arXiv subjects

Gergely Friss

Publications and source records attributed to Gergely Friss.

4 recordsLinked to original sources

arXiv2026

Atmospheric Supply of Hydrogen Cyanide Is Not the Rate-limiting Step for Prebiotic Chemistry across Rocky Exoplanets

Hydrogen cyanide (HCN) is crucial for the RNA World hypothesis, forming biomolecules essential for early life. Life likely emerged around 4 billion years ago during the early Archean Eon, a period on Earth with a fainter sun, frequent impacts, and a weakly reducing atmosphere. Warm little ponds (WLPs) are hypothetical protective aqueous environments that help explain the emergence and evolution of fragile prebiotic chemistry in such a hostile environment. WLPs need to undergo cycles of evaporation and rehydration, concentrating prebiotic molecules that increase the likelihood of (de-)polymerisation and forming early RNA molecules. We use a 1-D model of atmospheric chemistry to compare atmospheric HCN delivery to WLPs with exogenous sources. Using early Archean Earth as our baseline, we examine the sensitivity of atmospheric HCN delivery to the atmospheric C/O ratio, semi-major axis, assumed stellar host type, and methane budget, exploring conditions across rocky exoplanets. We find that atmospheric HCN delivery is sensitive to these parameters but its values generally exceed that of meteoritic delivery and our baseline Archean Earth. Planetary atmospheres with higher C/O ratios within the habitable zones of G stars and those closely orbiting M-dwarfs deliver the most atmospheric HCN. We find that atmospheric HCN delivery is remarkably robust, so this molecule is likely not the rate limiting step for the emergence of prebiotic chemistry on rocky exoplanets. This finding, with important caveats, potentially increases the probability of life emerging on other worlds.

astro-ph.EP↗

arXiv2026

Hydrocarbon complexity and photochemical shielding of prebiotic feedstock molecules in exoplanet atmospheres

The potential of prebiotic chemistry to propagate on an exoplanet fundamentally depends on whether the atmospheric conditions can facilitate the production of prebiotic feedstock molecules. Photochemical simulations of exoplanet atmospheres can be used to explore this potential atmospheric synthesis, but require a comprehensive chemical network. We present the implementation of the CRAHCN-O network, constructed to simulate the formation of feedstock molecules such as HCN, H$_2$CO, and simple hydrocarbons, into the VULCAN photochemical kinetics code. We investigate the production of feedstock molecules driven by M-star radiation and compare these to predictions by the N-C-H-O network in VULCAN, for N$_2$-dominated atmospheres with C/O ratios between 0.5-1.5. Predicted abundances are similar for C/O${=}$0.5. Once CH$_4$ is included (i.e., for C/O${>}$0.5), the abundance profiles diverge in the photochemical regions. By analysing the attenuation of UV radiation, we find that hydrocarbon photochemical shielding causes the diverging profiles. CRAHCN-O accumulates C$_2$H$_6$, while N-C-H-O accumulates C$_4$H$_3$ and C$_3$H$_4$. Importantly, C$_2$H$_6$ is photochemically active whereas C$_4$H$_3$ and C$_3$H$_4$ are assumed inactive. With mixing ratios up to a few percent in CRAHCN-O, C$_2$H$_6$ shields CH$_4$ and CO$_2$ from photodissociation and weakens the destruction of HCN and H$_2$CO. Maximum HCN mixing ratios reach 1000 ppm with CRAHCN-O compared to only 3 ppm with N-C-H-O. Other feedstock molecules like HC$_3$N and C$_2$H$_2$ form more efficiently in N-C-H-O. The shielding mechanism and its impact on feedstock molecules persist for radiation from distinct M-star types. These results demonstrate the crucial role of chemical kinetics in understanding prebiotic processes in exoplanet atmospheres, including important considerations for the construction and applicability of chemical networks.

astro-ph.EP↗

arXiv2023

GRBAlpha: the smallest astrophysical space observatory -- Part 1: Detector design, system description and satellite operations

Aims. Since launched on 2021 March 22, the 1U-sized CubeSat GRBAlpha operates and collects scientific data on high-energy transients, making it the smallest astrophysical space observatory to date. GRBAlpha is an in-obit demonstration of a gamma-ray burst (GRB) detector concept suitably small to fit into a standard 1U volume. As it was demonstrated in a companion paper, GRBAlpha adds significant value to the scientific community with accurate characterization of bright GRBs, including the recent outstanding event of GRB 221009A. Methods. The GRB detector is a 75x75x5 mm CsI(Tl) scintillator wrapped in a reflective foil (ESR) read out by an array of SiPM detectors, multi-pixel photon counters by Hamamatsu, driven by two separate, redundant units. To further protect the scintillator block from sunlight and protect the SiPM detectors from particle radiation, we apply a multi-layer structure of Tedlar wrapping, anodized aluminium casing and a lead-alloy shielding on one edge of the assembly. The setup allows observations of gamma radiation within the energy range of 70-890 keV with an energy resolution of ~30%. Results. Here, we summarize the system design of the GRBAlpha mission, including the electronics and software components of the detector, some aspects of the platform as well as the current way of semi-autonomous operations. In addition, details are given about the raw data products and telemetry in order to encourage the community for expansion of the receiver network for our initiatives with GRBAlpha and related experiments.

astro-ph.IM↗

arXiv2023

The peak-flux of GRB 221009A measured with GRBAlpha

The brightest gamma-ray burst ever observed, long-duration GRB 221009A, was detected by GRBAlpha nano-satellite without saturation. We present light curves of the prompt emission in 13 energy bands, from 80 keV to 950 keV, and perform a spectral analysis to calculate the peak flux and peak isotropic-equivalent luminosity. Since the satellite's attitude information is not available for the time of this GRB, more than 200 incident directions were probed in order to find the median luminosity and its systematic uncertainty. We found that the peak flux in the $80-800$ keV range (observer frame) was $F_{\rm{ph}}^{\rm{p}}=1300_{-200}^{+1200}$ ph cm$^{-2}$s$^{-1}$ or $F_{\rm{erg}}^{\rm{p}}=5.7_{-0.7}^{+3.7}\times10^{-4}$ erg cm$^{-2}$s$^{-1}$ and the fluence in the same energy range of the first GRB episode lasting 300 s, which was observable by GRBAlpha, was $S=2.2_{-0.3}^{+1.4}\times10^{-2}$ erg cm$^{-2}$ or $S^{\rm{bol}}=4.9_{-0.5}^{+0.8}\times10^{-2}$ erg cm$^{-2}$ for the extrapolated range of $0.9-8,690$ keV. We infer the isotropic-equivalent released energy of the first GRB episode to be $E_{\rm{iso}}^{\rm{bol}}=2.8_{-0.5}^{+0.8}\times10^{54}$ erg in the $1-10,000$ keV band (rest frame at $z=0.15$). The peak isotropic-equivalent luminosity in the $92-920$ keV range (rest frame) was $L_{\rm{iso}}^{\rm{p}}=3.7_{-0.5}^{+2.5}\times10^{52}$ erg s$^{-1}$ and the bolometric peak isotropic-equivalent luminosity was $L_{\rm{iso}}^{\rm{p,bol}}=8.4_{-1.5}^{+2.5}\times10^{52}$ erg s$^{-1}$ (4 s scale) in the $1-10,000$ keV range (rest frame). The peak emitted energy is $E_p^\ast=E_p(1+z)=1120\pm470$ keV. Our measurement of $L_{\rm{iso}}^{\rm{p,bol}}$ is consistent with the Yonetoku relation. It is possible that, due to the spectral evolution of this GRB and orientation of GRBAlpha at the peak time, the true values of peak flux, fluence, $L_{\rm{iso}}$, and $E_{\rm{iso}}$ are even higher. [abridged]

astro-ph.HE↗