J/ApJ/790/48 Variable stars in M31 & M33. II. LBVs (Humphreys+, 2014)
Luminous and variable stars in M31 and M33.
II. Luminous blue variables, candidate LBVs, Fe II emission line stars, and
other supergiants.
Humphreys R.M., Weis K., Davidson K., Bomans D.J., Burggraf B.
<Astrophys. J., 790, 48 (2014)>
=2014ApJ...790...48H 2014ApJ...790...48H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, blue ; Stars, giant ; Stars, variable ; Photometry, UBVRI ;
Photometry, infrared ; Spectroscopy ; Spectral types
Keywords: galaxies: individual: M31,M33; stars: massive; supergiants
Abstract:
An increasing number of non-terminal eruptions are being found in the
numerous surveys for optical transients. Very little is known about
these giant eruptions, their progenitors and their evolutionary state.
A greatly improved census of the likely progenitor class, including
the most luminous evolved stars, the luminous blue variables (LBVs),
and the warm and cool hypergiants is now needed for a complete picture
of the final pre-supernova stages of very massive stars. We have begun
a survey of the evolved and unstable luminous star populations in
several nearby resolved galaxies. In this second paper on M31 and M33,
we review the spectral characteristics, spectral energy distributions,
circumstellar ejecta, and evidence for mass loss for 82 luminous and
variable stars. We show that many of these stars have warm
circumstellar dust including several of the Fe II emission line stars,
but conclude that the confirmed LBVs in M31 and M33 do not. The
confirmed LBVs have relatively low wind speeds even in their hot,
quiescent or visual minimum state compared to the B-type supergiants
and Of/WN stars which they spectroscopically resemble. The nature of
the Fe II emission line stars and their relation to the LBV state
remains uncertain, but some have properties in common with the warm
hypergiants and the sgB[e] stars. Several individual stars are
discussed in detail. We identify three possible candidate LBVs and
three additional post-red supergiant candidates. We suggest that
M33-013406.63 (UIT301,B416) is not an LBV/S Dor variable, but is a
very luminous late O-type supergiant and one of the most luminous
stars or pair of stars in M33.
Description:
In Paper I (Humphreys et al. 2013ApJ...773...46H 2013ApJ...773...46H), we discussed a
small group of intermediate temperature supergiants, the warm
hypergiants, and suggested that they were likely post-red supergiants.
In this second paper, we review the spectral characteristics, spectral
energy distributions (SEDs), circumstellar ejecta, and mass loss of
the LBVs, candidate LBVs, emission line stars, and other luminous and
variable stars in M31 and M33.
The observations (described in paper I) were made in 2010 October with
the Hectospec Multi-Object Spectrograph on the 6.5m MMT on Mount Hopkins.
A few stars of special interest (5 in M31 and 8 in M33) were also
observed with the MODS1 spectrograph on the Large Binocular Telescope
(LBT) during commissioning in 2011 September, and in 2012 October and
November, and 2013 January.
All of the stars for which we have spectra are listed in Table 1 in
order of right ascension.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 187 87 Luminous stars and variables in M31 and M33:
spectroscopic summary
table2.dat 129 79 Multi-wavelength photometry
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See also:
J/ApJ/825/50 : Variable stars in M31 & M33. III. YSGs & RSGs (Gordon+, 2016)
J/ApJ/750/97 : The yellow and red supergiants of M33 (Drout+, 2012)
J/ApJ/743/19 : Photometry of variable star cand. in M31 (Clementini+, 2011)
J/MNRAS/411/263 : JHK variable stars in M33 (Javadi+ 2011)
J/A+A/522/A3 : M33 CO(2-1) and HI integrated intensity maps (Gratier+, 2010)
J/AJ/140/416 : IR photometry of massive stars in the SMC (Bonanos+, 2010)
J/ApJ/705/1364 : MIR catalog of point sources in M33 (Thompson+, 2009)
J/ApJ/703/441 : Yellow supergiants in M31 (Drout+, 2009)
J/ApJ/687/230 : Survey of M31 with Spitzer (Mould+, 2008)
J/AJ/134/2474 : Hα emission-line stars in 7 dwarfs gal. (Massey+, 2007)
J/ApJ/664/850 : Spitzer observations of stars in M33 (McQuinn+, 2007)
J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)
J/ApJ/505/793 : New WR star in M33 (Massey+, 1998)
J/ApJ/469/629 : UV-brightest stars of M33 and its nucleus (Massey+ 1996)
J/ApJS/89/85 : Blue and red supergiants in M33 (Ivanov+ 1993)
http://etacar.umn.edu/LuminousStars/M31M33/ : M31 & M33 variable stars
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Gal Galaxy identifier (M31 or M33)
5- 14 A10 --- Name Star name (1)
16- 34 A19 --- LGGS LGGS identifier (JHHMMSS.ss+DDMMSS.s)
36 A1 --- f_LGGS [ab] Flag on LGGS (2)
38- 52 A15 --- Group Spectral group (3)
54- 71 A18 --- SpT MK spectral type
73 A1 --- f_SpT [c] Flag on SpT (2)
75-173 A99 --- Notes Notes
175-187 A13 --- Star Star identifier as in table2;
column added by CDS (G1)
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Note (1): The M33C designation comes from an unpublished Hα survey
by Kerstin Weis.
Note (2): Flag as follows:
a = Massey et al. (2007, J/AJ/134/2474) labeled this star peculiar because
of an absorption line spectrum characteristic of an F-type star together
with FeII and hydrogen emission lines. This star is only about 1 arcsec
from a small cluster in M31 which was probably contaminating its spectrum
in their survey. Our spectrum observed with the LBT/MODS1 was obtained
under good seeing conditions and the cluster was kept off the slit. The
star is an FeII emission line star. HeIλ4026 is present in
absorption, and there are no F-type absorption lines.
b = The spectrum may have changed since Massey et al. (2007, J/AJ/134/2474).
The blue spectrum shows absorption lines typical of early B-type
supergiants while a strong OIλ7774 line common in A to F-type
supergiants is present in the red.
c = Several of the HeI absorption lines appear to be double including
λ4026, 4387, 4471, and 6678 due to emission in the line core.
Hα and Hβ are asymmetric with a second emission component on
the red side.
Note (3): The spectral groups are:
Fe II Em. Line (15 sources)
Hot Supergiant (19 sources)
Intermed-Type (18 sources)
LBV (classical luminous blue variable; 8 sources)
Of/WN (1 source)
Of/late-WN (11 sources)
Warm Hypergiant (7 sources)
foregrd (1 source)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Gal Galaxy identifier (M31 or M33)
5- 17 A13 --- Star Star identifier (G1)
19 A1 --- f_Star [cdef] Flag on Star (1)
21- 25 F5.2 mag Umag [14.9/21]? The U band magnitude
26- 26 A1 --- u_Umag [:] Uncertainty flag on Umag
28- 32 F5.2 mag Bmag [15/21.2]? The B band magnitude
34- 38 F5.2 mag Vmag [14.9/20.3]? The V band magnitude
40 A1 --- f_Vmag [v] Indicates a variable Vmag value
42- 46 F5.2 mag Rmag [15/20]? The R band magnitude
48- 52 F5.2 mag Imag [15/19.5]? The I band magnitude
54- 58 F5.2 mag Jmag [13.7/17.1]? The 2MASS J band magnitude
59 A1 --- u_Jmag [:] Uncertainty flag on Jmag
61- 65 F5.2 mag Hmag [13/17.2]? The 2MASS H band magnitude
66 A1 --- u_Hmag [:] Uncertainty flag on Hmag
68- 72 F5.2 mag Kmag [13/17]? The 2MASS K band magnitude
73 A1 --- u_Kmag [:] Uncertainty flag on Kmag
75- 79 F5.2 mag 3.6mag [12/17.3]? Spitzer/IRAC 3.6um band magnitude
81- 85 F5.2 mag 4.5mag [11.6/17]? Spitzer/IRAC 4.5um band magnitude
87- 91 F5.2 mag 5.8mag [11/15.1]? Spitzer/IRAC 5.8um band magnitude
93- 97 F5.2 mag 8.0mag [10/15]? Spitzer/IRAC 8.0 micron band magnitude
99-103 F5.2 mag 3.4mag [12/16.3]? WISE W1 (3.4um) band magnitude
105-109 F5.2 mag 4.6mag [11/16]? WISE W2 (4.6um) band magnitude
111-115 F5.2 mag 12mag [8/13.1]? WISE W3 (12um) band magnitude
117-120 F4.2 mag 22mag [5/9.5]? WISE W4 (22um) band magnitude
122-129 A8 --- Var Variability information
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Note (1): Flag as follows:
c = The photometry is from Humphreys et al. (2006AJ....131.2105H 2006AJ....131.2105H). Recent
CCD photometry obtained at the Barber Observatory, Univeristy of
Illinois Springfield, in October and December 2012 suggests that Var A
may have begun to brighten. Its current V magnitude is 18.36±0.05
measured relative to more than 40 comparison stars in the same field.
d = The two closest sources in the 2MASS catalog are offset from the
target by ∼3" at 01:33:27.26+30:30:32.1 and 01:33:27.29+30:30:32.4
and with nearly identical JHK magnitudes. We suspect that they may be
the same source. The identification is therefore doubtful. The closest
IRAC source is at 01:33:27.81+30:30:28.2.
e = The LBVs are variable, and both Var C and Var B experienced LBV-type
eruptions during the past decade. The 2MASS, IRAC, and WISE photometry
was not observed at the same time as the visual phoometry from
Massey et al. (2007, J/AJ/134/2474). The visual magnitudes for Var C,
however, are nearly the same as the B and V magnitudes published by
Szeifert et al. (1996A&A...314..131S 1996A&A...314..131S). We therefore adopted the
corresponding JHK photometry from Szeifert et al. (1996) for its SED
in Figure 8.
f = B324 is in a very crowded region and groundbased visual photometry of
B324 can be contaminated by nearby faint stars within an arcsec or so
of B324. For that reason we measured magnitudes from HST/WFPC2 F555W
and F439W obtained November 30, 1998. Converted to the standard V and B
magnitudes give 15.12 and 15.56 respectively. Slightly fainter than the
groundbased photometry.
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Global notes:
Note (G1): In this paper, we use the galaxy name and the R.A. of the star as
its designator for brevity and to save space in the tables.
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History:
From electronic version of the journal
References:
Humphreys et al. Paper I. 2013ApJ...773...46H 2013ApJ...773...46H
Humphreys et al. Paper II. 2014ApJ...790...48H 2014ApJ...790...48H This catalog
Gordon et al. Paper III. 2016ApJ...825...50G 2016ApJ...825...50G Cat. J/ApJ/825/50
Humphreys et al. Paper IV. 2017ApJ...836...64H 2017ApJ...836...64H Cat. J/ApJ/836/64
Humphreys et al. Paper V. 2017ApJ...844...40H 2017ApJ...844...40H Cat. J/ApJ/844/40
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-Aug-2016