MHD simulations of accretion onto a dipolar magnetosphere

Zanni, C.; Ferreira, J.

doi:10.1051/0004-6361/201220168

Cited by 212 publications

(276 citation statements)

References 65 publications

Supporting

Mentioning

252

Contrasting

Unclassified

Order By: Relevance

“…MHD disk winds have been associated to the LVC of the TTS forbidden lines (Kwan & Tademaru 1995), because at their base, when the disk material becomes unbound, they have high density and low velocities (see, e.g., Ferreira et al 2006;Suzuki & Inutsuka 2009;Bai & Stone 2013;Zanni & Ferreira 2013;Lesur et al 2013;Fromang et al 2013;Bai 2014;Kurosawa & Romanova 2012). It is, however, very difficult to estimate whether any of these models can explain the observed properties of the LVC emitting region derived in this paper or, even more, to use the observations to discriminate between the various mechanisms that can trigger an MHD wind and constrain the model parameters.…”

Section: Wind Modelsmentioning

confidence: 99%

X-shooter spectroscopy of young stellar objects

Natta

Testi

Alcalá

et al. 2014

A&A

126

View full text Add to dashboard Cite

Disks around T Tauri stars are known to lose mass, as best shown by the profiles of the forbidden emission lines of low-ionization species. At least two separate kinematic components have been identified, one characterized by velocity shifts of tens to hundreds of km s −1 (HVC) and one with a much lower velocity of a few km s −1 (LVC). The HVC are convincingly associated to the emission of jets, but the origin of the LVC is still unknown. In this paper we analyze the forbidden line spectrum of a sample of 44 mostly lowmass young stars in Lupus and σ Ori observed with the X-shooter ESO spectrometer. We detect forbidden line emission of O , O , S , N , and N , and characterize the line profiles as LVC, blueshifted HVC, and redshifted HVC. We focus our study on the LVC.We show that there is a good correlation between line luminosity and both L star and the accretion luminosity (or the mass accretion rate) over a large interval of values (L star ∼ 10 −2 −1 L ; L acc ∼ 10 −5 −10 −1 L ;Ṁ acc ∼ 10 −11 −10 −7 M /yr). The lines show the presence of a slow wind (V peak < 20 km s −1 ) that is dense (n H > 10 8 cm −3 ), warm (T ∼ 5000−10 000 K), mostly neutral. We estimate the mass of the emitting gas and provide a value for the maximum volume it occupies. Both quantities increase steeply with the stellar mass, from ∼10 −12 M and ∼0.01 AU 3 for M star ∼ 0.1 M , to ∼3 × 10 −10 M and ∼1 AU 3 for M star ∼ 1 M , respectively. These results provide quite stringent constraints to wind models in low-mass young stars, that need to be explored further.

show abstract

Section: Wind Modelsmentioning

confidence: 99%

X-shooter spectroscopy of young stellar objects

Natta

Testi

Alcalá

et al. 2014

A&A

126

View full text Add to dashboard Cite

show abstract

“…This review does not deal with jet-launching processes nor with the general properties of jets and their relation to accretion disks. These topics are reviewed and studied in many other papers where more references can be found (e.g., Mirabel & Rodríguez 1999;Fender & Belloni 2004;Ferreira et al 2006;Livio 2011;Fender & Belloni 2012;Pudritz et al 2012;McKinney et al 2013;Zanni & Ferreira 2013;Frank et al 2014;Lasota et al 2014;Lovelace et al 2014;McKinney et al 2014). I assume that whenever the accreted gas has a large enough specific angular momentum jets are launched.…”

Section: Introductionmentioning

confidence: 99%

The jet feedback mechanism (JFM) in stars, galaxies and clusters

Soker

2016

New Astronomy Reviews

149

106

View full text Add to dashboard Cite

I review the influence jets and the bubbles they inflate might have on their ambient gas as they operate through a negative jet feedback mechanism (JFM). I discuss astrophysical systems where jets are observed to influence the ambient gas, in many cases by inflating large, hot, and low-density bubbles, and systems where the operation of the JFM is still a theoretical suggestion. The first group includes cooling flows in galaxies and clusters of galaxies, star-forming galaxies, young stellar objects, and bipolar planetary nebulae. The second group includes core collapse supernovae, the common envelope evolution, the grazing envelope evolution, and intermediate luminosity optical transients. The suggestion that the JFM operates in these four types of systems is based on the assumption that jets are much more common than what is inferred from objects where they are directly observed. Common to all eight types of systems reviewed here is the presence of a compact object inside an extended ambient gas. The ambient gas serves as a potential reservoir of mass to be accreted on to the compact object. If the compact object launches jets as it accretes mass, the jets might reduce the accretion rate as they deposit energy to the ambient gas, or even remove the entire ambient gas, hence closing a negative feedback cycle.

show abstract

“…Gallet & Bouvier 2013). External processes are responsible for the AM loss from the stellar surface, and models for such processes include the magnetic star-disk interaction (e.g., Ghosh & Lamb 1979;Matt & Pudritz 2005), accretion-powered stellar winds (e.g., Matt et al 2012), and mass ejections (e.g., Conical Winds: Zanni & Ferreira 2013;Romanova et al 2009). To constrain the physical models, recent studies have been looking for correlations between stellar rotation rates and parameters like stellar mass, circumstellar disk indicators, X-ray emission, and mass accretion rates.…”

Section: Introductionmentioning

confidence: 99%

Near-infrared time-series photometry in the field of Cygnus OB2 association

Roquette

Bouvier

Alencar

et al. 2017

A&A

View full text Add to dashboard Cite

Context. In the last decades, the early pre main sequence stellar rotational evolution picture has been constrained by studies targetting different regions at a variety of ages with respect to young star formation. Observational studies suggest a dependence of rotation with mass, and for some mass ranges a connection between rotation and the presence of a circumstellar disk. Not still fully explored, though, is the role of environmental conditions on the rotational regulation.Aims. We investigate the rotational properties of candidate members of the young massive association Cygnus OB2. By evaluating their rotational properties, we address questions regarding the effect of environment properties on PMS rotational evolution.Methods. We studied JHK-band variability in 5083 candidate members (24% of them are diskbearing stars). The selection of variable stars was done using Stetson variability index, and period search was performed using Lomb-Scargle periodogram for periods between 0.83-45 days. Period detections were verified by using False Alarme Probability levels, the Saunders statistics, string/rope length method, and visual verification of folded light curves.Results. We identified 1224 periodic variable stars (24% of the candidate member sample, 8% of the disk-bearing sample, and 28% of the non-disked sample). Monte Carlo simulations were performed in order to evaluate completeness and contamination of the periodic sample, out of which 894 measured periods were considered reliable. Our study was considered reasonably complete for periods between 2 and 30 days. Conclusions. The general scenario for the rotational evolution of young stars seen in other regions is confirmed by Cygnus OB2 period distributions, with disked stars rotating on average slower than non-disked stars. A mass-rotation dependence was also verified, but as in NGC 6530, very low mass stars (M ≤ 0.4M ) are rotating on average slower than higher mass stars (0.4 M < M ≤ 1.4M ). We observed an excess of slow rotators among the lower mass population. The disk and mass-rotation connection was also analysed by taking into account the incident UV radiation arising from O stars in the association. Results compatible with the disk-locking scenario were verified for stars with low UV incidence, but no statistical significant relation between rotation and disk presence was verified for stars with high UV incidence suggesting that massive stars can have an important role on regulating the rotation of nearby low mass stars.Key words. infrared: stars -stars: variables: T Tauri -stars: low-mass -stars: formation -stars: pre main sequence -stars: rotation Use \titlerunning to supply a shorter title and/or \authorrunning to supply a shorter list of authors.

show abstract

MHD simulations of accretion onto a dipolar magnetosphere

Cited by 212 publications

References 65 publications

X-shooter spectroscopy of young stellar objects

X-shooter spectroscopy of young stellar objects

The jet feedback mechanism (JFM) in stars, galaxies and clusters

Near-infrared time-series photometry in the field of Cygnus OB2 association

Contact Info

Product

Resources

About