J/MNRAS/513/5701 Silicate clouds in ultracool dwarfs (Suarez+, 2022)
Ultracool dwarfs observed with the Spitzer infrared spectrograph.
II. Emergence and sedimentation of silicate clouds in L dwarfs, and analysis of
the full M5-T9 field dwarf spectroscopic sample.
Suarez G., Metchev S.
<Mon. Not. R. Astron. Soc., 513, 5701-5726 (2022)>
=2022MNRAS.513.5701S 2022MNRAS.513.5701S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, dwarfs ; Spectra, infrared ; Photometry, millimetric/submm
Keywords: brown dwarfs - stars: atmospheres - infrared: stars
Abstract:
We present a uniform analysis of all mid-infrared R∼90 spectra of
field M5-T9 dwarfs obtained with the Spitzer Infrared Spectrograph
(IRS). The sample contains 113 spectra out of which 12 belong to
late-M dwarfs, 69 to L dwarfs, and 32 to T dwarfs. Sixty-eight of
these spectra are presented for the first time. We measure strengths
of the main absorption bands in the IRS spectra, namely water at
6.25um, methane at 7.65um, ammonia at 10.5um, and silicates over
8-11um. Water absorption is present in all spectra and strengthens
with spectral type. The onset of methane and ammonia occurs at the L8
and T2.5 types, respectively, although ammonia can be detectable as
early as T1.5. Silicate absorption sets in at spectral type L2, is on
average the strongest in L4-L6 dwarfs, and disappears past L8.
However, silicate absorption can also be absent from the spectra at
any L subtype. We find a positive correlation between the silicate
absorption strength and the excess (deviation from median)
near-infrared colour at a given L subtype, which supports the idea
that variations of silicate cloud thickness produce the observed
colour scatter in L dwarfs. We also find that variable L3-L7 dwarfs
are twice more likely to have above-average silicate absorption than
non-variables. The ensemble of results solidifies the evidence for
silicate condensate clouds in the atmospheres of L dwarfs, and for the
first time observationally establishes their emergence and
sedimentation between effective temperatures of ∼2000K and ∼1300K,
respectively.
Description:
Concatenation of Tables 1, 2, 4, and 5, which include, respectively,
select properties, observing log, observed and synthetic photometry,
and spectral index values of the main absorption bands for all 113 IRS
spectra of field M5-T9 dwarfs in this study.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tables.dat 447 113 Objects with IRS spectra
(tables 1, 2, 4 and 5 of the paper)
refs.dat 76 139 References
sp/* . 113 Individual spectra
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Byte-by-byte Description of file: tables.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Name Name of IRS targets
25- 33 A9 --- SName Short name of IRS targets
36- 57 A22 --- OName ? Alternative name of IRS targets
59- 66 F8.4 deg RAdeg Right Ascension (J2000)
68- 75 F8.4 deg DEdeg Declination (J2000)
77- 83 A7 --- Discovery Discovery reference
86- 92 A7 --- SpTypeopt Optical spectral type
94-100 A7 --- r_SpTypeopt Optical spectral type reference
106-112 A7 --- SpTypeir Infrared spectral type
114-120 A7 --- r_SpTypeir Infrared spectral type reference
125-131 A7 --- Binary Reference to binarity
133-139 A7 --- Variable Reference to variability
142-147 A6 --- Non-var Reference to no variability
155-159 I5 --- Program Program ID
162-196 A35 --- AORKEY Astronomical observation request key
198-212 A15 --- Module IRS spectroscopic module
214-228 A15 --- ExpTime Exposure time in each module
230-261 A32 --- ObsDate Observing date
263-280 A18 --- PI Program PI
282-284 I3 --- SNR6um ? Signal-to-noise ration at 6 um
290-292 I3 --- SNR12um ? Signal-to-noise ration at 12 um
299-311 A13 --- Publication Publication reference (1)
315-319 F5.2 mag CH4obs ? Observed IRAC [8.0] magnitude
323-326 F4.2 mag e_CH4obs ? Observed IRAC [8.0] magnitude error
332-338 A7 --- r_CH4obs ? Observed IRAC [8.0] magnitude reference
341-346 F6.3 mag W3obs ? Observed WISE W3 magnitude (2)
348-352 F5.3 mag e_W3obs ? Observed WISE W3 magnitude error (2)
356-361 F6.3 mag CH4syn ? Synthetic IRAC [8.0] magnitude (3)
364-368 F5.3 mag e_CH4syn ? Synthetic IRAC [8.0] magnitude error
373-378 F6.3 mag W3syn ? Synthetic WISE W3 magnitude (3)
380-384 F5.3 mag e_W3syn ? Synthetic WISE W3 magnitude error
388-391 F4.2 --- Water ? Water index value
394-397 F4.2 --- e_Water ? Water index value error
401-404 F4.2 --- Methane Methane index value
409-412 F4.2 --- e_Methane Methane index value error
418-421 F4.2 --- Ammonia Ammonia index value
426-429 F4.2 --- e_Ammonia Ammonia index value error
435-438 F4.2 --- Silicate ? Silicate index value
444-447 F4.2 --- e_Silicate ? Silicate index value error
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Note (1): A second reference (Suar22) is added when the target spectrum is not
shown nor available in the first reference.
Note (2): WISE W3 photometry from Cutri & et al. (2013, Cat. II/328).
Note (3): Synthetic magnitudes (corrected by the -0.064mag mean offset with
respect to the observations) from the IRS spectra.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 7 A7 -- Ref Reference code
9- 27 A19 --- BibCode BibCode
29- 54 A26 --- Aut Author's name
56- 76 A21 --- Com Comments
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Byte-by-byte Description of file (#): sp/*
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Bytes Format Units Label Explanations
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3- 10 F8.5 um lambda Wavelength
13- 21 F9.6 Jy Flux Flux
25- 32 F8.6 Jy e_Flux Flux error
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Acknowledgements:
Genaro Suarez, gsuarez(at)uwo.ca
References:
Suarez et al., Paper I 2021ApJ...920...99S 2021ApJ...920...99S
(End) Genaro Suarez [Univ. Western Ontario], Patricia Vannier [CDS] 19-Sep-2022