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(2060) Chiron is a large centaur that has been reported active on multiple occasions including during aphelion passage. Studies of Chirons coma during active periods have resulted in the detection of C(triple)N and CO outgassing. Significant work remains to be undertaken to comprehend the activation mechanisms on Chiron and the parent molecules of the gas phases detected. This work reports the study of the ices on Chirons surface and coma and seeks spectral indicators of volatiles associated with the activity. Additionally, we discuss how these detections could be related to the activation mechanism for Chiron and, potentially, other centaurs. In July 2023, the James Webb Space Telescope (JWST) observed Chiron when it was active near its aphelion. We present JWST/NIRSpec spectra from 0.97 to 5.27 microns with a resolving power of 1000, and compare them with laboratory data for identification of the spectral bands. We report the first detections on Chiron of absorption bands of several volatile ices, including CO2, CO, C2H6, C3H8, and C2H2. We also confirm the presence of water ice in its amorphous state. A key discovery arising from these data is the detection of fluorescence emissions of CH4, revealing the presence of a gas coma rich in this hyper-volatile molecule, which we also identify to be in non-local thermal equilibrium (nonLTE). CO2 gas emission is also detected in the fundamental stretching band at 4.27 microns. We argue that the presence of CH4 emission is the first proof of the desorption of CH4 due to a density phase transition of amorphous water ice at low temperature in agreement with the estimated temperature of Chiron during the JWST observations (61 K). Detection of photolytic and proton irradiation products of CH4 and CO2 on the surface, in the coma ice grains, or in the ring material is also detected via a forest of absorption features from 3.5 to 5.3 microns., Comment: 4 figures in paper plus 2 more in the appendix. Accepted as A&A Letter

We observed Sedna, Gonggong, and Quaoar with the NIRSpec instrument on the James Webb Space Telescope (JWST). All three bodies were observed in the low-resolution prism mode at wavelengths spanning 0.7 to 5.2 $\mu$m. Quaoar was also observed at 10x higher spectral resolution from 0.97 to 3.16 $\mu$m using medium-resolution gratings. Sedna's spectrum shows a large number of absorption features due to ethane (C$_2$H$_6$), as well as acetylene (C$_2$H$_2$), ethylene (C$_2$H$_4$), H$_2$O, and possibly minor CO$_2$. Gonggong's spectrum also shows several, but fewer and weaker, ethane features, along with stronger and cleaner H$_2$O features and CO$_2$ complexed with other molecules. Quaoar's prism spectrum shows even fewer and weaker ethane features, the deepest and cleanest H$_2$O features, a feature at 3.2 $\mu$m possibly due to HCN, and CO$_2$ ice. The higher-resolution medium grating spectrum of Quaoar reveals several overtone and combination bands of ethane and methane (CH$_4$). Spectra of all three objects show steep red spectral slopes and strong, broad absorptions between 2.7 and 3.6 $\mu$m indicative of complex organic molecules. The suite of light hydrocarbons and complex organic molecules are interpreted as the products of irradiation of methane. We infer that the differences in apparent abundances of irradiation products are likely due to their distinctive orbits, which lead to different timescales of methane retention and to different charged particle irradiation environments. In all cases, however, the continued presence of light hydrocarbons implies a resupply of methane to the surface. We suggest that these three bodies have undergone internal melting and geochemical evolution similar to the larger dwarf planets and distinct from all smaller KBOs., Comment: 32 pages, 9 figures, 5 tables, accepted for publication in Icarus

James Webb Space Telescope's NIRSpec infrared imaging spectrometer observed the outer solar system dwarf planets Eris and Makemake in reflected sunlight at wavelengths spanning 1 through 5 microns. Both objects have high albedo surfaces that are rich in methane ice, with a texture that permits long optical path lengths through the ice for solar photons. There is evidence for N2 ice absorption around 4.2 um on Eris, though not on Makemake. No CO ice absorption is seen at 4.67 um on either body. For the first time, absorption bands of two heavy isotopologues of methane are observed at 2.615 um (13CH4), 4.33 um (12CH3D), and 4.57 um (12CH3D). These bands enable us to measure D/H ratios of (2.5 +/- 0.5) x 10-4 and (2.9 +/- 0.6) x 10-4, along with 13C/12C ratios of 0.012 +/- 0.002 and 0.010 +/- 0.003 in the surface methane ices of Eris and Makemake, respectively. The measured D/H ratios are much lower than that of presumably primordial methane in comet 67P/Churyumov-Gerasimenko, but they are similar to D/H ratios in water in many comets and larger outer solar system objects. This similarity suggests that the hydrogen atoms in methane on Eris and Makemake originated from water, indicative of geochemical processes in past or even ongoing hot environments in their deep interiors. The 13C/12C ratios are consistent with commonly observed solar system values, suggesting no substantial enrichment in 13C as could happen if the methane currently on their surfaces was the residue of a much larger inventory that had mostly been lost to space. Possible explanations include geologically recent outgassing from the interiors as well as processes that cycle the surface methane inventory to keep the uppermost surfaces refreshed.

The NASA Lucy mission is aimed at the study of the very interesting population of Jupiter Trojans, considered as time capsules from the origin of our solar system. During its journey, the mission will pass near a main belt asteroid, Donaldjohanson. Recently, NASA has announced that a new asteroid in the belt will also be visited by Lucy: 152830 Dinkinesh (1999 VD57). The main goal of this work is to characterise this newly selected target, asteroid Dinkinesh, in order to provide critical information to the mission team. To achieve it, we have obtained visible spectra, colour photometry, and time-series photometry of Dinkinesh, using several telescopes located at different observatories. For the spectra we used the 10.4m Gran Telescopio Canarias (GTC), in the island of La Palma (Spain); for the colour photometry the 4.3m Lowell Discovery Telescope (LDT), near Happy Jack, Arizona (USA) was used; and for the time-series photometry we used the 82cm IAC80 telescope located in the island of Tenerife (Spain). Both visible spectrum and reflectance values computed from colour photometry show that Dinkinesh is an S-type asteroid, i.e., it is composed mainly of silicates and some metal. According to observations done by the NEOWISE survey, S-type asteroids have typical geometric albedo of $p_V$ = 0.223 $\pm$ 0.073. From our time-series photometry, we obtained an asteroid mean magnitude $r'$ = 19.99 $\pm$ 0.05, which provides an absolute magnitude $H_{r'}$ = 17.53 $\pm$ 0.07 assuming $G$ = 0.19 $\pm$ 0.25 for S-types. Using our colour-photometry, we transformed $H_{r'}$ to $H_V$ = 17.48 $\pm$ 0.05. This value of absolute magnitude combined with the geometric albedo provides a mean diameter for Dinkinesh of $\sim$900 m, ranging between a minimum size of 542 m and a maximum size of 1309 m., Comment: 4 pages, 3 figures, Accepted for publication in A&A

Context. Asteroid families are witnesses to the intense collisional evolution that occurred on the asteroid belt. The study of the physical properties of family members can provide important information about the state of differentiation of the parent body and provide insights into how these objects were formed. Several of these asteroid families identified across the main belt are dominated by low-albedo, primitive asteroids. These objects are important for the study of Solar System formation because they were subject to weaker thermophysical processing and provide information about the early conditions of our planetary system. Aims. We aim to study the diversity of physical properties among the Themis, Hygiea, Ursula, Veritas, and Lixiaohua families. Methods. We present new spectroscopic data, combined with a comprehensive analysis using a variety of data available in the literature, such as albedo and rotational properties. Results. Our results show that Themis and Hygiea families, the largest families in the region, present similar levels of hydration. Ursula and Lixiaohua families are redder in comparison to the others and present no sign of hydrated members based on the analysis of visible spectra. Conversely, Veritas presents the highest fraction of hydrated members. Conclusions. This work demonstrates a diverse scenario in terms of the physical properties of primitive outer-belt families, which could be associated with dynamical mixing of asteroid populations and the level of differentiation of the parental body.

Jupiter co-orbital comets have orbits that are not long-term stable. They may experience flybys with Jupiter close enough to trigger tidal disruptions like the one suffered by comet Shoemaker-Levy 9. Our aim was to study the activity and dynamical evolution of the Jupiter co-orbital comet P/2019 LD2 (ATLAS). We present results of an observational study carried out with the 10.4m Gran Telescopio Canarias (GTC) that includes image analyses using a MC dust tail fitting code to characterize its activity, and spectroscopic studies to search for gas emission. We also present N-body simulations to explore its orbital evolution. Images of LD2 obtained on 2020 May 16 show a conspicuous coma and tail. The spectrum does not exhibit any evidence of CN, C2, or C3 emission. The comet brightness in a 2.6 arcsec aperture is r'=19.34+/-0.02 mag, with colors (g'-r')=0.78+/-0.03, (r'-i')=0.31+/-0.03, and (i'-z')=0.26+/-0.03. The temporal dependence of the dust loss rate can be parameterized by a Gaussian having a FWHM of 350 days and a maximum of 60 kg/s reached on 2019 August 15. The total dust loss rate is 1.9e09 kg. LD2 is now following what looks like a short arc of a quasi-satellite cycle that started in 2017 and will end in 2028. On 2063 January 23, it will experience a very close encounter with Jupiter at 0.016 au. Its probability of escaping the solar system during the next 0.5 Myr is 0.53+/-0.03. LD2 is a kilometer-sized object, in the size range of the Jupiter-family comets, with a typical comet-like activity likely linked to sublimation of crystalline water ice and clathrates. Its origin is still an open question. We report a probability of LD2 having been captured from interstellar space during the last 0.5 Myr of 0.49+/-0.02, 0.67+/-0.06 during the last 1 Myr, 0.83+/-0.06 over 3 Myr, and 0.91+/-0.09 during the last 5 Myr., Comment: To be published in Astronomy & Astrophysics. 10 pages, 8 figures

The Arecibo Observatory (AO) is a multidisciplinary research and education facility that is recognized worldwide as a leading facility in astronomy, planetary, and atmospheric and space sciences. AO's cornerstone research instrument was the 305-m William E. Gordon telescope. On December 1, 2020, the 305-m telescope collapsed and was irreparably damaged. In the three weeks following the collapse, AO's scientific and engineering staff and the AO users community initiated extensive discussions on the future of the observatory. The community is in overwhelming agreement that there is a need to build an enhanced, next-generation radar-radio telescope at the AO site. From these discussions, we established the set of science requirements the new facility should enable. These requirements can be summarized briefly as: 5 MW of continuous wave transmitter power at 2 - 6 GHz, 10 MW of peak transmitter power at 430 MHz (also at 220MHz under consideration), zenith angle coverage 0 to 48 deg, frequency coverage 0.2 to 30 GHz and increased Field-of-View. These requirements determine the unique specifications of the proposed new instrument. The telescope design concept we suggest consists of a compact array of fixed dishes on a tiltable, plate-like structure with a collecting area equivalent to a 300m dish. This concept, referred to as the Next Generation Arecibo Telescope (NGAT), meets all of the desired specifications and provides significant new science capabilities to all three research groups at AO. This whitepaper presents a sample of the wide variety of the science that can be achieved with the NGAT, the details of the telescope design concept and the need for the new telescope to be located at the AO site. We also discuss other AO science activities that interlock with the NGAT in the white paper., Comment: 82 pages (executive summary 10 pages), 21 figures, Arecibo observatory white paper (Updated with the complete author list and minor edits)

Using data from the Infrared Array Camera on the Spitzer Space Telescope, we present photometric observations of a sample of 100 trans-Neptunian objects (TNOs) beyond 2.2 {\mu}m. These observations, collected with two broad-band filters centered at 3.6 and 4.5 {\mu}m, were done in order to study the surface composition of TNOs, which are too faint to obtain spectroscopic measurements. With this aim, we have developed a method for the identification of different materials that are found on the surfaces of TNOs. In our sample, we detected objects with colors that are consistent with the presence of small amounts of water and were able to distinguish between surfaces that are predominately composed of complex organics and amorphous silicates. We found that 86% of our sample have characteristics that are consistent with a certain amount of water ice, and the most common composition (73% of the objects) is a mixture of water ice, amorphous silicates, and complex organics. 23% of our sample may include other ices such as carbon monoxide, carbon dioxide, methane or methanol. Additionally, only small objects seem to have surfaces dominated by silicates. This method is a unique tool for the identification of complex organics and to obtain the surface composition of extremely faint objects. Also, this method will be beneficial when using the James Webb Space Telescope for differentiating groups within the trans-Neptunian population., Comment: Accepted for publication in PSJ on October 13, 2020

Makemake is one of the brightest known trans-Neptunian objects, as such, it has been widely observed. Nevertheless, its visible to near-infrared spectrum has not been completely observed in medium resolving power, aimed at studying in detail the absorption features of CH$_4$ ice. In this paper we present the spectrum of Makemake observed with X-Shooter at the Very Large Telescope (Chile). We analyse the detected features, measuring their location and depth. Furthermore, we compare Makemake's spectrum with that of Eris, obtained with the same instrument and similar setup, to conclude that the bands of the CH$_4$ ice in both objects show similar shifts., Comment: 8 pages, 10 figures, accepted in MNRAS

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., Comment: 10 pages, 5 figures

Jupiter Trojan asteroids are minor bodies that share Jupiter's orbit around the Sun. Although not yet well understood in origin and composition, they have surface properties that, besides being comparable with other populations of small bodies in the Solar System, hold information that may restrict models of planetary formation. Due their importance, there has been a significant increase in an interest in studying this population. In this context arises the NASA Lucy Mission, with a planned launch of 2021. The Lucy Mission will be the first one to address a group of 6 objects with the aim of investigating, in detail, their nature. In order to provide valuable information for mission planning and maximize the scientific return, we carried out ground based observations of four targets of the mission. Aimed at looking for variabilities on the spectra of (3548) Eurybates, (15094) Polymele and (21900) Orus, we performed rotationally resolved visible spectroscopy of them at SOAR Telescope. We also analyzed the first visible spectrum obtained for the main belt asteroid (52246) Donaldjohanson at Gran Telescopio Canarias. The spectra of Orus and Polymele present rather homogeneous characteristics along the surfaces, and their taxa correspond with those of the two dominant populations in the Trojan population, the P- and the D-type group of objects. Spectroscopy of Eurybates, on the other side, suggests that some variation on the characteristics of the reflectance of this body could be related with its collisional history. Donaldjohanson, the only main belt object in the group of targets, shows, according to our visible spectrum, hints of the presence of hydrated materials. Lucy mission will investigate the surface composition of these targets and will shed light on their connections with other minor bodies populations and in their role on the evolution of the Solar System., Comment: 10 pages, 5 figures

The white paper discusses Arecibo Observatory's plan for facility improvements and activities over the next decade. The facility improvements include: (a) improving the telescope surface, pointing and focusing to achieve superb performance up to ~12.5 GHz; (b) equip the telescope with ultrawide-band feeds; (c) upgrade the instrumentation with a 4 GHz bandwidth high dynamic range digital link and a universal backend and (d) augment the VLBI facility by integrating the 12m telescope for phase referencing. These upgrades to the Arecibo telescope are critical to keep the national facility in the forefront of research in radio astronomy while maintaining its dominance in radar studies of near-Earth asteroids, planets and satellites. In the next decade, the Arecibo telescope will play a synergistic role with the upcoming facilities such as ngVLA, SKA and the now commissioned FAST telescope. Further, the observatory will be actively engaged in mentoring and training programs for students from a diverse background., Comment: Submitted as an Activities and Projects White Paper for the Astro2020 decadal survey (13 pages, 3 figures, 1 table)

NASA's OSIRIS-REx and JAXA's Hayabusa2 sample-return missions are currently on their way to encounter primitive near-Earth asteroids (101955) Bennu and (162173) Ryugu, respectively. Spectral and dynamical evidence indicates that these near-Earth asteroids originated in the inner part of the main belt. There are several primitive collisional families in this region, and both these asteroids are most likely to have originated in the Polana-Eulalia family complex. We present the expected spectral characteristics of both targets based on our studies of our primitive collisional families in the inner belt: Polana-Eulalia, Erigone, Sulamitis, and Clarissa. Observations were obtained in the framework of our PRIMitive Asteroids Spectroscopic Survey (PRIMASS). Our results are especially relevant to the planning and interpretation of in-situ images and spectra to be obtained by the two spacecraft during the encounters with their targets., Comment: 22 pages, 11 figures. Accepted for publication in Icarus on May 11, 2018

Asteroids can be classified into several groups based on their spectral reflectance. Among these groups, the one belonging to the L-class in the taxonomic classification based on visible and near-infrared spectra exhibit several peculiar properties. First, their near-infrared spectrum is characterized by a strong absorption band interpreted as the diagnostic of a high content of the FeO bearing spinel mineral. This mineral is one of the main constituents of Calcium-Aluminum-rich Inclusions (CAI) the oldest mineral compounds found in the solar system. In polarimetry, they possess an uncommonly large value of the inversion angle incompatible with all known asteroid belonging to other taxonomical classes. Asteroids found to possess such a high inversion angle are commonly called Barbarians based on the first asteroid on which this property was first identified, (234)~Barbara. In this paper we present the results of an extensive campaign of polarimetric and spectroscopic observations of L-class objects. We have derived phase-polarization curves for a sample of 7 Barbarians, finding a variety of inversion angles ranging between 25 and 30$^{\circ}$. Spectral reflectance data exhibit variations in terms of spectral slope and absorption features in the near-infrared. We analyzed these data using a Hapke model to obtain some inferences about the relative abundance of CAI and other mineral compounds. By combining spectroscopic and polarimetric results, we find evidence that the polarimetric inversion angle is directly correlated with the presence of CAI, and the peculiar polarimetric properties of Barbarians are primarily a consequence of their anomalous composition., Comment: 31 pages, 21 figures, 5 tables

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, 2017

The Cybele and Hilda dynamical groups delimit the outer edge of the asteroid belt. Their compositional distribution is a key element to constrain evolutionary models of the Solar System. In this paper, we present a compositional analysis of these populations using spectroscopic observations, SDSS and NEOWISE data. As part of the PRIMASS (Primitive Asteroids Spectroscopic Survey), we acquired visible spectra of 18 objects in Hilda or Cybele groups with the Goodman High Throughput Spectrometer at the 4.1m SOAR telescope and 20 near-IR spectra of Hilda objects with Near Infrared Camera Spectrograph at the 3.56m TNG. The sample is enlarged with spectra taken from the literature in order to increase our statistical analysis. The spectra were inspected for aqueous alteration bands and other spectral features that can be linked to compositional constraints. The analysis shows a continuous distribution of compositions from the main-belt to the Cybele, Hilda and Trojan regions. We also identify a population in the Trojans group not present in Hilda or Cybele objects., Comment: 26 pages, 10 figures

Context: Accurate measurements of diameters of trans-Neptunian objects are extremely complicated to obtain. Thermal modeling can provide good results, but accurate absolute magnitudes are needed to constrain the thermal models and derive diameters and geometric albedos. The absolute magnitude, Hv, is defined as the magnitude of the object reduced to unit helio- and geocentric distances and a zero solar phase angle and is determined using phase curves. Phase coefficients can also be obtained from phase curves. These are related to surface properties, yet not many are known. Aims: Our objective is to measure accurate V band absolute magnitudes and phase coefficients for a sample of trans-Neptunian objects, many of which have been observed, and modeled, within the 'TNOs are cool' program, one of Herschel Space Observatory key projects. Methods: We observed 56 objects using the V and R filters. These data, along with those available in the literature, were used to obtain phase curves and measure V band absolute magnitudes and phase coefficients by assuming a linear trend of the phase curves and considering magnitude variability due to rotational light-curve. Results: We obtained 237 new magnitudes for the 56 objects, six of them with no reported previous measurements. Including the data from the literature we report a total of 110 absolute magnitudes with their respective phase coefficients. The average value of Hv is 6.39, bracketed by a minimum of 14.60 and a maximum of -1.12. In the case of the phase coefficients we report 0.10 mag per degree as the median value and a very large dispersion, ranging from -0.88 up tp 1.35 mag per degree., Comment: 35 pages, 3 long tables, 11 figures. Phase curves for 110 objects, figures available upon request. A&A accepted

In this paper we investigate the opportunities provided by the James Webb Space Telescope (JWST) for significant scientific advances in the study of solar system bodies and rings using stellar occultations. The strengths and weaknesses of the stellar occultation technique are evaluated in light of JWST's unique capabilities. We identify several possible JWST occultation events by minor bodies and rings, and evaluate their potential scientific value. These predictions depend critically on accurate a priori knowledge of the orbit of JWST near the Sun-Earth Lagrange-point 2 (L2). We also explore the possibility of serendipitous stellar occultations by very small minor bodies as a by-product of other JWST observing programs. Finally, to optimize the potential scientific return of stellar occultation observations, we identify several characteristics of JWST's orbit and instrumentation that should be taken into account during JWST's development., Comment: This paper is one of a series for a special issue on Solar System observations with JWST in PASP. Accepted 2-Oct-2015. Preprint 30 pages, 5 tables, 8 figures

Context. During the last 30 years the surface of Pluto has been characterized, and its variability has been monitored, through continuous near-infrared spectroscopic observations. But in the visible range only few data are available. Aims. The aim of this work is to define the Pluto's relative reflectance in the visible range to characterize the different components of its surface, and to provide ground based observations in support of the New Horizons mission. Methods. We observed Pluto on six nights between May and July 2014, with the imager/spectrograph ACAM at the William Herschel Telescope (La Palma, Spain). The six spectra obtained cover a whole rotation of Pluto (Prot = 6.4 days). For all the spectra we computed the spectral slope and the depth of the absorption bands of methane ice between 0.62 and 0.90 $\mu$m. To search for shifts of the center of the methane bands, associated with dilution of CH4 in N2, we compared the bands with reflectances of pure methane ice. Results. All the new spectra show the methane ice absorption bands between 0.62 and 0.90 $\mu$m. The computation of the depth of the band at 0.62 $\mu$m in the new spectra of Pluto, and in the spectra of Makemake and Eris from the literature, allowed us to estimate the Lambert coefficient at this wavelength, at a temperature of 30 K and 40 K, never measured before. All the detected bands are blue shifted, with minimum shifts in correspondence with the regions where the abundance of methane is higher. This could be indicative of a dilution of CH4:N2 more saturated in CH4. The longitudinal and secular variations of the parameters measured in the spectra are in accordance with results previously reported in the literature and with the distribution of the dark and bright material that show the Pluto's albedo maps from New Horizons., Comment: This manuscript may change and improve during the reviewing process. The data reduction and calibration is reliable and has been checked independently using different reduction approaches. The data will be made publicily available when the paper is accepted. If you need them before, please, contact the author

Context. Icy dwarf planets are key for studying the chemical and physical states of ices in the outer solar system. The study of secular and rotational variations gives us hints of the processes that contribute to the evolution of their surface. Aims. The aim of this work is to search for rotational variability on the surface composition of the dwarf planet (136472) Makemake Methods. We observed Makemake in April 2008 with the medium-resolution spectrograph ISIS, at the William Herschel Telescope (La Palma, Spain) and obtained a set of spectra in the 0.28 - 0.52 {\mu}m and 0.70 - 0.95 {\mu}m ranges, covering 82% of its rotational period. For the rotational analysis, we organized the spectra in four different sets corresponding to different rotational phases, and after discarding one with low signal to noise, we analyzed three of them that cover 71% of the surface. For these spectra we computed the spectral slope and compared the observed spectral bands of methane ice with reflectances of pure methane ice to search for shifts of the center of the bands, related to the presence of CH 4 /N 2 solid solution. Results. All the spectra have a red color with spectral slopes between 20%/1000 {\AA} and 32%/1000 {\AA} in accordance with previously reported values. Some variation in the spectral slope is detected, pointing to the possibility of a variation in the surface content or the particle size of the solid organic compound. The absorption bands of methane ice present a shift toward shorter wavelengths, indicating that methane (at least partially) is in solid solution with nitrogen. There is no variation within the errors of the shifts with the wavelength or with the depth of the bands, so there is no evidence of variation in the CH 4 /N 2 mixing ratio with rotation. By comparing with all the available data in the literature, no secular compositional variations between 2005 and 2008 is found.

We propose that several short duration events observed in past stellar occultations by Chiron were produced by rings material. From a reanalysis of the stellar occultation data in the literature we determined two possible orientations of the pole of Chiron's rings, with ecliptic coordinates l=(352+/-10) deg, b=(37+/-10) deg or l=(144+/-10) deg, b=(24+/-10) deg . The mean radius of the rings is (324 +/- 10) km. One can use the rotational lightcurve amplitude of Chiron at different epochs to distinguish between the two solutions for the pole. Both imply lower lightcurve amplitude in 2013 than in 1988, when the rotational lightcurve was first determined. We derived Chiron's rotational lightcurve in 2013 from observations at the 1.23-m CAHA telescope and indeed its amplitude is smaller than in 1988. We also present a rotational lightcurve in 2000 from images taken at CASLEO 2.15-m telescope that is consistent with our predictions. Out of the two poles the l=(144+/-10) deg, b=(24+/-10) deg solution provides a better match to a compilation of rotational lightcurve amplitudes from the literature and those presented here. We also show that using this preferred pole, Chiron's long term brightness variations are compatible with a simple model that incorporates the changing brightness of the rings as the tilt angle with respect to the Earth changes with time. Also, the variability of the water ice band in Chiron's spectra in the literature can be explained to a large degree by an icy ring system whose tilt angle changes with time and whose composition includes water ice, analogously to the case of Chariklo. We present several possible formation scenarios for the rings from qualitative points of view and speculate on the reasons why rings might be common in centaurs. We speculate on whether the known bimodal color distribution of centaurs could be due to presence of rings and lack of them.

In this work we aim to study if the variability in the absolute magnitude of Chariklo and the temporal variation of the spectral ice feature, even its disappearance in 2007, can be explained by an icy ring system whose aspect angle changes with time. We modeled the light reflected by a system as the one described above to explain the variations on the absolute magnitude of Chariklo and its rings. Using X-Shooter at VLT we obtained a new reflectance spectra, here we compared this new set of data with the ones available in the literature. We showed how the water ice feature is visible in 2013 in accordance with the ring configuration, which had an opening angle of nearly 34$^o$ in 2013. Finally we also used models of the scattering of light to fit the visible and near-infrared spectra showing different characteristic to obtain information on the composition of Chariklo and its rings. {We showed that past absolute photometry of Chariklo from the literature and new photometric data that we obtained in 2013 can be explained by a ring of particles whose opening angle changes as a function of time. We used the two possible pole solutions for the ring system and found that only one of them, $\alpha$=151.30$\pm0.5$, $\delta=41.48\pm0.2$ $^o$ ($\lambda=137.9\pm0.5$, $\beta=27.7\pm0.2$ $^o$) provides the right variation of the aspect angle with time to explain the photometry, whereas the other possible pole solution fails to explain the photometry. From spectral modeling, using the result on the pole solution, we derived the composition of Chariklo surface and of that of the rings. Chariklo surface is composed by nearly 60% of amorphous carbon, 30% of silicates and 10\% of organics, no water ice was found on the surface. Whereas the ring contains 20% of water ice, 40-70% of silicates and 10-30% of tholins and small quantities of amorphous carbon., Comment: Astronomy and Astrophysics in press

Models of the escape and retention of volatiles by minor icy objects exclude any presence of volatile ices on the surface of TNOs smaller than ~1000km in diameter at the typical temperature in this region of the solar system, whereas the same models show that water ice is stable on the surface of objects over a wide range of diameters. Collisions and cometary activity have been used to explain the process of surface refreshing of TNOs and Centaurs. These processes can produce surface heterogeneity that can be studied by collecting information at different rotational phases. The aims of this work are to study the surface composition of (20000)Varuna, a TNO with a diameter ~650km and to search for indications of rotational variability. We observed Varuna during two consecutive nights in January 2011 with NICS@TNG obtaining a set of spectra covering the whole rotation period of Varuna. After studying the spectra corresponding to different rotational phases, we did not find any indication of surface variability. In all the spectra, we detect an absorption at 2{\mu}m, suggesting the presence of water ice on the surface. We do not detect any other volatiles on the surface, although the S/N is not high enough to discard their presence. Based on scattering models, we present two possible compositions compatible with our set of data and discuss their implications in the frame of the collisional history of the Kuiper Belt. We find that the most probable composition for the surface of Varuna is a mixture of amorphous silicates, complex organics, and water ice. This composition is compatible with all the materials being primordial. However, our data can also be fitted by models containing up to a 10% of methane ice. For an object with the characteristics of Varuna, this volatile could not be primordial, so an event, such as an energetic impact, would be needed to explain its presence on the surface., Comment: 6 pages, 5 figures, to be published in A&A

Centaurs are the transitional population between trans-Neptunian objects (TNOs) and Jupiter-family comets. For this reason it is possible to access the smaller ones, which is more difficult to do with the TNO population. The goal of this work is to characterize a set of 16 Centaurs in terms of their size, albedo, and thermal properties. We study the correlations, for a more extended sample obtained from the literature, of diameter, albedo, orbital parameters, and spectral slopes. We performed three-band photometric observations using Herschel-PACS and used a consistent method for the data reduction and aperture photometry of this sample to obtain monochromatic flux densities at 70, 100, and 160 $\mu$m. Additionally, we used Spitzer-MIPS flux densities at 24 and 70 $\mu$m when available. We also included in our Centaur sample scattered disk objects (SDOs), a dynamical family of TNOS, using results previously published by our team, and some Centaurs observed only with the Spitzer/MIPS instrument. We have determined new radiometric sizes and albedos of 16 Centaurs. The first conclusion is that the albedos of Centaur objects are not correlated with their orbital parameters. Similarly, there is no correlation between diameter and orbital parameters. Most of the objects in our sample are dark (pv < 7%) and most of them are small (D < 120km). However, there is no correlation between albedo and diameter, in particular for the group of the small objects as albedo values are homogeneously distributed between 4 to 16%. The correlation with the color of the objects showed that red objects are all small (mean diameter 65 km), while the gray ones span a wide range of sizes (mean diameter 120 km). Moreover, the gray objects tend to be darker, with a mean albedo of 5.6%, compared with a mean of 8.5% (ranging from 5 to 15%) for the red objects., Comment: 16 pages, 7 figures. accepted at A&A. in press

Near-Earth binary asteroid (175706) 1996 FG3 is the current backup target of the ESA MarcoPolo-R mission, selected for the study phase of ESA M3 missions. It is a primitive (C-type) asteroid that shows significant variation in its visible and near-infrared spectra. Here we present new spectra of 1996 FG3 and we compare our new data with other published spectra, analysing the variation in the spectral slope. The asteroid will not be observable again over the next three years at least. We obtained the spectra using DOLORES and NICS instruments at the Telescopio Nazionale Galileo (TNG), a 3.6m telescope located at El Roque de los Muchachos Observatory in La Palma, Spain. To compare with other published spectra of the asteroid, we computed the spectral slope S', and studied any plausible correlation of this quantity with the phase angle (alpha). In the case of visible spectra, we find a variation in spectral slope of Delta S' = 0.15 +- 0.10 %/10^3 A/degree for 3 < alpha < 18 degrees, in good agreement with the values found in the literature for the phase reddening effect. In the case of the near-infrared, we find a variation in the slope of Delta S' = 0.04 +- 0.08 %/10^3 A/degree for 6 < alpha < 51 degrees. Our computed variation in S' agrees with the only two values found in the literature for the phase reddening in the near-infrared. The variation in the spectral slope of asteroid 1996 FG3 shows a trend with the phase angle at the time of the observations, both in the visible and the near-infrared. It is worth noting that, to fully explain this spectral variability we should take into account other factors, like the position of the secondary component of the binary asteroid 1999 FG3 with respect to the primary, or the spin axis orientation at the time of the observations. More data are necessary for an analysis of this kind., Comment: 4 pages, 3 figures, Accepted in A&A 25 June 2013

Context. Primitive asteroids contain complex organic material and ices relevant to the origin of life on Earth. These types of asteroids are the target of several-sample return missions to be launched in the next years. 1999 JU3 is the target of the Japanese Aerospace Exploration Agency's Hayabusa 2 mission. Aims. 1999 JU3 has been previously identified as a C-class asteroid. Spectroscopic observations at longer wavelengths will help to constrain its composition. Methods. We obtained spectroscopy of 1999 JU3 from 0.85 to 2.2 microns, with the 3.6 m Telescopio Nazionale Galileo using the low resolution mode of the Near Infrared Camera Spectrograph. Results. We present a near-infrared spectrum of 1999 JU3 from 0.85 to 2.2microns that is consistent with previously published spectra and with its C-type classification. Conclusions. Our spectrum confirms the primitive nature of 1999 JU3 and its interest as target of the sample-return mission Hayabusa 2., Comment: Research Note: 3 pages 1 Figure Received December 2012; accepted 4 March 2013

Near-Earth asteroid 2012 DA14 made its closest approach on February 15, 2013, when it passed at a distance of 27,700 km from the Earth's surface. It was the first time an asteroid of moderate size was predicted to approach that close to the Earth, becoming bright enough to permit a detailed study from ground-based telescopes. Asteroid 2012 DA14 was poorly characterized before its closest approach. We acquired data using several telescopes on four Spanish observatories: the 10.4m Gran Telescopio Canarias (GTC) and the 3.6m Telescopio Nazionale Galileo (TNG), both in the El Roque de los Muchachos Observatory (ORM, La Palma); the 2.2m CAHA telescope, in the Calar Alto Observatory (Almeria); the f/3 0.77m telescope in the La Hita Observatory (Toledo); and the f/8 1.5m telescope in the Sierra Nevada Observatory (OSN, Granada). We obtained visible and near-infrared color photometry, visible spectra and time-series photometry. Visible spectra together with color photometry of 2012 DA14 show that it can be classified as an L-type asteroid, a rare spectral type with a composition similar to that of carbonaceous chondrites. The time-series photometry provides a rotational period of 8.95 +- 0.08 hours after the closest approach, and there are indications that the object suffered a spin-up during this event. The large amplitude of the light curve suggests that the object is very elongated and irregular, with an equivalent diameter of around 18m. We obtain an absolute magnitude of H_R = 24.5 +- 0.2, corresponding to H_V = 25.0 +- 0.2. The GTC photometry also gives H_V = 25.29 +- 0.14. Both values agree with the value listed at the Minor Planet Center shortly after discovery. From the absolute photometry, together with some constraints on size and shape, we compute a geometric albedo of p_V = 0.44 +- 0.20, which is slightly above the range of albedos known for L-type asteroids (0.082 - 0.405)., Comment: 7 pages, 4 figures, 1 table. Accepted in A&A (June 17 2013)

Most of the objects in the trans-Neptunian belt (TNb) and related populations move in prograde orbits with low eccentricity and inclination. However, the list of icy minor bodies moving in orbits with an inclination above 40 deg. has increased in recent years. The origin of these bodies, and in particular of those objects in retrograde orbits, is not well determined, and different scenarios are considered. In this paper, we present new observational and dynamical data of two objects in retrograde orbits, 2008 YB3 and 2005 VD. We find that the surface of these extreme objects is depleted of ices and does not contain the 'ultra-red' matter typical of some Centaurs. Despite small differences, these objects share common colors and spectral characteristics with the Trojans, comet nuclei, and the group of grey Centaurs. All of these populations are supposed to be covered by a mantle of dust responsible for their reddish- to neutral-color. To investigate if the surface properties and dynamical evolution of these bodies are related, we integrate their orbits for 10^(8) years to the past. We find a remarkable difference in their dynamical evolutions: 2005 VD' s evolution is dominated by a Kozai resonance with planet Jupiter while that of 2008 YB3 is dominated by close encounters with planets Jupiter and Saturn. Our models suggest that the immediate site of provenance of 2005 VD is the in the Oort cloud, whereas for 2008 YB3 it is in the trans-Neptunian region. Additionally, the study of their residence time shows that 2005 VD has spent a larger lapse of time moving in orbits in the region of the giant planets than 2008 YB3. Together with the small differences in color between these two objects, with 2005 VD being more neutral than 2008 YB3, this fact suggests that the surface of 2005 VD has suffered a higher degree of processing, probably related to cometary activity episodes., Comment: 9 pages, 5 figures, Accepted by Astronomy and Astrophysics: 28 November 2012

X-Shooter is the first second-generation instrument for the ESO-VLT. It as a spectrograph covering the 300 - 2480 nm spectral range at once with a high resolving power. These properties enticed us to observe (136199) Eris during the science verification of the instrument. The target has numerous absorption features in the optical and near-infrared domain which has been observed by different authors, showing differences in their positions and strengths. We attempt at constraining the existence of super-volatiles, e.g., CH4, CO and N2, and in particular try to understand the physical-chemical state of the ices on Eris' surface. We observed Eris in the 300-2480 nm range and compared the newly obtained spectra with those available in the literature. We identified several absorption features, measuring their positions and depth and compare them with those of reflectance of pure methane ice obtained from the optical constants of this ice at 30 K to study shifts in their positions and find a possible explanation for their origin. We identify several absorption bands in the spectrum all consistent with the presence of CH4 ice. We do not identify bands related with N2 or CO. We measured the central wavelengths of the bands and find variable shifts, with respect to the spectrum of pure CH4 at 30 K. Conclusions. Based on these wavelength shifts we confirm the presence of a dilution of CH4 in other ice on the surface of Eris and the presence of pure CH4 spatially segregated. The comparison of the centers and shapes of these bands with previous works suggest that the surface is heterogeneous. The absence of the 2160 nm band of N2 can be explained if the surface temperature is below 35.6 K, the transition temperature between the alpha and beta phases of this ice. Our results, including the reanalysis of data published elsewhere, point to an heterogeneous surface on Eris., Comment: 15 pages, 5 figures

We present the visible spectrum of MBCs 133P/Elst-Pizarro and 176P/LINEAR, as well as three Themis family asteroids: (62) Erato, (379), Huenna and (383) Janina, obtained in 2007 using three telescopes at "El Roque de los Muchachos"' Observatory, in La Palma, Spain, and the 8m Kueyen (UT2) VLT telescope at Cerro Paranal, Chile. The spectra of 133P and 176P resemble best those of B-type asteroid and are very similar to those of Themis family members and are significantly different from the spectrum of comet 162P/Siding-Spring and most of the observed cometary nuclei. CN gas emission is not detected in the spectrum of 133P. We determine an upper limit for the CN production rate Q(CN) = $= 2.8 \times 10^{21}$ mol/s, three orders of magnitude lower than the Q(CN) of Jupiter family comets observed at similar heliocentric distances. The spectra of 133P/Elst-Pizarro and 176P/LINEAR confirm that they are likely members of the Themis family of asteroids, fragments that probably retained volatiles, and unlikely have a cometary origin in the trans-neptunian belt or the Oort cloud., Comment: Paper sumbmited to A&A. 7 pages and 6 figures

The Eurybates family is a compact core inside the Menelaus clan, located in the L4 swarm of Jupiter Trojans. Fornasier et al. (2007) found that this family exhibits a peculiar abundance of spectrally flat objects, similar to Chiron-like Centaurs and C-type main belt asteroids. On the basis of the visible spectra available in literature, Eurybates family's members seemed to be good candidates for having on their surfaces water/water ice or aqueous altered materials. To improve our knowledge of the surface composition of this peculiar family, we carried out an observational campaign at the Telescopio Nazionale Galileo (TNG), obtaining near-infrared spectra of 7 members. Our data show a surprisingly absence of any spectral feature referable to the presence of water, ices or aqueous altered materials on the surface of the observed objects. Models of the surface composition are attempted, evidencing that amorphous carbon seems to dominate the surface composition of the observed bodies and some amount of silicates (olivine) could be present., Comment: 23 pages, 2 figures, paper accepted for publication in Icarus

The atmospheric water vapor content above the Roque de los Muchachos Observatory (ORM) obtained from Global Positioning Systems (GPS) is presented. GPS measurements have been evaluated by comparison with 940nm-radiometer observations. Statistical analysis of GPS measurements points to ORM as an observing site with suitable conditions for infrared (IR) observations, with a median column of precipitable water vapor (PWV) of 3.8 mm. PWV presents a clear seasonal behavior, being Winter and Spring the best seasons for IR observations. The percentage of nighttime showing PWV values smaller than 3 mm is over 60% in February, March and April. We have also estimated the temporal variability of water vapor content at the ORM. A summary of PWV statistical results at different astronomical sites is presented, recalling that these values are not directly comparable as a result of the differences in the techniques used to recorded the data., Comment: The paper contains 10 figures and 5 tables (28 pages) Accepted by MNRAS

Context: The recent discovery of a group of trans-neptunian objects (TNOs) in a narrow region of the orbital parameter space and with surfaces composed of almost pure water ice, being 2003 EL61 its largest member, promises new and interesting results about the formation and evolution of the trans-neptunian belt (TNb) and the outer Solar System. Aims: The aim of this paper is to obtain information of the surface properties of two members of this group ((24835) 1995 SM55, (120178) 2003 OP32) and three potential members (2003 UZ117, (120347) 2004 SB60 and 2005 UQ513) and to use that in order to confirm or reject their association. Methods: We obtained visible spectra of five TNOs using the 3.58m Telescopio Nazionale Galileo at the ''Roque de los Muchachos Observatory'' (La Palma, Spain) Results: The spectra of the five TNOs are featureless within the uncertainties and with colors from slightly blue to red (-2< S'<18%/0.1microns). No signatures of any absorption are found. Conclusions: We confirm the association of 1995 SM55 and 2003 OP32 with the group of 2003 EL61 as their spectra are almost identical to that of 2003 EL61. Only one of the three candidates, 2003 UZ117, can be considered as a possible member of the EL61-group, as its visible spectrum is compatible with a spectrum of a surface composed of almost pure water ice and no complex organics. The other two, 2004 SB60 and 2005 UQ513 are red and must be considered as interlopers., Comment: 5 pages, 2 figures

2003 EL61 is the largest member of a group of TNOs with similar orbits and 'unique' spectra (neutral slope in the visible and the deepest water ice absorption bands ever observed in the TNb). Studying the composition of the surface of 2003 EL61 provides useful constrains on the origin of this particular group of TNOs and on the outer Solar system's history. We present visible and near-infrared spectra of 2003 EL61 obtained with the 4.2m WHT and the 3.6m TNG at the Roque de los Muchachos Observatory (Canary Islands, Spain). Near infrared spectra were obtained at different rotational phases covering almost one complete rotational period. Spectra are fitted using Hapke scattering models and constraints on the surface composition are derived. No significant variations in the spectral slope and in the depth of the water ice absorption bands at different rotational phases are evident, suggesting that the surface of 2003 EL61 is homogeneous. The scattering models show that a 1:1 intimate mixture of crystalline and amorphous water ice is the most probable composition for the surface of this TNO, and constrain the presence of other minor constituents to a maximum of 8% The derived composition suggests that: a) cryovolcanism is unlikely to be the main resurfacing process responsible for the high presence of water ice on the surface of these bodies; b) the surface is older than 10^8 yr. Any catastrophic event, like the collision suggested to be the origin of this population, had to happen at least 10^8 yr ago; c) the surface of 2003 EL61 is depleted of carbon chains. According to the orbital parameters of this population, this makes it a possible source of carbon-depleted Jupiter family comets., Comment: 9 pages, 7 graphs. Keywords: water ice, carbon-depleted, Kuiper Belt, astrochemistry, spectroscopy

Recent results suggest that there is a group of TNOs (2003 EL61 being the biggest member), with surfaces composed of almost pure water ice and with very similar orbital elements. We study the surface composition of another TNO that moves in a similar orbit, 2005 RR43, and compare it with the surface composition of the other members of this group. We report visible and near-infrared spectra, obtained with the 4.2m William Herschel Telescope and the 3.58m Telescopio Nazionale Galileo at the "Roque de los Muchachos" Observatory (La Palma, Spain). The spectrum of 2005 RR43 is neutral in color in the visible and dominated by very deep water ice absorption bands in the near infrared (D= 70.3 +/- 2.1 % and 82.8 +/- 4.9 % at 1.5 \mu and 2.0 \mu respectively). It is very similar to the spectrum of the group of TNOs already mentioned. All of them present much deeper water ice absorption bands (D>40 %) than any other TNO except Charon. Scattering models show that its surface is covered by water ice, a significant fraction in crytalline state with no trace (5 % upper limit) of complex organics. Possible scenarios to explain the existence of this population of TNOs are discussed: a giant collision, an originally carbon depleted composition, or a common process of continuous resurfacing. We conclude that TNO 2005 RR43 is member of a group, may be a population, of TNOs clustered in the space of orbital parameters that show abundant water ice and no signs of complex organics. The lack of complex organics in their surfaces suggests a significant smaller fraction of carbonaceous volatiles like CH4 in this population than in "normal" TNOs. A carbon depleted population of TNOs could be the origin of the population of carbon depleted Jupiter family comets already noticed by A'Hearn et al. (1995)., Comment: Final Version (Paper Accepted) 4 pages, 2 figures. Changed title, abstract, discussion

The recent discovery of two large trans-Neptunian objects (TNOs) 2003 UB313 and 2005 FY9, with surface properties similar to those of Pluto, provides an exciting new laboratory for the study of processes considered for Pluto and Triton: volatile mixing and transport; atmospheric freeze-out and escape, ice chemistry, and nitrogen phase transitions. We studied the surface composition of TNO 2003 UB313, the first known TNO larger than Pluto. We report a visible spectrum covering the 0.35-0.95 microns spectral range, obtained with the 4.2m William Herschel Telescope at "El Roque de los Muchachos" Observatory (La Palma, Spain). The visible spectrum of this TNO presents very prominent absorpt- ions bands formed in solid CH4. At wavelengths shorter than 0.6 micron the spectrum is almost featureless and slightly red (S'=4%). The icy-CH4 bands are significantly stronger than those of Pluto and slightly weaker than those observed in the spectrum of another giant TNO, 2005 FY9, implying that methane is more abundant on its surface than in Pluto's and close to that of the surface of 2005 FY9. A shift of 15 +/-3 A relative to the position of the bands of the spectrum of laboratory CH4 ice is observed in the bands at larger wavelengths (e.g. around 0.89 microns), but not at shorter wavelengths (the band around 0.73 microns is not shifted) this may be evidence for a vertical compositional gradient. Purer methane could have condensed first while 2003 UB313 moved towards aphelion during the last 200 years, and as the atmosphere gradually collapsed, the composition became more nitrogen-rich as the last, most volatile components condensed, and CH4 diluted in N2 is present in the outer surface layers., Comment: Accepted in A&A