scholarly journals The Impact of Observing Strategy on the Reliable Classification of Standard Candle Stars: Detection of Amplitude, Period, and Phase Modulation (Blazhko Effect) of RR Lyrae Stars with LSST

2021 ◽  
Vol 258 (1) ◽  
pp. 4
Author(s):  
Nina Hernitschek ◽  
Keivan G. Stassun
Keyword(s):  
Phase Modulation ◽  
Variable Stars ◽  
Light Curves ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Standard Candle ◽  
Blazhko Effect ◽  
The Impact ◽  
Lyrae Stars

Abstract The Vera C. Rubin Observatory will carry out its Legacy Survey of Space and Time (LSST) with a single-exposure depth of r ∼ 24.7 and an anticipated baseline of 10 yr, allowing access to the Milky Way’s old halo not only deeper than, but also with a longer baseline and better cadence than, e.g., PS1 3π. This will make the LSST ideal to study populations of variable stars such as RR Lyrae stars (RRL). Here, we address the question of observing strategy optimization of LSST, as survey footprint definition, single-visit exposure time, as well as the cadence of repeat visits in different filters are yet to be finalized. We present metrics used to assess the impact of different observing strategies on the reliable detectability and classification of standard candle variable stars, including detection of amplitude, period, and phase modulation effects of RRL (the so-called Blazhko effect), by evaluating metrics for simulated potential survey designs. So far, due to the depths and cadences of typical all-sky surveys, it has been nearly impossible to study this effect on a larger sample. All-sky surveys with relatively few observations over a moderately long baseline allow only for fitting phase-folded RRL light curves, thus integrating over the complete survey length and hiding any information regarding possible period or phase modulation during the survey. On the other hand, surveys with cadences fit to detect slightly changing light curves usually have a relatively small footprint. LSST’s survey strategy, however, will allow for studying variable stars in a way that makes population studies possible.

A New Look at the Blazhko Effect in RR Lyrae Stars with High-Quality Data from the MACHO Project

2000 ◽  
Vol 176 ◽  
pp. 291-298 ◽  
Author(s):  
D. W. Kurtz ◽  
C. Alcock ◽  
R. A. Allsman ◽  
D. Alves ◽  
T. S. Axelrod ◽  
...  
Keyword(s):  
Phase Modulation ◽  
Period Change ◽  
Quality Data ◽  
High Quality Data ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Blazhko Effect ◽  
First Results ◽  
Lyrae Stars ◽  
Better Than

AbstractWe present the first results of the analysis of 22 Blazhko stars. We find: 1) Blazhko RRab stars that are nearly pure amplitude modulators; 2) Blazhko RRab stars that have both amplitude and phase modulation; 3) A Blazhko RRab star that has an abrupt period change; 4) Proof of the Blazhko effect in RRc stars. Our data show the character of the amplitude and phase modulations of the light curves over the Blazhko cycles far better than has been previously possible.

scholarly journals LSST Observations of RR Lyrae Stars for Mapping the Galactic Halo

2010 ◽  
Vol 6 (S277) ◽  
pp. 300-304
Author(s):  
Hakeem M. Oluseyi ◽  
Andrew C. Becker ◽  
Christopher C. Culliton ◽  
Muhammad Furqan ◽  
Keri L. Hoadley ◽  
...  
Keyword(s):  
Light Curve ◽  
Local Group ◽  
Galactic Halo ◽  
Variable Stars ◽  
Light Curves ◽  
Chemical Compositions ◽  
Galactic Halos ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

AbstractThe Large Synoptic Survey Telescope (LSST) is an anticipated to undertake a 10–year, 3π steradian survey that promises to observe millions of new periodic variable stars. We report on a study to determine the efficiency of the LSST to recover the light curve properties of RR Lyrae stars. An LSST light curve simulation tool was used to sample input idealized light curves or RR Lyrae stars observed in SDSS Stripe 82 data, returning each as it would have been observed by LSST, including realistic photometric scatter, limiting magnitudes, and telescope downtime. Our results show that the LSST will be capable of mapping the spatial distributions and chemical compositions of halo stellar overdensities using RR Lyrae discovered across 3π steradians and out to nearly 1.5 Mpc. LSST will thus enable the mapping of halo merger streams, the discovery of new dwarf galaxies, and the mapping galactic halos throughout the Local Group galaxies.

scholarly journals Informative Bayesian model selection for RR Lyrae star classifiers

2021 ◽  
Vol 503 (1) ◽  
pp. 484-497
Author(s):  
F Pérez-Galarce ◽  
K Pichara ◽  
P Huijse ◽  
M Catelan ◽  
D Mery
Keyword(s):  
Machine Learning ◽  
Marginal Likelihood ◽  
Likelihood Estimation ◽  
Variable Stars ◽  
Training Data ◽  
Multiple Sources ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

ABSTRACT Machine learning has achieved an important role in the automatic classification of variable stars, and several classifiers have been proposed over the last decade. These classifiers have achieved impressive performance in several astronomical catalogues. However, some scientific articles have also shown that the training data therein contain multiple sources of bias. Hence, the performance of those classifiers on objects not belonging to the training data is uncertain, potentially resulting in the selection of incorrect models. Besides, it gives rise to the deployment of misleading classifiers. An example of the latter is the creation of open-source labelled catalogues with biased predictions. In this paper, we develop a method based on an informative marginal likelihood to evaluate variable star classifiers. We collect deterministic rules that are based on physical descriptors of RR Lyrae stars, and then, to mitigate the biases, we introduce those rules into the marginal likelihood estimation. We perform experiments with a set of Bayesian logistic regressions, which are trained to classify RR Lyraes, and we found that our method outperforms traditional non-informative cross-validation strategies, even when penalized models are assessed. Our methodology provides a more rigorous alternative to assess machine learning models using astronomical knowledge. From this approach, applications to other classes of variable stars and algorithmic improvements can be developed.

scholarly journals RR Lyrae in M15: Fourier Decomposition and Physical Parameters

2006 ◽  
Vol 2 (S240) ◽  
pp. 605-612
Author(s):  
G. García Lugo ◽  
A. Arellano Ferro ◽  
Patricia Rosenzweig
Keyword(s):  
Globular Clusters ◽  
Light Curves ◽  
Physical Parameters ◽  
Rr Lyrae Stars ◽  
Mean Values ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
Blazhko Effect ◽  
The Mean ◽  
Lyrae Stars

AbstractThe V and R light curves for 30 RR Lyrae stars in M15 were used to calculate their physical parameters. The Blazhko effect, previously reported in V12, was not detected. The determined values of the iron content and distance of the cluster are: [Fe/H] = −1.98 ± 0.24 and d = 8.67 ± 0.41 kpc, respectively. The mean values of the physical parameters determined for the RR Lyrae stars place the cluster precisely into the sequences Oosterhoff type – metallicity and metallicity – effective temperature, valid for globular clusters.

scholarly journals The Characteristics of the Field RR Lyrae Stars in the Magellanic Clouds

1974 ◽  
Vol 59 ◽  
pp. 107-108
Author(s):  
J. A. Graham
Keyword(s):  
Stellar Evolution ◽  
Large Magellanic Cloud ◽  
Variable Stars ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Light Curves ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
First Results ◽  
Lyrae Stars

The Magellanic Clouds are well known as being very suitable for observing the various stages of stellar evolution. During the last few years, I have been studying the RR Lyrae variable stars in each of the two Clouds. Some first results were reported at IAU Colloquium No. 21 in 1972 (Graham, 1973). Here, I would like to update these results on the basis of more recent data and to comment on some of the characteristics of the field RR Lyrae stars in each system. Periods and light curves are now available for 63 RR Lyrae stars in a 1° x 1.3° field centered on the cluster NGC 1783 in the Large Magellanic Cloud (LMC) and for 62 stars in a 1° x 1.3° field centered on the cluster NGC 121 in the Small Magellanic Cloud (SMC). Both ab and c type variables are represented and, viewed individually, the Cloud RR Lyraes are identical in characteristics to those known in our Galaxy. Studied as groups, however, there are small but significant differences between the RR Lyrae stars in each system. The following four specific features seem to be emerging from the study.

The K2 RR Lyrae Survey

2017 ◽  
Vol 14 (S339) ◽  
pp. 83-86
Author(s):  
R. Szabó
Keyword(s):  
Statistical Study ◽  
Period Doubling ◽  
Variable Stars ◽  
Galactic Structure ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Continuous Coverage ◽  
Blazhko Effect ◽  
Lyrae Stars

AbstractIn the framework of this project, the K2 RR Lyrae Survey, we proposed to observe thousands of RR Lyrae stars along the Ecliptic in Kepler’s K2 Mission. The high photometric precision and the 80-to-90-day continuous coverage enabled us to investigate in unprecedented detail the light variations of these variable stars which can trace galactic structure. The survey enabled us to conduct a thorough statistical study of RR Lyrae pulsation dynamics, including both old and more recently discovered dynamical phenomena such as resonances, non-radial modes, period doubling and the Blazhko effect. This talk described the K2 RR Lyrae Survey, and discussed the prospects of combining our endeavour with Gaia, LSST and other surveys in the context of studies of Galactic archeology.

scholarly journals RR Lyrae Stars in the Globular NGC 3201: Light Curves, Reddening, and Distance

2002 ◽  
Vol 185 ◽  
pp. 122-123
Author(s):  
Andrew Layden
Keyword(s):  
Globular Clusters ◽  
Absolute Magnitude ◽  
Progress Report ◽  
Light Curves ◽  
High Quality ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Standard Candle ◽  
Trigonometric Parallaxes ◽  
Lyrae Stars

RR Lyrae stars (RRL) are a favourite standard candle for globular clusters and other old stellar populations, yet recent absolute magnitude calibrations, MV(RR), span more than 0.2 mag. Precise distance estimates for nearby globular clusters will eventually be available through satellite-based trigonometric parallaxes (Layden, these proceedings), thus providing a resolution to this old problem.Here, we present a progress report on our high quality time-series photometry of RRL in the nearby globular cluster NGC 3201 - the first obtained for this cluster with a CCD. The resulting light curves provide accurate intensity-mean apparent magnitudes and reddening estimates, which will in turn be used to calibrate MV(RR) once a satellite-based parallax for NGC 3201 is available.

Rr Lyrae Variable Stars

1980 ◽  
Vol 5 ◽  
pp. 489-492
Author(s):  
Yu. S. Romanov ◽  
V. P. Tsesevich ◽  
L. P. Zaikova ◽  
B. N. Firmanyuk ◽  
S. N. Udovichenko ◽  
...  
Keyword(s):  
Variable Stars ◽  
Astronomical Observatory ◽  
Light Variation ◽  
General Assembly ◽  
Rr Lyrae Stars ◽  
Observational Material ◽  
Rr Lyrae ◽  
Regular Control ◽  
Lyrae Stars

Some twenty years have passed since the decision was taken by the General Assembly of IAU in 1958 to resume a regular control of light variation stability in RR Lyrae stars. With this end in view the revision of elements is carried out at the Odessa Astronomical Observatory yearly, whereas ephemerides of RR Lyrae stars are published at the Krakov Observatory. Now 164 stars brighter than at maximum light visible in the northern hemisphere have entered the list.Considerable photometric observational material analyzed has shown that some RR Lyrae stars have stable periods of light variation (e.g. TV Lib, UY Cyg, SU Dra), while other ones have periods which vary regularly or proportionally to time (e.g. SV Eri, AV Peg, RV CrB) (Tsesevich, 1966; Firmanyuk, 1976; Romanov et al., 1978). In case of DR And at comparatively small amplitude of O-C variation, about 0.15, a synchronous variation in mean light at maximum nearly by has been found (Romanov, 1978). Unfortunately, necessary observational material is frequently unavailable to obtain the unambiguous classification of period stability character. The property of RR Lyrae stars light variation stability is connected with the weakening of KCall absorption line (Tsesevich, 1966, 1971).

scholarly journals Time-Domain Astrophysics with SuperWASP

2011 ◽  
Vol 7 (S285) ◽  
pp. 382-384
Author(s):  
A. J. Norton ◽  
Keyword(s):  
Binary Stars ◽  
Variable Stars ◽  
Eclipsing Binaries ◽  
Rr Lyrae Stars ◽  
Long Baseline ◽  
Rr Lyrae ◽  
Look Ahead ◽  
Blazhko Effect ◽  
Data Points ◽  
Lyrae Stars

AbstractSuperWASP is the world's leading ground-based survey for transiting exoplanets. Its database now contains over 300 billion data points covering 30 million unique objects from 10 million images obtained over 1700 nights since 2004. In addition to having discovered 70 transiting exoplanets, SuperWASP enables long-baseline, high-cadence studies of variable stars to be performed. We summarise some of the studies already carried out, and look ahead to the prospects for studying periodic variables with varying periods. The science which is thus supported will include studies of the Blazhko effect in RR Lyræ stars, migrating starspots in rotational variables, third bodies in eclipsing binaries, and coalescing binary stars.

scholarly journals The Unusual Period Distribution of the RR Lyrae Variables in NGC 5897

1989 ◽  
Vol 111 ◽  
pp. 287-287
Author(s):  
Amelia Wehlau
Keyword(s):  
Light Curves ◽  
Instability Strip ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Period Distribution ◽  
Unusual Distribution ◽  
Photoelectric Observations ◽  
Lyrae Stars ◽  
Branch Star ◽  
Central Concentration

AbstractAttention is called to the rather unusual distribution of the periods of the RR Lyrae variables in NGC 5897, a metal-poor halo globular cluster with a very low central concentration. Of the seven RR Lyrae stars known in the cluster, three have periods between 0.797 and 0.856 day and two have periods of 0.45 and 0.42 day. The other two have periods of 0.34 and 0.35 day with much lower amplitudes of variation. Due to the lack of crowding in this cluster photoelectric observations and Fourier decompositions of the resulting light curves should be possible for at least six of the RR Lyrae variables. In addition, the cluster appears to contain a non-variable horizontal branch star, SK 120, lying within the instability strip. As this is the only well documented case of such a star, photoelectric observations of this star would also be desirable.

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