Accretion in brown dwarfs: An infrared view

Natta, A.; Testi, L.; Muzerolle, James; Randich, S.; Comerón, F.; Persi, P.

doi:10.1051/0004-6361:20040356

Cited by 403 publications

(750 citation statements)

References 32 publications

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“…Most of the targets analyzed here have been previously observed in NIR spectroscopic or photometric studies (e.g., Wilking et al 1999;Luhman & Rieke 1999;Natta et al 2002Natta et al , 2004Natta et al , 2006 or with optical spectroscopy (e.g., Wilking et al 2005). The stellar parameters (SpT, A V ) derived in these works for our targets are reported in Table A.1 and in Table D.1 for N06.…”

Section: Comparison With Previous Resultsmentioning

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%

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

Manara

Testi

Natta

et al. 2015

A&A

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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...

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Section: Comparison With Previous Resultsmentioning

confidence: 99%

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

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“…For what concerns L1415-IRS, this condition seems to be met since it is still embedded and surrounded by a halo of matter. Recent studies show that the disks of brown dwarfs are quite similar to those of low-and intermediatemass stars (e.g., Natta et al 2004;Apai et al 2005). The observation of an FUor-type event from a low-luminosity YSO adds another piece of evidence to this finding.…”

Section: Fuor-or Exor-like Activity Of L1415-irsmentioning

confidence: 87%

The new nebula in LDN 1415 – A cry from the cradle of a low-luminosity source

Stecklum¹,

Melnikov

Meusinger³

2006

A&A

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Aims.A survey for candidate Herbig-Haro objects was performed to search for evidence of star formation in Galactic dark clouds Methods. For this aim true colour images were created from blue, red, and infrared DSS2 plates and inspected. Follow-up I-band, Hα, and [S ii] CCD imaging as well as long-slit spectroscopy using the Tautenburg 2-m telescope was carried out to verify candidate objects.Results. In the case of LDN 1415, the presence of a Herbig-Haro flow could be revealed which is henceforth named HH 892. In addition, an arcuate nebula was found which is barely seen on the DSS2 infrared plate (epoch 1996) and not detected in archival Kiso Schmidt data (epoch 2001). Thus, this nebula must have brightened by about 3.8 mag in recent years. Conclusions. The nebula is associated with IRAS 04376+5413. The 2MASS images show a red counterpart of the IRAS source, designated as L1415-IRS. Its morphology resembles that of a bipolar young object. The luminosity of this source integrated from 0.9 µm to 60 µm in the low state amounts to 0.13 L for an assumed distance of 170 pc. Thus it seems to be a young very-low mass star or it might even be of substellar mass. The current brightness increase of the nebula is caused by a FUor-or EXor-like outburst as indicated by the presence of a P Cygni profile of the Hα line. L1415-IRS is by far the least luminous member of the sparse sample of FUor and EXor objects.

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“…A later survey of the σ Orionis cluster found a large spread in measured values of Li pEW (Kenyon et al 2005), indicating a spread of ages. The authors did not reach any conclusions as to the cause of this spread in Li pEW, but noted that similar spreads in Li pEW have been observed among low mass objects in the Chamaeleon I cluster (Joergens & Guenther 2001;Natta et al 2004). A study of the luminosity spread in the HRD of the ONC argued that there was little evidence to support age spreads greater than a few Myr (Jeffries et al 2011).…”

Section: Age Spreadsmentioning

confidence: 94%

Towards precise ages and masses of Free Floating Planetary Mass Brown Dwarfs

Canty¹,

Lucas²,

Roche³

et al. 2013

Monthly Notices of the Royal Astronomical Society

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Measurement of the substellar initial mass function (IMF) in very young clusters is hampered by the possibility of the age spread of cluster members. This is particularly serious for candidate planetary mass objects (PMOs), which have a very similar location to older and more massive brown dwarfs on the Hertzsprung-Russell Diagram (HRD). This degeneracy can be lifted by the measurement of gravity sensitive spectral features. To this end we have obtained medium resolution (R≈5000) Near-infrared Integral Field Spectrometer (NIFS) K band spectra of a sample of late M-/early L-type dwarfs. The sample comprises old field dwarfs and very young brown dwarfs in the Taurus association and in the σ Orionis cluster. We demonstrate a positive correlation between the strengths of the 2.21 µm NaI doublet and the objects' ages. We demonstrate a further correlation between these objects' ages and the shape of their K band spectra. We have quantified this correlation in the form of a new index, the H 2 (K) index. This index appears to be more gravity-sensitive than the NaI doublet and has the advantage that it can be computed for spectra where gravity-sensitive spectral lines are unresolved, while it is also more sensitive to surface gravity at very young ages (<10 Myr) than the triangular H band peak. Both correlations differentiate young objects from field dwarfs, while the H 2 (K) index can distinguish, at least statistically, populations of ∼1 Myr objects from populations of ∼10 Myr objects. We applied the H 2 (K) index to NIFS data for one Orion nebula cluster (ONC) PMO and to previously published low resolution spectra for several other ONC PMOs where the 2.21 µm NaI doublet was unresolved and concluded that the average age of the PMOs is ∼1 Myr.

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Accretion in brown dwarfs: An infrared view

Cited by 403 publications

References 32 publications

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

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

The new nebula in LDN 1415 – A cry from the cradle of a low-luminosity source

Towards precise ages and masses of Free Floating Planetary Mass Brown Dwarfs

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