TY - CHAP AU - Bódi, Attila AU - Vida, Krisztián ED - Bufano, F. ED - Riggi, S. ED - Sciacca, E. ED - Schilliro, F. TI - Finding Stellar Flares with Recurrent Deep Neural Networks T2 - 1st International Conference on Machine Learning for Astrophysics, ML4ASTRO 2022 VL - 60 PB - Springer Science+Business Media SN - 9783031341663 T3 - Astrophysics and Space Science Proceedings, ISSN 1570-6591 ; 60. PY - 2023 SP - 105 EP - 109 PG - 5 DO - 10.1007/978-3-031-34167-0_21 UR - https://m2.mtmt.hu/api/publication/34683543 ID - 34683543 N1 - Export Date: 25 February 2024; Cited By: 0; Correspondence Address: A. Bódi; Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network, Budapest, Hungary; email: bodi.attila@csfk.org LA - English DB - MTMT ER - TY - JOUR AU - Molnár, László AU - Plachy, Emese AU - Bódi, Attila AU - Pál, András AU - Joyce, Meridith AU - Kalup, Csilla AU - Johnson, C.I. AU - Dencs, Z. AU - Mészáros, Szabolcs AU - Netzel, Henryka AU - Kinemuchi, K. AU - Kollmeier, J.A. AU - Prieto, J.L. AU - Derekas, Aliz TI - To grow old and peculiar: Survey of anomalous variable stars in M80 with age determinations using K2 and Gaia JF - ASTRONOMY & ASTROPHYSICS J2 - ASTRON ASTROPHYS VL - 678 PY - 2023 PG - 23 SN - 0004-6361 DO - 10.1051/0004-6361/202346507 UR - https://m2.mtmt.hu/api/publication/34238473 ID - 34238473 N1 - Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, Konkoly Thege Miklós út 15-17, Budapest, 1121, Hungary Csfk, Mta Centre of Excellence, Konkoly Thege Miklós út 15-17, Budapest, 1121, Hungary Mta Csfk Lendület Near-Field Cosmology Research Group, Konkoly Thege Miklós út 15-17, Budapest, 1121, Hungary Elte Eötvös Loránd University, Institute of Physics and Astronomy, Pázmány Péter sétány 1/A, Budapest, 1117, Hungary Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, 21218, MD, United States Elte Eötvös Loránd University, Gothard Astrophysical Observatory, Szent Imre h. u. 112, Szombathely, 9700, Hungary MTA-ELTE Lendület Momentum Milky Way Research Group, Szombathely, Hungary Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, Versoix, 1290, Switzerland Apache Point Observatory/New Mexico State University, 2001 Apache Point Road, Sunspot, 88349, NM, United States Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, M5S 3H8, ON, Canada Núcleo de Astronomía de la Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile Millennium Institute of Astrophysics, Santiago, Chile ELKH-SZTE Stellar Astrophysics Research Group, Szegedi út, Kt. 766, Baja, 6500, Hungary Export Date: 03 November 2023; Cited By: 0; Correspondence Address: L. Molnár; Csfk, Mta Centre of Excellence, Budapest, Konkoly Thege Miklós út 15-17, 1121, Hungary; email: molnar.laszlo@csfk.org; CODEN: AAEJA LA - English DB - MTMT ER - TY - JOUR AU - Tarczay-Nehéz, Dóra AU - Molnár, László AU - Bódi, Attila AU - Szabó, Róbert TI - Testing ultralow amplitude Cepheid candidates in the Galactic disk by TESS and Gaia JF - ASTRONOMY & ASTROPHYSICS J2 - ASTRON ASTROPHYS VL - 676 PY - 2023 SN - 0004-6361 DO - 10.1051/0004-6361/202346094 UR - https://m2.mtmt.hu/api/publication/34059879 ID - 34059879 N1 - Export Date: 23 August 2023; Cited By: 0; CODEN: AAEJA AB - Ultralow amplitude (ULA) and strange mode Cepheids are thought to be pulsating variable stars that are near to or are at the edges of the classical instability strip. Until now, a few dozen such variable star candidates have been found both in the Large Magellanic Cloud and the Milky Way. For the present work, we studied six ULA Cepheid candidates in the Milky Way, identified by using CoRoT and 2MASS data. In order to identify their positions in the period--luminosity and color--magnitude diagrams, we used the Gaia DR3 parallax and brightness data of each star to calculate their reddening-free absolute magnitudes and distances. Furthermore, we calculated the Fourier parameters (e.g., period and amplitude) of the light variations based on CoRoT and TESS measurements, and established the long-term phase shifts for four out of six stars. Based on the results, we conclude that none of the six ULA Cepheid candidates are pulsating variable stars, but rather rotation-induced variable stars (rotational spotted and $\\alpha^2$~Canum Venaticorum variables) that are either bluer or fainter than Cepheids would be. LA - English DB - MTMT ER - TY - JOUR AU - Ádám, R. Z. AU - Hajdu, Tamás AU - Bódi, Attila AU - Hajdu, R. AU - Szklenár, Tamás AU - Molnár, László TI - Variable stars in the residual light curves of OGLE-IV eclipsing binaries towards the Galactic Bulge JF - ASTRONOMY & ASTROPHYSICS J2 - ASTRON ASTROPHYS VL - 674 PY - 2023 SN - 0004-6361 DO - 10.1051/0004-6361/202346006 UR - https://m2.mtmt.hu/api/publication/34059753 ID - 34059753 N1 - Funding Agency and Grant Number: SeismoLab' Elvonal grant of the Hungarian Research, Development and Innovation Office (NKFIH) [KKP-137523]; undergraduate research assistant program of Konkoly Observatory; Lenduelet Program of the Hungarian Academy of Sciences [LP2018-7] Funding text: We acknowledge with thanks the OGLE survey for collecting these long datasets. We thank the referee for their helpful comments. R. Z. Adam thanks the financial support provided by the undergraduate research assistant program of Konkoly Observatory. This project was supported by the KKP-137523 SeismoLab' Elvonal grant of the Hungarian Research, Development and Innovation Office (NKFIH) and by the Lenduelet Program of the Hungarian Academy of Sciences under project No. LP2018-7. This research has made use of NASA's Astrophysics Data System. AB - Context. The Optical Gravitational Lensing Experiment (OGLE) observed around 450 000 eclipsing binaries (EBs) towards the Galactic Bulge. Decade-long photometric observations such as these provide an exceptional opportunity to thoroughly examine the targets. However, observing dense stellar fields such as the Bulge may result in blends and contamination by close objects. Aims: We searched for periodic variations in the residual light curves of EBs in OGLE-IV and created a new catalogue for the EBs that contain `background' signals after the investigation of the source of the signal. Methods: From the about half a million EB systems, we selected those that contain more than 4000 data points. We fitted the EB signal with a simple model and subtracted it. To identify periodical signals in the residuals, we used a GPU-based phase dispersion minimisation python algorithm called cuvarbase and validated the found periods with Lomb-Scargle periodograms. We tested the reliability of our method with artificial light curves. Results: We identified 354 systems where short-period background variation was significant. In these cases, we determined whether it is a new variable or just the result of contamination by an already catalogued nearby one. We classified 292 newly found variables into EB, δ Scuti, or RR Lyrae categories, or their sub-classes, and collected them in a catalogue. We also discovered four new doubly eclipsing systems and one eclipsing multiple system with a δ Scuti variable, and modelled the outer orbits of the components. Full Tables 1, 4, B.1, and C.1 are only available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/674/A170. The photometry data for OGLE-IV EBs towards the Galactic Bulge are available at the CDS and via http://www.astrouw.edu.pl/ogle/ogle4/OCVS/blg/ecl/. LA - English DB - MTMT ER - TY - JOUR AU - Kálmán, Szilárd AU - Szabó M., Gyula AU - Borsato, Luca AU - Bódi, Attila AU - Pál, András AU - Szabó, Róbert TI - Converting the sub-Jovian desert of exoplanets to a savanna with TESS, PLATO, and Ariel JF - MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY J2 - MON NOT R ASTRON SOC VL - 522 PY - 2023 IS - 1 SP - 488 EP - 502 PG - 15 SN - 0035-8711 DO - 10.1093/mnras/stad978 UR - https://m2.mtmt.hu/api/publication/33783176 ID - 33783176 AB - There is a lack of exoplanets with sizes similar to Neptune orbiting their host stars with periods ≲3 d - hence the name 'sub-Jovian/Neptune desert'. Recently, several exoplanets have been confirmed to reside in the desert, transforming it into a 'savanna' with several 'giraffe' planets (such as LTT 9779 b and TOI-674 b). The most prominent scenarios put forward for the explanation of the formation of the desert are related to the stellar irradiation destroying the primary atmosphere of certain specific exoplanets. We aim to present three targets (LTT 9779 b, TOI-674 b, and WASP-156 b) that, when observed at wide wavelength ranges in infrared (IR), could prove the presence of these processes, and therefore improve the theories of planetary formation/evolution. We simulate and analyse realistic light curves of the selected exoplanets with PLATO/N-CAM and the three narrow-band filters of Ariel (VISPhot, FGS1, and FGS2) based on TESS observations of these targets. We improved the precision of the transit parameters of the three considered planets from the TESS data. We find that the combination of the three narrow-band filters of Ariel can yield an inner precision of ${\\lesssim}1.1\\ \\hbox{per cent}$ for the planetary radii. Data from the three telescopes together will span decades, allowing the monitoring of changes in the planetary atmosphere through radius measurements. The three selected 'giraffe' planets can be golden targets for Ariel, whereby the loss of planetary mass due to stellar irradiation could be studied with high precision, multiwavelength (spectro-)photometry. LA - English DB - MTMT ER - TY - JOUR AU - Chen, Thomas Y. AU - Annex, Andrew AU - Ali-Dib, Mohamad AU - Szabó, Róbert AU - Jackman, Caitriona M. AU - Amerstorfer, Ute V. AU - Bódi, Attila TI - Machine Learning for Planetary Science: Challenges and Opportunities JF - BULLETIN OF THE AMERICAN ASTRONOMICAL SOCIETY J2 - BULL AM ASTRON SOC VL - 55 PY - 2023 IS - 2 SN - 0002-7537 UR - https://m2.mtmt.hu/api/publication/33720992 ID - 33720992 AB - The capabilities of machine learning (ML) and deep learning (DL), subsets of artificial intelligence (AI), have enabled new opportunities in planetary science in the past decade. DL-based computer vision has automated content-based image classification, identifying and categorizing landmarks such as craters and dunes in satellite imagery. Computer vision applied to video imagery also enables motion and anomaly detection. Its use in both mission development and mission operations is well-documented, from charting mission trajectories to prioritizing novel observations. A wide range of techniques, from clustering and support vector machines (SVMs) to random forests (RFs) and convolutional neural networks (CNNs) have been utilized for planetary science. There is also emerging research harnessing generative adversarial networks (GANs) to detect and reconstruct planets. Further, domain adaptation and transfer learning have reduced computational burdens and allowed AI applications to be utilized even when available domain-specific data is scarce. Integrating ML and physics-based modeling remains a popular research question to tackle. Outstanding challenges in the application of ML to planetary science and astronomy at large include increasing the explainability of algorithms and reducing bias in training data. An additional challenge is determining whether particular research problems are more aptly approached through traditional statistical modeling or more complex ML techniques. As the quantity of astronomical data continues to increase in volume, it is crucial that computer scientists and planetary scientists collaborate to bridge siloed efforts and advance the field in a way that is coordinated and sustainable. We also encourage increased investment in programs focused around data analysis (such as in NASA's Planetary Science Division) and the development of ML-ready software and hardware. LA - English DB - MTMT ER - TY - JOUR AU - Benkő, József AU - Plachy, Emese AU - Netzel, Henryka AU - Bódi, Attila AU - Molnár, László AU - Pál, András TI - Time series analysis of bright TESS RRc stars: Additional modes, phase variations and more JF - MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY J2 - MON NOT R ASTRON SOC VL - 521 PY - 2023 IS - 1 SP - 443 EP - 462 PG - 20 SN - 0035-8711 DO - 10.1093/mnras/stad556 UR - https://m2.mtmt.hu/api/publication/33682875 ID - 33682875 AB - Using two years of data from the TESS space telescope, we have investigated the time series of 633 overtone pulsating field RR Lyrae (RRc) stars. The majority of stars (82.8 per cent) contain additional frequencies beyond the main pulsation. In addition to the frequencies previously explained by the ℓ = 8 and ℓ = 9 non-radial modes, we have identified a group of stars where the additional frequencies may belong to the ℓ = 10 non-radial modes. We found that stars with no additional frequencies are more common among stars with shorter periods, while stars with longer periods almost always show additional frequencies. The incidence rate and this period distribution both agree well with the predictions of recent theoretical models. The amplitude and phase of additional frequencies are varying in time. The frequencies of different non-radial modes appearing in a given star seem to vary on different timescales. We have determined a 10.4 per cent incidence rate for the Blazhko effect. For several stars we have detected continuous annual-scale phase change without significant amplitude variation. This type of variation offers a plausible explanation for 'phase jump' phenomenon reported in many RRc stars. The main pulsation frequency could show quasi-periodic phase and amplitude fluctuations. This fluctuation is clearly related to additional frequencies present in the star: stars with two non-radial modes show the strongest fluctuations, while stars with no such modes show no fluctuations at all. The summation of the phase fluctuation over time may explain the O-C variations that have long been known for many non-Blazhko RRc stars. LA - English DB - MTMT ER - TY - JOUR AU - Jurkovic, Mónika AU - Plachy, Emese AU - Molnár, László AU - Groenewegen, Martin A T AU - Bódi, Attila AU - Moskalik, Pawel AU - Szabó, Róbert TI - Type II and anomalous Cepheids in the Kepler K2 mission JF - MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY J2 - MON NOT R ASTRON SOC VL - 518 PY - 2023 IS - 1 SP - 642 EP - 661 PG - 20 SN - 0035-8711 DO - 10.1093/mnras/stac2957 UR - https://m2.mtmt.hu/api/publication/33561337 ID - 33561337 AB - We present the results of the analysis of Type II and anomalous Cepheids using the data from the Kepler K2 mission. The precise light curves of these pulsating variable stars are the key to study the details of their pulsation, such as the period-doubling effect or the presence of additional modes. We applied the Automated Extended Aperture Photometry (autoEAP) to obtain the light curves of the targeted variable stars which were observed. The light curves were Fourier analysed. We investigated 12 stars observed by the K2 mission, seven Type II, and five anomalous Cepheids. Among the Type II Cepheids, EPIC 210622262 shows period-doubling, and four stars have modulation present in their light curves which are different from the period-doubling effect. We calculated the high-order Fourier parameters for the short-period Cepheids. We also determined physical parameters by fitting model atmospheres to the spectral energy distributions. The determined distances using the parallaxes measured by the Gaia space telescope have limited precision below 16 mag for these types of pulsating stars, regardless if the inverse method is used or the statistical method to calculate the distances. The BaSTI evolutionary models were compared to the luminosities and effective temperatures. Most of the Type II Cepheids are modelled with low metallicity models, but for a few of them solar-like metallicity ([Fe/H] = 0.06) model is required. The anomalous Cepheids are compared to low-metallicity single stellar models. We do not see signs of binarity among our sample stars. LA - English DB - MTMT ER - TY - JOUR AU - Fiorellino, Elenonora AU - Zsidi, Gabriella AU - Kóspál, Ágnes AU - Ábrahám, Péter AU - Bódi, Attila AU - Hussain, Gaitee AU - Manara, Carlo F. AU - Pál, András TI - Accretion and Extinction Variations in the Low-mass Pre-main-sequence Binary System WX Cha JF - ASTROPHYSICAL JOURNAL J2 - ASTROPHYS J VL - 938 PY - 2022 IS - 2 PG - 14 SN - 1538-4357 DO - 10.3847/1538-4357/ac912d UR - https://m2.mtmt.hu/api/publication/33196366 ID - 33196366 AB - Light curves of young star systems show photometric variability due to different kinematic and physical processes. One of the main contributors to the photometric variability is the changing mass accretion rate, which regulates the interplay between the forming young star and the protoplanetary disk. We collected high-resolution spectroscopy in eight different epochs, as well as ground-based and space-borne multiepoch optical and infrared photometry of WX Cha, an MO binary system, with an almost edge-on disk (i = 87 degrees) in the Chamaeleon I star-forming region. Spectroscopic observations cover 72 days, the ground-based optical monitoring covers 42 days while space-borne TESS photometry extends for 56 days. The multiwavelength light curves exhibit quasi-periodic variability of 0.35-0.53 mag in the near-infrared, and of 1.3 mag in the g band. We studied the variability of selected emission lines that trace the accretion, computed the accretion luminosity and the mass accretion rate using empirical relations, and obtained values between L-acc similar to 1.6 L-circle dot - 3.2 L-circle dot and (M) over dot(acc) similar to 3.31 x 10(-7) M-circle dot yr(-1) - 7.76 x 10(-7) M-circle dot yr(-1). Our results show that WX Cha is accreting at a rate larger than what is typical for T Tauri stars in the same star-forming region with the same stellar parameters. We theorize that this is due to the higher disk mass of WX Cha than what is usual for stars with similar stellar mass and to the binary nature of the system. Daily changes in the accretion luminosity and in the extinction can explain the photometric variability. LA - English DB - MTMT ER - TY - JOUR AU - Szklenár, Tamás AU - Bódi, Attila AU - Tarczay-Nehéz, Dóra AU - Vida, Krisztián AU - Mező, György AU - Szabó, Róbert TI - Variable Star Classification with a Multiple-input Neural Network JF - ASTROPHYSICAL JOURNAL J2 - ASTROPHYS J VL - 938 PY - 2022 IS - 1 PG - 14 SN - 1538-4357 DO - 10.3847/1538-4357/ac8df3 UR - https://m2.mtmt.hu/api/publication/33174459 ID - 33174459 N1 - Konkoly Observatory, Research Centre for Astronomy and Earth Sciences (ELKH), Konkoly Thege Miklós út 15-17, Budapest, H-1121, Hungary CSFK, MTA Centre of Excellence, Konkoly Thege Miklós út 15-17, Budapest, H-1121, Hungary MTA CSFK Lendület Near-Field Cosmology Research Grou P, Konkoly Observatory, Budapest, Hungary ELTE Eötvös Loránd University, Institute of Physics, Budapest, Hungary Cited By :2 Export Date: 13 October 2023 AB - In this experiment, we created a Multiple-Input Neural Network, consisting of convolutional and multilayer neural networks. With this setup the selected highest-performing neural network was able to distinguish variable stars based on the visual characteristics of their light curves, while taking also into account additional numerical information (e.g., period, reddening-free brightness) to differentiate visually similar light curves. The network was trained and tested on Optical Gravitational Lensing Experiment-III (OGLE-III) data using all OGLE-III observation fields, phase-folded light curves, and period data. The neural network yielded accuracies of 89%-99% for most of the main classes (Cepheids, delta Scutis, eclipsing binaries, RR Lyrae stars, Type-II Cepheids), only the first-overtone anomalous Cepheids had an accuracy of 45%. To counteract the large confusion between the first-overtone anomalous Cepheids and the RRab stars we added the reddening-free brightness as a new input and only stars from the LMC field were retained to have a fixed distance. With this change we improved the neural network's result for the first-overtone anomalous Cepheids to almost 80%. Overall, the Multiple-input Neural Network method developed by our team is a promising alternative to existing classification methods. LA - English DB - MTMT ER -