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
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
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
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
Albert Bruch
Summary: This study investigates the flickering strength and high-frequency spectral index of dwarf nova systems using high-cadence Kepler light curves. The findings confirm that the flickering strength remains relatively constant above a certain brightness threshold and increases at fainter magnitudes. It also reveals a hysteresis effect in both the flickering strength and spectral index, indicating a stronger flickering during the decline from outburst compared to the rise. These observations can be qualitatively explained by the disc instability model for dwarf nova outbursts.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
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
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
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
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
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)
Article
Astronomy & Astrophysics
Abid Kh Rzaev
Summary: Temporal radial velocity variations of the ion, He i, and Hβ lines in the spectrum of α Cyg are studied using about 430 CCD spectra obtained from 1998 to 2001 and in 2007. These variations are found to be caused by pulsation-type motions and have specific periods and amplitudes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Geza Kovacs, Behrooz Karamiqucham
Summary: The study focuses on the luminosities of double-mode RR Lyrae stars and compares them with data from the Gaia survey. By analyzing the parameters of these stars, it is found that there is a strong correlation between the RR Lyrae and Gaia luminosities, with a slight adjustment needed for the Gaia parallaxes to match. Additionally, the study confirms independently derived period-luminosity-metallicity relations and finds that predicted absolute magnitudes align closely within a small margin of error.
ASTRONOMY & ASTROPHYSICS
(2021)
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
A. H. Corsico, M. Uzundag, S. O. Kepler, R. Silvotti, L. G. Althaus, D. Koester, A. S. Baran, K. J. Bell, A. Bischoff-Kim, J. J. Hermes, S. D. Kawaler, J. L. Provencal, D. E. Winget, M. H. Montgomery, P. A. Bradley, S. J. Kleinman, A. Nitta
Summary: This study presents an asteroseismological analysis of six GW Vir stars using TESS data, revealing g-mode pulsations in these stars and estimating their masses based on period spacings. The results demonstrate the significant contribution of TESS, in conjunction with other space missions and ground-based observations, to the advancement of white dwarf asteroseismology.
ASTRONOMY & ASTROPHYSICS
(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
Fangfei Shi, Huawei Zhang, Jianning Fu, Donald Kurtz, Maosheng Xiang
Summary: In this study, a sample of 2700 Ap stars in the LAMOST DR9 catalog is presented. The candidates are selected based on their temperature range and the characteristic flux depression features of Ap stars. Spectral analysis and statistical analysis are carried out to determine the stellar parameters and discuss the evolutionary stages. Additionally, the rotation and pulsation features of stars with TESS or Kepler light curves are also discussed, revealing new variables and pulsation phenomena.
ASTROPHYSICAL JOURNAL
(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
Andreea Henriksen, Victoria Antoci, Hideyuki Saio, Matteo Cantiello, Hans Kjeldsen, Donald W. Kurtz, Simon J. Murphy, Savita Mathur, Rafael A. Garcia, Angela R. G. Santos
Summary: The Kepler mission discovered various types of stellar variability, including magnetic activity and oscillations. In this study, the researchers analyzed the periodic signal in 162 intermediate-mass stars, known as Rossby modes and rotational modulation. They investigated whether the rotational modulation was caused by magnetic spots or by Overstable Convective modes. The results suggest that the magnetic spots scenario is more likely to explain the observed feature, but further investigation and observations are needed to confirm this.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
V. Vanlaer, C. Aerts, E. P. Bellinger, J. Christensen-Dalsgaard
Summary: Gravity-mode pulsators have improved our understanding of mixing in intermediate mass stars. However, theoretical pulsation periods of stellar models often do not match observations, making it difficult to determine how these models should be improved. Inversions provide a way to probe the internal structure of these stars and identify areas in need of improvement. This study explores the feasibility of inversions for gravity-mode pulsators, specifically focusing on slowly rotating slowly pulsating B-type stars.
ASTRONOMY & ASTROPHYSICS
(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)
Article
Astronomy & Astrophysics
V. Hocde, R. Smolec, P. Moskalik, O. Ziolkowska, R. Singh Rathour
Summary: This study establishes new empirical relations for estimating the iron content of classical Cepheids based on Fourier parameters from the V- and I-band light curves. These relations are applied to Cepheids in the Milky Way, Small Magellanic Cloud, and Large Magellanic Cloud. The results show small errors in the V- and I-band light curves and are consistent with literature values.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Justin A. Kader, Catherine A. Pilachowski, Christian I. Johnson, R. Michael Rich, Michael D. Young, Iulia T. Simion, William I. Clarkson, Scott Michael, Andrea Kunder, Anna Katherina Vivas, Andreas J. Koch-Hansen, Tommaso Marchetti
Summary: We present wide-field, high resolution maps of the color excess for 14 globular clusters toward the Southern Galactic bulge. These maps trace interstellar extinction by dust down to 5'' scales and show residual broadening in the color-magnitude diagrams for the target globular clusters. The broadening is likely driven by star-to-star elemental abundance variations.
ASTROPHYSICAL JOURNAL
(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
D. W. Kurtz, R. Jayaraman, P. Sowicka, G. Handler, H. Saio, J. Labadie-Bartz, U. Lee
Summary: Through the study of HD 42477, we disprove the conjecture that all stars pulsating in p modes and lying in the T-eff range are due to incorrect measurements of T-eff, contamination, or the presence of unseen cooler companions in the d Sct instability strip. We find that the pulsation modes in HD 42477 are coupled to r modes and/or g modes, ruling out the possibility of background contamination and a binary companion d Sct star. We propose that the g modes are excited by overstable convective core modes, and suggest that the single p mode is driven by coupling with the g modes or by He ii ionization in the equatorial region of this rapidly rotating star.
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)
Article
Astronomy & Astrophysics
Y. El Jariri, F. L. Sefyani, A. Benhida, Z. Benkhaldoun, K. Kolenberg, K. Chafouai, A. Habib, M. Sabil
Summary: We conducted a campaign of measurements of variable star spectra at the Oukaimeden observatory since 2013 and developed a graphical interface using Python to analyze the data. The interface can represent spectroscopic data graphically and determine parameters for the study of short-period variable stars. It can also convert Fits files into text files and create Excel tables containing calculated parameters.
ASTRONOMY AND COMPUTING
(2023)
