On the dust environment of Main-Belt Comet 313P/Gibbs

We present observations carried out using the 10.4 m Gran Telescopio Canarias and an interpretative model of the dust environment of activated asteroid 313P/Gibbs. We discuss three different models relating to different values of the dust parameters, i.e, dust loss rate, maximum and minimum sizes of particles, power index of the size distribution, and emission pattern. The best model corresponds with an isotropic emission of particles which started on August 1st. The size of grains were in the range of $0.1-2000$ $\mu$m, with velocities for 100 $\mu$m particles between $0.4-1.9$ m$~$s$^{-1}$, with a dust production rate in the range of $0.2-0.8$ kg$~$s$^{-1}$. The dust tails' brightness and morphology are best interpreted in terms of a model of sustained and low dust emission driven by water-ice sublimation, spanning since 2014 August 1st, and triggered by a short impulsive event. This event produced an emission of small particles of about 0.1 $\mu$m with velocities of $\sim$4 m$~$s$^{-1}$. From our model we deduce that the activity of this Main-Belt Comet continued for, at least, four months, since activation.Comment: 14 pages, 4 figures, 2 tables. Accepted for publication in The Astrophysical Journa

Dust loss from activated asteroid P/2015 X6

We present observations and dust tail models of activated asteroid P/2015 X6 from deep imaging data acquired at the 10.4m Gran Telescopio Canarias (GTC) from mid-December 2015 to late January 2016. The results of the modeling indicate that the asteroid has undergone a sustained dust loss over a two-month or longer period. The dust parameters, derived from multidimensional fits of the available images, are compatible with either ice sublimation or rotational instability processes. An impulsive event, as it could be associated to an impact with another body, is less likely. A power-law distribution of particles, with minimum and maximum radius of 1 $\mu$m and 1 cm, and power index of --3.3 is found to be consistent with the observations. Depending on the ejection velocity model adopted, the particle velocities are found in the 0.3 to 10 m s$^{-1}$ range. The activation time was between 18-26 days before discovery. The total ejected mass from that time to the most recent observation is in the range 5-9$\times$10$^6$ kg. No dust features giving indication of past activity earlier than the activation time have been observed.Comment: Accepted by ApJ, May 15th 201

Disrupted asteroid P/2016 G1. II. Follow-up observations from the Hubble Space Telescope

After the early observations of the disrupted asteroid P/2016 G1 with the 10.4m Gran Telescopio Canarias (GTC), and the modeling of the dust ejecta, we have performed a follow-up observational campaign of this object using the Hubble Space Telescope (HST) during two epochs (June 28 and July 11, 2016). The analysis of these HST images with the same model inputs obtained from the GTC images revealed a good consistency with the predicted evolution from the GTC images, so that the model is applicable to the whole observational period from late April to early July 2016. This result confirms that the resulting dust ejecta was caused by a relatively short-duration event with onset about 350 days before perihelion, and spanning about 30 days (HWHM). For a size distribution of particles with a geometric albedo of 0.15, having radii limits of 1 $\mu$m and 1 cm, and following a power-law with index --3.0, the total dust mass ejected is $\sim$2$\times$10$^7$ kg. As was the case with the GTC observations, no condensations in the images that could be attributed to a nucleus or fragments released after the disruption event were found. However, the higher limiting magnitude reachable with the HST images in comparison with those from GTC allowed us to impose a more stringent upper limit to the observed fragments of $\sim$30 m.Comment: 10 pages, 2 figures Accepted by Astronomical Journal, Nov. 2, 201

The dust environment of comet C/2012 S1 (ISON)

editorial reviewedA Monte Carlo comet dust tail model has been applied to extract the dust environment parameters of comet C/2012 S1 (ISON) from both Earth-based and Solar and Heliospheric Observatory (SOHO) calibrated observations, performed from about 6 Astronomical Units (au) inbound, to right after perihelion passage, when just a small portion of the original comet nucleus survived in the form of a cloud of tiny particles. The early Afρ and image data are consistent with particle ejection from an extended active area occupying a large region between latitudes 35°N to 90°N (for a prograde rotating nucleus), with the spin axis having a large obliquity (I ≈ 70°). This configuration fits nicely the early images and Afρ data until approximately 3.9 au inbound, where the emission should become isotropic in order to fit the data. This isotropic ejection model perfectly mimics the minimum in the Afρ data found observationally 60 days before perihelion and the steep rise afterwards owing to the strong outburst of activity detected by many observers during the first hours of November 14, 2013. The comparison of the derived dust loss rates with water production rates implies a dust-to-gas ratio which generally decreases with increasing heliocentric distance, and a particle ejection velocity law that is close to a r_h^{-2} dependence. The analysis of SOHO LASCO C3 images around comet's perihelion reveals that, assuming an original nucleus of R_N = 500 m with ρ = 1000 kg m^{-3}, at least half of the mass of the nucleus was vaporized when the comet was at about 17 solar radii inbound. We conclude that at that time the nucleus suffered a cataclysmic fragmentation releasing a huge amount of material of 2.3×10^{11} kg, for a particle density of 1000 kg m^{-3}, equivalent to a sphere of 380 m in radius. The model results on a later pre-perihelion image at about 5.5 solar radii implies a further reduction in mass of about 300 to that at 17 solar radii, a consequence of vaporization of comet material. However, the total mass contained in the post-perihelion tails analyzed are about the same of that at 5.5 solar radii pre-perihelion, but with much smaller particles in the distribution, implying that the dominating process at perihelion was particle fragmentation. The total mass contained in the last SOHO LASCO C3 post-perihelion image analyzed, at 27.5 solar radii post-perihelion, the surviving ISON material is just 6.7×10^8 kg or a sphere of 54 m in radius with the density of 1000 kg m^{-3}. The dust contained in the post-perihelion tails is very small in size, with particles having 0.1-50 μ m in radius, distributed following a power law of index -3.5

Dust modelling and a dynamical study of comet 41P/Tuttle-Giacobini-Kresak during its 2017 perihelion passage

Thanks to the Rosetta mission, our understanding of comets has greatly improved. A very good opportunity to apply this knowledge appeared in early 2017 with the appearance of the Jupiter family comet 41P/TGK. We performed an observational campaign with the TRAPPIST telescopes that covered almost the entire period of time when the comet was active. In this work we present a comprehensive study of the evolution of the dust environment of 41P based on observational data from January to July, 2017. Also, we performed numerical simulations to constrain its origin and dynamical nature. To model the observational data set we used a Monte Carlo dust tail model, which allowed us to derive the dust parameters that best describe its dust environment as a function of heliocentric distance. In order to study its dynamical evolution, we completed several experiments to evaluate the degree of stability of its orbit, its life time in its current region close to Earth, and its future behaviour. From the dust analysis, we found that comet 41P has a complex emission pattern that shifted from full isotropic to anisotropic ejection sometime during February 24-March 14 in 2017, and then from anisotropic to full isotropic again between June 7-28. During the anisotropic period, the emission was controlled by two strongly active areas, where one was located in the southern and one in the northern hemisphere of the nucleus. The total dust mass loss is estimated to be $\sim7.5\times10^{8}$ kg. From the dynamical simulations we estimate that $\sim$3600 yr is the period of time during which 41P will remain in a similar orbit. Taking into account the estimated mass loss per orbit, after 3600 yr, the nucleus may lose about 30$\%$ of its mass. However, based on its observed dust-to-water mass ratio and its propensity to outbursts, the lifetime of this comet could be much shorter.Comment: 14 pages, 13 figures. Accepted for its publication in Astronomy & Astrophysic

WASP-189b: an ultra-hot Jupiter transiting the bright A star HR 5599 in a polar orbit

We report the discovery of WASP-189b: an ultra-hot Jupiter in a 2.72-d transiting orbit around the $V = 6.6$ A star WASP-189 (HR 5599). We detected periodic dimmings in the star's lightcurve, first with the WASP-South survey facility then with the TRAPPIST-South telescope. We confirmed that a planet is the cause of those dimmings via line-profile tomography and radial-velocity measurements using the HARPS and CORALIE spectrographs. Those reveal WASP-189b to be an ultra-hot Jupiter ($M_{\rm P}$ = 2.13 $\pm$ 0.28 $M_{\rm Jup}$; $R_{\rm P}$ = 1.374 $\pm$ 0.082 $R_{\rm Jup}$) in a polar orbit ($\lambda = 89.3 \pm 1.4^\circ$; $\Psi = 90.0 \pm 5.8^\circ$) around a rapidly rotating A6IV-V star ($T_{\rm eff}$ = 8000 $\pm$ 100 K; $v_* \sin i_*$ $\approx$ 100 km\, s$^{-1}$). We calculate a predicted equilibrium temperature of $T_{\rm eql}$ = 2641 $\pm$ 34 K, assuming zero albedo and efficient redistribution, which is the third hottest for the known exoplanets. WASP-189 is the brightest known host of a transiting hot Jupiter and the third-brightest known host of any transiting exoplanet. We note that of the eight hot-Jupiter systems with $T_{\rm eff}$ $>$ 7000 K, seven have strongly misaligned orbits, and two of the three systems with $T_{\rm eff}$ $\geq$ 8000 K have polar orbits (the third is aligned).Comment: Submitted to MNRAS. 10 pages, 9 figures, 3 table

Profesorado de enseñanza básica: características socioprofesionales, formación TIC y efectos en su práctica (Algarbe-Portugal)

En las últimas décadas países como Portugal han realizado un esfuerzo económico importante para poder introducir las TIC en sus escuelas. El objetivo que nos proponemos con este trabajo es identificar las características socio-profesionales del profesorado del primer ciclo de enseñanza básica de la región del Algarbe (Portugal) y su relación con el tiempo de uso de las TIC en sus aulas, entre otros factores. La metodología utilizada es cuantitativa siendo el instrumento principal el cuestionario. La muestra quedó constituida por 156 docentes de la región. Entre los resultados encontramos que las docentes tienen una mayor frecuencia semanal de uso de las TIC que sus compañeros varones y que cuanta más formación se cursa más horas de implementación de las TIC en el aula se produce. finalmente, concluimos con una serie de reflexiones sobre la formación y la integración de las TIC que pueden servir a prácticos, teóricos e instituciones.info:eu-repo/semantics/publishedVersio

TRAPPIST comet production rates: 19P/Borrelly, 67P/C-G, 104P/Kowal 2, C/2019 L3 (ATLAS), and C/2021 A1 (Leonard)

E. Jehin, Y. Moulane, J. Manfroid, M. Vander Donckt, F. Pozuelos, M. Ferrais, and D. Hutsemekers (STAR Institute, University of Liege) report that they obtained from TRAPPIST-North (code=Z53, Morocco) and TRAPPIST-South (code=I40, Chile) robotic telescopes (Jehin el al. 2011) recent observations using cometary HB narrowband filters (Farnham et al. 2000) for the following comets and computed preliminary production rates at 10.000 km using a Haser Model (Vp=Vd=1km/s) (Haser 1957)

Outburst of comet C/2021 A1 (Leonard) on January 7, 2021

We report about an outburst of comet C/2021 A1 (Leonard) that happened between January 6 and 8, 00:00 UT 2021. Observations were carried on with TRAPPIST-South (code=I40, Chile) robotic telescopes about every night since Dec 20 until Jan 25, using broad band and cometary HB narrowband filters (Jehin el al. 2011)