X-shooter spectroscopy of young stellar objects

Natta, A.; Testi, L.; Alcalá, J. M.; Rigliaco, E.; Covino, E.; Stelzer, B.; D’Elia, V.

doi:10.1051/0004-6361/201424136

Cited by 94 publications

(139 citation statements)

References 58 publications

Supporting

Mentioning

128

Contrasting

Order By: Relevance

“…From the diagnostic analysis it results that the LVC shares the same electron density and extinction as the base of the HVC, but has a lower temperature, on the order of ∼7000 K. Forbidden line emission components centered close to systemic velocity are features commonly observed in CTT stars (e.g., Hartigan et al 1995;Natta et al 2014). The typical peak velocities of CTT LVCs are in the range ∼5−20 km s −1 (thus closer to systemic velocity than the HH34 LVC) and they are usually brighter than the corresponding HVC emission, even in sources known to drive prominent jets (e.g., Hartigan et al 1995).…”

Section: Origin Of the Lvcmentioning

confidence: 95%

The small-scale HH34 IRS jet as seen by X-shooter

Nisini¹,

Giannini²,

Antoniucci³

et al. 2016

A&A

Self Cite

View full text Add to dashboard Cite

Context. Atomic jets are a common phenomenon among young stars, being intimately related to disk accretion. Most studies have been performed on jets from pre-main sequence stars. However, to date very little detailed information has been gathered on jets from young embedded low mass sources (the so-called class I stars), especially in the inner jet region. Aims. We exploit a diagnostic analysis based on multiwave spectroscopic observations to infer kinematics and physical conditions of the inner region of the prototypical class I jet from HH34 IRS. Methods. We use a deep X-shooter spectrum covering the wavelength range 350−2300 nm at resolution between ∼8000 and ∼18 000 (i.e., ∆V ∼ 17−27 km s −1 ), which allows us to detect lines in a wide range of excitation conditions (from E up ∼ 8000 to ∼31 000 cm −1 ) and to study their kinematics. Statistical equilibrium and ionization models are adopted to derive the jet main physical parameters. Results. We separately derive the physical conditions for the extended high velocity jet (HVC, V r ∼ −100 km s −1 ) and for the low velocity and compact gas (LVC, V r ∼ −20−50 km s −1 ) located on-source. Close to the jet base (<200 AU from source) the HVC gas is mostly neutral (x e < 0.1) and very dense (n H > 5 × 10 5 cm −3 ). The LVC gas has the same density and A V as the HVC, but it is at least a factor of two colder. Iron abundance in the HVC is consistent with the solar value, while it is a factor of 3 subsolar in the LVC, suggesting an origin of the LVC gas from a dusty disk. From the derived total density we infer that the jet mass flux rate is >5 × 10 −7 M yr −1 . We find that the relationships between accretion luminosity and permitted line luminosity derived for T Tauri stars cannot be directly extended to class I sources embedded in reflection nebulae since the permitted lines are seen through scattered light. An accretion rate of ∼7 × 10 −6 M yr −1 is instead derived from an empirical relationship connectingṀ acc with L([O i])(HVC).Conclusions. The class I HH34 IRS jet at small scale shares many kinematical and physical properties with the jets from the most active classical T Tauri (CTT) stars. However, the HH34 IRS jet is denser as a consequence of the larger mass ejection rate with respect to typical values in CTTs jets. These findings suggests that the acceleration and excitation mechanisms in collimated jets are not influenced by evolution and are similar in CTTs and in still embedded sources with high accretion rates.

show abstract

Section: Origin Of the Lvcmentioning

confidence: 95%

The small-scale HH34 IRS jet as seen by X-shooter

Nisini¹,

Giannini²,

Antoniucci³

et al. 2016

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…This is a particularly interesting relation as it is obtained independently from models of PMS evolution, thus it can be considered a "purely observational" plot. The plot also indicates the best-fit relation for the GTO sample by Natta et al (2014), in which the slope is 1.53 ± 0.18.…”

Section: Accretion Luminosity and Stellar Luminosity Relationmentioning

confidence: 99%

“…Star-disk interaction processes can be studied observationally through the strong signatures they introduce in the spectra of YSOs. Accretion shocks give rise to continuum excess emission in the UV (e.g., Valenti et al 1993;Gullbring et al 1998Gullbring et al , 2000Calvet et al 2000) and the prominent emission of permitted lines across the whole spectrum (e.g., Muzerolle et al 1998aMuzerolle et al ,b,c, 2003Natta et al 2004), while winds are traced by various forbidden emission lines (e.g., Hartigan et al 1995;Rigliaco et al 2013;Natta et al 2014). In recent years, new instruments have provided the possibility of studying these processes simultaneously in large samples of objects.…”

Section: Introductionmentioning

confidence: 99%

X-Shooter study of accretion inρ-Ophiucus: very low-mass stars and brown dwarfs

Manara

Testi

Natta

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

We present new VLT/X-Shooter optical and near-infrared spectra of a sample of 17 candidate young low-mass stars and brown dwarfs located in the ρ-Ophiucus cluster. We derived the spectral type and extinction for all the targets, and then we determined their physical parameters. All the objects but one have M 0.6 M , and eight have mass below or close to the hydrogen-burning limit. Using the intensity of various permitted emission lines present in their spectra, we determined the accretion luminosity and mass accretion rates (Ṁ acc ) for all the objects. When compared with previous works targeting the same sample, we find that, in general, these objects are not as strongly accreting as previously reported, and we suggest that the reason is our more accurate estimate of the photospheric parameters. We also compare our findings with recent works in other slightly older star-forming regions, such as Lupus, to investigate possible differences in the accretion properties, but we find that the accretion properties for our targets have the same dependence on the stellar and substellar parameters as in the other regions. This leads us to conclude that we do not find evidence for a different dependence ofṀ acc with M when comparing low-mass stars and brown dwarfs. Moreover, we find a similar small ( 1 dex) scatter in theṀ acc −M relation as in some of our recent works in other star-forming regions, and no significant differences inṀ acc due to different ages or properties of the regions. The latter result suffers, however, from low statistics and sample selection biases in the current studies. The small scatter in theṀ acc −M correlation confirms that mass accretion rate measurements in the literature based on uncertain photospheric parameters and single accretion indicators, such as the Hα width, can lead to a scatter that is unphysically large. Our studies show that only broadband spectroscopic surveys coupled with a detailed analysis of the photospheric and accretion properties allows us to properly study the evolution of disk accretion rates in star-forming regions.Key words. stars: pre-main sequence -stars: formation -brown dwarfs -protoplanetary disks -accretion, accretion disksopen clusters and associations: individual: rho-Ophiucus IntroductionThe evolution of protoplanetary disks surrounding forming stars has been a major subject of study in recent years. The interest in this topic is driven by the fact that disks are the birthplace of planets. A clear understanding of the physical mechanisms driving the formation, evolution, and dispersal of disks is thus needed to constrain planet formation theories, and to explain the observed properties of our own solar system and of the wealth of exoplanetary systems discovered so far.During their evolution, the central young stellar object (YSO) and the surrounding disk interact through multiple processes, such as photoevaporation, stellar winds, and accretion of matter. The latter is a result of viscous processes happening in the disk, which drive its secular evolu...

show abstract

“…The Taurus targets analyzed here follow the L acc -L distribution of the Lupus targets, while the Chamaeleon II targets are located in the lower part of the distribution. With respect to the best fit of the sample of Alcalá et al (2014) (shown in the figure as a black dotted line, from Natta et al 2014), the Chamaeleon I targets follow a steeper slope of L acc vs. L . However, the two values are compatible.…”

Section: Accretion Luminosity and Stellar Luminosity Dependencementioning

confidence: 99%

X-Shooter study of accretion in Chamaeleon I

Manara

Fedele

Herczeg

et al. 2016

A&A

125

163

View full text Add to dashboard Cite

We present the analysis of 34 new VLT/X-Shooter spectra of young stellar objects in the Chamaeleon I star-forming region, together with four more spectra of stars in Taurus and two in Chamaeleon II. The broad wavelength coverage and accurate flux calibration of our spectra allow us to estimate stellar and accretion parameters for our targets by fitting the photospheric and accretion continuum emission from the Balmer continuum down to ∼700 nm. The dependence of accretion on stellar properties for this sample is consistent with previous results from the literature. The accretion rates for transitional disks are consistent with those of full disks in the same region. The spread of mass accretion rates at any given stellar mass is found to be smaller than in many studies, but is larger than that derived in the Lupus clouds using similar data and techniques. Differences in the stellar mass range and in the environmental conditions between our sample and that of Lupus may account for the discrepancy in scatter between Chamaeleon I and Lupus. Complete samples in Chamaeleon I and Lupus are needed to determine whether the difference in scatter of accretion rates and the lack of evolutionary trends are not influenced by sample selection.

show abstract

X-shooter spectroscopy of young stellar objects

Cited by 94 publications

References 58 publications

The small-scale HH34 IRS jet as seen by X-shooter

The small-scale HH34 IRS jet as seen by X-shooter

X-Shooter study of accretion inρ-Ophiucus: very low-mass stars and brown dwarfs

X-Shooter study of accretion in Chamaeleon I

Contact Info

Product

Resources

About