J/A+A/632/A32 Carbon depletion observed inside T Tauri inner rims (McClure 2019)
Carbon depletion observed inside T Tauri inner rims.
Formation of icy, kilometer size planetesimals by 1 Myr.
McClure M.K.
<Astron. Astrophys. 632, A32 (2019)>
=2019A&A...632A..32M 2019A&A...632A..32M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, pre-main sequence ; Spectra, infrared
Keywords: astrochemistry - line: formation - solid state: volatile -
techniques: spectroscopic - protoplanetary disks -
stars: variables: T Tauri, Herbig Ae/Be
Abstract:
The carbon content of protoplanetary disks is an important parameter
to characterize planets formed at different disk radii. There is some
evidence from far-infrared and submillimeter observations that gas in
the outer disk is depleted in carbon, with a corresponding enhancement
of carbon-rich ices at the disk midplane. Observations of the carbon
content inside of the inner sublimation rim could confirm how much
cpc on remains locked in kilometer size bodies in the disk.
I aim to determine the density, temperature, and carbon abundance
inside the disk dust sublimation rim in a set of T Tauri stars with
full protoplanetary disks.
Using medium-resolution, near-infrared (0.8 to 2.5um) spectra and
the new GAIA DR2 distances, I self-consistently determine the
stellar, extinction, veiling, and accretion properties of the 26 stars
in my sample. From these values, and non-accreting T Tauri spectral
templates, I extract the inner disk excess of the target stars from
their observed spectra. Then I identify a series of C0 recombination
lines in 18 of these disks and use the CHIANTI atomic line database
with an optically thin slab model to constrain the average ne, Te, and
nC for these lines in the five disks with a complete set of lines. By
comparing these values with other slab models of the inner disk using
the Cloudy photoionization code, I also constrain nH and the carbon
abundance, XC, and hence the amount of carbon 'missing' from the
slab. For one disk, DR Tau, I use relative abundances for the
accretion stream from the literature to also determine XSi and XN .
The inner disks modeled here are extremely dense (nH∼1016cm-3),
warm (Te∼4500K), and moderately ionized (logXe∼3.3). Three of the five
modeled disks show robust carbon depletion up to a factor of 42
relative to the solar value. I discuss multiple ways in which the
'missing' carbon could be locked out of the accreting gas. Given
the high-density inner disk gas, evidence for radial drift, and lack
of obvious gaps in these three systems, their carbon depletion is most
consistent with the 'missing' carbon being sequestered in
kilometer size bodies. For DR Tau, nitrogen and silicon are also
depleted by factors of 45 and 4, respectively, suggesting that the
kilometer size bodies into which the grains are locked were formed
beyond the N2 snowline. I explore briefly what improvements in the
models and observations are needed to better address this topic in the
future.
Description:
Tables with stellar parameters and CI emission line fluxes for 26
accreting T Tauri stars in the Taurus star-forming region are
presented. For each young star, the observation date, derived IR
spectral type, visual extinction, GAIA distance, stellar luminosity,
luminosity in Brackett gamma, accretion luminosity, accretion shock
filling factor, stellar radius, stellar mass, age, mass accretion
rate, and mean J-band veiling value are given. The raw fits files for
the spectral data are also presented, with three columns: wavelengths
in microns, fluxes in units of W/m2/um, and uncertainties in the
same units as the flux. The spectra were recorded with NASA's IRTF
SpeX in SXD mode, although the files may also contain merged Lowres15
or LXD spectra in addition the the SXD data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 139 26 *Targets and derived stellar parameters
table2.dat 139 26 *Integrated fluxes for major line complexes of
C0 and H0 Brγ observed in this sample
list.dat 135 40 List of fits spectra
sp/* . 40 Individual spectra
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Note on table2.dat: in most cases these include multi-line blends.
Note on table1.dat: All stellar quantities are derived here using the procedure
from McClure et al., 2013ApJ...769...73M 2013ApJ...769...73M.
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Star Central star name
17- 26 A10 "date" Obs.date Date of observation
28- 30 A3 --- SpType MK stellar spectral type
32- 35 I4 K Teff Effective stellar temperature
37- 39 F3.1 mag AV Extinction along the line of sight
41- 43 F3.1 mag e_AV rms uncertainty on AV
45- 49 F5.1 pc Dist Distance to the star (1)
51- 54 F4.1 pc E_Dist ? Error on AV (upper value)
56- 59 F4.1 pc e_Dist ? Error on AV (lower value)
61- 66 F6.2 Lsun L* Stellar luminosity
68- 73 E6.3 Lsun LBrg ? Luminosity in the H0 Brγ line
75- 80 E6.3 Lsun Lacc ? Accretion luminosity derived from Brγ
82- 87 E6.3 --- fsh ? Filling factor of the accretion shock on
the central star
89- 93 F5.2 Rsun R* Stellar radius
95- 99 F5.3 Msun M* Stellar mass (2)
101-104 F4.1 Myr Age Stellar age from the same tracks
106-112 E7.3 Msun/yr dM/dt ? Mass accretion rate derived from
Brγ (3)
114-116 F3.1 --- <rJ> Mean J-band veiling
118-139 A22 --- FileName Name of the fits file with spectrum
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Note (1): distance to the star using either the GAIA DR2 supplemental catalog
from Bailer-Jones et al. (2018AJ....156...58B 2018AJ....156...58B, Cat. I/347) or the default
distance of the Taurus star-forming region of 140pc Kenyon et al.,
1994AJ....108.1872K 1994AJ....108.1872K.
Note (2): stellar mass taken from the Siess et al. (2000A&A...358..593S 2000A&A...358..593S)
evolutionary tracks
Note (3): Missing mass accretion rates resulted in two sources, HP Tau and
HP Tau G3, for which the Brγ line was in absorption even after
subtracting the stellar photosphere.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Star Star name
17- 23 E7.3 mW/m2 F0.908um Integrated flux for line at 0.908um (1)
25- 32 A8 --- S/N0.908um S/N for line at 0.908um
34- 40 E7.3 mW/m2 F0.94um Integrated flux for line at 0.94um (1)
42- 49 A8 --- S/N0.94um S/N for line at 0.94um
51- 57 E7.3 mW/m2 F1.069um Integrated flux for line at 1.069um (1)
59- 67 A9 --- S/N1.069um S/N for line at 1.069um
69- 75 E7.3 mW/m2 F1.176um Integrated flux for line at 1.176um (1)
77- 85 A9 --- S/N1.176um S/N for line at 1.176um
87- 93 E7.3 mW/m2 F1.45um ? Integrated flux for line at 1.45um (1)
95-102 A8 --- S/N1.45um S/N for line at 1.45um
104-110 E7.3 mW/m2 F2.166um ? Integrated flux for line at 2.166um (1)
112-115 F4.1 --- S/N2.166um ? S/N for line at 2.166um
117-139 A23 --- Notes Notes
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Note (1): Limits of integration are as follows: 0.906-0.912 µm,
0.9395-0.942 µm, 1.0675-1.0705 µm, 1.174-1.177 µm,
1.4530-1.4560 µm, and 2.158-2.174 µm, respectively.
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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- 2 I2 h RAh Right ascension (J2000)
4- 5 I2 min RAm Right ascension (J2000)
7- 11 F5.2 s RAs Right ascension (J2000)
13 A1 --- DE- Declination sign (J2000)
14- 15 I2 deg DEd Declination (J2000)
17- 18 I2 arcmin DEm Declination (J2000)
20- 23 F4.1 arcsec DEs Declination (J2000)
25- 40 A16 --- Star Star name
41- 44 I4 --- Nx Number of pixels along X-axis
47- 49 I3 Kibyte size Size of FITS file
51- 87 A37 --- FileName Name of FITS file, in subdirectory sp
89-135 A47 --- Title Title of the FITS file
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Acknowledgements:
Melissa K. McClure, melissa.k.mcclure(at)gmail.com
(End) Melissa McClure [Leiden, Netherlands], Patricia Vannier [CDS] 18-Nov-2019