Emission lines of FeI and NiI are commonly found in the coma of Solar System comets, even at large heliocentric distances. These atoms are most likely released from the surface of the comet’s nucleus or from a short-lived parent. The presence of these lines in cometary spectra is unexpected because the surface blackbody equilibrium temperature is too low to allow the sublimation of refractory minerals containing these metals. These lines were also found in the interstellar comet 2I/Borisov, which has a NiI/FeI abundance ratio similar to that observed in Solar System comets. On average, this ratio is one order of magnitude higher than the solar Ni/Fe abundance ratio. Here, we report observations of the interstellar comet 3I/ATLAS, which were carried out with the ESO Very Large Telescope equipped with the UVES and X-shooter spectrographs. Spectra were obtained at heliocentric distances ranging from 3.14 to 1.85 au. Nil was detected at all epochs. FeI was only detected at heliocentric distances smaller than 2.64 au. We estimated the Nil and FeI production rates by comparing the observed line intensities with those produced by a dedicated fluorescence model. Comet 3I first exhibited extreme and unusual NiI/FeI abundance ratios during the initial stages of its activity. However, as its heliocentric distance decreased, this ratio became indistinguishable from those observed in Solar System comets and in comet 2I∕Borisov. Comet 3I was found to be C2-depleted, with a NiI/FeI abundance ratio finally consistent with other C2-depleted comets. Nevertheless, comet 3I remains exceptional due to its high, total production rate of NiI and FeI, which is at least one order of magnitude larger than that of other comets. We interpreted these observations assuming that the NiI and FeI atoms were released through the sublimation of Ni(CO)4 and Fe(CO)5 carbonyls. This scenario provides a straightforward explanation for the asymmetric release of NiI and FeI atoms in the cometary coma and how it depends on the heliocentric distance. It also supports the presence of carbonyls in the cometary material.

We present high-resolution UVES+VLT observations of neutral nickel and iron atoms in the coma of the interstellar comet 3I/ATLAS taken after perihelion. Metal emission was strong shortly after perihelion and persisted at large heliocentric distances. At r_h ∼ 2 au the total metal production rate was found to be at least an order of magnitude larger than that of typical solar-system comets. Post-perihelion production rates exhibit pronounced asymmetry compared to the pre-perihelion behavior: production rates are higher after perihelion and decline more gradually with r_h, the difference being stronger for FeI. The NiI/FeI abundance ratio, initially anomalously large before perihelion, evolved toward values comparable to solar-system comets near 2 au, and shows a weaker r_h dependence after perihelion. To interpret these results, we revisited and extended the carbonyl hypothesis in which FeI and NiI are produced by the rapid photodissociation of Fe(CO)_5 and Ni(CO)_4 vaporized from the nucleus. Fits that include direct sublimation of carbonyls reproduce the observed rates and the high NiI/FeI line ratio, which is determined by the higher volatility of Ni(CO)_4. Desorption of carbonyls from sublimating CO_2 and H_2O ices is found to be negligible. The temperature profiles needed to reproduce the observations were found to be shallower than the equilibrium T ∝ r_h^-1/2 relation, suggesting that the sublimation could occur below the surface of the nucleus. Fits using temperature profiles from thermal models require sublimation from depths of several cm, especially post-perihelion. An additional transient heat source (T ≃ 100-140 K), possibly linked to the amorphous-crystalline ice transition, is proposed to explain the early NiI excess before perihelion.

Comet C/2023 A3 (Tsuchinshan-ATLAS) is a non-periodic dynamically new Oort cloud comet that was discovered independently by Purple Mountain Observatory in China and Asteroid Terrestrial-impact Last Alert System (ATLAS) telescopes in South Africa. The comet passed perihelion at a distance of 0.39 AU on 27 September 2024. It was visible to the naked eye (the brightest since the comet C/1995 O1 (Hale-Bopp)) and was dubbed the great comet of 2024. In this work, we investigate the nature of this comet, which is moving in a hyperbolic orbit (e > 1), by analysing its composition using various observational techniques and tracing its orbital evolution through high-precision N-body simulations.

Introduction:Roughly a hundred comets approach perihelion annually, yet only a fraction undergo thorough study due to the scarcity of observation time on larger and fewer available telescopes. However, comets are known to exhibit unpredictable variations for diverse reasons. Consequently, observing them on a restricted number of nights may yield a biased understanding of their evolution and composition. Acquiring homogeneous physical data from a broad sample is crucial for comprehending the distribution of their physical and chemical properties. In this work, we present results from long-term photometric monitoring and some epochs from spectroscopic observations of four long-period comets (LPCs) and four dynamically new comets (DNCs) obtained between 2013 and 2024. These comets include C/2017 T2 (PanSTARRS), disintegrated comet C/2019 Y4 (ATLAS), the very bright comet C/2020 F3 (NEOWISE), C/2020 M3 (Atlas), C/2012 K1 (PANSTARRS), C/2018 W2 (Africano), C/2020 V2 (ZTF), and C/2021 S3 (PANSTARRS).Our work contributes to the understanding of the cometary behavior of these two dynamical classes originating from the Oort Cloud which could be used for predictions of future comet observations or help to identify potential targets for future ESA Comet Interceptor mission [1]. Photometry (TRAPPIST):We used both TRAPPIST-North (TN) and –South (TS) [2], to observe and follow those LPCs and DNCs along their orbits. These telescopes are equipped with standard Johnson-Cousin B, V, Rc, and Ic filters, as well as narrow-band filters CN, C3, C2, NH, and OH to compute the production rates (Qs) from the gas species and BC, GC, and BC to compute the dust proxy (Afρ) for the dust continuum [3]. Spectroscopy (HFOSC/HCT and LISA/MIRO):Low-resolution long-slit spectra were acquired with the Himalaya Faint Object Spectrograph and Camera (HFOSC) [4], installed on the 2m Himalayan Chandra Telescope (HCT), and the 1.2 m telescope of the Mount Abu Infrared Observatory (MIRO), with the assistance of the Long slit Intermediate resolution Spectrograph for Astronomy (LISA) [5]. Figure 1: BVRI magnitude within radius aperture of 5" as a function of days to perihelion for comets C/2017 T2, C/2018 W2, C/2020 F3, C/2020 M3, and as a function of days to the disintegration for comet C/2019 Y4.*The magnitude formula: m = M0 + 5 log(rg) + 2.5 n log(rh). Table 1: TRAPPIST observational circumstances and dynamical types of the comets reported in this work. All the orbital elements are taken from the NASA JPL/Horizon database.Figure 2: The Optical spectrum of comets C/2017 T2, C/2018 W2, C/2019 Y4, C/2020 F3, and C/202 M3. For the disintegrated comet C/2019 Y4 (ATLAS), Top: Optical spectrum of 19Y4 before disintegration on 2020-02-23; middle: during disintegration on 2020-03-15, and bottom: after disintegration on 2020-05-26. AcknowledgmentsTRAPPIST is a project funded by the Belgian “Fonds National de la Recherche Scientifique” (F.R.S.-FNRS) under grant T.0120.21. This work is supported by the BIPASS program from the International Division of the Department of Science and Technology (DST; Govt. of India) and the Belgian Federal Science Policy Office (BELSPO; Govt. of Belgium). acknowledges support for the grant from the Academy of Research and Higher Education (ARES). References:[1] Jones, Geraint H et al. 2024, The Comet Interceptor Mission.[2] E. Jehin et al. 2011, The Messenger, 145, 2-6.[3] Farnham, T., Schleicher, D., & A’Hearn, M. (2000), Icarus, 147, 180.[4] Aravind, K et al. 2021. Mon. Not. R. Astron. Soc. 502 (3), 3491–3499.[5] Venkataramani, K., 2019. Optical Spectroscopic Studies of Minor Bodies of the Solar System (PhD Thesis).

Comets are pristine remnants of the Solar system, composed of dust and ice. They remain inactive and undetectable for most of their orbit due to low temperatures. However, as they approach the Sun, volatile materials sublimate, expelling dust and creating a visible coma. Spectroscopic observations of comets help the simultaneous study of both the gas emissions and reflected sunlight from dust particles. By implementing a long slit, the spatial variations in molecular emissions can be analysed to be further used for other computations. Additionally, spatial information aids in extracting the characteristic profile of the Afρ parameter, revealing insights into the behaviour of dust emissions. A sufficiently long slit would prove advantageous in extracting information about the emissions occurring at different parts of the coma or even the tail. We can gain an overall comprehensive understanding of a comet’s chemical composition and dust emission by constructively utilising low-resolution spectroscopy with the help of a long slit.

We present pre-perihelion photometric and spectroscopic observations of comet 12P/Pons-Brooks (hereafter 12P) during its 2024 passage. 12P is a comet on a Halley-type orbit with a period of 71 years that showed during its recent approach several impressive outbursts[1], with an interesting double horn shaped dust coma which earned it the nickname of "devil comet". The comet, discovered in 1812, had already experienced outbursts during previous passages [2]. We observed the comet over 125 nights with the TRAPPIST-North telescope [3] from May 6, 2023 (rh = 4.62 au), to March 16, 2024 (rh = 1.02 au), when it was too close to the Sun to be observed. We collected images with broad-band Johnson–Cousins filters (BVRI) as well as narrow-band HB filters [4] (OH, CN, C2, C3 and NH for gas species and BC, GC and BC for the dust continuum) to compute the comet lightcurve in BVRI, the gas activity using the Haser model [5], and the dust activity proxy af(0)rho [6]. From the lightcurve and images we detect at least 6 major outbursts with an increase up to 4 magnitudes (see Fig. 1 and [1]) along with gas and dust increase; OH production rate reaching values as high as 1029 molecules/s and af(0)rho as high as 105 cm. Interestingly, most of the outbursts where observed at a heliocentric distance higher than 3 au, where supervolatiles such as CO2 and CO probably drives cometary activity. It indicates that the outburst mechanism might be similar to other far away comets such as the centaur 29P/Schwassmann–Wachmann 1 that shows regular outbursts at an heliocentric distance of ~ 6 au [7]. The outbursts and their subsequent fall-off were observed with narrow-band filters allowing the study of the gas and dust ratios behavior during those events. The analysis of the images in the various filters shows the evolution of the peculiar 12P coma shape with the activity.To complement the TRAPPIST photometric dataset, long-slit low resolution spectra were obtained at the Observatoire de Haute Provence with the MISTRAL instrument [8] (5.5’x1.9’’ slit, R∼700@6000 Å) on the night of March 23, 2024, when the comet was at a heliocentric distance of 0.94 au (Fig. 2). Spectra was extracted from the observed data and calibrated to analyse the emissions from the different molecular bands. While the usual emission bands from the neutral molecular species, C2 , NH2 , CN, are observed, additionally, a tentative detection of H2O+ has also been made.Fig. 1: 12P/Pons-Brooks magnitude in the R band from the TRAPPIST survey. Several outbursts with a 1 to 4 magnitude increase can be observed. The lightcurve covers observations from May 6, 2023 (rh = 4.62 au), to February 25, 2024 (rh = 1.27 au)Fig. 2: 120s spectra of 12P taken with MISTRAL at Observatoire de Haute Provence with a 1,9’’ wide slit, dust subtracted and extracted on the photocenter. Different emission bands are visible, including tentative detections of H2O+.References[1] ATel#16194, ATel#16202, ATel#16223, ATel#16229, ATel#16254, ATel#16270, ATel#16282, ATel#16315, ATel#16338, ATel#16343, ATel#16408, ATel#16498[2] Gary W Kronk, Cometography: a catalog of comets. Vol. 4, 1933-1959, Cambridge University Press (2009)[3] Jehin, E. et al. TRAPPIST: TRAnsiting Planets and PlanetesImals Small Telescope. The Messenger 145, (2011).[4] Farnham, T. The HB Narrowband Comet Filters: Standard Stars and Calibrations. Icarus 147, 180–204 (2000).[5] Haser, L. Distribution d’intensité dans la tête d’une comète. Bulletins de l'Académie Royale de Belgique 43 pp. 740-750 (1957)[6] A'Hearn et al., Comet Bowell 1980b, The Astronomical Journal 89-4, 579-591 (1984)[7] see the MISSION 29P campain: https://britastro.org/section_information_/comet-section-overview/mission-29p-2[8] Schmitt, J. et al. Multi-purpose InSTRument for Astronomy at Low-resolution: MISTRAL@OHP. Preprint at http://arxiv.org/abs/2404.03705 (2024).AcknowledgmentsTRAPPIST is a project funded by the Belgian Fonds (National) de la Recherche Scientifique (F.R.S.-FNRS) under grant T.0120.21. This work is supported by the BIPASS program from the International Division of Department of Science and Technology (DST; Govt. of India) and the Belgian Federal Science Policy Office (BELSPO; Govt. of Belgium). M.V.D. acknowledges support from the French-speaking Community of Belgium through its FRIA grant

ABSTRACT Observing the vibrational/rotational lines in a comet’s optical spectrum requires high-resolution spectroscopy, as they are otherwise seen as a blended feature. To achieve this, we have obtained medium and high-resolution (R (λ/Δλ) = 30 000 and 60 000) spectra of several comets, including C/2015 V2 (Johnson), 46P/Wirtanen, 41P/Tuttle–Giacobini–Kresák, and 38P/Stephan–Oterma, using the Hanle Echelle Spectrograph (HESP) mounted on the 2-m Himalayan Chandra Telescope (HCT) in India. The spectra effectively cover the wavelength range 3700–10 000 Å, allowing us to probe the various vibrational bands and band sequences to identify the rotational lines in the cometary molecular emission. We were also able to separate the cometary Oxygen lines from the telluric lines and analyse the green-to-red (G/R) forbidden oxygen [O i] ratios in a few comets. For comets C/2015 V2, 46P, and 41P, the computed G/R ratios, 0.04 ± 0.01, 0.04 ± 0.01, and 0.08 ± 0.02, respectively, point to H2O being a major source of Oxygen emissions. Notably, in the second fibre pointing at a location 1000 km away from the photocentre of comet 46P, the G/R ratio reduced by more than half the value observed in the first fibre, indicating the effects of quenching within the inner coma. We also measured the NH2 ortho-to-para ratio of comet 46P to be about 3.41 ± 0.05 and derived an ammonia ratio of 1.21 ± 0.03 corresponding to a spin temperature of ∼26 K. With these, we present the results of the study of four comets from different cometary reservoirs using medium and high-resolution optical spectroscopy, emphasizing the capabilities of the instrument for future cometary studies.

Jupiter family comets, having an orbital period <20 years, allow us to observe their activity and analyze the homogeneity in their coma composition over multiple apparitions. Comet 46P/Wirtanen, with its exceptionally close approach to Earth during its 2018 apparition, offered the possibility for long-term spectroscopic observations. We used a 1.2 m telescope equipped with a low-resolution spectrograph to monitor the comet’s activity and compute the relative abundances in the coma as a function of heliocentric distance. We report the production rates of four molecules CN, C _2 , C _3 and NH _2, and Af ρ parameter, a proxy to the dust production, before and after perihelion. We found that 46P has a typical coma composition with almost constant abundance ratios with respect to CN across the epochs of observation. Comparing the coma composition of comet 46P during the current and previous apparitions, we conclude the comet has a highly homogeneous chemical composition in the nucleus with an enhancement in ammonia abundance compared to the average abundance in comets.

Context. Lunar swirls are high-albedo irregular markings that are generally associated with prominent magnetic anomalies. The formation of swirls is still unknown. Near-infrared spacecraft-based imaging suggests reduced space weathering at the locations of swirls. However, the reduced space weathering alone cannot explain the observed spectral properties. Aims. We provide detailed physical characteristics of the regolith at the Reiner Gamma swirl. For the first time, systematic telescopic observations in a range of phase angles are used to derive the surface roughness, opposition effect strength, and grain size distribution at a spatial resolution of 1 km. Methods. Imaging polarimetric observations of Reiner Gamma were obtained at the Mount Abu IR Observatory between January and March, 2021. These observations were collected with the two narrow-band continuum filters, GC (green) and RC (red), in a range of phase angles. The georeferenced polarimetric images were used to derive the single-scattering albedo, photometric roughness, and amplitude of the opposition effect by adopting the Hapke reflectance model. We further computed median regolith grain size maps of Reiner Gamma using the derived photometric roughness, albedo, and degree of polarization. Results. A comparison of the polarization properties of Reiner Gamma swirl with the craters Kepler and Aristarchus suggests grain size variations within the swirl structure. The Hapke modeling of the Reiner Gamma swirl suggests significant changes in the opposition effect strength at the central oval, but only marginal differences in surface roughness from its surroundings. Within the swirl, the median grain size varies significantly in comparison to the background mare grain size of ~45 µm. Conclusions. Our results confirm the occurrence of surface alteration processes that might have disrupted the regolith microstructure in the Reiner Gamma swirl. These findings are consistent with an external mechanism of swirl formation, by considering interaction between the regolith and cometary gas. Subsequent to its formation, the swirl structure was preserved due to shielding by crustal magnetic field.

Comet 156P/Russell-LINEAR is a short period Jupiter family comet with an orbital period of 6.44 years. The results from spectroscopic, photometric, polarimetric observations and dust modelling studies are presented here. From the spectroscopic study, strong emissions from CN(Δν=0), C3 (λ4050 Å), C2(Δν=+1) and C2(Δν=0) can be observed during both the epochs of our observations. The Q(C2)/Q(CN) ratio classifies the comet as a typical comet. The imaging data reveals the presence of jets. The dust emission from the comet is observed to have a non-steady state outflow due to the presence of these strong jets which subside in later epochs, resulting in a steady state outflow. Polarimetric study at two different phase angles reveals the degree of polarization to be comparable to Jupiter family comets at similar phase angles. Localized variations in polarization values are observed in the coma. The dust modelling studies suggest the presence of high amount of silicate/low absorbing material and indicate the coma to be dominated by higher amount of large size grains with low porosity having power law size distribution index = 2.4. The observed activity and dust properties points to a similarity to another Jupiter family comet, 67P/Churyumov–Gerasimenko.

Comet 2I/Borisov is the first true interstellar comet discovered. Here we present results from observational programs at two Indian observatories, 2 m Himalayan Chandra Telescope at the Indian Astronomical Observatory, Hanle (HCT) and 1.2 m telescope at the Mount Abu Infrared Observatory (MIRO). Two epochs of imaging and spectroscopy were carried out at the HCT and three epochs of imaging at MIRO. We found CN to be the dominant molecular emission on both epochs, 31/11/2019 and 22/12/2019, at distances of rH = 2.013 and 2.031 AU respectively. The comet was inferred to be relatively depleted in Carbon bearing molecules on the basis of low C2 and C3 abundances. We find the production rate ratio, Q(C2)/Q(CN) = 0.54 ± 0.18, pre-perihelion and Q(C2)/Q(CN) = 0.34 ± 0.12 post-perihelion. This classifies the comet as being moderately depleted in carbon chain molecules. Using the results from spectroscopic observations, we believe the comet to have a chemically heterogeneous surface having variation in abundance of carbon chain molecules. From imaging observations we infer a dust-to-gas ratio similar to carbon chain depleted comets of the Solar system. We also compute the nucleus size to be in the range 0.18 ≤ r ≤ 3.1 Km. Our observations show that 2I/Borisov’s behaviour is analogous to that of the Solar system comets.

This paper aims at the detection of the fault occurring in an underground cable system, pinpoint the location of the fault using Extreme Learning Machine and convey the parameters of the fault occurred using Internet of Things (IoT). The underground cables have seen a steep increase in usage due to its many inherent advantages compared to the overhead cables. However, various methods to pinpoint the presence of fault in the underground cables of large lengths has proved futile and the communication of the fault information has been proved to be expensive. Our proposed project uses Extreme Learning Machine to detect the type of fault and to pinpoint the location of the fault in the system. Extreme Learning Machine Classification and Regression Algorithms are utilized to predict the type of fault in the system and the distance of the fault from the sending end. The regression algorithm is compared to other ML algorithms relevant to the subject matter at hand. The fault location conveyed by the use of GSM is limited by the fact that only text messages in the form of Short Messaging Services can be sent to the user concerned increasing the cost incurred by the user. Our project uses the internet to communicate through a big arsenal of methods, like e-mail and other social media services possible, thus widening the scope of communication while decreasing the size of the product.

Light-induced reactions are the first step of many chemical and biological processes like vision and photosynthesis. The timescale of such reactions is of the order of picoseconds to nanoseconds, so studying these ultrafast reactions in real-time requires the use of intense ultrashort lasers having tens of femtoseconds (fs) or shorter pulse duration. In this study, we have used 800 nm, 29 fs, 1 kHz pulses from a Ti:sapphire laser to study the photodissociation of gas-phase CH3OH in a home-built Velocity Map Imaging Spectrometer (VMIS). Strong-field ionization of methanol with the laser pulses results in processes like excitation, ionization, bond-breaking, intramolecular H-atom migration, and bond association, prior to complete molecular fragmentation. Our study focused on the intramolecular H-atom migration in methanol, leading to the formation of Hn+ (n=1-3) ions, and controlling the yield of the Hn + ions using different laser parameters like intensity, pulse duration, wavelength, and polarization. We have confirmed the H2 + and H3 + formation Figure: (left) (a) Schematic diagram of the experimental setup. (b) (I) and (II) show the Hn + (n=1, 2, 3) ions’ VMI images for 800 nm, 29 fs and 195 fs pulses, respectively, (III) shows the time-of-flight (TOF) mass spectrum recorded for methanol, (c) pulse characterization using SPIDER, and (d) multi-plate VMIS. (right) Normalised yield of H2 + and H3 + ions for 800 nm and 1300 nm pulses, plotted as a function of laser intensity. Strong-field ionization of polyatomic molecules

An Andor 1K x 1K EMCCD detector has been used to develop an optical imaging polarimeter for use at the Cassegrain focus of 1.2 m telescope of PRL. The optics is derived from an older single-element detector instrument and consists of a rotating half-wave plate as modulator and a Foster prism as an analyser. The field of view of the instrument is 3x3 sq arcmin. We describe the instrument and the observational methodology in this document. Extensive observations have been carried out with this instrument covering a large variety of sources e.g. near-Earth asteroids, comets, Lynds dark nebulae, open clusters and AGN such as blazars. In the current communication, we discuss some results from the initial calibration runs while the other results will be presented elsewhere.

Indian astronomers have been using their relatively modest instruments and telescopes to contribute greatly in understanding the minor bodies of the solar system. Here we discuss some of the results from observations using Indian facilities by researchers from India and abroad. Results are discussed in imaging/photometry, polarimetry and spectroscopy from the Indian telescopes up to 2 metres in aperture. It is hoped that access to the upcoming 2-m and 4-m class telescopes and sophisticated instrumentation would greatly improve our understanding with more exciting results coming up in future. Access to 2-m and 4-m class telescopes are one of the key points of the BINA collaboration. It is expected that our understanding of the solar system bodies, particularly the minor bodies and other small objects, would be greatly enhanced in terms of statistics as well as detailed characterization of individual ones.