Updated census of RR Lyrae stars in the globular cluster<i>ω</i>Centauri (NGC 5139)

Navarrete, C.; Ramos, R. Contreras; Catelan, M.; Clement, Christine M.; Gran, F.; Alonso-García, J.; Angeloni, R.; Hempel, M.; Dékány, I.; Minniti, D.

doi:10.1051/0004-6361/201424838

Cited by 30 publications

(77 citation statements)

References 61 publications

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“…In this diagram we can see that our RR Lyrae stars are predominantly Oosterhoff Type I (OoI) with a minor composition of Oosterhoff Type II (OoII). We derived this composition with the Oosterhoof reference lines traced by Navarrete et al (2015). In addition to the period and amplitude, another characteristic feature of the RRab stars is the light curve shape, which can be described by a Fourier series.…”

Section: Resultsmentioning

confidence: 99%

“…In our catalog there are eight matches within d < 1 in tiles b220 and b221. Three of the five remaining RRab stars were not analyzed by our algorithm owing to non-stellar photometry flags or fewer epochs than the minimum required, and there were no matches at 1 for Navarrete et al (2015) are shown. Bottom panel: period histogram of the 1019 RRab stars with bins adapted by the Bayesian Block algorithm (Scargle et al 2013) through the astroML implementation (Vanderplas et al 2012).…”

Section: Detection and Classification Of Rr Lyrae Starsmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

Section: Detection and Classification Of Rr Lyrae Starsmentioning

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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“…They provided homogeneous JK s photometry for 180 variables and provided a new estimate of the ω Cen distance modulus using the K-band PL relation (13.77 ± 0.07 mag). A similar analysis was recently performed by Navarrete et al (2015) based on a large set of images collected with the VISTA telescope. They provided homogeneous JK s photometry for 189 probable member RRLs (101 RRc, 88 RRab) and discussed the pulsation properties of the entire sample in the NIR.…”

Section: Introductionmentioning

confidence: 87%

On THE RR LYRAE STARS IN GLOBULARS. IV. Ω CENTAURI OPTICAL UBVRI PHOTOMETRY*

Braga

Stetson

Bono

et al. 2016

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New accurate and homogeneous optical UBVRI photometry has been obtained for variable stars in the Galactic globular cluster ω Cen (NGC 5139). We secured 8202 CCD images covering a time interval of 24 years and a sky area of 84×48 arcmin. The current data were complemented with data available in the literature and provided new, homogeneous pulsation parameters (mean magnitudes, luminosity amplitudes, periods) for 187 candidate ω Cen RR Lyrae (RRLs). Among them we have 101RRc (first overtone) and 85RRab (fundamental) variables, and a single candidate RRd (double-mode) variable. Candidate Blazhko RRLs show periods and colors that are intermediate between the RRc and RRab variables, suggesting that they are transitional objects. A comparison of the period distribution and the Bailey diagram indicates that RRLs in ω Cen show a long-period tail not present in typical Oosterhoff II (OoII) globulars. The RRLs in dwarf spheroidals and in ultra-faint dwarfs have properties between Oosterhoff intermediate and OoII clusters. Metallicity plays a key role in shaping the above evidence. These findings do not support the hypothesis that ω Cen is the core remnant of a spoiled dwarf galaxy. Using optical period-Wesenheit relations that are reddening-free and minimally dependent on metallicity we find a mean distance to ω Cen of 13.71±0.08±0.01 mag (semi-empirical and theoretical calibrations). Finally, we invert the I-band period-luminosity-metallicity relation to estimate individual RRLs' metal abundances. The metallicity distribution agrees quite well with spectroscopic and photometric metallicity estimates available in the literature.

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“…All of the known variables are outside the field of view of our reference image. Most recently, Navarrete et al (2015) made an updated analysis of the variables in this cluster, but the variables in their study are also located outside the field of view of our reference image.…”

Section: Known Variablesmentioning

confidence: 99%

Exploring the crowded central region of ten Galactic globular clusters using EMCCDs

Jaimes¹,

Bramich²,

Skottfelt³

et al. 2016

A&A

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Aims. We aim to obtain time-series photometry of the very crowded central regions of Galactic globular clusters; to obtain better angular resolution than has been previously achieved with conventional CCDs on ground-based telescopes; and to complete, or improve, the census of the variable star population in those stellar systems. Methods. Images were taken using the Danish 1.54-m Telescope at the ESO observatory at La Silla in Chile. The telescope was equipped with an electron-multiplying CCD, and the short-exposure-time images obtained (ten images per second) were stacked using the shift-and-add technique to produce the normal-exposure-time images (minutes). Photometry was performed via difference image analysis. Automatic detection of variable stars in the field was attempted. Results. The light curves of 12 541 stars in the cores of ten globular clusters were statistically analysed to automatically extract the variable stars. We obtained light curves for 31 previously known variable stars (3 long-period irregular, 2 semi-regular, 20 RR Lyrae, 1 SX Phoenicis, 3 cataclysmic variables, 1 W Ursae Majoris-type and 1 unclassified) and we discovered 30 new variables (16 long-period irregular, 7 semi-regular, 4 RR Lyrae, 1 SX Phoenicis and 2 unclassified). Fluxes and photometric measurements for these stars are available in electronic form through the Strasbourg astronomical Data Center.

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Updated census of RR Lyrae stars in the globular clusterωCentauri (NGC 5139)

Cited by 30 publications

References 61 publications

Mapping the outer bulge with RRab stars from the VVV Survey

Mapping the outer bulge with RRab stars from the VVV Survey

On THE RR LYRAE STARS IN GLOBULARS. IV. Ω CENTAURI OPTICAL UBVRI PHOTOMETRY*

Exploring the crowded central region of ten Galactic globular clusters using EMCCDs

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