X-ray photolysis of CH${}_3$COCH${}_3$ ice: Implications for the radiation effects of compact objects towards astrophysical ices

Abstract

In this study, we employed broadband X-rays ($6-2000$ eV) to irradiate the frozen acetone CH${}_3$COCH${}_3$, at the temperature of 12 K, with different photon fluences up to $2.7\times 10^{18}$ photons cm${}^{-2}$. Here, we consider acetone as a representative complex organic molecule (COM) present on interstellar ice grains. The experiments were conduced at the Brazilian synchrotron facility (LNLS/CNPEN) employing infrared spectroscopy (FTIR) to monitor chemical changes induced by radiation in the ice sample. We determined the effective destruction cross-section of the acetone molecule and the effective formation cross-section for daughter species. Chemical equilibrium, obtained for fluence $2\times 10^{18}$ photons cm${}^{-2}$, and molecular abundances at this stage were determined, which also includes the estimates for the abundance of unknown molecules, produced but not detected, in the ice. Timescales for ices, at hypothetical snow line distances, to reach chemical equilibrium around several compact and main-sequence X-ray sources are given. We estimate timescales of 18 days, 3.6 and 1.8 months, $1.4\times 10^9-6\times 10^{11}$ years, 600 and $1.2\times 10^7$ years, and $10^7$ years, for the Sun at 5 AU, for O/B stars at 5 AU, for white dwarfs at 1 LY, for the Crab pulsar at 2.25 LY, for Vela pulsar at 2.25 LY, and for Sagittarius A* at 3 LY, respectively. This study improves our current understanding about radiation effects on the chemistry of frozen material, in particular, focusing for the first time, the effects of X-rays produced by compact objects in their eventual surrounding ices.

Accepted in MNRAS. This is a preprint. 14 pages, 7 figures

References in corpus (12)

• The frequency of planetary debris around young white dwarfs
• Complex organic molecules in protoplanetary disks
• A planetesimal orbiting within the debris disc around a white dwarf star
• A Chandra Search for Coronal X Rays from the Cool White Dwarf GD 356
• NuSTAR detection of high-energy X-ray emission and rapid variability from Sagittarius A* flares
• Oxygen atom reactions with C2H6, C2H4, and C2H2 in ices
• Radiolysis of Amino Acids by Heavy and Energetic Cosmic Ray Analogs in Simulated Space Environments: $\alpha$-Glycine Zwitterion Form
• A 3 Gyr White Dwarf with Warm Dust Discovered via the Backyard Worlds: Planet 9 Citizen Science Project
• Planet Formation around Super Massive Black Holes in the Active Galactic Nuclei
• On the frequency correlations of low-frequency QPOs with kilohertz QPOs in accreting millisecond X-ray pulsars
• Searching for Faint X-ray Emission from Galactic Stellar Wind Bow Shocks
• Variable quiescent state for the neutron-star X-ray transient SAX J1750.8-2900: not such a hot neutron star after all?

Cited by in corpus (1)

• Characterization of acetonitrile ice irradiated by X-rays employing the PROCODA code: II. Desorption processes