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The preparation of the long-term telescope schedule follows the submission and scientific review of new proposals. At the European Southern Observatory (ESO) this process entails scheduling the scientific proposals according to their scientific merit and available observing resources, as well as scheduling technical, maintenance, and commissioning activities for all operational telescopes of the La Silla Paranal Observatory. After the recent overhaul of the phase 1 proposal submission software, ESO started the development of a new telescopes time allocation and scheduling tool. The new tool makes the scheduling process more efficient while optimising the use of observing facilities. Besides scheduling activities and allocating time according to scientific merit, available resources, operational and programmatic needs, the tool will enable simultaneous scheduling of multiple telescopes to appropriately account for dependencies between them. The implementation of this new Time Allocation tool opens the possibility for dynamic re-scheduling of the telescopes, which is a pre-requisite to implementing a "Yearly Call for Proposals" along with the "Fast Track Channel" at ESO., Comment: Proceedings for the SPIE Astronomical Telescopes and Instrumentation 2024, Observatory Operations: Strategies, Processes and Systems X

The number of satellites in low-Earth orbit is increasing rapidly, and many tens of thousands of them are expected to be launched in the coming years. There is a strong concern among the astronomical community about the contamination of optical and near-infrared observations by satellite trails. We analyze the impact analysis of such constellations on optical and near-infrared astronomical observations in a rigorous and quantitative way, using updated constellation information, and considering imagers and spectrographs and their very different characteristics. We introduce an analytical method that allows us to rapidly and accurately evaluate the effect of a very large number of satellites, accounting for their magnitudes and the effect of trailing of the satellite image during the exposure. We use this to evaluate the impact on a series of representative instruments, including imagers (traditional narrow field instruments, wide-field survey cameras, and astro-photographic cameras) and spectrographs (long-slit and fibre-fed), taking into account their limiting magnitude. As already known (Walker et al. 2020), the effect of satellite trails is more damaging for high-altitude satellites, on wide-field instruments, or essentially during the first and last hours of the night. Thanks to their brighter limiting magnitudes, low- and mid-resolution spectrographs will be less affected, but the contamination will be at about the same level as that of the science signal, introducing additional challenges. High-resolution spectrographs will essentially be immune. We propose a series of mitigating measures, including one that uses the described simulation method to optimize the scheduling of the observations. We conclude that no single mitigation measure will solve the problem of satellite trails for all instruments and all science cases., Comment: 20 pages, 18 figures, submitted to Astronomy & Astrophysics

2I/Borisov - hereafter 2I - is the first visibly active interstellar comet observed in the solar system, allowing us for the first time to sample the composition of a building block from another system. We report on the monitoring of 2I with UVES, the high resolution optical spectrograph of the ESO Very Large Telescope at Paranal, during four months from November 15, 2019 to March 16, 2020. Our goal is to characterize the activity and composition of 2I with respect to solar system comets. We collected high resolution spectra at 12 different epochs from 2.1 au pre-perihelion to 2.6 au post perihelion. On December 24 and 26, 2019, close to perihelion, we detected several OH lines of the 309 nm (0-0) band and derived a water production rate of $2.2\pm0.2 \times 10^{26}$ molecules/s. The three [OI] forbidden oxygen lines were detected at different epochs and we derive a green-to-red doublet intensity ratio (G/R) of $0.31\pm0.05$ close to perihelion. NH$_2$ ortho and para lines from various bands were measured and allowed us to derive an ortho-to-para ratio (OPR) of $3.21\pm0.15$, corresponding to an OPR and spin temperature of ammonia of $1.11\pm0.08$ and $31^{+10}_{-5}$ K, respectively. These values are consistent with the values usually measured for solar system comets. Emission lines of the radicals NH (336 nm), CN (388 nm), CH (431 nm), and C$_2$ (517 nm) were also detected. Several FeI and NiI lines were identified and their intensities were measured to provide a ratio of log (NiI/FeI) = $0.21\pm0.18$ in agreement with the value recently found in solar system comets. Our high spectral resolution observations of 2I/Borisov and the associated measurements of the NH$_2$ OPR and the Ni/Fe abundance ratio are remarkably similar to solar system comets. Only the G/R ratio is unusually high but consistent with the high abundance ratio of CO/H$_2$O found by other investigators., Comment: Accepted for publication in A&A

At Paranal Observatory, the least predictable parameter affecting the short-term scheduling of astronomical observations is the optical turbulence, especially the seeing, coherence time and ground layer fraction. These are critical variables driving the performance of the instruments of the Very Large Telescope (VLT), especially those fed with adaptive optics systems. Currently, the night astronomer does not have a predictive tool to support him/her in decision-making at night. As most service-mode observations at the VLT last less than two hours, it is critical to be able to predict what will happen in this time frame, to avoid time losses due to sudden changes in the turbulence conditions, and also to enable more aggressive scheduling. We therefore investigate here the possibility to forecast the turbulence conditions over the next two hours. We call this "turbulence nowcasting", analogously with weather nowcasting, a term already used in meteorology coming from the contraction of "now" and "forecasting". We present here the results of a study based on historical data of the Paranal Astronomical Site Monitoring combined with ancillary data, in a machine learning framework. We show the strengths and shortcomings of such an approach, and present some perspectives in the context of the Extremely Large Telescope., Comment: 12 pages, 7 figures, proceeding of the AO4ELT6 conference

The discovery of the first active interstellar object 2I/Borisov provides an unprecedented opportunity to study planetary formation processes in another planetary system. In particular, spectroscopic observations of 2I allow us to constrain the composition of its nuclear ices. We obtained optical spectra of 2I with the 4.2 m William Herschel and 2.5 m Isaac Newton telescopes between 2019 September 30 and October 13, when the comet was between 2.5 au and 2.4 au from the Sun. We also imaged the comet with broadband filters on 15 nights from September 11 to October 17, as well as with a CN narrow-band filter on October 18 and 20, with the TRAPPIST-North telescope. Broadband imaging confirms that the dust coma colours (B-V=0.82$\pm$0.02, V-R=0.46$\pm$0.03, R-I=0.44$\pm$0.03, B-R=1.28$\pm$0.03) are the same as for Solar System comets. We detect CN emission in all spectra and in the TRAPPIST narrow-band images with production rates between 1.6$\times10^{24}$ and 2.1$\times10^{24}$ molec/s. No other species are detected. We determine three-sigma upper limits for C$_2$, C$_3$, and OH production rates of 6$\times10^{23}$ molec/s, 3$\times10^{23}$ molec/s and 2$\times10^{27}$ molec/s, respectively, on October 02. There is no significant increase of the CN production rate or A(0)f$\rho$ during our observing period. Finally, we place a three-sigma upper limit on the Q(C$_2$)/Q(CN) ratio of 0.3 (on October 13). From this, we conclude that 2I is highly depleted in C$_2$, and may have a composition similar to Solar System carbon-chain depleted comets., Comment: Revised version, Accepted for publication in A&A Letters

The first detected interstellar object 'Oumuamua that passed within 0.25au of the Sun on 2017 September 9 was presumably ejected from a stellar system. We use its newly determined non-Keplerian trajectory together with the reconstructed Galactic orbits of 7 million stars from Gaia DR2 to identify past close encounters. Such an "encounter" could reveal the home system from which 'Oumuamua was ejected. The closest encounter, at 0.60pc (0.53-0.67pc, 90% confidence interval), was with the M2.5 dwarf HIP 3757 at a relative velocity of 24.7km/s, 1Myr ago. A more distant encounter (1.6pc) but with a lower encounter (ejection) velocity of 10.7km/s was with the G5 dwarf HD 292249, 3.8Myr ago. Two more stars have encounter distances and velocities intermediate to these. The encounter parameters are similar across six different non-gravitational trajectories for 'Oumuamua. Ejection of 'Oumuamua by scattering from a giant planet in one of the systems is plausible, but requires a rather unlikely configuration to achieve the high velocities found. A binary star system is more likely to produce the observed velocities. None of the four home candidates have published exoplanets or are known to be binaries. Given that the 7 million stars in Gaia DR2 with 6D phase space information is just a small fraction of all stars for which we can eventually reconstruct orbits, it is a priori unlikely that our current search would find 'Oumuamua's home star system. As 'Oumuamua is expected to pass within 1pc of about 20 stars and brown dwarfs every Myr, the plausibility of a home system depends also on an appropriate (low) encounter velocity., Comment: Accepted to The Astronomical Journal

We describe Castalia, a proposed mission to rendezvous with a Main Belt Comet (MBC), 133P/Elst-Pizarro. MBCs are a recently discovered population of apparently icy bodies within the main asteroid belt between Mars and Jupiter, which may represent the remnants of the population which supplied the early Earth with water. Castalia will perform the first exploration of this population by characterising 133P in detail, solving the puzzle of the MBC's activity, and making the first in situ measurements of water in the asteroid belt. In many ways a successor to ESA's highly successful Rosetta mission, Castalia will allow direct comparison between very different classes of comet, including measuring critical isotope ratios, plasma and dust properties. It will also feature the first radar system to visit a minor body, mapping the ice in the interior. Castalia was proposed, in slightly different versions, to the ESA M4 and M5 calls within the Cosmic Vision programme. We describe the science motivation for the mission, the measurements required to achieve the scientific goals, and the proposed instrument payload and spacecraft to achieve these., Comment: Accepted for publication in Advances in Space Research (special issue on Small Body Exploration). 30 pages

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft, and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively `well behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit-to-orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends -- in this paper we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies., Comment: Author prepared version; final published version available at journal. 22 pages

The ESA Rosetta spacecraft, currently orbiting around comet 67P, has already provided in situ measurements of the dust grain properties from several instruments, particularly OSIRIS and GIADA. We propose adding value to those measurements by combining them with ground-based observations of the dust tail to monitor the overall, time-dependent dust-production rate and size distribution. To constrain the dust grain properties, we take Rosetta OSIRIS and GIADA results into account, and combine OSIRIS data during the approach phase (from late April to early June 2014) with a large data set of ground-based images that were acquired with the ESO Very Large Telescope (VLT) from February to November 2014. A Monte Carlo dust tail code has been applied to retrieve the dust parameters. Key properties of the grains (density, velocity, and size distribution) were obtained from Rosetta observations: these parameters were used as input of the code to considerably reduce the number of free parameters. In this way, the overall dust mass-loss rate and its dependence on the heliocentric distance could be obtained accurately. The dust parameters derived from the inner coma measurements by OSIRIS and GIADA and from distant imaging using VLT data are consistent, except for the power index of the size-distribution function, which is $\alpha$=--3, instead of $\alpha$=--2, for grains smaller than 1 mm. This is possibly linked to the presence of fluffy aggregates in the coma. The onset of cometary activity occurs at approximately 4.3 au, with a dust production rate of 0.5 kg/s, increasing up to 15 kg/s at 2.9 au. This implies a dust-to-gas mass ratio varying between 3.8 and 6.5 for the best-fit model when combined with water-production rates from the MIRO experiment., Comment: Accepted by Astronomy and Astrophysics (January 17th, 2016)

Asteroid 2009 FD could impact Earth between 2185 and 2196. The long term propagation to the possible impacts and the intervening planetary encounters make 2009 FD one of the most challenging asteroids in terms of hazard assessment. To compute accurate impact probabilities we model the Yarkovsky effect by using the available physical characterization of 2009 FD and general properties of the Near Earth Asteroid population. We perform the hazard assessment with two independent methods: the first method is a generalization of the standard impact monitoring algorithms in use by NEODyS and Sentry, while the second one is based on a Monte Carlo approach. Both methods generate orbital samples in a 7 dimensional space that includes orbital elements and the parameter characterizing the Yarkovsky effect. The highest impact probability is $2.7 \times 10^{-3}$ for an impact during the 2185 Earth encounter. Impacts after 2185 corresponding to resonant returns are possible, the most relevant being in 2190 with a probability of $3 \times 10^{-4}$. Both numerical methods can be used in the future to handle similar cases. The structure of resonant returns and the list of the possible keyholes on the Target Plane of the scattering encounter in 2185 can be predicted by an analytic theory.

P/2013 P5 PANSTARRS was discovered in Aug. 2013, displaying a cometary tail, but with orbital elements typical for a member of the inner asteroid Main Belt. We monitored the object from 2013 Aug. 30 until Oct. 05 using the CFHT, NTT, CA 1.23m, Perkins 1.8m (Lowell), and the 0.6m TRAPPIST telescopes. We measured its nuclear radius to be r < 0.25-0.29km, and its colours g-r = 0.58+/-0.05 and r-i = 0.23+/-0.06, typical for an S-class asteroid. We failed to detect any rotational light curve, with an amplitude < 0.05mag and a double-peaked rotation period < 20h. A detailed Finson-Probstein analysis of deep NTT and CFHT images indicated that the object was active since at least late January 2013 until the time of the latest observations in 2013 September, with at least two peaks of activity around 2013 June 14+/-10d and 2013 July 22+/-3d. The changes of activity level and the activity peaks were extremely sharp and short, shorter than the temporal resolution of our observations (about 1d). The dust distribution was similar during these two events, with dust grains covering at least the 1-1000{\mu}m range. The total mass ejected in grains <1mm was estimated to be 3.0 10$^6$kg and 2.6 10$^7$kg around the two activity peaks. Rotational disruption cannot be ruled out as the cause of the dust ejection. We also propose that the components of a contact binary might gently rub and produce the observed emission. Volatile sublimation might also explain what appears as cometary activity over a period of 8 months. However, while Main Belt comets best explained by ice sublimation are found in the outskirts of the Main Belt, where water ice is believed to be able to survive buried in moderately large objects for the age of the solar system deeply, the presence of volatiles in an object smaller than 300m in radius would be very surprising in the inner asteroid belt., Comment: A&A, accepted

We present an update of the visible and near-infrared colour database of Minor Bodies in the Outer Solar System (MBOSSes), which now includes over 2000 measurement epochs of 555 objects, extracted from over 100 articles. The list is fairly complete as of December 2011. The database is now large enough to enable any dataset with a large dispersion to be safely identified and rejected from the analysis. The selection method used is quite insensitive to individual outliers. Most of the rejected datasets were observed during the early days of MBOSS photometry. The spectral gradient over the visible range is derived from the colours, as well as the R absolute magnitude M(1, 1). The average colours, absolute magnitude, and spectral gradient are listed for each object, as well as the physico-dynamical classes using a classification adapted from Gladman and collaborators. Colour-colour diagrams, histograms, and various other plots are presented to illustrate and investigate class characteristics and trends with other parameters, whose significances are evaluated using standard statistical tests. The colour tables and all plots are also available on the MBOSS colour web page http://www.eso.org/~ohainaut/MBOSS which will be updated when new measurements are published., Comment: 26 pages + 29 pages supplement. A&A in press

We present our latest results about the short-term variability of trans-Neptunian objects (TNOs). We performed broad-band CCD photometric observations using several telescopes in Spain and Chile. We present results based on three years of observations and report the short-term variability of 10 TNOs. Our sample of studied targets contains classical objects: (275809) 2001 QY297, (307251) 2002 KW14, (55636) 2002 TX300, 2004 NT33, (230965) 2004 XA192, and (202421) 2005 UQ513, a resonant body: (84522) 2002 TC302, a scattered target: (44594) 1999 OX3, and two detached objects: (145480) 2005 TB190, and (40314) 1999 KR16. For each target, light curves as well as possible rotation periods and photometric amplitudes are reported. The majority of the observed objects present a low peak-to-peak amplitude, <0.15mag. Only two objects exhibit light curve amplitudes higher than 0.15mag: (275809) 2001 QY297, and (307251) 2002 KW14. We remark two biases in the literature, previously studied in Thirouin et al. (2010) and confirmed by this new study: a bias towards objects with a small amplitude light curve and a second one against objects with a long rotational period in the data base of published rotational periods. We derived constraints on physical properties of some targets. We also report the solar phase curves of (40314) 1999 KR16, and (44594) 1999 OX3 for solar phase angles from 0 degree to around 2 degrees. Part of our discussion is focused on the study of (275809) 2001 QY297 which turned out to be an asynchronous binary system., Comment: 30 pages, 25 figures, Accepted for publication in MNRAS

Comet P/2010A2 LINEAR is a good candidate for membership with the Main Belt Comet family. It was observed with several telescopes (ESO NTT, La Silla; Gemini North, Mauna Kea; UH 2.2m, Mauna Kea) from 14 Jan. until 19 Feb. 2010 in order to characterize and monitor it and its very unusual dust tail, which appears almost fully detached from the nucleus; the head of the tail includes two narrow arcs forming a cross. The immediate surroundings of the nucleus were found dust-free, which allowed an estimate of the nucleus radius of 80-90m. A model of the thermal evolution indicates that such a small nucleus could not maintain any ice content for more than a few million years on its current orbit, ruling out ice sublimation dust ejection mechanism. Rotational spin-up and electrostatic dust levitations were also rejected, leaving an impact with a smaller body as the favoured hypothesis, and ruling out the cometary nature of the object. The impact is further supported by the analysis of the tail structure. Finston-Probstein dynamical dust modelling indicates the tail was produced by a single burst of dust emission. More advanced models, independently indicate that this burst populated a hollow cone with a half-opening angle alpha~40degr and with an ejection velocity v_max ~ 0.2m/s, where the small dust grains fill the observed tail, while the arcs are foreshortened sections of the burst cone. The dust grains in the tail are measured to have radii between a=1-20mm, with a differential size distribution proportional to a^(-3.44 +/- 0.08). The dust contained in the tail is estimated to at least 8x10^8kg, which would form a sphere of 40m radius. Analysing these results in the framework of crater physics, we conclude that a gravity-controlled crater would have grown up to ~100m radius, i.e. comparable to the size of the body. The non-disruption of the body suggest this was an oblique impact., Comment: 15 pages, 11 figures, in press

A dedicated mission to investigate exoplanetary atmospheres represents a major milestone in our quest to understand our place in the universe by placing our Solar System in context and by addressing the suitability of planets for the presence of life. EChO -the Exoplanet Characterisation Observatory- is a mission concept specifically geared for this purpose. EChO will provide simultaneous, multi-wavelength spectroscopic observations on a stable platform that will allow very long exposures. EChO will build on observations by Hubble, Spitzer and groundbased telescopes, which discovered the first molecules and atoms in exoplanetary atmospheres. EChO will simultaneously observe a broad enough spectral region -from the visible to the mid-IR- to constrain from one single spectrum the temperature structure of the atmosphere and the abundances of the major molecular species. The spectral range and resolution are tailored to separate bands belonging to up to 30 molecules to retrieve the composition and temperature structure of planetary atmospheres. The target list for EChO includes planets ranging from Jupiter-sized with equilibrium temperatures Teq up to 2000 K, to those of a few Earth masses, with Teq ~300 K. We have baselined a dispersive spectrograph design covering continuously the 0.4-16 micron spectral range in 6 channels (1 in the VIS, 5 in the IR), which allows the spectral resolution to be adapted from several tens to several hundreds, depending on the target brightness. The instrument will be mounted behind a 1.5 m class telescope, passively cooled to 50 K, with the instrument structure and optics passively cooled to ~45 K. EChO will be placed in a grand halo orbit around L2. We have also undertaken a first-order cost and development plan analysis and find that EChO is easily compatible with the ESA M-class mission framework., Comment: Accepted for publication in Experimental Astronomy, 23 pages, 15 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

Thermal emission from Kuiper Belt object (136108) Haumea was measured with Herschel-PACS at 100 and 160 micrometers for almost a full rotation period. Observations clearly indicate a 100-micrometer thermal lightcurve with an amplitude of a factor of ~ 2, which is positively correlated with the optical lightcurve. This confirms that both are primarily due to shape effects. A 160-micrometer lightcurve is marginally detected. Radiometric fits of the mean Herschel- and Spitzer- fluxes indicate an equivalent diameter D ~ 1300 km and a geometric albedo p_v ~ 0.70-0.75. These values agree with inferences from the optical lightcurve, supporting the hydrostatic equilibrium hypothesis. The large amplitude of the 100-micrometer lightcurve suggests that the object has a high projected a/b axis ratio (~ 1.3) and a low thermal inertia as well as possible variable infrared beaming. This may point to fine regolith on the surface, with a lunar-type photometric behavior. The quality of the thermal data is not sufficient to clearly detect the effects of a surface dark spot., Comment: Accepted for publication in Astronomy & Astrophysics (special issue on Herschel first results)

The goal of the Herschel Open Time Key programme "TNOs are Cool!" is to derive the physical and thermal properties for a large sample of Centaurs and trans-Neptunian objects (TNOs), including resonant, classical, detached and scattered disk objects. We present results for seven targets either observed in PACS point-source, or in mini scan-map mode. Spitzer-MIPS observations were included for three objects. The sizes of these targets range from 100 km to almost 1000 km, five have low geometric albedos below 10%, (145480) 2005 TB190 has a higher albedo above 15%. Classical thermal models driven by an intermediate beaming factor of $\eta$=1.2 or $\eta$-values adjusted to the observed colour temperature fit the multi-band observations well in most cases. More sophisticated thermophysical models give very similar diameter and albedo values for thermal inertias in the range 0-25 Jm-2s-0.5K-1, consistent with very low heat conductivities at temperatures far away from the Sun. The early experience with observing and model strategies will allow us to derive physical and thermal properties for our complete Herschel TNO sample of 140 targets as a benchmark for understanding the solar system debris disk, and extra-solar ones as well., Comment: 5 pages, 2 figures, accepted for publication in the A&A Herschel Special Issue

On 4 July 2005 at 05:52 UT, the impactor of NASA's Deep Impact (DI) mission crashed into comet 9P/Tempel 1 with a velocity of about 10 km/s. The material ejected by the impact expanded into the normal coma, produced by ordinary cometary activity. The characteristics of the non-impact coma and cloud produced by the impact were studied by observations in the visible wavelengths and in the near-IR. The scattering characteristics of the "normal" coma of solid particles were studied by comparing images in various spectral regions, from the UV to the near-IR. For the non-impact coma, a proxy of the dust production has been measured in various spectral regions. The presence of sublimating grains has been detected. Their lifetime was found to be about 11 hours. Regarding the cloud produced by the impact, the total geometric cross section multiplied by the albedo was measured as a function of the color and time. The projected velocity appeared to obey a Gaussian distribution with the average velocity of the order of 115 m/s. By comparing the observations taken about 3 hours after the impact, we have found a strong decrease in the cross section in J filter, while that in Ks remained almost constant. This is interpreted as the result of sublimation of grains dominated by particles of sizes of the order of some microns., Comment: Accepted by A&A

We present the results of a visible spectroscopic and photometric survey of Jupiter Trojans belonging to different dynamical families carried out at the ESO-NTT telescope. We obtained data on 47 objects, 23 belonging to the L5 swarm and 24 to the L4 one. These data together with those already published by Fornasier et al. (2004a) and Dotto et al. (2006), constitute a total sample of visible spectra for 80 objects. The survey allows us to investigate six families (Aneas, Anchises, Misenus, Phereclos, Sarpedon, Panthoos) in the L5 cloud and four L4 families (Eurybates, Menelaus, 1986 WD and 1986 TS6). The sample that we measured is dominated by D--type asteroids, with the exception of the Eurybates family in the L4 swarm, where there is a dominance of C- and P-type asteroids. All the spectra that we obtained are featureless with the exception of some Eurybates members, where a drop--off of the reflectance is detected shortward of 5200 A. Similar features are seen in main belt C-type asteroids and commonly attributed to the intervalence charge transfer transition in oxidized iron. Our sample comprises fainter and smaller Trojans as compared to the literature's data and allows us to investigate the properties of objects with estimated diameter smaller than 40--50 km. The analysis of the spectral slopes and colors versus the estimated diameters shows that the blue and red objects have indistinguishable size distribution. We perform a statistical investigation of the Trojans's spectra property distributions as a function of their orbital and physical parameters, and in comparison with other classes of minor bodies in the outer Solar System. Trojans at lower inclination appear significantly bluer than those at higher inclination, but this effect is strongly driven by the Eurybates family., Comment: 52 pages, 14 figure, paper accepted for publication in Icarus

Long-duration gamma-ray bursts (GRBs) are associated with type Ic supernovae that are more luminous than average and that eject material at very high velocities. Less-luminous supernovae were not hitherto known to be associated with GRBs, and therefore GRB-supernovae were thought to be rare events. Whether X-ray flashes - analogues of GRBs, but with lower luminosities and fewer gamma-rays - can also be associated with supernovae, and whether they are intrinsically 'weak' events or typical GRBs viewed off the axis of the burst, is unclear. Here we report the optical discovery and follow-up observations of the type Ic supernova SN 2006aj associated with X-ray flash XRF 060218. Supernova 2006aj is intrinsically less luminous than the GRB-supernovae, but more luminous than many supernovae not accompanied by a GRB. The ejecta velocities derived from our spectra are intermediate between these two groups, which is consistent with the weakness of both the GRB output and the supernova radio flux. Our data, combined with radio and X-ray observations, suggest that XRF 060218 is an intrinsically weak and soft event, rather than a classical GRB observed off-axis. This extends the GRB-supernova connection to X-ray flashes and fainter supernovae, implying a common origin. Events such as XRF 060218 are probably more numerous than GRB-supernovae., Comment: Final published version

Various techniques are being used to search for extra-solar planetary signatures, including accurate measurement of radial velocity and positional (astrometric) displacements, gravitational microlensing, and photometric transits. Planned space experiments promise a considerable increase in the detections and statistical knowledge arising especially from transit and astrometric measurements over the years 2005-15, with some hundreds of terrestrial-type planets expected from transit measurements, and many thousands of Jupiter-mass planets expected from astrometric measurements. Beyond 2015, very ambitious space (Darwin/TPF) and ground (OWL) experiments are targeting direct detection of nearby Earth-mass planets in the habitable zone and the measurement of their spectral characteristics. Beyond these, `Life Finder' (aiming to produce confirmatory evidence of the presence of life) and `Earth Imager' (some massive interferometric array providing resolved images of a distant Earth) appear as distant visions. This report, to ESA and ESO, summarises the direction of exo-planet research that can be expected over the next 10 years or so, identifies the roles of the major facilities of the two organisations in the field, and concludes with some recommendations which may assist development of the field. The report has been compiled by the Working Group members and experts over the period June-December 2004., Comment: ESA-ESO Working Groups Report No. 1, 92 pages, 7 figures, a pdf version including the cover pages is available from ESO and ESA websites: http://www.eso.org/gen-fac/pubs/esaesowg/ http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=36935 A printed version (A5 booklet) is available in limited numbers from Space Telescope-European Coordinating Facility (ST-ECF) on request: stdesk@eso.org

We report optical and infrared spectroscopic observations of the Type Ia SN 1999ee and the Type Ib/c SN 1999ex, both of which were hosted by the galaxy IC 5179. For SN 1999ee we obtained a continuous sequence with an unprecedented wavelength and temporal coverage beginning 9 days before maximum light and extending through day 42. Before maximum light SN 1999ee displayed a normal spectrum with a strong Si II 6355 absorption, thus showing that not all slow-declining SNe are spectroscopically peculiar at these evolutionary phases. A comparative study of the infrared spectra of SN 1999ee and other Type Ia supernovae shows that there is a remarkable homogeneity among the Branch-normal SNe Ia during their first 60 days of evolution. SN 1991bg-like objects, on the other hand, display spectroscopic peculiarities at infrared wavelengths. SN 1999ex was characterized by the lack of hydrogen lines, weak optical He I lines, and strong He I 10830,20581, thus providing an example of an intermediate case between pure Ib and Ic supernovae. We conclude therefore that SN 1999ex provides first clear evidence for a link between the Ib and Ic classes and that there is a continuous spectroscopic sequence ranging from the He deficient SNe Ic to the SNe Ib which are characterized by strong optical He I lines., Comment: 35 pages, 13 figures, accepted by The Astronomical Journal

The discovery of the peculiar supernova (SN) 1998bw and its possible association with the gamma-ray burst (GRB) 980425$^{1,2,3}$ provide new clues to the understanding of the explosion mechanism of very massive stars and to the origin of some classes of gamma-ray bursts. Its spectra indicate that SN~1998bw is a type Ic supernova$^{3,4}$, but its peak luminosity is unusually high compared with typical type Ic supernovae$^3$. Here we report our findings that the optical spectra and the light curve of SN 1998bw can be well reproduced by an extremely energetic explosion of a massive carbon+oxygen (C+O) star. The kinetic energy is as large as $\sim 2-5 \times 10^{52}$ ergs, more than ten times the previously known energy of supernovae. For this reason, the explosion may be called a `hypernova'. Such a C+O star is the stripped core of a very massive star that has lost its H and He envelopes. The extremely large energy, suggesting the existence of a new mechanism of massive star explosion, can cause a relativistic shock that may be linked to the gamma-ray burst., Comment: to appear in Nature(accepted July 27; submitted June 11, 1998)

The discovery of X-ray, optical and radio afterglows of gamma-ray bursts (GRBs) and the measurements of the distances to some of them have established that these events come from Gpc distances and are the most powerful photon emitters known in the Universe, with peak luminosities up to 10^52 erg/s. We here report the discovery of an optical transient, in the BeppoSAX Wide Field Camera error box of GRB980425, which occurred within about a day of the gamma-ray burst. Its optical light curve, spectrum and location in a spiral arm of the galaxy ESO 184-G82, at a redshift z = 0.0085, show that the transient is a very luminous type Ic supernova, SN1998bw. The peculiar nature of SN1998bw is emphasized by its extraordinary radio properties which require that the radio emitter expand at relativistical speed. Since SN1998bw is very different from all previously observed afterglows of GRBs, our discovery raises the possibility that very different mechanisms may give rise to GRBs, which differ little in their gamma-ray properties., Comment: Under press embargo at Nature (submitted June 10, 1998)

We present the results of a 7 year long photometric monitoring of two components (A and B) of UM 425, thought to be images, separated by 6.5", of the same z = 1.47 quasar. These components have been imaged through an R filter in order to obtain their light curves. The photometry was obtained by simultaneously fitting a stellar two-dimensional profile on each component. The brightest image (component A, m(R) = 15.7) shows a slow and smooth increase in brightness of 0.2 magnitude in seven years, while the faintest one (component B, m(R) = 20.1) displays an outburst of 0.4 magnitude which lasts approximately two years. The variation of component B may be interpreted in two ways, assuming UM 425 is gravitationally lensed. If it is due to an intrinsic variation of the quasar, we derive a lower limit of 3 years on the time delay from the fact that it is not observed in component A. On the other hand, if it is a microlensing ``High Amplification Event'', we estimate the size of the source to be ~ 10^{-3} pc, in agreement with standard models of AGNs. These observations are consistent with the gravitational lens interpretation of the object. Furthermore, all the CCD frames obtained under the best seeing conditions have been co-added, in an attempt to detect the deflector. The final R image reveals a rich field of faint galaxies in the magnitude range m(R) 22-24. No obvious deflector, nor any system of arcs or arclets is detected, down to a limiting magnitude of m(R) 24., Comment: Astronomy and Astrophysics, in press (accepted March 22, 1995). Postscript file of 8 pages, figures included