J/A+A/620/A99 SMC Cepheids K-band and RV curves (Gieren+, 2018)
The effect of metallicity on Cepheid period-luminosity relations from a
Baade-Wesselink analysis of Cepheids in the Milky Way and Magellanic Clouds.
Gieren W., Storm J., Konorski P., Gorski M., Pilecki B., Thompson I.,
Pietrzynski G., Graczyk D., Barnes T.G., Fouque P., Nardetto N.,
Gallenne A., Karczmarek P., Suchomska K., Wielgorski P., Taormina M.,
Zgirski B.
<Astron. Astrophys. 620, A99 (2018)>
=2018A&A...620A..99G 2018A&A...620A..99G (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, variable ; Photometry ;
Radial velocities
Keywords: stars: variables: Cepheids - stars: distances -
stars: fundamental parameters - Magellanic Clouds -
galaxies: distances and redshifts
Abstract:
The extragalactic distance scale builds on the Cepheid
period-luminosity (PL) relation. Decades of work have not yet
convincingly established the sensitivity of the PL relation to
metallicity. This currently prevents a determination of the Hubble
constant accurate to 1% from the classical Cepheid-SN Ia method.
In this paper we carry out a strictly differential comparison of the
absolute PL relations obeyed by classical Cepheids in the Milky Way
(MW), LMC, and SMC galaxies. Taking advantage of the substantial
metallicity difference among the Cepheid populations in these three
galaxies, we want to establish a possible systematic trend of the PL
relation absolute zero point as a function of metallicity, and to
determine the size of such an effect in the optical and near-infrared
photometric bands.
We used a IRSB Baade-Wesselink-type method to determine individual
distances to the Cepheids in our samples in the MW, LMC, and SMC. For
our analysis, we used a greatly enhanced sample of Cepheids in the SMC
(31 stars) compared to the small sample (5 stars) available in our
previous work. We used the distances to determine absolute Cepheid PL
relations in the optical and near-infrared bands in each of the three
galaxies.
Our distance analysis of 31 SMC Cepheids with periods of 4-69 days
yields tight PL relations in all studied bands, with slopes consistent
with the corresponding LMC and MW relations. Adopting the very
accurately determined LMC slopes for the optical and near-infrared
bands, we determine the zero point offsets between the corresponding
absolute PL relations in the three galaxies.
We find that in all bands the metal-poor SMC Cepheids are
intrinsically fainter than their more metal-rich counterparts in the
LMC and MW. In the K band the metallicity effect is
-0.23±0.06mag/dex, while in the V,(V-I) Wesenheit index it is
slightly stronger, -0.34±0.06mag/dex. We find suggestive evidence
that the metallicity sensitivity of the PL relation might be
nonlinear, being small in the range between solar and LMC Cepheid
metallicity, and becoming steeper towards the lower-metallicity
regime.
Description:
We have selected a sample of 26 classical Cepheids in the Small
Magellanic Cloud from the OGLE catalogue. They are OGLE-SMC-CEP-0320,
0518, 0524, 0958, 1365, 1385, 1403, 1410, 1680, 1686, 1693, 1712,
1717, 1723, 1729, 1750, 1761, 1765, 1797, 1977, 2533, 2905, 3311,
3927, 4017, 4444.
For these stars we present K-band light curves on the UKIRT system
(table2.dat) as well as radial velocity curves (table4.dat). For five
stars, OGLE-SMC_CEP-1680, 1729, 1977, 2905, & 2470 (HV837) it was
necessary to remove orbital motion from the radial velocities before
proceeding to determine pulsational velocities. The corrected radial
velocities as well as the applied corrections are given in
tableb1.dat.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 59 30 List of studied stars
table2.dat 44 754 K-band light curve data
table4.dat 54 714 Radial velocity data
tableb1.dat 63 156 Radial velocity data corrected for orbital motion
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See also:
J/AcA/65/297 : OGLE4 LMC and SMC Cepheids (Soszynski+, 2015)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- ID OGLE identifier
19- 20 I2 h RAh Simbad right ascension (J2000)
22- 23 I2 min RAm Simbad right ascension (J2000)
25- 29 F5.2 s RAs Simbad right ascension (J2000)
31 A1 --- DE- Declination sign (J2000)
32- 33 I2 deg DEd Declination (J2000)
35- 36 I2 arcmin DEm Declination (J2000)
38- 41 F4.1 arcsec DEs Declination (J2000)
43- 50 F8.6 [d] logP ? logarithm of the period
(from table5 of the paper)
52- 53 I2 --- NT2 ? Number of measurements in table2
55- 56 I2 --- NT4 ? Number of measurements in table4
58- 59 I2 --- NTB1 ? Number of measurements in tableb1
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- ID OGLE identifier
19- 31 F13.5 d HJD Heliocentric Julian Date
33- 38 F6.3 mag Kmag K-band magnitude in UKIRT system
40- 44 F5.3 mag e_Kmag Error estimate on K-band magnitude
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- ID OGLE identifier
19- 31 F13.5 d HJD Heliocentric Julian Date
33- 38 F6.2 km/s RV Radial velocity
41- 44 F4.2 km/s e_RV Error estimate on radial velocity
46- 54 A9 --- Inst Instrument used
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Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- ID OGLE identifier
19- 23 F5.3 --- Phase Pulsation phase
25- 37 F13.5 d HJD Heliocentric Julian Date
39- 44 F6.2 km/s RVobs Observed Radial velocity
47- 50 F4.2 km/s e_RVobs Error estimate on rad. velocity
52- 57 F6.2 km/s RV Corrected radial velocity
60- 63 F4.1 km/s RVoff Radial velocity offset
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Acknowledgements:
Jesper Storm, jstorm(at)aip.de
(End) Jesper Storm [AIP, Germany], Patricia Vannier [CDS] 30-Nov-2018