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
Guojie Feng, Ali Esamdin, Jianning Fu, Yanping Zhang, Hubiao Niu, Chunqian Li, Nian Liu, Tianqi Cang, Raul Michel, Lester Fox-Machado, Liang Wang, Qingfeng Pi, Chunhai Bai, Jing Xu, Abdusamatjan Iskandar, Xiangyun Zeng, Lu Ma
Summary: New multicolour photometric observations and high- and low-resolution spectroscopic observations were conducted on the eclipsing binary HIP 7666, providing the stellar physical parameters and estimated ages. The primary component has evolved to the late stages while the secondary component remains in the early main sequence stage. Frequency analysis suggests that the primary component is most likely a non-radial delta Scuti oscillator.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
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
G. Mathys, V. Khalack, O. Kobzar, F. LeBlanc, P. L. North
Summary: We report on a unique combination of rare properties observed in HD 213258, an Ap star. Through our study, we confirmed that HD 213258 is an Ap star with a resolved magnetically split spectrum and a stable magnetic field modulus over a span of 2 years. Additionally, it exhibits high overtone pulsations and has a mean radial velocity exceeding that of at least 99% of Ap stars. This exceptional combination of properties makes HD 213258 an interesting object deserving of further detailed study.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Guillermo Torres
Summary: The study reveals that the pulsation period of Polaris is becoming shorter, and the amplitude of the velocity variations has stopped increasing and may be getting smaller again. The changes in pulsation behavior over the past century seem to be related to the binary nature of the system, suggesting that the companion may be perturbing the atmosphere of the Cepheid and altering its pulsation properties.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
T. R. Shutt, E. Brunsden, K. R. Pollard
Summary: Following frequency and mode identification of two candidate gamma Doradus stars, HD 103257 and HD 109799, both were confirmed to belong to the class. High-resolution spectra and high-quality photometry data proved to be effective in supporting frequency and mode analysis.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
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
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
K. Woodcock, G. A. Wade, O. Kochukhov, J. Sikora, A. Pigulski
Summary: Using spectropolarimetric observations, a slightly eccentric orbit with a strong magnetic field in the primary of tau(9)Eri was identified. The Bp star exhibits a clear rotation period of 3.82 days and g-mode pulsations, indicating a complex binary system with distinct characteristics.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Luca Zampieri, Giampiero Naletto, Aleksandr Burtovoi, Michele Fiori, Cesare Barbieri
Summary: Stellar intensity interferometry is a technique that measures the second-order spatial correlation of light emitted from stars to determine the angular size and structure of the emitting source. An experiment at the Asiago Observatory in Italy successfully detected the temporal correlation of Vega at zero baseline and measured the correlation on a projected baseline of around 2 km, with a signal-to-noise ratio of greater than or similar to 4. This experience will help with future implementations of stellar intensity interferometry on long-baseline arrays of Cherenkov telescopes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
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
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
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
K. Brogaard, F. Grundahl, E. L. Sandquist, D. Slumstrup, M. L. Jensen, J. B. Thomsen, J. H. Jorgensen, J. R. Larsen, S. T. Bjorn, C. T. G. Sorensen, H. Bruntt, T. Arentoft, S. Frandsen, J. Jessen-Hansen, J. A. Orosz, R. Mathieu, A. Geller, N. Ryde, D. Stello, S. Meibom, I. Platais
Summary: Accurate measurements of parameters of eclipsing binary members of open clusters can constrain models of stellar structure and evolution. Multiple binary stars can provide ways to improve the precision and accuracy of age estimates of host clusters. The study identified and measured properties of a non-eclipsing cluster member, V56, in NGC 6791, which further supported and strengthened previous findings by providing additional model constraints.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
E. Niemczura, P. Walczak, P. Mikolajczyk, M. Schoeller, C. A. Hummel, S. Hubrig, T. Rozanski
Summary: Photometric and spectroscopic time-series analysis of chemically peculiar HgMn stars reveals a small sample of candidates for pulsating variables. In this study, one particular star, HD 29589, was thoroughly analyzed, revealing high-temperature and typical abundance pattern. More than 20 independent frequencies were identified, interpreted as high-order g-modes. The study provides insights into the pulsation characteristics of HgMn stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
B. Fuhrmeister, S. Czesla, E. Nagel, A. Reiners, J. H. M. M. Schmitt, S. Jeffers, J. A. Caballero, D. Shulyak, E. N. Johnson, M. Zechmeister, D. Montes, A. Lopez-Gallifa, I Ribas, A. Quirrenbach, P. J. Amado, D. Galadi-Enriquez, A. P. Hatzes, M. Kuerster, C. Danielski, V. J. S. Bejar, A. Kaminski, J. C. Morales, M. R. Zapatero Osorio
Summary: In this study, we investigate the optical and near-infrared doublet lines in a sample of 324 M dwarfs. These lines serve as diagnostics for photospheric and chromospheric properties and are important for variability studies and activity diagnostics. The optical doublet lines are sensitive to activity, while the near-infrared doublet lines show little correlation with Ha activity.
ASTRONOMY & ASTROPHYSICS
(2022)
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
Daniel R. Hey, Angela Kochoska, Richard Monier, Oleg Kochukhov, Cole Johnston, Timothy R. Bedding, Simon J. Murphy, Michael Abdul-Masih, John Southworth, Mads Fredslund Andersen, Frank Grundahl, Pere L. Palle
Summary: This study analyzes the eclipsing single-lined spectroscopic binary system a Dra, determining parameters for both primary and secondary components, as well as performing an abundance analysis of the primary star for 21 chemical elements. The results provide valuable insights into the physical characteristics and chemical composition of this binary system.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
O. Kochukhov, N. Papakonstantinou, C. Neiner
Summary: This study presents a comprehensive investigation of the rotational photometric variability, binarity, magnetic field geometry, and surface chemical spot structure of the brightest magnetic chemically peculiar star phi Dra in the northern sky. The analysis reveals that the surface field structure of phi Dra is dominated by a distorted dipolar component and exhibits chemical spot geometries with enhanced concentrations of Cr, Fe, and to a lesser extent Si.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Francesco Borsa, Luca Fossati, Tommi Koskinen, Mitchell E. Young, Denis Shulyak
Summary: This study presents the first definitive detection of the oxygen 777.4nm triplet in an exoplanetary atmosphere, suggesting a high mass-loss rate and the presence of fast winds. The findings have important implications for understanding exoplanetary atmospheres.
Article
Astronomy & Astrophysics
Julian D. Alvarado-Gomez, Ofer Cohen, Jeremy J. Drake, Federico Fraschetti, Katja Poppenhaeger, Cecilia Garraffo, Judy Chebly, Ekaterina Ilin, Laura Harbach, Oleg Kochukhov
Summary: Two close-in planets have been recently discovered around the M-dwarf flare star AU Microscopii, making it an important system for studying atmospheric loss on exoplanets. Numerical modeling and simulations were conducted to investigate the stellar wind and coronal mass ejection events in this system. The results predict extreme space weather conditions for AU Mic and its planets, posing a significant challenge for the survival of exoplanetary atmospheres in this system.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
M. E. Shultz, S. P. Owocki, A. ud-Doula, A. Biswas, D. Bohlender, P. Chandra, B. Das, A. David-Uraz, V Khalack, O. Kochukhov, J. D. Landstreet, P. Leto, D. Monin, C. Neiner, Th Rivinius, G. A. Wade
Summary: Numerous magnetic hot stars exhibit gyrosynchrotron radio emission, and the radio luminosity is strongly dependent on rotation. By collecting and analyzing a large amount of data, it is found that there is a clear correlation between radio emission and rotation, and there is a close correlation between H alpha emission strength and radio luminosity. These results suggest that radio emission and H alpha emission may be produced by different mechanisms in centrifugal magnetospheres.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Travis S. Metcalfe, Adam J. Finley, Oleg Kochukhov, Victor See, Thomas R. Ayres, Keivan G. Stassun, Jennifer L. van Saders, Catherine A. Clark, Diego Godoy-Rivera, Ilya V. Ilyin, Marc H. Pinsonneault, Klaus G. Strassmeier, Pascal Petit
Summary: The rotation rates of main-sequence stars slow over time due to the loss of angular momentum to magnetized stellar winds. This phenomenon is influenced by various factors such as the strength and morphology of the magnetic field, mass-loss rate, and stellar properties. Observations of different stars reveal a transition in magnetic morphology and a decrease in the rate of angular momentum loss as stars age.
ASTROPHYSICAL JOURNAL LETTERS
(2022)
Article
Astronomy & Astrophysics
R. J. Dorn, P. Bristow, J. V. Smoker, F. Rodler, A. Lavail, M. Accardo, M. van den Ancker, D. Baade, A. Baruffolo, B. Courtney-Barrer, L. Blanco, A. Brucalassi, C. Cumani, R. Follert, A. Haimerl, A. Hatzes, M. Haug, U. Heiter, R. Hinterschuster, N. Hubin, D. J. Ives, Y. Jung, M. Jones, H. -u. Kaeufl, J. -p. Kirchbauer, B. Klein, O. Kochukhov, H. H. Korhonen, J. Koehler, J-l. Lizon, C. Moins, I. Molina-Conde, T. Marquart, M. Neeser, E. Oliva, L. Pallanca, L. Pasquini, J. Paufique, N. Piskunov, A. Reiners, D. Schneller, R. Schmutzer, U. Seemann, D. Slumstrup, A. Smette, J. Stegmeier, E. Stempels, S. Tordo, E. Valenti, J. J. Valenzuela, J. Vernet, J. Vinther, A. Wehrhahn
Summary: The CRIRES+ project upgraded the capabilities of the CRIRES instrument by transforming it into a cross-dispersed spectrograph, increasing the covered wavelength range by up to a factor of ten. It also included improvements such as a new spectropolarimetric unit and enhanced calibration system. The instrument was installed in early 2020 and successfully commissioned and verified for science operations in 2021.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Kim Pouilly, Oleg Kochukhov, Agnes Kospal, Axel Hahlin, Andres Carmona, Peter Abraham
Summary: The study aims to investigate the accretion and magnetic field of the tight eccentric binary system DQ Tau composed of two equal-mass CTTSs. The magnetic field topology and strengths in this system are compatible with the accretion processes on CTTSs. Both components of the system are found to be accreting, with a change of the main accretor during the orbital motion. Additionally, the system exhibits a strong enhancement of the mass accretion rate at periastron and apastron, and the apsidal motion of the orbital ellipse is discovered for the first time in this system.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
F. Yan, L. Nortmann, A. Reiners, N. Piskunov, A. Hatzes, U. Seemann, D. Shulyak, A. Lavail, A. D. Rains, D. Cont, M. Rengel, F. Lesjak, E. Nagel, O. Kochukhov, S. Czesla, L. Boldt-Christmas, U. Heiter, J. V. Smoker, F. Rodler, P. Bristow, R. J. Dorn, Y. Jung, T. Marquart, E. Stempels
Summary: We observed the dayside thermal emission spectra of WASP-18b and WASP-76b using the new CRIRES+ high-resolution spectrograph and detected strong CO emission lines, confirming the existence of temperature inversions on their dayside hemispheres. This is the first detection of CO emission lines in Ultra-hot Jupiters orbiting F-type stars. We also found weak H2O emission signals for both planets and retrieved the temperature-pressure profiles and CO volume mixing ratios.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
A. Hahlin, O. Kochukhov, A. D. Rains, A. Lavail, A. Hatzes, N. Piskunov, A. Reiners, U. Seemann, L. Boldt-Christmas, E. W. Guenther, U. Heiter, L. Nortmann, F. Yan, D. Shulyak, J. V. Smoker, F. Rodler, P. Bristow, R. J. Dorn, Y. Jung, T. Marquart, E. Stempels
Summary: This study aims to characterize the small-scale magnetic fields of 16 Sun-like stars and evaluate the capabilities of the newly upgraded near-infrared instrument CRIRES+ for small-scale magnetic field studies. Two different models were used to describe the small-scale magnetic fields, and it was found that they are correlated with the large-scale fields and are at least ten times stronger. Comparison with optical measurements showed a discrepancy two to three times stronger in the near-infrared results.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Travis S. Metcalfe, Klaus G. Strassmeier, Ilya V. Ilyin, Jennifer L. van Saders, Thomas R. Ayres, Adam J. Finley, Oleg Kochukhov, Pascal Petit, Victor See, Keivan G. Stassun, Sandra V. Jeffers, Stephen C. Marsden, Julien Morin, Aline A. Vidotto
Summary: During the first half of their main-sequence lifetimes, stars lose angular momentum rapidly through magnetic braking. Recent observations show that this process becomes less efficient when stars reach a critical value of the Rossby number. Using new spectropolarimetry measurements and reanalyzing published data, researchers find that the angular momentum loss rate drops significantly between two stars of different ages. The study provides new insights into the nature and timing of weakened magnetic braking.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
O. Kochukhov, H. Gursoytrak Mutlay, A. M. Amarsi, P. Petit, I Mutlay, B. Gurol
Summary: In this study, we observed and characterized the surface structure of 45 Her, a weak-field Ap star, to better understand the origin of magnetic fields and chemical spot formation. With the help of Zeeman Doppler imaging, we found that despite its weak magnetic field, 45 Her exhibits surface chemical inhomogeneities. We also discovered that chemical spot formation does not necessarily require strong magnetic fields and that the stellar structure and global field can remain stable for sub-100 G field strengths contrary to theoretical predictions.
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)