Anomalous Cepheids discovered in a sample of galactic short period Type II Cepheids
We revisited the short period Type II Cepheids (T2Cs), called the BL Herculis (BLHs), in the Galactic Field to derive a homogeneous analysis of their Fourier parameters. Only V-band data were compiled to make sure that it was directly comparable between the known variables of the OGLE-III catalogue...
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Astronomical Observatory, Department of Astronomy, Belgrade
2018-01-01
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doaj-917d82b5c5ae48ea855f8833c23f7d242020-11-25T02:46:21ZengAstronomical Observatory, Department of Astronomy, BelgradeSerbian Astronomical Journal1450-698X1820-92892018-01-0120181972210.2298/SAJ180316002J1450-698X1800002JAnomalous Cepheids discovered in a sample of galactic short period Type II CepheidsJurković M.I.0Astronomical Observatory, Belgrade + Konkoly Thege Miklós Astronomical Institute, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Budapest, HungaryWe revisited the short period Type II Cepheids (T2Cs), called the BL Herculis (BLHs), in the Galactic Field to derive a homogeneous analysis of their Fourier parameters. Only V-band data were compiled to make sure that it was directly comparable between the known variables of the OGLE-III catalogue and the 59 individual objects classified as short period Type II Cepheids in the General Catalogue of Variable Stars (GCVS) we had in our sample. The derived Fourier parameters were used to make distinction between different classes of variables. From the 59 stars we found 19 BLHs, 19 fundamental mode Anomalous Cepheids (ACs) (8 of them were already known from the Catalina Sky Survey (CSS)), 1 first overtone AC, 2 were found to be possible peculiar W Virginis (pWVir), 11 classical Cepheids (DCEPs), and 7 stars were not pulsating variables at all. As a result we created a list of bright BLH stars in the Galactic Field, and separated the ACs, as well as other objects that were misclassified. The number of true BLHs decreased in our sample by more than 50%. We gathered the metallicity from spectroscopic measurements published in literature. While the number of actual measurements is low, it is highly suggestive that ACs are metal poor. The mean metallicity from 8 measurements in 4 stars (UY Eri having 5 different [Fe/H] data points) is -1.12 dex, but if the higher value metallicity outliers of UY Eri are left out the mean metallicity becomes -1.88 dex, regardless if the AC is in the Milky Way itself or in a cluster. On the other hand, BLHs seem to have a Solar-like metallicity of 0.00 dex averaged from 21 measurements of 10 stars. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 176004]http://www.doiserbia.nb.rs/img/doi/1450-698X/2018/1450-698X1800002J.pdfStars: variables: CepheidsStars: Population II |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Jurković M.I. |
spellingShingle |
Jurković M.I. Anomalous Cepheids discovered in a sample of galactic short period Type II Cepheids Serbian Astronomical Journal Stars: variables: Cepheids Stars: Population II |
author_facet |
Jurković M.I. |
author_sort |
Jurković M.I. |
title |
Anomalous Cepheids discovered in a sample of galactic short period Type II Cepheids |
title_short |
Anomalous Cepheids discovered in a sample of galactic short period Type II Cepheids |
title_full |
Anomalous Cepheids discovered in a sample of galactic short period Type II Cepheids |
title_fullStr |
Anomalous Cepheids discovered in a sample of galactic short period Type II Cepheids |
title_full_unstemmed |
Anomalous Cepheids discovered in a sample of galactic short period Type II Cepheids |
title_sort |
anomalous cepheids discovered in a sample of galactic short period type ii cepheids |
publisher |
Astronomical Observatory, Department of Astronomy, Belgrade |
series |
Serbian Astronomical Journal |
issn |
1450-698X 1820-9289 |
publishDate |
2018-01-01 |
description |
We revisited the short period Type II Cepheids (T2Cs), called the BL Herculis (BLHs), in the Galactic Field to derive a homogeneous analysis of their Fourier parameters. Only V-band data were compiled to make sure that it was directly comparable between the known variables of the OGLE-III catalogue and the 59 individual objects classified as short period Type II Cepheids in the General Catalogue of Variable Stars (GCVS) we had in our sample. The derived Fourier parameters were used to make distinction between different classes of variables. From the 59 stars we found 19 BLHs, 19 fundamental mode Anomalous Cepheids (ACs) (8 of them were already known from the Catalina Sky Survey (CSS)), 1 first overtone AC, 2 were found to be possible peculiar W Virginis (pWVir), 11 classical Cepheids (DCEPs), and 7 stars were not pulsating variables at all. As a result we created a list of bright BLH stars in the Galactic Field, and separated the ACs, as well as other objects that were misclassified. The number of true BLHs decreased in our sample by more than 50%. We gathered the metallicity from spectroscopic measurements published in literature. While the number of actual measurements is low, it is highly suggestive that ACs are metal poor. The mean metallicity from 8 measurements in 4 stars (UY Eri having 5 different [Fe/H] data points) is -1.12 dex, but if the higher value metallicity outliers of UY Eri are left out the mean metallicity becomes -1.88 dex, regardless if the AC is in the Milky Way itself or in a cluster. On the other hand, BLHs seem to have a Solar-like metallicity of 0.00 dex averaged from 21 measurements of 10 stars. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 176004] |
topic |
Stars: variables: Cepheids Stars: Population II |
url |
http://www.doiserbia.nb.rs/img/doi/1450-698X/2018/1450-698X1800002J.pdf |
work_keys_str_mv |
AT jurkovicmi anomalouscepheidsdiscoveredinasampleofgalacticshortperiodtypeiicepheids |
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1724758976473595904 |