arXiv subjects

C. de la Fuente Marcos

Publications and source records attributed to C. de la Fuente Marcos.

At least 37 records · Page 2Linked to original sources

arXiv2021

Memories of past close encounters in extreme trans-Neptunian space: Finding unseen planets using pure random searches

Context. The paths followed by the known extreme trans-Neptunian objects (ETNOs) effectively avoid direct gravitational perturbations from the four giant planets, yet their orbital eccentricities are in the range between 0.69-0.97. Solar system dynamics studies show that such high values of the eccentricity can be produced via close encounters or secular perturbations. In both cases, the presence of yet-to-be-discovered trans-Plutonian planets is required. Aims. If the high eccentricities of the known ETNOs are the result of relatively recent close encounters with putative planets, the mutual nodal distances of sizeable groups of ETNOs with their assumed perturber may still be small enough to be identifiable geometrically. In order to confirm or reject this possibility, we used Monte Carlo random search techniques. Methods. Two arbitrary orbits may lead to close encounters when their mutual nodal distance is sufficiently small. We generated billions of random planetary orbits with parameters within the relevant ranges and computed the mutual nodal distances with a set of randomly generated orbits with parameters consistent with those of the known ETNOs and their uncertainties. We monitored which planetary orbits had the maximum number of potential close encounters with synthetic ETNOs and we studied the resulting distributions. Results. We provide narrow ranges for the orbital parameters of putative planets that may have experienced orbit-changing encounters with known ETNOs. Conclusions. Our calculations suggest that more than one perturber is required if scattering is the main source of orbital modification for the known ETNOs. Perturbers might not be located farther than 600 AU and they have to follow moderately eccentric and inclined orbits to be capable of experiencing close encounters with multiple known ETNOs.

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arXiv2021

Using Mars co-orbitals to estimate the importance of rotation-induced YORP break-up events in Earth co-orbital space

Both Earth and Mars host populations of co-orbital minor bodies. A large number of present-day Mars co-orbitals is probably associated with the fission of the parent body of Mars Trojan 5261 Eureka (1990 MB) during a rotation-induced YORP break-up event. Here, we use the statistical distributions of the Tisserand parameter and the relative mean longitude of Mars co-orbitals with eccentricity below 0.2 to estimate the importance of rotation-induced Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) break-up events in Martian co-orbital space. Machine-learning techniques (k-means++ and agglomerative hierarchical clustering algorithms) are applied to assess our findings. Our statistical analysis identified three new Mars Trojans: 2009 SE, 2018 EC4 and 2018 FC4. Two of them, 2018 EC4 and 2018 FC4, are probably linked to Eureka but we argue that 2009 SE may have been captured, so it is not related to Eureka. We also suggest that 2020 VT1, a recent discovery, is a transient Martian co-orbital of the horseshoe type. When applied to Earth co-orbital candidates with eccentricity below 0.2, our approach led us to identify some clustering, perhaps linked to fission events. The cluster with most members could be associated with Earth quasi-satellite 469219 Kamo`oalewa (2016 HO3) that is a fast rotator. Our statistical analysis identified two new Earth co-orbitals: 2020 PN1, that follows a horseshoe path, and 2020 PP1, a quasi-satellite that is dynamically similar to Kamo`oalewa. For both Mars and Earth co-orbitals, we found pairs of objects whose values of the Tisserand parameter differ by very small amounts, perhaps hinting at recent disruption events. Clustering algorithms and numerical simulations both suggest that 2020 KZ2 and Kamo`oalewa could be related.

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arXiv2020

Constraining the orientation of the spin axes of extrasolar minor bodies 1I/2017 U1 (`Oumuamua) and 2I/Borisov

Context. The orientation of the spin axis of a comet is defined by the values of its equatorial obliquity and its cometocentric longitude of the Sun. These parameters can be computed from the components of the nongravitational force caused by outgassing, if the cometary activity is well characterized. The trajectories of known interstellar bodies passing through the Solar System show nongravitational accelerations. Aims. The spin-axis orientation of 1I/2017 U1 (`Oumuamua) remains to be determined; for 2I/Borisov, the already released results are mutually exclusive. Here, we investigate the orientation of the spin axes of `Oumuamua and 2I/Borisov using public orbit determinations that consider outgassing. Methods. We applied a Monte Carlo simulation using the covariance matrix method together with Monte Carlo random search techniques to compute the distributions of equatorial obliquities and cometocentric longitudes of the Sun at perihelion of `Oumuamua and 2I/Borisov from the values of the nongravitational parameters. Results. We find that the equatorial obliquity of `Oumuamua could be about 93 deg, if it has a very prolate (fusiform) shape, or close to 16 deg, if it is very oblate (disk-like). Different orbit determinations of 2I/Borisov gave obliquity values of 59 deg and 90 deg. The distributions of cometocentric longitudes were in general multimodal. Conclusions. The most probable spin-axis direction of `Oumuamua in equatorial coordinates is (280 degrees, +46 degrees) if very prolate or (312 deg, -50 deg) if very oblate. For the orbit determinations of 2I/Borisov used here, we find most probable poles pointing near (275 deg, +65 deg) and (231 deg, +30 deg), respectively. Although our analysis favors an oblate shape for 2I/Borisov, a prolate one cannot be ruled out.

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arXiv2020

Physical characterization of 2020 AV2, the first known asteroid orbiting inside Venus orbit

The first known asteroid with the orbit inside that of Venus is 2020~AV$_{2}$. This may be the largest member of a new population of small bodies with the aphelion smaller than 0.718~au, called Vatiras. The surface of 2020~AV$_{2}$ is being constantly modified by the high temperature, by the strong solar wind irradiation that characterizes the innermost region of the Solar system, and by high-energy micrometeorite impacts. The study of its physical properties represents an extreme test-case for the science of near-Earth asteroids. Here, we report spectroscopic observations of 2020~AV$_{2}$ in the 0.5-1.5~$μm$ wavelength interval. These were performed with the Nordic Optical Telescope and the William Herschel Telescope. Based on the obtained spectra, we classify 2020~AV$_{2}$ as a Sa-type asteroid. We estimate the diameter of this Vatira to be $1.50_{-0.65}^{+1.10}$ km by considering the average albedo of A-type and S-complex asteroids ($p_V=0.23_{-0.08}^{+0.11}$), and the absolute magnitude (H=$16.40\pm0.78$ mag). The wide spectral band around 1~$μm$ shows the signature of an olivine rich composition. The estimated band centre $BIC = 1.08 \pm 0.02~μm$ corresponds to a ferroan olivine mineralogy similar to that of brachinite meteorites.

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arXiv2020

Visible and near-infrared observations of interstellar comet 2I/Borisov with the 10.4-m GTC and the 3.6-m TNG telescopes

In this work, we present the results of an observational study of 2I/Borisov carried out with the 10.4-m Gran Telescopio Canarias (GTC) and the 3.6-m Telescopio Nazionale Galileo (TNG), both telescopes located at the Roque de Los Muchachos Observatory, in the island of La Palma (Spain). The study includes images in the visible and near-infrared, as well as visible spectra in the 3600 - 9200 A wavelength range. N-body simulations were also performed to explore its orbital evolution and Galactic kinematic context. The comet's dust continuum and near-infrared colours are compatible with those observed for Solar system comets. From its visible spectrum on the nights of 2019, September 24 and 26 we measured CN gas production rates Q(CN) = (2.3 +- 0.4) x 10^{24} mol/s and Q(CN) = (9.5 +- 0.2) x 10^{24} mol/s, respectively, in agreement with measurements reported by other authors on similar nights. We also obtained an upper limit for the C2 production rate of Q(C2) < (4.5 +- 0.1) x 10^{24} mol/s. Dust modelling results indicate a moderate dust production rate of about 50 kg/s at heliocentric distance r_h=2.6 au, with a differential power-law dust size distribution of index -3.4, within the range reported for many comet comae. Our simulations show that the Galactic velocity of 2I/Borisov matches well that of known stars in the solar neighbourhood and also those of more distant regions of the Galactic disc.

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arXiv2020

On the orbital evolution of meteoroid 2020 CD3, a temporarily captured orbiter of the Earth-Moon system

Any near-Earth object (NEO) following an Earth-like orbit may eventually be captured by Earth's gravity during low-velocity encounters. This theoretical possibility was first attested during the fly-by of 1991 VG in 1991-1992 with the confirmation of a brief capture episode ---for about a month in 1992 February. Further evidence was obtained when 2006 RH120 was temporarily captured into a geocentric orbit from 2006 July to 2007 July. Here, we perform a numerical assessment of the orbital evolution of 2020 CD3, a small NEO found recently that could be the third instance of a meteoroid temporarily captured by Earth's gravity. We confirm that 2020 CD3 is currently following a geocentric trajectory although it will escape into a heliocentric path by early May 2020. Our calculations indicate that it was captured by the Earth in 2016 (median). This episode is longer than that of 2006 RH120. Prior to its capture as a minimoon, 2020 CD3 was probably a NEO of the Aten type, but an Apollo type cannot be excluded; in both cases, the orbit was very Earth-like, with low eccentricity and low inclination, typical of an Arjuna-type meteoroid. A few clone orbits remained geocentric for nearly a century, opening the door to the existence of yet-to-be-detected minimoons that are relatively stable for time-scales comparable to those of unbound quasi-satellites such as (469219) Kamo`oalewa. In addition, nearly 10 per cent of the experiments led to brief moon-moon episodes in which the value of the selenocentric energy of 2020 CD3 became negative.

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arXiv2020

On the orbital evolution of 2020 AV2, the first asteroid ever observed to go around the Sun inside the orbit of Venus

The innermost section of the Solar system has not been extensively studied because minor bodies moving inside Earth's orbit tend to spend most of their sidereal orbital periods at very low solar elongation, well away from the areas more frequently observed by programs searching for near-Earth objects. The survey carried out from the Zwicky Transient Facility (ZTF) is the first one that has been able to detect multiple asteroids well detached from the direct gravitational perturbation of the Earth-Moon system. ZTF discoveries include 2019 AQ3 and 2019 LF6, two Atiras with the shortest periods among known asteroids. Here, we perform an assessment of the orbital evolution of 2020 AV2, an Atira found by ZTF with a similarly short period but following a path contained entirely within the orbit of Venus. This property makes it the first known member of the elusive Vatira population. Genuine Vatiras, those long-term dynamically stable, are thought to be subjected to the so-called von Zeipel-Lidov-Kozai oscillation that protects them against close encounters with both Mercury and Venus. However, 2020 AV2 appears to be a former Atira that entered the Vatira orbital domain relatively recently. It displays an anticoupled oscillation of the values of eccentricity and inclination, but the value of the argument of perihelion may circulate. Simulations show that 2020 AV2 might reach a 3:2 resonant orbit with Venus in the future, activating the von Zeipel-Lidov-Kozai mechanism, which in turn opens the possibility to the existence of a long-term stable population of Vatiras trapped in this configuration.

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arXiv2019

Comet C/2018 V1 (Machholz-Fujikawa-Iwamoto): dislodged from the Oort Cloud or coming from interstellar space?

The chance discovery of the first interstellar minor body, 1I/2017 U1 (`Oumuamua), indicates that we may have been visited by such objects in the past and that these events may repeat in the future. Unfortunately, minor bodies following nearly parabolic or hyperbolic paths tend to receive little attention: over 3/4 of those known have data-arcs shorter than 30 d and, consistently, rather uncertain orbit determinations. This fact suggests that we may have observed interstellar interlopers in the past, but failed to recognize them as such due to insufficient data. Early identification of promising candidates by using N-body simulations may help in improving this situation, triggering follow-up observations before they leave the Solar system. Here, we use this technique to investigate the pre- and post-perihelion dynamical evolution of the slightly hyperbolic comet C/2018 V1 (Machholz-Fujikawa-Iwamoto) to understand its origin and relevance within the context of known parabolic and hyperbolic minor bodies. Based on the available data, our calculations suggest that although C/2018 V1 may be a former member of the Oort Cloud, an origin beyond the Solar system cannot be excluded. If extrasolar, it might have entered the Solar system from interstellar space at low relative velocity with respect to the Sun. The practical feasibility of this alternative scenario has been assessed within the kinematic context of the stellar neighbourhood of the Sun, using data from Gaia second data release, and two robust solar sibling candidates have been identified. Our results suggest that comets coming from interstellar space at low heliocentric velocities may not be rare.

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arXiv2019

Flying far and fast: the distribution of distant hypervelocity star candidates from Gaia DR2 data

Context. Hypervelocity stars move fast enough to leave the gravitational field of their home galaxies and venture into intergalactic space. The most extreme examples known have estimated speeds in excess of 1000 km/s. These can be easily induced at the centres of galaxies via close encounters between binary stars and supermassive black holes; however, a number of other mechanisms operating elsewhere can produce them as well. Aims. Recent studies suggest that hypervelocity stars are ubiquitous in the local Universe. In the Milky Way, the known hypervelocity stars are anisotropically distributed, but it is unclear why. Here, we used Gaia Data Release 2 (DR2) data to perform a systematic exploration aimed at confirming or refuting these findings. Methods. We assume that the farther the candidate hypervelocity stars are, the more likely they are to be unbound from the Galaxy. We used the statistical analysis of both the spatial distribution and kinematics of these objects to achieve our goals. Results. Focussing on nominal Galactocentric distances greater than 30 kpc, which are the most distant candidates, we isolated a sample with speeds in excess of 500 km/s that exhibits a certain degree of anisotropy but remains compatible with possible systematic effects. We find that the effect of the Eddington-Trumpler-Weaver bias is important in our case: over 80% of our sources are probably located further away than implied by their parallaxes; therefore, most of our velocity estimates are lower limits. If this bias is as strong as suggested here, the contamination by disc stars may not affect our overall conclusions. Conclusions. The subsample with the lowest uncertainties shows stronger, but obviously systematic, anisotropies and includes a number of candidates of possible extragalactic origin and young age with speeds of up to 2000 km/s.

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arXiv2019

Understanding the evolution of Atira-class asteroid 2019 AQ3, a major step towards the future discovery of the Vatira population

Orbiting the Sun at an average distance of 0.59 au and with the shortest aphelion of any known minor body, at 0.77 au, the Atira-class asteroid 2019 AQ3 may be an orbital outlier or perhaps an early indication of the presence of a new population of objects: those following orbits entirely encompassed within that of Venus, the so-called Vatiras. Here, we explore the orbital evolution of 2019 AQ3 within the context of the known Atiras to show that, like many of them, it displays a present-day conspicuous coupled oscillation of the values of eccentricity and inclination, but no libration of the value of the argument of perihelion with respect to the invariable plane of the Solar system. The observed dynamics is consistent with being the result of the combined action of two dominant perturbers, the Earth-Moon system and Jupiter, and a secondary one, Venus. Such a multiperturber-induced secular dynamics translates into a chaotic evolution that can eventually lead to a resonant behaviour of the Lidov-Kozai type. Asteroid 2019 AQ3 may have experienced brief stints as a Vatira in the relatively recent past and it may become a true Vatira in the future, outlining possible dynamical pathways that may transform Atiras into Vatiras and vice versa. Our results strongly suggest that 2019 AQ3 is only the tip of the iceberg: a likely numerous population of similar bodies may remain hidden in plain sight, permanently confined inside the Sun's glare.

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arXiv2019

Waiting to make an impact: A probable excess of near-Earth asteroids in 2018 LA-like orbits

Context. The discovery and tracking of 2018 LA marks only the third instance in history that the parent body of a fireball has been identified before its eventual disintegration in our atmosphere. The subsequent recovery of meteorites from 2018 LA was only the second time materials from outer space that reached the ground could be linked with certitude to a particular minor body. However, meteoroids like 2018 LA and its forerunners, 2008 TC3 and 2014 AA, are perhaps fragments of larger members of the near-Earth object (NEO) population. As the processes leading to the production of such fragments are unlikely to spawn just one meteoroid per event, it is important to identify putative siblings and plausible candidates from which the observed meteoroids might have originated. Aims. Here, we study the pre-impact orbital evolution of 2018 LA to place this meteoroid within the dynamical context of other NEOs that follow similar trajectories. Methods. Our statistical analyses are based on the results of direct N-body calculations that use the latest orbit determinations and include perturbations by the eight major planets, the Moon, the barycentre of the Pluto-Charon system, and the three largest asteroids. A state-of-the-art NEO orbit model was used to interpret our findings and a randomization test was applied to estimate their statistical significance. Results. We find a statistically significant excess of NEOs in 2018 LA-like orbits; among these objects, we find one impactor, 2018 LA, and the fourth closest known passer-by, 2018 UA. A possible connection with the Chi-Scorpiids meteor shower is also discussed. The largest known NEO with an orbit similar to that of 2018 LA is the potentially hazardous asteroid (454100) 2013 BO73 and we speculate that they both originate from a common precursor via a collisional cascade.

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arXiv2018

Dancing with Venus in the shadow of the Earth: a pair of genetically related near-Earth asteroids trapped in a mean-motion resonance

YORP-induced fission events may form dynamically coherent pairs or even families of asteroids. The outcome of this process is well documented among members of the main asteroid belt, but not in the case of the near-Earth asteroid (NEA) population because their paths randomize very efficiently in a short time-scale. Mean-motion resonances (MMRs) may stabilize the orbits of small bodies by making them avoid close encounters with planets. In theory, YORP-induced fission of asteroids trapped in MMRs can preserve evidence of this process even in near-Earth space. Here, we show that two NEAs, 2017 SN16 and 2018 RY7, are currently following an orbital evolution in which their relative mean longitude does not exhibit any secular increase due to the stabilizing action of the 3:5 MMR with Venus. The mechanism that makes this configuration possible may be at work both in the Solar system and elsewhere. Our analysis suggests that the pair 2017 SN16-2018 RY7 may have had its origin in one out of two mechanisms: YORP-induced splitting or binary dissociation.

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arXiv2018

Searching for the lost Unicorn: a prominent feature in the radial velocity distribution of stars in Vela from Gaia DR2 data

Stellar streams are ubiquitous in the Galactic halo and they can be used to improve our understanding of the formation and evolution of the Milky Way as a whole. The so-called Monoceros Ring might have been the result of satellite accretion. Guglielmo et al. have used N-body simulations to search for the progenitor of this structure. Their analysis shows that, if the Ring has a dwarf galaxy progenitor, it might be found in the background of one out of eight specific areas in the sky. Here, we use Gaia DR2 data to perform a systematic exploration aimed at confirming or rejecting this remarkable prediction. Focusing on the values of the radial velocity to uncover possible multimodal spreads, we identify a bimodal Gaussian distribution towards Galactic coordinates (l, b) = (271, +2) degrees in Vela, which is one of the locations of the progenitor proposed by Guglielmo et al. This prominent feature with central values 60+/-7 km/s and 97+/-10 km/s, may signal the presence of the long sought progenitor of the Monoceros Ring, but the data might also be compatible with the existence of an unrelated, previously unknown, kinematically coherent structure.

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arXiv2018

A Fruit of a Different Kind: 2015 BP519 as an Outlier among the Extreme Trans-Neptunian Objects

A number of intriguing patterns have been identified in the distributions of the orbital elements of the known extreme trans-Neptunian objects or ETNOs --those with semimajor axis greater than 150 au and perihelion distance greater than 30 au. The announcement of the discovery of 2015 BP519, also known as Caju, has been hailed by some as a consistent piece of robust evidence for the existence of a yet-to-be-discovered massive planet far beyond the trans-Neptunian belt. In this Note, we use the latest data available to provide evidence against 2015 BP519 having followed the same dynamical pathway that placed other ETNOs where they are now. As an statistical outlier within the 29 known ETNOs, 2015 BP519 cannot be used as a reference to further support the trends perhaps present for other ETNOs. Asteroid 2015 BP519 represents a case of extreme dynamical anticorrelation within the ETNO orbital realm and the value of the distance to its descending node, nearly 700 au from the Sun, is the largest of any known ETNO.

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arXiv2018

Pre-airburst Orbital Evolution of Earth's Impactor 2018 LA: An Update

Apollo meteoroid 2018 LA has become only the third natural object ever to be discovered prior to causing a meteor airburst and just the second one to have its meteorites recovered (at Botswana's Central Kalahari Game Reserve). Here, we use the latest orbit determination of 2018 LA (solution date 18-July-2018) to search for minor bodies moving in paths comparable to that of 2018 LA using the D-criteria, which are metrics to study orbit similarity, and N-body simulations. Our results further confirm the existence of a dynamical grouping of asteroids that might be related to 2018 LA and show that the impactor could be a recent fragment spawned by a larger object, the 550-m wide, potentially hazardous asteroid (454100) 2013 BO73. Spectroscopic observations of 454100 during its next flyby with our planet (brightest at an apparent visual magnitude of 18.4 on 2018 mid-November) may confirm or deny a putative similar chemical composition to that of the recovered meteorites of 2018 LA.

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arXiv2018

On the Pre-impact Orbital Evolution of 2018 LA, Parent Body of the Bright Fireball Observed over Botswana on 2018 June 2

On 2018 June 2, meteoroid 2018 LA became the third natural body ever to be observed before entering our atmosphere ---small asteroids 2014 AA and 2008 TC3 had stricken the Earth on 2014 January 2 and 2008 October 7, respectively. Here, we explore the pre-impact orbital evolution of 2018 LA and investigate the possible presence of known NEOs moving in similar orbits using N-body simulations and the D-criteria. We identify several objects moving in orbits similar to that of 2018 LA and focus on three of them: (454100) 2013 BO73, which is the largest of the group and a PHA, 2016 LR, and 2018 BA5, which follows a path very close to that of 2018 LA in terms of semimajor axis, eccentricity, and inclination. All these objects could be part of a dynamical grouping and their orbital evolution is rather chaotic, experiencing close encounters with Venus, the Earth-Moon system, and Mars. NEO encounters take place at the node and, on the short-term, the relative positions of our planet in its orbit around the Sun repeat every year. Besides the bright fireball observed over Botswana on 2018 June 2, three other bolides were observed early in June in recent years: Crete on 2002 June 6, Washington State on 2004 June 3, and Reisadalen on 2007 June 7.

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arXiv2018

Kozai-Lidov Resonant Behavior among Atira-class Asteroids

Atira-class asteroids have aphelia greater than 0.718 au and smaller than 0.983 au. It has been found that the orbits of many of them remain relatively stable for at least 1 Myr, but it is unclear what can make them so stable when they cross the orbit of Venus and some may reach, in heliocentric terms, as far as Earth's perihelion and as close as inside Mercury's perihelion. The analysis of their orbits shows that many of them have values of the argument of perihelion close to 0 or 180 degrees. Such an orbital arrangement means that the nodes are located at perihelion and at aphelion, i.e. for many known Atiras, away from the path of Venus. Here, we show that the orbits of some Atiras are strongly affected by the Kozai-Lidov resonance, which translates into enhanced long-term stability.

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arXiv2018

2MASS J06562998+3002455: Not a Cool White Dwarf Candidate, but a Population II Halo Star

2MASS J06562998+3002455 or PSS 309-6 is a high proper-motion star that was discovered during a survey with the 2.1 m telescope at Kitt Peak National Observatory. Here, we reevaluate the status of this interesting star using Gaia DR2. Our results strongly suggest that PSS 309-6 could be a Population II star as the value of its V component is close to -220 km/s, which is typical for halo stars in the immediate solar neighborhood. Kapteyn's star is the nearest known halo star and PSS 309-6 exhibits similar kinematic and photometric signatures. Its properties also resemble those of 2MASS J15484023-3544254, which was once thought to be the nearest cool white dwarf but was later reclassified as K-type subdwarf. Although it is virtually certain that PSS 309-6 is not a nearby white dwarf but a more distant Population II subdwarf, further spectroscopic information, including radial velocity measurements, is necessary to fully characterize this probable member of the Galactic halo.

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