J/A+A/635/A33 Galactic classical Cepheids Per-Lbol-Rad (Groenewegen, 2020)
Analysing the spectral energy distributions of Galactic classical Cepheids.
Groenewegen M.A.T
<Astron. Astrophys. 635, A33 (2020)>
=2020A&A...635A..33G 2020A&A...635A..33G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, distances ; Parallaxes, trigonometric
Keywords: stars: distances - stars: variables: Cepheids - parallaxes
Abstract:
Spectral energy distributions (SEDs) were constructed for a sample of
477 classical cepheids (CCs); including stars that have been
classified in the literature as such but are probably not. The SEDs
were fitted with a dust radiative transfer code. Four stars showed a
large mid- or far-infrared excess and the fitting then included a dust
component. These comprise the well-known case of RS Pup, and three
stars that are (likely) Type-II cepheids (T2Cs), AU Peg, QQ Per, and
FQ Lac. The infrared (IR) excess in FQ Lac is reported for the first
time in this work.
The remainder of the sample was fitted with a stellar photosphere to
derive the best-fitting luminosity and effective temperature. Distance
and reddening were taken from the literature. The stars were plotted
in a Hertzsprung-Russell diagram (HRD) and compared to evolutionary
tracks for cepheids and theoretical instability strips. For the large
majority of stars, the position in the HRD is consistent with the
instability strip for a CC or T2C. About 5% of the stars are outliers
in the sense that they are much hotter or cooler than expected. A
comparison to effective temperatures derived from spectroscopy
suggests in some cases that the photometrically derived temperature is
not correct and that this is likely linked to an incorrectly adopted
reddening.
Two three-dimensional reddening models have been used to derive
alternative estimates of the reddening for the sample. There are
significant systematic differences between the two estimates with a
non-negligible scatter.
In this work the presence of a small near-infrared (NIR) excess, as
has been proposed in the literature for a few well-known cepheids, is
investigated. Firstly, this was done by using a sample of about a
dozen stars for which a mid-infrared spectrum is available. This data
is particularly con straining as the shape of the observed spectrum
should match that of the photosphere and any dust spectrum, both dust
continuum and any spectral features of, for example, silicates or
aluminium oxide. This comparison provides constraints on the dust
composition, in agreement with a previous work in the literature.
Secondly, the SEDs of all stars were fitted with a dust model to see
if a statistically significant better fit could be obtained. The
results were compared to recent work. Eight new candidates for
exhibiting a NIR excess are proposed, solely based on the photometric
SEDs. Obtaining mid-infrared spectra would be needed to confirm this
excess. Finally, period-bolometric luminosity and period-radius
relations are presented for samples of over 370 fundamental-mode CCs.
Description:
The tabular material describes the basic parameters for the sample of
stars (Table1) and compiles alternative reddening values (TableA1) for
the entire sample except the five Cepheids in the inner disk.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 182 477 Sample of stars
tablea1.dat 77 472 Different reddening values
refer.dat 50 13 References for angular diameters
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name The variable star name
16- 23 A8 --- Type1 The classification of the variability
25- 31 A7 --- Type2 An alternative classification of the
variability (1)
33- 38 F6.3 d Period ? The pulsation period
40- 43 F4.2 mag E(B-V) The reddening
45- 48 F4.2 mag e_E(B-V) The reddening error
50- 55 F6.3 kpc dist The distance (2)
57- 58 I2 - r_dist Reference (2)
60- 65 F6.3 kpc e_dist The error in the distance
71- 76 F6.3 kpc dist2 ? An alternative distance with error bars (3)
78- 82 F5.3 kpc E_dist2 ? An alternative distance with error bars (3)
84- 88 F5.3 kpc e_dist2 ? An alternative distance with error bars (3)
90- 97 F8.1 Lsun Lum The stellar luminosity with error bar
99-105 F7.1 Lsun e_Lum The stellar luminosity with error bar
107-110 I4 K Teff The effective temperature
112-114 I3 K e_Teff The effective temperature
116-120 F5.3 mas theta The predicted angular diameter
122-126 F5.3 mas e_theta The predicted angular diameter
128-182 A55 --- Remarks Angular diameters from the literature
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Note (1): The classification by Ripepi et al. (2019, Cat. J/A+A/625/A14).
Multimode cepheids are labelled with "_MU".
Note (2): Adopted distance, with references as follows:
1 = parallax from Gaia Collaboration et al. (2018, Cat. I/345) with
additional criteria and a parallax zeropoint offset applied
(see main text),
2 = parallax from van Leeuwen (2008, Cat. I/311)
3 = parallax from van Leeuwen et al. (2007MNRAS.379..723V 2007MNRAS.379..723V)
4 = parallax from Benedict et al. (2007AJ....133.1810B 2007AJ....133.1810B)
5 = parallax from Riess et al. (2014ApJ...785..161R 2014ApJ...785..161R)
6 = parallax from Riess et al. (2018ApJ...855..136R 2018ApJ...855..136R)
For references 1-6 the distance is taken as 1/parallax.
7 = Gallenne et al. (2018ApJ...867..121G 2018ApJ...867..121G)
8 = Inno et al. (2019MNRAS.482...83I 2019MNRAS.482...83I)
9 = Melnik et al. (2015, Cat. J/AN/336/70)
10 = Acharova et al. (2012, Cat. J/MNRAS/420/1590)
11 = Genovali et al. (2014, Cat. J/A+A/566/A37)
12 = Kashuba et al. (2016, Cat. J/MNRAS/461/839)
13 = Andrievsky et al. (2016MNRAS.461.4256A 2016MNRAS.461.4256A)
14 = Martin et al. (2015MNRAS.449.4071M 2015MNRAS.449.4071M)
15 = Luck (2018, Cat. J/AJ/156/171)
16 = Luck (2014, Cat. J/AJ/147/137)
Note (3): Distance with error bar as given by Bailer-Jones et al.
(2018AJ....156...58B 2018AJ....156...58B, Cat. I/347).
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name The variable star name
16- 20 F5.3 mag E(B-V)1 The adopted reddening (1)
22- 26 F5.3 mag e_E(B-V)1 The error in the adopted reddening (1)
28- 32 F5.3 mag E(B-V)2 ? An alternative reddening (2)
34- 38 F5.3 mag e_E(B-V)2 ? The error in the reddening E(B-V)2 (2)
40- 44 F5.3 mag E(B-V)3a An alternative reddening (3)
46- 50 F5.3 mag E(B-V)3b An alternative reddening (3)
52- 56 F5.3 mag e_E(B-V)3a The error in the reddening E(B-V)3a
and E(B-V)3b (3)
58- 62 F5.3 mag E(B-V)4 ? An alternative reddening (4)
64- 68 F5.3 mag e_E(B-V)4 ? The error in the reddening E(B-V)4 (4)
70- 77 A8 --- Remarks Remarks (5)
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Note (1): The adopted reddening and error, repeated from Table 1.
Note (2): The reddening and error from Trahin (2019, PhD thesis,
L'Universite PSL, l'Observatoire de Paris).
Note (3): The results from the 3D model by Lallement et al.
(2018A&A...616A.132L 2018A&A...616A.132L).
E(B-V)3a is the reddening in the available grid at the distance closest
to distance of the object.
E(B-V)3b is the reddening at the distance of the object, based on the
extrapolation explained in the main text.
Note (4): The reddening from the 3D model by Green et al.
(2019ApJ...887...93G 2019ApJ...887...93G).
Note (5): The remark indicates if a star is an outlier in the HRD (Fig. 2,
labelled as HRD) or in the comparison with the spectroscopic temperature
determinations (Fig. 4, labelled as TEF).
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Byte-by-byte Description of file: refer.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Ref Reference code
5- 50 A46 --- Com Comments
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Acknowledgements:
Martin Groenewegen, martin.groenewegen(at)oma.be
(End) Patricia Vannier [CDS] 31-Jan-2020