@inproceedings{MTMT:34683543, title = {Finding Stellar Flares with Recurrent Deep Neural Networks}, url = {https://m2.mtmt.hu/api/publication/34683543}, author = {Bódi, Attila and Vida, Krisztián}, booktitle = {1st International Conference on Machine Learning for Astrophysics, ML4ASTRO 2022}, doi = {10.1007/978-3-031-34167-0_21}, volume = {60}, unique-id = {34683543}, year = {2023}, pages = {105-109}, orcid-numbers = {Bódi, Attila/0000-0002-8585-4544} } @article{MTMT:34238473, title = {To grow old and peculiar: Survey of anomalous variable stars in M80 with age determinations using K2 and Gaia}, url = {https://m2.mtmt.hu/api/publication/34238473}, author = {Molnár, László and Plachy, Emese and Bódi, Attila and Pál, András and Joyce, Meridith and Kalup, Csilla and Johnson, C.I. and Dencs, Z. and Mészáros, Szabolcs and Netzel, Henryka and Kinemuchi, K. and Kollmeier, J.A. and Prieto, J.L. and Derekas, Aliz}, doi = {10.1051/0004-6361/202346507}, journal-iso = {ASTRON ASTROPHYS}, journal = {ASTRONOMY & ASTROPHYSICS}, volume = {678}, unique-id = {34238473}, issn = {0004-6361}, year = {2023}, eissn = {1432-0746}, orcid-numbers = {Bódi, Attila/0000-0002-8585-4544; Mészáros, Szabolcs/0000-0001-8237-5209; Derekas, Aliz/0000-0002-6526-9444} } @article{MTMT:34059879, title = {Testing ultralow amplitude Cepheid candidates in the Galactic disk by TESS and Gaia}, url = {https://m2.mtmt.hu/api/publication/34059879}, author = {Tarczay-Nehéz, Dóra and Molnár, László and Bódi, Attila and Szabó, Róbert}, doi = {10.1051/0004-6361/202346094}, journal-iso = {ASTRON ASTROPHYS}, journal = {ASTRONOMY & ASTROPHYSICS}, volume = {676}, unique-id = {34059879}, issn = {0004-6361}, abstract = {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.}, keywords = {Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Astrophysics of Galaxies}, year = {2023}, eissn = {1432-0746}, orcid-numbers = {Tarczay-Nehéz, Dóra/0000-0003-3759-7616; Bódi, Attila/0000-0002-8585-4544; Szabó, Róbert/0000-0002-3258-1909} } @article{MTMT:34059753, title = {Variable stars in the residual light curves of OGLE-IV eclipsing binaries towards the Galactic Bulge}, url = {https://m2.mtmt.hu/api/publication/34059753}, author = {Ádám, R. Z. and Hajdu, Tamás and Bódi, Attila and Hajdu, R. and Szklenár, Tamás and Molnár, László}, doi = {10.1051/0004-6361/202346006}, journal-iso = {ASTRON ASTROPHYS}, journal = {ASTRONOMY & ASTROPHYSICS}, volume = {674}, unique-id = {34059753}, issn = {0004-6361}, abstract = {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/.}, keywords = {methods: numerical; Astrophysics - Solar and Stellar Astrophysics; techniques: photometric; binaries: close; binaries: eclipsing; stars: variables: general; Astrophysics - Astrophysics of Galaxies}, year = {2023}, eissn = {1432-0746}, orcid-numbers = {Hajdu, Tamás/0000-0001-8060-2367; Bódi, Attila/0000-0002-8585-4544} } @article{MTMT:33783176, title = {Converting the sub-Jovian desert of exoplanets to a savanna with TESS, PLATO, and Ariel}, url = {https://m2.mtmt.hu/api/publication/33783176}, author = {Kálmán, Szilárd and Szabó M., Gyula and Borsato, Luca and Bódi, Attila and Pál, András and Szabó, Róbert}, doi = {10.1093/mnras/stad978}, journal-iso = {MON NOT R ASTRON SOC}, journal = {MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY}, volume = {522}, unique-id = {33783176}, issn = {0035-8711}, abstract = {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.}, keywords = {techniques: photometric; methods: observational; Astrophysics - Earth and Planetary Astrophysics; planets and satellites: individual: LTT 9779b; planets and satellites: individual: TOI-674b; planets and satellites: individual: WASP-156b}, year = {2023}, eissn = {1365-2966}, pages = {488-502}, orcid-numbers = {Kálmán, Szilárd/0000-0003-3754-7889; Szabó M., Gyula/0000-0002-0606-7930; Bódi, Attila/0000-0002-8585-4544; Szabó, Róbert/0000-0002-3258-1909} } @article{MTMT:33720992, title = {Machine Learning for Planetary Science: Challenges and Opportunities}, url = {https://m2.mtmt.hu/api/publication/33720992}, author = {Chen, Thomas Y. and Annex, Andrew and Ali-Dib, Mohamad and Szabó, Róbert and Jackman, Caitriona M. and Amerstorfer, Ute V. and Bódi, Attila}, journal-iso = {BULL AM ASTRON SOC}, journal = {BULLETIN OF THE AMERICAN ASTRONOMICAL SOCIETY}, volume = {55}, unique-id = {33720992}, issn = {0002-7537}, abstract = {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.}, year = {2023}, orcid-numbers = {Szabó, Róbert/0000-0002-3258-1909; Bódi, Attila/0000-0002-8585-4544} } @article{MTMT:33682875, title = {Time series analysis of bright TESS RRc stars: Additional modes, phase variations and more}, url = {https://m2.mtmt.hu/api/publication/33682875}, author = {Benkő, József and Plachy, Emese and Netzel, Henryka and Bódi, Attila and Molnár, László and Pál, András}, doi = {10.1093/mnras/stad556}, journal-iso = {MON NOT R ASTRON SOC}, journal = {MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY}, volume = {521}, unique-id = {33682875}, issn = {0035-8711}, abstract = {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.}, keywords = {methods: data analysis; Astrophysics - Solar and Stellar Astrophysics; techniques: photometric; stars: oscillations; Space vehicles; asteroseismology; stars: variables: RR Lyrae}, year = {2023}, eissn = {1365-2966}, pages = {443-462}, orcid-numbers = {Benkő, József/0000-0003-3851-6603; Bódi, Attila/0000-0002-8585-4544} } @article{MTMT:33561337, title = {Type II and anomalous Cepheids in the Kepler K2 mission}, url = {https://m2.mtmt.hu/api/publication/33561337}, author = {Jurkovic, Mónika and Plachy, Emese and Molnár, László and Groenewegen, Martin A T and Bódi, Attila and Moskalik, Pawel and Szabó, Róbert}, doi = {10.1093/mnras/stac2957}, journal-iso = {MON NOT R ASTRON SOC}, journal = {MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY}, volume = {518}, unique-id = {33561337}, issn = {0035-8711}, abstract = {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.}, year = {2023}, eissn = {1365-2966}, pages = {642-661}, orcid-numbers = {Jurkovic, Mónika/0000-0002-8591-4295; Bódi, Attila/0000-0002-8585-4544; Szabó, Róbert/0000-0002-3258-1909} } @article{MTMT:33196366, title = {Accretion and Extinction Variations in the Low-mass Pre-main-sequence Binary System WX Cha}, url = {https://m2.mtmt.hu/api/publication/33196366}, author = {Fiorellino, Elenonora and Zsidi, Gabriella and Kóspál, Ágnes and Ábrahám, Péter and Bódi, Attila and Hussain, Gaitee and Manara, Carlo F. and Pál, András}, doi = {10.3847/1538-4357/ac912d}, journal-iso = {ASTROPHYS J}, journal = {ASTROPHYSICAL JOURNAL}, volume = {938}, unique-id = {33196366}, issn = {1538-4357}, abstract = {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.}, year = {2022}, eissn = {0004-637X}, orcid-numbers = {Bódi, Attila/0000-0002-8585-4544} } @article{MTMT:33174459, title = {Variable Star Classification with a Multiple-input Neural Network}, url = {https://m2.mtmt.hu/api/publication/33174459}, author = {Szklenár, Tamás and Bódi, Attila and Tarczay-Nehéz, Dóra and Vida, Krisztián and Mező, György and Szabó, Róbert}, doi = {10.3847/1538-4357/ac8df3}, journal-iso = {ASTROPHYS J}, journal = {ASTROPHYSICAL JOURNAL}, volume = {938}, unique-id = {33174459}, issn = {1538-4357}, abstract = {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.}, keywords = {Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Instrumentation and Methods for Astrophysics}, year = {2022}, eissn = {0004-637X}, orcid-numbers = {Bódi, Attila/0000-0002-8585-4544; Tarczay-Nehéz, Dóra/0000-0003-3759-7616; Szabó, Róbert/0000-0002-3258-1909} }