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This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., A stellar occultation by Pluto was observed on 2020 June 6 with the 1.3 m and 3.6 m telescopes located at Devasthal, Nainital, India, using imaging systems in the I and H bands, respectively. From this event, we derive a surface pressure for Pluto's atmosphere of psurf=12.23-0.38+0.65 μbar. This shows that Pluto's atmosphere has been in a plateau phase since mid-2015, a result which is in excellent agreement with the Pluto volatile transport model of Meza et al. This value does not support the pressure decrease reported by independent teams, based on occultations observed in 2018 and 2019 by Young et al. and Arimatsu et al., respectively. © 2021. The Author(s). Published by the American Astronomical Society., The authors are grateful to the Directors of ARIES and IIA for granting time under Directors' Discretionary Time allotment for observing this event. The authors also thank the staff of the Devasthal Observatory and the IR Group at TIFR for their help during observations. The work leading to these results has received funding from the European Research Council under the European Community's H2020 2014-2021 ERC Grant Agreement no. 669416 "Lucky Star." Research at PRL and IIST is supported by the Department of Space, Government of India. M.A., G.B.-R., F.B.-R., and R.V.-M. thank CNPq and CAPES for grants 313144/2020-6, 314772/2020-0, 465376/2014-2, and Process 88887.310463/2018-00—Project 88887.571156/2020-00. R.V.-M. also thanks grant CNPq 304544/2017-6. P.S-S. acknowledges financial support by the Spanish grant AYA-RTI2018-098657-J-I00 "LEO-SBNAF" (MCIU/AEI/FEDER, UE)., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

Trans-Neptunian Objects (TNOs) are small bodies that orbit the Sun with a semi-major axis larger than Neptune's4. They are thought to be remnants of the Solar System primordial disk and can retain information about the early stages of our planetary system's formation. Since the discovery of Albion3 in 1992, thousands of objects were detected in this orbital region, but only the Pluto system13 and (486958) Arrokoth14 has been visited so far by a spacecraft. Detailed topographic studies of Pluto and Charon6,7 presented superficial features of ~6 km while reprocessed Voyager images of Uranus' largest satellite - Oberon, show a mountain11 of ~11 km. Discovered15 in 2002 the big TNO 2002 MS4 is dynamically classified as a hot classical TNO. Thermal measurements made by Spitzer Space Telescope and Herschel Space Observatory, resulted an area equivalent diameter16 of 934 +/- 47 km and a geometric albedo at V-band of 0.051-0.022+0.036. Stellar occultation is a ground-based method that has been presenting exciting advances in the knowledge of Centaurs' and TNOs' physical properties2,9,10,12 and rings1,8. We predicted and observed seven stellar occultations by 2002 MS4 between 2019 and 2021 under the European Research Council (ERC) Lucky Star project framework. The most successful one involved 116 telescopes from Europe, North Africa, and Western Asia on 8 August 2020. Here we will present results about 2002 MS4 size, shape and topographic features. Stellar occultation data show an equivalent diameter of about 800 +/- 24 km. On the projected northern hemisphere, they are evidence of topographic features of about 20 km. Following the procedure described by Johnson and McGetchin in 1973, and assuming that 2002 MS4 is mainly composed of ice with densities between 1.0 - 2.0 g/cm3, this object supports surface features of about 7 km. However, if we consider that ice density increases toward the object's centre, then 2002 MS4 can support more prominent features. Figure 1 presents the projected profile detected on the 8 August 2020 stellar occultation. Figure 1: blue lines are the positive detections with uncertainties in red. Green segments present the surrounding region and in black is the best projected elliptical limb. Shaded region are the solutions inside the 3σ. Next figure presents the radial dispersion of the observed points from the black ellipse as a position angle function. This angle is measured from the local North and increases toward the East (Figure 1). Shaded rectangles show the evidence of a mountain and a depression of about 20 km between 10 and 55 degrees. Figure 2: radial dispersion from better elliptical limb as a function of the position angle. Dashed green lines present the 7 km lower limit for global roughness. Shaded regions are evidence of the mountain and the depression. Additionally, the northernmost grazing light curve at 2002 MS4 acquired from Varages observatory in France presents a direct detection of a minor surface feature. Note that, in figure 3, the star partially appears before the reappearance, probably due to a depression or a local mountain. Figure 3: normalized star flux as a function of time as seen by Varages observatory. The 3 intermediate points before emersion are inside the green rectangle. Acknowledgements: F.L.R is thankful for the support of the CAPES scholarship. The following authors acknowledge the respective CNPq grants: F.B-R 309578/2017-5; R.V-M 304544/2017-5, 401903/2016-8; J.I.B.C. 308150/2016-3; M.A 427700/2018-3, 310683/2017-3, 473002/2013-2. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001 and the National Institute of Science and Technology of the e-Universe project (INCT do e-Universo, CNPq grant 465376/2014-2). G.B-R acknowledges CAPES-FAPERJ/PAPDRJ grant E26/203.173/2016, M.A FAPERJ grant E-26/111.488/2013 and A.R.G-Jr FAPESP grant 2018/11239-8. B.E.M thanks the CAPES/Cofecub-394/2016-05 grant. P.S-S. acknowledges financial support by the Spanish grant AYA-RTI2018-098657-J-I00 "LEO-SBNAF" (MCIU/AEI/FEDER, UE). We would like to acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofı́sica de Andalucı́a (SEV-2017-0709) and the financial support by the Spanish grant AYA-2017-84637-R. Part of the results were based on observations taken at the 1.6 m telescope on Pico dos Dias Observatory of the National Laboratory of Astrophysics (LNA/Brazil). Part of this work was carried out within the “Lucky Star" umbrella that aggregates the efforts of the Paris, Granada and Rio teams. It is funded by the European Research Council under the European Community’s H2020 (2014-2021/ERC Grant Agreement No. 669416). This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. References 1Braga-Ribas, F., Sicardy, B., Ortiz, J. L., et al.: 2014, Nature, 508, 72. 2Dias-Oliveira, A., Sicardy, B., Ortiz, J. L.,et al.: 2017, The Astronomical Journal, 154, 22. 3Jewitt, D., and Luu, J.: 1993, Nature, 362, 730. 4Jewitt, D., Morbidelli, A., and Rauer, H.: 2008, Saas-Fee Advanced Course 35: Trans-Neptunian Objects and Comets. 5Johnson, T. V. and McGetchin, T.R. 1973, Icarus, 18, 612. 6Moore, J. M., McKinnon, W.B., et al.: 2016, Science, 351, 1284. 7Nimmo, F., Umurhan, et al. 2017, Icarus, 287, 12. 8Ortiz, J. L., Santos-Sanz, P., Sicardy, B., et al.: 2017, Nature, 550, 219. 9Ortiz, J.L., Santos-Sanz, P., Sicardy, B., et al.: 2020, Astronomy and Astrophysics, 639, A134. 10Santos-Sanz, P., Ortiz, J. L., Sicardy, B., et al.: 2021, Monthly Notices of the Royal Astronomical Society, 501. 11Schenk, P. M. and Moore, J. M.: 2020, Philosophical Transactions of the Royal Society of London Series, A378. 12Sicardy, B., Ortiz, J. L., Assafin, M., et al.: 2011, Nature, 478, 493. 13Stern, S. A., Bagenal, F., Ennico, K. et al.: 2015, Science, 350, aad1815. 14Stern, S. A., Weaver, H. A., Spencer, J. R., et al.: 2019, Science, 364, aaw9771. 15Trujillo, C. A., Brown, M. E., Minor Planet Electronic Circulars – MPEC 2002-W27. 16Vilenius, E., Kiss, C., Mommert, M., et al.: 2012, Astronomy and Astrophysics, 541, A94.

The purpose of this study was to assess the distance between the mandibular canal and the base of the mandible in the mental foramen region, in order to determine sexual dimorphism in the Brazilian population. The assessment of this distance is also important to prevent injuries to the inferior alveolar neurovascular bundle and to avoid clinical complications during surgical procedures. Using the simplified Kalabalik and Aytuğarn method for studies in Forensic Dentistry or Anatomy, this study assessed 100 cone-beam computed tomography images of male and female patients. The distance between the inferior border of the mandibular canal and the base of the mandible in the mental foramen region was evaluated bilaterally. No significant statistical differences were found between the right and left sides of the mandible. However, statistically significant difference between the genders was found (p=0.038). The lower distance (D2) measure can be applied to determine sexual dimorphism in the Brazilian population. Further studies presenting larger samples are needed to confirm these initial findings. El objetivo de este estudio fue determinar la distancia entre el canal mandibular y la base de la mandíbula en la región del agujero mentoniano para determinar el dimorfismo sexual em la población brasileña. Esta evaluación es importante para prevenir lesiones del nervio alveolar inferior, evitando complicaciones clínicas durante los procedimientos quirúrgicos mandibulares. Utilizando el método simplificado de Kalabalik y Aytuğarn para estudios en Odontología Forense o Anatomía, el estudio utilizó 100 imágenes de Tomografía computarizada de haz cónico de pacientes de ambos sexos. La distancia entre el borde inferior del canal mandibular y la base de la mandíbula obtenidos en las regiones del foramen mental se evaluó de forma bilateral. No hubo diferencias estadísticas significativas entre los lados derecho e izquierdo de la mandíbula. Sin embargo, hubo una diferencia estadísticamente significativa entre los sexos (p=0,038). La medida de distancia inferior (D2) se puede aplicar para determinar el dimorfismo sexual en la población brasileña. Se necesitan estudios con muestras más grandes para confirmar los hallazgos iniciales. O objetivo desse estudo foi determinar a distância entre o canal mandibular e a base da mandíbula na região do forame mentual para determinar o dimorfismo sexual na população brasileira. Essa avaliação é importante para prevenir lesões no nervo alveolar inferior, evitando complicações clínicas durante procedimentos cirúrgicos mandibulares. Utilizando o método simplificado de Kalabalik and Aytuğarn para estudos em Odontologia Forense ou Anatomia, o estudo utilizou 100 imagens de tomografia computadorizada de feixe cônico de pacientes de ambos os sexos. A distância entre a borda inferior do canal da mandíbula e a base da Mandíbula obtidas nas regiões do forame mentual foi avaliada bilateralmente. Não houve diferenças estatísticas significantes entre os lados direito e esquerdo da mandíbula. No entanto, houve diferença estatística significante entre os sexos (p=0,038). A medida da distância inferior (D2) pode ser aplicada para determinar o dimorfismo sexual na população brasileira. Estudos com amostras maiores são necessários para confirmar os achados iniciais.

Full list of authors: Santos-Sanz, P.; Ortiz, J. L.; Sicardy, B.; Benedetti-Rossi, G.; Morales, N.; Fernández-Valenzuela, E.; Duffard, R.; Iglesias-Marzoa, R.; Lamadrid, J. L.; Maícas, N.; Pérez, L.; Gazeas, K.; Guirado, J. C.; Peris, V.; Ballesteros, F. J.; Organero, F.; Ana-Hernández, L.; Fonseca, F.; Alvarez-Candal, A.; Jiménez-Teja, Y. Vara-Lubiano, M.; Braga-Ribas, F.; Camargo, J. I. B.; Desmars, J.; Assafin, M.; Vieira-Martins, R.; Alikakos, J.; Boutet, M.; Bretton, M.; Carbognani, A.; Charmandaris, V.; Ciabattari, F.; Delincak, P.; Fuambuena Leiva, A.; González, H.; Haymes, T.; Hellmich, S.; Horbowicz, J.; Jennings, M.; Kattentidt, B.; Kiss, Cs; Komžík, R.; Lecacheux, J.; Marciniak, A.; Moindrot, S.; Mottola, S.; Pal, A.; Paschalis, N.; Pastor, S.; Perello, C.; Pribulla, T.; Ratinaud, C.; Reyes, J. A.; Sanchez, J.; Schnabel, C.; Selva, A.; Signoret, F.; Sonbas, E.; Alí-Lagoa, V.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., We predicted a stellar occultation of the bright star Gaia DR1 4332852996360346368 (UCAC4 385-75921) (mV = 14.0 mag) by the centaur 2002 GZ32 for 2017 May 20. Our latest shadow path prediction was favourable to a large region in Europe. Observations were arranged in a broad region inside the nominal shadow path. Series of images were obtained with 29 telescopes throughout Europe and from six of them (five in Spain and one in Greece) we detected the occultation. This is the fourth centaur, besides Chariklo, Chiron, and Bienor, for which a multichord stellar occultation is reported. By means of an elliptical fit to the occultation chords, we obtained the limb of 2002 GZ32 during the occultation, resulting in an ellipse with axes of 305 ± 17 km × 146 ± 8 km. From this limb, thanks to a rotational light curve obtained shortly after the occultation, we derived the geometric albedo of 2002 GZ32 (pV = 0.043 ± 0.007) and a 3D ellipsoidal shape with axes 366 km × 306 km × 120 km. This shape is not fully consistent with a homogeneous body in hydrostatic equilibrium for the known rotation period of 2002 GZ32. The size (albedo) obtained from the occultation is respectively smaller (greater) than that derived from the radiometric technique but compatible within error bars. No rings or debris around 2002 GZ32 were detected from the occultation, but narrow and thin rings cannot be discarded. © 2020 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society., P.S-S. acknowledges financial support by the Spanish grant AYA-RTI2018-098657-J-I00 'LEO-SBNAF' (MCIU/AEI/FEDER, UE). PS-S, JLO, NM, and RD acknowledge financial support from the State Agency for Research of the Spanish MCIU through the 'Center of Excellence Severo Ochoa' award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709), they also acknowledge the financial support by the Spanish grant AYA-2017-84637-R and the Proyecto de Excelencia de la Junta de Andalucia J.A. 2012-FQM1776. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). The research leading to these results has received funding from the European Union's Horizon 2020 Research and Innovation Programme, under Grant Agreement no. 687378, as part of the project `Small Bodies Near and Far' (SBNAF). Part of the research leading to these results has received funding from the European Research Council under the European Community's H2020 (2014-2020/ERC Grant Agreement no. 669416 `LUCKY STAR'). E.F-V. acknowledges funding through the Preeminant Postdoctoral Program of the University of Central Florida. Part of the data were collected during the photometric monitoring observations with the robotic and remotely controlled observatory at the University of Athens Observatory -UOAO (Gazeas 2016). F.J.B. acknowledges financial support by the Spanish grant AYA2016-81065-C2-2-P. A.A-C. acknowledges support from FAPERJ (grant E26/203.186/2016) and CNPq (grants 304971/20162 and 401669/2016-5). A.C. acknowledges the use of the main telescope of theAstronomical Observatory of the Autonomous Region of the Aosta Valley (OAVdA). C.K. has been supported by the grants K125015 and GINOP-2.3.2-15-2016-00003 of the National Research, Development and Innovation Office, Hungary (NKFIH). T.P. and R.K. acknowledge support from the project ITMS No. 26220120029, based on the Research and development program financed from the European Regional Development Fund and from the Slovak Research and Development Agency -the contract No. APVV-150458. We are grateful to the CAHA and OSN staffs. This research is partially based on observations collected at Centro Astronomico Hispano-Aleman (CAHA) at Calar Alto, operated jointly by Junta de Andalucia and Consejo Superior de Investigaciones Cientificas (IAA-CSIC). This research was also partially based on observation carried out at the Observatorio de Sierra Nevada (OSN) operated by Instituto de Astrofisica de Andalucia (CSIC). This article is also based on observations made with the Liverpool Telescope operated on the island of La Palma by the Instituto de Astrofisica de Canarias in the Spanish Roque de losMuchachos Observatory. Partially based on observations made with the Tx40 telescope at the Observatorio Astrofisico de Javalambre in Teruel, a Spanish Infraestructura Cientifico-Tecnica Singular (ICTS) owned, managed and operated by the Centro de Estudios de Fisica del Cosmos de Arag on (CEFCA). Tx40 is funded with the Fondos de Inversiones de Teruel (FITE). This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium).Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

Transneptunian Objects (TNOs) are the remnants of our planetary system and can retain information about the early stages of the Solar System formation. Stellar occultation is a ground-based method used to study these distant bodies which have been presenting exciting results mainly about their physical properties. The big TNO called 2002 MS4 was discovered by Trujillo, C. A., & Brown, M. E., in 2002 using observations made at the Palomar Observatory (EUA). It is classified as a hot classical TNO, with orbital parameters a = 42 AU, e = 0.139, and i = 17.7º. Using thermal measurements with PACS (Herschel) and MIPS (Spitzer Space Telescope) instruments, Vilenius et al. 2012 obtained a radius of 467 +/- 23.5 km and an albedo of 0.051. Predictions of stellar occultations by this body in 2019 were obtained using the Gaia DR2 catalogue and NIMA ephemeris (Desmars et al. 2015) and made available in the Lucky Star web page (https://lesia.obspm.fr/lucky-star/). Four events were observed in South America and Canada. The first stellar occultation was detected on 09 July 2019, resulting in two positives and four negatives chords, including a close one which proven to be helpful to constrain the body’s size. This detection also allowed us to obtain a precise astrometric position that was used to update its ephemeris and improve the predictions of the following events. Two of them were detected on 26 July 2019, separated by eight hours. The first event was observed from South America and resulted in three positive detections, while the second, observed from Canada, resulted in a single chord. Another double chord event was observed on 19 August 2019 also from Canada. Due to its size, it is expected that 2002 MS4 is in hydrostatic equilibrium. Thirouin, A. 2013 obtained a rotational light curve of 2002 MS4 and determined two possible periods (7.33 h and 10.44 h) with low amplitude variation (0.05 +/- 0.01 mag). Admitting that it has a Maclaurin shape, the projected limb in the sky plane for Earth-based observers should be the same in the 09 July and 26 July events. The multi-chord detection allows determining an interval of parameters for size and shape. Considering that the same figure should have been observed in the 09 July event, we could use the both chords and the negative observations to constrain its physical parameters. With that, we could determine that 2002 MS4 has an equivalent radius of 385 +/- 1 km (Figure 1). Our results indicate that this TNO is about 100 km smaller in diameter than the value obtained by Vilenius et al. 2012, implying an albedo of 0.076 (Hv = 4.0 +/- 0.6) . The astrometric positions derived from these data were also helpful to improve forthcoming stellar occultations, in special the one crossing Europe on 08 August this year. More data from stellar occultations and observations of rotational light curves will help to confirm these results and assumptions. Acknowledgements: F.L.R is thankful for the support of the CAPES scholarship. The following authors acknowledge the respective CNPq grants: F.B-R 309578/2017-5; R.V-M 304544/2017-5, 401903/2016-8; J.I.B.C. 308150/2016-3; M.A 427700/2018-3, 310683/2017-3, 473002/2013-2. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001 and the National Institute of Science and Technology of the e-Universe project (INCT do e-Universo, CNPq grant 465376/2014-2). G.B-R acknowledges CAPES-FAPERJ/PAPDRJ grant E26/203.173/2016, M.A FAPERJ grant E-26/111.488/2013 and A.R.G-Jr FAPESP grant 2018/11239-8. B.E.M thanks the CAPES/Cofecub-394/2016-05 grant. P.S-S. acknowledges financial support by the Spanish grant AYA-RTI2018-098657-J-I00 "LEO-SBNAF" (MCIU/AEI/FEDER, UE). We would like to acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofı́sica de Andalucı́a (SEV-2017-0709) and the financial support by the Spanish grant AYA-2017-84637-R. Part of the results were based on observations taken at the 1.6 m telescope on Pico dos Dias Observatory of the National Laboratory of Astrophysics (LNA/Brazil). Part of this work was carried out within the “Lucky Star" umbrella that agglomerates the efforts of the Paris, Granada and Rio teams. It is funded by the European Research Council under the European Community’s H2020 (2014-2020/ERC Grant Agreement No. 669416). This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. References Assafin, M. et al. PRAIA - Platform for Reduction of Astronomical Images Automatically. In: Tanga, P.; Thuillot, W. (Ed.). Gaia follow-up network for the solar system objects : Gaia FUN-SSO workshop proceedings, held at IMCCE -Paris Observatory, France, November 29 - December 1, 2010 / edited by Paolo Tanga, William Thuillot.- ISBN 2-910015-63-7, p. 85-88. [S.l.: s.n.], 2011. p. 85–88. Desmars, J. et al. Orbit determination of trans-Neptunian objects and Centaurs for the prediction of stellar occultations. Astronomy & Astrophysics, v. 584, p. A96, dez. 2015. Thirouin, A. Study of Trans-Neptunian Objects using photometric techniques and numerical simulations. Dissertation. Editorial de la Universidad de Granada. Spain, 2013. Trujillo, C. A., Brown, M. E., Minor Planet Electronic Circulars – MPEC 2002-W27. Disponível em: \url{https://minorplanetcenter.net//iau/mpec/K02/K02W27.html}. Vilenius, E. “TNOs are cool”: a survey of the trans-Neptunian region. VI. Herschel/PACS observations and thermal modelling of 19 classical Kuiper belt objects. Astronomy & Astrophysics. v. 541, A94, 2012.

1 IntroductionCentaurs are objects that orbit the Sun with semi-major axis between those of Jupiter and Neptune, according to the JPL Horizons definition https://ssd.jpl.nasa.gov/sbdb_help.cgi?class=CEN. These objects are thought to come from the trans-Neptunian region being injected into inner parts of the solar system due to planetary encounters, mostly with Neptune [1]. Therefore, centaurs present an excellent opportunity to study smaller trans-Neptunian objects much closer to the Earth, providing a better characterization of their physical properties. During the last years, there has been a growing momentum in the interest about the centaur population due to the discovery of ring systems around two of them, Chariklo [2] and Chiron [3,4], which has opened a new branch of research in order to understand how such rings are formed and how they can survive around these small bodies.(54598) Bienor is one of the largest centaurs known to date, with a diameter of ∼ 200 km estimated from Herschel Space Observatory, Spitzer Space Telescope and ALMA thermal measurements [5,6], similar to that of Chiron and Chariklo. Bienor also has ellipsoidal shape and water ice spectral features analogous to Chariklo and Chiron [7,8,9], although its rotation period of ∼ 9.14 h, without being very slow, is slightly over the average of the TNO/centaur population [10]. From the similarities with Chariklo and Chiron and from other reasons it has been proposed that Bienor could possess a ring system, similar to what has been found in the above mentioned centaurs [9].2 ObservationsWithin our program of physical characterization of TNOs and centaurs, a stellar occultation by the centaur Bienor was predicted to occur on January 11, 2019, with good observability potential. High accuracy astrometry runs were carried out to refine the prediction, and as a result, a shadow path favorable for the south of Europe was derived. This encouraged us to carry out an occultation observation campaign that resulted in 5 positive detections from 4 observing sites located in Spain and Portugal (see Figure 1 and Figure 2). Apart from occultations by the centaurs Chiron [3,4], Chariklo [2,11,12] and 2002 GZ32 [13], no other multichord occultations by centaurs had ever been obtained. 3 ResultsFrom the analysis of the occultation chords we obtain the instantaneous limb fit of Bienor at the moment of the occultation and combining this information with rotational light curves obtained shortly after the occultation, we infer the rotational phase at the time of the occultation and the three dimensional shape of this Centaur under the assumption of a triaxial ellipsoidal shape. The area-equivalent diameter and geometric albedo are also derived and its mass density can be constrained under the assumption of hydrostatic equilibrium. Our results are compared with radiometric results obtained using Herschel Space Observatory, Spitzer Space Telescope and ALMA facilities. Besides, we explored the potential presence of a ring system and we found no clear hints for rings, but constraints on debris material orbiting Bienor will be presented.Acknowlegements: P.S-S. acknowledges financial support by the Spanish grant AYA-RTI2018-098657-J-I00 "LEO-SBNAF" (MCIU/AEI/FEDER, UE). We would like to acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709) and the financial support by the Spanish grant AYA-2017-84637-R. This campaign was carried out within the “Lucky Star" umbrella that agglomerates the efforts of the Paris, Granada and Rio teams. It is funded by the European Research Council under the European Community’s H2020 (2014-2020/ERC Grant Agreement No. 669416). Part of the research leading to these results has received funding from the European Unions Horizon 2020 Research and Innovation Programme, under Grant Agreement No. 687378 (SBNAF). E.F-V acknowledges UCF 2017 Preeminent Postdoctoral Program (P3). F.L.R is thankful for the support of the CAPES scholarship.References[1] Fernandez J. A., 1980, MNRAS, 192, 481[2] Braga-Ribas F., Sicardy, B., Ortiz, J. L., et al., 2014, Nature, 508, 72[3] Ortiz J. L., Duffard, R., Pinilla-Alonso, N., et al., 2015, A&A, 576, A18[4] Ruprecht J. D., Bosh A. S., Person M. J., et al., 2015, Icarus, 252, 271[5] Duffard R., Pinilla-Alonso N., Santos-Sanz P., et al., 2014, A&A, 564, A92[6] Lellouch E., Moreno R., Müller T., et al., 2017, A&A, 608, A45[7] Dotto E., Barucci M. A., Boehnhardt H., et al., 2003, Icarus, 162, 408[8] Rabinowitz D. L., Schaefer B. E., Tourtellotte S. W., 2007, AJ, 133, 26[9] Fernández-Valenzuela E., Ortiz J. L., Duffard R. et al., 2017, MNRAS, 466, 4147[10] Thirouin A., Noll K. S., Ortiz J. L., Morales N., 2014, A&A, 569, A3[11] Bérard D., Sicardy B., Camargo J.I.B., et al., 2017, AJ, 154, 144[12] Leiva R., Sicardy B., Camargo J.I.B., et al., 2017, AJ, 154, 159[13] Santos-Sanz P., Ortiz J. L., Sicardy B., at al., submitted to MNRAS

All authors: Ortiz, J. L.; Santos-Sanz, P.; Sicardy, B.; Benedetti-Rossi, G.; Duffard, R.; Morales, N.; Braga-Ribas, F.; Fernández-Valenzuela, E.; Nascimbeni, V.; Nardiello, D.; Carbognani, A.; Buzzi, L.; Aletti, A.; Bacci, P.; Maestripieri, M.; Mazzei, L.; Mikuz, H.; Skvarc, J.; Ciabattari, F.; Lavalade, F. Scarfi, G.; Mari, J. M.; Conjat, M.; Sposetti, S.; Bachini, M.; Succi, G.; Mancini, F.; Alighieri, M.; Dal Canto, E.; Masucci, M.; Vara-Lubiano, M.; Gutiérrez, P. J.; Desmars, J.; Lecacheux, J.; Vieira-Martins, R.; Camargo, J. I. B.; Assafin, M.; Colas, F.; Beisker, W.; Behrend, R.; Mueller, T. G.; Meza, E.; Gomes-Junior, A. R.; Roques, F.; Vachier, F.; Mottola, S.; Hellmich, S.; Campo Bagatin, A.; Alvarez-Candal, A.; Cikota, S.; Cikota, A.; Christille, J. M.; Pál, A.; Kiss, C.; Pribulla, T.; Komžík, R.; Madiedo, J. M.; Charmandaris, V.; Alikakos, J.; Szakáts, R.; Farkas-Takács, A.; Varga-Verebélyi, E.; Marton, G.; Marciniak, A.; Bartczak, P.; Butkiewicz-Baķ, M.; Dudziński, G.; Alí-Lagoa, V.; Gazeas, K.; Paschalis, N.; Tsamis, V.; Guirado, J. C.; Peris, V.; Iglesias-Marzoa, R.; Schnabel, C.; Manzano, F.; Navarro, A.; Perelló, C.; Vecchione, A.; Noschese, A.; Morrone, L., Context. Deriving physical properties of trans-Neptunian objects is important for the understanding of our Solar System. This requires observational efforts and the development of techniques suitable for these studies. Aims. Our aim is to characterize the large trans-Neptunian object (TNO) 2002 TC302. Methods. Stellar occultations offer unique opportunities to determine key physical properties of TNOs. On 28 January 2018, 2002 TC302 occulted a mv ∼ 15.3 star with designation 593-005847 in the UCAC4 stellar catalog, corresponding to Gaia source 130957813463146112. Twelve positive occultation chords were obtained from Italy, France, Slovenia, and Switzerland. Also, four negative detections were obtained near the north and south limbs. This represents the best observed stellar occultation by a TNO other than Pluto in terms of the number of chords published thus far. From the 12 chords, an accurate elliptical fit to the instantaneous projection of the body can be obtained that is compatible with the near misses. Results. The resulting ellipse has major and minor axes of 543 ± 18 km and 460 ± 11 km, respectively, with a position angle of 3 ± 1 degrees for the minor axis. This information, combined with rotational light curves obtained with the 1.5 m telescope at Sierra Nevada Observatory and the 1.23 m telescope at Calar Alto observatory, allows us to derive possible three-dimensional shapes and density estimations for the body based on hydrostatic equilibrium assumptions. The effective diameter in equivalent area is around 84 km smaller than the radiometrically derived diameter using thermal data from Herschel and Spitzer Space Telescopes. This might indicate the existence of an unresolved satellite of up to ∼300 km in diameter, which is required to account for all the thermal flux, although the occultation and thermal diameters are compatible within their error bars given the considerable uncertainty of the thermal results. The existence of a potential satellite also appears to be consistent with other ground-based data presented here. From the effective occultation diameter combined with absolute magnitude measurements we derive a geometric albedo of 0.147 ± 0.005, which would be somewhat smaller if 2002 TC302 has a satellite. The best occultation light curves do not show any signs of ring features or any signatures of a global atmosphere. © ESO 2020., This research was partially based on data taken at the Sierra Nevada Observatory, which is operated by the Instituto de Astrofisica de Andalucia (CSIC). This research is also partially based on data taken at the German-Spanish Calar Alto observatory, which is jointly operated by the Max Planck Institute fur Astronomie and the Instituto de Astrofisica de Andalucia (CSIC). Part of the results were also based on observations taken at the 1.6m telescope on Pico dos Dias Observatory. This research was partially based on observations collected at the Schmidt telescope 67/92 cm (Asiago, Italy) of the INAF - Osservatorio Astronomico di Padova. Funding from Spanish projects AYA2014-56637-C2-1-P, AYA2017-89637-R, from FEDER, and Proyecto de Excelencia de la Junta de Andalucia 2012-FQM1776 is acknowledged. We would like to acknowledge financial support by the Spanish grant AYA-RTI2018-098657-JI00 "LEO-SBNAF" (MCIU/AEI/FEDER, UE) and the financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofisica de Andalucia (SEV- 2017-0709). Part of the research received funding from the European Union's Horizon 2020 Research and Innovation Programme, under grant agreement no. 687378 and from the ERC programme under Grant Agreement no. 669416 Lucky Star. The following authors acknowledge the respective CNPq grants: FB-R 309578/2017-5; RV-M 304544/2017-5, 401903/2016-8; J.I.B.C. 308150/2016-3; MA 427700/2018-3, 310683/2017-3, 473002/2013-2. This study was financed in part by the CoordenacAo de Aperfeiacoamento de Pessoal de Nivel Superior - Brasil (CAPES) - Finance Code 001 and the National Institute of Science and Technology of the e-Universe project (INCT do e-Universo, CNPq grant 465376/2014-2). GBR acknowledges CAPES-FAPERJ/PAPDRJ grant E26/203.173/2016, MA FAPERJ grant E-26/111.488/2013 and ARGJr FAPESP grant 2018/11239-8. E.F.-V. acknowledges support from the 2017 Preeminent Postdoctoral Program (P3) at UCF. C.K., R.S., A.F-T., and G.M. have been supported by the K-125015 and GINOP-2.3.2-15-2016-00003 grants of the Hungarian National Research, Development and Innovation Office (NKFIH), Hungary. G.M. was also supported by the Hungarian National Research, Development and Innovation Office (NKFIH) grant PD-128 360. R.K. and T.P. were supported by the VEGA 2/0031/18 grant. We acknowledge the use of Occult software by D. Herald.

Stellar occultations are a unique technique to access physical characteristics of distant solar system objects from the ground. They allow the measure of the size and the shape at kilometric level, the detection of tenuous atmospheres (few nanobars), and the investigation of close vicinity (satellites, rings) of Transneptunian objects and Centaurs. This technique is made successful thanks to accurate predictions of occultations. Accuracy of the predictions depends on the uncertainty in the position of the occulted star and the object's orbit. The Gaia stellar catalogue (Gaia Collaboration (2017)) now allows to get accurate astrometric stellar positions (to the mas level). The main uncertainty remains on the orbit. In this context, we now take advantage of the NIMA method (Desmars et al.(2015)) for the orbit determination and of the Gaia DR1 catalogue for the astrometry. In this document, we show how the orbit determination is improved by reducing current and some past observations with Gaia DR1. Moreover, we also use more than 45 past positive occultations observed in the 2009-2017 period to derive very accurate astrometric positions only depending on the position of the occulted stars (about few mas with Gaia DR1). We use the case of (10199) Chariklo as an illustration. The main limitation lies in the imprecision of the proper motions which is going to be solved by the Gaia DR2 release.

This article is dedicated to the memory of H.-J. Bode, J. G. Greenhill and O. Faragó for their long-standing support and participation to occultation campaigns. The work leading to these results has received funding from the European Research Council under the European Community’s H2020 2014-2020 ERC Grant Agreement n° 669416 “Lucky Star”. E.M. thanks support from Concytec-Fondecyt-PE and GA, FC-UNI for providing support during the 2012 July 18 occultation. B.S. thanks S. Para for partly supporting this research though a donation, J. P. Beaulieu for helping us accessing to the Hobart Observatory facilities and B. Warner, B. L. Gary, C. Erickson, H. Reitsema, L. Albert, P. J. Merritt, T. Hall, W. J. Romanishin, Y. J. Choi for providing data during the 2007 March 18 occultation. M.A. thanks CNPq (Grants 427700/2018-3, 310683/2017-3 and 473002/2013-2) and FAPERJ (Grant E-26/111.488/2013). J.L.O. thanks support from grant AYA2017-89637-R. P.S.S. acknowledges financial support from the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378, as part of the project “Small Bodies Near and Far” (SBNAF). J.L.O., R.D., P.S.S. and N.M. acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). F.B.R. acknowledges CNPq support process 309578/2017-5. G.B.R. thanks support from the grant CAPES-FAPERJ/PAPDRJ (E26/203.173/2016). J.I.B.C. acknowledges CNPq grant 308150/2016-3. R.V.M. thanks the grants: CNPq-304544/2017-5, 401903/2016-8, and Faperj: PAPDRJ-45/2013 and E-26/203.026/2015. B.M. thanks the CAPES/Cofecub-394/2016-05 grant and CAPES/Brazil – Finance Code 001. B.M. and A.R.G.J. were financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) – Finance Code 001. TRAPPIST-North is a project funded by the University of Liège, in collaboration with Cadi Ayyad University of Marrakech (Morocco). TRAPPIST-South is a project funded by the Belgian Fonds (National) de la Recherche Scientifique (F.R.S.-FNRS) under grant FRFC 2.5.594.09.F, with the participation of the Swiss National Science Foundation (FNS/SNSF). VSD, SPL, TRM and ULTRACAM are all supported by the STFC. K.G. acknowledges help from the team of Archenhold-Observatory, Berlin, and A.R. thanks G. Román (Granada) for help during the observation of the 2016 July 19 occultation. A.J.C.T. acknowledges support from the Spanish Ministry Project AYA2015-71718-R (including EU funds). We thank Caisey Harlingten for the repeated use of his 50 cm telescopes in San Pedro de Atacama, Chile. We thank the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. L.M. acknowledges support from the Italian Minister of Instruction, University and Research (MIUR) through FFABR 2017 fund and support from the University of Rome Tor Vergata through “Mission: Sustainability 2016” fund. The Astronomical Observatory of the Autonomous Region of the Aosta Valley (OAVdA) is managed by the Fondazione Clément Fillietroz-ONLUS, which is supported by the Regional Governmentof the Aosta Valley, the Town Municipality of Nus and the “Unité des Communes valdôtaines Mont-Émilius”. The research was partially funded by a 2016 “Research and Education”s grant from Fondazione CRT. We thank D.P. Hinson for his constructive and detailed comments that helped to improve this article., Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015. Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ~5 and ~380 km (i.e. pressures from ~ 10 μbar to 10 nbar). Results. (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ~0.3 are present at 4–7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ~20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere., European Research Council under the European Community’s H2020 2014-2020 ERC Grant Agreement n° 669416 “Lucky Star”, Grants 427700/2018-3, 310683/2017-3 and 473002/2013-2) and FAPERJ (Grant E-26/111.488/2013), Grant AYA2017-89637-R. P.S.S. acknowledges financial support from the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378, as part of the project “Small Bodies Near and Far” (SBNAF), Financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709), Support process 309578/2017-5. G.B.R. thanks support from the grant CAPES-FAPERJ/PAPDRJ (E26/203.173/2016). J.I.B.C. acknowledges CNPq grant 308150/2016-3. R.V.M. thanks the grants: CNPq-304544/2017-5, 401903/2016-8, and Faperj: PAPDRJ-45/2013 and E-26/203.026/2015. B.M. thanks the CAPES/Cofecub-394/2016-05 grant and CAPES/Brazil – Finance Code 001., Grant FRFC 2.5.594.09.F, with the participation of the Swiss National Science Foundation (FNS/SNSF), Support from the Spanish Ministry Project AYA2015-71718-R (including EU funds), Support from the Italian Minister of Instruction, University and Research (MIUR) through FFABR 2017 fund and support from the University of Rome Tor Vergata through “Mission: Sustainability 2016” fund

Transneptunian objects (TNOs) are a source of invaluable information to access the history and evolution of the outer solar system. However, observing these faint objects is a difficult task. As a consequence, important properties such as size and albedo are known for only a small fraction of them. Now, with the results from deep sky surveys and the Gaia space mission, a new exciting era is within reach as accurate predictions of stellar occultations by numerous distant small solar system bodies become available. From them, diameters with kilometer accuracies can be determined. Albedos, in turn, can be obtained from diameters and absolute magnitudes. We use observations from the Dark Energy Survey (DES) from November 2012 until February 2016, amounting to 4292847 CCD frames. We searched them for all known small solar system bodies and recovered a total of 202 TNOs and Centaurs, 63 of which have been discovered by the DES collaboration until the date of this writing. Their positions were determined using the Gaia Data Release 2 as reference and their orbits were refined. Stellar occultations were then predicted using these refined orbits plus stellar positions from Gaia. These predictions are maintained, and updated, in a dedicated web service. The techniques developed here are also part of an ambitious preparation to use the data from the Large Synoptic Survey Telescope (LSST), that expects to obtain accurate positions and multifilter photometry for tens of thousands of TNOs., 25 pages, submitted to Astronomical Journal

Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., Context. From 1988 to 2016, several stellar occultations have been observed to characterise Pluto's atmosphere and its evolution. From each stellar occultation, an accurate astrometric position of Pluto at the observation epoch is derived. These positions mainly depend on the position of the occulted star and the precision of the timing. Aims. We present 19 Pluto's astrometric positions derived from occultations from 1988 to 2016. Using Gaia DR2 for the positions of the occulted stars, the accuracy of these positions is estimated at 2-10 mas, depending on the observation circumstances. From these astrometric positions, we derive an updated ephemeris of Pluto's system barycentre using the NIMA code. Methods. The astrometric positions were derived by fitting the light curves of the occultation by a model of Pluto's atmosphere. The fits provide the observed position of the centre for a reference star position. In most cases other publications provided the circumstances of the occultation such as the coordinates of the stations, timing, and impact parameter, i.e. the closest distance between the station and centre of the shadow. From these parameters, we used a procedure based on the Bessel method to derive an astrometric position. Results. We derive accurate Pluto's astrometric positions from 1988 to 2016. These positions are used to refine the orbit of Pluto'system barycentre providing an ephemeris, accurate to the milliarcsecond level, over the period 2000-2020, allowing for better predictions for future stellar occultations.© J. Desmars et al. 2019., Part of the research leading to these results has received funding from the European Research Council under the European Community's H2020 (2014 2020/ERC Grant Agreement No. 669416 >LUCKY STAR>). This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processedby the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium).Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. J.I.B.C. acknowledges CNPq grant 308150/2016-3. M.A. thanks CNPq (Grants 427700/2018-3, 310683/2017-3 and 473002/2013-2) and FAPERJ (Grant E-26/111.488/2013). G.B.R. is thankful for the support of the CAPES (203.173/2016) and FAPERJ/PAPDRJ (E26/200.464/2015-227833) grants. This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior -Brasil (CAPES) -Finance Code 001. F.B.R. acknowledges CNPq grant 309578/2017-5. A.R.G-J thanks FAPESP proc. 2018/11239-8. R.V-M thanks grants: CNPq-304544/2017-5, 401903/2016-8, Faperj: PAPDRJ-45/2013 and E-26/203.026/2015 P.S.-S. acknowledges financial support by the European Union's Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378, as part of the project > Small Bodies Near and Far> (SBNAF).

Distant objects in the solar system are crucial to better understand the history and evolution of its outskirts. The stellar occultation technique allows the determination of their sizes and shapes with kilometric accuracy, a detailed investigation of their immediate vicinities, as well as the detection of tenuous atmospheres. The prediction of such events is a key point in this study, and yet accurate enough predictions are available to a handful of objects only. In this work, we briefly discuss the dramatic impact that both the astrometry from the Gaia space mission and the deep sky surveys -- the Large Synoptic Survey Telescope in particular -- will have on the prediction of stellar occultations and how they may influence the future of the study of distant small solar system bodies through this technique., 10 pages, 3 figures, ACM2017

Ortiz, José Luis et. al., Haumea-one of the four known trans-Neptunian dwarf planets- is a very elongated and rapidly rotating body1-3. In contrast to other dwarf planets4-6, its size, shape, albedo and density are not well constrained. The Centaur Chariklo was the first body other than a giant planet known to have a ring system7, and the Centaur Chiron was later found to possess something similar to Chariklo's rings8,9. Here we report observations from multiple Earth-based observatories of Haumea passing in front of a distant star (a multichord stellar occultation). Secondary events observed around the main body of Haumea are consistent with the presence of a ring with an opacity of 0.5, width of 70 kilometres and radius of about 2,287 kilometres. The ring is coplanar with both Haumea's equator and the orbit of its satellite Hi'iaka. The radius of the ring places it close to the 3:1 mean-motion resonance with Haumea's spin period-that is, Haumea rotates three times on its axis in the time that a ring particle completes one revolution. The occultation by the main body provides an instantaneous elliptical projected shape with axes of about 1,704 kilometres and 1,138 kilometres. Combined with rotational light curves, the occultation constrains the three-dimensional orientation of Haumea and its triaxial shape, which is inconsistent with a homogeneous body in hydrostatic equilibrium. Haumea's largest axis is at least 2,322 kilometres, larger than previously thought, implying an upper limit for its density of 1,885 kilograms per cubic metre and a geometric albedo of 0.51, both smaller than previous estimates1,10,11. In addition, this estimate of the density of Haumea is closer to that of Pluto than are previous estimates, in line with expectations. No global nitrogen- or methane-dominated atmosphere was detected.© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved., J.L.O. acknowledges funding from Spanish and Andalusian grants MINECO AYA-2014-56637-C2-1-P and J. A. 2012-FQM1776 as well as FEDER funds. Part of the research leading to these results received funding from the European Union's Horizon 2020 Research and Innovation Programme, under grant agreement no. 687378. B.S. acknowledges support from the French grants 'Beyond Neptune' ANR-08-BLAN-0177 and 'Beyond Neptune II' ANR-11-1S56-0002. Part of the research leading to these results has received funding from the European Research Council under the European Community's H2020 (2014-2020/ERG grant agreement no. 669416 'Lucky Star'). A.P. and R.S. have been supported by the grant LP2012-31 of the Hungarian Academy of Sciences. All of the Hungarian contributors acknowledge the partial support from K-125015 grant of the National Research, Development and Innovation Office (NKFIH). G.B.-R., F.B.-R., F.L.R., R.V.-M., J.I.B.C., M.A., A.R.G.-J. and B.E.M. acknowledge support from CAPES, CNPq and FAPERJ. J.C.G. acknowledges funding from AYA2015-63939-C2-2-P and from the Generalitat Valenciana PROMETEOII/2014/057. K.H. and P.P. were supported by the project RVO:67985815. The Astronomical Observatory of the Autonomous Region of the Aosta Valley acknowledges a Shoemaker NEO Grant 2013 from The Planetary Society. We acknowledge funds from a 2016 'Research and Education' grant from Fondazione CRT. We also acknowledge the Slovakian project ITMS no. 26220120029.

International audience; We present results from a multi-chord Pluto stellar occultation observed on 2015 June 29 from New Zealand and Australia. This occurred only two weeks before the NASA New Horizons flyby of the Pluto system and serves as a useful comparison between ground-based and space results. We find that Pluto's atmosphere is still expanding, with a significant pressure increase of 5 ± 2% since 2013 and a factor of almost three since 1988. This trend rules out, as of today, an atmospheric collapse associated with Pluto's recession from the Sun. A central flash, a rare occurrence, was observed from several sites in New Zealand. The flash shape and amplitude are compatible with a spherical and transparent atmospheric layer of roughly 3 km in thickness whose base lies at about 4 km above Pluto's surface, and where an average thermal gradient of about 5 K km−1 prevails. We discuss the possibility that small departures between the observed and modeled flash are caused by local topographic features (mountains) along Pluto's limb that block the stellar light. Finally, using two possible temperature profiles, and extrapolating our pressure profile from our deepest accessible level down to the surface, we obtain a possible range of 11.9–13.7 μbar for the surface pressure.

We report on the results of a six-month photometric study of the main-belt binary C-type asteroid 121 Hermione, performed during its 2007 opposition. We took advantage of the rare observational opportunity afforded by one of the annual equinoxes of Hermione occurring close to its opposition in June 2007. The equinox provides an edge-on aspect for an Earth-based observer, which is well suited to a thorough study of Hermione's physical characteristics. The catalog of observations carried out with small telescopes is presented in this work, together with new adaptive optics (AO) imaging obtained between 2005 and 2008 with the Yepun 8-m VLT telescope and the 10-m Keck telescope. The most striking result is confirmation that Hermione is a bifurcated and elongated body, as suggested by Marchis et al., (2005). A new effective diameter of 187 +/- 6 km was calculated from the combination of AO, photometric and thermal observations. The new diameter is some 10% smaller than the hitherto accepted radiometric diameter based on IRAS data. The reason for the discrepancy is that IRAS viewed the system almost pole-on. New thermal observations with the Spitzer Space Telescope agree with the diameter derived from AO and lightcurve observations. On the basis of the new AO astrometric observations of the small 32-km diameter satellite we have refined the orbit solution and derived a new value of the bulk density of Hermione of 1.4 +0.5/-0.2 g cm-3. We infer a macroscopic porosity of ~33 +5/-20%., Comment: 39 pages, 4 Tables, 8 figures

At the IAU XXVI General Assembly in 2006, the Division I decided to create the Working Group on Astrometry by Small Ground-Based Telescopes (WG-ASGBT). Its scientic goals are to foster the follow-up of small bodies detected by the large surveys including the NEOs; to set-up a dedicated observation network for the follow-up of objects which will be detected by Gaia; to contribute to the observation campaigns of the mutual events of natural satellites, stellar occultations, and binary asteroids; and to encourage teaching astrometry for the next generation. The present report gives the main activities carried out in these areas with small telescopes (diameter less than 2m).

We present astrometric positions of Uranus and its satellites Miranda, Ariel, Umbriel, Titania, and Oberon, determined in the International Celestial Reference System, from 1758 frames observed over 105 nights between 1982 and 1998. All the positions of the satellites were reduced using secondary frames referred to the Tycho-2 Catalogue from photographic plates and CCD frames obtained with the 1.6 m reflector at the Laboratorio Nacional de Astrofisica in Brazil. The images of Uranus were overexposed and thus not were measured in the frames. Its positions were instead calculated from the satellites, with the exception of Miranda, using their differential positions as given by the ephemeris GUST86. The positions of the planet were compared with the planetary ephemeris DE403, and the residuals have a mean and standard deviation, respectively, of -009 and 014 for (O-C)α and -001 and 015 for (O-C)δ. The results are similar for the satellites.

The recent discovery of two asteroids with unstable orbits in the neighborhood of the 5 : 2 resonance raises the question whether there exist unstable asteroids in the neighborhood of the more important 3 : 1 asteroidal resonance. The two asteroids have short dynamical lifetimes of about 10 and 50 Myr. Semimajor-axis drift due to the Yarkovsky effect can explain their existence in such a short-lived orbit. Since this effect is not specific to the 5 : 2 resonance, a natural question is whether there exist short-lived asteroids near other resonance borders. This question is interesting because by studying such objects we can better understand the production of near-Earth asteroids (NEAs) via the collision and Yarkovsky processes. We search for short-lived asteroids in the neighborhood of the 3 : 1 resonance. The borders of this resonance and the positions of the asteroids with respect to them are determined by using the mean elliptic planar restricted three-body problem and a method that invokes the concept of a "representative plane." A semianalytical global study of the orbits for this nonlinear dynamical system is made through this convenient plane. The limit between the circulation and libration or chaotic orbits in this simple problem is taken as the edge of the resonance. We then choose 41 numbered asteroids that are closest to the resonance borders and have inclinations smaller than 10°. The orbits of these asteroids are numerically integrated using the full equations of motion in the gravitational field of the Sun and the planets Jupiter, Saturn, Mars, Earth, and Venus. We find that about 40% of the studied asteroids enter into the 3 : 1 resonance within 100 Myr and are subsequently dynamical eliminated. The existence of a nonnegligible number of asteroids in the 3 : 1 resonance neighborhood implies that a process must be continually acting to replenish this region. We suggest that these asteroids may have wandered to the resonance borders through small semimajor-axis displacements due to the Yarkovsky effect. This result also confirms that asteroids are continually feeding the chaotic 3 : 1 resonance region and consequently the Mars crossers and NEA population.

To take full advantage of the September 2008 opposition passage of the M-type asteroid (216) Kleopatra, we have used near-infrared adaptive optics (AO) imaging with the W.M. Keck II telescope to capture unprecedented high resolution images of this unusual asteroid. Our AO observations with the W.M. Keck II telescope, combined with Spitzer/IRS spectroscopic observations and past stellar occultations, confirm the value of its IRAS radiometric radius of 67.5 km as well as its dog-bone shape suggested by earlier radar observations. Our Keck AO observations revealed the presence of two small satellites in orbit about Kleopatra (see Marchis et al., 2008). Accurate measurements of the satellite orbits over a full month enabled us to determine the total mass of the system to be 4.64+/-0.02 10^18 Kg. This translates into a bulk density of 3.6 +/-0.4 g/cm3, which implies a macroscopic porosity for Kleopatra of ~ 30-50%, typical of a rubble-pile asteroid. From these physical characteristics we measured its specific angular momentum, very close to that of a spinning equilibrium dumbbell., Comment: 35 pages, 3 Tables, 9 Figures. In press to Icarus

A long-term adaptive optics (AO) campaign of observing the double Asteroid (90) Antiope has been carried out in 2003–2005 using 8–10-m class telescopes, allowing prediction of the circumstances of mutual events occurring during the July 2005 opposition [Marchis, F., Descamps, P., Hestroffer, D., Berthier, J., de Pater, I., 2004. Bull. Am. Astron. Soc. 36, 1180]. This is the first opportunity to use complementary lightcurve and AO observations to extensively study the (90) Antiope system, an interesting visualized binary doublet system located in the main belt. The orbital parameters derived from the AO observations have served as input quantities for the derivation of a whole set of other physical parameters (namely shapes, surface scattering, bulk density, and internal properties) from analysis of collected lightcurves. To completely model the observed lightcurves, we employed Roche figures to construct an overall shape solution. The combination of these complementary observations has enabled us to derive a reliable physical and orbital solution for the system. Our model is consistent with a system of slightly non-spherical components, having a size ratio of 0.95 (with R avg = 42.9 ± 0.5 km , separation = 171 ± 1 km ), and exhibiting equilibrium figures for homogeneous rotating bodies. A comparison with grazing occultation event lightcurves suggests that the real shapes of the components do not depart from Roche equilibrium figures by more than 10%. The J2000 ecliptic coordinates of the pole of the system are λ n = 200 ° ± 2 ° and α n = 38 ° ± 2 ° . The orbital period was refined to P = 16.5051 ± 0.0001 h , and the density is found to be slightly lower than previous determinations, with a value of 1.25 ± 0.05 g / cm 3 , leading to a significant macro-porosity of 30%. Possible scenarios for the origin of the system are also discussed.

The original publication is available at http://iopscience.iop.org/1538-3881/; International audience; Pluto and its main satellite, Charon, occulted the same star on 2008 June 22. This event was observed from Australia and La Réunion Island, providing the east and north Charon Plutocentric offset in the sky plane (J2000): X= + 12,070.5 ± 4 km (+ 546.2 ± 0.2 mas), Y= + 4,576.3 ± 24 km (+ 207.1 ± 1.1 mas) at 19:20:33.82 UT on Earth, corresponding to JD 2454640.129964 at Pluto. This yields Charon's true longitude L= 153.483 ± 0fdg071 in the satellite orbital plane (counted from the ascending node on J2000 mean equator) and orbital radius r= 19,564 ± 14 km at that time. We compare this position to that predicted by (1) the orbital solution of Tholen & Buie (the "TB97" solution), (2) the PLU017 Charon ephemeris, and (3) the solution of Tholen et al. (the "T08" solution). We conclude that (1) our result rules out solution TB97, (2) our position agrees with PLU017, with differences of ΔL= + 0.073 ± 0fdg071 in longitude, and Δr= + 0.6 ± 14 km in radius, and (3) while the difference with the T08 ephemeris amounts to only ΔL= 0.033 ± 0fdg071 in longitude, it exhibits a significant radial discrepancy of Δr= 61.3 ± 14 km. We discuss this difference in terms of a possible image scale relative error of 3.35 × 10-3in the 2002-2003 Hubble Space Telescope images upon which the T08 solution is mostly based. Rescaling the T08 Charon semi-major axis, a = 19, 570.45 km, to the TB97 value, a = 19636 km, all other orbital elements remaining the same ("T08/TB97" solution), we reconcile our position with the re-scaled solution by better than 12 km (or 0.55 mas) for Charon's position in its orbital plane, thus making T08/TB97 our preferred solution.

We present a Véron & Véron based optical extragalactic reference frame progress report.

We present results derived from four stellar occultations by the plutino object (208996) 2003~AZ$_{84}$, detected at January 8, 2011 (single-chord event), February 3, 2012 (multi-chord), December 2, 2013 (single-chord) and November 15, 2014 (multi-chord). Our observations rule out an oblate spheroid solution for 2003~AZ$_{84}$'s shape. Instead, assuming hydrostatic equilibrium, we find that a Jacobi triaxial solution with semi axes $(470 \pm 20) \times (383 \pm 10) \times (245 \pm 8)$~km % axis ratios $b/a= 0.82 \pm 0.05$ and $c/a= 0.52 \pm 0.02$, can better account for all our occultation observations. Combining these dimensions with the rotation period of the body (6.75~h) and the amplitude of its rotation light curve, we derive a density $��=0.87 \pm 0.01$~g~cm$^{-3}$ a geometric albedo $p_V= 0.097 \pm 0.009$. A grazing chord observed during the 2014 occultation reveals a topographic feature along 2003~AZ$_{84}$'s limb, that can be interpreted as an abrupt chasm of width $\sim 23$~km and depth $> 8$~km or a smooth depression of width $\sim 80$~km and depth $\sim 13$~km (or an intermediate feature between those two extremes).