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 detailMonitoring the activity and composition of comets with TRAPPIST telescopes
Moulane, Youssef ULiege

Doctoral thesis (2021)

Comets are remnants of the early stages of the Solar System and the most primitive Solar System bodies. Understanding their nature and evolution history provides important clues about the formation of the ... [more ▼]

Comets are remnants of the early stages of the Solar System and the most primitive Solar System bodies. Understanding their nature and evolution history provides important clues about the formation of the Solar System and the planets. Comets contain complex organic molecules, and may have played a key role in delivering water, organics and noble gases from the interstellar medium to the early Earth, contributing to the origin of life. The strong scientific interest in the Solar System small bodies is well demonstrated by numerous space missions in the recent years, such as Stardust, Deep Impact, Dawn and New Horizon etc. Particularly, ESA’s very successful Rosetta mission recently visited comet 67P/Churyumov–Gerasimenko and made several ground-breaking discoveries that have dramatically increased our knowledge about comets. However, most of the space missions can only perform short-term studies over a narrow time window of single objects. We are currently lacking long-term observations to study variations in the activity and composition in the coma of a comet and how it evolves along its orbit around the Sun. We regularly use the two robotic TRAPPIST telescopes to observe relatively bright comets (V<12 mag) that are visible in both hemispheres. These telescopes are equipped with narrow-band cometary filters that allow us to collect images of a comet at wavelengths where the light is emitted by the main gaseous species accessible in the optical (OH, NH, CN, C2, and C3). In addition, we observe comets in three continuum windows (scattered sunlight) that allow us to characterize the dust component of the comet. Thanks to the large amount of telescope time available on both telescopes for this project, we collected a unique data set of thousands of photometric measurements of 35 comets including 18 Jupiter-family Comets (hereafter JFCs) and 16 Long Period Comets (hereafter LPCs) in addition to the first active interstellar comet 2I/Borisov which was discovered in 2019. Each comet is monitored along an important part of its inner solar system orbit, starting at 3 au from the Sun (where water start to sublimate) and all the way to its perihelion. Post perihelion, we followed the comet again all the way out to 3 au at least. Then, through cometary coma models, the abundances of the main chemical species (accessible in the optical part of the spectrum) and dust production proxy (known as Afrho) and its color were determined. These measurements, thanks to the high quality and homogeneity of the observations and of the verified analysis procedure, allowed us to address important and long debated questions like the existence of comet compositional classes (comet taxonomy), the changes of molecular abundance ratios with the distance to the Sun and the link between chemical composition and dynamical origins, which is a fundamental step in understanding the formation of comets and the Solar System itself. Among 29 comets for which the gas emissions were detected (at least CN and C2), we identified three depleted comets in carbon-chain elements. These comets are 21P/Giacobini–Zinner, 260P/McNaught and 398P/Boattini in addition to the first interstellar comet 2I/Borisov. 21P is known as a depleted comet for a long time , but we confirm its depletion in its 2018 passage. The other three comets were found to be depleted in C2 and C3 for the first time with TRAPPIST. We made an extensive monitoring of the activity of the first interstellar comet 2I/Borisov. We presented an initial characterization of its activity including magnitude, Afrho dust parameter and dust colours during our observation period. 2I/Borisov was found to be depleted in C2 with respect to CN similar to the Solar System comets carbon-depleted group. No LPC was found to be depleted in carbon-chain elements, except for comet C/2019 Y4 which was at the limit of depleted comets before its fragmentation where we see a significant change in its coma composition. We also found four comets (21P, C/2015 V2, C/2017 T2 and C/2018 W2) depleted in NH with respect to OH and CN. In term of dust activity, most comets show a normal dust/gas activity with respect to the heliocentric distance, except for comet C/2017 O1 which shows a higher dust/gas ratio (especially for Afrho/OH) and comet C/2018 Y1 that shows a lower dust/gas ratio (in both Afrho/OH and Afrho/CN) with respect to most comets. We made a follow-up of five JFCs that showed outbursts. These comets include 29P/Schwassmann-Wachmann 1, 123P/West-Hartley, 155P/Shoemaker, 243P/NEAT, and 260P/McNaught. Comet 29P, as usual, shows multiple outbursts with various amplitudes while other comets show an unique outburst. We discussed the evolution of the outbursts for each comet, by measuring the magnitude, Afrho parameter and dust colours. The dense monitoring of comets allows us to investigate new topics like the heterogeneity of the nuclei composition and the determination of their rotation period through the analysis of the flux variations and of the coma features (jets). We found that the rotation period of comet 41P was surprisingly changed by 26 hr in just two months while the rotation period of comet 46P did not change on both sides of perihelion with an average value of 9.10±0.05 hr. The regular measurements of the comets activity and composition from optical measurements are also invaluable to support observing programs on larger ground based or space telescopes that we plan with our collaborators or other groups to perform complementary studies of the most interesting objects through optical and IR spectrometers (e.g, 21P and 66P/du Toit). In this work, we also discussed the reactive collision of electrons with molecular cations in cometary coma. In order to improve our understanding of the kinetics of the cometary coma, theoretical studies of the major reactive collisions in these environments are needed. Deep in the collisional coma, inelastic collisions between thermal electrons and molecular ions result in dissociation and vibrational excitation of the ions, the rates of these processes are especially elevated due to the high ion and electron densities in the inner cometary coma. We presented the study of reactive collisions of electrons with CO+ and H2+ molecular cations using the multi channel quantum defect theory (MQDT), such as dissociative recombination (DR), vibrational excitation (VE) and vibrational de-excitation (VdE), to understand the importance of these reactive collisions in producing carbon, oxygen and hydrogen atoms in cometary activity. The results shows that among all reactive collisions taking place between low energy electrons and CO+/H2+, the dissociative recombination is the most important process at electronic temperatures characteristic of comets, which can be a major source of atoms in the cometary coma at small cometocentric distances. [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 detailVLT multi-instrument observations of comet 46P/Wirtanen
Opitom, Cyrielle; Hutsemekers, Damien ULiege; Manfroid, Jean ULiege et al

Conference (2019, September 01)

We present observations of the Jupiter family comet 46P/Wirtanen performed at the ESO/VLT in December 2018 with three different instruments: the high-resolution spectrographs UVES and ESPRESSO, and the ... [more ▼]

We present observations of the Jupiter family comet 46P/Wirtanen performed at the ESO/VLT in December 2018 with three different instruments: the high-resolution spectrographs UVES and ESPRESSO, and the MUSE integral field spectrograph. Combining those observations, we investigate the coma composition and main activity drivers of 46P, as well as species parentage and jets in its coma. [less ▲]

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See detailModeling of the CO+ emission spectrum in comet C/2016 R2 (PanSTARRS)
Rousselot, Philippe; Jehin, Emmanuel ULiege; Curti, Mathieu et al

Conference (2019, September 01)

The long period comet C/2016 R2 (PanSTARRS), discovered on 2016 September 7 by the PansSTARRS telescope, presented an unusual composition. Most of the emission lines due to radicals usually abundant in ... [more ▼]

The long period comet C/2016 R2 (PanSTARRS), discovered on 2016 September 7 by the PansSTARRS telescope, presented an unusual composition. Most of the emission lines due to radicals usually abundant in comets (such as C2, CN, C3 ) appeared to be faint while unexpected strong emission lines due to N2+ and CO+ ions were clearly apparent in the spectra obtained in the optical range (some fainter CO2+ emission lines were also present). It is the first comet with such bright N2+ emission lines but also the brightness and abundance of CO+ lines allow to study this ion in great details. We obtained in February 2018 high resolution spectra with the ESO 8-m Very Large Telescope and the UVES spectrograph, that allowed us to obtain a CO+ spectrum with an unprecedented signal-to-noise ratio. We also developed a fluorescence model for CO+ to model these spectra. We will present these observations, their modeling and a first estimate of the 12C/13C isotopic ratio for CO+ ions in comet C/2016 R2. It is the first measurement of such a ratio with ground-based telescopes, the only related measurement published so far being done in situ in the coma of comet 67P/Churyumov-Gerasimenko by the ROSINA instrument on-board the Rosetta spacecraft for CO and CO2 molecules. [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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