J/ApJ/942/85 CII em-line stars in LMC. II. Final results (Margon+, 2023)
A survey for CII emission-line stars in the Large Magellanic Cloud.
II. Final results and the origin of CII emission in [WC] spectra.
Margon B., Morrell N., Massey P., Neugent K.F., Williams R.
<Astrophys. J., 942, 85 (2023)>
=2023ApJ...942...85M 2023ApJ...942...85M
ADC_Keywords: Stars, Wolf-Rayet; Spectra, optical; Spectral types;
Magnitudes, absolute; Colors; Infrared sources; Magellanic Clouds;
Planetary nebulae
Keywords: Planetary nebulae nuclei ; Wolf-Rayet stars
Abstract:
We present the final results of an imaging and spectroscopic search
for stars in the Large Magellanic Cloud (LMC) with
CIIλλ7231,7236 emission lines. The goal is to identify
and study [WC11] stars, the coolest of the low-mass Wolf-Rayet
sequence, and a subset of central stars of planetary nebulae where the
CII lines are known to be especially prominent. A recent serendipitous
discovery of an LMC [WC11] raised the possibility that these objects,
although difficult to identify, might in fact be more common than
previously believed. Several new members of this rare class have been
found in this survey. It now seems clear, however, that a significant
number of these stars are not hiding among the general [WC]
population. We point out that the CII doublet intensity ratio observed
in our spectra proves to neatly divide the objects into two distinct
groups, with the CII emission likely originating from either the
stellar wind or a surrounding nebula. The physics of the CII emission
mechanism correctly explains this bifurcation. Spectral subtypes are
suggested for most of the objects. The numerous spectroscopic clues
now available for these objects should facilitate future detailed
modeling.
Description:
Paper I (Margon+ 2020, J/ApJ/898/85) describes in detail how
candidates were selected.
That publication also reports a preliminary spectroscopic
reconnaissance of a small number of the candidates, using the MagE
Spectrograph on the 6.5m Baade Magellan telescope of the Las Campanas
Observatory. The observations described here used this same
configuration, yielding complete wavelength coverage from 3150Å,
near the atmospheric cutoff, up to ∼10000Å at intermediate
resolution (R∼4100).
In addition to the observations described in Paper I, during
2020 November and December we obtained further spectra of the most
promising CII emission candidates, each selected in the imaging survey
described in Paper I. There were a total of 28 stars observed, with
typical exposure times of 600-1200s.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 78 9 Spectroscopically verified LMC CII emission stars
table2.dat 62 19 Spectra of candidates lacking CII emission
sp/* . 8 *Individual spectra in FITS format
-- Data behind Figures 1 and 2
fig4/* . 19 *Individual spectra in FITS format
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Note on sp/* and fig4/*: These are simple 1D spectra of wavelength (Angstroms)
and flux (erg/cm2/s/Angstrom). Additional observational details are
given in the header. The spectra are not corrected for telluric
absorption, and the spectrophotometric flux calibration should be
considered approximate.
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See also:
III/85 : Sixth Catalogue of Galactic Wolf-Rayet Stars (van der Hucht+ 1981)
III/215 : 7th Catalog of Galactic Wolf-Rayet stars (van der Hucht, 2001)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
VII/259 : 6dF galaxy survey final redshift release (Jones+, 2009)
J/MNRAS/234/583 : Abundances in Magellanic Cloud PNe (Monk+ 1988)
J/AJ/99/784 : IR photometry of LMC long-period variables (Hughes+ 1990)
J/ApJS/75/407 : LMC & SMC PNe optical spectroscopy. I (Meatheringham+ 1991)
J/A+A/403/659 : Classification of WR planetary nebulae (Acker+, 2003)
J/AJ/128/1606 : Magellanic Clouds Photometric Survey: LMC (Zaritsky+, 2004)
J/A+A/442/249 : Integrated spectrum of NGC 7027 (Zhang+, 2005)
J/AJ/133/2393 : UBVRI phot. in seven Local Group dwarfs gal. (Massey+, 2007)
J/A+A/530/A90 : Optically bright post-AGB pop. of LMC (van Aarle+, 2011)
J/ApJ/831/L3 : NIR spectra of 10 PNe in LMC and SMC (Mashburn+, 2016)
J/A+A/588/A25 : AGB & CSPNe evolutionary models (Miller Bertolami, 2016)
J/ApJ/888/54 : Spectrum of a rare low-mass WR star in LMC (Margon+, 2020)
J/ApJ/898/85 : CII emission-line stars in LMC with MagE sp. (Margon+, 2020)
J/MNRAS/493/1512 : Galactic Wolf-Rayet stars with Gaia DR2 I (Rate+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- 2MASS 2MASS identifier (HHMMSSSss+DDMMSSs; J2000)
18- 22 F5.2 mag Vmag [15/16.33] Johnson V magnitude (G1)
24- 27 F4.1 mag VMag [-3.9/-2.5] Absolute V magnitude (G1)
29- 33 F5.2 mag B-V [-0.16/1.22] B-V color index (G1)
35- 39 F5.2 mag U-B [-1.1/0.4] U-B color index (G1)
41- 45 F5.3 --- CII/Hb [0.002/2.8]? CII λ7231 to
Hβ ratio
47- 50 F4.2 --- CII [0.47/1] CII λ7231 to λ7236
ratio
52- 58 A7 --- Class Class
60- 62 A3 --- Ref Reference(s) (1)
64- 78 A15 --- File Name of the FITS file in subdirectory "sp";
column added by CDS
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Note (1): Reference as follows:
1 = this work
2 = Paper I (Margon+ 2020, J/ApJ/898/85)
3 = van Aarle et al. 2011, J/A+A/530/A90
4 = Margon et al. 2020, J/ApJ/888/54
5 = Williams et al. 2021ApJ...906...31W 2021ApJ...906...31W
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- 2MASS 2MASS identifier (HHMMSSSss+DDMMSSs; J2000)
18- 22 F5.2 mag Vmag [13.6/18.84] Johnson V-band magnitude (G1)
24- 42 A19 --- Class Classification
44 I1 --- n_Class [1/5]? Note (1)
46- 62 A17 --- File Name of the FITS file in subdirectory "fig4";
column added by CDS
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Note (1): Note (see the Appendix) as follows:
1 = There is no previous spectral information in the literature for
J05022531-6552527. We classify this object as B[e], with quite weak
but still well-detected nebular forbidden lines of [OII], [NII], and
[SII] in our spectrum. These stars are rare but not unknown in the
Magellanic Clouds (Zickgraf 2006ASPC..355..135Z 2006ASPC..355..135Z).
2 = Object J05060423-7016513 is cataloged as a carbon star, WORC 82,
and a known high-amplitude (∼2.5mag) variable.
O'Grady+ 2020ApJ...901..135O 2020ApJ...901..135O give a period (840d) and light curve. Our
spectrum shows no obvious C2 or CN bands, but unfortunately occurred
near minimum light and is thus poorly exposed. Strong Balmer and Ca IR
triplet emission, as well as the NaD doublet in absorption, are
evident. Extremely prominent LiIλ6707 absorption is also
present, a typical characteristic of the highly variable "super-AGB
stars" discussed by O'Grady+ (2020).
3 = J05144238-6535497 proves to be a previously uncatalogued emission-line
galaxy (ELG) at z=0.101, with our spectrum (Figure 4) showing strong,
narrow Balmer, [OII], [OIII], [NII], and [SII] emission. At this
redshift, the Hα and [NII] emission fall within our on-band
CIIλλ7231,7236 imaging filter, explaining the selection
of the object in our sample. See the appendix for further explanations.
4 = We find no previous spectroscopy cited in the literature for
J05313424-6901217. Our spectrum is that of a Be shell star, with the
classic Hα profile of broad emission bisected by strong, narrow
absorption, as well as broad HeI absorption.
5 = We classify J05334283-7003193 as an S star, confirming the tentative
suggestion by Hughes & Wood (1990, J/AJ/99/784). There are multiple
prominent ZrO bands, NaD absorption, very strong, narrow Balmer
emission, and probable CN bands. No obvious LiIλ6707 is seen.
Smith+ (1995ApJ...441..735S 1995ApJ...441..735S) type this object as a carbon star.
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Global notes:
Note (G1): The photometry is from Zaritsky+ 2004, J/AJ/128/1606
See Section 3.1 for assumptions on distance and extinction used to
derive VMag.
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History:
From electronic version of the journal
References:
Margon et al. Paper I. 2020ApJ...898...85M 2020ApJ...898...85M Cat. J/ApJ/898/85
(End) Emmanuelle Perret [CDS] 18-Nov-2024