arXiv subjects

P. Gajdoš

Publications and source records attributed to P. Gajdoš.

8 recordsLinked to original sources

arXiv2026

DSLR times of minima of selected eclipsing binaries

We present a collection of eclipse timings of eclipsing binary stars obtained over the extended time interval 2014-2024. In all observations, a DSLR camera was used as the detector. The presented dataset contains 250 previously unpublished minima of 86 eclipsing binary systems obtained at three observing sites. The minima were determined from calibrated light curves using the phenomenological modelling approach, and their uncertainties were estimated by bootstrap resampling. The presented measurements extend the available timing coverage of the observed systems and may contribute to future studies of orbital period variations and other long-term phenomena in eclipsing binaries.

astro-ph.SR↗

arXiv2026

Aligned, Misaligned and Polar Orbits of Hot Jupiters: Measuring Spin-Orbit Angles via Doppler Tomography with HARPS-N

Although the migration of hot Jupiters is not yet fully understood, measurements of the projected spin-orbit angle λ help shed light on the processes involved. Here we present Doppler tomography of three known hot Jupiters to determine their λ orientation: HAT-P-49 b, HAT-P-57A b, and XO-3A b. Our analysis explores the impact of cross-correlation processing methods on the detectability and characterization of the planet's Doppler shadow using up to three independent routines for cross-correlation functions extraction; those being: Yabi, iSpec and IRAF. After accounting for differences among the results obtained with the various routines, we report: first, the HAT-P-49 system is a case of a hot Jupiter on a polar orbit with λ=-85.3{\pm}1.7°, second, HAT-P-57A indicates practically no deviation of the planet's projected orbit from the host's equatorial plane with λ=-0.4^{+1.4}_{-1.9}°, and third, the XO-3A system with the measured value of λ=38{+3}_{-4}° lies in between an aligned and a perpendicular orientation, which is a less populated region of the spin-orbit distribution. Our findings highlight both the diversity of spin-orbit angles among close-in giant planets and the potential discrepancies in their measurement that can arise from different approaches to constructing the cross-correlation functions.

astro-ph.EP↗

arXiv2025

Flares and superflares on the southern active binary CC Eri

Flares and CMEs are known to be the dominating high-energy phenomena on cool stars. Superflares were thoroughly investigated using broadband photometry predominantly from Kepler, K2, and TESS. Here we present a spectroscopic investigation of superflares on the very active spectroscopic binary CC~Eri. We focus on spectroscopic signatures of (super)-flares and line asymmetries with the goal to characterize superflares spectroscopically. In 70 nights of spectroscopic observations obtained at the ESO~1.52m telescope with the Echelle spectrograph PUCHEROS+ hosted by the PLATOSpec consortium we identified 31 flares from which two are superflares already from the deduced g'-band energies. We also find a broad blue-wing asymmetry occurring in the impulsive phase of another superflare which shows great potential to be a prominence eruption. For the second most luminous flare we find the largest number of excess emissions during the impulsive and gradual flare. We identify the flare to be occurring close to the stellar limb which indicates that the flare was even more energetic than derived from its g'-band and spectral line energies. We identify more than sixty spectral lines in the spectral range of 4100 and 7200Å showing excess emission during this flare. We detect continuum enhancements as well as photospheric line fillings during the flare. Generally we find that depending on the flare energy the number of spectral lines revealing excess emission increases, especially for the more energetic superflares. We therefore conclude that superflares are likely scaled-up versions of less energetic normal flares.

astro-ph.SR↗

arXiv2025

PLATOSpec: a precise spectrograph in support of space missions

The upcoming space missions that will characterize exoplanets, such as PLATO and Ariel, will collect huge amounts of data that will need to be complemented with ground-based observations. The aim of the PLATOSpec project is to perform science with an echelle spectrograph capable of measuring precise radial velocities. The main focus of the spectrograph will be to perform the initial screening and validation of exoplanetary candidates, in addition to study stellar variability. It will be possible to determine the physical properties of large exoplanets. The PLATOSpec blue-sensitive spectrograph, with a spectral range of 380 to 700\,nm and a resolving power of R=70,000, is installed on the 1.5-m telescope at the ESO La Silla Observatory in Chile. Initial results show that the radial-velocity limit given by the wavelength calibration is about 2-3 m/s. Tests on bright F-K main-sequence standard stars reveal a scatter of about 5 m/s over a few hours. The scatter over a few months is slightly higher. We demonstrate the capabilities of PLATOSpec on the mass determination of WASP-79 b and the spin-orbit alignment of WASP-62\,b via the Rossiter-McLaughlin effect. We show its possible usage on variable star research as demonstrated on the false-positive exoplanetary candidate TIC 238060327, which is proven a binary star. Investigation of line-profile variations of the roAp star alpha Cir shows that PLATOSpec can also be used for the surface mapping. Finally, we present new results on the active star UY Pic in the PLATO southern field. Our results show that PLATOSpec is a versatile spectrograph with great precision.

astro-ph.IM↗

arXiv2025

PLATOSpec's first results: planets WASP-35b and TOI-622b are on aligned orbits, and K2-237b is on a polar orbit

The spin-orbit angle between a stellar spin axis and its planetary orbital axis is a key diagnostic of planetary migration pathways, yet the mechanisms shaping the observed spin-orbit distribution remain incompletely understood. Combining the spin-orbit angle with atmospheric measurements has emerged as a powerful method of studying exoplanets that showcases the synergy between ground- and space-based observations. We present the Rossiter-McLaughlin effect measurements of the projected spin-orbit angle ($λ$) for three gaseous exoplanets using the newly commissioned PLATOSpec instrument on the E152 Telescope at La Silla Observatory. For WASP-35b, we determine $λ= 1_{-18}^{+19}$ deg, demonstrating PLATOSpec's capabilities through excellent agreement with HARPS-N literature data. We provide the first spin-orbit measurements for TOI-622b ($λ=-4 \pm 12$ deg, true spin-orbit angle $ψ= $16.1$^{+8.0}_{-9.7}$ deg), revealing an aligned orbit consistent with quiescent disc migration. For K2-237b, we find $λ= 91 \pm 7$ deg and $ψ= $90.5$^{+6.8}_{-6.2}$ deg, indicating a nearly perfect polar orbit, which suggests a history consistent with disc-free migration, contrasting previous studies inferring disc migration. TOI-622b populates a sparsely populated region of sub-Jovian planets with measured spin-orbit angles orbiting stars above the Kraft break, while K2-237b's polar configuration strengthens tentative evidence for preferential orbital orientations. All three systems are compelling targets for future atmospheric characterization, where these dynamical constraints will be vital for a comprehensive understanding of their formation and evolution.

astro-ph.EP↗

arXiv2024

High Yield of Alpha Particles Generated in Proton-Boron Nuclear Fusion Reactions Induced in Solid Boron Hydride B${}_{18}$H${}_{22}$

The use of solid boron hydride molecules as a fuel for proton-boron fusion was proposed by M. Krůs and M. Londesborough at "Interaction of Inorganic Clusters, Cages, and Containers with Light" workshop in November 2021. Here we demonstrate experimentally, for first time, that the solid boron hydride, octadecaborane - \textit{anti}-B${}_{18}$H${}_{22}$, produces a relatively high yield of alpha particles of about $10^9$ per steradian using a sub-nanosecond, low-contrast laser pulse (PALS) with a typical intensity of $10^{16}$ Wcm${}^{-2}$. In contrast to previously published proton-boron studies, the boron hydrides, due to their composition containing only atoms of boron and hydrogen, represent a natural choice for future proton-boron nuclear fusion schemes.

physics.plasm-ph↗

arXiv2023

Photomeric analysis of eclipsing binaries: VY UMI, RU UMI AND GSC 04364-00648

We present the photometric analysis of \textit{BVR} and \textit{TESS} light curves of three eclipsing binaries (RU~UMi and purely studied VY~UMi, GSC 04364-00648), together with their period changes considering archival data and new minima times from our and \textit{TESS} observations. For the first time we detected wave-like variations with low-amplitude in $O-C$ residua of RU UMi, which can be interpreted as a consequence of the light-time effect caused by the 3rd invisible component with period 7370 days. Period increase with rate 2.56(9)$\times10^{-7}$~d/yr$^{-1}$ detected in the VY UMi system corresponds to mass transfer from the secondary to the primary component. For GSC 04364-00648 binary system we find some quadratic changes on the $O-C$ diagram, which corresponds to a period decrease with a high rate of $-2.26(5)\times10^{-5}$~d/yr$^{-1}$. We cannot assumptions about their nature, mainly due to short time of observation and uneven coverage of $O-C$ diagram. We also determined the absolute parameter of their components using the photometric solution and \textit{GAIA} distances.

astro-ph.SR↗

arXiv2022

ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations

The ExoClock project has been created with the aim of increasing the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates over an extended period, in order to produce a consistent catalogue of reliable and precise ephemerides. This work presents a homogenous catalogue of updated ephemerides for 450 planets, generated by the integration of $\sim$18000 data points from multiple sources. These sources include observations from ground-based telescopes (ExoClock network and ETD), mid-time values from the literature and light-curves from space telescopes (Kepler/K2 and TESS). With all the above, we manage to collect observations for half of the post-discovery years (median), with data that have a median uncertainty less than one minute. In comparison with literature, the ephemerides generated by the project are more precise and less biased. More than 40\% of the initial literature ephemerides had to be updated to reach the goals of the project, as they were either of low precision or drifting. Moreover, the integrated approach of the project enables both the monitoring of the majority of the Ariel candidates (95\%), and also the identification of missing data. The dedicated ExoClock network effectively supports this task by contributing additional observations when a gap in the data is identified. These results highlight the need for continuous monitoring to increase the observing coverage of the candidate planets. Finally, the extended observing coverage of planets allows us to detect trends (TTVs - Transit Timing Variations) for a sample of 19 planets. All products, data, and codes used in this work are open and accessible to the wider scientific community.

astro-ph.EP↗