Magellanic Cloud Halo RR Lyrae Stars: The NGC 2257 Field in the Outskirts of the LMC

AbstractThe Large Magellanic Cloud (LMC) is widely considered a corner-stone of the astronomical distance scale. However, a difference of 0.2−0.3 mag exists in its distance as predicted by the short and long distance scales. Distances to the LMC from Population II objects are founded on the RR Lyrae variables. We have undertaken an observational campaign devoted to the definition of the average apparent luminosity, and to the study of the mass–metallicity relation for RR Lyrae stars in the bar of the LMC. These are compared with analogous quantities for cluster RR Lyrae stars. The purpose is to see whether an intrinsic difference in luminosity, possibly due to a difference in mass, might exist between field and cluster RR Lyrae stars, which could be responsible for the well-known dichotomy between short and long distance scales. Preliminary results are presented on the V and B − V light curves, the average apparent visual magnitude, and the pulsational properties of 102 RR Lyrae stars in the bar of the LMC, observed at ESO in January 1999. The photometric data are accurately tied to the Johnson photometric system. Comparison is presented with the photometry of RR Lyrae stars in the bar of the LMC obtained by the MACHO collaboration (Alcock et al. 1996). Our sample includes 9 double-mode RR Lyrae stars selected from Alcock et al. (1997) for which an estimate of the metal abundance from the ΔS method is presented.

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Standard Galactic field RR Lyrae II: a Gaia DR2 calibration of the period–Wesenheit–metallicity relation

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2814 ◽

2019 ◽

Vol 490 (3) ◽

pp. 4254-4270 ◽

Cited By ~ 4

Author(s):

Jillian R Neeley ◽

Massimo Marengo ◽

Wendy L Freedman ◽

Barry F Madore ◽

Rachael L Beaton ◽

...

Keyword(s):

Near Infrared ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Distance Modulus ◽

Rr Lyrae Stars ◽

Galactic Field ◽

Rr Lyrae ◽

Lyrae Stars ◽

Distance Indicators ◽

Made In

ABSTRACT RR Lyrae stars have long been popular standard candles, but significant advances in methodology and technology have been made in recent years to increase their precision as distance indicators. We present multiwavelength (optical UBVRcIc and Gaia G, BP, RP; near-infrared JHKs; mid-infrared [3.6], [4.5]) period–luminosity–metallicity (PLZ), period–Wesenheit–metallicity (PWZ) relations, calibrated using photometry obtained from the Carnegie RR Lyrae Program and parallaxes from the Gaia second data release for 55 Galactic field RR Lyrae stars. The metallicity slope, which has long been predicted by theoretical relations, can now be measured in all passbands. The scatter in the PLZ relations is on the order of 0.2 mag, and is still dominated by uncertainties in the parallaxes. As a consistency check of our PLZ relations, we also measure the distance modulus to the globular cluster M4, the Large Magellanic Cloud and the Small Magellanic Cloud, and our results are in excellent agreement with estimates from previous studies.

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Near-Infrared photometry of the LMC cluster Reticulum

International Astronomical Union Colloquium ◽

10.1017/s0252921100010605 ◽

2004 ◽

Vol 193 ◽

pp. 189-192

Author(s):

M. Dall’Ora ◽

G. Bono ◽

J. Storm ◽

V. Ripepi ◽

V. Testa ◽

...

Keyword(s):

Data Reduction ◽

Near Infrared ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Distance Estimate ◽

Infrared Photometry ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Lyrae Stars

AbstractWe present U, B, V, I (SUSI@NTT) and J,Ks (SOFI@NTT) photometry of the Large Magellanic Cloud (LMC) cluster Reticulum. The observing strategy and data reduction (DAOPHOTII/ALLFRAME) allowed us to reach an accuracy of the order of 0.01 – 0.03 mag in all the bands at limiting magnitudes typical of RR Lyrae stars. Reticulum hosts a sizable sample of RR Lyrae stars (32), and we supply an accurate distance estimate using the RR Lyrae K-band Period-Luminosity-Metallicity (PLZK) relation. This method presents several advantages when compared with the MV vs [Fe/H] relation, since it is only marginally affected by off-ZAHB evolutionary effects and reddening corrections.

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