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See detailThe remarkable surface homogeneity of the Dawn mission target (1) Ceres
Carry, Benoît; Vernazza, Pierre; Dumas, Christophe et al

in Icarus (2012), 217

Dwarf-planet (1) Ceres is one of the two targets, along with (4) Vesta, that will be studied by the NASA Dawn spacecraft via imaging, visible and near-infrared spectroscopy, and gamma-ray and neutron ... [more ▼]

Dwarf-planet (1) Ceres is one of the two targets, along with (4) Vesta, that will be studied by the NASA Dawn spacecraft via imaging, visible and near-infrared spectroscopy, and gamma-ray and neutron spectroscopy. While Ceres' visible and near-infrared disk-integrated spectra have been well characterized, little has been done about quantifying spectral variations over the surface. Any spectral variation would give us insights on the geographical variation of the composition and/or the surface age. The only work so far was that of Rivkin and Volquardsen ([2010], Icarus 206, 327) who reported rotationally-resolved spectroscopic (disk-integrated) observations in the 2.2-4.0 μm range; their observations showed evidence for a relatively uniform surface.Here, we report disk-resolved observations of Ceres with SINFONI (ESO VLT) in the 1.17-1.32 μm and 1.45-2.35 μm wavelength ranges. The observations were made under excellent seeing conditions (0.6″), allowing us to reach a spatial resolution of ˜75 km on Ceres' surface. We do not find any spectral variation above a 3% level, suggesting a homogeneous surface at our spatial resolution. Slight variations (about 2%) of the spectral slope are detected, geographically correlated with the albedo markings reported from the analysis of the HST and Keck disk-resolved images of Ceres (Li et al. [2006], Icarus 182, 143; Carry et al. [2008], Astron. Astrophys. 478, 235). Given the lack of constraints on the surface composition of Ceres, however, we cannot assert the causes of these variations. [less ▲]

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See detailThe C2-hydrocarbon link in cometary comae
Weiler, M.; Bockelée-Morvan, D.; Hutsemekers, Damien ULg et al

in EPSC Abstract 2012 (2012)

Comet 8P/Tuttle was the target of an ESO multiwavelength observing campaign in 2008. Observations of the spatial distribution of C2 and C3 were obtained, as well as simultaneous direct detections of the ... [more ▼]

Comet 8P/Tuttle was the target of an ESO multiwavelength observing campaign in 2008. Observations of the spatial distribution of C2 and C3 were obtained, as well as simultaneous direct detections of the C2 parent species C2H2 and C2H6. We combine these observations to investigate the origin of cometary C2. The observed C2 column densities are inconsistent with a production of C2 from C2H2, C2H6, and C3. Based on a photochemical model, we quantitatively discuss the influence of further potential C2 parent species. The assumption of C4H2 as an additional C2 parent species in comet 8P/Tuttle provides the best explanation for the observed C2 column densities. [less ▲]

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See detailA Search For 15NH2 Lines In Comet C/2002 T7 (LINEAR)
Rousselot, Philippe; Pirali, O.; Jehin, Emmanuel ULg et al

in Bulletin of the American Astronomical Society (2012), 44

The determination of isotopic ratios in comets is of primary importance for a good understanding of their origin and the formation of solar system. The [SUP]14[/SUP]N/[SUP]15[/SUP]N ratio is an ... [more ▼]

The determination of isotopic ratios in comets is of primary importance for a good understanding of their origin and the formation of solar system. The [SUP]14[/SUP]N/[SUP]15[/SUP]N ratio is an interesting tracer, because of its variability among various solar system bodies. So far it has only been measured in bright comets through optical observations of the CN radical (Arpigny et al., 2003; Manfroid et al., 2009) and millimeter observations of HCN (Bockelée-Morvan et al., 2005, 2008). The measurements give for both species the same non-terrestrial isotopic composition ([SUP]14[/SUP]N/[SUP]15[/SUP]N≈150 in comets versus 272 in the Earth atmosphere), but HCN and CN are minor species. In order to get a determination of this ratio in another molecule we have searched for [SUP]15[/SUP]NH[SUB]2[/SUB] lines in a high-resolution and high signal-to-noise ratio spectrum of comet C/2002 T7 (LINEAR) obtained with the UVES spectrometer at the VLT ESO 8-m telescope (Hutsemékers et al., 2008). This work is based on a new laboratory experiment conducted with the AILES beamline spectrometer at synchrotron SOLEIL to determine the [SUP]15[/SUP]NH[SUB]2[/SUB] wavelengths by Fourier transform spectroscopy. We will present the first results obtained from these data, which have allowed to search for the first time [SUP]15[/SUP]NH[SUB]2[/SUB] emission lines in a comet. References: Arpigny et al., 2003, Science, 301, 1522 Bockelée-Morvan et al.,2005, in Comets II, ed. M. C. Festou, H. U. Keller, & H. A. Weaver (Tucson: Univ. Arizona Press), 391 Bockelée-Morvan et al., 2008, ApJ, 679, L49 Hutsemékers et al., 2008, A&A 490, L31 Manfroid et al., 2009, A&A 503, 613 [less ▲]

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See detailWASP-43b: The closest-orbiting hot Jupiter
Hellier, Coel; Anderson, D. R.; Collier Cameron, A. et al

in Astronomy and Astrophysics (2011), 535

We report the discovery of WASP-43b, a hot Jupiter transiting a K7V star every 0.81 d. At 0.6-Msun the host star has the lowest mass of any star hosting a hot Jupiter. It also shows a 15.6-d rotation ... [more ▼]

We report the discovery of WASP-43b, a hot Jupiter transiting a K7V star every 0.81 d. At 0.6-Msun the host star has the lowest mass of any star hosting a hot Jupiter. It also shows a 15.6-d rotation period. The planet has a mass of 1.8 Mjup, a radius of 0.9 Rjup, and with a semi-major axis of only 0.014 AU has the smallest orbital distance of any known hot Jupiter. The discovery of such a planet around a K7V star shows that planets with apparently short remaining lifetimes owing to tidal decay of the orbit are also found around stars with deep convection zones. [less ▲]

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See detailA Search for Water Vaporization on Ceres
Rousselot, P.; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

in Astronomical Journal (The) (2011), 142

There are hints that the dwarf planet (1) Ceres may contain a large amount of water ice. Some models and previous observations suggest that ice could be close enough to the surface to create a flux of ... [more ▼]

There are hints that the dwarf planet (1) Ceres may contain a large amount of water ice. Some models and previous observations suggest that ice could be close enough to the surface to create a flux of water outward through the regolith. This work aims to confirm a previous detection of OH emission off the northern limb of Ceres with the International Ultraviolet Explorer (IUE). Such emission would be evidence of water molecules escaping from the dwarf planet. We used the Ultraviolet and Visual Echelle Spectrograph of the Very Large Telescope to obtain spectra off the northern and southern limbs of Ceres at several epochs. These spectra cover the 307-312 nm wavelength range corresponding to the OH (0,0) emission band, which is the brightest band of this radical, well known in the cometary spectra. These new observations, five times more sensitive than those from IUE, did not permit detection of OH around Ceres. We derive an upper limit for the water production of about ~7 × 10[SUP]25[/SUP] molecules s[SUP]-1[/SUP] and estimate the minimum thickness of the dust surface layer above the water ice layer (if present) to be about 20 m. . [less ▲]

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See detailA Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation
Sicardy, B.; Ortiz, J. L.; Assafin, M. et al

in Nature (2011), 478

The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 ... [more ▼]

The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163+/-6kilometres, density 2.52+/-0.05 grams per cm[SUP]3[/SUP] and a high visible geometric albedo, . No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ~1nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun. [less ▲]

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See detailStellar Occultations by TNOs: the January 08, 2011 by (208996) 2003 AZ84 and the May 04, 2011 by (50000) Quaoar
Braga-Ribas, F.; Sicardy, B.; Ortiz, J. L. et al

in EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, France. <A href="http://meetings.copernicus.org/epsc-dps2011">http://meetings.copernicus.org/epsc-dps2011</A>, p.1060 (2011, October 01)

Between February 2010 and May 2011, our group has observed five stellar occultations by Trans-Neptunian Objects (TNOs), giving the size and shape for some of the biggest TNO's: Varuna, Eris, 2003 AZ84 ... [more ▼]

Between February 2010 and May 2011, our group has observed five stellar occultations by Trans-Neptunian Objects (TNOs), giving the size and shape for some of the biggest TNO's: Varuna, Eris, 2003 AZ84, Makemake and Quaoar. Here we present two of them: the January 08 stellar occultation by 2003 AZ84, and the May 04 by Quaoar. For the event of 2003 AZ84 we obtained one positive and another negative occultation chords in Chile. We give a lower limit to the diameter of the TNO. The event of Quaoar was observed from 16 sites distributed in Uruguay, Argentina, Chile and Brazil. Five of them yielded positive detection of the occultation. A preliminary analysis shows that the body is probably elongated and significantly bigger than the size determined by Fraser & Brown 2010, with a diameter of 890km. Using the size determined by the occultation, we will discuss the implications for the body density and albedo determination. The upper limit of the atmosphere is also studied. [less ▲]

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See detailThe stellar occultation by Makemake on 2011 April 23
Ortiz, J. L.; Sicardy, B.; Assafin, M. et al

in EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, France. <A href="http://meetings.copernicus.org/epsc-dps2011">http://meetings.copernicus.org/epsc-dps2011</A>, p.704 (2011, October 01)

We have taken advantage of a stellar occultation by the dwarf planet Makemake on 2011 April 23, to determine several of its main physical properties. We present results from a multisite campaign with 8 ... [more ▼]

We have taken advantage of a stellar occultation by the dwarf planet Makemake on 2011 April 23, to determine several of its main physical properties. We present results from a multisite campaign with 8 positive occultation detections from 5 different sites, including data from the 8-m VLT and 3.5-m NTT telescopes in Chile, which have very high temporal resolution. Because the star was significantly fainter than Makemake (setting a record in the magnitude of a star whose occultation has been detected), the occultation resulted in a drop of just ~0.3 mag in the lightcurves. From the lightcurves we have been able to determine the size and shape of the body, its geometric albedo and constraints on its atmosphere. [less ▲]

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See detailSize, density, albedo and atmosphere limit of dwarf planet Eris from a stellar occultation
Sicardy, B.; Ortiz, J. L.; Assafin, M. et al

in EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, France. <A href="http://meetings.copernicus.org/epsc-dps2011">http://meetings.copernicus.org/epsc-dps2011</A>, p.137 (2011, October 01)

We report the observation of a multi-chord stellar occultation by the dwarf planet (136199) Eris. The event was observed on November 6, 2010 UT, from two sites in Chile. Our observation is consistent with ... [more ▼]

We report the observation of a multi-chord stellar occultation by the dwarf planet (136199) Eris. The event was observed on November 6, 2010 UT, from two sites in Chile. Our observation is consistent with a spherical Eris with radius RE=1163±6 km, density =2.52±0.05 g cm-3, and visible geometric albedo pV=0.96+0.09 -0.04. Besides being remarkably similar in size to Pluto, Eris appears as one of the intrinsically brightest objects of the solar system, with a density suggesting a mainly rocky interior. Upper limits of about 1 nbar are derived for the surface pressure of possible nitrogen, argon or methane atmospheres of the dwarf planet. [less ▲]

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See detailWASP-50 b: a hot Jupiter transiting a moderately active solar-type star
Gillon, Michaël ULg; Doyle, A. P.; Lendl, M. et al

in Astronomy and Astrophysics (2011), 533

We report the discovery by the WASP transit survey of a giant planet in a close orbit (0.0295 ± 0.0009 AU) around a moderately bright (V = 11.6, K = 10) G9 dwarf (0.89 ± 0.08 M[SUB]&sun;[/SUB], 0.84 ± 0 ... [more ▼]

We report the discovery by the WASP transit survey of a giant planet in a close orbit (0.0295 ± 0.0009 AU) around a moderately bright (V = 11.6, K = 10) G9 dwarf (0.89 ± 0.08 M[SUB]&sun;[/SUB], 0.84 ± 0.03 R[SUB]&sun;[/SUB]) in the Southern constellation Eridanus. Thanks to high-precision follow-up photometry and spectroscopy obtained by the telescopes TRAPPIST and Euler, the mass and size of this planet, WASP-50 b, are well constrained to 1.47 ± 0.09 M[SUB]Jup[/SUB] and 1.15 ± 0.05 R[SUB]Jup[/SUB], respectively. The transit ephemeris is 2 455 558.6120 (±0.0002) + N × 1.955096 (±0.000005) HJD[SUB]UTC[/SUB]. The size of the planet is consistent with basic models of irradiated giant planets. The chromospheric activity (log R'[SUB]HK = -4.67[/SUB]) and rotational period (P[SUB]rot[/SUB] = 16.3 ± 0.5 days) of the host star suggest an age of 0.8 ± 0.4 Gy that is discrepant with a stellar-evolution estimate based on the measured stellar parameters (ρ[SUB]∗[/SUB] = 1.48 ± 0.10 ρ[SUB]&sun;[/SUB], T[SUB]eff[/SUB] = 5400 ± 100 K, [Fe/H] = -0.12 ± 0.08) which favors an age of 7 ± 3.5 Gy. This discrepancy could be explained by the tidal and magnetic influence of the planet on the star, in good agreement with the observations that stars hosting hot Jupiters tend to show faster rotation and magnetic activity. We measure a stellar inclination of 84[SUB]-31[SUP]+6[/SUP][/SUB] deg, disfavoring a high stellar obliquity. Thanks to its large irradiation and the relatively small size of its host star, WASP-50 b is a good target for occultation spectrophotometry, making it able to constrain the relationship between hot Jupiters' atmospheric thermal profiles and the chromospheric activity of their host stars. The photometric time-series used in this work are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A88">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A88</A> [less ▲]

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See detailTRAPPIST: TRAnsiting Planets and PlanetesImals Small Telescope
Jehin, Emmanuel ULg; Gillon, Michaël ULg; Queloz, D. et al

in The Messenger (2011), 145

TRAPPIST is a 60-cm robotic telescope that was installed in April 2010 at the ESO La Silla Observatory. The project is led by the Astrophysics and Image Processing group (AIP) at the Department of ... [more ▼]

TRAPPIST is a 60-cm robotic telescope that was installed in April 2010 at the ESO La Silla Observatory. The project is led by the Astrophysics and Image Processing group (AIP) at the Department of Astrophysics, Geophysics and Oceanography (AGO) of the University of Liège, in close collaboration with the Geneva Observatory, and has been funded by the Belgian Fund for Scientific Research (F.R.S.-FNRS) and the Swiss National Science Foundation (SNF). It is devoted to the detection and characterisation of exoplanets and to the study of comets and other small bodies in the Solar System. We describe here the goals of the project and the hardware and present some results obtained during the first six months of operation. [less ▲]

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See detailWASP-23b: a transiting hot Jupiter around a K dwarf and its Rossiter-McLaughlin effect
Triaud, A H M J; Queloz, D.; Hellier, C. et al

in Astronomy and Astrophysics (2011), 531

We report the discovery of a new transiting planet in the southern hemisphere. It was found by the WASP-south transit survey and confirmed photometrically and spectroscopically by the 1.2 m Swiss Euler ... [more ▼]

We report the discovery of a new transiting planet in the southern hemisphere. It was found by the WASP-south transit survey and confirmed photometrically and spectroscopically by the 1.2 m Swiss Euler telescope, LCOGT 2m Faulkes South Telescope, the 60 cm TRAPPIST telescope, and the ESO 3.6 m telescope. The orbital period of the planet is 2.94 days. We find that it is a gas giant with a mass of 0.88 ± 0.10 M[SUB]J[/SUB] and an estimated radius of 0.96 ± 0.05 R[SUB]J[/SUB]. We obtained spectra during transit with the HARPS spectrograph and detect the Rossiter-McLaughlin effect despite its small amplitude. Because of the low signal-to-noise ratio of the effect and a small impact parameter, we cannot place a strong constraint on the projected spin-orbit angle. We find two conflicting values for the stellar rotation. We find, via spectral line broadening, that v sin I = 2.2 ± 0.3 km s[SUP]-1[/SUP], while applying another method, based on the activity level using the index log R'_HK, gives an equatorial rotation velocity of only v = 1.35 ± 0.20 km s[SUP]-1[/SUP]. Using these as priors in our analysis, the planet might be either misaligned or aligned. This result raises doubts about the use of such priors. There is evidence of neither eccentricity nor any radial velocity drift with time. Using WASP-South photometric observations confirmed with LCOGT Faulkes South Telescope, the 60 cm TRAPPIST telescope, the CORALIE spectrograph and the camera from the Swiss 1.2 m Euler Telescope placed at La Silla, Chile, as well as with the HARPS spectrograph, mounted on the ESO 3.6 m, also at La Silla, under proposal 084.C-0185. The data is publicly available at the CDS Strasbourg and on demand to the main author.RV data is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/531/A24">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/531/A24</A>Appendix is available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A> [less ▲]

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See detailTransiting exoplanets from the CoRoT space mission. XVII. The hot Jupiter CoRoT-17b: a very old planet
Csizmadia, Szilard; Moutou, C.; Deleuil, M. et al

in Astronomy and Astrophysics (2011), 531

We report on the discovery of a hot Jupiter-type exoplanet, CoRoT-17b, detected by the CoRoT satellite. It has a mass of 2.43 ± 0.30 M[SUB]Jup[/SUB] and a radius of 1.02 ± 0.07 R[SUB]Jup[/SUB], while its ... [more ▼]

We report on the discovery of a hot Jupiter-type exoplanet, CoRoT-17b, detected by the CoRoT satellite. It has a mass of 2.43 ± 0.30 M[SUB]Jup[/SUB] and a radius of 1.02 ± 0.07 R[SUB]Jup[/SUB], while its mean density is 2.82 ± 0.38 g/cm[SUP]3[/SUP]. CoRoT-17b is in a circular orbit with a period of 3.7681 ± 0.0003 days. The host star is an old (10.7 ± 1.0 Gyr) main-sequence star, which makes it an intriguing object for planetary evolution studies. The planet's internal composition is not well constrained and can range from pure H/He to one that can contain ~380 earth masses of heavier elements. The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain. Part of the observations were obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Based on observations made with HARPS spectrograph on the 3.6-m European Organisation for Astronomical Research in the Southern Hemisphere telescope at La Silla Observatory, Chile (ESO program 184.C-0639). Based on observations made with the IAC80 telescope operated on the island of Tenerife by the Instituto de Astrofísica de Canarias in the Spanish Observatorio del Teide. Part of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. [less ▲]

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See detailSpin-orbit measurements and refined parameters for the exoplanet systems WASP-22 and WASP-26
Anderson, D. R.; Collier Cameron, A.; Gillon, Michaël ULg et al

in Astronomy and Astrophysics (2011), 534

We report on spectroscopic and photometric observations through transits of the exoplanets WASP-22b and WASP-26b, intended to determine the systems' spin-orbit angles. We combine these data with existing ... [more ▼]

We report on spectroscopic and photometric observations through transits of the exoplanets WASP-22b and WASP-26b, intended to determine the systems' spin-orbit angles. We combine these data with existing data to refine the system parameters. We measure a sky-projected spin-orbit angle of 22 ± 16° for WASP-22b, showing the planet's orbit to be prograde and, perhaps, slightly misaligned. We do not detect the Rossiter-McLaughlin effect of WASP-26b due to its low amplitude and observation noise. We place 3-σ upper limits on orbital eccentricity of 0.063 for WASP-22b and 0.050 for WASP-26b. After refining the drift in the systemic velocity of WASP-22 found by Maxted et al. (2010, AJ, 140, 2007), we find the third body in the system to have a minimum-mass of 5.3 ± 0.3 MJup (a3 / 5 AU)2, where a3 is the orbital distance of the third body. [less ▲]

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See detailEPOXI: Comet 103P/Hartley 2 Observations from a Worldwide Campaign
Meech, K. J.; A'Hearn, M. F.; Adams, J. A. et al

in Astrophysical Journal (2011), 734(Letters), 11-9

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible ... [more ▼]

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO[SUB]2[/SUB]-driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production. [less ▲]

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See detailEarly-type stars observed in the ESO UVES Paranal Observatory Project - III. Sub-parsec and au-scale structure in the interstellar medium
Smoker, J. V.; Bagnulo, S.; Cabanac, R. et al

in Monthly Notices of the Royal Astronomical Society (2011), 414

UVES interstellar observations from the Paranal Observatory Project are presented for early-type stars located in the line of sight to the nearby open clusters IC 2391 (Omni Vel) and NGC 6475 (M7), with ... [more ▼]

UVES interstellar observations from the Paranal Observatory Project are presented for early-type stars located in the line of sight to the nearby open clusters IC 2391 (Omni Vel) and NGC 6475 (M7), with spectroscopic resolution R˜ 80 000 and signal-to-noise ratios in the Ti II (3383 Å), Ca II K, CH[SUP]+[/SUP] (4232 Å), Na I D and K I (7698 Å) lines of several hundred. The sightlines are a mixture of cluster and non-cluster objects. A total of 22 early-type stars (A and B type) are present in our sample towards IC 2391, with 21 towards NGC 6475/M7, and enable us to probe for differences in column density on scales from ˜0.07 to 7.3 and ˜0.05 to 4.9 pc in the respective clusters. Additionally, towards Praesepe the Na I D interstellar variation only is probed towards 13 sightlines and transverse scales of ˜0.16-10.7 pc at R= 70 000. Towards IC 2391 variations are found in Ti II, Ca II K and Na I D column density in different sightlines of up to 0.7, 1.0 and 1.8 dex (excluding one star), respectively. This kind of variability correlates well with the Hipparcos parallax of the objects, and probes structure within the Local Bubble. For cluster-only objects the variations are 0.3, 0.3 and 0.5 dex, respectively. For the field of view towards NGC 6475 the corresponding maximum variations are somewhat smaller, being 0.5, 0.3, 0.8 and 1.0 dex for Ti II, Ca II K, Na I and K I, respectively, for all objects and 0.4, 0.2, 0.6 and 0.7 dex for the cluster-only objects. These are uncorrelated with parallax, and again demonstrate that Ca II K tends to be more smoothly distributed than Na I D. A few likely cluster sightlines show evidence for CH[SUP]+[/SUP] and variations in this molecular species of a factor of 10 in equivalent width over sub-pc scales. Towards Praesepe variation in interstellar Na I D is small, being a maximum of only ˜0.4 dex (including measurement errors), but with fewer sightlines studied. Overall, the scatter in the data is similar for the singly ionized species Ti II and Ca II, lending more support to the hypothesis that these two species sample similar parts of the interstellar medium (ISM). This also appears to be the case for the neutral species Na I D and K I in the one cluster studied. Finally, multiple-epoch observations from a variety of archive sources are used to search for astronomical unit (au) scale structure in the ISM towards 46 sightlines. There are tentative indications of structure on scales of tens to thousands of au for three sightlines. Future observations will confirm the veracity or otherwise of the time-variable components and others presented. Based on observations taken at UT2, Kueyen, Cerro Paranal, Chile, ESO DDT programme 265.D-5655(A), UVES Paranal Observatory Project and using FEROS on the ESO 2.2-m telescope, La Silla, Chile, programme ID 078.C-0493(A), the Observatoire de Haute Provence, France, the Pic du Midi telescope, France and the AAO archive. [less ▲]

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See detailStellar Occultation by Transneptunian Object (208996) 2003 AZ84
Braga-Ribas, F.; Sicardy, B.; Colas, F. et al

in Central Bureau Electronic Telegrams (2011), 2675

CBET 2675 available at Central Bureau for Astronomical Telegrams.

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See detailOrtho-to-para Abundance Ratio (OPR) of Ammonia in 15 Comets: OPRs of Ammonia Versus 14N/15N Ratios in CN
Shinnaka, Yoshiharu; Kawakita, Hideyo; Kobayashi, Hitomi et al

in Astrophysical Journal (2011), 729

The ortho-to-para abundance ratio (OPR) of cometary molecules is considered to be one of the primordial characteristics of cometary ices. We present OPRs of ammonia (NH[SUB]3[/SUB]) in 15 comets based on ... [more ▼]

The ortho-to-para abundance ratio (OPR) of cometary molecules is considered to be one of the primordial characteristics of cometary ices. We present OPRs of ammonia (NH[SUB]3[/SUB]) in 15 comets based on optical high-dispersion spectroscopic observations of NH[SUB]2[/SUB], which is a photodissociation product of ammonia in the gaseous coma. The observations were mainly carried out with the VLT/UVES. The OPR of ammonia is estimated from the OPR of NH[SUB]2[/SUB] based on the observations of the NH[SUB]2[/SUB] (0, 9, 0) vibronic band. The absorption lines by the telluric atmosphere are corrected and the cometary C[SUB]2[/SUB] emission lines blended with NH[SUB]2[/SUB] lines are removed in our analysis. The ammonia OPRs show a cluster between 1.1 and 1.2 (this corresponds to a nuclear spin temperature of ~30 K) for all comets in our sample except for 73P/Schwassmann-Wachmann 3 (73P/SW3). Comet 73P/SW3 (both B- and C-fragments) shows the OPR of ammonia consistent with nuclear spin statistical weight ratio (1.0) that indicates a high-temperature limit as nuclear spin temperature. We compared the ammonia OPRs with other properties ([SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in CN, D/H ratios of water, and mixing ratios of volatiles). Comet 73P/SW3 is clearly different from the other comets in the plot of ammonia OPRs versus [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in CN. The ammonia OPRs of 1.0 and lower [SUP]15[/SUP]N-fractionation of CN in comet 73P/SW3 imply that icy materials in this comet formed under warmer conditions than other comets. Comets may be classified into two groups in the plot of ammonia OPRs against [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in CN. [less ▲]

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See detailTRAPPIST: a robotic telescope dedicated to the study of planetary systems
Gillon, Michaël ULg; Jehin, Emmanuel ULg; Magain, Pierre ULg et al

in EPJ Web of Conferences (2011, February 01), 11

We present here a new robotic telescope called TRAPPIST<xref ref-type="fn" rid="FN2">1</xref> (TRAnsiting Planets and PlanetesImals Small Telescope). Equipped with a high-quality CCD camera mounted on a 0 ... [more ▼]

We present here a new robotic telescope called TRAPPIST<xref ref-type="fn" rid="FN2">1</xref> (TRAnsiting Planets and PlanetesImals Small Telescope). Equipped with a high-quality CCD camera mounted on a 0.6 meter light weight optical tube, TRAPPIST has been installed in April 2010 at the ESO La Silla Observatory (Chile), and is now beginning its scientific program. The science goal of TRAPPIST is the study of planetary systems through two approaches: the detection and study of exoplanets, and the study of comets. We describe here the objectives of the project, the hardware, and we present some of the first results obtained during the commissioning phase. [less ▲]

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