J/ApJ/805/57 Atmosphere parameters model-derived for PMS & BDs (Tottle+, 2015)
Testing model atmospheres for young very-low-mass stars and brown dwarfs in
the infrared: evidence for significantly underestimated dust opacities.
Tottle J., Mohanty S.
<Astrophys. J., 805, 57 (2015)>
=2015ApJ...805...57T 2015ApJ...805...57T (SIMBAD/NED BibCode)
ADC_Keywords: Spectral types ; Effective temperatures ; Extinction ; YSOs ;
Models ; Photometry, infrared
Keywords: brown dwarfs; stars: atmospheres; stars: formation;
stars: fundamental parameters; stars: low-mass;
stars: pre-main sequence; techniques: photometric
Abstract:
We test state-of-the-art model atmospheres for young very-low-mass
stars and brown dwarfs in the infrared, by comparing the predicted
synthetic photometry over 1.2-24µm to the observed photometry of
M-type spectral templates in star-forming regions. We find that (1) in
both early and late young M types, the model atmospheres imply
effective temperatures (Teff) several hundred Kelvin lower than
predicted by the standard pre-main sequence (PMS) spectral type-Teff
conversion scale (based on theoretical evolutionary models). It is
only in the mid-M types that the two temperature estimates agree. (2)
The Teff discrepancy in the early M types (corresponding to stellar
masses ≳0.4M☉ at ages of a few Myr) probably arises from
remaining uncertainties in the treatment of atmospheric convection
within the atmospheric models, whereas in the late M types it is
likely due to an underestimation of dust opacity. (3) The empirical
and model-atmosphere J-band bolometric corrections are both roughly
flat, and similar to each other, over the M-type Teff range. Thus the
model atmospheres yield reasonably accurate bolometric luminosities
(Lbol), but lead to underestimations of mass and age relative to
evolutionary expectations (especially in the late M types) due to
lower Teff. We demonstrate this for a large sample of young Cha I and
Taurus sources. (4) The trends in the atmospheric model J-Ks colors,
and their deviations from the data, are similar at PMS and main
sequence ages, suggesting that the model dust opacity errors we
postulate here for young ages also apply at field ages.
Description:
Our final Cha I sample selected from Luhman et al. 2008, J/ApJ/675/1375
consists of 78 Class III M-type sources, all with NIR and MIR
photometry and assigned spectral types.
Our final Taurus sample selected from Luhman et al. 2010, J/ApJS/186/111
consists of 96 Class III M-type sources.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 78 Properties of the 78 class III Cha I objects
table2.dat 90 96 Properties of the 96 class III Taurus objects
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/ApJ/767/95 : Improved parameters of smallest KIC stars (Dressing+, 2013)
J/ApJ/731/8 : Multiple star formation in Taurus-Auriga (Kraus+, 2011)
J/ApJS/196/4 : New young star candidates in Taurus-Auriga (Rebull+, 2011)
J/ApJS/186/259 : Taurus Spitzer survey: new candidate members (Rebull+, 2010)
J/ApJS/186/111 : Spitzer observations of Taurus members (Luhman+, 2010)
J/ApJ/684/654 : Low-mass members of Chamaeleon I (Luhman+, 2008)
J/ApJ/675/1375 : IRAC/MIPS photometry in Cha I (Luhman+, 2008)
J/A+A/478/507 : Distances & atmospheric param. of MSU stars (Morales+, 2008)
J/ApJS/173/104 : Stellar population in Chamaeleon I (Luhman, 2007)
J/A+A/446/485 : New very low-mass members in Taurus (Guieu+, 2006)
J/ApJ/645/676 : Spatial distribution of brown dwarfs in Taurus (Luhman+, 2006)
J/ApJ/602/816 : Chamaeleon I star-forming region census (Luhman, 2004)
J/A+A/416/555 : Brown Dwarfs in ChaI Dark Cloud (Lopez-Marti+ 2004)
J/A+A/337/403 : Low-mass stars evolutionary models (Baraffe+ 1998)
J/ApJS/101/117 : UBVRIJHKLMNQ photometry in Taurus-Auriga (Kenyon+ 1995)
Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Name Star name (JHHMMSSss-DDMMSSs)
19 A1 --- f_Name [eh] Flag on Name (1)
21- 22 A2 --- l_SpT [≥] Limit flag on SpT (2)
23- 27 A5 --- SpT MK spectral type
29- 33 F5.2 mag Jmag [8.3/17.9] J-band magnitude from 2MASS
unless flagged
34 A1 --- f_Jmag [cd] Flag on Jmag (1)
36- 40 F5.2 mag Hmag [7.6/16.8] H-band magnitude from 2MASS
unless flagged
41 A1 --- f_Hmag [cd] Flag on Hmag (1)
43- 47 F5.2 mag Kmag [7.4/16] K-band magnitude from 2MASS
unless flagged
48 A1 --- f_Kmag [cd] Flag on Kmag (1)
50- 53 F4.2 --- AjL [0/7] J-band extinction (AJ,L) (3)
55- 56 A2 --- l_TL [≤] Limit flag on TL
57- 60 I4 K TL [2300/3850] Effective temperature (3)
62- 68 F7.5 Lsun LL [0.0003/2.5] Bolometric luminosity (3)
70- 73 F4.2 --- Aj [0/7] Atmosphere-fit J-band NIR extinction
(AJ,NIR)
74- 76 A3 --- f_Aj [ ,abfg] Flag on Aj (1)
78- 79 A2 --- l_TA [≤] Limit flag on TA
80- 83 I4 K TA [1925/3550] Atmosphere-fit temperature TA
85- 91 F7.5 Lsun LA [0.0005/2] Atmosphere-fit bolometric luminosity
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Note (1): Flag as follows:
a = Flagged due to the best fit AJ having an rms above 1.00.
b = Flagged due to the best fit AJ differing to the Luhman (2007,
J/ApJS/173/104) derived value by above 0.5.
c = Photometry taken from Luhman (2004ApJ...614..398L 2004ApJ...614..398L) due to it being an
unresolved binary in 2MASS.
d = Photometry taken from Luhman (2007, J/ApJS/173/104) from his ISPI
measurements.
e = Known binary (Lafreniere et al. 2008ApJ...683..844L 2008ApJ...683..844L).
f = Flagged due to the best fit AJ differing to the
Luhman (2010ApJS..186..111L 2010ApJS..186..111L) derived value by above 0.5.
g = Flagged due to the best fit AJ having an rms above 1.00 and best fit
AJ differing to the Luhman (2010ApJS..186..111L 2010ApJS..186..111L) derived value by
above 0.5.
h = Known binary (Kraus et al. 2011, J/ApJ/731/8).
Note (2): Two sources have no available optical spectra, and have been assigned
a rough spectral type of ≥M9 by Luhman (2007, J/ApJS/173/104), based
on comparisons of their NIR spectra to those of other late-type
objects.
Note (3): Parameters derived by "Luhman" techniques (L). See section 2.2.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 10-Mar-2016