J/AJ/155/207 Properties of yellow supergiant stars in the SMC (Neugent+, 2018)
A runaway yellow supergiant star in the Small Magellanic Cloud.
Neugent K.F., Massey P., Morrell N.I., Skiff B., Georgy C.
<Astron. J., 155, 207 (2018)>
=2018AJ....155..207N 2018AJ....155..207N (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, supergiant ; Photometry, infrared ;
Photometry, UBV ; Radial velocities ; Spectral types ;
Spectra, optical
Keywords: galaxies: individual (SMC) - Local Group - Magellanic Clouds -
supergiants
Abstract:
We recently discovered a yellow supergiant (YSG) in the Small Magellanic
Cloud (SMC) with a heliocentric radial velocity of ∼300 km/s, which is
much larger than expected for a star at its location in the SMC. This
is the first runaway YSG ever discovered and only the second evolved
runaway star discovered in a galaxy other than the Milky Way. We classify
the star as G5-8 I and use de-reddened broad-band colors with model
atmospheres to determine an effective temperature of 4700±250 K,
consistent with what is expected from its spectral type. The star's
luminosity is then log L/L☉∼4.2∼0.1, consistent with it being a
∼30 Myr 9 M☉ star according to the Geneva evolution models. The
star is currently located in the outer portion of the SMC's body, but
if the star's transverse peculiar velocity is similar to its peculiar
radial velocity, in 10 Myr the star would have moved 1.6° across
the disk of the SMC and could easily have been born in one of the
SMC's star-forming regions. Based on its large radial velocity, we
suggest it originated in a binary system where the primary exploded as
a supernovae, thus flinging the runaway star out into space. Such
stars may provide an important mechanism for the dispersal of heavier
elements in galaxies given the large percentage of massive stars that
are runaways. In the future, we hope to look into additional evolved
runaway stars that were discovered as part of our other past surveys.
Description:
Our first (discovery) spectrum was obtained using Hydra on the CTIO 4 m
Blanco telescope on (UT) 2009 October 9. The second spectrum was obtained
on (UT) 2017 August 16 using the Echelle on the duPont 2.1 m telescope
on Las Campanas in Chile. The spectrum was under-exposed in the blue,
as our goal was simply to check on the radial velocity from the Ca II
triplet in the far red. Subsequently (2017 December 31), we obtained a
high signal-to-noise spectrum with MagE on the Las Campanas Baade 6.5 m
Magellan telescope for the purposes of spectral classification and radial
velocity measurement, plus a shorter exposure the following night simply
to confirm the radial velocity.
Objects:
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RA (ICRS) DE Designation(s)
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00 52 38.0 -72 48 01 Small Magellanic Cloud = NAME SMC
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 131 493 Properties of observed targets
fig2.dat 47 7 Spectral classification stars and runaway star
spectrum
sp/* . 7 Individual fits spectra
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See also:
III/31 : Michigan catalogue for the HD stars, vol. 1 (Houk+, 1975)
V/13 : Probable Members of the SMC (Azzopardi+ 1975, 1979)
II/236 : UBVR CCD survey of the Magellanic clouds (Massey+, 2002)
J/A+AS/30/261 : UBV and Radial Velocities of SMC Supergiants
(Ardeberg+, 1977)
J/AJ/123/855 : Magellanic Clouds Photometric Survey: the SMC
(Zaritsky+, 2002)
J/AJ/126/2867 : Red supergiants in Magellanic Clouds (Massey+, 2003)
J/MNRAS/353/601 : 2dF survey of the Small Magellanic Cloud (Evans+, 2004)
J/ApJ/719/1784 : Yellow supergiants in the SMC (Neugent+, 2010)
J/ApJ/754/35 : Red supergiant stars in the SMC. II. (Yang+, 2012)
J/A+A/578/A3 : New survey of supergiants in the MCs
(Gonzalez-Fernandez+, 2015)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- 2MASS 2MASS identification (JHHMMSSss+DDMMSSs)
19 A1 --- f_2MASS [a] Flag on 2MASS (1)
21- 21 I1 h RAh Hour of Right Ascension (J2000)
23- 24 I2 min RAm Minute of Right Ascension (J2000)
26- 30 F5.2 s RAs Second of Right Ascension (J2000)
32 A1 --- DE- Sign of the Declination (J2000)
33- 34 I2 deg DEd Degree of Declination (J2000)
36- 37 I2 arcmin DEm Arcminute of Declination (J2000)
39- 42 F4.1 arcsec DEs Arcsecond of Declination (J2000)
44- 48 F5.2 mag Ksmag [5.51/12.89] 2MASS KS band magnitude
50- 53 F4.2 mag J-Ks [0/0.92] The (J-KS) color
55- 59 F5.2 mag Vmag [8.42/14.11]? V band magnitude
61- 65 F5.2 mag B-V [-0.07/1.78]? The (B-V) color
67 I1 --- PRef [1/5] The Vmag and B-V photometry reference (2)
69- 74 F6.2 km/s HRV [-97.46/296.1] Heliocentric radial velocity (3)
76- 80 F5.1 --- r [13.1/158.7] r parameter from Tondry & Davis
(1979AJ.....84.1511T 1979AJ.....84.1511T)
82 I1 --- Cat [1/3] Category (4)
84- 92 A9 --- SpTypeH Spectral classification from Hydra spectra
94-102 A9 --- SpTypeL Literature spectral classification (3)
104-105 I2 --- r_SpTypeL [1/28]? Spectral classification reference (5)
107-131 A25 --- Com Additional comments (6)
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Note (1): Flag as follows:
a = These stars were imaged twice and their results were averaged. The
average difference in Velobs was 2.2 km/s and the average difference
in the r parameter was 13.7.
Note (2): The Vmag and B-V photometry reference as follows:
1 = Massey (2002, Cat. II/236);
2 = Mermilliod (1997A&AS..124..349M 1997A&AS..124..349M);
3 = ASAS-3; Pojmanski (1997AcA....47..467P 1997AcA....47..467P);
4 = Zaritsky (2002, J/AJ/123/855);
5 = (Zaritsky B) - (ASAS-3 V).
Note (3): This table is a re-issue of Table 1 from Neugent et al. (2010,
J/ApJ/719/1784) with corrected heliocentric radial velocities and subsequently
revised spectral types from Gonzalez-Fernandez et al. (2015, J/A+A/578/A3).
Note (4): Category as follows:
1 = SMC supergiant;
2 = Possible SMC supergiant;
3 = Foreground dwarf.
Note (5): Spectral classification reference as follows:
1 = Cannon & Pickering (1918AnHar..91....1C 1918AnHar..91....1C);
2 = Massey & Olsen (2003, J/AJ/126/2867);
3 = Evans et al. (2004, J/MNRAS/353/601);
4 = Sanduleak (1969AJ.....74..877S 1969AJ.....74..877S);
5 = Lu (1971TOYal..31....1L 1971TOYal..31....1L);
6 = Florsch (1972POStr...2....1F 1972POStr...2....1F);
7 = Lennon (1997A&A...317..871L 1997A&A...317..871L);
8 = Azzopardi et al. (1975, Cat. V/13);
9 = Houk & Cowley (1975, J/A+AS/30/261);
10 = Ardeberg & Maurice (1977, J/A+AS/30/261);
11 = Azzopardi & Vigneau (1979A&AS...35..353A 1979A&AS...35..353A);
12 = Gonzalez-Fernandez et al. (2015, J/A+A/578/A3);
13 = Humphreys (1983ApJ...265..176H 1983ApJ...265..176H);
14 = Humphreys et al. (1991A&A...245..593H 1991A&A...245..593H);
15 = Wallerstein (1984AJ.....89.1705W 1984AJ.....89.1705W);
16 = Bouchet et al. (1985A&A...149..330B 1985A&A...149..330B);
17 = Carney et al. (1985AJ.....90.1196C 1985AJ.....90.1196C);
19 = Houk & Cowley (1975, Cat. III/31);
22 = Gonzalez-Fernandez et al. (2015, J/A+A/578/A3);
28 = Neugent et al. (2010, J/ApJ/719/1784).
Note (6): Comments include: alternate names for the star, comments on the blue
spectra and comments based on the literature search.
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Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Star Star name (1)
19- 24 A6 --- SpType Spectral type (from Table 2 of this paper)
26- 47 A22 --- FileName Name of FITS file, in subdirectory sp
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Note (1): The stars shown are the spectral standards along with our yellow
supergiant (YSG) runaway, J01020100-7122208.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 10-Dec-2018