J/A+A/605/A86 Pre-main sequence stars VLT/X-Shooter spectra (Manara+, 2017)
An extensive VLT/X-Shooter library of photospheric templates of pre-main
sequence stars.
Manara C.F., Frasca A., Alcala J.M., Natta A., Stelzer B., Testi L.
<Astron. Astrophys. 605, A86 (2017)>
=2017A&A...605A..86M 2017A&A...605A..86M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Stars, variable ; Spectroscopy
Keywords: stars: pre-main sequence - stars: chromospheres - stars: formation -
stars: low-mass - stars: variables: T Tauri, Herbig Ae/Be - catalogs
Abstract:
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.
Here we derive stellar properties of low-mass (M*~<2M☉) 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.
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 (AV<0.5mag)
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 paper. 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 1.5Msun
and ages of 1-5Myr, the chromospheric noise converts to a limit of
measurable mass accretion rates of 3x10-10M☉/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.
Description:
Reduced, flux- and wavelength-calibrated, telluric corrected 1-d
spectra of all the 17 objects considered in this work. Each object's
spectrum is divided in the three arms of X-Shooter, namely the UVB
arm, the VIS arm, and the NIR arm. The spectra are given in fits
format and are not corrected for extinction when the objects are known
to have low Av (<0.5 mag), while the spectrum of HBC407 is corrected
for Av=0.8mag using the reddening law by Cardelli et al.
(1989ApJ...345..245C 1989ApJ...345..245C) and Rv=3.1. The wavelengths are in nanometers
and the flux in erg/s/cm2/nm.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
spectra.dat 104 17 X-shooter spectra of Class III YSOs
sp/* . 51 Individual fits spectra
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Byte-by-byte Description of file: spectra.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- YSO Object name
22- 23 I2 h RAh Right ascension (J2000)
25- 26 I2 min RAm Right ascension (J2000)
28- 32 F5.2 s RAs Right ascension (J2000)
34 A1 --- DE- Declination sign (J2000)
35- 36 I2 deg DEd Declination (J2000)
38- 39 I2 arcmin DEm Declination (J2000)
41- 45 F5.2 arcsec DEs Declination (J2000)
47- 50 A4 --- SpType Spectral type of the object
53- 64 A12 --- UVB UVB spectrum filename in subdirectory sp
67- 78 A12 --- VIS VIS spectrum filename in subdirectory sp
81- 92 A12 --- NIR NIR spectrum filename in subdirectory sp
94- 96 F3.1 arcsec SLU Width of the UVB slit
98-100 F3.1 arcsec SLV Width of the VIS slit
102-104 F3.1 arcsec SLN Width of the NIR slit
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Acknowledgements:
Carlo Felice Manara, cmanara(at)cosmos.esa.int
(End) Carlo Felice Manara [ESA/ESTEC], Patricia Vannier [CDS] 06-Jul-2017