scholarly journals An interferometric journey around massive stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 241-251
Author(s):  
Anthony Meilland ◽  
Philippe Stee
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Short Review ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Formation And Evolution ◽  
Circumstellar Environments ◽  
New Generation

AbstractSince the construction in the late nineties of modern facilities such as the VLTI or CHARA, interferometry became a key technique to probe massive stars and their often-complex circumstellar environments. Over the last decade, the development of a new generation of beam combiners for these facilities enabled major breakthroughs in the understanding of the formation and evolution of massive stars. In this short review, we will present few of these advances concerning young stellar objects, binarity, mass loss, and stellar surfaces.

scholarly journals Three generations of stars: a possible case of triggered star formation

2020 ◽  
Vol 496 (1) ◽  
pp. 870-874
Author(s):  
M B Areal ◽  
A Buccino ◽  
S Paron ◽  
C Fariña ◽  
M E Ortega
Keyword(s):  
Star Formation ◽  
Young Stellar Objects ◽  
H Ii Regions ◽  
Stellar Objects ◽  
Three Generations ◽  
The North ◽  
Western Border ◽  
H Ii Region ◽  
New Generation ◽  
North Western

ABSTRACT Evidence for triggered star formation linking three generations of stars is difficult to assemble, as it requires convincingly associating evolved massive stars with H ii regions that, in turn, would need to present signs of active star formation. We present observational evidence for triggered star formation relating three generations of stars in the neighbourhood of the star LS II +26 8. We carried out new spectroscopic observations of LS II +26 8, revealing that it is a B0 III-type star. We note that LS II +26 8 is located exactly at the geometric centre of a semi-shell-like H ii region complex. The most conspicuous component of this complex is the H ii region Sh2-90, which is probably triggering a new generation of stars. The distances to LS II +26 8 and to Sh2-90 are in agreement (between 2.6 and 3 kpc). Analysis of the interstellar medium on a larger spatial scale shows that the H ii region complex lies on the north-western border of an extended H2 shell. The radius of this molecular shell is about 13 pc, which is in agreement with what an O9 V star (the probable initial spectral type of LS II +26 8 as inferred from evolutive tracks) can generate through its winds in the molecular environment. In conclusion, the spatial and temporal correspondences derived in our analysis enable us to propose a probable triggered star formation scenario initiated by the evolved massive star LS II +26 8 during its main-sequence stage, followed by stars exciting the H ii region complex formed in the molecular shell, and culminating in the birth of young stellar objects around Sh2-90.

scholarly journals Far-IR Spectrophotometry of HH Flows with the ISO Long-Wavelength Spectrometer

1997 ◽  
Vol 182 ◽  
pp. 111-120
Author(s):  
R. Liseau ◽  
T. Giannini ◽  
B. Nisini ◽  
P. Saraceno ◽  
L. Spinoglio ◽  
...  
Keyword(s):  
Mass Loss ◽  
Line Emission ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Shock Models ◽  
Ir Spectrophotometry ◽  
Hh Objects ◽  
Loss Rates

Full Iso-Lws spectral scans between about 45 to 190 μm of 17 individual HH objects in 7 star forming regions have revealed essentially only [O I] 63 μm line emission, implying that the Fircooling of these objects is totally dominated by this line alone. In this case, J-shock models can be used to determine the mass loss rates of the HH exciting sources. These mass loss rates are in reasonably good agreement with those estimated for the accompanying CO flows, providing first observational evidence that HH and molecular flows are driven by the same agent. The Lmech – Lbol relation, based on our results with the Lws, implies that young stellar objects of lower mass are loosing mass at relatively higher rates than their more massive counterparts.

scholarly journals Formation and Evolution of Disks Around Young Stellar Objects

2020 ◽  
Vol 216 (3) ◽  
Author(s):  
Bo Zhao ◽  
Kengo Tomida ◽  
Patrick Hennebelle ◽  
John J. Tobin ◽  
Anaëlle Maury ◽  
...  
Keyword(s):  
Young Stellar Objects ◽  
Stellar Objects ◽  
Formation And Evolution

scholarly journals Oi63 Micron–determined Mass‐Loss Rates in Young Stellar Objects

1997 ◽  
Vol 476 (2) ◽  
pp. 771-780 ◽  
Author(s):  
Cecilia Ceccarelli ◽  
Michael R. Haas ◽  
David J. Hollenbach ◽  
Alexander L. Rudolph
Keyword(s):  
Mass Loss ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Loss Rates

scholarly journals e-MERLIN Radio Continuum Measurements of OB Star Winds in CYG OB2

2015 ◽  
Vol 12 (S316) ◽  
pp. 169-170
Author(s):  
Jack Morford ◽  
Raman Prinja ◽  
Danielle Fenech
Keyword(s):  
Mass Loss ◽  
Massive Star ◽  
Massive Stars ◽  
Radial Distance ◽  
Radio Continuum ◽  
Hot Stars ◽  
Cluster Evolution ◽  
First Results ◽  
Formation And Evolution ◽  
Crucial Parameter

AbstractHere, we report on the first results from the e-MERLIN Cyg OB2 Radio Survey (COBRaS), which is designed to exploit e-MERLIN’s enhanced capabilities to conduct deep-field mapping of the tremendously rich Cyg OB2 association. The project aims to deliver the most detailed radio census of the most massive OB association in the northern hemisphere. There exists considerable evidence for clumping in the winds of hot stars, which has hugely important consequences for mass-loss determinations. The amount of mass lost from a massive star is a crucial parameter required for stellar and cluster evolution models that are paramount to our understanding of the formation and evolution of massive star clusters. Presenting some of the first 20cm (L band) detections of massive stars in Cyg OB2, both accurate mass-loss determinations and constraints upon clumping within their winds are made. These data substantially increase the observational detections of the outer wind of massive stars and in combination with other observations at different wavelengths, COBRaS will greatly advance our knowledge of clumping as a function of radial distance around massive stars.

scholarly journals Can we expect the massive discs around young stellar objects class O-I to be a birthplace of planetesimal?

2014 ◽  
Vol 9 (S310) ◽  
pp. 225-226
Author(s):  
Valeriy N. Snytnikov ◽  
Olga P. Stoyanovskaya ◽  
Olga A. Stadnichenko
Keyword(s):  
Variable Mass ◽  
Catalytic Reactions ◽  
Young Stellar Objects ◽  
Solar Mass ◽  
Stellar Objects ◽  
Gravitational Instabilities ◽  
Self Consistent ◽  
Gas Cooling ◽  
Formation And Evolution ◽  
Favorable Conditions

AbstractPossibility of large bodies formation in massive discs of young stellar objects (YSO) class O-I was investigated. On the stage of YSO O-I the whole of factors: chemical composition of gas and solids, chemical catalytic reactions, the disc self-gravitation, the increased ratio of solids to gas surface density, adiabatic gas cooling provides favorable conditions for gravitational instabilities development. We simulated 3D dynamics of gas and dust under self-consistent gravitational field and reproduced the formation and evolution of the disc around the protostar. We found that for stars of Solar mass there are regimes when the disc of variable mass is unstable for the development of fast gravitational instabilities.

Water Masers in the Circumstellar Environments of Young Stellar Objects

1998 ◽  
Vol 115 (4) ◽  
pp. 1599-1609 ◽  
Author(s):  
Lebée S. Grissom Meehan ◽  
Bruce A. Wilking ◽  
Mark J. Claussen ◽  
Lee G. Mundy ◽  
Alwyn Wootten
Keyword(s):  
Young Stellar Objects ◽  
Stellar Objects ◽  
Circumstellar Environments ◽  
Water Masers

scholarly journals Star formation in the Eagle Nebula and NGC 6611

2006 ◽  
Vol 2 (S237) ◽  
pp. 460-460
Author(s):  
J. M. Oliveira ◽  
R. D. Jeffries ◽  
J. Th van Loon
Keyword(s):  
Ionizing Radiation ◽  
Massive Stars ◽  
Environmental Influence ◽  
Mass Function ◽  
Initial Mass Function ◽  
Young Stellar Objects ◽  
Low Mass Stars ◽  
Stellar Objects ◽  
Eagle Nebula ◽  
Disk Evolution

AbstractWe present IZJHKL′ photometry of the core of the cluster NGC 6611 in the Eagle Nebula. This photometry is used to constrain the Initial Mass Function (IMF) and the circumstellar disk frequency of the young stellar objects. Optical spectroscopy of 258 objects is used to confirm membership and constrain contamination as well as individual reddening estimates. Our overall aim is to assess the influence of the ionizing radiation from the massive stars on the formation and evolution of young low-mass stars and their disks. The disk frequency determined from the JHKL′ colour-colour diagram suggests that the ionizing radiation from the massive stars has little effect on disk evolution (Oliveira et al. 2005). The cluster IMF seems indistinguishable from those of quieter environments; however towards lower masses the tell-tale signs of an environmental influence are expected to become more noticeable, a question we are currently addressing with our recently acquired ultra-deep (ACS and NICMOS) HST images.

scholarly journals The Evolution of Massive Stars: The Production of “Single” WR Stars

1982 ◽  
Vol 99 ◽  
pp. 323-341 ◽  
Author(s):  
C. Chiosi
Keyword(s):  
Mass Loss ◽  
Turbulent Diffusion ◽  
Massive Stars ◽  
Current Status ◽  
Physical Mechanisms ◽  
Formation And Evolution ◽  
Theoretical Results

In this paper we summarize the basic observational properties of WR stars, and the current status of the evolution of massive stars, giving particular emphasis to those physical mechanisms (mass loss, overshooting, turbulent diffusion…) that may lead O type stars to the WR stage. We consider only those scenarios for WR formation and evolution that have been developed during the last few years and that appear to be sufficiently substanciated by observational and theoretical arguments. Finally, the theoretical results are compared with the observations, pointing out several still unsettled aspects of the problem.

scholarly journals On the structure and kinematics of molecular clouds from large scale mapping of mm-lines

1991 ◽  
Vol 147 ◽  
pp. 11-20
Author(s):  
J. Bally ◽  
W. D. Langer ◽  
R. W. Wilson ◽  
A. A. Stark ◽  
M. W. Pound
Keyword(s):  
Molecular Clouds ◽  
Large Scale ◽  
Massive Stars ◽  
Vital Role ◽  
Solar Neighborhood ◽  
Young Stellar Objects ◽  
Small Scale ◽  
Molecular Gas ◽  
Main Body ◽  
Stellar Objects

Molecular gas in the interior of the Orion superbubble consists of sheets, filaments, and partial shells in which the active star forming dense cloud cores are embedded. The main body of the Orion A and B clouds and at least 14 smaller clouds in Orion region are cometary in appearance suggesting strong interaction with massive stars in the Orion OB association. While the small scale (< 1 pc) structure of the clouds may be determined primarily by internal magnetic fields, gravity, and the effects of outflows from young stellar objects, the large scale morphology and kinematics is affected by the energy injected by massive stars. Supernovae, stellar winds, and radiation have compressed, accelerated, ablated, and dispersed molecular gas over the last 107 years. Most GMC/OB star complexes in the Solar neighborhood exhibit morphological and kinematic properties similar to the Orion region. We argue that energy injection by massive stars plays a vital role in the evolution of the ISM and may be responsible for much of the observed large-scale structure and kinematics of molecular clouds.

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