Article
Astronomy & Astrophysics
Anastasiya D. Yarovova, Oleg Egorov, Alexei Moiseev, Olga Maryeva
Summary: We discovered an unusual emission-line stellar-like object in the low-metallicity dwarf galaxy NGC 4068, characterized by high velocity dispersion, the presence of He II lambda 4686 angstrom line, and peculiarly low [S II]/[N II] fluxes ratio. Our observations suggest that this object is a single star with high bolometric luminosity surrounded by an expanding nebula. The peculiar nitrogen overabundance in the nebula indicates interaction between the star's ejecta and the interstellar medium, possibly a massive blue supergiant or Wolf-Rayet star.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Y. D. Mayya, A. Plat, V. M. A. Gomez-Gonzalez, J. Zaragoza-Cardiel, S. Charlot, G. Bruzual
Summary: We detected the nebular He ii lambda 4686 line in 32 H ii regions in the metal-poor collisional ring galaxy Cartwheel using the MUSE data set. The I(He ii lambda 4686)/I(H beta) ratio varies from 0.004 to 0.07, with a mean value of 0.010 +/- 0.003. Ten of these H ii regions coincide with an ultra luminous X-ray (ULX) source. We investigated the physical mechanisms responsible for the ionization of He+ and found that the majority of the regions are consistent with photoionization by star clusters in their Wolf-Rayet (WR) phase.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
S. Bloot, J. R. Callingham, B. Marcote
Summary: Apep is the brightest non-thermal colliding-wind binary, with radio observations showing a steep decline in flux density at low frequencies, possibly due to free-free absorption. The light curve analysis suggests that an anisotropic wind model fits the data better than a spherical wind model, supporting the hypothesis of one of the Wolf-Rayet stars in Apep launching an anisotropic wind. Predictions indicate a 25% decrease in the 1.4 GHz flux density of Apep over the next 5 years.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
V. M. A. Gomez-Gonzalez, Y. D. Mayya, J. A. Toala, S. J. Arthur, J. Zaragoza-Cardiel, M. A. Guerrero
Summary: In this study of the interacting galaxies NGC4038/39, the analysis of VLT MUSE observations reveals up to 38 young star-forming complexes with contribution from Wolf-Rayet (WR) stars. By using templates and extinction measurements, the study quantifies and classifies the WR population in each region, finding a global WC to WN-type ratio of 1.01.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
J. L. Pledger, A. J. Sharp, A. E. Sansom
Summary: The study reveals that spatial resolution significantly impacts the inferred numbers and types of Wolf-Rayet and other massive stars in external galaxies, with a large decrease in WR detections and variations in WR subtypes mix observed as distance increases. The ability of ELT/HARMONI to undertake WR surveys is investigated, indicating that even the faintest WR stars can be detected up to 30 Mpc using adaptive optics at visible wavelengths.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Peredur M. Williams, Nidia Morrell, Konstantina Boutsia, Philip Massey
Summary: Mid-infrared photometry from the NEOWISE-R mission shows that the Wolf-Rayet star HD 38030 in the Large Magellanic Cloud experienced a dust-formation episode in 2018, which cooled in 2019-20. New spectroscopy with the MagE spectrograph revealed absorption lines indicating a companion near O9.7III-IV type, and a significant shift in the radial velocity of the C IV lambda lambda 5801-12 blend compared to previous measurements. These findings suggest that HD 38030 is a colliding-wind binary with short-lived dust formation episodes, similar to Galactic systems WR 140 and WR 19, but with longer intervals.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Felipe Navarete, Augusto Damineli, Aura E. Ramirez, Danilo F. Rocha, Leonardo A. Almeida
Summary: This study used photometric and astrometric data from Gaia Early Data Release 3 to determine the distance of Westerlund 1 star cluster as 4.06(-0.34)(+0.36) kpc and derived an age of 10.7 +/- 1 Myr for the cluster.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Rodolfo H. Barba, Roberto C. Gamen, Pablo Martin-Ravelo, Julia Arias, Nidia Morrell
Summary: WR 21a is a spectroscopic binary with massive stars. Photometric variations and tidally excited oscillations have been discovered. The orbital solution and mass estimates have been determined through modeling and measurements.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Dayi Li, Pauline Barmby
Summary: The study demonstrates the power of Gibbs point process models in analyzing the spatial distributions of objects in the star formation complexes of resolved galaxies, revealing the high correlation between GMCs and YSCCs. The spatial distribution of YSCCs exhibits a clustering pattern with a peak at about 250pc scale, mainly in regions with galactocentric distance greater than 4.5kpc. The properties of GMCs, such as galactocentric distance and mass, have a strong positive effect on the correlation strength between GMCs and YSCCs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Brian L. Flores, D. John Hillier, Luc Dessart
Summary: The spectra of Wolf-Rayet (WR) stars, caused by their radiatively driven winds, exhibit strong, broad emission lines originating from clumps formed by hydrodynamic instabilities. The volume-filling factor (VFF) approach, commonly used to model these spectra, assumes that the entire wind mass resides in optically thin clumps, which may not be valid in dense winds. To test this assumption, the 'shell' approach is applied to study line and continuum formation in the dense wind of the WN4 star, HD 50896. The results suggest that the wind of HD 50896, and possibly other WR stars, consist of small radially compressed and laterally confined clumps, indicating the need for 'broken' shells in modeling.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. Sixtos, A. Wofford, A. A. C. Sander, A. Peimbert
Summary: Observing the emission lines of star-forming galaxies can help understand the sources of He+-ionizing photons. In metal-poor starburst galaxies, the broad underlying component of nebular He II lambda 4686 is believed to come from the winds of classical Wolf-Rayet stars, specifically the WN subtype. However, our observations of HD 5980 suggest that the broad He II emission is likely contamination from the multiple-star system rather than from the WN stars. Modelling shows that the O stars in coeval stellar populations can be the main emitters of He+-ionizing radiation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Jakub Klencki, Alina Istrate, Gijs Nelemans, Onno Pols
Summary: Mass transfer in binary systems is influenced by various factors, including the metallicity of the stars involved. This study investigates the impact of metallicity on post-main sequence mass transfer, revealing the existence of two novel types of mass transfer and their implications for the evolution of stars in binary systems. The findings suggest a preference for metal-poor host galaxies for certain types of binary systems and shed light on the formation of black hole mergers.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
I Shaposhnikov, A. Cherepashchuk, A. Dodin, K. Postnov
Summary: This article presents the results of new photometric and spectroscopic observations of the WN5 + O6 binary V444 Cyg and provides a detailed analysis of existing spectroscopy and photometry. The study determined the masses and orbit sizes of the components of V444 Cyg, as well as estimated the secular increase rate of the orbital period and the stellar wind mass-loss rate from the WR star.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. Danehkar
Summary: A comprehensive spatio-kinematic analysis of the planetary nebula Abell 48 revealed a deformed elliptical toroidal shell and narrow exterior low-ionization structures. The peculiar hydrogen-deficient nucleus of this nebula requires further investigation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
G. Lenoir-Craig, I. I. Antokhin, E. A. Antokhina, N. St-Louis, A. F. J. Moffat
Summary: WR22 = HD 92740 is a bright double-line WN7h + O9III-V binary system, exhibiting a deep eclipse phenomenon during periastron passage. Models L96 and A13 are applied to analyze the optical observations, providing insights into the physical characteristics of the stars in the binary system.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
V. V. Gvaramadze, A. Y. Kniazev, O. V. Maryeva, L. N. Berdnikov
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2018)
Article
Astronomy & Astrophysics
Olga Maryeva, Gloria Koenigsberger, Oleg Egorov, Corinne Rossi, Vito Francesco Polcaro, Massimo Calabresi, Roberto F. Viotti
ASTRONOMY & ASTROPHYSICS
(2018)
Article
Astronomy & Astrophysics
Olga Maryeva, Gloria Koenigsberger, Oleg Egorov, Corinne Rossi, Vito Francesco Polcaro, Massimo Calabresi, Roberto F. Viotti
ASTRONOMY & ASTROPHYSICS
(2018)
Article
Astronomy & Astrophysics
V. V. Gvaramadze, O. V. Maryeva, A. Y. Kniazev, D. B. Alexashov, N. Castro, N. Langer, I. Y. Katkov
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2019)
Article
Multidisciplinary Sciences
Vasilii V. Gvaramadze, Goez Graefner, Norbert Langer, Olga V. Maryeva, Alexei Y. Kniazev, Alexander S. Moskvitin, Olga I. Spiridonova
Article
Astronomy & Astrophysics
Olga Maryeva, Gloria Koenigsberger, Sergey Karpov, Tatiana A. Lozinskaya, Oleg Egorov, Corinne Rossi, Massimo Calabresi, Roberto F. Viotti
ASTRONOMY & ASTROPHYSICS
(2020)
Article
Astronomy & Astrophysics
O. Maryeva, V. V. Gvaramadze, A. Y. Kniazev, L. N. Berdnikov
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
Y. R. Cochetti, M. L. Arias, M. Kraus, L. S. Cidale, A. F. Torres, A. Granada, O. V. Maryeva
Summary: The aim of this study was to investigate the evolution of disks around peculiar B stars by studying the variability of their physical properties and dynamical structure, and setting constraints on different models and disk forming mechanisms. Temporal monitoring of a sample of objects in the near infrared using spectroscopic facilities at the Gemini and Las Campanas Observatories was conducted. Variability in the hydrogen line profiles of the classical Be star 12 Vul was observed, along with the emission of (CO)-C-12 band heads, a feature not previously reported in Be stars but common in B[e] stars. Parameters to describe the (CO)-C-12 emitting region were obtained and different scenarios were proposed to explain this intriguing emission.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
M. Kourniotis, M. Kraus, O. Maryeva, M. Borges Fernandes, G. Maravelias
Summary: In this study, we use FEROS to revise the temperature and luminosity of eight hypergiants and determine their evolutionary state. The A-type stars are in their early post-main-sequence phase, while the FG-type stars exhibit enhanced atmospheric activity. Additionally, we identify important phenomena such as double-peaked emission and a mass-loss event.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
O. Maryeva, S. Karpov, A. Y. Kniazev, V. V. Gvaramadze
Summary: In this paper, the long-term variability properties of the LBV candidate MN 112 are investigated. It is found that MN 112 is a dormant LBV that has been inactive for at least a century.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Anastasiya D. Yarovova, Oleg Egorov, Alexei Moiseev, Olga Maryeva
Summary: We discovered an unusual emission-line stellar-like object in the low-metallicity dwarf galaxy NGC 4068, characterized by high velocity dispersion, the presence of He II lambda 4686 angstrom line, and peculiarly low [S II]/[N II] fluxes ratio. Our observations suggest that this object is a single star with high bolometric luminosity surrounded by an expanding nebula. The peculiar nitrogen overabundance in the nebula indicates interaction between the star's ejecta and the interstellar medium, possibly a massive blue supergiant or Wolf-Rayet star.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
O. Maryeva, K. Bicz, C. Xia, M. Baratella, P. Cechvala, K. Vida
Summary: This study identified 56 flare stars, including 8 hot B-A type objects, among confirmed members of Galactic open clusters using high-cadence photometry from the TESS mission. Flares were mainly detected in cool stars and M-type stars, with no direct correlation found between ages, rotation periods, and flaring activity.
CONTRIBUTIONS OF THE ASTRONOMICAL OBSERVATORY SKALNATE PLESO
(2021)
Review
Astronomy & Astrophysics
Olga Maryeva, Roberto F. Viotti, Gloria Koenigsberger, Massimo Calabresi, Corinne Rossi, Roberto Gualandi
Proceedings Paper
Astronomy & Astrophysics
O. V. Maryeva, E. L. Chentsov, V. P. Goranskij, V. V. Dyachenko, S. V. Karpov
STARS: FROM COLLAPSE TO COLLAPSE
(2017)
Article
Astronomy & Astrophysics
D. R. Gadelshin, G. G. Valyavin, M. V. Yushkin, E. A. Semenko, G. A. Galazutdinov, O. V. Maryeva, A. F. Valeev, Byeong-Cheol Lee
ASTROPHYSICAL BULLETIN
(2017)