Physical parameters of the Small Magellanic Cloud RR Lyrae stars and the distance scale

Deb, Sukanta; Singh, Harinder P.

doi:10.1111/j.1365-2966.2009.15927.x

Cited by 31 publications

(29 citation statements)

References 52 publications

(93 reference statements)

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“…All the Fourier components tend to be clustered in a limited region in this space (for reference see Fig. 6 of Deb & Singh 2010). There were some outliers in the distributions (e.g.…”

Section: Resultsmentioning

confidence: 99%

Mapping the outer bulge with RRab stars from the VVV Survey

Gran

Minniti

Saito

et al. 2016

A&A

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Context. The VISTA Variables in the Vía Láctea (VVV) is a near-IR time-domain survey of the Galactic bulge and southern plane. One of the main goals of this survey is to reveal the 3D structure of the Milky Way through their variable stars. In particular, enormous numbers of RR Lyrae stars have been discovered in the inner regions of the bulge (−8• ) by optical surveys such as OGLE and MACHO, but leaving an unexplored window of more than ∼47 sq deg (−10.0• and −10.3• b −8.0 • ) observed by the VVV Survey. Aims. Our goal is to characterize the RR Lyrae stars in the outer bulge in terms of their periods, amplitudes, Fourier coefficients, and distances in order to evaluate the 3D structure of the bulge in this area. The distance distribution of RR Lyrae stars will be compared to that of red clump stars, which is known to trace a X-shaped structure, in order to determine whether these two different stellar populations share the same Galactic distribution. Methods. A search for RR Lyrae stars was performed in more than ∼47 sq deg at low Galactic latitudes (−10.3• ). In the procedure the χ 2 value and analysis of variance (AoV) statistic methods were used to determine the variability and periodic features of the light curves, respectively. To prevent misclassifications, the analysis was performed only on the fundamental mode RR Lyrae stars (RRab) owing to similarities found in the near-IR light curve shapes of contact eclipsing binaries (W UMa) and first overtone RR Lyrae stars (RRc). On the other hand, the red clump stars of the same analyzed tiles were selected, and cuts in the color-magnitude diagram were applied and the maximum distance restricted to ∼20 kpc in order to construct a similar catalog in terms of distances and covered area compared to the RR Lyrae stars. Results. We report the detection of more than 1000 RR Lyrae ab-type stars in the VVV Survey located in the outskirts of the Galactic bulge. A few of them are possibly associated with the Sagittarius Dwarf Spheroidal Galaxy. We calculated colours, reddening, extinction, and distances of the detected RR Lyrae stars in order to determine the outer bulge 3D structure. Our main result is that, at the low galactic latitudes mapped here, the RR Lyrae stars trace a centrally concentrated spheroidal distribution. This is a noticeably different spatial distribution to the one traced by red clump stars known to follow a bar and X-shaped structure. We estimate the completeness of our sample at 80% for K s ≤ 15 mag.

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“…All the Fourier components tend to be clustered in a limited region in this space (for reference see Fig. 6 of Deb & Singh 2010). There were some outliers in the distributions (e.g.…”

Section: Resultsmentioning

confidence: 99%

Mapping the outer bulge with RRab stars from the VVV Survey

Gran

Minniti

Saito

et al. 2016

A&A

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“…It should be noted that some authors (e.g. Deb & Singh , hereinafter DS10; Haschke et al , hereinafter HGDJ) have used I ‐band data to derive metal abundances and physical parameters of RR Lyrae stars. As thoroughly discussed in Paper I, although the I ‐band light curves may produce similar average metallicities to those derived from the V ‐band light curves, discrepancies are revealed in metallicities of individual stars and their distributions.…”

Section: Data Analysis and Fourier Decompositionmentioning

confidence: 99%

RR Lyrae variables in the Small Magellanic Cloud - II. The extended area: chemical and structural analysis

Kapakos

Hatzidimitriou

2012

Monthly Notices of the Royal Astronomical Society

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We have performed the Fourier decomposition analysis of 8‐ and 13‐yr V‐band light curves of a carefully selected sample of 454 fundamental‐mode RR Lyrae variables (RRab type), detected in an ≃14 square degree area of the Small Magellanic Cloud (SMC) and listed in the Optical Gravitational Lensing Experiment, phase III, Catalogue of Variable Stars. The Fourier decomposition parameters were used to derive metal abundances and distance moduli, following the methodology described by Kapakos, Hatzidimitriou & Soszyński. The average metal abundance of the RRab stars on the new scale of Carretta et al. was found to be 〈[Fe/H]C09〉 = −1.69 ± 0.41 dex (std, with a standard error of 0.02 dex). A tentative metallicity gradient of −0.013 ± 0.007 dex kpc−1 was detected, with increasing metal abundance towards the dynamical centre of the SMC, but selection effects are also discussed. The distance modulus of the SMC was re‐estimated and was found to be 〈μ〉 = 19.13 ± 0.19 (std) in a distance scale where the distance modulus of the Large Magellanic Cloud (LMC) is μLMC = 18.52 ± 0.06 (std). The average 1σ line‐of‐sight depth was found to be σ int =5.3±0.4 kpc (std), while spatial variations of the depth were detected. The SMC was found to be deeper in the north‐eastern region, while metal‐richer and metal‐poorer objects in the sample seem to belong to different dynamical structures. The former have smaller scale height and may constitute a thick disc, its width being 10.40 ± 0.02 kpc, and a bulge whose size (radius) is estimated to be 2.09 ± 0.81 kpc. The latter seem to belong to a halo structure with a maximum depth along the line of sight extending over 16 kpc in the SMC central region and falling to ∼12 kpc in the outer regions.

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“…Here we aim to investigate the massive star population of the young open star cluster NGC 330. This cluster is situated in the Small Magellanic Cloud (SMC) at a distance of 60 ± 1 kpc (Har-ries et al 2003;Hilditch et al 2005;Deb & Singh 2010). Age estimates of NGC 330 vary between 26 and 45 Myrs, thus putting it in the age range of interest for our purposes (Sirianni et al 2002;Martayan et al 2007b;Milone et al 2018, Patrick et al, subm.).…”

Section: Introductionmentioning

confidence: 99%

The young massive SMC cluster NGC 330 seen by MUSE

Bodensteiner

Sana

Mahy

et al. 2020

A&A

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Context. A majority of massive stars are part of binary systems, a large fraction of which will inevitably interact during their lives. Binary-interaction products (BiPs), i.e. stars affected by such interaction, are expected to be commonly present in stellar populations. BiPs are thus a crucial ingredient in the understanding of stellar evolution. Aims. We aim to identify and characterize a statistically significant sample of BiPs by studying clusters of 10 − 40 Myr, an age at which binary population models predict the abundance of BiPs to be highest. One example of such a cluster is NGC 330 in the Small Magellanic Cloud. Methods. Using MUSE WFM-AO observations of NGC 330, we resolve the dense cluster core for the first time and are able to extract spectra of its entire massive star population. We develop an automated spectral classification scheme based on the equivalent widths of spectral lines in the red part of the spectrum. Results. We characterize the massive star content of the core of NGC 330 which contains more than 200 B stars, two O stars, 6 A-type supergiants and 11 red supergiants. We find a lower limit on the Be star fraction of 32 ± 3% in the whole sample. It increases to at least 46 ± 10% when only considering stars brighter than V = 17 mag. We estimate an age of the cluster core between 35 and 40 Myr and a total cluster mass of 88 +17 −18 × 10 3 M . Conclusions. We find that the population in the cluster core is different than the population in the outskirts: while the stellar content in the core appears to be older than the stars in the outskirts, the Be star fraction and the observed binary fraction are significantly higher. Furthermore, we detect several BiP candidates that will be subject of future studies.

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Physical parameters of the Small Magellanic Cloud RR Lyrae stars and the distance scale

Cited by 31 publications

References 52 publications

Mapping the outer bulge with RRab stars from the VVV Survey

Mapping the outer bulge with RRab stars from the VVV Survey

RR Lyrae variables in the Small Magellanic Cloud - II. The extended area: chemical and structural analysis

The young massive SMC cluster NGC 330 seen by MUSE

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