The Virgo Stellar Stream: Extended sample

AbstractWe have completed a spectroscopic study of the “12.4 hr clump”, the second largest substructure in the Quasar Equatorial Survey Team (QUEST) catalog. First discovered as an over-density of RR Lyrae stars (Vivas et al. 2001, ApJL 554 33), the region containing the “12.4 hr clump” has generated much interest (Newberg et al. (2002), Martinez-Delgado et al. (2007), Juric et al. (2008), amongst many others). Our first spectroscopic study of this clump revealed the presence of a sharp peak in the radial velocity histogram for the candidate stars (Duffau et al. 2006). The combination of this result and metal abundance estimates for the sample was then interpreted as a signature of the presence of a stellar stream within the clump. This sub-structure was named the “Virgo Stellar Stream” (VSS), given its location in the direction of the Virgo Constellation, at approximately 20 kpc from the Sun. Several other groups have studied this region and have suggested that the over-density containing the VSS could extend to larger areas of the sky (outside QUEST's observing range). We present the complete spectroscopic follow up of the clump candidates present in QUEST and the composite of the studies we performed along the same l.o.s., including data at brighter magnitudes (Vivas et al. 2008). Our study confirmed the nature of the VSS, revealed its likely extent within the QUEST survey and defined a number of its relevant properties.

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The Period-Radius Relation: Classical Cepheids and RR Lyrae stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100011222 ◽

2004 ◽

Vol 193 ◽

pp. 502-505

Author(s):

M. Marconi ◽

G. Bono ◽

T.E. Nordgren

Keyword(s):

Robust Method ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Classical Cepheids ◽

Metal Abundance ◽

Lyrae Stars

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.

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Light Curves and Metal Abundances of RR Lyrae Variables in the Bar of the Large Magellanic Cloud

International Astronomical Union Colloquium ◽

10.1017/s0252921100057481 ◽

2000 ◽

Vol 176 ◽

pp. 172-175 ◽

Cited By ~ 1

Author(s):

G. Clementini ◽

A. Bragaglia ◽

L. Di Fabrizio ◽

E. Carretta ◽

R. G. Gratton

Keyword(s):

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Light Curves ◽

Photometric System ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Visual Magnitude ◽

Metal Abundance ◽

Definition Of ◽

Lyrae Stars

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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Period-Luminosity-Metal Abundance Relations for Population II Variable Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100116896 ◽

1993 ◽

Vol 139 ◽

pp. 31-52 ◽

Cited By ~ 1

Author(s):

James M. Nemec ◽

Thomas E. Lutz

Keyword(s):

Variable Stars ◽

Clear Trend ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Short Period ◽

New Period ◽

Blue Straggler ◽

Metal Abundance ◽

Filter Type ◽

Lyrae Stars

AbstractNew period-luminosity-metallicity (P-L-[Fe/H]) relationships for Pop. II Cepheids, RR Lyrae stars, anomalous Cepheids and SX Phe (variable-blue straggler) stars are presented. These were computed by fitting regression lines to observed pulsation periods and mean B, V, K magnitudes for over 1200 stars in ∼40 stellar systems. The stars were assumed to be pulsating in either the fundamental (F) or first-overtone (H) modes (excluding double-mode and other multi-periodic variables). Eight P-L-[Fe/H] relationships (one for each of the two pulsation modes for the four kinds of stars) were simultaneously fitted for each filter. After accounting for the metal abundance differences, the slopes of the P-L relations were tested for departures from equality. The results are consistent with the assumption that, for each kind of star, the relations for the F and H stars are vertically offset, with a family of lines corresponding to the different metallicities. In the case of the globular cluster Cepheids, the available B, V data support Arp's 1955 contention that the Cepheids are oscillating in the F and H modes; moreover, the majority of the short-period Cepheids (BL Her stars) appear to be first-overtone pulsators, while most of the Cepheids with periods between 10 and 30 days (W Vir stars) appear to be fundamental-mode pulsators. For the RR Lyrae stars, the slopes of the P-L-[Fe/H] relations in B, V and K show a clear trend with filter type, namely, the absolute values of the slopes increase from B to K. Finally, for the SX Phe stars the differences between the P-L-[Fe/H] relations in B and V for the F and H stars are found to be consistent with the known period-ratio for the double-mode star SX Phe.

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Convection during the formation of gaseous giants and stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307000440 ◽

2006 ◽

Vol 2 (S239) ◽

pp. 211-216

Author(s):

Günther Wuchterl

Keyword(s):

System Of Equations ◽

The Sun ◽

Rr Lyrae Stars ◽

Solar Convection Zone ◽

Solar Convection ◽

Rr Lyrae ◽

Wide Range ◽

Consistent Solution ◽

Convection Model ◽

Lyrae Stars

AbstractConvection theories for star and planet formation studies have to be (1) simple, to allow a self-consistent solution with other relevant processes, (2) time-dependent, because convection often starts in collapse-flows, and (3) robust, i.e. physically well-behaved under a wide range of conditions ranging from the quiet protoplanetary nebula to supercritical protostellar accretion-shocks with Mach-numbers of a few hundred. I describe how the equations of radiation fluid-dynamics can be augmented by a one-equation convection model in order to construct a system of equations that contains the Sun, brown dwarfs and planets as well as their nearly isothermal parent-clouds. The system of equations is calibrated to the Sun and tested by the solar convection zone and the pulsations of RR-Lyrae stars. I discuss the following applications: (1) star formation as the collapse of Bonnor-Ebert spheres of masses ranging from the stellar domain to the brown dwarf region, (2) the approach to the main sequence, (3) companion mass determinations for direct imaging searches for exoplanets, with GQ Lupi as an example, and (4) the formation of Pegasi-planets, and the “large core” exoplanet, HD 149 026, in particular.

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Radial-velocity curves for RR Lyrae stars in the globular clusters M5 and M92 obtained using synthetic spectra cross-correlation templates

Publications of the Astronomical Society of the Pacific ◽

10.1086/132974 ◽

1992 ◽

Vol 104 ◽

pp. 168 ◽

Cited By ~ 5

Author(s):

Jesper Storm ◽

Bruce W. Carney ◽

David W. Latham ◽

Robert J. Davis ◽

John B. Laird

Keyword(s):

Radial Velocity ◽

Globular Clusters ◽

Cross Correlation ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Synthetic Spectra ◽

Lyrae Stars

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Ground-based photometry for 42 Kepler-field RR Lyrae stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313014889 ◽

2013 ◽

Vol 9 (S301) ◽

pp. 427-428 ◽

Cited By ~ 1

Author(s):

Young-Beom Jeon ◽

Chow-Choong Ngeow ◽

James M. Nemec

Keyword(s):

Light Curves ◽

Astronomy Observatory ◽

Color Information ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Photometric Observations ◽

Data Points ◽

Optical Astronomy ◽

Lyrae Stars

AbstractFollow-up (U)BVRI photometric observations have been carried out for 42 RR Lyrae stars in the Kepler field. The new magnitude and color information will complement the available extensive high-precision Kepler photometry and recent spectroscopic results. The photometric observations were made with the following telescopes: 1-m and 41-cm telescopes of Lulin Observatory (Taiwan), 81-cm telescope of Tenagra Observatory (Arizona, USA), 1-m telescope at the Mt. Lemmon Optical Astronomy Observatory (LOAO, Arizona, USA), 1.8-m and 15-cm telescopes at the Bohyunsan Optical Astronomy Observatory (BOAO, Korea) and 61-cm telescope at the Sobaeksan Optical Astronomy Observatory (SOAO, Korea). The observations span from 2010 to 2013, with ~200 to ~600 data points per light curve. Preliminary results of the Korean observations were presented at the 5th KASC workshop in Hungary. In this work, we analyze all observations. These observations permit the construction of full light curves for these RR Lyrae stars and can be used to derive multi-filter Fourier parameters.

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Review of Observational Data on RR Lyrae Stars

Highlights of Astronomy ◽

10.1017/s1539299600000915 ◽

1971 ◽

Vol 2 ◽

pp. 781-787

Author(s):

G. van Herk

Keyword(s):

Radial Velocity ◽

Observational Data ◽

Proper Motion ◽

Point Of View ◽

Proper Motions ◽

Physical Point ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Complete Set ◽

Lyrae Stars

The data on which my work on the secular parallaxes of RR Lyrae stars is based (Bull. Astron. Inst. Neth.18) were in many respects so incomplete that I have tried to interest astronomers to get a more complete set of data. The number of stars for which I had a proper motion was only 168, and for which a radial velocity was known, was 180, with an overlap of only 138 stars. The accuracy of the proper motions was certainly unsatisfactory for 43% of the total. The greatest trouble in dealing with such insufficient numbers arises when one wants to subdivide the material into groups which are homogeneous from a physical point of view. Many subdivisions, in making up my paper, were not tried at all, simply because the material was inadequate.In recent years plenty of work has been done by various investigators, of which I will at this point only mention the work on proper motions done at the Leander McCormick Observatory, and the great number of radial velocities determined by Dr. Clube and his associates. I do not, however, believe we are yet in a position to consider the whole subject as finished. Discussions about space motions, as given by Professor Oort in the book Stellar Structures, Volume V, will, at this time, be hardly improved upon. I still feel we should increase the number of stars substantially in order to get a better statistical discussion possible. This means we have to go to fainter stars. Plenty of these stars will be found on the plates which have served to make the Charts of the Carte du Ciel, which means we have at least one old position available for proper motions. At Leiden we are now engaged in the determination or redetermination of the proper motions of 430 RR Lyrae stars.

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