Article
Astronomy & Astrophysics
Christina K. Gilligan, Brian Chaboyer, Massimo Marengo, Joseph P. Mullen, Giuseppe Bono, Vittorio F. Braga, Juliana Crestani, Massimo Dall'Ora, Giuliana Fiorentino, Matteo Monelli, Jill R. Neeley, Michele Fabrizio, Clara E. Martinez-Vazquez, Frederic Thevenin, Christopher Sneden
Summary: Accurate metallicities of RR Lyrae stars were analyzed in this study using high-resolution spectra from the Southern African Large Telescope. The study presented new period-luminosity-metallicity relationships in WISE W1 and W2 magnitudes, as well as the Wesenheit magnitudes W(W1, V - W1) and W(W2, V- W2) by combining new spectroscopic abundances with literature determinations for 93 stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
V. F. Braga, G. Fiorentino, G. Bono, P. B. Stetson, C. E. Martinez-Vazquez, S. Kwak, M. Tantalo, M. Dall'Ora, M. Di Criscienzo, M. Fabrizio, M. Marengo, S. Marinoni, P. M. Marrese, M. Monelli
Summary: We investigated the properties of mixed-mode RR Lyrae variables in the Fornax dwarf spheroidal galaxy and compared them with variables in the Magellanic Clouds and nearby dwarf spheroidals. We found that the ratio of mixed-mode RR Lyrae decreases with metallicity, and Fornax fills a period gap in the Petersen diagram similarly to Small Magellanic Cloud variables. Additionally, a new pulsation diagnostics method reveals that Large Magellanic Cloud variables can be separated into two groups with different evolutionary properties. Our findings suggest that Fornax and Sculptor dwarf spheroidals have undergone different chemical enrichment histories.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Ata Sarajedini, Sevinc Gokmen
Summary: This study compares two relations for calculating the metal abundance of ab-type RR Lyrae variables and determines that knowing only the period of these variables is sufficient to determine the mean metallicity of a globular cluster. Both tested equations accurately reproduce the spectroscopic metal abundance of each cluster, with an accuracy of ±0.28 dex.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Thomas A. Molnar, Jason L. Sanders, Leigh C. Smith, Vasily Belokurov, Philip Lucas, Dante Minniti
Summary: The study introduces the VIVACE catalogue which extracts variable stars from the VVV infrared survey data through an automated classification pipeline. Utilizing a two-stage hierarchical classifier, the research identifies and classifies variable sources, resulting in a catalogue of approximately 1.4 million likely variable stars with different types and classification probabilities.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Yoichi Takeda
Summary: The photospheric abundances of C, N, O, and Na in RR Lyr stars were studied to investigate the mixing mechanism in low-mass giant stars. The study confirmed the deficiency in C and enrichment in N in these stars, with the extent of peculiarities increasing with a decrease in metallicity. However, no apparent Na anomaly was observed, contradicting theoretical expectations. Further improvements in the current theory may be necessary.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Henryka Netzel, Radoslaw Smolec
Summary: This paper discusses the phenomenon and explanation of additional signals observed in the frequency spectra of first-overtone RR Lyrae stars, and attempts to model these stars with non-radial modes, finding that pulsation masses seem higher than evolutionary masses.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
M. Marconi, R. Molinaro, V Ripepi, S. Leccia, I Musella, G. De Somma, M. Gatto, M. Moretti
Summary: Theoretical light curves in Gaia bands G, G(BP), and G(RP) for RR Lyrae pulsators are derived based on extended non-linear convective models. The effects of chemical composition on the derived parameters and Period-Wesenheit relations are discussed, and theoretical estimates of individual parallaxes for Galactic RR Lyrae in Gaia Data Release 2 are compared with astrometric solutions. A very small offset, consistent with zero, is required to reconcile the predicted distances with Gaia results.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Nitesh Kumar, Anupam Bhardwaj, Harinder P. Singh, Susmita Das, Marcella Marconi, Shashi M. Kanbur, Philippe Prugniel
Summary: We propose a new technique using artificial neural networks (ANN) to generate light curves of RRab stars in different photometric bands. The ANN is trained using a pre-computed grid of models and optimized using I-band light curves. The trained interpolators successfully predict the light curves of RRab stars in the Magellanic Clouds, and the distances to the Large Magellanic Cloud and Small Magellanic Cloud are determined based on the Wesenheit index. The ANN interpolator provides a fast and efficient method for generating model light curves, which is computationally expensive using traditional stellar pulsation codes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Ata Sarajedini
Summary: In this study, we analyze archival images of the Wolf-Lundmark-Melotte (WLM) galaxy taken with the Hubble Space Telescope, and identify and characterize RR Lyrae and Cepheid variables. We find that the WLM globular cluster has a lower metallicity than previously thought.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
H. Netzel, L. Molnar, E. Plachy, J. M. Benko
Summary: This article utilizes samples of first-overtone RR Lyrae stars observed by the Kepler telescope during the K2 mission to search for and characterize additional low-amplitude signals. The study discovers new sequences of period ratios and unknown periodicity phenomena.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Kuan-Wei Huang, Sergey E. Koposov
Summary: We present an RR Lyrae (RRL) catalogue based on the combination of ZTF DR3 and Gaia EDR3, which includes period and light-curve parameter measurements and has high completeness and purity. This catalogue covers the Northern sky with declination >= -28 degrees and is more complete around the Galactic halo compared to other catalogues.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Ata Sarajedini
Summary: By using observations of ab-type RR Lyrae variables in M31 and M33 from the Hubble Space Telescope, a purely differential line-of-sight distance between the two galaxies was presented. The study found that M33 is approximately 115 kpc beyond M31 in terms of line-of-sight distance.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
A. Bhardwaj, S. M. Kanbur, M. Rejkuba, M. Marconi, M. Catelan, V. Ripepi, H. P. Singh
Summary: The study aims to characterize the pulsation properties of the population II RRL and T2C variables in NGC 6441 and compare them with other clusters and theoretical predictions. The results show that the pulsation properties of RRL variables in NGC 6441 are consistent with theoretical models, indicating that these variables may not be significantly helium-enhanced as previously thought.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Anupam Bhardwaj, Marina Rejkuba, Richard de Grijs, Soung-Chul Yang, Gregory J. Herczeg, Marcella Marconi, Harinder P. Singh, Shashi Kanbur, Chow-Choong Ngeow
Summary: This study presents new near-infrared period-luminosity relations for RR Lyrae variables in the Messier 53 globular cluster, utilizing JHK(s) observations to estimate precise mean magnitudes and predict parallaxes for Galactic RR Lyrae stars. The results show constrained PLRs for RRab types and a theoretical distance modulus for M53, as well as the empirical calibration of a new RR Lyrae PLZ(Ks) relation anchored with Gaia EDR3 distances.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Anupam Bhardwaj, Marcella Marconi, Marina Rejkuba, Richard de Grijs, Harinder P. P. Singh, Vittorio F. F. Braga, Shashi Kanbur, Chow-Choong Ngeow, Vincenzo Ripepi, Giuseppe Bono, Giulia De Somma, Massimo Dall'Ora
Summary: We empirically measure the distances of RR Lyrae stars using near-infrared monitoring of Galactic globular clusters and find a significant dependence of their near-infrared period-luminosity relationships on metallicity. The metallicity coefficients and zero-points of the empirical relationships are consistent with theoretical predictions, and the RR Lyrae-based distances to the globular clusters are consistent with other independent measurements.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
