J.; Chibueze, James O.; Friesen, Rachel; Indebetouw, R.; Thesner, Cherise; Young, Kenneth H.

doi:10.3847/2041-8213/aa5d0e

Cited by 161 publications

(191 citation statements)

References 48 publications

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“…We conclude that the small flux increase observed at millimetre wavelengths with respect to the (extrapolated) pre-burst literature flux can be entirely due to the free-free emission from the radio jet and not to dust heating by the outburst. This result differs from the (sub)mm brightening detected by Hunter et al (2017) in a similar high-mass YSO (NGC6334I-MM1), also undergoing a maser flare and, possibly, an accretion outburst. Such a lack of brightening in the (sub)mm regime is puzzling given the similarities between the two outbursts.…”

Section: Origin Of the Millimetre Emissioncontrasting

confidence: 92%

Radio outburst from a massive (proto)star

Cesaroni

Moscadelli

Neri

et al. 2018

A&A

102

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Context. Recent observations of the massive young stellar object S255 NIRS 3 have revealed a large increase in both methanol maser flux density and IR emission, which have been interpreted as the result of an accretion outburst, possibly due to instabilities in a circumstellar disk. This indicates that this type of accretion event could be common in young/forming early-type stars and in their lower mass siblings, and supports the idea that accretion onto the star may occur in a non-continuous way. Aims. As accretion and ejection are believed to be tightly associated phenomena, we wanted to confirm the accretion interpretation of the outburst in S255 NIRS 3 by detecting the corresponding burst of the associated thermal jet. Methods. We monitored the radio continuum emission from S255 NIRS 3 at four bands using the Karl G. Jansky Very Large Array. The millimetre continuum emission was also observed with both the Northern Extended Millimeter Array of IRAM and the Atacama Large Millimeter/submillimeter Array. Results. We have detected an exponential increase in the radio flux density from 6 to 45 GHz starting right after July 10, 2016, namely ∼13 months after the estimated onset of the IR outburst. This is the first ever detection of a radio burst associated with an IR accretion outburst from a young stellar object. The flux density at all observed centimetre bands can be reproduced with a simple expanding jet model. At millimetre wavelengths we infer a marginal flux increase with respect to the literature values and we show this is due to free-free emission from the radio jet. Conclusions. Our model fits indicate a significant increase in the jet opening angle and ionized mass loss rate with time. For the first time, we can estimate the ionization fraction in the jet and conclude that this must be low (<14%), lending strong support to the idea that the neutral component is dominant in thermal jets. Our findings strongly suggest that recurrent accretion+ejection episodes may be the main route to the formation of massive stars.

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Section: Origin Of the Millimetre Emissioncontrasting

confidence: 92%

Radio outburst from a massive (proto)star

Cesaroni

Moscadelli

Neri

et al. 2018

A&A

102

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“…We note that the shallower slope for cluster NGC6334-I indicates a larger fraction of massive cores, and this can be linked to the recent burst reported by(Hunter et al 2017). …”

supporting

confidence: 66%

Physical properties of the star-forming clusters in NGC 6334

Sadaghiani

Sánchez-Monge

Schilke

et al. 2020

A&A

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Aims. We aim to characterise certain physical properties of high-mass star-forming sites in the NGC 6334 molecular cloud, such as the core mass function (CMF), spatial distribution of cores, and mass segregation. Methods. We used the Atacama Large Millimetre/sub-millimetre Array (ALMA) to image the embedded clusters NGC 6334-I and NGC 6334-I(N) in the continuum emission at 87.6 GHz. We achieved a spatial resolution of 1300 au, enough to resolve different compact cores and fragments, and to study the properties of the clusters. Results. We detected 142 compact sources distributed over the whole surveyed area. The ALMA compact sources are clustered in different regions. We used different machine-learning algorithms to identify four main clusters: NGC 6334-I, NGC 6334-I(N), NGC 6334-I(NW), and NGC 6334-E. The typical separations between cluster members range from 4 000 au to 12 000 au. These separations, together with the core masses (0.1-100 M ), are in agreement with the fragmentation being controlled by turbulence at scales of 0.1 pc. We find that the CMFs show an apparent excess of high-mass cores compared to the stellar Initial Mass Function. We evaluated the effects of temperature and unresolved multiplicity on the derived slope of the CMF. Based on this, we conclude that the excess of high-mass cores might be spurious and due to inaccurate temperature determinations and/or resolution limitations. We searched for evidence of mass segregation in the clusters and we find that clusters NGC 6334-I and NGC 6334-I(N) show hints of segregation with the most massive cores located in the centre of the clusters. Conclusions. We searched for correlations between the physical properties of the four embedded clusters and their evolutionary stage (based on the presence of H ii regions and infrared sources). NGC 6334-E appears as the most evolved cluster, already harboring a well-developed H ii region. NGC 6334-I is the second-most evolved cluster with an ultra-compact H ii region. NGC 6334-I(N) contains the largest population of dust cores distributed in two filamentary structures and no dominant H ii region. Finally, NGC 6334-I(NW) is a cluster of mainly low-mass dust cores with no clear signs of massive cores or H ii regions. We find a larger separation between cluster members in the more evolved clusters favoring the role of gas expulsion and stellar ejection with evolution. The mass segregation, seen in the NGC 6334-I and NGC 6334-I(N) clusters, suggests a primordial origin for NGC 6334-I(N). In contrast, the segregation in NGC 6334-I might be due to dynamical effects. Finally, the lack of massive cores in the most evolved cluster suggests that the gas reservoir is already exhausted, while the less evolved clusters still have a large gas reservoir along with the presence of massive cores. In general, the fragmentation process of NGC 6334 at large scales (from filament to clump, i.e. at about 1 pc) is likely governed by turbulent pressure, while at smaller scales (scale of cores and sub-fragments, i.e. a few hundred au) ...

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“…Our ALMA data show a submillimeter burst in this object, which lasted about 2 years (Liu et al 2018). An even more impressive burst (with an increase by a factor of ∼ 70 in luminosity but with a lower initial level) was detected in another massive object NGC6334I-MM1 (Hunter et al 2017). These events demonstrate an importance of the episodic disk accretion in the process of high mass star formation.…”

Section: Introductionmentioning

confidence: 96%

Dense Cores, Filaments, and Outflows in the S255IR Region of High-mass Star Formation

Зинченко

Liu

et al. 2020

ApJ

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We investigate at a high angular resolution the spatial and kinematic structure of the S255IR high mass star-forming region, which demonstrated recently the first disk-mediated accretion burst in the massive young stellar object. The observations were performed with ALMA in Band 7 at an angular resolution ∼ 0. 1, which corresponds to ∼ 180 AU. The 0.9 mm continuum, C 34 S(7-6) and CCH N = 4 − 3 data show a presence of very narrow (∼ 1000 AU), very dense (n ∼ 10 7 cm −3 ) and warm filamentary structures in this area. At least some of them represent apparently dense walls around the high velocity molecular outflow with a wide opening angle from the S255IR-SMA1 core, which is associated with the NIRS3 YSO. This wide-angle outflow surrounds a narrow jet. At the ends of the molecular outflow there are shocks, traced in the SiO(8-7) emission. The SiO abundance there is enhanced by at least 3 orders of magnitude. The CO(3-2) and SiO(8-7) data show a collimated and extended high velocity outflow from another dense core in this area, SMA2. The outflow is bent and consists of a chain of knots, which may indicate periodic ejections possibly arising from a binary system consisting of low or intermediate mass protostars. The C 34 S emission shows evidence of rotation of the parent core. Finally, we detected two new low mass compact cores in this area (designated as SMM1 and SMM2), which may represent prestellar objects.

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An Extraordinary Outburst in the Massive Protostellar System NGC 6334I-MM1: Quadrupling of the Millimeter Continuum

Cited by 161 publications

References 48 publications

Radio outburst from a massive (proto)star

Radio outburst from a massive (proto)star

Physical properties of the star-forming clusters in NGC 6334

Dense Cores, Filaments, and Outflows in the S255IR Region of High-mass Star Formation

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