J/ApJ/888/54 Spectra of a rare low-mass Wolf-Rayet star in LMC (Margon+, 2020)
Discovery of a rare late-type, low-mass Wolf-Rayet star in the LMC.
Margon B., Manea C., Williams R., Bond H.E., Prochaska J.X.,
Szymanski M.K., Morrell N.
<Astrophys. J., 888, 54-54 (2020)>
=2020ApJ...888...54M 2020ApJ...888...54M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, Wolf-Rayet; Magellanic Clouds; Spectra, optical; Infrared;
Radial velocities; Equivalent widths
Keywords: WC stars; Planetary nebulae nuclei; Planetary nebulae
Abstract:
We report the serendipitous discovery of an object,
UVQSJ060819.93-715737.4, with a spectrum dominated by extremely
intense, narrow CII emission lines. The spectrum is similar to those
of the very rare, late-type [WC11] low-mass Wolf-Rayet stars. Despite
the recognition of these stars as a distinct class decades ago, there
remains barely a handful of Galactic members, all of which are also
planetary-nebula central stars. Although no obvious surrounding
nebulosity is present in J0608, [OII], [NII], and [SII] emission
suggest the presence of an inconspicuous, low-excitation nebula. There
is low-amplitude incoherent photometric variability on timescales of
days to years, as well as numerous prominent P Cygni profiles,
implying mass loss. There are indications of a binary companion. The
star is located on the outskirts of the LMC, and the observed radial
velocity (~+250km/s) and proper motion strongly suggest membership. If
indeed an LMC member, this is the first extragalactic late [WC] star,
and the first with an accurately determined luminosity, as the
Galactic examples are too distant for precise parallax determinations.
A high-quality, broad-coverage spectrum of the prototype of the late
[WC] class, CPD -56 8032, is also presented. We discuss different
excitation mechanisms capable of producing the great strength of the
CII emission. Numerous autoionizing levels of C II are definitely
populated by processes other than dielectronic recombination. Despite
the spectacular emission spectra, observational selection makes
objects such as these difficult to discover. Members of the [WC11]
class may in fact be considerably more common than the handful of
previously known late [WC] stars.
Description:
The UVQS spectrum of J060819.93-715737.4 was obtained on
UT 2015 February 14 with the Boller and Chivens spectrograph at the
2.5m du Pont telescope of the Las Campanas Observatory (∼4Å
spectral resolution).
The unusual nature of J0608 in the UVQS spectrum prompted us to seek
considerably higher signal-to-noise spectra with better resolution,
using the Magellan Echellette Spectrograph (MagE) on the Baade
Magellan telescope. Multiple exposures totaling 4200s were obtained on
2017 December 30, using a 1" slit which provides ∼1Å spectral
resolution. A second spectrum was obtained on 2019 May 3 with a
similar configuration.
Objects:
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RA (ICRS) DE Designation(s)
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06 08 19.94 -71 57 37.4 J0608 = UVQS J060819.93-715737.4
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 319 Identification and measurements of
UVQS J060819.93-715737.4 spectral lines
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See also:
III/85 : Sixth Catalogue of Galactic Wolf-Rayet Stars (van der Hucht+ 1981)
II/358 : SkyMapper Southern Sky Survey. DR1.1 (Wolf+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+AS/121/407 : LMC planetary nebulae positions (Leisy+ 1997)
J/A+AS/142/85 : Recombination coefficients for C II lines (Davey+, 2000)
J/A+A/403/659 : Classification of WR planetary nebulae (Acker+, 2003)
J/ApJS/149/157 : EMILI line-identification in IC 418 spectrum (Sharpee+, 2003)
J/AcA/59/335 : VI light curves of LMC R CBr stars (Soszynski+, 2009)
J/ApJ/724/748 : Galactic anticenter PNe and oxygen abundance (Henry+, 2010)
J/A+A/526/A6 : Central stars of galactic planetary nebulae (Weidmann+, 2011)
J/A+A/530/A90 : Optically bright post-AGB population of LMC (van Aarle+, 2011)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/AJ/152/25 : The UV-bright Quasar Survey (UVQS) DR1 (Monroe+, 2016)
J/ApJ/861/153 : Ultraviolet Extinction in the GALEX Bands. UVEXT (Sun+, 2018)
J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)
J/A+A/621/A38 : Gaia catalogue of hot subluminous stars (Geier+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Ion1 Line identifier (ion)
12- 18 F7.1 0.1nm rlam1 [3165.5/10830]? Ion1 rest wavelength in Å
20- 25 A6 --- Ion2 Added line identifier (ion) if any
27- 32 F6.1 0.1nm rlam2 ? Ion2 rest wavelength in Å
34- 40 A7 --- Trans1 Transition for Ion1
42- 47 A6 --- Trans2 Transition for Ion2
49- 53 A5 --- Type Line type
55- 60 F6.1 0.1nm OWave1 [3190/9257.5]? Observed wavelength
on Dec. 30, 2017 in Å
62 A1 --- l_RFlux1 Limit flag on RFlux1
63- 67 F5.2 --- RFlux1 [0.01/3.9]? Relative flux to the Hβ line
on Dec. 30, 2017 (1)
69- 73 F5.2 0.1nm EW1 [-1.2/-0.02]? Equivalent width
on Dec. 30, 2017 in Å
75- 77 I3 km/s RV1 [159/299]? Heliocentric radial velocity
on Dec. 30, 2017
79- 85 F7.1 0.1nm OWave2 [3168/10839]? Observed wavelength
on May 3, 2019 in Å
87- 90 F4.2 --- RFlux2 [0.03/3.5]? Relative flux to the Hβ line
on May 3, 2019 (2)
92- 96 F5.2 0.1nm EW2 [-0.9/-0.03]? Equivalent width
on May 3, 2019 in Å
98-100 I3 km/s RV2 [146/284]? Heliocentric radial velocity
on May 3, 2019
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Note (1): The 2017 Hβ+CII blend flux is 5e-15erg/s/Å/cm2
Note (2): The 2019 Hβ+CII blend flux is 5.7e-15erg/s/Å/cm2.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Jun-2021