The Variable-Star Population in Phoenix: Coexistence of Anomalous and Short-Period Classical Cepheids and Detection of RR Lyrae Variables

Abstract We present the period-radius relations predicted by nonlinear convective models of Classical Cepheids and RR Lyrae stars. For the former variables we show that the metallicity effect is negligible for both fundamental and first overtone pulsators. This confirms the power of the period-radius relation to estimate Cepheid radii and in turn distances. For the latter class of variables we show that the dispersion of the period-radius relation of both fundamental and first overtone pulsators is significantly reduced once the metallicity dependence is taken into account. This provides a robust method to evaluate the radius of observed RR Lyrae with measured period and metal abundance.

Download Full-text

OGLE-ing the Magellanic System: Three-Dimensional Structure

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318007093 ◽

2018 ◽

Vol 14 (S344) ◽

pp. 86-89

Author(s):

Anna M. Jacyszyn-Dobrzeniecka ◽

Keyword(s):

Three Dimensional ◽

Neutral Hydrogen ◽

Variable Stars ◽

Dimensional Structure ◽

Rr Lyrae Stars ◽

Three Dimensional Structure ◽

Rr Lyrae ◽

Classical Cepheids ◽

Lyrae Stars ◽

Magellanic System

AbstractWe present a three-dimensional structure of the Magellanic System using over 9 000 Classical Cepheids and almost 23 000 RR Lyrae stars from the OGLE Collection of Variable Stars. Given the vast coverage of the OGLE-IV data and very high completeness of the sample, we were able to study the Magellanic System in great details.We very carefully studied the distribution of both types of pulsators in the Magellanic Bridge area. We show that there is no evident physical connection between the Clouds in RR Lyrae stars distribution. We only see the two extended structures overlapping. There are few classical Cepheids in the Magellanic Bridge area that seem to form a genuine connection between the Clouds. Their on-sky locations match very well young stars and neutral hydrogen density contours. We also present three-dimensional distribution of classical pulsators in both Magellanic Clouds.

Download Full-text

CCD Observations of Variable Stars in Globular Clusters

International Astronomical Union Colloquium ◽

10.1017/s0252921100011933 ◽

1989 ◽

Vol 111 ◽

pp. 285-285

Author(s):

H.A. Smith ◽

J.R. Kuhn ◽

J. Curtis

Keyword(s):

Globular Cluster ◽

Globular Clusters ◽

Variable Stars ◽

Michigan State University ◽

State University ◽

Ccd Photometry ◽

Rr Lyrae ◽

Short Period ◽

Ccd Observations ◽

Period Variable

AbstractBVR observations of the relatively metal-rich globular cluster NGC 6388 have been obtained with a CCD on the CTIO 0.9 m telescope. Eighteen possible short period variable stars have been discovered in or near the cluster. At least 10 of these are probable RR Lyrae members of NGC 6388. We confirm the finding of Hazen and Hesser that this cluster is one of the most metal-rich to contain a significant number of RR Lyraes. A program of CCD photometry of field and cluster variable stars has been initiated on the 0.6m telescope of the Michigan State University Observatory.

Download Full-text

Search for Variables in the Galactic Globular Clusters NGC 6544 and NGC 6642

International Astronomical Union Colloquium ◽

10.1017/s0252921100117774 ◽

1993 ◽

Vol 139 ◽

pp. 337-337

Author(s):

Martha L. Hazen

Keyword(s):

Globular Clusters ◽

Slow Variable ◽

Variable Stars ◽

Horizontal Branch ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

A Value ◽

Short Period ◽

Period Variable ◽

Lyrae Stars

A search for variable stars in the globular cluster NGC 6544 has revealed only one possible short period variable within the tidal radius of the cluster. A search in NGC 6642 yielded 16 new RR Lyrae stars within the tidal radius and 5 new field RRs. The previously discovered (Hoffleit 1972) V1 is a slow variable, and V2 is an RR Lyrae star. Photometry of the variables within the tidal radius gives a mean B for the horizontal branch of < B > = 17.0 mag. With E(B – V) = 0.37 mag and (B – V) = 0.35 mag for RR Lyraes, a value for V(HB) = 16.3 mag is derived. This is about one mag fainter than previous estimates (Webbink 1985), and places NGC 6642 at a distance of approximately 7.9 kpc.

Download Full-text