J/A+A/416/655 Atomic lines in IR spectra for ultracool dwarfs (Lyubchik+, 2004)
Atomic lines in infrared spectra for ultracool dwarfs
Lyubchik Y., Jones H.R.A., Pavlenko Y.V, Viti S., Pickering J.C.,
Blackwell-Whitehead R.
<Astron. Astrophys. 416, 655 (2004)>
=2004A&A...416..655L 2004A&A...416..655L
ADC_Keywords: Stars, dwarfs ; Spectra, infrared ; Atomic physics
Keywords: infrared: stars - stars: low mass - brown dwarfs - atomic data
Abstract:
We provide a set of atomic lines which are suitable for the
description of ultracool dwarf spectra from 10000 to 25000Å.
This atomic linelist was made using both synthetic spectra
calculations and existing atlases of infrared spectra of Arcturus
and Sunspot umbra. We present plots which show the comparison of
synthetic spectra and observed Arcturus and Sunspot umbral spectra
for all atomic lines likely to be observable in high resolution
infrared spectra.
Description:
Table 1 contains all identified lines with central intensities deeper
than 0.8 of residual flux using "ultracool dwarf model" identifications.
Table 2 investigates the sensitivity of priority 1 lines identified in
Table 1 to temperature, gravity and metallicity.
We compute some synthetic spectra for ultracool objects varying
parameters of Teff, log g and metallicity to show the sensitivity of
the central intensities of identified lines to these parameters. For
our computations we chose the minimal step in model atmospheres grid:
ΔTeff=100K, Δlogg=0.5, Δ[M/H]=-0.5.
STeff shows the dependence of residual fluxes on effective
temperature. For comparison a 2100/5.0/0.0 synthetic spectrum was
used. One can see that only a few lines show strong temperature
dependence for Δ=100K.
The NextGen 2000/4.5/0.0 model was used with 2000/5.0/0.0 to test
gravity sensitivity. The dependence for Δ(log g)=0.5 is also
relatively weak for most lines.
The NextGen model atmospheres 2000/5.0/-0.5 and 2000/5.0/0.0 to test
metallicity sensitivity. The metallicity dependence is relatively high
for all lines.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 51 198 Atomic lines found in ultracool dwarf synthetic
spectrum from 1-2.5um
table2.dat 46 51 Sensitivity of first priority lines to
temperature, gravity and metallicity.
tables.tex 127 418 LaTeX version of the tables
--------------------------------------------------------------------------------
See also:
J/ApJS/103/235 : Arcturus IR spectral atlas (Wallace+ 1996)
J/PASP/107/1042 : Infrared Arcturus Atlas (Hinkle+ 1995)
J/AJ/126/1526 : IR photometry of ultracool dwarfs (Bouy+, 2003)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- Pr ? Priority of the line for measurement of
atomic data (1)
3 A1 --- n_Ion [*] Note on measurements (2)
4- 12 F9.3 0.1nm lambda Wavelength of the line in air (3)
15- 18 A4 --- Ion Element name with ionization stage
21- 25 F5.3 --- UCDss Residual flux (F(line)/F(cont.)) in "ultracool
dwarf" synthetic spectrum
28- 32 F5.3 --- Arss Residual flux (F(line)/F(cont.)) in
"Arcturus-like" synthetic spectrum
34 A1 --- l_ArAt [~] Limit flag on ArAt (4)
35- 38 F4.2 --- ArAt ? Residual line intensity from hard copy of
Arcturus atlas (accuracy 0.01-0.02) (6)
39- 40 A2 --- n_ArAt [bl T] Note on ArAt (5)
43 A1 --- l_SsAt [~] Limit flag on SsAt (4)
44- 47 F4.2 --- SsAt ? Residual line intensity from hard copy of
Sunspot umbra atlas (accuracy 0.02-0.03) (5)
48- 49 A2 --- n_SsAt [bl T] Note on SsAt (5)
--------------------------------------------------------------------------------
Note (1): Priority of lines for measurement of atomic data:
Priority 1 indicates that atomic line is deeper than 0.6 in the
2000/5.0/0.0 synthetic spectrum. Also we include as first priority
three lines of Ti (22211.229, 22232.838, 22274.012Å) which are
shallower than 0.6. They are located far from strong atomic and
molecular lines and thus are good for identification purposes in the
spectra of ultracool dwarfs.
Priority 2 indicates that the residual flux of an atomic line is
between 0.8- 0.6.
Priority 3 indicates that the atomic line is located in the wing of a
nearby stronger line or in a wavelength region with strong telluric
absorption.
Atomic lines without an assigned priority might be relevant in the
analysis of ultracool dwarf spectra, but they are predicted to be weak
in the synthetic spectrum.
Note (2): An * indicates atomic lines of Rb, Y, Ba and Lu,
identified only using theoretical computations. Although these lines
are not seen in the observations of Arcturus and Sunspot umbra, they
are strong in synthetic spectrum computed for the 2000/5.0/0.0 model
atmosphere, and therefore also likely to be strong below 2000K.
Note (3): These values were taken fromVienna Atomic Line Data Base
(VALD, Kupka et al., 1999A&AS..138..119K 1999A&AS..138..119K). We check that wavelengths
from Arcturus and Sunspot umbra atlases identification files are in a
good agreement with VALD. The wavelengths of a few lines differ from
VALD values by less than 0.1Å in the region 10000-20000Å and by
less than 0.3Å beyond 20000Å.
Note (4): The symbol '~' means that part of the line in the hard copy of
the atlas is obscured by a gap in the data and the value given in the
table is for the visible part of the line.
Note (5): bl means that these lines are blended with stronger nearby lines
T indicates the two regions with strong telluric absorption
13600-14770Å and 18260-19450Å, regions between the J and H, and
H and K photometric bands. Lines identified from VALD in these regions
are difficult to observe in ground based observations but can be used
in probable future space observations of ultracool dwarfs.
Note (6): Linedepth information given in ArAt and SsAt is only used to
check the presence of a line in the observed spectra. Thus we do not
need high accuracy linedepth measurements for the observable spectra
of the Sunspot umbra and Arcturus.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.3 0.1nm lambda Wavelength
12- 15 A4 --- Atom Element name
18- 22 F5.3 --- LD Central line intensity in the ultra cool
(2000/5.0/0.0) synthetic spectrum
26- 30 F5.2 % STeff Temperature sensitivity (1)
33- 38 F6.2 % Slogg ? logg sensitivity (1)
41- 46 F6.2 % S[M/H] Metallicity sensitivity (1)
--------------------------------------------------------------------------------
Note (1): We show the difference of central intensity computations with
"new" models from central intensity computations for our "ultracool
dwarf model". Negative values indicate that a line is stronger in the
new model relative to the reference model 2000/5.0/0.0.
--------------------------------------------------------------------------------
Acknowledgements: Yuri Lyubchik
(End) Patricia Bauer [CDS] 27-Jan-2004