J/A+A/548/A56 X-shooter spectra of 12 young stellar objects (Rigliaco+, 2012)
X-shooter spectroscopy of young stellar objects.
I. Mass accretion rates of low-mass T Tauri stars in σ Orionis.
Rigliaco E., Natta A., Testi L., Randich S., Alcala J.M., Covino E.,
Stelzer B.
<Astron. Astrophys., 548, A56-56 (2012)>
=2012A&A...548A..56R 2012A&A...548A..56R
ADC_Keywords: Stars, pre-main sequence ; Spectroscopy ; Equivalent widths ; YSOs
Keywords: stars: low-mass - accretion, accretion disks - line: formation -
open clusters and associations: individual: sigma Orionis
Abstract:
We present high-quality, medium-resolution X-shooter/VLT spectra in
the range 300-2500nm 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 0.3M☉. 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
10-9M☉/yr down to 5x10-11M☉/yr, 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 NaI line at 589.3nm, 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 Lacc that often better agree than the uncertainties
introduced by the adopted correlations. The average Lacc 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.
Description:
X-shooter@VLT spectra of 12 Young Stellar Objects (YSOs) in the
σ Orionis star forming region were acquired on 21, 23 and 24
December 2009 and 11-12 January 2011. For most of the targets, slits
of 1"/0.9" were used in the UVB/VIS arms, respectively, yielding
resolving powers of 5100/8800.
For every YSO the spectra in the UVB and VIS are given. The 1d
wavelength-calibrated and flux-calibrated spectra are in fits format
and are not corrected for extinction.
The wavelength units are nm and the flux units are erg/s/cm2/nm.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 41 12 Stellar parameters and observed properties
table4.dat 129 8 Hydrogen recombination line equivalent widths
and fluxes
table5.dat 99 8 Fluxes and equivalent widths of other lines
used as accretion indicators
list.dat 57 12 X-shooter spectra of Sigma Orionis YSOs
sp/* . 24 Individual FITS spectra
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See also:
J/A+A/551/A107 : X-shooter spectra of 24 young stellar objects (Manara+, 2013)
J/A+A/561/A2 : 36 accreting YSOs emission lines (Alcala+, 2014)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Name Object name
8- 11 A4 --- SpT MK spectral type
13- 16 I4 K Teff Effective temperature
18- 21 F4.2 Lsun Lum Luminosity
23- 26 F4.2 Rsun Rad Radius
28- 31 F4.2 Msun Mass Mass
33- 35 A3 --- Cl [II /III] YSO class
37- 41 F5.2 mag Imag I-band magnitude
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Name Object name
8- 15 E8.3 mW/m2 F(Ha) Hα flux (erg/cm2/s)
17- 24 E8.3 mW/m2 F(Hb) Hβ flux (erg/cm2/s)
26- 33 E8.3 mW/m2 F(Hg) Hγ flux (erg/cm2/s)
35- 42 E8.3 mW/m2 F(H11) H11 flux (erg/cm2/s)
44- 51 E8.3 mW/m2 F(Pag) ?=- Paschenγ flux (erg/cm2/s)
53- 60 E8.3 mW/m2 F(Pab) ?=- Paschenβ flux (erg/cm2/s)
62- 67 F6.2 nm W(Ha) Hα equivalent width
69- 72 F4.2 nm e_W(Ha) rms uncertainty on W(Ha)
74- 78 F5.2 nm W(Hb) Hβ equivalent width
80- 83 F4.2 nm e_W(Hb) rms uncertainty on W(Hb)
85- 89 F5.2 nm W(Hg) Hγ equivalent width
91- 94 F4.2 nm e_W(Hg) rms uncertainty on W(Hg)
96-100 F5.2 nm W(H11) H11 equivalent width
102-105 F4.2 nm e_W(H11) rms uncertainty on W(H11)
107-112 F6.3 nm W(Pag) ?=- Paschenγ equivalent width
114-117 F4.2 nm e_W(Pag) ? rms uncertainty on W(Pag)
119-124 F6.3 nm W(Pad) ?=- Paschenδ equivalent width
126-129 F4.2 nm e_W(Pad) ? rms uncertainty on W(Pad)
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name Object name
8- 16 E9.4 mW/m2 F(HeI) HeI (587.6) flux (erg/cm2/s)
18 A1 --- l_F(NaI) Limit flag on FNaI
19- 26 E8.3 mW/m2 F(NaI) NaI (589.3) flux (erg/cm2/s)
28 A1 --- l_F(CaT1) Limit flag on CaT1
29- 37 E9.4 mW/m2 F(CaT1) CaII (854.2) flux (erg/cm2/s)
39 A1 --- l_F(CaT2) Limit flag on CaT2
40- 48 E9.4 mW/m2 F(CaT2) CaII (866.2) flux (erg/cm2/s)
50- 55 F6.3 nm W(HeI) HeI (587.6) equivalent width
57- 60 F4.2 nm e_W(HeI) rms uncertainty on W(HeI)
62 A1 --- l_W(NaI) Limit flag on W(NaI)
63- 68 F6.3 nm W(NaI) NaI (589.3) equivalent width
70- 73 F4.2 nm e_W(NaI) ? rms uncertainty on W(NaI)
75 A1 --- l_W(CaT1) Limit flag on W(CaT1)
76- 81 F6.3 nm W(CaT1) CaII (854.2) equivalent width
83- 86 F4.2 nm e_W(CaT1) ? rms uncertainty on W(CaT1)
88 A1 --- l_W(CaT2) Limit flag on W(CaT2)
89- 94 F6.3 nm W(CaT2) CaII (866.2) equivalent width
96- 99 F4.2 nm e_W(CaT2) ? rms uncertainty on W(CaT2)
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name Object name
8- 9 I2 h RAh Right ascension (J2000)
11- 12 I2 min RAm Right ascension (J2000)
14- 18 F5.2 s RAs Right ascension (J2000)
20 A1 --- DE- Declination sign
21- 22 I2 deg DEd Declination (J2000)
24- 25 I2 arcmin DEm Declination (J2000)
27- 31 F5.2 arcsec DEs Declination (J2000)
33- 44 A12 --- UVB UVB Spectrum filename in subdirectory sp
(λ=310-589nm)
46- 57 A12 --- VIS VIS Spectrum filename in subdirectory sp
(λ=546-1019nm)
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Acknowledgements:
Elisabetta Rigliaco, rigliaco(at)lpl.arizona.edu
References:
Manara et al., Paper II 2013A&A...551A.107M 2013A&A...551A.107M, Cat. J/A+A/551/A107
Stelzer et al., Paper III 2013A&A...558A.141S 2013A&A...558A.141S
Alcala et al., Paper IV 2014A&A...561A...2A 2014A&A...561A...2A, Cat. J/A+A/561/A2
(End) E. Rigliaco [Univ. Arizona, Tucson, AZ], P. Vannier [CDS] 02-Jun-2014