Publications of Youssef Moulane
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See detailLightcurve Based Determination of 10 Hygiea'S Rotational Period With Trappist-North and -South
Ferrais, Marin ULiege; Jehin, Emmanuel ULiege; Vernazza, Pierre et al

in Minor Planet Bulletin (2021), 48

A densely-sampled lightcurve of the large main-belt asteroid 10 Hygiea was obtained with the TRAPPISTSouth (TS) and TRAPPIST-North (TN) telescopes in 2018 September and October. We found its synodic ... [more ▼]

A densely-sampled lightcurve of the large main-belt asteroid 10 Hygiea was obtained with the TRAPPISTSouth (TS) and TRAPPIST-North (TN) telescopes in 2018 September and October. We found its synodic rotation period and amplitude to be 13.8224 ± 0.0005 h and 0.27 mag. The data have been submitted to the ALCDEF database. [less ▲]

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See detail398P/Boattini a new JFC carbon-chain poor comet
Jehin, Emmanuel ULiege; Moulane, Youssef ULiege; Manfroid, Jean ULiege et al

in The Astronomer's Telegram (2020), 14251

E. Jehin, Y. Moulane, J. Manfroid, F. Pozuelos, M. Ferrais, D. Hutsemekers (STAR Institute, University of Liege, Belgium) report that they obtained with TRAPPIST-North (code=Z53, at Oukaimeden Observatory ... [more ▼]

E. Jehin, Y. Moulane, J. Manfroid, F. Pozuelos, M. Ferrais, D. Hutsemekers (STAR Institute, University of Liege, Belgium) report that they obtained with TRAPPIST-North (code=Z53, at Oukaimeden Observatory, Morocco) 0.6-m robotic telescope, three sets of observations of the recently recovered comet 398P/Boattini (= 2009 Q4 = 2020 P2, CBET 4829) on November 10, 15 and 20 UT under photometric conditions using HB cometary narrowband filters (Farnham et al. 2000). [less ▲]

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See detailTRAPPIST comet production rates: 88/Howell, C/2020 M3 (ATLAS), C/2020 S3 (Erasmus), 156P/Russell-LINEAR
Jehin, Emmanuel ULiege; Moulane, Youssef ULiege; Manfroid, Jean ULiege et al

in The Astronomer's Telegram (2020), 14174

E. Jehin, Y. Moulane, J. Manfroid, F. Pozuelos, M. Ferrais, D. Hutsemekers (STAR Institute, University of Liege) report that they obtained from TRAPPIST-South (code=I40, Chile) and TRAPPIST-North (code ... [more ▼]

E. Jehin, Y. Moulane, J. Manfroid, F. Pozuelos, M. Ferrais, D. Hutsemekers (STAR Institute, University of Liege) report that they obtained from TRAPPIST-South (code=I40, Chile) and TRAPPIST-North (code=Z53, Morocco) 0.6-m robotic telescopes (Jehin el al. 2011) observations using HB narrowband filters (Farnham et al. 2000) for the following comets and computed preliminary production rates at 10.000 km using a Haser Model (Vp=Vd=1km/s) (Haser 1957). [less ▲]

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See detailTRAPPIST comet production rates: 88/Howell, C/2020 M3 (ATLAS), C/2020 S3 (Erasmus), 156P/Russell-LINEAR
Jehin, Emmanuel ULiege; Moulane, Youssef ULiege; Manfroid, Jean ULiege et al

in The Astronomer's Telegram (2020), 14101

E. Jehin, Y. Moulane, J. Manfroid, F. Pozuelos, D. Hutsemekers (STAR Institute, University of Liege) report that they obtained from TRAPPIST-South (I40, Chile) and TRAPPIST-North (Z53, Morocco) 0.6-m ... [more ▼]

E. Jehin, Y. Moulane, J. Manfroid, F. Pozuelos, D. Hutsemekers (STAR Institute, University of Liege) report that they obtained from TRAPPIST-South (I40, Chile) and TRAPPIST-North (Z53, Morocco) 0.6-m robotic telescopes (Jehin el al. 2011) observations using HB narrowband filters (Farnham et al. 2000) for the following comets and computed preliminary production rates at 10.000 km using a Haser Model (Vp=Vd=1km/s) (Haser 1957). [less ▲]

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See detailOn Water Ice in Cometary Outbursts
Kelley, M.; Protopapa, S.; Moulane, Youssef ULiege et al

in Bulletin of the American Astronomical Society (2020, October 01), 52

Cometary outbursts are brief, but potentially strong, mass-loss events, likely caused by a wide range of phenomena [1]. Using near-infrared (near-IR) spectroscopy, water ice grains have been observed in ... [more ▼]

Cometary outbursts are brief, but potentially strong, mass-loss events, likely caused by a wide range of phenomena [1]. Using near-infrared (near-IR) spectroscopy, water ice grains have been observed in the ejecta of some cometary outbursts. These detections present us with opportunities to study the properties of a cometary ice, and potentially infer the properties of the nucleus at the site of the event. <P />We present a detailed analysis of a large outburst (∆m~3 mag) of comet 243P/NEAT that occurred in December 2018, at 2.55 au from the Sun. Our study combines photometry, imaging, and spectroscopy with dynamical and thermophysical models of dust and ice grains. Overall, the outburst ejected ~10[SUP]8[/SUP] kg of dust. We find no photometric or spectroscopic evidence for water ice in our data, which includes near-IR spectroscopy (1─2.5 μm) taken 4 days after the outburst. Nevertheless, this does not necessarily imply that water ice was not ejected by the outburst. Specifically, we consider the possibility that the ejecta from 243P had ice with the same properties as comet C/2013 US[SUB]10[/SUB] (Catalina): micrometer-sized grains mixed with a small fraction of low-albedo dust, ~0.5% by volume [2]. These physical properties can account for our 243P/NEAT observations on thermophysical and dynamical grounds, i.e., the icy grains are depleted in our spectroscopic slit due to ice sublimation and their expansion speed. <P />The lack of water ice absorption features in our near-IR spectrum is in stark contrast to the outbursts of comets 17P/Holmes and P/2010 H2 (Vales), which had the signatures of water ice 7 and 6 days post-outburst, respectively [3,4], despite occurring at similar heliocentric distances and spanning a wide range of ejected masses (10[SUP]8[/SUP] kg for Vales, 10[SUP]11[/SUP] kg for Holmes) [5]. We consider the dynamical and thermophysical properties of water ice grains in each event, and discuss three possibilities for the differences: (1) that the site of the 243P outburst has a low abundance of water ice caused by surface processing or natal heritage; (2) that ice observed at Holmes and/or Vales was not from the original outburst, but instead produced after the event; and/or, (3) that a diversity of water ice properties exists in the comet population. We conclude that further studies of cometary outbursts that combine dynamical, spectroscopic, and thermophysical considerations will help advance our general understanding of water ice in comets. <P />1: Hughes 1990, QJRAS, 31, 69 ; 2: Protopapa et al. 2018, ApJL, 862, 16 ; 3: Yang et al. 2009, AJ 137, 4538 ; 4: Yang and Sarid 2010, DPS 42, 5.09 ; 5: Ishiguro et al. 2016, AJ 152, 168 [less ▲]

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See detailA dense monitoring of 2I/Borisov activity with TRAPPIST telescopes
Jehin, Emmanuel ULiege; Moulane, Youssef ULiege; Pozuelos Romero, Francisco José ULiege et al

Conference (2020, September 01)

We report on the regular observation with broad band and cometary narrow band filters of the first interstellar active comet, 2I/Borisov, with both TRAPPIST-South and -North telescopes (TS and TN) [1]. We ... [more ▼]

We report on the regular observation with broad band and cometary narrow band filters of the first interstellar active comet, 2I/Borisov, with both TRAPPIST-South and -North telescopes (TS and TN) [1]. We followed 2I activity since its discovery on September 11, 2019 (rh=2.8 au inbound) until the beginning of March 2020 when it was 2.9 au outbound and TS operations had to stop because of Covid-19 and la Silla Observatory closure. The comet activity reached a maximum on November 29, 2019 (rh=2.01au), 10 days before perihelion with an apparent magnitude of 16.50±0.04 measured within an aperture radius of 5 arcsec in R filter, an A(0)fp(R) dust proxy = 135±7 cm and a Q(CN)=(4.5±0.7) 1024 molecules/s (using a Haser model and vp=vd=1km/s [2]). Unlike the first interstellar object, 1I/Oumuamua, discovered in 2017 [3,4], 2I was showing an extended coma surrounding its nucleus and a short tail. We first detected CN in 2I with TN on October 18 when the comet was 2.65 au from the Sun while we never detected C2. We were able to follow the CN activity of 2I for more than 3 months.Figure 1: Light curve (R mag) and A(0)fp dust proxy of 2I/Borisov as a function of days to perihelion. The A(0)fp values are computed at 10 000 km from the nucleus and normalized to phase angle of 0°.References:[1] Jehin, E., Gillon, M., Queloz, D., et al. 2011, The Messenger, 145, 2[2] Haser, 1957, Bulletin de l'Académie Royale de Belgique, vol. 43, p. 740-750[3] Meech, K. J., Weryk, R., Micheli, M., et al. 2017, Nature, 552, 378[4] Micheli, M., Farnocchia, D., Meech, K. J., et al. 2018, Nature, 559, 223 [less ▲]

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See detailNarrow-band photometry of Long Period Comets with TRAPPIST telescopes in 2019-2020
Moulane, Youssef ULiege; Jehin, Emmanuel ULiege; José Pozuelos, Francisco et al

Conference (2020, September 01)

Long Period Comets (LPCs) have orbital periods longer than 200 years, perturbed from their resting place in the Oort cloud. Such gravitational influences may send these icy bodies on a path towards the ... [more ▼]

Long Period Comets (LPCs) have orbital periods longer than 200 years, perturbed from their resting place in the Oort cloud. Such gravitational influences may send these icy bodies on a path towards the center of the Solar system in highly elliptical orbits. In this work, we present the activity and composition evolution of several LPCs observed with both TRAPPIST telescopes (TS and TN) during the period of 2019-2020. These comets include: C/2017 T2 (PANSTARRS), C/2018 Y1 (Iwamoto), C/2018 W2 (Africano), and disintegrated comet C/2019 Y4 (ATLAS). We monitored the OH, NH, CN, C2 and C3 production rates evolution and their chemical mixing ratios with respect to their distances to the Sun as well as the dust production rate proxy (A(0)fp) during the journey of these comets into the inner Solar system.C/2017 T2 (PANSTARRS) is a very bright comet which was discovered on October 2, 2017 when it was 9.20 au from the Sun. We started observing this comet with TS at the beginning of August 2019 when it was at 3.70 au. The comet made the closest approach to the Earth on December 28, 2019 at a distance of 1.52 au and it passed the perihelion on May 4, 2020 at 1.61 au. The water production rate of the comet reached a maximum of (4,27±0,12)1028 molecules/s and its dust production rate (A(0)fp(RC)) also reached the peak of 5110±25 cm on January 26, 2020, when the comet was at 2.08 au from the Sun (-100 days pre-perihelion). At the time of writing, we still monitoring the activity of the comet with TN at heliocentric distance of 1.70 au. Our observations show that C/2017 T2 is a normal LPC.C/2018 Y1 (Iwamoto) is a nearly parabolic comet with a retrograde orbit discovered on December 18, 2018 by Japanese amateur astronomer Masayuki Iwamoto. We monitored the activity and composition of Iwamoto with both TN and TS telescopes from January to March 2019. The comet reached its maximum activity on January 29, 2019 when it was at 1.29 au from the Sun (-8 days pre-perihelion) with Q(H2O)=(1,68±0,05)1028 molecules/s and A(0)fp(RC)= 92±5 cm. These measurements show that it was a dust-poor comet compared to the typical LPCs.C/2018 W2 (Africano) was discovered on November 27, 2018 at Mount Lemmon Survey with a visual magnitude of 20. The comet reached its perihelion on September 6, 2019 when it was at 1.45 au from the Sun. We monitored the comet from July 2019 (rh=1.71 au) to January 2020 (rh=2.18 au) with both TN and TS telescopes. The comet reached its maximum activity on September 21, 15 days post-perihelion (rh=1.47 au) with Q(H2O)=(0,40±0,03)1028 molecules/s.C/2019 Y4 (ATLAS) is a comet with a nearly parabolic orbit discovered on December 18, 2019 by the ATLAS survey. We started to follow its activity and composition with broad- and narrow-band filters with the TN telescope on February 22, 2019 when it was at 1.32 au from the Sun until May 3, 2020 when the comet was at a heliocentric distance of 0.90 au inbound. The comet activity reached a maximum on March 22 (rh=1.65 au) 70 days before perihelion. At that time, the water-production rate reached (1,53±0,04)1028 molecules/s and the A(0)fp reached (1096±14) cm in the red filter. After that, the comet began to fade and disintegrated into several fragments. [less ▲]

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See detailMonitoring of the optical spectrum of comet 2I/Borisov at the VLT
Jehin, Emmanuel ULiege; Bin, Yang; Hainaut, Olivier et al

Conference (2020, September 01)

2I/Borisov is the first active interstellar comet observed in the Solar Sytem, allowing for the first time to sample the composition of a planetary building block from an extrasolar system. We report on ... [more ▼]

2I/Borisov is the first active interstellar comet observed in the Solar Sytem, allowing for the first time to sample the composition of a planetary building block from an extrasolar system. We report on the monitoring of 2I with the FORS low resolution spectrograph of the ESO VLT at Paranal during four months, from November 19, 2019 to March 20, 2020. We collected a dozen spectra at 8 different epochs allowing to follow the evolution of the comet activity and composition around perihelion. We also observed with the same instrumental setup an Oort Cloud comet, C/2019 U6 (Lemmon), at about the same heliocentric and geocentric distance than 2I/Borisov at perihelion (rh=Delta=2 au) and with similar AfRho value and Q(CN) in order to use it as a reference for the Solar System. The usual species are detected in the optical spectrum of 2I (CN, C3, C2, and NH2) and their production rates and abundance ratios are computed. The dust production rate and colors are also derived, compared to C/2019 U6 and other comets of the Solar System, and their evolutions are followed with the heliocentric distance. Fig1. Comparison of the optical spectra of the interstellar comet 2I/Borisov at perihelion (rh=Delta=2,0 au) and the Oort Could comet C/2019 U6 (Lemmon) observed with FORS at the ESO VLT (Paranal Observatory). C/2019/U6 was chosen for comparison as a Solar System comet with a typical composition. It was also at the about the same distances to the Sun and Earth, and it had about the same dust and CN production rates as 2I/Borisov as measured by the TRAPPIST-South telescope. [less ▲]

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See detailFollow-up of the activity and composition of the interstellar comet 2I/Borisov with MUSE
Opitom, Cyrielle; Bannister, Michele; Rousselot, Philippe et al

Conference (2020, September 01)

The interstellar comet 2I/Borisov was discovered on August 20, 2019. It is only the second interstellar object to be observed crossing our Solar System, and the first one for which outgassing was detected ... [more ▼]

The interstellar comet 2I/Borisov was discovered on August 20, 2019. It is only the second interstellar object to be observed crossing our Solar System, and the first one for which outgassing was detected directly [1]. Early observations indicated that 2I/Borisov is depleted in C2, similarly to about 30% of Solar System comets [2,3]. Preliminary observations with the MUSE IFU performed in November 2019 confirmed that 2I is depleted in C2 but also showed it is rich in NH2 [4]. We present here results from the full observing campaign performed with the MUSE instrument.MUSE is a multi-unit integral field spectrograph mounted on the UT4 telescope of the VLT [5]. The instrument covers the wavelength range from 480 to 930 nm with a resolving power of about 3000. It has a large field of view of 1"x1" and a spatial resolution of 0.2", which makes it an ideal instrument to study extended sources. We observed 2I with MUSE on 16 different dates between November 14, 2019 and March 19, 2020. The observations started about one month before the perihelion passage and continued until the comet reached 3 au post-perihelion. This data sets constitutes a great opportunity to study the activity and coma composition of 2I over several months.Our observations allow us to detect emission bands from C2, NH2, and CN. Using a Haser model [6] we derive production rates for those 3 species and follow their evolution. We also study the evolution of the ratio between those production rates, to monitor how the composition of 2I coma changes as a function of time and distance from the Sun.References:[1] Fitzsimmons et al., 2019, The Astrophysical Journal Letters, Volume 885, Issue 1, article id. L9, 6 pp.[2] Opitom et al., 2019, Astronomy & Astrophysics, Volume 631, id.L8, 5 pp.; [3] Lin et al., 2019, The Astrophysical Journal Letters, Volume 889, Issue 2, id.L30;[4] Bannister et al, 2020, submitted to ApJ Letters; [5] Bacon et al, 2010, Proceedings of the SPIE, Volume 7735, id. 773508; [6] Haser, 1957,Bulletin de la Classe des Sciences de l'Académie Royale de Belgique, vol. 43, p. 740-750 [less ▲]

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See detailPhotometry and high-resolution spectroscopy of comet 21P/Giacobini-Zinner during its 2018 apparition
Moulane, Youssef ULiege; Jehin, Emmanuel ULiege; Rousselot, P. et al

in Astronomy and Astrophysics (2020), 640(A54), 14

We report on photometry and high-resolution spectroscopy of the chemically peculiar Jupiter-family comet (hereafter JFC) 21P/Giacobini-Zinner. Comet 21P is a well-known member of the carbon-chain-depleted ... [more ▼]

We report on photometry and high-resolution spectroscopy of the chemically peculiar Jupiter-family comet (hereafter JFC) 21P/Giacobini-Zinner. Comet 21P is a well-known member of the carbon-chain-depleted family, but also displays a depletion of amines. We continuously monitored the comet over more than seven months with the two TRAPPIST telescopes (TN and TS), covering a wide heliocentric distance range from 1.60 au inbound to 2.10 au outbound with a perihelion at 1.01 au on September 10, 2018. We computed and followed the evolution of the dust- (represented by Afρ) and gas-production rates of the daughter species OH, NH, CN, C3, and C2 and their relative abundances to OH and to CN over the cometary orbit. We compared them to those measured in the previous apparitions. The activity of the comet and its water production rate reached a maximum of (3.72 ± 0.07) × 1028 mol s-1 on August 17, 2018 (rh = 1.07 au), 24 days before perihelion. The peak value of A(0)fρ was reached on the same date (1646 ± 13) cm in the red filter. Using a sublimation model for the nucleus, we constrained the active surface of the nucleus using the slow-rotator model. The abundance ratios of the various species are remarkably constant over a wide range of heliocentric distances before and after perihelion, showing a high level of homogeneity of the ices in the surface of the nucleus. The behaviour and level of the activity of the comet is also remarkably similar over the last five orbits. In the coma dust colour, 21P shows reflective gradients similar to JFCs. We obtained a high-resolution spectrum of 21P with UVES at ESO Very Large Telescope one week after perihelion. Using the CN B-X (0, 0) violet band, we measured 12C/13C and 14N/15N isotopic ratios of 100 ± 10 and 145 ± 10, respectively, both in very good agreement with the ratios commonly found in comets. We measured an ortho-para abundance ratio of NH3 of 1.16 ± 0.02, corresponding to a nuclear spin temperature of Tspin = 27 ± 1 K, which is similar to other comets. While the abundance ratios in the gaseous coma reveal a peculiar composition, the isotopic and ortho-to-para ratios appear entirely normal. We performed a dynamical simulation of 21P and found that it is likely a young member of the JFC population. We favour a pristine composition scenario to explain the chemical peculiarities of this comet. [less ▲]

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See detailTrappist-North and -South Combined Lightcurves of Near-Earth Asteroid 3122 Florence
Ferrais, Marin ULiege; Jehin, Emmanuel ULiege; Moulane, Youssef ULiege et al

in Minor Planet Bulletin (2020), 47

A long lightcurve of the near-Earth asteroid 3122 Florence was obtained by combining observations from the TRAPPIST-South (TS) and TRAPPIST- North (TN) telescopes during the night of 2017 September 3. We ... [more ▼]

A long lightcurve of the near-Earth asteroid 3122 Florence was obtained by combining observations from the TRAPPIST-South (TS) and TRAPPIST- North (TN) telescopes during the night of 2017 September 3. We found its synodic rotation period and amplitude to be 2.352 ± 0.005 h and 0.19 mag. All the data have been submitted to the ALCDEF database. [less ▲]

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See detailInterstellar comet 2I/Borisov as seen by MUSE: C2, NH2 and red CN detections
Bannister, Michele T.; Opitom, Cyrielle; Fitzsimmons, Alan et al

E-print/Working paper (2020)

We report the clear detection of C$_2$ and of abundant NH$_2$ in the first prominently active interstellar comet, 2I/Borisov. We observed 2I on three nights in November 2019 at optical wavelengths 4800 ... [more ▼]

We report the clear detection of C$_2$ and of abundant NH$_2$ in the first prominently active interstellar comet, 2I/Borisov. We observed 2I on three nights in November 2019 at optical wavelengths 4800--9300 Åwith the Multi-Unit Spectroscopic Explorer (MUSE) integral-field spectrograph on the ESO/Very Large Telescope. These data, together with observations close in time from both 0.6-m TRAPPIST telescopes, provide constraints on the production rates of species of gas in 2I's coma. From the MUSE detection on all epochs of several bands of the optical emission of the C$_2$ Swan system, a rich emission spectrum of NH$_2$ with many highly visible bands, and the red (1-0) bandhead of CN, together with violet CN detections by TRAPPIST, we infer production rates of $Q$(C$_2$) = $1.1\times10^{24}$ mol s$^{-1}$, $Q$(NH$_2$) = $4.8\times10^{24}$ mol s$^{-1}$ and $Q$(CN) = $(1.8\pm0.2)\times 10^{24}$ mol s$^{-1}$. In late November at 2.03~au, 2I had a production ratio of C$_2$/CN$=0.61$, only barely carbon-chain depleted, in contrast to earlier reports measured further from the Sun of strong carbon-chain depletion. Thus, 2I has shown evolution in its C$_2$ production rate: a parent molecule reservoir has started sublimating. At $Q$(NH$_2$)/$Q$(CN) = 2.7, this second interstellar object is enriched in NH$_2$, relative to the known Solar System sample. [less ▲]

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See detailComet 66P/du Toit: not a near-Earth main belt comet
Yang, Bin; Jehin, Emmanuel ULiege; Pozuelos Romero, Francisco José ULiege et al

in Astronomy and Astrophysics (2019), 631

Context. Main belt comets (MBCs) are a peculiar class of volatile- containing objects with comet-like morphology and asteroid-like orbits. However, MBCs are challenging targets to study remotely due to ... [more ▼]

Context. Main belt comets (MBCs) are a peculiar class of volatile- containing objects with comet-like morphology and asteroid-like orbits. However, MBCs are challenging targets to study remotely due to their small sizes and the relatively large distance they are from the Sun and the Earth. Recently, a number of weakly active short-period comets have been identified that might originate in the asteroid main belt. Among all of the known candidates, comet 66P/du Toit has been suggested to have one of the highest probabilities of coming from the main belt. <BR /> Aims: The main goal of this study is to investigate the physical properties of 66P via spectroscopic and imaging observations to constrain its formation conditions. In particular, the isotopic abundance ratio and the ortho-to-para ratio (OPR) of gaseous species can be derived via high-resolution spectroscopy, which is sensitive to the formation temperature of the nucleus. <BR /> Methods: We obtained medium and high-resolution spectra of 66P from 300-2500 nm with the X-shooter and the UVES instruments at the Very Large Telescope in July 2018. We also obtained a series of narrow-band images of 66P to monitor the gas and dust activity between May and July 2018 with TRAPPIST-South. In addition, we applied a dust model to characterize the dust coma of 66P and performed dynamical simulations to study the orbital evolution of 66P. <BR /> Results: We derive the OPR of ammonia (NH[SUB]3[/SUB]) in 66P to be 1.08 ± 0.06, which corresponds to a nuclear spin temperature of 34 K. We compute the production rates of OH, NH, CN, C[SUB]3[/SUB], and C[SUB]2[/SUB] radicals and measure the dust proxy, Afρ. The dust analysis reveals that the coma can be best-fit with an anisotropic model and the peak dust production rate is about 55 kg s[SUP]-1[/SUP] at the perihelion distance of 1.29 au. Dynamical simulations show that 66P is moderately asteroidal with the capture time, t[SUB]cap[/SUB] 10[SUP]4[/SUP] yr. <BR /> Conclusions: Our observations demonstrate that the measured physical properties of 66P are consistent with typical short-period comets and differ significantly from other MBCs. Therefore, 66P is unlikely to have a main belt origin. [less ▲]

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See detail2I/Borisov: A C2-depleted interstellar comet
Opitom, Cyrielle; Fitzsimmons, Alan; Jehin, Emmanuel ULiege et al

in Astronomy and Astrophysics (2019), 631

<BR /> Aims: The discovery of the first active interstellar object 2I/Borisov provides an unprecedented opportunity to study planetary formation processes in another planetary system. In particular ... [more ▼]

<BR /> Aims: The discovery of the first active interstellar object 2I/Borisov provides an unprecedented opportunity to study planetary formation processes in another planetary system. In particular, spectroscopic observations of 2I allow us to constrain the composition of its nuclear ices. <BR /> Methods: We obtained optical spectra of 2I with the 4.2 m William Herschel and 2.5 m Isaac Newton telescopes between 2019 September 30 and October 13, when the comet was between 2.5 au and 2.4 au from the Sun. We also imaged the comet with broadband filters on 15 nights from September 11 to October 17, as well as with a CN narrow-band filter on October 18 and 20, with the TRAPPIST-North telescope. <BR /> Results: Broadband imaging confirms that the dust coma colours (B - V = 0.82 ± 0.02, V - R = 0.46 ± 0.03, R - I = 0.44 ± 0.03, B - R = 1.28 ± 0.03) are the same as for Solar System comets. We detect CN emission in all spectra and in the TRAPPIST narrow-band images with production rates between 1.6 × 10[SUP]24[/SUP] and 2.1 × 10[SUP]24[/SUP] molec/s. No other species are detected. We determine three-sigma upper limits for C[SUB]2[/SUB], C[SUB]3[/SUB], and OH production rates of 6 × 10[SUP]23[/SUP] molec/s, 2 × 10[SUP]23[/SUP] molec/s and 2 × 10[SUP]27[/SUP] molec/s, respectively, on October 02. There is no significant increase of the CN production rate or A(0)fρ during our observing period. Finally, we place a three-sigma upper limit on the Q(C[SUB]2[/SUB])/Q(CN) ratio of 0.3 (on October 13). From this, we conclude that 2I is highly depleted in C[SUB]2[/SUB], and may have a composition similar to Solar System carbon-chain depleted comets. [less ▲]

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See detailDetection of CN Gas in Interstellar Object 2I/Borisov
Fitzsimmons, Alan; Hainaut, Olivier; Meech, Karen J. et al

in Astrophysical Journal (2019), 885

The detection of interstellar objects passing through the solar system offers the promise of constraining the physical and chemical processes involved in planetary formation in other extrasolar systems ... [more ▼]

The detection of interstellar objects passing through the solar system offers the promise of constraining the physical and chemical processes involved in planetary formation in other extrasolar systems. While the effect of outgassing by 1I/2017 U1 (’Oumuamua) was dynamically observed, no direct detection of the ejected material was made. The discovery of the active interstellar comet 2I/Borisov means spectroscopic investigations of the sublimated ices is possible for this object. We report the first detection of gas emitted by an interstellar comet via the near-UV emission of CN from 2I/Borisov at a heliocentric distance of r = 2.7 au on 2019 September 20. The production rate was found to be Q(CN) = (3.7 ± 0.4) × 10[SUP]24[/SUP] s[SUP]−1[/SUP], using a simple Haser model with an outflow velocity of 0.5 km s[SUP]−1[/SUP]. No other emission was detected, with an upper limit to the production rate of C[SUB]2[/SUB] of 4 × 10[SUP]24[/SUP] s[SUP]−1[/SUP]. The spectral reflectance slope of the dust coma over 3900 Å < λ < 6000 Å is steeper than at longer wavelengths, as found for other comets. Broadband R [SUB] c [/SUB] photometry on 2019 September 19 gave a dust production rate of Afρ = 143 ± 10 cm. Modeling of the observed gas and dust production rates constrains the nuclear radius to 0.7─3.3 km assuming reasonable nuclear properties. Overall, we find the gas, dust, and nuclear properties for the first active interstellar object are similar to normal solar system comets. [less ▲]

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See detailA photometric and spectroscopic study of the multi-tailed asteroid (6478) Gault
Jehin, Emmanuel ULiege; Moreno, Fernando; Ferrais, Marin ULiege et al

Conference (2019, September 01)

In this presentation, we describe several months of monitoring of Gault since January 2019 using various telescopes and instrumentation. The goal is to characterize and to model the asteroids and the ... [more ▼]

In this presentation, we describe several months of monitoring of Gault since January 2019 using various telescopes and instrumentation. The goal is to characterize and to model the asteroids and the tails to impose constraints on the physical properties of the ejected dust, and to shed light on the activity timeline and the causes for the ejection events. [less ▲]

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See detailPhotometry, imaging and rotation period of comet 46P/Wirtanen during its 2018 apparition
Moulane, Youssef ULiege; Jehin, Emmanuel ULiege; José Pozuelos, Francisco et al

Conference (2019, September 01)

We report on photometry, imaging and the rotation period of the Jupiter Family Comet (JFC) 46P/Wirtanen (hereafter 46P) observed with both TRAPPIST telescopes (TN and TS). We monitored the comet regularly ... [more ▼]

We report on photometry, imaging and the rotation period of the Jupiter Family Comet (JFC) 46P/Wirtanen (hereafter 46P) observed with both TRAPPIST telescopes (TN and TS). We monitored the comet regularly during 8 months, following the evolution of the production rates of the gaseous species, e.g. OH, NH, CN, C3 and C2, as well as the evolution of the Afrho parameter, a dust proxy. Measurements along the orbit of the production rates and the relative abundance with respect to CN and OH will be discussed. We measured the rotation period of the comet using high cadence observations of the CN flux on several nights, we obtained a value of (9.2±0.5) hr on Dec. 9, 2018. The comparison of the coma morphology exhibited by the gas species and the dust will be presented. [less ▲]

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See detailNarrow- and broad-band photometry of the peculiar comet 21P/Giacobini-Zinner during its 2018 apparition
Moulane, Youssef ULiege; Jehin, Emmanuel ULiege; José Pozuelos, Francisco et al

Conference (2019, September 01)

We report on narrow- and broad-band photometry of the Jupiter Family Comet (JFC) 21P/Giacobini-Zinner observed, over than 8 months continuously, with both TRAPPIST telescopes (TN and TS). We monitored the ... [more ▼]

We report on narrow- and broad-band photometry of the Jupiter Family Comet (JFC) 21P/Giacobini-Zinner observed, over than 8 months continuously, with both TRAPPIST telescopes (TN and TS). We monitored the evolution of the gaseous species production rates OH, NH, CN, C3 and C2 as well as the evolution of the Afhro parameter, a dust proxy. Measurements on the production rates and their ratios with respect to CN and to OH will be discussed. The peak of the water production was on August 17, 2018 (rh=1.07 au), 24 days before the perihelion, and it reached (3.72±0.05).10^28 molecules/s, while the peak value of Afrho was (575±12) cm. Comparison of the coma morphology features and the coma colors will be discussed. [less ▲]

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See detailTrappist Lightcurves of Main-Belt Asteroids 31 Euphrosyne, 41 Daphne and 89 Julia
Ferrais, Marin ULiege; Jehin, Emmanuel ULiege; Manfroid, Jean ULiege et al

in Minor Planet Bulletin (2019), 46

Densely sampled lightcurves of three large main-belt asteroids were obtained with the TRAPPIST-South (TS) and TRAPPIST-North (TN) telescopes from 2017 September to 2018 July. We found their synodic ... [more ▼]

Densely sampled lightcurves of three large main-belt asteroids were obtained with the TRAPPIST-South (TS) and TRAPPIST-North (TN) telescopes from 2017 September to 2018 July. We found their synodic rotation periods and amplitudes to be: 31 Euphrosyne, 5.5312 ± 0.0007 h and 0.07 mag; 41 Daphne, 5.9912 ± 0.0028 h and 0.18 mag; and 89 Julia, 11.3844 ± 0.0002 h and 0.19 mag. All data have been submitted to the ALCDEF database. [less ▲]

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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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