J/MNRAS/488/3211 Two new Galactic lithium-rich Cepheids (Kovtyukh+, 2019)
The MAGIC project - II. Discovery of two new Galactic lithium-rich Cepheids.
Kovtyukh V., Lemasle B., Kniazev A., Berdnikov L., Bono G., Usenko I.,
Grebel E.K., Hajdu G., Pastukhova E.
<Mon. Not. R. Astron. Soc., 488, 3211-3221 (2019)>
=2019MNRAS.488.3211K 2019MNRAS.488.3211K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, distances ; Effective temperatures ;
Radial velocities ; Abundances ; Spectra, optical
Keywords: stars: abundances - stars: variables: Cepheids
Abstract:
We report the discovery of two new lithium-rich Cepheids in the Milky
Way (A(Li)∼2.9dex) among the targets of the MAGIC spectroscopic survey
with the Southern African Large Telescope spectrographs. The 6707Å
Li feature is usually not detectable in the atmosphere of Cepheids.
Only three Cepheids (two in the Milky Way and one in the Large
Magellanic Cloud) had been reported so far with high lithium
abundances. We examine the possibility that the Li-rich Cepheids are
evolving towards the red giant branch, crossing the instability strip
for the first time, as well as other possible scenarios. The two stars
are mixed-mode Cepheids pulsating simultaneously in the first and in
the second overtone modes. We briefly discuss the possible connection
between their unusual chemical composition and their pulsational
properties.
Description:
Our stars were observed with SALT on 2016 May 20 (ASAS J075842-2536.1)
and on 2016 May 21 (ASAS J131714-6605.0) with the high-resolution
echelle spectrograph (HRS) in single exposures of 2600s and 2672s,
respectively, with a seeing of ∼1.8arcsec. HRS is a dual beam,
fibre-fed echelle spectrograph (Barnes et al. 2008SPIE.7014E..0KB;
Bramall et al. 2010SPIE.7735E..4FB, 2012SPIE.8446E..0AB; Crause et al.
2014SPIE.9147E..6TC). In our observations, HRS was used in the
medium-resolution mode (MR; R∼37000-39000) and with a 2.23arcsec
diameter for both the object and sky fibres to provide a spectrum in
the blue and red arms over the total spectral range of ∼3900-8900Å.
The two previously known Li-rich Cepheids were studied with spectra
collected with the HERMES spectrograph (Raskin et al.
2011A&A...526A..69R 2011A&A...526A..69R) in the case of V371 Per and with the Espadons
spectrograph in the case of V1033 Cyg. HERMES is an echelle
spectrograph at the 1.2m Mercator telescope on la Palma. Our spectrum
of V371 Per has a resolution of R=85000 and covers the 3800-8350Å
wavelength range. Espadons is an echelle spectrograph at the
Canada-France-Hawaii Telescope (CFHT, Donati et al.
2003ASPC..307...41D 2003ASPC..307...41D). Our spectrum of V1033 Cyg has a resolution of
80000 and covers the wavelength range 3700-10500Å. The observing
log is given in Table 2.
Objects:
------------------------------------------------------------------------
RA (ICRS) DE Designation(s)
------------------------------------------------------------------------
07 58 42.16 -25 36 00.9 ASAS J075842-2536.1 = 2MASS J07584216-2536009
13 17 13.77 -66 04 59.4 ASAS J131714-6605.0 = 2MASS J13171376-6604595
02 55 31.18 +42 35 19.7 V371 Per = 2MASS J02553118+4235197
20 05 20.66 +32 39 32.8 V1033 Cyg = 2MASS J20052066+3239327
------------------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 75 4 Parameters of the lithium-rich Cepheids
table2.dat 70 5 Observations and atmospheric parameters of the
lithium-rich Cepheids
table4.dat 112 4 LTE abundances in lithium-rich Cepheids
table6.dat 89 4 Abundance ratios in lithium-rich Cepheids
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- Name Cepheid name
20- 27 A8 --- Type Cepheid type
29- 33 A5 --- Mode Pulsating modes
35- 43 F9.7 d Pobs Period of pulsation
45- 50 F6.3 mag Vmag V magnitude
52- 56 F5.2 kpc RG Galactocentric distance
58- 61 I4 pc Dist Distance
63- 68 F6.2 deg GLON Galactic longitude (l)
70- 75 F6.2 deg GLAT Galactic latitude (b)
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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- 18 A18 --- Name Cepheid name
20- 30 F11.5 d MJD Modified Julian Date (JD-2400000)
32- 39 A8 --- Spect Spectrograph (SALT HRS, HERMES or CFHT)
41 I1 --- Ref Reference for data (1)
43- 45 I3 --- S/N Signal to noise ratio
47- 50 I4 K Teff Effective temperature
52- 54 F3.1 [cm/s2] logg Surface gravity
56- 58 F3.1 km/s Vt Micro-turbulence velocity
60- 64 F5.2 [-] [Fe/H] Iron to hydrogen abundance ratio
66- 70 F5.1 km/s RV Radial velocity
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Note (1): References as follows:
1 = This paper
2 = Kovtyukh et al. (2016MNRAS.460.2077K 2016MNRAS.460.2077K)
3 = Martin et al. (2015MNRAS.449.4071M 2015MNRAS.449.4071M)
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- Name Cepheid name
20- 24 F5.2 [-] [FeI/H] FeI to hydrogen abundance ratio
26- 29 F4.2 [-] e_[FeI/H] Error on [FeI/H]
31- 33 I3 --- o_[FeI/H] Number of lines used to obtain [FeI/H]
35- 39 F5.2 [-] [FeII/H] FeII to hydrogen abundance ratio
41- 44 F4.2 [-] e_[FeII/H] Error on [FeII/H]
46- 47 I2 --- o_[FeII/H] Number of lines used to obtain [FeII/H]
49- 52 F4.2 [-] A(Li) Lithium abundance
54- 57 F4.2 [-] e_A(Li) Error on A(Li)
59 I1 --- o_A(Li) Number of lines used to obtain A(Li)
61- 65 F5.2 [-] [C/H] Carbon to hydrogen abundance ratio
67- 70 F4.2 [-] e_[C/H] Error on [C/H]
72- 73 I2 --- o_[C/H] Number of lines used to obtain [C/H]
75- 79 F5.2 [-] [N/H] Nitrogen to hydrogen abundance ratio
81- 84 F4.2 [-] e_[N/H] Error on [N/H]
86 I1 --- o_[N/H] Number of lines used to obtain [N/H]
88- 92 F5.2 [-] [O/H] Oxygen to hydrogen abundance ratio
94- 97 F4.2 [-] e_[O/H] ? Error on [O/H]
99 I1 --- o_[O/H] Number of lines used to obtain [O/H]
101-105 F5.2 [-] [Na/H] Sodium to hydrogen abundance ratio
107-110 F4.2 [-] e_[Na/H] Error on [Na/H]
112 I1 --- o_[Na/H] Number of lines used to obtain [Na/H]
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- Name Cepheid name
20- 23 F4.2 [-] A(Li) Lithium abundance
25- 29 F5.2 [-] [Fe/H] Iron to hydrogen abundance ratio
31- 35 F5.2 [-] [C/H] Carbon to hydrogen abundance ratio
37- 41 F5.2 [-] [N/H] Nitrogen to hydrogen abundance ratio
43- 47 F5.2 [-] [O/H] Oxygen to hydrogen abundance ratio
49- 53 F5.2 [-] [Na/H] Sodium to hydrogen abundance ratio
55- 59 F5.2 [-] [C/Fe] Carbon to iron abundance ratio
61- 65 F5.2 [-] [N/Fe] Nitrogen to iron abundance ratio
67- 71 F5.2 [-] [O/Fe] Oxygen to iron abundance ratio
73- 77 F5.2 [-] [Na/Fe] Sodium to iron abundance ratio
79- 83 F5.2 [-] [C/O] Carbon to oxygen abundance ratio
85- 89 F5.2 [-] [N/C] Nitrogen to carbon abundance ratio
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History:
From electronic version of the journal
References:
Kniazev et al., Paper I 2019AstBu..74..208K 2019AstBu..74..208K
(End) Ana Fiallos [CDS] 13-Dec-2022