arXiv subjects

Pedro J. Gutiérrez

Publications and source records attributed to Pedro J. Gutiérrez.

7 recordsLinked to original sources

arXiv2026

Dust and coma radicals in C/2024 E1 (Wierzchos): evolution of the activity

We present multi-epoch R-band imaging and long-slit spectroscopy of the dynamically new comet C/2024 E1 (Wierzchos) during its pre-perihelion phase, spanning heliocentric distances from 4.5 to 2.3 au. The most prominent fluorescence emissions in the visible wavelength range are detected. We measure production rates of CN, C$_2$, and C$_3$, while no significant NH$_2$ signal is identified. In our dataset, CN became detectable at 3.48 au, and C$_3$ and C$_2$ at 2.80 au. The mean ratios $\log\mathrm{C}_2/\mathrm{CN} = 0.00 \pm 0.07$ and $\log\mathrm{C}_3/\mathrm{CN} = -1.03 \pm 0.09$ place the comet in an intermediate taxonomic regime between typical and carbon-depleted populations. Dust production rates, ejection velocities, and particle size distributions are constrained using a Monte Carlo dust tail model that reproduces the observed coma morphology. The dust population is characterized by a power-law size distribution with an exponent of $\sim -3.5$, and particle sizes ranging from 1~$μ$m to 4~mm. The inferred initial ejection velocities span from $\sim$20$ m $s$^{-1}$ to $\sim$100$ m $s$^{-1}$. We use the empirical relation between CN and OH to estimate the water production rate and derive the dust-to-gas mass ratio for heliocentric distances $r_{\rm{h}} \lesssim 3$ au, where water sublimation is expected to dominate the activity regime. The dust-to-gas mass ratio remains consistently above unity, ranging from $\sim$1 to 3 depending on the choice of scale lengths and the CN--OH conversion factor. This result characterizes C/2024 E1 as a ``dust-rich'' comet, where the mass loss is dominated by the refractory component rather than volatiles.

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arXiv2025

Dense photometry validation of super-fast-rotating asteroid candidates

Super-fast rotators (SFRs; P < 2.2 hr) are of great importance in asteroid studies; yet, many reported detections suffer from aliasing caused by an insufficient observation cadence. We present dense CCD photometry for 15 SFRs candidates (14 after excluding 11219 Benbohn, whose published period already exceeds the spin barrier) observed from 2023 Aug 11 to 2024 Aug 11 with the 1.5 m Sierra Nevada and 1.4 m AS Vidojevica telescopes. Our dataset comprises approximately 2,400 calibrated data points, with per-measurement formal errors of 0.02-0.04 mag and total on-target coverage of 2-13 hr per object. We have reliably determined periods for 9 targets. In terms of spin rate, we have confirmed four SFRs with periods of 1.06-1.84 hr and peak-to-peak amplitudes of 0.054-0.685 mag. Three candidates remain ambiguous, while the rest are reclassified, showing the best solutions with periods greater than 2.5 hr. By extrapolating from our confirmation rate (4/14) to the 3.9 percent occurrence rate found in the Light Curve Database (LCDB) yields a central SFR fraction of 1.1 percent, with a one-sigma lower bound of 0.6 percent among kilometre-scale asteroids.

astro-ph.EP↗

arXiv2025

Activity of comet 7P/Pons-Winnecke during the 2021 apparition

Comet 7P/Pons-Winnecke was observed from the Calar Alto Observatory (Spain) for four months during the 2021 inbound apparition. Broad-band visible images were taken between 1.71 and 1.25 AU pre-perihelion, while long-slit spectrophotometric data were taken at $\sim$ 1.25 AU pre-perihelion. This dataset has been complemented with three $r$-Sloan images observed from Zwicky Transient Facility (ZTF) to model the physical properties and loss rate of the dust with a forward Monte Carlo dust tail code. The model fits the observed isophotes well for most observations. The peak dust production rate was measured at 83 kg s$^{-1}$, 15 days after perihelion. The particle terminal speed ranges from 3 m s$^{-1}$ for 0.1 m particles to 23 m s$^{-1}$ for 5 $μ$m particles. Regarding the gas production from spectra, CN and C$_2$ show asymmetric emission between the sunward and antisunward directions beyond the data uncertainties and error propagation, while a clear asymmetry for C$_3$ cannot be definitively claimed. Average production rates for CN, C$_2$, and C$_3$ near 2021 perihelion are 1.15 $\times 10^{24}$, 2.32$\times 10^{24}$, and 1.69$\times 10^{23}$ s$^{-1}$, respectively. The dust-to-gas mass ratio value is estimated to be around 2, suggesting a dust-rich composition. Based on the gas composition and the $Afρ$ value, we classify 7P/Pons-Winnecke as having a typical composition for Jupiter Family comets, with some C$_3$ depletion. Given the limited previous knowledge, our work contributes to expanding the understanding of the activity and characteristics of 7P/Pons-Winnecke.

astro-ph.EP↗

arXiv2022

CO2-driven surface changes in the Hapi region on Comet 67P/Churyumov-Gerasimenko

Between 2014 December 31 and 2015 March 17, the OSIRIS cameras on Rosetta documented the growth of a 140m wide and 0.5m deep depression in the Hapi region on Comet 67P/Churyumov-Gerasimenko. This shallow pit is one of several that later formed elsewhere on the comet, all in smooth terrain that primarily is the result of airfall of coma particles. We have compiled observations of this region in Hapi by the microwave instrument MIRO on Rosetta, acquired during October and November 2014. We use thermophysical and radiative transfer models in order to reproduce the MIRO observations. This allows us to place constraints on the thermal inertia, diffusivity, chemical composition, stratification, extinction coefficients, and scattering properties of the surface material, and how they evolved during the months prior to pit formation. The results are placed in context through long-term comet nucleus evolution modelling. We propose that: 1) MIRO observes signatures that are consistent with a solid-state greenhouse effect in airfall material; 2) CO2 ice is sufficiently close to the surface to have a measurable effect on MIRO antenna temperatures, and likely is responsible for the pit formation in Hapi observed by OSIRIS; 3) the pressure at the CO2 sublimation front is sufficiently strong to expel dust and water ice outwards, and to compress comet material inwards, thereby causing the near-surface compaction observed by CONSERT, SESAME, and groundbased radar, manifested as the "consolidated terrain" texture observed by OSIRIS.

astro-ph.EP↗

arXiv2022

Modelling the water and carbon dioxide production rates of Comet 67P/Churyumov-Gerasimenko

The European Space Agency Rosetta/Philae mission to Comet 67P/Churyumov-Gerasimenko in 2014-2016 is the most complete and diverse investigation of a comet carried out thus far. Yet, many physical and chemical properties of the comet remain uncertain or unknown, and cometary activity is still not a well-understood phenomenon. We here attempt to place constraints on the nucleus abundances and sublimation front depths of H2O and CO2 ice, and to reconstruct how the nucleus evolved throughout the perihelion passage. We employ the thermophysical modelling code 'Numerical Icy Minor Body evolUtion Simulator', or NIMBUS, to search for conditions under which the observed H2O and CO2 production rates are simultaneously reproduced before and after perihelion. We find that the refractories to water-ice mass ratio of relatively pristine nucleus material is mu~1, that airfall material has mu~2, and that the molar abundance of CO2 relative H2O near 30 per cent. The dust mantle thickness is typically < 2 cm. The average CO2 sublimation front depths near aphelion were ~3.8 m and ~1.9 m on the northern and southern hemispheres, respectively, but varied substantially with time. We propose that airfall material is subjected to substantial fragmentation and pulverisation due to thermal fatigue during the aphelion passage. Sub-surface compaction of material due to CO2 activity near perihelion seems to have reduced the diffusivity in a measurable way.

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arXiv2012

Ice structures, patterns, and processes: A view across the ice-fields

We look ahead from the frontiers of research on ice dynamics in its broadest sense; on the structures of ice, the patterns or morphologies it may assume, and the physical and chemical processes in which it is involved. We highlight open questions in the various fields of ice research in nature; ranging from terrestrial and oceanic ice on Earth, to ice in the atmosphere, to ice on other solar system bodies and in interstellar space.

nlin.PS↗

arXiv2012

Crossing barriers in planetesimal formation: The growth of mm-dust aggregates with large constituent grains

Collisions of mm-size dust aggregates play a crucial role in the early phases of planet formation. We developed a laboratory setup to observe collisions of dust aggregates levitating at mbar pressures and elevated temperatures of 800 K. We report on collisions between basalt dust aggregates of from 0.3 to 5 mm in size at velocities between 0.1 and 15 cm/s. Individual grains are smaller than 25 \mum in size. We find that for all impact energies in the studied range sticking occurs at a probability of 32.1 \pm 2.5% on average. In general, the sticking probability decreases with increasing impact parameter. The sticking probability increases with energy density (impact energy per contact area). We also observe collisions of aggregates that were formed by a previous sticking of two larger aggregates. Partners of these aggregates can be detached by a second collision with a probability of on average 19.8 \pm 4.0%. The measured accretion efficiencies are remarkably high compared to other experimental results. We attribute this to the rel. large dust grains used in our experiments, which make aggregates more susceptible to restructuring and energy dissipation. Collisional hardening by compaction might not occur as the aggregates are already very compact with only 54 \pm 1% porosity. The disassembly of previously grown aggregates in collisions might stall further aggregate growth. However, owing to the levitation technique and the limited data statistics, no conclusive statement about this aspect can yet be given. We find that the detachment efficiency decreases with increasing velocities and accretion dominates in the higher velocity range. For high accretion efficiencies, our experiments suggest that continued growth in the mm-range with larger constituent grains would be a viable way to produce larger aggregates, which might in turn form the seeds to proceed to growing planetesimals.

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