T Tauri stars in blue

Valenti, Jeff A.; Basri, Gibor; Johns, Christopher

doi:10.1086/116783

Cited by 254 publications

(299 citation statements)

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“…In any case, great uncertainties remain in the derived accretion rates (especially when the hot accretion continuum is very high) mainly due to uncertainties in the extinction corrections. The three most extensive samples of T Tauri stars with accretion rates determined in this way (Valenti et al 1993;Hartigan et al 1995;Gullbring et al 1998) report values that differ for the same star by as much as a factor of ten. On the average, the Gullbring et al (1998) and the Valenti et al (1993) estimates are consistent with each other, although with large scatter, while the Hartigan et al (1995) estimates are systematically biased to higher values.…”

Section: Discussionmentioning

confidence: 99%

The spectral energy distribution of self-gravitating protostellar disks

Lodato

Bertin

2001

A&A

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Abstract. The long wavelength emission of protostellar objects is commonly attributed to a disk of gas and dust around the central protostar. In the first stages of disk accretion or in the case of high mass protostars, the disk mass is likely to be sufficiently large, so that the disk self-gravity may have an impact on the dynamics and the emission properties of the disk. In this paper we describe the spectral energy distribution (SED) produced by a simple, non-flaring, self-gravitating accretion disk model. Self-gravity is included in the calculation of the rotation curve of the disk and in the energy balance equation, as a term of effective heating related to Jeans instability. In order to quantify in detail the requirements on the mass of the disk and on the accretion rate posed on the models by realistic situations, we compare the SEDs produced by these models with the observed SEDs of a small sample of well-studied protostellar objects. We find that relatively modest disks -even lighter than the central star -can lead to an interesting fit to the infrared SED of the FU Orionis objects considered, while in the case of T Tauri stars the required parameters fall outside the range suggested as acceptable by the general theoretical and observational scenario. On the basis of the present results, we may conclude that the contribution of a selfgravitating disk is plausible in several cases (in particular, for FU Orionis objects) and that, in the standard irradiation, dominated disk scenario, it would help soften the requirements encountered by Keplerian accretion models.

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Section: Discussionmentioning

confidence: 99%

The spectral energy distribution of self-gravitating protostellar disks

Lodato

Bertin

2001

A&A

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“…The SEDs of this object have been used by Corbally et al (2009) for comparison with SEDs in their sample stars. Valenti et al (1993) provide blue LkHα 191 spectra. Terranegra et al (1994) classify it as CTTS star and present uvbyβ photometry.…”

Section: Lkhα 191mentioning

confidence: 99%

Long-term photometric observations of pre-main sequence objects in the field of North America/Pelican Nebula

Beljan

Jurdana-Šepić

Semkov

et al. 2014

A&A

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To broaden the search and study stars in the early evolutionary phase, we investigated a sample of 17 pre-main sequence objects previously detected as either Hα emission-line pre-main sequence stars or T Tauri variables located in the field of the North America/Pelican Nebula complex. Johnson-Cousins B, V, R c , I c magnitudes and mean color indices for the program stars are determined from more than 12 400 measurements from archive photographic plates and from CCD data collected at 7 observatories covering the period of almost 60 years from 1954 up to 2013. We complemented previously rare insights on the photometry of the program stars and presented their photometric history, which for almost all program stars is the first long term photometric monitoring on a timescale of 6 decades. Eight program stars are found to be classical T Tauri stars of variability type II, while 6 program stars are weak-line T Tauri stars of variability type I. For the first time, periodicity is found for three stars: V1716 Cyg indicates a 4.15 day period, V2051 Cyg indicates a 384 day period, and V521 Cyg a period of 503 days.

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“…Measurements of L acc require well-calibrated observations of the continuum flux over a wide range of wavelengths, as well as an adequate knowledge of the photospheric and chromospheric spectrum of the star, which need to be subtracted from the observed flux to isolate the accretion emission. This has been possible for a relatively small sample of objects only (Hartigan et al 1995(Hartigan et al , 1991Muzerolle et al 2003;Valenti et al 1993;Gullbring et al 1998;Herczeg & Hillenbrand 2008, hereafter HH08). However, it has been noticed that in these objects the luminosity or flux of several lines correlates quite well with L acc .…”

Section: Introductionmentioning

confidence: 99%

X-shooter spectroscopy of young stellar objects

Rigliaco

Natta

Testi

et al. 2012

A&A

180

291

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We present high-quality, medium-resolution X-shooter/VLT spectra in the range 300−2500 nm for a sample of 12 very low mass stars in the σ Orionis cluster. The sample includes eight stars with evidence of disks from Spitzer and four without disks, with masses ranging from 0.08 to 0.3 M . The aim of this first paper is to investigate the reliability of the many accretion tracers currently used to measure the mass accretion rate in low-mass young stars and the accuracy of the correlations between these secondary tracers (mainly accretion line luminosities) found in the literature. We use our spectra to measure the accretion luminosity from the continuum excess emission in the UV and visual; the derived mass accretion rates range from 10 −9 M yr −1 down to 5 × 10 −11 M yr −1 , allowing us to investigate the behavior of the accretion-driven emission lines in very low mass accretion rate regimes. We compute the luminosity of ten accretion-driven emission lines from the UV to the near-IR, which are all obtained simultaneously. In general, most of the secondary tracers correlate well with the accretion luminosity derived from the continuum excess emission. We recompute the relationships between the accretion luminosities and the line luminosities, and we confirm the validity of the correlations given in the literature, with the possible exception of Hα. Metallic lines, such as the CaII IR triplet or the Na I line at 589.3 nm, show a larger dispersion. When looking at individual objects, we find that the hydrogen recombination lines, from the UV to the near-IR, give good and consistent measurements of L acc that often better agree than the uncertainties introduced by the adopted correlations. The average L acc derived from several hydrogen lines, measured simultaneously, have a much reduced error. This suggests that some of the spread in the literature correlations may be due to the use of nonsimultaneous observations of lines and continuum. Three stars in our sample deviate from this behavior, and we discuss them individually.

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T Tauri stars in blue

Cited by 254 publications

References 0 publications

The spectral energy distribution of self-gravitating protostellar disks

The spectral energy distribution of self-gravitating protostellar disks

Long-term photometric observations of pre-main sequence objects in the field of North America/Pelican Nebula

X-shooter spectroscopy of young stellar objects

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