scholarly journals Young Stellar Objects and Herbig-Haro Objects

1992 ◽  
Vol 45 (4) ◽  
pp. 487
Author(s):  
WJ Zealey
Keyword(s):  
Current Understanding ◽  
Morphological Data ◽  
Young Stellar Objects ◽  
General Mechanism ◽  
Stellar Objects ◽  
Stellar Outflows

Our current understanding of Herbig-Haro objects and their relationship with young stellar outflows is reviewed. The role of multi-waveband observations in the visible, infrared and radio in the study of outflows is discussed with examples drawn from the HH1, HH24 and HH54 outflow complexes. The current theories are briefly considered in the light of spectroscopic and morphological data. It is concluded that although the general mechanism of outflows is understood, the details of the outflowing material's origin and the collimation mechanism remain largely unanswered.

Near Infrared Mapping of Jets and Outflow Cavities Associated with Young Stellar Objects

1993 ◽  
Vol 10 (3) ◽  
pp. 203-207 ◽  
Author(s):  
W.J. Zealey ◽  
M.G. Suters ◽  
P.R. Randall
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
High Spatial Resolution ◽  
Infrared Camera ◽  
Young Stellar Objects ◽  
General Mechanism ◽  
Stellar Objects ◽  
Hydrogen Emission ◽  
First Time

AbstractOur current understanding of Herbig-Haro objects and their relationship with outflows and Pre-Main-Sequence objects is limited. Although the general mechanism of outflows is understood, the detailed questions concerning the outflowing material’s origin and the collimation mechanisms remain largely unanswered. The role of multi-waveband observations (visible, infrared and radio) is vital to our understanding of the shock dynamics of outflows.This paper discusses high spatial resolution near infrared maps of three outflow complexes, HH34, HH46/HH47 and HH54, made using the Anglo Australian Observatory’s infrared camera, IRIS. For the first time molecular hydrogen emission is observed associated with the edges of outflow cavities. In the cases of HH46/47 and to a lesser extent HH34 molecular emission is seen coincident with highly collimated jets feeding the outflow cavities.

Magnetic Fields and Disks in Star-forming Regions

1993 ◽  
Vol 10 (3) ◽  
pp. 247-249 ◽  
Author(s):  
C.M. Wright ◽  
D.K. Aitken ◽  
C.H. Smith ◽  
P.F. Roche
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Transverse Component ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Molecular Outflow ◽  
The Magnetic Field

AbstractThe star-formation process is an outstanding and largely unsolved problem in astrophysics. The role of magnetic fields is unclear but is widely considered to be important at all stages of protostellar evolution, from cloud collapse to ZAMS. For example, in some hydromagnetic models, the field may assist in removing angular momentum, thereby driving accretion and perhaps bipolar outflows.Spectropolarimetry between 8 and 13μm provides information on the direction of the transverse component of a magnetic field through the alignment of dust grains. We present results of 8–13μm spectropolarimetric observations of a number of bipolar molecular outflow sources, and compare the field directions observed with the axes of the outflows and putative disk-like structures observed to be associated with some of the objects. There is a strong correlation, though so far with limited statistics, between the magnetic field and disk orientations. We compare our results with magnetic field configurations predicted by current models for hydromagnetically driven winds from the disks around Young Stellar Objects (YSOs). Our results appear to argue against the Pudritz and Norman model and instead seem to support the Uchida and Shibata model.

scholarly journals MAGNETIC FIELD EFFECTS NEAR THE LAUNCHING REGION OF ASTROPHYSICAL JETS

2010 ◽  
Vol 19 (06) ◽  
pp. 729-739 ◽  
Author(s):  
E. M. DE GOUVEIA DAL PINO ◽  
G. KOWAL ◽  
L. H. S. KADOWAKI ◽  
P. PIOVEZAN ◽  
A. LAZARIAN
Keyword(s):  
Magnetic Field ◽  
Active Galactic Nuclei ◽  
Magnetic Energy ◽  
Galactic Nuclei ◽  
Young Stellar Objects ◽  
Magnetic Field Effects ◽  
Astrophysical Jets ◽  
Stellar Objects ◽  
Fundamental Properties

One of the fundamental properties of astrophysical magnetic fields is their ability to change topology through reconnection and in doing so, to release magnetic energy, sometimes violently. In this work, we review recent results on the role of magnetic reconnection and associated heating and particle acceleration in jet/accretion disk systems, namely young stellar objects (YSOs), microquasars, and active galactic nuclei (AGNs).

scholarly journals Mass Accretion Processes in Young Stellar Objects: Role of Intense Flaring Activity

2014 ◽  
Vol 1 (1) ◽  
pp. 108-112
Author(s):  
Salvatore Orlando ◽  
Fabio Reale ◽  
Giovanni Peres ◽  
Andrea Mignone
Keyword(s):  
Circumstellar Disks ◽  
Young Stellar Objects ◽  
Disk System ◽  
Low Mass Stars ◽  
Stellar Objects ◽  
Low Mass ◽  
The Stability ◽  
Circumstellar Environment ◽  
Magnetospheric Accretion

According to the magnetospheric accretion scenario, young low-mass stars are surrounded by circumstellar disks which they interact with through accretion of mass. The accretion builds up the star to its nal mass and is also believed to power the mass out ows, which may in turn have a signicant role in removing the excess angular momentum from the star-disk system. Although the process of mass accretion is a critical aspect of star formation, some of its mechanisms are still to be fully understood. On the other hand, strong  aring activity is a common feature of young stellar objects (YSOs). In the Sun, such events give rise to perturbations of the interplanetary medium. Similar but more energetic phenomena occur in YSOs and may in uence the circumstellar environment. In fact, a recent study has shown that an intense flaring activity close to the disk may strongly perturb the stability of circumstellar disks, thus inducing mass accretion episodes (Orlando et al. 2011). Here we review the main results obtained in the eld and the future perspectives.

scholarly journals Circumstellar maher of young low-mass stars: Observations versus theory

1987 ◽  
Vol 122 ◽  
pp. 23-38 ◽  
Author(s):  
Claude Bertout
Keyword(s):  
T Tauri Stars ◽  
Young Stellar Objects ◽  
Low Mass Stars ◽  
Stellar Objects ◽  
Star Forming ◽  
T Tauri ◽  
Region I ◽  
Low Mass ◽  
Infrared Sources

After presenting NGC 7129 as a prototypical star-forming region, I discuss what can be learned from the radio spectra of embedded infrared sources. I then review available observational evidence for disks around young stellar objects, with emphasis on accretion disks around T Tauri stars. Finally, new results on the role of magnetic fields in the circumstellar activity of T Tauri stars are presented.

JET MODELS FOR NEUTRON STAR X-RAY BINARIES

2012 ◽  
Vol 08 ◽  
pp. 108-113 ◽  
Author(s):  
SIMONE MIGLIARI ◽  
GABRIELE GHISELLINI ◽  
JAMES MILLER-JONES ◽  
DAVID RUSSELL
Keyword(s):  
Neutron Star ◽  
Compact Object ◽  
Young Stellar Objects ◽  
Jet Formation ◽  
Stellar Objects ◽  
X Ray ◽  
The Status ◽  
Observational Knowledge ◽  
X Ray Binaries

A variety of different models for jet formation have been developed over the years (mainly) for black hole systems and young stellar objects. Conclusive observational constraints which would favor one particular mechanism are difficult to obtain. Neutron star X-ray binaries are crucial for advancing our understanding of jet formation in general, building a bridge between the two most studied jet-producing classes of systems: black holes, i.e. non-magnetized, relativistic objects, and young stellar objects, i.e. non-relativistic, magnetized stars. I will briefly review the status of our observational knowledge of jets in neutron star X-ray binaries, with a focus on the parameters which might be involved in the production of jets. I will present recent works and current observational programs aiming to quantify the role of the compact object in the formation of jets in neutron star systems. Finally, I will test a jet model developed for young stellar objects, the X–wind model, on a neutron star system.

scholarly journals A study of radial self-similar non-relativistic MHD outflow models: parameter space exploration and application to the water fountain W43A

2020 ◽  
Vol 501 (2) ◽  
pp. 2071-2090
Author(s):  
C Ceccobello ◽  
M H M Heemskerk ◽  
Y Cavecchi ◽  
W H T Vlemmings ◽  
D Tafoya
Keyword(s):  
Young Stellar Objects ◽  
Parameter Study ◽  
Rotating Disc ◽  
Stellar Objects ◽  
Global Properties ◽  
Wide Range ◽  
Astrophysical Objects ◽  
Self Similar ◽  
Water Maser

ABSTRACT Outflows, spanning a wide range of dynamical properties and spatial extensions, have now been associated with a variety of accreting astrophysical objects, from supermassive black holes at the core of active galaxies to young stellar objects. The role of such outflows is key to the evolution of the system that generates them, for they extract a fraction of the orbiting material and angular momentum from the region close to the central object and release them in the surroundings. The details of the launching mechanism and their impact on the environment are fundamental to understand the evolution of individual sources and the similarities between different types of outflow-launching systems. We solve semi-analytically the non-relativistic, ideal, magnetohydrodynamics equations describing outflows launched from a rotating disc threaded with magnetic fields using our new numerical scheme. We present here a parameter study of a large sample of new solutions. We study the different combinations of forces that lead to a successfully launched jet and discuss their global properties. We show how these solutions can be applied to the outflow of the water fountain W43A for which we have observational constraints on magnetic field, density and velocity of the flow at the location of two symmetrical water maser emitting regions.

scholarly journals COBRaS: The e-MERLIN 21 cm Legacy survey of Cygnus OB2

2020 ◽  
Vol 637 ◽  
pp. A64
Author(s):  
J. C. Morford ◽  
D. M. Fenech ◽  
R. K. Prinja ◽  
R. Blomme ◽  
J. A. Yates ◽  
...  
Keyword(s):  
Binary Systems ◽  
Massive Stars ◽  
Critical Role ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Enhanced Sensitivity ◽  
Transient Sources ◽  
First Time ◽  
Colliding Winds

Context. The role of massive stars is central to an understanding of galactic ecology. It is important to establish the details of how massive stars provide radiative, chemical, and mechanical feedback in galaxies. Central to these issues is an understanding of the evolution of massive stars, and the critical role of mass loss via strongly structured winds and stellar binarity. Ultimately, and acting collectively, massive stellar clusters shape the structure and energetics of galaxies. Aims. We aim to conduct high-resolution, deep field mapping at 21 cm of the core of the massive Cygnus OB2 association and to characterise the properties of the massive stars and colliding winds at this waveband. Methods. We used seven stations of the e-MERLIN radio facility, with its upgraded bandwidth and enhanced sensitivity to conduct a 21 cm census of Cygnus OB2. Based on 42 hours of observations, seven overlapping pointings were employed over multiple epochs during 2014 resulting in 1σ sensitivities down to ∼21 μJy and a resolution of ∼180 mas. Results. A total of 61 sources are detected at 21 cm over a ∼0.48° × 0.48° region centred on the heart of the Cyg OB2 association. Of these 61 sources, 33 are detected for the first time. We detect a number of previously identified sources including four massive stellar binary systems, two YSOs, and several known X-ray and radio sources. We also detect the LBV candidate (possible binary system) and blue hypergiant star of Cyg OB2 #12. Conclusions. The 21 cm observations secured in the COBRaS Legacy project provide data to constrain conditions in the outer wind regions of massive stars; determine the non-thermal properties of massive interacting binaries; examine evidence for transient sources, including those associated with young stellar objects; and provide unidentified sources that merit follow-up observations. The 21 cm data are of lasting value and will serve in combination with other key surveys of Cyg OB2, including Chandra and Spitzer.

scholarly journals Crystalline silicate absorption at 11.1 μm: ubiquitous and abundant in embedded YSOs and the interstellar medium

2020 ◽  
Vol 493 (3) ◽  
pp. 4463-4517 ◽  
Author(s):  
Tho Do-Duy ◽  
Christopher M Wright ◽  
Takuya Fujiyoshi ◽  
Alistair Glasse ◽  
Ralf Siebenmorgen ◽  
...  
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Mass Fraction ◽  
Cosmic Ray ◽  
Young Stellar Objects ◽  
Absorption Feature ◽  
H Ii Regions ◽  
Stellar Objects ◽  
Stellar Outflows ◽  
T Tauri

ABSTRACT Utilizing several instruments on 4–8 m telescopes, we have observed a large sample of objects in the mid-infrared (8–13 μm). These comprise a few evolved stars, multiple envelopes of embedded young stellar objects (YSOs) or compact H-II regions, and several sightlines through the interstellar medium (ISM). The latter is where dust resides – and is potentially modified – between its formation in evolved stellar outflows and deposition in molecular clouds. In most objects, we detect not only the well-known 9.7 μm absorption feature of amorphous silicates but also a second absorption band around 11.1 μm whose carrier is attributed to crystalline forsterite. We propose that crystalline silicates are essentially ubiquitous in the ISM and earliest phases of star formation, and are evolutionary precursors to T-Tauri and Herbig stars where such silicates have been commonly found. Modelling shows that in most YSOs, H-II regions and ISM cases, the forsterite mass fraction is between 1 and 2 per cent, suggesting that the younger phases inherit their abundance from the ISM. However, several sources show much stronger features (abundances ≥3 per cent). This suggests that significant processing, perhaps crystallization by thermal annealing, occurs early on in star formation. Most intriguing is the first detection of crystalline silicate in the diffuse ISM. We propose that our observed abundance is consistent with a mass fraction of crystalline silicates of 10–20 per cent injected into the ISM, along with commonly accepted lifetimes against their destruction, but only if cosmic ray-induced amorphization is insignificant over a few Giga years.

scholarly journals Ice chemistry in massive young stellar objects: the role of metallicity

2010 ◽  
Vol 411 (1) ◽  
pp. L36-L40 ◽  
Author(s):  
J. M. Oliveira ◽  
J. Th. van Loon ◽  
G. C. Sloan ◽  
R. Indebetouw ◽  
F. Kemper ◽  
...  
Keyword(s):  
Young Stellar Objects ◽  
Stellar Objects ◽  
Ice Chemistry
Sign in / Sign up

Export Citation Format

Share Document