The complex binary system
β
Lyr A has an extensive observational dataset: light curves (from far UV to far IR), interferometric squared visibility, closure phase, triple product measurements, ...spectral-energy distribution, high-resolution spectroscopy, differential visibility amplitude, and also a differential phase. In particular, we used spectra from the Ondřejov 2m telescope from 2013 to 2015 to measure the emission in H
α
, He
I
, Si
II
, Ne
I
, or C
II
lines, and differential interferometry by CHARA/VEGA from the 2013 campaign to measure wavelength-dependent sizes across H
α
and He
I
6678. This allowed us to constrain not only optically thick objects (primary, secondary, accretion disc), but also optically thin objects (disc atmosphere, jets, shell). We extended our modelling tool, Pyshellspec (based on Shellspec; a 1D local thermodynamical equilibrium radiative transfer code), to include all new observables, to compute differential visibilities/phases, to perform a Doppler tomography, and to determine a joint
χ
2
metric. After an optimisation of 38 free parameters, we derived a robust model of the
β
Lyr A system. According to the model, the emission is formed in an extended atmosphere of the disc, two perpendicular jets expanding at ∼700 km s
−1
, and a symmetric shell with the radius ∼70
R
⊙
. The spectroscopy indicates a low abundance of carbon, 10
−2
of the solar value. We also quantified systematic differences between datasets, and we discuss here alternative models with higher resolutions, additional asymmetries, or He-rich abundances.
We model the long-term evolution of the Hilda collisional family located in the 3/2 mean-motion resonance with Jupiter. Its eccentricity distribution evolves mostly due to the Yarkovsky/YORP effect ...and assuming that (i) impact disruption was isotropic and (ii) albedo distribution of small asteroids is the same as for large ones, we can estimate the age of the Hilda family to be 4+0
−1 Gyr. We also calculate collisional activity in the J3/2 region. Our results indicate that current collisional rates are very low for a 200-km parent body such that the number of expected events over gigayears is much smaller than 1.
The large age and the low probability of the collisional disruption lead us to the conclusion that the Hilda family might have been created during the late heavy bombardment (LHB) when the collisions were much more frequent. The Hilda family may thus serve as a test of orbital behaviour of planets during the LHB. We have tested the influence of the giant-planet migration on the distribution of the family members. The scenarios that are consistent with the observed Hilda family are those with fast migration time-scales ≃0.3-3 Myr, because longer time-scales produce a family that is depleted and too much spread in eccentricity. Moreover, there is an indication that Jupiter and Saturn were no longer in a compact configuration (with period ratio P
S/P
J > 2.09) at the time when the Hilda family was created.
The study of photon-induced reactions in collisions of heavy nuclei at RHIC and the LHC has become an important direction of the research program of these facilities in recent years. In particular, ...the production of vector mesons in ultra-peripheral collisions (UPC) has been intensively studied. Owing to the intense photon fluxes, the two nuclei participating in such processes undergo electromagnetic dissociation producing neutrons at beam rapidities. Here, we introduce the nOOn (pronounced noon) Monte Carlo program, which generates events containing such neutrons. nOOn is a ROOT based program that can be interfaced with existing generators of vector meson production in UPC or with theoretical calculations of such photonuclear processes. nOOn can also be easily integrated with the simulation programs of the experiments at RHIC and the LHC.
Program Title:nOOn
Program Files doi:http://dx.doi.org/10.17632/jynt6cvhjk.1
Licencing provisions: GNU GPLv3
Programming language: C++
External routines: The generator is based on ROOT.
Nature of problem: The electromagnetic fields of nuclei at RHIC and the LHC can be described as a flux of quasi-real photons. These photons may interact with one of the nucleus in the opposite beam. There are events of interest where two independent interactions occur, one involving a hard scattering and one from the exchange of soft photons. As a result of the latter, the nucleus get excited and upon de-excitation it may emit neutrons, which are boosted to beam rapidities. The program computes the probability of neutron emission based on existing measurements and some mild modelling; it then generates neutrons in a per-event basis.
Solution method: The break-up probabilities are computed using existing data and stored in ROOT objects (graphs and histograms). Photon energies from the accompanying hard process, e.g. vector meson production, are loaded into the program and a catalogue of specific break-up probabilities is constructed. The number of neutrons emitted in the event is generated and the neutrons are produced and boosted into the laboratory frame. The output is a TTree with a TClonesArray of TParticles per event, which can be easily interfaced to the simulation programs of the RHIC and LHC collaborations.
Restrictions: At the moment only emission from Pb is available.
References:https://github.com/mbroz84/noon
Asteroid families are believed to originate by catastrophic disruptions of large asteroids. They are nowadays identified as clusters in the proper orbital elements space. The proper elements are ...analytically defined as constants of motion of a suitably simplified dynamical system. Indeed, they are generally nearly constant on a 10
7–10
8-year time scale. Over longer time intervals, however, they may significantly change, reflecting the accumulation of the tiny nonperiodic evolutions provided by chaos and nonconservative forces. The most important effects leading to a change of the proper orbital elements are (i) the chaotic diffusion in narrow mean motion resonances, (ii) the Yarkovsky nongravitational force, and (iii) the gravitational impulses received at close approaches with large asteroids. A natural question then arises: How are the size and shape of an asteroid family modified due to evolution of the proper orbital elements of its members over the family age? In this paper, we concentrate on the dynamical dispersion of the proper eccentricity and inclination, which occurs due to (i), but with the help of (ii) and (iii). We choose the Flora family as a model case because it is unusually dispersed in eccentricity and inclination and, being located in the inner main belt, is intersected by a large number of effective mean motion resonances with Mars and Jupiter. Our results suggest that the Flora family dynamically disperses on a few 10
8-year time scale and that its age may be significantly less than 10
9 years. We discuss the possibility that the parent bodies of the Flora family and of the ordinary L chondrite meteorites are the same object. In a broader sense, this work suggests that the common belief that the present asteroid families are simple images of their primordial dynamical structure should be revised.
Context. In the past decade, more than one hundred asteroid models were derived using the lightcurve inversion method. Measured by the number of derived models, lightcurve inversion has become the ...leading method for asteroid shape determination. Aims. Tens of thousands of sparse-in-time lightcurves from astrometric projects are publicly available. We investigate these data and use them in the lightcurve inversion method to derive new asteroid models. By having a greater number of models with known physical properties, we can gain a better insight into the nature of individual objects and into the whole asteroid population. Methods. We use sparse photometry from selected observatories from the AstDyS database (Asteroids – Dynamic Site), either alone or in combination with dense lightcurves, to determine new asteroid models by the lightcurve inversion method. We investigate various correlations between several asteroid parameters and characteristics such as the rotational state and diameter or family membership. We focus on the distribution of ecliptic latitudes of pole directions. We create a synthetic uniform distribution of latitudes, compute the method bias, and compare the results with the distribution of known models. We also construct a model for the long-term evolution of spins. Results. We present 80 new asteroid models derived from combined data sets where sparse photometry is taken from the AstDyS database and dense lightcurves are from the Uppsala Asteroid Photometric Catalogue (UAPC) and from several individual observers. For 18 asteroids, we present updated shape solutions based on new photometric data. For another 30 asteroids we present their partial models, i.e., an accurate period value and an estimate of the ecliptic latitude of the pole. The addition of new models increases the total number of models derived by the lightcurve inversion method to ~200. We also present a simple statistical analysis of physical properties of asteroids where we look for possible correlations between various physical parameters with an emphasis on the spin vector. We present the observed and de-biased distributions of ecliptic latitudes with respect to different size ranges of asteroids as well as a simple theoretical model of the latitude distribution and then compare its predictions with the observed distributions. From this analysis we find that the latitude distribution of small asteroids (D < 30 km) is clustered towards ecliptic poles and can be explained by the YORP thermal effect while the latitude distribution of larger asteroids (D > 60 km) exhibits an evident excess of prograde rotators, probably of primordial origin.
δ
Orionis is the closest massive multiple stellar system and one of the brightest members of the Orion OB association. The primary (Aa1) is a unique evolved O star. In this work, we applied a ...two-step disentangling method to a series of spectra in the blue region (430–450 nm), and we detected spectral lines of the secondary (Aa2). For the first time, we were able to constrain the orbit of the tertiary (Ab) – to 55 450 d or 152 yr – using variable
γ
velocities and new speckle interferometric measurements, which have been published in the Washington Double Star Catalogue. In addition, the
Gaia
DR3 parallax of the faint component (Ca+Cb) constrains the distance of the system to (381 ± 8) pc, which is just in the centre of the Orion OB1b association, at (382 ± 1) pc. Consequently, we found that the component masses according to the three-body model are 17.8, 8.5, and 8.7
M
⊙
, for Aa1, Aa2, and Ab, respectively, with the uncertainties of the order of 1
M
⊙
. We used new photometry from the BRITE satellites together with astrometry, radial velocities, eclipse timings, eclipse duration, spectral line profiles, and spectral energy distribution to refine radiative properties. The components, classified as O9.5 II + B2 V + B0 IV, have radii of 13.1, 4.1, and 12.0
R
⊙
, which means that
δ
Ori A is a pre-mass-transfer object. The frequency of 0.478 cycles per day, known from the Fourier analysis of the residual light curve and X-ray observations, was identified as the rotation frequency of the tertiary.
δ
Ori could be related to other bright stars in Orion, in particular,
ζ
Ori, which has a similar architecture, or
ε
Ori, which is a single supergiant, and possibly a post-mass-transfer object.
•125 SPH/N-body simulations of impacts into 10 km bodies have been carried out•Resulting distributions of fragments differ from simulations of 100 km bodies•New parametric relations for largest ...remnants and fragments were derived
We report on our study of asteroidal breakups, i.e. fragmentations of targets, subsequent gravitational reaccumulation and formation of small asteroid families. We focused on parent bodies with diameters Dpb=10km. Simulations were performed with a smoothed-particle hydrodynamics (SPH) code combined with an efficient N-body integrator. We assumed various projectile sizes, impact velocities and impact angles (125 runs in total). Resulting size-frequency distributions are significantly different from scaled-down simulations with Dpb=100km targets (Durda et al., 2007). We derive new parametric relations describing fragment distributions, suitable for Monte-Carlo collisional models. We also characterize velocity fields and angular distributions of fragments, which can be used as initial conditions for N-body simulations of small asteroid families. Finally, we discuss a number of uncertainties related to SPH simulations.
Aims.
The satellite Linus orbiting the main-belt asteroid (22) Kalliope exhibited mutual occultation and transit events in late 2021. A photometric campaign was organised and observations were ...undertaken by the TRAPPIST-South, SPECULOOS-Artemis, OWL-Net, and BOAO telescopes, with the goal to further constrain dynamical and photometric models of this sizeable asteroid-satellite system.
Methods.
Our dynamical model is sufficiently complex, featuring multipoles (up to the order of
ℓ
= 2), internal tides, and external tides. The model was constrained by astrometry (spanning 2001–2021), occultations, adaptive-optics imaging, and calibrated photometry, as well as relative photometry. Our photometric model was substantially improved. A new precise (<0.1 mmag) light curve algorithm was implemented, based on polygon intersections, which are computed exactly by including partial eclipses and partial visibility of polygons. Moreover, we implemented a ‘cliptracing’ algorithm, again based on polygon intersections, in which partial contributions to individual pixels are computed exactly. Both synthetic light curves and synthetic images then become very smooth.
Results.
Based on our combined solution, we confirmed the size of Linus, namely, (28 ± 1)km. However, this solution exhibits some tension among the light curves and the PISCO speckle-interferometry dataset, acquired simultaneously with the 2021 events. This indicates that improvements of the shape are still possible. In most solutions, Linus is darker than Kalliope, with the single-scattering albedos
A
w
= 0.40 vs. 0.44. This is confirmed on deconvolved images. A detailed revision of astrometric data has allowed us to revise also the
J
2
≡ −
C
20
value of Kalliope. Most importantly, a homogeneous body is excluded. For a differentiated body, two solutions exist: low-oblateness (
C
20
≃ −0.12), with a spherical iron core, and, alternatively, high-oblateness (
C
20
≃ −0.22) with an elongated iron core. These values correspond, respectively, to the low- and high-energy collisions we studied via SPH simulations in our previous work.
Context. The current number of ~500 asteroid models derived from the disk-integrated photometry by the lightcurve inversion method allows us to study the spin-vector properties of not only the whole ...population of main-belt asteroids, but also of several individual collisional families. Aims. We create a data set of 152 asteroids that were identified by the hierarchical clustering method (HCM) as members of ten collisional families, among which are 31 newly derived unique models and 24 new models with well-constrained pole-ecliptic latitudes of the spin axes. The remaining models are adopted from the DAMIT database or a few individual publications. Methods. We revised the preliminary family membership identification by the HCM according to several additional criteria: taxonomic type, color, albedo, maximum Yarkovsky semi-major axis drift, and the consistency with the size-frequency distribution of each family, and consequently we remove interlopers. We then present the spin-vector distributions for asteroidal families Flora, Koronis, Eos, Eunomia, Phocaea, Themis, Maria, and Alauda. We use a combined orbital- and spin-evolution model to explain the observed spin-vector properties of objects among collisional families. Results. In general, for studied families we observe similar trends in (ap, β) space (proper semi-major axis vs. ecliptic latitude of the spin axis): (i) larger asteroids are situated in the proximity of the center of the family; (ii) asteroids with β > 0° are usually found to the right of the family center; (iii) on the other hand, asteroids with β < 0° to the left of the center; (iv) the majority of asteroids have large pole-ecliptic latitudes (|β| ≳ 30°); and finally (v) some families have a statistically significant excess of asteroids with β > 0° or β < 0°. Our numerical simulation of the long-term evolution of a collisional family is capable of reproducing the observed spin-vector properties well. Using this simulation, we also independently constrain the age of families Flora (1.0 ± 0.5 Gyr) and Koronis (2.5–4 Gyr).
Context.
Cybele asteroids constitute an appealing reservoir of primitive material genetically linked to the outer Solar System, and the physical properties (size and shape) of the largest members can ...be readily accessed by large (8m class) telescopes.
Aims.
We took advantage of the bright apparition of the most iconic member of the Cybele population, (65) Cybele, in July and August 2021 to acquire high-angular-resolution images and optical light curves of the asteroid with which we aim to analyse its shape and bulk properties.
Methods.
Eight series of images were acquired with VLT/SPHERE+ZIMPOL, seven of which were combined with optical light curves to reconstruct the shape of the asteroid using the
ADAM
,
MPCD
, and
SAGE
algorithms. The origin of the shape was investigated by means of N-body simulations.
Results.
Cybele has a volume-equivalent diameter of 263±3 km and a bulk density of 1.55 ± 0.19 g cm
−3
. Notably, its shape and rotation state are closely compatible with those of a Maclaurin equilibrium figure. The lack of a collisional family associated with Cybele and the higher bulk density of that body with respect to other large P-type asteroids suggest that it never experienced any large disruptive impact followed by rapid re-accumulation. This would imply that its present-day shape represents the original one. However, numerical integration of the long-term dynamical evolution of a hypothetical family of Cybele shows that it is dispersed by gravitational perturbations and chaotic diffusion over gigayears of evolution.
Conclusions.
The very close match between Cybele and an equilibrium figure opens up the possibility that
D
≥ 260 km (
M
≥ 1.5 × 10
19
kg) small bodies from the outer Solar System all formed at equilibrium. However, we cannot currently rule out an old impact as the origin of the equilibrium shape of Cybele. Cybele itself is found to be dynamically unstable, implying that it was ‘recently’ (<1 Gyr ago) placed on its current orbit either through slow diffusion from a relatively stable orbit in the Cybele region or, less likely, from an unstable, Jupiter-family-comet orbit in the planet-crossing region.
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