Publications of Jean Manfroid
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See detailIsotopic Ratios in a Peculiar Outbursting Comet
Yang, Bin; Hutsemekers, Damien ULiege; Shinnaka, Yoshiharu et al

in Bulletin of the American Astronomical Society (2017, October 01), 49

Isotopic ratios in comets provide keys for the understanding of the origin of cometary material, and the physical and chemical conditions in the early Solar Nebula. A newly discovered peculiar comet, C ... [more ▼]

Isotopic ratios in comets provide keys for the understanding of the origin of cometary material, and the physical and chemical conditions in the early Solar Nebula. A newly discovered peculiar comet, C/2015 ER61, underwent an outburst with a total brightness increase of 2 magnitudes on the night of April 4th, 2017. The sharp increase in brightness offers a rare opportunity to measure the isotopic ratios of the light elements of this comet. We obtained two high-resolution spectra of C/2015 ER61 with UVES on Apr. 13 and Apr. 17 respectively. At the time of our observations, the comet was fading gradually since the outburst. We measured the 12C/13C and 14N/15N isotopic ratios from the CN Violet (0,0) band. In addition, we determined the 14N/15N ratio in NH2 for C/2015 ER61 from four pairs of NH2 isotopologue lines. Some 18OH lines were detected but the S/N of these lines is too low to derive a reliable 18O/16O estimate. We will present our UVES spectra of C/2015 ER61, obtained shortly after the outburst. We will also present the comparison of the Isotopic ratios of C/2015 ER61 with those of other comets. [less ▲]

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See detailGround-based monitoring of comet 67P/Churyumov–Gerasimenko gas activity throughout the Rosetta mission
Opitom, C.; Snodgrass, C.; Fitzsimmons, A. et al

in Monthly Notices of the Royal Astronomical Society (2017), 469

Simultaneously to the ESA Rosetta mission, a world-wide ground-based campaign provided measurements of the large scale activity of comet 67P/Churyumov-Gerasimenko through measurement of optically active ... [more ▼]

Simultaneously to the ESA Rosetta mission, a world-wide ground-based campaign provided measurements of the large scale activity of comet 67P/Churyumov-Gerasimenko through measurement of optically active gas species and imaging of the overall dust coma. We present more than 2 yr of observations performed with the FORS2 low-resolution spectrograph at the VLT, TRAPPIST and ACAM at the WHT. We focus on the evolution of the CN production as a tracer of the comet activity. We find that it is asymmetric with respect to perihelion and different from that of the dust. The CN emission is detected for the first time at 1.34 au pre-perihelion and production rates then increase steeply to peak about 2 weeks after perihelion at (1.00 ± 0.10) × 10[SUP]25[/SUP] molecules s[SUP]-1[/SUP], while the post-perihelion decrease is more shallow. The evolution of the comet activity is strongly influenced by seasonal effects with enhanced CN production when the Southern hemisphere is illuminated. [less ▲]

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See detailStudy of the plutino object (208996) 2003 AZ84 from stellar occultations: size, shape and topographic features
Dias-Oliveira, A.; Sicardy, B.; Ortiz, J. L. et al

in The Astronomical Journal (2017), 154(1), 13

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 ... [more ▼]

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 $\rho=0.87 \pm 0.01$~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). [less ▲]

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See detailThe 67P/Churyumov-Gerasimenko observation campaign in support of the Rosetta mission
Snodgrass, C.; A'Hearn, M. F.; Aceituno, F. et al

in Philosophical Transactions : Mathematical, Physical & Engineering Sciences (2017), 375

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko ... [more ▼]

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

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See detailTrappist-1 et les sept planètes
Manfroid, Jean ULiege; Désamoré, Luc

Article for general public (2017)

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See detailObservational signatures of past mass-exchange episodes in massive binaries: the case of LSS 3074
Raucq, Françoise ULiege; Gosset, Eric ULiege; Rauw, Grégor ULiege et al

in Astronomy and Astrophysics (2017), 601

Context. The role of mass and momentum exchanges in close massive binaries is very important in the subsequent evolution of the components. Such exchanges produce several observational signatures such as ... [more ▼]

Context. The role of mass and momentum exchanges in close massive binaries is very important in the subsequent evolution of the components. Such exchanges produce several observational signatures such as asynchronous rotation and altered chemical compositions, that remain after the stars detach again. Aims. We investigated these effects for the close O-star binary LSS 3074 (O4 f + O6-7:(f):), which is a good candidate for a past Roche lobe overflow (RLOF) episode because of its very short orbital period, P = 2.185 days, and the luminosity classes of both components. Methods.We determined a new orbital solution for the system. We studied the photometric light curves to determine the inclination of the orbit and Roche lobe filling factors of both stars. Using phase-resolved spectroscopy, we performed the disentangling of the optical spectra of the two stars.We then analysed the reconstructed primary and secondary spectra with the CMFGEN model atmosphere code to determine stellar parameters, such as the effective temperatures and surface gravities, and to constrain the chemical composition of the components. Results. We confirm the apparent low stellar masses and radii reported in previous studies. We also find a strong overabundance in nitrogen and a strong carbon and oxygen depletion in both primary and secondary atmospheres, together with a strong enrichment in helium of the primary star. Conclusions. We propose several possible evolutionary pathways through a RLOF process to explain the current parameters of the system. We confirm that the system is apparently in overcontact configuration and has lost a significant portion of its mass to its surroundings. We suggest that some of the discrepancies between the spectroscopic and photometric properties of LSS 3074 could stem from the impact of a strong radiation pressure of the primary. [less ▲]

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See detailL'astronomie dans le monde - 12/2016
Manfroid, Jean ULiege

Article for general public (2016)

Expansion de l’Univers –Halos autour de quasars – ST11 – Voie lactée (I) et (II) – Surpopulation – 2014 UZ224 – Schiaparelli – 2007 OR10

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See detailOrtho-to-para abundance ratios of NH2in 26 comets: implications for the real meaning of OPRs
Shinnaka, Yoshiharu; Kawakita, Hideyo; Jehin, Emmanuel ULiege et al

in Monthly Notices of the Royal Astronomical Society (2016), 462

Abundance ratios of nuclear-spin isomers for cometary molecules having identical protons, such as water and ammonia, have been measured and discussed from the viewpoint that they are primordial characters ... [more ▼]

Abundance ratios of nuclear-spin isomers for cometary molecules having identical protons, such as water and ammonia, have been measured and discussed from the viewpoint that they are primordial characters in comet. In the case of ammonia, its ortho-to-para abundance ratio (OPR) is usually estimated from OPRs of NH2 because of difficulty in measuring OPR of ammonia directly. We report our survey for OPRs of NH2 in 26 comets. A weighted mean of ammonia OPRs for the comets is 1.12 ± 0.01 and no significant difference is found between the Oort Cloud comets and the Jupiter-family comets. These values correspond to ∼30 K as nuclear-spin temperatures. The OPRs of ammonia in comets probably reflect the physicochemical conditions in coma, rather than the conditions for the molecular formation or condensation in the pre-solar molecular cloud/the solar nebula, based on comparison of OPRs (and nuclear-spin temperatures) of ammonia with those of water, 14N/15N ratios in ammonia, and D/H ratios in water. The OPRs could be reset to a nuclear-spin weights ratio in solid phase and modified by interactions with protonated ions like H3O+, water clusters (H2O)n, ice grains, and paramagnetic impurities (such as O2 molecules and grains) in the inner coma gas. Relationship between the OPRs of ammonia and water is a clue to understanding the real meaning of the OPRs. [less ▲]

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See detailNitrogen isotopic ratios of NH 2 in comets: implication for 15 N-fractionation in cometary ammonia
Shinnaka, Yoshiharu; Kawakita, Hideyo; Jehin, Emmanuel ULiege et al

in Monthly Notices of the Royal Astronomical Society (2016), 462

The isotopic ratios are diagnostics for the physico-chemical conditions governing molecular formation. In comets, 14N/15N ratios have been measured from HCN in three comets and from CN in more than 20 ... [more ▼]

The isotopic ratios are diagnostics for the physico-chemical conditions governing molecular formation. In comets, 14N/15N ratios have been measured from HCN in three comets and from CN in more than 20 comets. Those ratios are enriched in 15N compared to the Sun by a factor of ∼3, have a small diversity and do not depend on the dynamical type of the comets. The origin of this high 15N-fractionation is still in debate because CN probably comes not only from HCN, but also from other materials (such as polymers or organic dusts) in the coma. Consequently, an interpretation of the isotopic ratios in cometary CN is quite complicated due to the multiple possible parents of CN. In contrast with CN, the isotopic ratios of nitrogen in NH3 give us a much clearer interpretation than in CN because NH3 is directly incorporated in the nuclear ices. To estimate the 14N/15N ratios in NH3, 14N/15N ratios have been determined from high-resolution spectra of NH2 in the optical wavelength region. NH2 is indeed a dominant photodissociation product of NH3. Those ratios were also found to be enriched in 15N compared to the Sun by a factor of ∼3. In this paper, we present 14N/15N ratios in NH2 for an additional sample of 16 comets. Our sample includes short-period comets as well as long-period comets. We found that the 14N/15N ratios in cometary NH2 also show a small dispersion and do not depend on the dynamical origin of the comets. [less ▲]

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See detailL'astronomie dans le monde - 11/2016
Manfroid, Jean ULiege

Article for general public (2016)

Gravity – LAB-1 – Gaia – Météorite record – RCW103 – Mars – Le cœur de Pluton – Comète 332P – Un trou noir affamé – Champ Hubble Ultra-profond

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See detailThe OD/OH Isotope Ratio in Comets 8P/Tuttle and C/2012 F6 (Lemmon)
Rousselot, Philippe; Jehin, Emmanuel ULiege; Hutsemekers, Damien ULiege et al

in Bulletin of the American Astronomical Society (2016, October 01), 48

The determination of isotopic ratios in solar system objects is an important source of information about their origin, especially for comets. Among these ratios the D/H is of particular importance because ... [more ▼]

The determination of isotopic ratios in solar system objects is an important source of information about their origin, especially for comets. Among these ratios the D/H is of particular importance because of its sensitivity to fractionation processes and physical environment, and the abundance of hydrogen in the solar system. The main molecule used to derive this ratio in comets is water. So far, apart water, only HCN has permitted to derive D/H ratio and not only upper limits.Most of the existing determinations of D/H in water molecules have been obtained by spectroscopic observations of water lines in the sub-mm or near infrared range [1,2]. So far only one measurement has been based on OD/OH emission lines radicals in the near-UV [3] and another one on the Lyman-alpha D emission [4]. In situ measurements have also been obtained in comets 1P/Halley and 67P/Churyumov-Gerasimenko using mass spectrometer [5,6,7,8].In this work we have used the OH and OD ultraviolet bands at 310 nm observed with the ESO 8-m Very Large Telescope feeding the Ultraviolet-Visual Echelle Spectrograph (UVES) for measuring the D/H ratio in comets 8P/Tuttle and C/2012 F6 (Lemmon). The OH and OD being the photodissociation products of H[SUB]2[/SUB]O and HDO such observations allow to derive D/H ratio for water molecules. This work constitutes an independant determination of the D/H ratios already published for these comets and based on observations performed in the sub-mm and near infrared range of H[SUB]2[/SUB]O and HDO lines. We present our modeling, data analysis and numerical values obtained for this ratio.[1] D. Bockelée-Morvan et al., 2015, SSR 197, 47-83 [2] N. Biver et al., 2016, A&A 589, id A78, 11p [3] D. Hutsemékers et al., 2008, A&A 490, L31 [4] H.A. Weaver et al., 2008, LPI Contributions 1405, 8216 [5] H. Balsiger, K. Altwegg, J. Geiss, 1995, JGR 100, 5827 [6] P. Eberhardt et al., 1995, A&A 302, 301 [7] R.H. Brown et al., 2012, PSS 60, 166 [8] K. Alwegg et al., 2015, Science 347, article id. 1261952 [less ▲]

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See detailSurvey for Ortho-to-Para Abundance Ratios (OPRs) of NH2 in Comets: Revisit to the Meaning of OPRs of Cometary Volatiles
Kawakita, Hideyo; Shinnaka, Yoshiharu; Jehin, Emmanuel ULiege et al

in Bulletin of the American Astronomical Society (2016, October 01), 48

Since molecules having identical protons can be classified into nuclear-spin isomers (e.g., ortho-H[SUB]2[/SUB]O and para-H[SUB]2[/SUB]O for water) and their inter-conversions by radiative and non ... [more ▼]

Since molecules having identical protons can be classified into nuclear-spin isomers (e.g., ortho-H[SUB]2[/SUB]O and para-H[SUB]2[/SUB]O for water) and their inter-conversions by radiative and non-destructive collisional processes are believed to be very slow, the ortho-to-para abundance ratios (OPRs) of cometary volatiles such as H[SUB]2[/SUB]O, NH[SUB]3[/SUB] and CH[SUB]4[/SUB] in coma have been considered as primordial characters of cometary molecules [1]. Those ratios are usually interpreted as nuclear-spin temperatures although the real meaning of OPRs is in strong debate. Recent progress in laboratory studies about nuclear-spin conversion in gas- and solid-phases [2,3] revealed short-time nuclear-spin conversions for water, and we have to reconsider the interpretation for observed OPRs of cometary volatiles. We have already performed the survey for OPRs of NH[SUB]2[/SUB] in more than 20 comets by large aperture telescopes with high-resolution spectrographs (UVES/VLT, HDS/Subaru, etc.) in the optical wavelength region [4]. The observed OPRs of ammonia estimated from OPRs of NH[SUB]2[/SUB], cluster around ~1.1 (cf. 1.0 as a high-temperature limit), indicative of ~30 K as nuclear-spin temperatures. We present our latest results for OPRs of cometary NH[SUB]2[/SUB] and discuss about the real meaning of OPRs of cometary ammonia, in relation to OPRs of water in cometary coma. Chemical processes in the inner coma may play an important role to achieve un-equilibrated OPRs of cometary volatiles in coma.This work was financially supported by MEXT Supported Program for the Strategic Research Foundation at Private Universities, 2014–2018 (No. S1411028) (HK) and by Graint-in-Aid for JSPS Fellows, 15J10864 (YS).References:[1] Mumma & Charnley, 2011, Annu. Rev. Astro. Astrophys. 49, 471.[2] Hama & Watanabe, 2013, Chem. Rev. 113, 8783.[3] Hama et al., 2008, Science 351, 6268.[4] Shinnaka et al., 2011, ApJ 729, 81. [less ▲]

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See detail2003 AZ84: Size, shape, albedo and first detection of topographic features
Dias-Oliveira, Alex; Sicardy, Bruno; Ortiz, Jose-Luis et al

in AAS/Division for Planetary Sciences Meeting Abstracts (2016, October 01)

We analyze two multi-chord stellar occultations by the Trans-Neptunian Object (TNO) 2003 AZ84 observed on February 3, 2012 and November 15, 2014.They provide different elliptical limb fits that are ... [more ▼]

We analyze two multi-chord stellar occultations by the Trans-Neptunian Object (TNO) 2003 AZ84 observed on February 3, 2012 and November 15, 2014.They provide different elliptical limb fits that are consistent to within their respective error bars, but could also suggest a possible precession of the object (assumed here to be a Maclaurin spheroid). The derived equatorial radius and oblateness are R[SUB]e[/SUB] = 393 ± 7 km and ɛ = 0.057 in 2014 and R[SUB]e[/SUB] = 414 ± 13 km and ɛ = 0.165 in 2012, respectively. Those results are consistent with single-chord events observed in January 2011 and December 2013. The figures above provide geometric visual albedos of p[SUB]V(2014)[/SUB] = 0.112 ± 0.008 and p[SUB]V(2012)[/SUB] = 0.114 ± 0.020. Using the Maclaurin assumption, combined with possible rotational periods of 6.67 h and 10.56 h, we estimate density upper limits of 1.89 ± 0.16g/cm[SUP]3[/SUP] and 0.77 ± 0.07g/cm[SUP]3[/SUP] for the two dates, respectively.The 2014 event provides (for the first time during a TNO occultation) a grazing chord with a gradual disappearance of the star behind 2003[SUB]AZ[/SUB]84's limb that lasts for more than 10 seconds. We rule out the possibility of a localized dust concentration as it would imply very high optical depth for that cloud. We favor a local topographic feature (chasm) with minimum width and depth of 22 ± 2.5 km and 7 ± 2.0 km, respectively. Features with similar depths are in fact observed on Pluto's main satellite, Charon, which has a radius of about 605 km, comparable to that of 2003[SUB]AZ[/SUB]84. [less ▲]

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See detailL'astronomie dans le monde - 10/2016
Manfroid, Jean ULiege

Article for general public (2016)

ExoMars – Philae retrouvé – Juno – Proxima du Centaure – Expansion de l’Univers – Les jupiters chaudes de M67 – Titan

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See detailLes observateurs - 10/2016
Manfroid, Jean ULiege; Ponsard, P. Dupont

Article for general public (2016)

À observer en octobre – Balletplanétaire dans le Scorpion - Le télescope Dobson – Nuits des étoiles 2016 - Les Dentelles du Cygne, filtres anti-pollution lumineuse

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See detailL'astronomie dans le monde - 09/2016
Manfroid, Jean ULiege

Article for general public (2016)

Vénus - Phobos et Deimos - Une nouvelle planète naine au-delà de Neptune - Ondes gravitationnelles - L’oxygène de la comète 67P - Averse intergalactique - Méthanol protoplanétaire - TRAPPIST-1 - Les ... [more ▼]

Vénus - Phobos et Deimos - Une nouvelle planète naine au-delà de Neptune - Ondes gravitationnelles - L’oxygène de la comète 67P - Averse intergalactique - Méthanol protoplanétaire - TRAPPIST-1 - Les jupiters chaudes de M67 [less ▲]

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See detailJoyaux cosmiques - 09/2016
Manfroid, Jean ULiege

Article for general public (2016)

Abell S1063 - Jupiter - LHA 120-N55

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See detailThe 19 Feb. 2016 Outburst of Comet 67P/CG: An ESA Rosetta Multi-Instrument Study
Grün, E.; Agarwal, J.; Altobelli, N. et al

in Monthly Notices of the Royal Astronomical Society (2016)

On 19 Feb. 2016 nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ... [more ▼]

On 19 Feb. 2016 nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in-situ gas, dust and plasma instruments, and one dust collector. At 9:40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50% of the neutral gas density at Rosetta to factors >100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors >10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from ˜-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta (34 km from the nucleus): within 15 minutes the Star Tracker camera detected fast particles (˜25 m s[SUP]-1[/SUP]) while 100 μm radius particles were detected by the GIADA dust instrument ˜1 hour later at a speed of ~6 m s[SUP]-1[/SUP]. The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined. [less ▲]

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See detailObservational signatures of past mass-exchange episodes in massive binaries : The cases of LSS 3074 and HD 17505
Raucq, Françoise ULiege; Rauw, Grégor ULiege; Gosset, Eric ULiege et al

Poster (2016, July)

Mass and angular momentum exchanges through Roche Lobe Overflow interactions within close massive binaries are known to play an important role in the subsequent evolution of the components of such systems ... [more ▼]

Mass and angular momentum exchanges through Roche Lobe Overflow interactions within close massive binaries are known to play an important role in the subsequent evolution of the components of such systems, and produce several observational signatures, such as asynchronous rotation and altered chemical compositions, that remain once the stars detach again. We have started to investigate these effects in a sample of massive O-star binaries that are thought to have previously experienced a Case A Roche Lobe Overflow episode. Using phase-resolved spectroscopy, we perform the disentangling of the optical spectra of the two stars. The reconstructed primary and secondary spectra re then analysed with the CMFGEN model atmosphere code to determine stellar parameters such as the effective temperatures, surface gravities and rotational velocities, and to constrain the chemical composition of the components. In this contribution, we present the results of our analyses of LSS 3074 (O5.5I + O6.5-7I, P = 2.1852 days), together with the analyses of its photometric lightcurve and orbital solution. We also present the first results of our analyses of the triple system HD17505 ([O7.5V + O7.5V, P = 8.57 days] + O6.5III). [less ▲]

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See detailL'astronomie dans le monde - 06/2016
Manfroid, Jean ULiege

Article for general public (2016)

Chocs d’amas - Amas de galaxies - Halos sur Pluton - Makémaké - Comète sans queue – Titan – Planètes Kepler - Transit de Mercure - Quatre lasers au-dessus de Paranal – NGC 1332 - Eau sur Mars

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