References of "Manfroid, Jean"
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See detailLower atmosphere and pressure evolution on Pluto from ground-based stellar occultations, 1988-2016
Meza, E.; Sicardy, B.; Assafin, M. et al

in Astronomy and Astrophysics (2019), 625(A42), 21

Context. The tenuous nitrogen (N[SUB]2[/SUB]) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New ... [more ▼]

Context. The tenuous nitrogen (N[SUB]2[/SUB]) 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. <BR /> 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. <BR /> 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). <BR /> 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 N[SUB]2[/SUB] 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. [less ▲]

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See detailDust properties of double-tailed active asteroid (6478) Gault
Moreno, F.; Jehin, Emmanuel ULiege; Licandro, J. et al

in Astronomy and Astrophysics (2019), 624(L14), 11

Context. Asteroid (6478) Gault was discovered to exhibit a comet-like tail in observations from December 2018, becoming a new member of the so-called active asteroid population in the main asteroid belt ... [more ▼]

Context. Asteroid (6478) Gault was discovered to exhibit a comet-like tail in observations from December 2018, becoming a new member of the so-called active asteroid population in the main asteroid belt. <BR /> Aims: We seek to investigate the grain properties of the dust ejected from asteroid (6478) Gault and to give insight into the activity mechanism(s). <BR /> Methods: We use a Monte Carlo dust tail brightness code to retrieve the dates of dust ejection, the physical properties of the grains, and the total dust mass losses during each event. The code takes into account the brightness contribution of the asteroid itself. The model is applied to a large data set of images spanning the period from 2019 January 11 to 2019 March 13. In addition, we carried out both short- and long-term photometric measurements of the asteroid. <BR /> Results: It is shown that, to date, asteroid (6478) Gault has experienced two episodes of impulsive dust ejection, which took place around 2018 November 5 and 2019 January 2. These two episodes released at least 1.4 × 10[SUP]7[/SUP] kg and 1.6 × 10[SUP]6[/SUP] kg of dust, respectively, at escape speeds. The size distribution, consisting of particles in the 1 μm-1 cm radius range, follows a broken power law with bending points near 15 μm and 870 μm. On the other hand, the photometric series indicate a nearly constant magnitude over several 5-7.3 h periods, which is a possible effect of the masking of a rotational light curve by the dust. <BR /> Conclusions: The dust particles forming Gault's tails were released from the asteroid at escape speeds, but the specific ejection mechanism is unclear until photometry of the dust-free asteroid are conducted to assess whether this was related to rotational disruption or to other possible causes. [less ▲]

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See detailHigh resolution optical spectroscopy of the N2-rich comet C/2016 R2 (PanSTARRS)
Opitom, C.; Hutsemekers, Damien ULiege; Jehin, Emmanuel ULiege et al

in Astronomy and Astrophysics (2019), 624

Context. Early observations of comet C/2016 R2 (PanSTARRS) have shown that the composition of this comet is very peculiar. Radio observations have revealed a CO-rich and HCN-poor comet and an optical coma ... [more ▼]

Context. Early observations of comet C/2016 R2 (PanSTARRS) have shown that the composition of this comet is very peculiar. Radio observations have revealed a CO-rich and HCN-poor comet and an optical coma dominated by strong emission bands of CO[SUP]+[/SUP] and, more surprisingly, N[SUB]2[/SUB][SUP]+[/SUP]. <BR /> Aims: The strong detection of N[SUB]2[/SUB][SUP]+[/SUP] in the coma of C/2016 R2 provided an ideal opportunity to measure the [SUP]14[/SUP]N/[SUP]15[/SUP]N isotopic ratio directly from N[SUB]2[/SUB][SUP]+[/SUP] for the first time, and to estimate the N[SUB]2[/SUB]/CO ratio, which is an important diagnostic to constrain formation models of planetesimals, in addition to the more general study of coma composition. <BR /> Methods: We obtained high resolution spectra of the comet in February 2018 when it was at 2.8 au from the Sun. We used the UVES spectrograph of the European Southern Observatory Very Large Telescope, complemented with narrowband images obtained with the TRAPPIST telescopes. <BR /> Results: We detect strong emissions from the N[SUB]2[/SUB][SUP]+[/SUP] and CO[SUP]+[/SUP] ions, but also CO[SUB]2[/SUB][SUP]+[/SUP], emission lines from the CH radical, and much fainter emissions of the CN, C[SUB]2[/SUB], and C[SUB]3[/SUB] radicals that were not detected in previous observations of this comet. We do not detect OH or H[SUB]2[/SUB]O[SUP]+[/SUP], and we derive an upper limit of the H[SUB]2[/SUB]O[SUP]+[/SUP]/CO[SUP]+[/SUP] ratio of 0.4, implying that the comet has a low water abundance. We measure a N[SUB]2[/SUB][SUP]+[/SUP]/CO[SUP]+[/SUP] ratio of 0.06 ± 0.01. The non-detection of NH[SUB]2[/SUB] indicates that most of the nitrogen content of the comet is in N[SUB]2[/SUB]. Together with the high N[SUB]2[/SUB][SUP]+[/SUP]/CO[SUP]+[/SUP] ratio, this could indicate a low formation temperature of the comet or that the comet is a fragment of a large differentiated Kuiper Belt object. The CO[SUB]2[/SUB][SUP]+[/SUP]/CO[SUP]+[/SUP] ratio is 1.1 ± 0.3. We do not detect [SUP]14[/SUP]N[SUP]15[/SUP]N[SUP]+[/SUP] lines and can only put a lower limit on the [SUP]14[/SUP]N/[SUP]15[/SUP]N ratio (measured from N[SUB]2[/SUB][SUP]+[/SUP]) of about 100, which is compatible with measurements of the same isotopic ratio for NH[SUB]2[/SUB] and CN in other comets. Finally, in addition to the [OI] and [CI] forbidden lines, we detect for the first time the forbidden nitrogen lines [NI] doublet at 519.79 and 520.03 nm in the coma of a comet. [less ▲]

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See detailMonitoring of the activity and composition of comets 41P/Tuttle-Giacobini-Kresak and 45P/Honda-Mrkos-Pajdusakova
Moulane, Y.; Jehin, Emmanuel ULiege; Opitom, C. et al

in Astronomy and Astrophysics (2018), 619

We report on photometry and imaging of the Jupiter Family Comets 41P/Tuttle-Giacobini-Kresak and 45P/Honda-Mrkos-Pajdusakova with the TRAPPIST-North telescope. We observed 41P on 34 nights from February ... [more ▼]

We report on photometry and imaging of the Jupiter Family Comets 41P/Tuttle-Giacobini-Kresak and 45P/Honda-Mrkos-Pajdusakova with the TRAPPIST-North telescope. We observed 41P on 34 nights from February 16, 2017 to July 27, 2017 pre- and post-perihelion (r$_h$=1.04 au), while we collected data for comet 45P from February 10 to March 30 after perihelion (r$_h$=0.53 au). We computed the production rates of the daughter species OH, NH, CN, C$_3$ and C$_2$ and we measured the dust proxy, Af$\rho$, for both comets. The peak of water production rate of 41P was (3.46$\pm$0.20)$\times$10$^{27}$ molecules/s on April 3, 2017 when the comet was at 1.05 au from the Sun. We have shown that the activity of 41P is decreasing by about 30% to 40% from one apparition to the next. We measured a mean water production rate for 45P of (1.43$\pm$0.62)$\times$10$^{27}$ molecules/s during a month after perihelion. Our results show that these Jupiter Family Comets had low gas and dust activity and no outburst was detected. Relative abundances, expressed as ratios of production rates and Af$\rho$ parameter with respect to OH and to CN, were compared to those measured in other comets. We found that 41P and 45P have a typical composition in term of carbon bearing species. The study of coma features exhibited by the CN gas species allowed the measurement of the rotation period of 41P, showing a surprisingly large increase of the rotation period from (30$\pm$5) hrs at the end of March to (50$\pm$10) hrs at the end of April, 2017 in agreement with recent observations by other teams. [less ▲]

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See detailA high resolution spetrum of comet C/2016 R2 (PanSTARRS) with the ESO VLT
Jehin, Emmanuel ULiege; Opitom, Cyrielle; Hutsemekers, Damien ULiege et al

in Bulletin of the American Astronomical Society (2018, October 01), 50

The returning long period comet C/2016 R2 (PanSTARRS) was discovered on September 7, 2016 at 6.3 au from the Sun. While it was already showing a 20" coma at this large distance (Weryk and Wainscoat 2016 ... [more ▼]

The returning long period comet C/2016 R2 (PanSTARRS) was discovered on September 7, 2016 at 6.3 au from the Sun. While it was already showing a 20" coma at this large distance (Weryk and Wainscoat 2016), it is only in December 2017 that it was found that this comet had a very unusual composition. From radio observations the comet appeared to be very rich in CO and very poor in HCN (Wierzchos and Womack 2018) and its optical spectrum was dominated by CO[SUP]+[/SUP] and more surprisingly N[SUB]2[/SUB][SUP]+[/SUP] emission bands (Cochran and McKay 2018), while most of the emission bands usually detected in the optical spectrum of comets were not detected. In order to investigate in detail its coma in the optical, we obtained a total of 6 hours of Director Discretionary Time on C/2016 R2 with UVES, the high resolution optical spectrograph of the ESO Very Large Telescope, between February 11 and 16, 2018. We used two different settings to optimally cover the whole optical spectrum (326-1060 nm) with a resolving power of 80.000. We report on those observations. We detect strong emissions of the ions CO[SUP]+[/SUP] and N[SUB]2[/SUB][SUP]+[/SUP], and also several CO[SUB]2[/SUB][SUP]+ [/SUP]bands, but no H[SUB]2[/SUB]O[SUP]+[/SUP] . We detect emission lines of the radicals CN, C[SUB]2[/SUB] and C[SUB]3[/SUB] but they are very weak. We computed from these spectra the N[SUB]2[/SUB][SUP]+[/SUP] / CO[SUP]+[/SUP] / CO[SUB]2[/SUB][SUP]+[/SUP] ratios in the coma of the comet which put some constraints on the comet formation models, and compared those values to other comets. The forbidden oxygen [OI] lines are detected, allowing to measure the ratio between the green line and the red doublet which provides a way to determine the abundance of CO and CO[SUB]2[/SUB] relative to H[SUB]2[/SUB]O. For the first time we report the detection of the nitrogen [NI] forbidden doublet at 5197.9 and 5200.2 Å in the coma of a comet, confirming the high abundance of nitrogen in this comet. Interestingly we also detect a line at 9850 Å which could be one of the carbon [CI] forbidden lines but we do not detect the other line of the doublet at 9823 Å. Because of the strong N[SUB]2[/SUB][SUP]+[/SUP] emissions, it was also a unique opportunity to measure the [SUP]14[/SUP]N/[SUP]15[/SUP]N isotopic ratio directly in N[SUB]2[/SUB], the main nitrogen reservoir in the solar nebula. [less ▲]

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See detailOn the dust properties and dynamical evolution of the near- Earth Jupiter family comet 41P/Tuttle-Giacobini-Kresak
Pozuelos Romero, Francisco José ULiege; Jehin, Emmanuel ULiege; Moulane, Youssef et al

Poster (2018, September 01)

We present a study of the evolution of the dust environment of the near-Earth Jupiter family comet 41P/Tuttle-Giacobini-Kresak, based on observational data obtained using TRAPPIST telescopes from January ... [more ▼]

We present a study of the evolution of the dust environment of the near-Earth Jupiter family comet 41P/Tuttle-Giacobini-Kresak, based on observational data obtained using TRAPPIST telescopes from January to July, 2017. In addition, we performed numerical simulations to constrain its origin and dynamical nature. Along this work we compared our results with those obtained for 67P/Churyumov-Gerasimenko. These results have been recently accepted for publication in Astronomy & Astrophysics. [less ▲]

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See detailTRAPPIST monitoring of the activity and composition of the small near-Earth Jupiter Family Comets : 41P and 252P
Moulane, Youssef; Jehin, Emmanuel ULiege; José Pozuelos, Francisco et al

Poster (2018, September 01)

We monitored 41P and 252P on both sides of perihelion with the TRAPPIST telescopes. The gas species production rates were computed as well as the Afrho parameter for both comets. Our results have shown ... [more ▼]

We monitored 41P and 252P on both sides of perihelion with the TRAPPIST telescopes. The gas species production rates were computed as well as the Afrho parameter for both comets. Our results have shown that the two JFCs have a typical composition according to the Q(C2)/Q(CN) and Q(C3)/Q(CN) ratios but have a low gas and dust activity compared to other JFCs. We found that the activity of 41P is decreasing by about 30% to 40% from one apparition to the next. We confirmed rotation period derived from coma features slowed down by 20 hours in 2 months. 252P has shown an increase in production rates and dust production after perihelion which is believed to be associated with thermal processing of the nucleus surface. [less ▲]

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See detailHigh resolution spectroscopy of the unusual comet C/2016 R2 (PanSTARRS)
Opitom, Cyrielle; Hutsemekers, Damien ULiege; Rousselot, Philippe et al

in EPSC Abstracts (2018, September 01), 12

We report on high spectral resolution observations of the peculiar comet C/2016 R2 (Pan-STARRS). This comet was found to have a highly unusual composition, with a very high abundance of CO, and is only ... [more ▼]

We report on high spectral resolution observations of the peculiar comet C/2016 R2 (Pan-STARRS). This comet was found to have a highly unusual composition, with a very high abundance of CO, and is only the third comet in which the N2+ ion is clearly detected. Our observations allowed us to measure the N2+/CO+/CO2+ ratios. Among other things, we also put an upper limit to the 14N/15N isotopic ratio, measured for the first time directly from N2+, and detected the [NI] lines for the first time in a comet. [less ▲]

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See detailSearch for water outgassing of (1) Ceres near its perihelion
Rousselot, Philippe; Opitom, Cyrielle; Jehin, Emmanuel ULiege et al

in EPSC Abstracts (2018, September 01), 12

(1) Ceres is the largest body in the main asteroid belt and one of the most intriguing object since the discovery of water outgassing in the infrared by the Herschel space observatory in 2014. Ceres is ... [more ▼]

(1) Ceres is the largest body in the main asteroid belt and one of the most intriguing object since the discovery of water outgassing in the infrared by the Herschel space observatory in 2014. Ceres is the current target of NASA's Dawn spacecraft. Recently, the possible influence of the local flux of solar energetic particles (SEP) on the production of a cerean exosphere and water vapor has been suggested. On the other hand the Herschel, IUE and ground-based observations seem to show a correlation between water vapor emission and Ceres heliocentric distance. We used the opportunity of both the perihelion passage of (1) Ceres in 2018 and the presence of Dawn in its vicinity (for measuring the SEP flux in real time) to check the influence of heliocentric distance on water outgassing. We searched for OH emission lines from the limb of Ceres in the near- UV. Despite a sensitivity level similar to the Herschel observations we did not detect any water outgassing. [less ▲]

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See detailThe triple system HD 150136: From periastron passage to actual masses
Mahy, Laurent ULiege; Gosset, Eric ULiege; Manfroid, Jean ULiege et al

in Astronomy and Astrophysics (2018), 616(A), 75

Context. The triple system HD 150136 is composed of an O3 V((f[SUP]*[/SUP]))-O3.5 V((f[SUP]+[/SUP])) primary, of an O5.5-6 V((f)) secondary, and of a more distant O6.5-7 V((f)) tertiary. The latter ... [more ▼]

Context. The triple system HD 150136 is composed of an O3 V((f[SUP]*[/SUP]))-O3.5 V((f[SUP]+[/SUP])) primary, of an O5.5-6 V((f)) secondary, and of a more distant O6.5-7 V((f)) tertiary. The latter component went through periastron in 2015-2016, an event that will not occur again within the next eight years. <BR /> Aims: We aim to analyse the tertiary periastron passage to determine the orbital properties of the outer system, to constrain its inclination and its eccentricity, and to determine the actual masses of the three components of the system. <BR /> Methods: We conducted an intensive spectroscopic monitoring of the periastron passage of the tertiary component and combined the outcoming data with new interferometric measurements. This allows us to derive the orbital solution of the outer orbit in three-dimensional space. We also obtained the light curve of the system to further constrain the inclination of the inner binary. <BR /> Results: We determine an orbital period of 8.61 ± 0.02 years, an eccentricity of 0.682 ± 0.002, and an inclination of 106.18 ± 0.14° for the outer orbit. The actual masses of the inner system and of the tertiary object are 72.32[SUB]-8.49[/SUB][SUP]+8.45[/SUP] M[SUB]☉[/SUB] and 15.54[SUB]-4.97[/SUB][SUP]+4.96[/SUP] M[SUB]☉[/SUB], respectively. From the mass of the inner system and accounting for the known mass ratio between the primary and the secondary, we determine actual masses of 42.81 M[SUB]☉[/SUB] and 29.51 M[SUB]☉[/SUB] for the primary and the secondary components, respectively. We infer, from the different mass ratios and the inclination of the outer orbit, an inclination of 62.4° for the inner system. This value is confirmed by photometry. Grazing eclipses and ellipsoidal variations are detected in the light curve of HD 150136. We also compute the distance of the system to 1.096 ± 0.274 kpc. <BR /> Conclusions: By combining spectroscopy, interferometry, and photometry, HD 150136 offers us a unique chance to compare theory and observations. The masses estimated through our analysis are smaller than those constrained by evolutionary models. The formation of this triple system suggests similar ages for the three components within the errorbars. Finally, we show that Lidov-Kozai cycles have no effect on the evolution of the inner binary, which suggests that the latter will experience mass transfer leading to a merger of the two stars. Based on observations collected at the European Southern Observatory (Paranal and La Silla, Chile).The journal of observations and the radial velocity data are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (<A href="http://cdsarc.u-strasbg.fr">http://130.79.128.5</A>) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/616/A75">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/616/A75</A> [less ▲]

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See detailDust modelling and dynamical study of comet 41P/Tuttle-Giacobini-Kresak during 2017 perihelion passage
Pozuelos Romero, Francisco José ULiege; Jehin, Emmanuel ULiege; Moulane, Youssef ULiege et al

in Astronomy and Astrophysics (2018), 615

Context. Thanks to the Rosetta mission, our understanding of comets has greatly improved. A very good opportunity to apply this knowledge appeared in early 2017 with the appearance of the Jupiter family ... [more ▼]

Context. Thanks to the Rosetta mission, our understanding of comets has greatly improved. A very good opportunity to apply this knowledge appeared in early 2017 with the appearance of the Jupiter family comet 41P/Tuttle-Giacobini-Kresak. The comet was only 0.15 au from the Earth as it passed through perihelion on April 12, 2017. We performed an observational campaign with the TRAPPIST telescopes that covered almost the entire period of time when the comet was active. Aims: In this work we present a comprehensive study of the evolution of the dust environment of 41P based on observational data from January to July, 2017. In addition, we performed numerical simulations to constrain its origin and dynamical nature. Methods: To model the observational data set we used a Monte Carlo dust tail model, which allowed us to derive the dust parameters that best describe its dust environment as a function of heliocentric distance: its dust production rate, the size distribution and ejection velocities of the dust particles, and its emission pattern. In order to study its dynamical evolution, we completed several experiments to evaluate the degree of stability of its orbit, its life time in its current region close to Earth, and its future behaviour. Results: From the dust analysis, we found that comet 41P is a dust-poor comet compared to other comets of the same family, with a complex emission pattern that shifted from full isotropic to anisotropic ejection sometime during February 24-March 14 in 2017, and then from anisotropic to full isotropic again between June 7 and 28. During the anisotropic period, the emission was controlled by two strongly active areas, where one was located in the southern and one in the northern hemisphere of the nucleus. The total dust mass loss is estimated to be 7.5 × 108 kg. From the dynamical simulations we estimate that 3600 yr is the period of time during which 41P will remain in a similar orbit. Taking into account the estimated mass loss per orbit, after 3600 yr, the nucleus may lose about 30% of its mass. However, based on its observed dust-to-water mass ratio and its propensity to outbursts, the lifetime of this comet could be much shorter. [less ▲]

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See detailIsotopic ratios in outbursting comet C/2015 ER61
Yang, Bin; Hutsemekers, Damien ULiege; Shinnaka, Yoshiharu et al

in Astronomy and Astrophysics (2018), 609

Isotopic ratios in comets are critical to understanding the origin of cometary material and the physical and chemical conditions in the early solar nebula. Comet C/2015 ER61 (PANSTARRS) underwent an ... [more ▼]

Isotopic ratios in comets are critical to understanding the origin of cometary material and the physical and chemical conditions in the early solar nebula. Comet C/2015 ER61 (PANSTARRS) underwent an outburst with a total brightness increase of 2 magnitudes on the night of 2017 April 4. The sharp increase in brightness offered a rare opportunity to measure the isotopic ratios of the light elements in the coma of this comet. We obtained two high-resolution spectra of C/2015 ER61 with UVES/VLT on the nights of 2017 April 13 and 17. At the time of our observations, the comet was fading gradually following the outburst. We measured the nitrogen and carbon isotopic ratios from the CN violet (0, 0) band and found that [SUP]12[/SUP]C/[SUP]13[/SUP]C = 100 ± 15, [SUP]14[/SUP]N/[SUP]15[/SUP]N = 130 ± 15. In addition, we determined the [SUP]14[/SUP]N/[SUP]15[/SUP]N ratio from four pairs of NH[SUB]2[/SUB] isotopolog lines and measured [SUP]14[/SUP]N/[SUP]15[/SUP]N = 140 ± 28. The measured isotopic ratios of C/2015 ER61 do not deviate significantly from those of other comets. [less ▲]

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See detailL'astronomie dans le monde - 01/2018
Manfroid, Jean ULiege

Article for general public (2018)

C/2012 K1 (PANSTARRS); Ross 128; A/2017 U1 PANSTARRS -1I/2017 U1(suite); Comète 45P/Honda-Mrkos-Pajdušáková; Oxydes carboniques cométaires; RSL; Énergie et matière noires ?; Pollution lumineuse; Échos ... [more ▼]

C/2012 K1 (PANSTARRS); Ross 128; A/2017 U1 PANSTARRS -1I/2017 U1(suite); Comète 45P/Honda-Mrkos-Pajdušáková; Oxydes carboniques cométaires; RSL; Énergie et matière noires ?; Pollution lumineuse; Échos lumineux; Sondage spectroscopique profond; Petit Nuage de Magellan; Une fusion de plus; Minimums solaires [less ▲]

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See detailStellar parameters for TRAPPIST-1
Van Grootel, Valérie ULiege; Silva Fernandes, Catarina ULiege; Gillon, Michaël ULiege et al

in Astrophysical Journal (2018), 853

TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability and internal ... [more ▼]

TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability and internal compositions is possible with current and next generation telescopes. Accurate modeling of the star is essential to achieve this goal. We aim to obtain updated stellar parameters for TRAPPIST- 1 based on new measurements and evolutionary models, compared to those used in discovery studies. We present a new measurement for the parallax of TRAPPIST-1, 82.4 $\pm$ 0.8 mas, based on 188 epochs of observations with the TRAPPIST and Liverpool Telescopes from 2013 to 2016. This revised parallax yields an updated luminosity of $L_*=(5.22\pm0.19)\times 10^{-4} L_{\odot}$, very close to the previous estimate but almost twice more precise. We next present an updated estimate for TRAPPIST-1 stellar mass, based on two approaches: mass from stellar evolution modeling, and empirical mass derived from dynamical masses of equivalently classified ultracool dwarfs in astrometric binaries. We combine them through a Monte-Carlo approach to derive a semi-empirical estimate for the mass of TRAPPIST-1. We also derive estimate for the radius by combining this mass with stellar density inferred from transits, as well as estimate for the effective temperature from our revised luminosity and radius. Our final results are $M_*=0.089 \pm 0.006 M_{\odot}$, $R_* = 0.121 \pm 0.003 R_{\odot}$, and $T_{\rm eff} =$ 2516 $\pm$ 41 K. Considering the degree to which TRAPPIST-1 system will be scrutinized in coming years, these revised and more precise stellar parameters should be considered when assessing the properties of TRAPPIST-1 planets. [less ▲]

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See detailÊta Carinae
Manfroid, Jean ULiege

Article for general public (2018)

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See detailLes observateurs - 02/2018
Manfroid, Jean ULiege; Ponsard, P.; Tajer, P.

Article for general public (2018)

Les Géminides; Un nouvel observateur à la SAL

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See detailGaia : le ciel en 3D - 06/2018
Manfroid, Jean ULiege

Article for general public (2018)

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See detailPhaéton - 02/2018
Manfroid, Jean ULiege

Article for general public (2018)

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See detailL'astronomie dans le monde - 12/2018
Manfroid, Jean ULiege

Article for general public (2018)

Tempêtes de poussière sur Titan– Le trou noir de la Voie lactée – Une molécule radioactive dans CK Vulpeculae – Exolune – Europe – Trous noirs supermassifs doubles – Nuage martien – Ondes sur Jupiter

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See detailJoyaux cosmiques - 12/2018
Manfroid, Jean ULiege

Article for general public (2018)

M8, la nébuleuse de la Lagune – Barge de Jupiter

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