J/MNRAS/505/5567 Red Be Stars in the LMC and the SMC (Vieira+, 2021)
Red Be stars in the Magellanic Clouds?
Vieira K., Garcia-Varela A., Sabogal B., Rimulo L.R., Hernandez J.
<Mon. Not. R. Astron. Soc., 505, 5567-5583 (2021)>
=2021MNRAS.505.5567V 2021MNRAS.505.5567V (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, B-type ; Stars, Be ; Infrared ;
Photometry, millimetric/submm ; Photometry ; Optical ;
Parallaxes, trigonometric ; Proper motions
Keywords: parallaxes; proper motion - stars: emission-line, Be -
Magellanic Clouds
Abstract:
We revisit the subject of Be candidate stars towards the Magellanic
Clouds, previously studied by the authors using SPM4 proper motions.
We obtain Gaia DR2 parallaxes and proper motions for 2357 and 994 LMC
and SMC Be candidates, respectively. Parallaxes and proper motions
versus colour V - I easily reveal the presence of the redder galactic
contaminant foreground, as concluded in our previous work, but this
time we do find a few red Be candidates consistent with being true
Magellanic objects. A membership assessment to each Magellanic Cloud
is done for each Be candidate, based on the distribution of their
parallaxes and proper motions. From a compilation of published
catalogues of spectroscopically confirmed emission line stars,we find
that 41 (LMC) and 56 (SMC) of the Be candidates have shown the
Hα line in emission. Near-infrared IRSF JHKs magnitudes are
obtained for about 70 per cent of the Be candidates with Gaia DR2
astrometric data. Mid-infrared SAGE IRAC 3.6, 4.5, 5.8, and 8.0 µm
magnitudes are obtained for about 85 per cent as well. After
discarding possible Herbig Ae/Be stars, one LMC and three SMC B
emission line confirmed stars show significantly redder optical,
near and mid-infrared colours than what has been typically measured for
Classical Be stars - they are called red Be stars. Taking into account
that classical Be stars do not show these red colours, further studies
about these four stars are needed in order to establish their true
nature and explain the observed red excess.
Description:
The main purpose of our work is to clean the Be candidates and
matching with Gaia DR2, do statistical analysis of their parallaxes and
proper motions and membership, assessment crossmatch with
spectroscopic catalogues to obtain the list of spectroscopically
confirmed B emission line (BEL) stars, distribution of the light curve
variability types of Be candidate and BEL stars near- and mid-IR
photometry and thus finding redder than expected Magellanic confirmed
BEL and Be candidate stars.
Be candidate stars for the LMC and SMC were obtained from Sabogal et
al. (2005MNRAS.361.1055S 2005MNRAS.361.1055S, Cat. J/MNRAS/361/1055) and Mennickent et al.
(2002A&A...393..887M 2002A&A...393..887M, Cat. J/A+A/393/887), respectively, where a total
of 2446 and 1019 candidates are listed. In Vieira et al.
(2017MNRAS.469.4175V 2017MNRAS.469.4175V, J/MNRAS/469/4175) we found that OGLE II has a
slightly larger set of very similar entries, all correspond to pairs
of stars, and located less than 2 arcsec from each other, with very
similar photometry (< 0.1 magnitude differences) in the three BVI
bands. These are repeated entries with bad enough astrometry to end up
listed as different stars instead of the same and in many cases, they
have different OGLE II identifications (which is based on their
coordinates). One entry per pair was kept (the first one listed), so
the clean lists of Be candidates have 2393 and 1004 stars, towards the
LMC and SMC, respectively.
After data reduction, multiple data analysis and crossmatches with
Gaia DR2, OGLE II, IRAC, IRSF and BEL catalogues (i.e sections 3-8).
We are able to extract spectroscopic and photometric properties of our
clean samples as shown in tablea1.dat and tablea2.dat. Additionally, we
provide in tablea2.dat, properties of four exceptionally red Be stars
(i.e section 9 and 10) on which we detail causes and consequences
of their redder colours values.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 273 2393 Sample of the LMC Be stars data used
in this study
tablea2.dat 269 4 Sample of the four exceptionally red Be stars,
ID = 909 is in the LMC and ID = 75, 184,
and 547 are in the SMC
tablea3.dat 317 1004 Sample of the SMC Be stars data used
in this study
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See also:
J/MNRAS/361/1055 : BVI photometry of LMC Be stars (Sabogal+, 2005)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/305 : SAGE LMC and SMC IRAC Source Catalog (IPAC 2009)
II/288 : IRSF Magellanic Clouds Point Source Catalog (Kato+ 2007)
J/A+A/462/683 : Velocities in SMC field of NGC 330 (Martayan+, 2007)
J/A+A/509/A11 : Hα emission-line objects in SMC clusters
(Martayan+, 2010)
J/MNRAS/421/3622 : Candidate Be stars in the Magellanic Clouds (Paul+, 2012)
J/ApJ/771/111 : SMC dusty OB stars. I. Optical spectroscopy (Sheets+, 2013)
J/MNRAS/425/355 : Hot stars in LMC UKST Hα survey (Reid+, 2012)
J/MNRAS/421/3622 : Candidate Be stars in the Magellanic Clouds (Paul+, 2012)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Identifier number index from this work (idBe)
6- 21 A16 --- OGLE Designation HHMMSSss-DDMMSSs (J2000)
(OGLE) (G1)
23- 28 F6.3 mag Vmag Apparent magnitude in V band (Vmag) (G1)
30- 35 F6.3 mag B-V B-V colour index (B-V) (G1)
37- 42 F6.3 mag V-I V-I colour index (V-I) (G1)
44- 46 F3.1 --- Type [1/4] Type of the star (Type_num) (G2)
48- 66 I19 --- GaiaDR2 Gaia DR2 source identifier
(GaiaDR2sourceid) (G3)
68- 81 F14.11 deg RAdeg Barycentric right ascension (ICRS)
at Ep=2015.5 (ra) (G3)
83- 97 F15.11 deg DEdeg Barycentric declination (ICRS)
at Ep=2015.5 (dec) (G3)
99-105 F7.4 mas plx ?=- Absolute stellar parallax (parallax) (G3)
107-112 F6.4 mas e_plx ?=- Mean error of plx (parallax_error) (G3)
114-120 F7.3 mas/yr pmRA ?=- Proper motion in right ascension direction
pmRA*cosDE (pmra) (G3)
122-126 F5.3 mas/yr e_pmRA ?=- Mean error of pmRA (pmra_error) (G3)
128-134 F7.3 mas/yr pmDE ?=- Proper motion in declination direction
(pmdec) (G3)
136-140 F5.3 mas/yr e_pmDE ?=- Mean error of pmDE (pmdec_error) (G3)
142-150 F9.6 mag Gmag G-band mean magnitude (Vega)
(photgmean_mag) (G3)
152-160 F9.6 mag BPmag ?=- Integrated BP mean magnitude (Vega)
(photbpmean_mag) (G3)
162-170 F9.6 mag RPmag ?=- Integrated RP mean magnitude (Vega)
(photrpmean_mag) (G3)
172-191 F20.18 --- Rank Position mag ranking value (rank) (G4)
193-213 F21.17 --- Chi ?=- Χ-value for membership to the Clouds
(Χ) (G5)
215-227 A13 --- ONames BEL crossmatch confirmed with linked catalogues
(other_names) (G6)
229-233 F5.2 mag Jmag ?=- Apparent magnitude in J band (Jmag) (G7)
235-239 F5.2 mag Hmag ?=- Apparent magnitude in H band (Hmag) (G7)
241-245 F5.2 mag Ksmag ?=- Apparent magnitude in Ks band (Ksmag) (G7)
247-252 F6.3 mag 3.6mag ?=- Apparent magnitude Spitzer/IRAC at 3.6
micron band magnitude ([3.6]) (G8)
254-259 F6.3 mag 4.5mag ?=- Apparent magnitude Spitzer/IRAC
at 4.5 micron band magnitude ([4.5]) (G8)
261-266 F6.3 mag 5.8mag ?=- Apparent magnitude Spitzer/IRAC
at 5.8 micron band magnitude ([5.8]) (G8)
268-273 F6.3 mag 8.0mag ?=- Apparent magnitude Spitzer/IRAC
at 8.0 micron band magnitude ([8.0]) (G8)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID Identifier number index from this work (idBe)
5- 22 A18 --- OGLE Designation HHMMSSss-DDMMSSs (J2000)
(OGLE) (G1)
24- 29 F6.3 mag Vmag Apparent magnitude in V band (Vmag) (G1)
31- 36 F6.3 mag B-V B-V colour index (B-V) (G1)
38- 43 F6.3 mag V-I V-I colour index (V-I) (G1)
45- 47 F3.1 --- Type [1/4] Type of the star (Type_num) (G2)
49- 67 I19 --- GaiaDR2 Gaia DR2 source identifier
(GaiaDR2sourceid) (G3)
69- 82 F14.11 deg RAdeg Barycentric right ascension (ICRS)
at Ep=2015.5 (ra) (G3)
84- 98 F15.11 deg DEdeg Barycentric declination (ICRS)
at Ep=2015.5 (dec) (G3)
100-106 F7.4 mas plx Absolute stellar parallax (parallax) (G3)
108-113 F6.4 mas e_plx Mean error of plx (parallax_error) (G3)
115-119 F5.3 mas/yr pmRA Proper motion in right ascension direction
pmRA*cosDE (pmra) (G3)
121-125 F5.3 mas/yr e_pmRA Mean error of pmRA (pmra_error) (G3)
127-132 F6.3 mas/yr pmDE Proper motion in declination direction
(pmdec) (G3)
134-138 F5.3 mas/yr e_pmDE Mean error of pmDE (pmdec_error) (G3)
140-148 F9.6 mag Gmag G-band mean magnitude (Vega)
(photgmean_mag) (G3)
150-159 F10.6 mag BPmag Integrated BP mean magnitude (Vega)
(photbpmean_mag) (G3)
161-169 F9.6 mag RPmag Integrated RP mean magnitude (Vega)
(photrpmean_mag) (G3)
171-189 F19.17 --- Rank Position mag ranking value (rank) (G4)
191-208 F18.16 --- Chi Χ-value for membership to the Clouds
(Χ) (G5)
210-223 A14 --- ONames BEL crossmatch confirmed with linked
catalogues (other_names) (G6)
225-229 F5.2 mag Jmag Apparent magnitude in J band (Jmag) (G7)
231-235 F5.2 mag Hmag Apparent magnitude in H band (Hmag) (G7)
237-241 F5.2 mag Ksmag Apparent magnitude in Ks band (Ksmag) (G7)
243-248 F6.3 mag 3.6mag Apparent magnitude Spitzer/IRAC
at 3.6 micron band magnitude ([3.6]) (G8)
250-255 F6.3 mag 4.5mag Apparent magnitude Spitzer/IRAC
at 4.5 micron band magnitude ([4.5]) (G8)
257-262 F6.3 mag 5.8mag Apparent magnitude Spitzer/IRAC
at 5.8 micron band magnitude ([5.8]) (G8)
264-269 F6.3 mag 8.0mag Apparent magnitude Spitzer/IRAC
at 8.0 micron band magnitude ([8.0]) (G8)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Identifier number index from this work (idBe)
6- 23 A18 --- OGLE Designation HHMMSSss-DDMMSSs (J2000)
(OGLE) (G1)
25- 30 F6.3 mag Vmag Apparent magnitude in V band (Vmag) (G1)
32- 37 F6.3 mag B-V B-V colour index (B-V) (G1)
39- 44 F6.3 mag V-I V-I colour index (V-I) (G1)
46- 48 F3.1 --- Type [1/4] Type of the star (Type_num) (G2)
50- 68 I19 --- GaiaDR2 Gaia DR2 source identifier
(GaiaDR2sourceid) (G3)
70- 83 F14.11 deg RAdeg Barycentric right ascension (ICRS)
at Ep=2015.5 (ra) (G3)
85- 99 F15.11 deg DEdeg Barycentric declination (ICRS)
at Ep=2015.5 (dec) (G3)
101-107 F7.4 mas plx ?=- Absolute stellar parallax (parallax) (G3)
109-114 F6.4 mas e_plx ?=- Mean error of plx (parallax_error) (G3)
116-122 F7.3 mas/yr pmRA ?=- Proper motion in right ascension direction
pmRA*cosDE (pmra) (G3)
124-128 F5.3 mas/yr e_pmRA ?=- Mean error of pmRA (pmra_error) (G3)
130-136 F7.3 mas/yr pmDE ?=- Proper motion in declination
direction (pmdec) (G3)
138-142 F5.3 mas/yr e_pmDE ?=- Mean error of pmDE (pmdec_error) (G3)
144-152 F9.6 mag Gmag G-band mean magnitude (Vega)
(photgmean_mag) (G3)
154-162 F9.5 mag BPmag ?=- Integrated BP mean magnitude (Vega)
(photbpmean_mag) (G3)
164-172 F9.6 mag RPmag ?=- Integrated RP mean magnitude (Vega)
(photrpmean_mag) (G3)
174-192 F19.17 --- Rank Position mag ranking value (rank) (G4)
194-214 F21.17 --- Chi ?=- Χ-value for membership to the Clouds
(Χ) (G5)
216-271 A56 --- ONames BEL crossmatch confirmed with linked
catalogues (other_names) (G6)
273-277 F5.2 mag Jmag ?=- Apparent magnitude in J band (Jmag) (G7)
279-283 F5.2 mag Hmag ?=- Apparent magnitude in H band (Hmag) (G7)
285-289 F5.2 mag Ksmag ?=- Apparent magnitude in Ks band (Ksmag) (G7)
291-296 F6.3 mag 3.6mag ?=- Apparent magnitude Spitzer/IRAC
at 3.6 micron band magnitude ([3.6]) (G8)
298-303 F6.3 mag 4.5mag ?=- Apparent magnitude Spitzer/IRAC
at 4.5 micron band magnitude ([4.5]) (G8)
305-310 F6.3 mag 5.8mag ?=- Apparent magnitude Spitzer/IRAC
at 5.8 micron band magnitude ([5.8]) (G8)
312-317 F6.3 mag 8.0mag ?=- Apparent magnitude Spitzer/IRAC
at 8.0 micron band magnitude ([8.0]) (G8)
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Global notes:
Note (G1): Taken from Sabogal et al. 2005MNRAS.361.1055S 2005MNRAS.361.1055S, Cat. J/MNRAS/361/1055
Note (G2): As detailed in Sabogal et al. 2005MNRAS.361.1055S 2005MNRAS.361.1055S,
Cat. J/MNRAS/361/1055, we class types of Be-stars as follows:
1.0 = Type-1 stars, showing outbursts
1.5 = Type-1 stars with luminosity jumps in their light curves
2.0 = Type-2 stars, showing sudden luminosity jumps
(i.e. high and low states)
3.0 = Type-3 stars, showing periodic or near-periodic variations
4.0 = Type-4 stars, showing light curves similar to Galactic
Be stars.
Note (G3): Taken from Gaia DR2 (Gaia Collaboration, 2018A&A...616A...1G 2018A&A...616A...1G,
Cat. I/345), see its corresponding data descriptions
for more details.
Note (G4): As explicited in the section 3, to properly crossmatch the Be
candidates with Gaia DR2, we considered closeness
(estimated with the Rank parameter) not only in sky
position but also in photometry, since the Gaia DR2 G-band is close
enough to the OGLE-II V-band, as to serve to clean up possible
misidentifications. The Gaia DR2 match was chosen as the star having
the lowest value of the Rank expressed as
SQRT((Δθ/θmax)2 + (V-G/1mag)2),
where Δθ is the sky angular separation in arcseconds
between the (RA, DEC) coordinates listed for the Be candidates
and the Gaia DR2 ones, θmax = 2 arcsec for the SMC and
θmax= 4 arcsec for the LMC.
Note (G5): As described in the section 6.1 Membership assessment, in any cases,
Magellanic stars cluster around zero simultaneously in standardized
parallax and proper motions. This leads us to define a new variable
Χ-value as
SQRT((pmRA*cosDEstd)2 + (plxstd)2 + (pmDEstd)2),
where std stands for standardized values.
Note (G6): As explained in the section 7 crossmatch with spectroscopic
catalogues, our lists of Be candidates were crossmatched with several
previous publications and online databases of spectroscopically
confirmed Be stars towards the Magellanic Clouds areas as :
SMC = Martayan et al. 2007A&A...462..683M 2007A&A...462..683M, Cat. J/A+A/462/683;
Martayan et al. 2010A&A...509A..11M 2010A&A...509A..11M, Cat. J/A+A/509/A11;
Paul et al. 2012MNRAS.421.3622P 2012MNRAS.421.3622P, Cat. J/MNRAS/421/3622;
Be Stars Spectra database (http://basebe.obspm.fr);
Sheets et al. 2013ApJ...771..111S 2013ApJ...771..111S, Cat. J/ApJ/771/111;
Cieslinski et al. 2013IBVS.6088....1C 2013IBVS.6088....1C;
LMC = Reid et al. 2012MNRAS.425..355R 2012MNRAS.425..355R, Cat. J/MNRAS/425/355;
Cieslinski et al. 2013IBVS.6088....1C 2013IBVS.6088....1C;
Paul et al. 2012MNRAS.421.3622P 2012MNRAS.421.3622P, Cat. J/MNRAS/421/3622;
Despite these stars are called Be stars in those works, they are
in many cases BEL stars at the time of observations and not
necessarily CBe.
Note (G7): We crossmatched our clean lists of LMC 2393 and 1004 SMC Be
candidates with the IRSF catalogue by Kato et al.
(2007PASJ...59..615K 2007PASJ...59..615K, Cat. II/288). We found that true matches have
angular distances distributed below 0.4 arcsec, a rather small
distance, within which 1521 stars (64 per cent of the LMC sample)
and 737 stars (73 per cent of the SMC sample) were matched between
these catalogues.
Note (G8): We crossmatched our clean lists of LMC 2393 and 1004 SMC Be
candidates with the SAGE IRAC catalogues for the LMC by
Meixner et al. (2006AJ....132.2268M 2006AJ....132.2268M, Cat. II/305) and for SMC by
Gordon et al. (2011AJ....142..102G 2011AJ....142..102G, Cat. II/305). Results are 1882
stars in the LMC (79 per cent of the sample) and 869 stars in the SMC
(87 per cent of the sample). Not unexpectedly, some stars are missing
either near-IR or mid-IR photometry or both.
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 17-Jun-2024