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
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
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
J. M. Benko, E. Plachy, H. Netzel, A. Bodi, L. Molnar, A. Pal
Summary: Using TESS space telescope data, we investigated the time series of 633 RR Lyrae stars and found that 82.8% of them have additional frequencies beyond the main pulsation. The additional frequencies may belong to non-radial modes, particularly l=10 modes. Stars with shorter periods tend to have no additional frequencies, while longer period stars almost always show additional frequencies. The incidence rate and period distribution match well with recent theoretical models. Amplitude and phase of additional frequencies vary over time, and different non-radial modes have different time-scale variations. We also observed the Blazhko effect in 10.4% of the stars and detected annual-scale phase changes without significant amplitude variation.
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
L-J Li, S-B Qian, L-Y Zhu
Summary: This study reanalyzed the c-type RR Lyrae star BE Dor that showed cyclic period changes and found that these changes are quasi-periodic and abrupt, which cannot be explained by the light-traveltime effect. The study suggests that the period modulation in BE Dor may be caused by the interaction between turbulent convection and magnetic field activity.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
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
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
Geza Kovacs, Behrooz Karamiqucham
Summary: The study combines observational data with models to derive average luminosities for RR Lyrae stars and finds that they are in agreement with high accuracy parallax measurements. However, about 10% of the sample shows a curious distance keeping behavior between evolutionary and pulsation models, which may be addressed by increasing reddening excessively.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Johanna Jurcsik, Aron Juhasz
Summary: The study showed that some stars have light curves very similar to typical bulge RR Lyrae stars based on Fourier parameters. Calculating the physical properties revealed that short-period stars are less metal-poor, fainter, smaller, and hotter than long-period variables.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
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
Andrew M. Hoffman, Yukei S. Murakami, WeiKang Zheng, Benjamin E. Stahl, Alexei Filippenko
Summary: This study presents measurements of periods, amplitudes, and types of 74 RR Lyrae stars in the globular cluster M15 based on Nickel 1m telescope observations at Lick Observatory in 2019 and 2020. It identifies new Type II Cepheid variable stars, as well as stars with uncertain classifications and periods. The study also discusses the development and application of a new PYTHON package, PIPS, for period determination and uncertainty treatment in variable stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
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
Jozsef M. Benko, Adam Sodor, Andras Pal
Summary: The study found that T Sex may be the first representative of rare RRc stars observed from space photometry, with an additional pulsation frequency and characteristic line distortion. This indicates differences in turbulent convection and macroturbulent velocity between T Sex and typical RRab stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
L. Molnar, A. Bodi, A. Pal, A. Bhardwaj, F-J Hambsch, J. M. Benko, A. Derekas, M. Ebadi, M. Joyce, A. Hasanzadeh, K. Kolenberg, M. B. Lund, J. M. Nemec, H. Netzel, C. -C Ngeow, J. Pepper, E. Plachy, Z. Prudil, R. J. Siverd, M. Skarka, R. Smolec, A. Sodor, S. Sylla, P. Szabo, R. Szabo, H. Kjeldsen, J. Christensen-Dalsgaard, G. R. Ricker
Summary: The TESS space telescope is studying RR Lyrae stars and found that their mode distribution is different from that of bulge stars, potentially due to differences in physical parameters. However, uncertainties in determining the true pulsation frequencies of the extra modes hinder mode identification. In addition, a high percentage of modulated stars are found among fundamental mode pulsators, but a significant fraction of stars lack the Blazhko effect.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2022)
Article
Astronomy & Astrophysics
Attila Bodi, Pal Szabo, Emese Plachy, Laszlo Molnar, Robert Szabo
Summary: In this paper, we present an outline of the automated version of the EAP method, called autoEAP, which compensates for the systematic errors caused by the two-wheel-mode operation in the Kepler space telescope's K2 mission. We compare the light curve results to other photometric solutions and also introduce a new detrending method based on phase dispersion minimization for periodic variable stars.
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC
(2022)
Article
Astronomy & Astrophysics
Adrienn Forro, Robert Szabo, Attila Bodi, Kornel Csaszar
Summary: This paper describes a project that investigates individual pixels in the downloaded Kepler apertures to find objects in the background of main targets with changing brightness. The study discovered 26 new RR Lyrae stars and provides continuous and precise photometry for these objects. The research sheds light on these faint and distant stars and their characteristics in terms of light curves and pulsation.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2022)
Article
Astronomy & Astrophysics
T. Szklenar, A. Bodi, D. Tarczay-Nehez, K. Vida, Gy Mezo, R. Szabo
Summary: In this experiment, a Multiple-input Neural Network was developed to distinguish variable stars based on the visual characteristics of their light curves. By incorporating additional numerical information, the accuracy of classification was improved. The results showed that the Multiple-input Neural Network method is a promising alternative to existing classification methods.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Monika Jurkovic, Emese Plachy, Laszlo Molnar, Martin A. T. Groenewegen, Attila Bodi, Pawel Moskalik, Robert Szabo
Summary: We presented the results of analyzing Type II and anomalous Cepheids using data from the Kepler K2 mission. The precise light curves of these pulsating variable stars are essential for studying their pulsation details and effects. The analysis included Fourier analysis of the light curves and determining physical parameters through model fitting. The study also compared the stars with evolutionary models and found the presence of period doubling and modulation effects.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Viktoria Kecskemethy, Csaba Kiss, Robert Szakats, Andras Pal, Gyula M. Szabo, Laszlo Molnar, Krisztian Sarneczky, Jozsef Vinko, Robert Szabo, Gabor Marton, Aniko Farkas-Takacs, Csilla E. Kalup, Laszlo L. Kiss
Summary: This paper presents the results of K2 observations of 66 trans-Neptunian objects, revealing new identifications and evidence of slow rotation. The detectability rate of light-curve periods was only 56%, lower than other small-body populations. Surprisingly, the trans-Neptunian objects showed higher light-curve amplitudes at larger sizes, in contrast to the expected behavior.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2023)
Article
Astronomy & Astrophysics
Dora Tarczay-Nehez, Laszlo Molnar, Attila Bodi, Robert Szabo
Summary: In this study, six ULA Cepheid candidates in the Milky Way were investigated using CoRoT and 2MASS data. The absolute magnitudes and distances of each star were calculated using Gaia DR3 parallax and brightness data. Fourier parameters were calculated based on CoRoT and TESS measurements, and long-term phase shifts were established for four out of six stars. The results indicate that none of the six ULA Cepheid candidates are pulsating variable stars, but rather rotation-induced variable stars (rotational spotted and a(2) Canum Venaticorum variables) that differ in color or luminosity from Cepheids.
ASTRONOMY & ASTROPHYSICS
(2023)
Review
Physics, Multidisciplinary
Richard J. Szabo, Michelangelo Tirelli
Summary: This article is a mini-review on generalized instantons of noncommutative gauge theories in dimensions 4, 6 and 8, focusing on their realizations in type II string theory, their geometric interpretations, and their applications in enumerative geometry of non-compact toric varieties.
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS
(2023)
Article
Astronomy & Astrophysics
Szilard Kalman, Gyula M. Szabo, Luca Borsato, Attila Bodi, Andras Pal, Robert Szabo
Summary: The recent confirmation of several exoplanets residing in the "sub-Jovian/Neptune desert" has transformed it into a "savanna" with "giraffe" planets like LTT 9779 b and TOI-674 b. This article emphasizes the importance of studying these processes and presents three specific targets for observing them in the infrared range, which could improve our understanding of planetary formation/evolution.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
J. M. Benko, E. Plachy, H. Netzel, A. Bodi, L. Molnar, A. Pal
Summary: Using TESS space telescope data, we investigated the time series of 633 RR Lyrae stars and found that 82.8% of them have additional frequencies beyond the main pulsation. The additional frequencies may belong to non-radial modes, particularly l=10 modes. Stars with shorter periods tend to have no additional frequencies, while longer period stars almost always show additional frequencies. The incidence rate and period distribution match well with recent theoretical models. Amplitude and phase of additional frequencies vary over time, and different non-radial modes have different time-scale variations. We also observed the Blazhko effect in 10.4% of the stars and detected annual-scale phase changes without significant amplitude variation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Gabor B. Kovacs, Janos Nuspl, Robert Szabo
Summary: Despite the development of two- and three-dimensional models, numerical hydrocodes used for modeling stellar pulsations still rely on simplified one-dimensional stellar envelope models. This study compares two one-dimensional numerical codes with observations of radial-velocity of RRab stars and determines the undetermined convective parameters. The results show temperature dependence of some parameters and degeneracy between parameters, providing suggestions for the widely used RSP code in the MESA package.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)