X-shooter spectroscopy of FU Tauri A

Stelzer, B.; Alcalá, J. M.; Scholz, Alexander; Natta, A.; Randich, S.; Covino, E.

doi:10.1051/0004-6361/201220736

Cited by 16 publications

(31 citation statements)

References 65 publications

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“…Manara et al (2013b) have developed a new method to model all the components of the observed X-Shooter spectra of YSOs to directly derive L acc simultaneously with the stellar parameters and extinction. First studies of accretion with this instrument focused on individual targets (e.g., Rigliaco et al 2011b;Stelzer et al 2013) or on a few very low-mass stars and BDs in σ-Orionis (Rigliaco et al 2012). The largest sample studied to date with this instrument is a set of 36 YSOs in the Lupus I and III clouds .…”

Section: Introductionmentioning

confidence: 99%

X-Shooter study of accretion in Chamaeleon I

Manara

Fedele

Herczeg

et al. 2016

A&A

126

163

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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.

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Section: Introductionmentioning

confidence: 99%

X-Shooter study of accretion in Chamaeleon I

Manara

Fedele

Herczeg

et al. 2016

A&A

126

163

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“…This sample included objects with spectral type from K5 to M9.5 with typically two or more objects per spectral subclass. The spectra, fully reduced and calibrated, were made available to the community and have already been used as templates for several studies (e.g., Alcalá et al 2014Alcalá et al , 2017Banzatti et al 2014;Fang et al 2016;Manara et al 2015Manara et al , 2016Manara et al , 2017Manjavacas et al 2014;Stelzer et al 2013b;Whelan et al 2014). From the same spectra we estimated the contribution of chromospheric activity to the emission lines typically used to estimate the accretion luminosity of accreting stars, showing that this has a strong dependence on the spectral type, and hence the stellar mass, of the target.…”

Section: Introductionmentioning

confidence: 99%

An extensive VLT/X-shooter library of photospheric templates of pre-main sequence stars

Manara

Frasca

Alcalá

et al. 2017

A&A

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Context. Studies of the formation and evolution of young stars and their disks rely on knowledge of the stellar parameters of the young stars. The derivation of these parameters is commonly based on comparison with photospheric template spectra. Furthermore, chromospheric emission in young active stars impacts the measurement of mass accretion rates, a key quantity for studying disk evolution. Aims. Here we derive stellar properties of low-mass (M 2 M ) pre-main sequence stars without disks, which represent ideal photospheric templates for studies of young stars. We also use these spectra to constrain the impact of chromospheric emission on the measurements of mass accretion rates. The spectra are reduced, flux-calibrated, and corrected for telluric absorption, and are made available to the community. Methods. We derive the spectral type for our targets by analyzing the photospheric molecular features present in their VLT/X-shooter spectra by means of spectral indices and comparison of the relative strength of photospheric absorption features. We also measure effective temperature, gravity, projected rotational velocity, and radial velocity from our spectra by fitting them with synthetic spectra with the ROTFIT tool. The targets have negligible extinction (A V < 0.5 mag) and spectral type from G5 to K6, and from M6.5 to M8. They thus complement the library of photospheric templates presented in our previous publication. We perform synthetic photometry on the spectra to derive the typical colors of young stars in different filters. We measure the luminosity of the emission lines present in the spectra and estimate the noise due to chromospheric emission in the measurements of accretion luminosity in accreting stars. Results. We provide a calibration of the photospheric colors of young pre-main sequence stars as a function of their spectral type in a set of standard broad-band optical and near-infrared filters. The logarithm of the noise on the accretion luminosity normalized to the stellar luminosity is roughly constant and equal to ∼−2.3 for targets with masses larger than 1 solar mass, and decreases with decreasing temperatures for lower-mass stars. For stars with masses of ∼1.5 M and ages of ∼1−5 Myr, the chromospheric noise converts to a limit of measurable mass accretion rates of ∼3 × 10 −10 M /yr. The limit on the mass accretion rate set by the chromospheric noise is of the order of the lowest measured values of mass accretion rates in Class II objects.

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“…A key way to do this is to investigate their accretion and outflow properties and compare them to YSOs. Since evidence first emerged that BDs launch outflows (Fernández & Comerón 2001;Whelan et al 2005) the number of BD outflows, both atomic and molecular has grown to ∼10 (Phan-Bao et al 2008;Whelan et al 2012;Joergens et al 2012;Stelzer et al 2013;Monin et al 2013). While this is still a statistically small sample, the comparison between BD outflows and those driven by Class II YSOs i.e classical T Tauri stars (CTTSs) has proven to be very interesting (Whelan et al 2009b(Whelan et al , 2011.…”

Section: Introductionmentioning

confidence: 99%

“…4.2). This work is part of a larger study to investigate the accretion-ejection connection in BDs and very low mass stars (VLMSs; Whelan et al 2014a;Giannini et al 2013;Stelzer et al 2013). …”

Section: Introductionmentioning

confidence: 99%

Accretion-ejection connection in the young brown dwarf candidate ISO-ChaI 217

Whelan

Alcalá

Bacciotti

et al. 2014

A&A

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As the number of observed brown dwarf outflows is growing it is important to investigate how these outflows compare to the wellstudied jets from young stellar objects. A key point of comparison is the relationship between outflow and accretion activity and in particular the ratio between the mass outflow and accretion rates (Ṁ out /Ṁ acc ). The brown dwarf candidate ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric study of brown dwarfs, to be driving an asymmetric outflow with the blueshifted lobe having a position angle of ∼20 • . The aim here is to further investigate the properties of ISO-ChaI 217, the morphology and kinematics of its outflow, and to better constrainṀ out /Ṁ acc . The outflow is spatially resolved in the [S ] λλ6716, 6731 lines and is detected out to ∼1. 6 in the blue-shifted lobe and 1 in the red-shifted lobe. The asymmetry between the two lobes is confirmed although the velocity asymmetry is less pronounced with respect to our previous study. Using thirteen different accretion tracers we measure log (Ṁ acc ) [M /yr] = −10.6 ± 0.4. As it was not possible to measure the effect of extinction on the ISO-ChaI 217 outflowṀ out was derived for a range of values of A v , up to a value of A v = 2.5 mag estimated for the source extinction. The logarithm of the mass outflow (Ṁ out ) was estimated in the range −11.7 to −11.1 for both jets combined. ThusṀ out /Ṁ acc [M /yr] lies below the maximum value predicted by magneto-centrifugal jet launching models. Finally, both model fitting of the Balmer decrements and spectro-astrometric analysis of the Hα line show that the bulk of the H I emission comes from the accretion flow.

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X-shooter spectroscopy of FU Tauri A

Cited by 16 publications

References 65 publications

X-Shooter study of accretion in Chamaeleon I

X-Shooter study of accretion in Chamaeleon I

An extensive VLT/X-shooter library of photospheric templates of pre-main sequence stars

Accretion-ejection connection in the young brown dwarf candidate ISO-ChaI 217

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