TY - JOUR AU - Kriskovics, Levente AU - Kővári, Zsolt AU - Seli, Bálint Attila AU - Oláh, Katalin Ilona AU - Vida, Krisztián AU - Henry, G. W. AU - Granzer, T. AU - Görgei, A. TI - EI Eridani: A star under the influence. The effect of magnetic activity in the short and long term JF - ASTRONOMY & ASTROPHYSICS J2 - ASTRON ASTROPHYS VL - 674 PY - 2023 SN - 0004-6361 DO - 10.1051/0004-6361/202245767 UR - https://m2.mtmt.hu/api/publication/34053151 ID - 34053151 N1 - Funding Agency and Grant Number: Hungarian National Research, Development and Innovation Office [OTKA K-131508, KKP-143986, 2019-2.1.11-TeT-2019-00056]; Bolyai+ [UNKP-22-5-ELTE-1093]; DNew National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund; NASA; NSF; State of Tennessee through its Centers of Excellence Program Funding text: The authors would like to thank Albert Washuettl and the original MUSICOS team for organizing and gathering the data used in this work. The authors acknowledge the Hungarian National Research, Development and Innovation Office grants OTKA K-131508, KKP-143986 (Elvonal), and 2019-2.1.11-TeT-2019-00056. L.K. acknowledges the Hungarian National Research, Development and Innovation Office grant OTKA PD-134784. L.K. and K.V. are Bolyai Janos research Fellows. K.V. is supported by the Bolyai+ grant UNKP-22-5-ELTE-1093, BS is supported by the UNKP-22-3 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund. G.W.K. acknowledges long-term support from NASA, NSF, and the State of Tennessee through its Centers of Excellence Program. AB - Context. Homogeneous photometric time series spanning decades provide a unique opportunity to study the long-term cyclic behavior of active spotted stars such as our target EI Eridani. In addition, with ultraprecise space photometry data, it is possible to investigate the accompanying flare activity in detail. However, the rotation period of ≈2 days for EI Eri makes it impossible to achieve time-resolved surface images from a single ground-based observing site. Therefore, for this purpose, spectroscopic data from a multi-site observing campaign are needed. LA - English DB - MTMT ER - TY - JOUR AU - Oláh, Katalin Ilona AU - Seli, Bálint Attila AU - Kővári, Zsolt AU - Kriskovics, Levente AU - Vida, Krisztián TI - Characteristics of flares on giant stars JF - ASTRONOMY & ASTROPHYSICS J2 - ASTRON ASTROPHYS VL - 668 PY - 2022 SN - 0004-6361 DO - 10.1051/0004-6361/202243789 UR - https://m2.mtmt.hu/api/publication/33538419 ID - 33538419 N1 - Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly Thege Miklós út 15-17, Budapest, 1121, Hungary Csfk, Mta Centre of Excellence, Budapest, Konkoly Thege Miklós út 15-17, Budapest, 1121, Hungary Eötvös University, Department of Astronomy, Pf. 32, Budapest, 1518, Hungary Cited By :1 Export Date: 13 October 2023 CODEN: AAEJA AB - Context. Although late-type dwarfs and giant stars are substantially different, their flares are thought to originate in similar physical processes and differ only by a scale factor in the energy levels. We study the validity of this approach. LA - English DB - MTMT ER - TY - CONF AU - Seli, Bálint Attila AU - Van Driel Gesztelyi, Lídia AU - Baker, Deborah AU - Laming, J. Martin AU - Kővári, Zsolt AU - Oláh, Katalin Ilona AU - Kriskovics, Levente AU - Vida, Krisztián AU - Balázs, Lajos TI - Stellar FIP effect from the empirical side T2 - 44th COSPAR Scientific Assembly. Held 16-24 July PY - 2022 UR - https://m2.mtmt.hu/api/publication/33087071 ID - 33087071 AB - The difference between the elemental abundances of the corona and the photosphere is an apparently common feature of stellar atmospheres. The abundance difference depends on the first ionization potential of the given element, so the phenomenon is known as the FIP effect. Here we explore the variation of the strength of the FIP effect for different types of stars, through the FIP bias parameter. Using a sample of 59 main sequence and evolved stars with known coronal abundances from the literature, we look for macroscopic, measurable parameters that affect the stellar FIP bias, and also re-evaluate the simple dependence on the effective temperature. LA - English DB - MTMT ER - TY - JOUR AU - Günther, Maximilian N. AU - Berardo, David A. AU - Ducrot, Elsa AU - Murray, Catriona A. AU - Stassun, Keivan G. AU - Oláh, Katalin Ilona AU - Bouma, L. G. AU - Rappaport, Saul AU - Winn, Joshua N. AU - Feinstein, Adina D. AU - Matthews, Elisabeth C. AU - Sebastian, Daniel AU - Rackham, Benjamin V. AU - Seli, Bálint Attila AU - Triaud, Amaury H. M. J. AU - Gillen, Edward AU - Levine, Alan M. AU - Demory, Brice-Olivier AU - Gillon, Michaël AU - Queloz, Didier AU - Ricker, George R. AU - Vanderspek, Roland K. AU - Seager, Sara AU - Latham, David W. AU - Jenkins, Jon M. AU - Brasseur, C. E. AU - Colón, Knicole D. AU - Daylan, Tansu AU - Delrez, Laetitia AU - Fausnaugh, Michael AU - Garcia, Lionel J. AU - Jayaraman, Rahul AU - Jehin, Emmanuel AU - Kristiansen, Martti H. AU - Kruijssen, J. M. Diederik AU - Pedersen, Peter Pihlmann AU - Pozuelos, Francisco J. AU - Rodriguez, Joseph E. AU - Wohler, Bill AU - Zhan, Zhuchang TI - Complex Modulation of Rapidly Rotating Young M Dwarfs: Adding Pieces to the Puzzle JF - ASTRONOMICAL JOURNAL J2 - ASTRON J VL - 163 PY - 2022 IS - 4 SN - 0004-6256 DO - 10.3847/1538-3881/ac503c UR - https://m2.mtmt.hu/api/publication/32732997 ID - 32732997 N1 - Department of Physics, Kavli Institute for Astrophysics and Space Research, Mit, 77 Massachusetts Avenue, Cambridge, MA 02139, United States European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Keplerlaan 1, Noordwijk, 2201 AZ, Netherlands Astrobiology Research Unit, Université de Liège, 19C Allée du 6 Aout, Liège, B-4000, Belgium Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, United States Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungary Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, United States Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Avenue, Chicago, IL 60637, United States Department of Earth, Atmospheric and Planetary Sciences, Mit, 77 Massachusetts Avenue, Cambridge, MA 02139, United States School of Physics and Astronomy, University of Birmingham, Birmingham, Edgbaston, B15 2TT, United Kingdom Astronomy Unit, Queen Mary University of London, Mile End Road, London, E1 4NS, United Kingdom University of Bern, Center for Space and Habitability, Bern, Switzerland Observatoire Astronomique de l'Université de Genève, 51 chemin de Pégase, Sauverny, 1290, Switzerland Department of Aeronautics and Astronautics, Mit, 77 Massachusetts Avenue, Cambridge, MA 02139, United States Center for Astrophysics Harvard and Smithsonian, 60 Garden Street, Cambridge, MA 02138, United States Nasa Ames Research Center, Moffett FieldCA 94035, United States Mikulski Archive for Space Telescopes, United States Nasa Goddard Space Flight Center, Exoplanets and Stellar Astrophysics Laboratory (Code 667), Greenbelt, MD 20771, United States Space Sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, 19C Allée du 6 Aout, Liège, B-4000, Belgium Brorfelde Observatory, Observator Gyldenkernes Vej 7DK-4340, Denmark Dtu Space, National Space Institute, Technical University of Denmark, Elektrovej 327, Lyngby, DK-2800, Denmark Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, Heidelberg, D-69120, Germany Seti Institute/NASA Ames Research Center, United States Cited By :1 Export Date: 29 June 2022 Correspondence Address: Günther, M.N.; Department of Physics, 77 Massachusetts Avenue, United States; email: maximilian.guenther@esa.int Funding details: T010920F Funding details: KR4801/2-1 Funding details: National Science Foundation, NSF, DGE-1746045 Funding details: National Aeronautics and Space Administration, NASA, NAS 5-26555 Funding details: Simons Foundation, SF Funding details: Automotive Research Center, ARC Funding details: Horizon 2020 Framework Programme, H2020, 714907, 803193/BEBOP Funding details: Seventh Framework Programme, FP7, FP/2007–2013 Funding details: Heising-Simons Foundation, HSF Funding details: Engineering Research Centers, ERC, 336480 Funding details: Science and Technology Facilities Council, STFC, ST/S00193X/1 Funding details: European Research Council, ERC Funding details: European Space Agency, ESA Funding details: Deutsche Forschungsgemeinschaft, DFG, KR4801/1-1 Funding details: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, SNF, PP00P2-163967 Funding details: Nemzeti Kutatási Fejlesztési és Innovációs Hivatal, NKFIH, OTKA K131508 Funding details: Fondation Merac, MERAC Funding details: Innovációs és Technológiai Minisztérium Funding text 1: M.N.G. acknowledges support from MIT’s Kavli Institute as a Juan Carlos Torres Fellow and from the European Space Agency (ESA) as an ESA Research Fellow. K.O. and B.S. acknowledge support from the Hungarian National Research, Development and Innovation Office grant OTKA K131508. B.S. is supported by the ÚNKP-19-3 New National Excellence Program of the Ministry for Innovation and Technology. J.N.W. and B.V.R. thank the Heising-Simons Foundation for support. A.D.F. acknowledges the support from the National Science Foundation Graduate Research Fellowship Program under grant No. (DGE-1746045). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. E.G. gratefully acknowledges support from the David and Claudia Harding Foundation in the form of a Winton Exoplanet Fellowship. M.G. is F.R.S.-FNRS Senior Research Associate. B.-O.D. acknowledges support from the Swiss National Science Foundation (PP00P2-163967). J.M.D.K. gratefully acknowledges funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through an Emmy Noether Research Group (grant number KR4801/1-1), the DFG Sachbeihilfe (grant number KR4801/2-1), and the SFB 881 “The Milky Way System” (subproject B2), as well as from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program via the ERC Starting Grant MUSTANG (grant agreement number 714907). Funding text 2: Funding for the TESS mission is provided by NASA’s Science Mission directorate. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013) ERC Grant Agreement n° 336480, from the European Union’s Horizon 2020 research and innovation program (grant agreement n° 803193/BEBOP), from the ARC grant for Concerted Research Actions financed by the Wallonia-Brussels Federation, from the Balzan Prize Foundation, from F.R.S-FNRS (Research Project ID T010920F), from the Simons Foundation, from the MERAC foundation, and from STFC, under grant number ST/S00193X/1. This work has made use of data from the European Space Agency (ESA) mission Gaia ( https://www.cosmos.esa.int/gaia ), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium ). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. LA - English DB - MTMT ER - TY - JOUR AU - Seli, Bálint Attila AU - Oláh, Katalin Ilona AU - Kriskovics, Levente AU - Kővári, Zsolt AU - Vida, Krisztián AU - Balázs, Lajos AU - Laming, J. M. AU - Van Driel Gesztelyi, Lídia AU - Baker, D. TI - Extending the FIP bias sample to magnetically active stars JF - ASTRONOMY & ASTROPHYSICS J2 - ASTRON ASTROPHYS VL - 659 PY - 2022 SN - 0004-6361 DO - 10.1051/0004-6361/202141493 UR - https://m2.mtmt.hu/api/publication/32726535 ID - 32726535 N1 - Konkoly Observatory, Research Centre for Astronomy and Earth Sciences (ELKH), Budapest, Hungary Eotvos University, Department of Astronomy, Pf. 32, Budapest, 1518, Hungary Space Science Division, Code 7684, Naval Research Laboratory, Washington, DC 20375, United States University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Surrey, RH5 6NT, United Kingdom LESIA, Observatoire de Paris, Universite PSL, CNRS, Sorbonne Universite, Univ. Paris Diderot, Sorbonne Paris Cite, 5 place Jules Janssen, Meudon, 92195, France Export Date: 29 June 2022 CODEN: AAEJA Correspondence Address: Seli, B.; Konkoly Observatory, Hungary; email: seli.balint@csfk.org Funding details: 101öu13, 104öu2, NKFIH PD-134784 Funding details: Office of Naval Research, ONR Funding details: National Aeronautics and Space Administration, NASA, 80HQTR19T0029, 80HQTR20T0076 Funding details: Science and Technology Facilities Council, STFC, ST/S000240/1 Funding details: Hungarian Scientific Research Fund, OTKA, 2019-2.1.11-TÉT-2019-00056, K-131508, K129249, KH-130526, NN129075 Funding details: Nemzeti Kutatási Fejlesztési és Innovációs Hivatal, NKFIH Funding text 1: cA knolw edgements. We thank the referee for the useful suggestion concerning the connection between the (I)FIP and the heating of the stellar coronae. Konkoly Observatory, Budapest, Hungary hosted two workshops on Elemental Composition in Solar and Stellar Atmospheres (IFIPWS-1, 13-15 Feb, 2017 and IFIPWS-2, 27 Feb-1 Mar, 2018). The workshops have fostered collaboration by exploiting synergies in solar and stellar magnetic activity studies and exchanging experience and knowledge in both research fields. We thank G. Csörnyei for the useful discussions and enlightening ideas regarding statistical methods. This work was supported by the Hungarian National Research, Development and Innovation Office grants NKFIH (OTKA) K-131508, KH-130526, NN129075, K129249 and by the NKFIH grant 2019-2.1.11-TÉT-2019-00056. Authors acknowledge the financial support of the Austrian-Hungarian Action Foundation (101öu13, 104öu2). L.K. acknowledges the financial support of the Hungarian National Research, Development and Innovation Office grant NKFIH PD-134784. L.K. is a Bolyai János Research Fellow. J.M.L. was supported by the NASA Heliophysics Guest Investigator (80HQTR19T0029) and Supporting Research (80HQTR20T0076) programs, and by Basic Research FUnds of the Office of Naval Research. D.B. is funded under STFC consolidated grant number ST/S000240/1 and LvDG is partially funded under the same grant. Software: python (Van Rossum & Drake 2009), matplotlib (Hunter 2007), numpy (van der Walt et al. 2011), scipy (Virtanen et al. 2020), pandas (McKinney 2010), sklearn (Pedregosa et al. 2011). AB - Context. The different elemental abundances of the photosphere and the corona are striking features of not only the Sun, but of other stars as well. This phenomenon is known as the first ionisation potential (FIP) effect, and its strength can be characterized by the FIP bias, the logarithmic abundance difference between low- and high-FIP elements in the corona, compared to the photosphere. The FIP bias was shown to depend on the surface temperature of the star. Aims: We aim to extend the Teff−FIP bias relationship to a larger stellar sample and analyse the effect of other astrophysical parameters on the relation (e.g. surface gravity, age, activity indicators). Methods: We compiled FIP bias and other parameters for 59 stars for which coronal composition is available, now including evolved stars. Using principal component analysis and linear discriminant analysis, we searched for correlations with other astrophysical parameters within the sample that may influence the stellar FIP bias. Results: Adding stars to the Teff−FIP bias diagram unveiled new features in its structure. In addition to the previously known relationship, there appears to be a second branch: a parallel sequence about 0.5 dex above it. While the Teff remains the main determinant of the FIP bias, other parameters such as stellar activity indicators also have influence. We find three clusters in the FIP bias determinant parameter space. One distinct group is formed by the evolved stars. Two groups contain main sequence stars in continuation separated roughly by the sign change of the FIP-bias value. Conclusions: The new branch of the Teff−FIP bias diagram contains stars with higher activity level, in terms of X-ray flux and rotational velocity. The Rossby number also seems to be important, indicating possible dependence on the type of dynamo operating in these stars influencing their FIP bias. The two main-sequence clusters run from the earliest spectral types of A-F with shallow convection zones through G-K-early-M stars with gradually deeper convection zones, and they end with the fully convective M dwarf stars, depicting the change of the dynamo type with the internal differences of the main sequence stars in connection with the FIP-bias values. LA - English DB - MTMT ER - TY - JOUR AU - Kővári, Zsolt AU - Kriskovics, Levente AU - Oláh, Katalin Ilona AU - Odert, P. AU - Leitzinger, M. AU - Seli, Bálint Attila AU - Vida, Krisztián AU - Borkovits, Tamás AU - Carroll, T. TI - A confined dynamo: Magnetic activity of the K-dwarf component in the pre-cataclysmic binary system V471 Tauri JF - ASTRONOMY & ASTROPHYSICS J2 - ASTRON ASTROPHYS VL - 650 PY - 2021 SN - 0004-6361 DO - 10.1051/0004-6361/202140707 UR - https://m2.mtmt.hu/api/publication/32106991 ID - 32106991 N1 - Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly Thege út 15-17, Budapest, 1121, Hungary Institute of Physics/IGAM, University of Graz, Universitätsplatz 5, Graz, 8010, Austria Baja Astronomical Observatory of University of Szeged, Szegedi út, Kt. 766, Baja, 6500, Hungary Leibniz-Institute for Astrophysics (AIP), An der Sternwarte 16, Potsdam, 14482, Germany Cited By :4 Export Date: 12 May 2023 CODEN: AAEJA Correspondence Address: Kriskovics, L.; Konkoly Observatory, Konkoly Thege út 15-17, Hungary; email: kovari@konkoly.hu AB - Context. Late-type stars in close binary systems can exhibit strong magnetic activity owing to rapid rotation supported by tidal locking. On the other hand, tidal coupling may suppress the differential rotation which is a key ingredient of the magnetic dynamo. Aims: We studied the red dwarf component in the eclipsing binary system V471 Tau in order to unravel the relations between the different activity layers, from the stellar surface through the chromosphere up to the corona. Our aim is to study how the magnetic dynamo in the late-type component is affected by the close white dwarf companion. Methods: We used space photometry, high-resolution spectroscopy, and X-ray observations from different space instruments to explore the main characteristics of magnetic activity. We applied a light curve synthesis program to extract the eclipsing binary model and to analyze the residual light variations. Photometric periods were obtained using a Fourier-based period search code. We searched for flares by applying an automated flare detection code. Spectral synthesis was used to derive or specify some of the astrophysical parameters. Doppler imaging was used to reconstruct surface temperature maps, which were cross-correlated to derive surface differential rotation. We applied different conversion techniques to make it possible to compare the X-ray emissions obtained from different space instruments. Results: From the K2 photometry we found that 5-10 per cent of the apparent surface of the red dwarf is covered by cool starspots. From seasonal photometric period changes we estimated a weak differential rotation. From the flare activity we derived a cumulative flare frequency diagram which suggests that frequent flaring could have a significant role in heating the corona. Using high-resolution spectroscopy we reconstructed four Doppler images for different epochs which reveal an active longitude, that is, a permanent dominant spot facing the white dwarf. From short term changes in the consecutive Doppler images we derived a weak solar-type surface differential rotation with αDR = 0.0026 shear coefficient, similar to that provided by photometry. The long-term evolution of X-ray luminosity reveals a possible activity cycle length of ≈12.7 yr, traces of which were also discovered in the Hα spectra. Conclusions: We conclude that the magnetic activity of the red dwarf component in V471 Tau is strongly influenced by the close white dwarf companion. We confirm the presence of a permanent dominant spot (active longitude) on the red dwarf facing the white dwarf. The weak differential rotation of the red dwarf is very likely the result of tidal confinement by the companion. We find that the periodic appearance of the inter-binary Hα emission from the vicinity of the inner Lagrangian point is correlated with the activity cycle. LA - English DB - MTMT ER - TY - JOUR AU - Seli, Bálint Attila AU - Vida, Krisztián AU - Moór, Attila AU - Pál, András AU - Oláh, Katalin Ilona TI - Activity of TRAPPIST-1 analog stars observed with TESS JF - ASTRONOMY & ASTROPHYSICS J2 - ASTRON ASTROPHYS VL - 650 PY - 2021 PG - 19 SN - 0004-6361 DO - 10.1051/0004-6361/202040098 UR - https://m2.mtmt.hu/api/publication/32100131 ID - 32100131 N1 - Funding Agency and Grant Number: New National Excellence Program of the Ministry for Innovation and Technology [UNKP-19-3]; Bolyai Janos Research Scholarship of the Hungarian Academy of SciencesHungarian Academy of Sciences; Lendulet Program of the Hungarian Academy of Sciences [LP2018-7/2019]; NKFINational Research, Development & Innovation Office (NRDIO) - Hungary [KH-130526, K-131508, 2019-2.1.11-TET-2019-00056]; Hungarian OTKAOrszagos Tudomanyos Kutatasi Alapprogramok (OTKA) [119993]; Austrian-Hungarian Action Foundation [95ou3, 98ou5, 101ou13]; NASA Explorer ProgramNational Aeronautics & Space Administration (NASA) Funding text: The authors would like to thank the anonymous referee for improving the quality of the paper with helpful comments and suggestions. BS was supported by the UNKP-19-3 New National Excellence Program of the Ministry for Innovation and Technology. KV was supported by the Bolyai Janos Research Scholarship of the Hungarian Academy of Sciences. This project has been supported by the Lendulet Program of the Hungarian Academy of Sciences, project No. LP2018-7/2019, the NKFI KH-130526 and NKFI K-131508 grants, the Hungarian OTKA Grant No. 119993 and by the NKFI grant 2019-2.1.11-TET-2019-00056. On behalf of "Analysis of space-borne photometric data" project we thank for the usage of MTA Cloud (https://cloud.mta.hu) that helped us achieving the results published in this paper. Authors acknowledge the financial support of the Austrian-Hungarian Action Foundation (95ou3, 98ou5, 101ou13). This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. This research has benefitted from the Ultracool RIZzo Spectral Library (http://dx.doi.org/10.5281/zenodo.11313), maintained by Jonathan Gagne and Kelle Cruz. AB - As more exoplanets are being discovered around ultracool dwarfs, understanding their magnetic activity and the implications for habitability is of prime importance. To find stellar flares and photometric signatures related to starspots, continuous monitoring is necessary, which can be achieved with spaceborne observatories such as the Transiting Exoplanet Survey Satellite (TESS). We present an analysis of TRAPPIST-1 analog ultracool dwarfs with TESS full-frame image photometry from the first two years of the primary mission. A volume-limited sample up to 50 pc is constructed consisting of 339 stars closer than 0.(m)5 to TRAPPIST-1 on the Gaia color-magnitude diagram. We analyzed the 30 min cadence TESS light curves of 248 stars, searching for flares and rotational modulation caused by starspots. The composite flare frequency distribution of the 94 identified flares shows a power-law index that is similar to TRAPPIST-1 and contains flares up to E-TESS=3x10(33) erg. Rotational periods shorter than 5(d) were determined for 42 stars, sampling the regime of fast rotators. The ages of 88 stars from the sample were estimated using kinematic information. A weak correlation between rotational period and age is observed, which is consistent with magnetic braking. LA - English DB - MTMT ER - TY - CONF AU - Kővári, Zsolt AU - Oláh, Katalin Ilona AU - Günther, M. N. AU - Vida, Krisztián AU - Kriskovics, Levente AU - Seli, Bálint Attila TI - KIC 2852961 – a superflaring red monster in the Kepler field T2 - The 20.5th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (CS20.5) PY - 2021 DO - 10.5281/zenodo.4555348 UR - https://m2.mtmt.hu/api/publication/32079892 ID - 32079892 N1 - Poszter AB - Superflares on giant stars have up to 100,000 times more energy than the high energy solar flares. However, it is disputed, whether scaling up a solar-type dynamo could explain such a magnitude difference. We investigate the flaring activity of KIC 2852961, a late-type spotted giant. We seek for flares in the Kepler Q0-Q17 datasets by an automated technique together with visual inspection. Flare occurence rate and flare energies are analyzed and compared to flare statistics of different targets with similar flare activity at different energy levels. We find that the flare energy distribution of KIC 2852961 does not seem to be consistent with that of superflares on solar-type stars. Also, we believe that in case of KIC 2852961 spot activity should have an important role in producing such superflares. LA - English DB - MTMT ER - TY - CONF AU - Seli, Bálint Attila AU - Vida, Krisztián AU - Moór, Attila AU - Pál, András AU - Oláh, Katalin Ilona TI - Activity of TRAPPIST-1 analogue stars observed with TESS T2 - The 20.5th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (CS20.5) PY - 2021 DO - 10.5281/zenodo.4566167 UR - https://m2.mtmt.hu/api/publication/32079884 ID - 32079884 N1 - Poszter AB - We present an analysis of TRAPPIST-1 like ultracool dwarfs with TESS full-frame image photometry from the first two years of the primary mission. We constructed a volume-limited sample up to 50 pc, consisting of stars in the vicinity of TRAPPIST-1 on the Gaia color-magnitude diagram. We searched for flares and rotational modulation on the light curves of 248 stars. We determined rotational periods for 42 stars, and estimated the ages of 88 stars using kinematic information. A weak correlation between rotational period and age is observed. The composite flare frequency distribution shows a power-law index similar to TRAPPIST-1, and it is extended to higher energies. The results imply that while superflares can be expected every few decades, the flare rate of such stars is insufficient to fully destroy the possible ozone layer of orbiting planets. LA - English DB - MTMT ER - TY - JOUR AU - Oláh, Katalin Ilona AU - Kővári, Zsolt AU - Günther, M. N. AU - Vida, Krisztián AU - Gaulme, P. AU - Seli, Bálint Attila AU - Pál, András TI - Toward the true number of flaring giant stars in the Kepler field: Are their flaring specialities associated with their being giant stars? JF - ASTRONOMY & ASTROPHYSICS J2 - ASTRON ASTROPHYS VL - 647 PY - 2021 SN - 0004-6361 DO - 10.1051/0004-6361/202039674 UR - https://m2.mtmt.hu/api/publication/31922644 ID - 31922644 N1 - Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Budapest, Hungary Department of Physics, Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, United States Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany Eötvös Loránd University, Department of Astronomy, Budapest, Hungary Cited By :5 Export Date: 12 May 2023 CODEN: AAEJA Correspondence Address: Oláh, K.; Konkoly Observatory, Hungary; email: Olah@konkoly.hu LA - English DB - MTMT ER -