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Contains fulltext : 292560.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 292035.pdf (Publisher’s version ) (Closed access) 03 maart 2023

The majority of massive stars are born in binaries, and most unbind upon the first supernova. With precise proper motion surveys such as Gaia, it is possible to trace back the motion of stars in the vicinity of young remnants to search for ejected companions. Establishing the fraction of remnants with an ejected companion, and the photometric and kinematic properties of these stars, offers unique insight into supernova progenitor systems. In this paper, we employ binary population synthesis to produce kinematic and photometric predictions for ejected secondary stars. We demonstrate that the unbound neutron star velocity distribution from supernovae in binaries closely traces the input kicks. Therefore, the observed distribution of neutron star velocities should be representative of their natal kicks. We evaluate the probability for any given filter, magnitude limit, minimum measurable proper motion (as a function of magnitude), temporal baseline, distance and extinction that an unbound companion can be associated with a remnant. We compare our predictions with results from previous companion searches, and demonstrate that the current sample of stars ejected by the supernova of their companion can be increased by a factor of 5-10 with Gaia data release 3. Further progress in this area is achievable by leveraging the absolute astrometric precision of Gaia, and by obtaining multiple epochs of deep, high resolution near-infrared imaging with the Hubble Space Telescope, JWST and next-generation wide-field near-infrared observatories such as Euclid or the Nancy Grace Roman Space Telescope., Comment: Accepted for publication in MNRAS. 19 pages, 17 figures

Tidal disruption events (TDEs) are highly energetic phenomena that occur when a star is tidally disrupted by the central massive black hole in a galaxy. Fitting the observed X-ray spectra of TDEs with a first-principles, general-relativistic slim-disk model for the emission from the inner accretion disk can constrain the black hole mass M • and dimensionless spin a •. Multiepoch spectra can break degeneracies in parameter estimation, particularly when they include a period of super-Eddington mass accretion. Even one observed super-Eddington epoch can be useful. Constraints on {M •, a •} improve as a power law with the number of spectral counts; the power-law index is higher for a higher mass accretion rate. These results are supported by the successful modeling of real spectra in the nearby (0.0206 ≤ z ≤ 0.145) TDEs ASASSN-14li, 3XMM J150052.0+015452, and 3XMM J215022.4–055108, which were observed over multiple epochs with >1 ks exposure times. Guided by these results, we create an updated and expanded TDE catalog from the Open TDE compilation. We then explore the XMM-Newton and Chandra archives to identify 37 TDE candidates with promising spectra for constraining {M •, a •} with slim-disk model fits. At least seven TDEs are likely associated with intermediate-mass black holes. Three of the 24 TDEs with multiepoch UV/optical photometry from Swift have late-time observations that allow their light curves to be compared directly to model predictions from the X-ray spectral fits. Existing X-ray spectra for other TDEs can be augmented with future optical/UV data. Ultimately, our new TDE catalog will reveal the {M •, a •} distributions traced by TDEs, thereby discriminating among black hole growth scenarios and providing insights on general relativity and dark matter particle candidates. The new TDE catalog is here: https://github.com/aarongoldtooth/Census-of-TDE-and-Archival-X-Ray-UV-Data/blob/main/Full%20New%20TDE%20Catalog%20(Published).tsv, and the codes used to construct it are here: https://github.com/aarongoldtooth/Census-of-TDE-and-Archival-X-Ray-UV-Data.

The next generation Event Horizon Telescope (ngEHT) will observe multiple supermassive black hole (SMBH) candidates down to a few tens of mJy, and profoundly transform our understanding of the local SMBH population. Given the impossibility of large-area high-resolution millimeter surveys, multi-frequency spectral energy densities (SEDs), and models are required to both identify source samples tailored to specific science goals, and to predict the feasibility of detection of individual interesting sources. Here, we present the Event Horizon and Environs (ETHER) source and SED model database whose primary use is to enable the selection and optimization of targets for EHT and ngEHT science. The living ETHER database currently consolidates 1.6 million black hole mass estimates, ∼15,500 milliarcsec-scale radio fluxes, ∼14,000 hard X-ray fluxes (expected to grow by factor ≳40 with the eROSITA data release) and SED information as obtained from catalogs and database queries, the literature, and our own new observations. Jet and accretion flow models are fit to individual SEDs in an automated way in order to predict the ngEHT observable fluxes from the jet base and accretion inflow. The database can be filtered by parameters or cross matched to a user source list, with the automated SED fitting models optionally fine tuned by the user. We have identified an initial ngEHT ‘gold sample’ for jet base studies and potentially black hole shadows; this sample will grow significantly in the coming years. While the ngEHT requires and will best exploit the ETHER database, six (eleven) ETHER sources have already been observed (scheduled) with the EHT in 2022 (2023), and the database has wide ranging applications in galaxy and black hole mass evolution studies.

Stars that interact with supermassive black holes (SMBHs) can either be completely or partially destroyed by tides. In a partial tidal disruption event (TDE) the high-density core of the star remains intact, and the low-density, outer envelope of the star is stripped and feeds a luminous accretion episode. The TDE AT2018fyk, with an inferred black hole mass of $10^{7.7\pm0.4}$ M$_{\odot}$, experienced an extreme dimming event at X-ray (factor of $>$6000) and UV (factor $\sim$15) wavelengths $\sim$500--600 days after discovery. Here we report on the re-emergence of these emission components roughly 1200 days after discovery. We find that the source properties are similar to those of the pre-dimming accretion state, suggesting that the accretion flow was rejuvenated to a similar state. We propose that a repeating partial TDE, where the partially disrupted star is on a $\sim 1200$ day orbit about the SMBH and is periodically stripped of mass during each pericenter passage, powers its unique lightcurve. This scenario provides a plausible explanation for AT2018fyk's overall properties, including the rapid dimming event and the rebrightening at late times. We also provide testable predictions for the behavior of the accretion flow in the future: if the second encounter was also a partial disruption then we predict another strong dimming event around day 1800 (August 2023), and a subsequent rebrightening around day 2400 (March 2025). This source provides strong evidence of the partial disruption of a star by a SMBH., ApJ Letters, accepted for publication

The Event Horizon Telescope (EHT) has recently released high-resolution images of accretion flows onto two supermassive black holes. Our physical understanding of these images depends on accuracy and precision of numerical models of plasma and radiation around compact objects. The goal of this work is to speed up radiative-transfer simulations used to create mock images of black holes for comparison with the EHT observations. A ray-tracing code for general relativistic and fully polarized radiative transfer through plasma in strong gravity is ported onto a graphics processing unit (GPU). We describe our GPU implementation and carry out speedup tests using models of optically thin advection-dominated accretion flow (ADAF) onto a black hole realised semi-analytically and in 3D general relativistic magnetohydrodynamics simulations, low and very high image pixel resolutions, and two different sets of CPU+GPUs. We show that a GPU with high double precision computing capability can significantly reduce the image production computational time, with a speedup factor of up to approximately 1200. The significant speedup facilitates, e.g., dynamic model fitting to the EHT data, including polarimetric data. The method extension may enable studies of emission from plasma with nonthermal particle distribution functions for which accurate approximate synchrotron emissivities are not available. The significant speedup reduces the carbon footprint of the generation of the EHT image libraries by at least an order of magnitude., 6 pages, 1 table, 2 figures, Accepted to ApJS, after editorial corrections

Full list of authors: Levan, A. J.; Lamb, G. P.; Schneider, B.; Hjorth, J.; Zafar, T.; de Ugarte Postigo, A.; Sargent, B.; Mullally, S. E.; Izzo, L.; D'Avanzo, P.; Burns, E.; Fernandez, J. F. Aguei; Barclay, T.; Bernardini, M. G.; Bhirombhakdi, K.; Bremer, M.; Brivio, R.; Campana, S.; Chrimes, A. A.; D'Elia, V.; Valle, M. Della; De Pasquale, M.; Ferro, M.; Fong, W.; Fruchter, A. S.; Fynbo, J. P. U.; Gaspari, N.; Gompertz, B. P.; Hartmann, D. H.; Hedges, C. L.; Heintz, K. E.; Hotokezaka, K.; Jakobsson, P.; Kann, D. A.; Kennea, J. A.; Laskar, T.; Le Floc'h, E.; Malesani, D. B.; Melandri, A.; Metzger, B. D.; Oates, S. R.; Pian, E.; Piranomonte, S.; Pugliese, G.; Racusin, J. L.; Rastinejad, J. C.; Ravasio, M. E.; Rossi, A.; Saccardi, A.; Salvaterra, R.; Sbarufatti, B.; Starling, R. L. C.; Tanvir, N. R.; Thoene, C. C.; van der Horst, A. J.; Vergani, S. D.; Watson, D.; Wiersema, K.; Wijers, R. A. M. J.; Xu, Dong.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., We present James Webb Space Telescope (JWST) and Hubble Space Telescope (HST) observations of the afterglow of GRB 221009A, the brightest gamma-ray burst (GRB) ever observed. This includes the first mid-IR spectra of any GRB, obtained with JWST/Near Infrared Spectrograph (0.6–5.5 micron) and Mid-Infrared Instrument (5–12 micron), 12 days after the burst. Assuming that the intrinsic spectral slope is a single power law, with Fν ∝ ν−β, we obtain β ≈ 0.35, modified by substantial dust extinction with AV = 4.9. This suggests extinction above the notional Galactic value, possibly due to patchy extinction within the Milky Way or dust in the GRB host galaxy. It further implies that the X-ray and optical/IR regimes are not on the same segment of the synchrotron spectrum of the afterglow. If the cooling break lies between the X-ray and optical/IR, then the temporal decay rates would only match a post-jet-break model, with electron index p < 2, and with the jet expanding into a uniform ISM medium. The shape of the JWST spectrum is near-identical in the optical/near-IR to X-SHOOTER spectroscopy obtained at 0.5 days and to later time observations with HST. The lack of spectral evolution suggests that any accompanying supernova (SN) is either substantially fainter or bluer than SN 1998bw, the proto-type GRB-SN. Our HST observations also reveal a disk-like host galaxy, viewed close to edge-on, that further complicates the isolation of any SN component. The host galaxy appears rather typical among long-GRB hosts and suggests that the extreme properties of GRB 221009A are not directly tied to its galaxy-scale environment. © 2023. The Author(s). Published by the American Astronomical Society., A.J.L., D.B.M., and N.R.T. are supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 725246). G.P.L. is supported by a Royal Society Dorothy Hodgkin Fellowship (grant Nos. DHF-R1-221175 and DHF-ERE-221005). J.H. and L.I. were supported by a VILLUM FONDEN Investigator grant to JH (project No. 16599). B.D.M. acknowledges support from the National Science Foundation (grant No. AST-2002577). J.P.U.F. acknowledges support from the Carlsberg Foundation. The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant No. 140. D.A.K. acknowledges the support by the State of Hessen within the Research Cluster ELEMENTS (Project ID 500/10.006). R.B., M.G.B., S.C., P.D.A., M.F., A.M., and S.P. acknowledge funding from the Italian Space Agency, contract ASI/INAF No. I/004/11/4. P.D.A. acknowledges support from PRIN-MIUR 2017 (grant 20179ZF5KS). J.F.A.F. acknowledges support from the Spanish Ministerio de Ciencia, Innovación y Universidades through the grant PRE2018-086507., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

We use the surface detector of the Pierre Auger Observatory to search for air showers initiated by photons with an energy above 1019 eV. Photons in the zenith angle range from 30∘ to 60∘ can be identified in the overwhelming background of showers initiated by charged cosmic rays through the broader time structure of the signals induced in the water-Cherenkov detectors of the array and the steeper lateral distribution of shower particles reaching ground. Applying the search method to data collected between January 2004 and June 2020, upper limits at 95% CL are set to an E-2 diffuse flux of ultra-high energy photons above 1019 eV, 2 × 1019 eV and 4 × 1019 eV amounting to 2.11 × 10-3, 3.12 × 10-4 and 1.72 × 10-4 km-2 sr-1 yr-1, respectively. While the sensitivity of the present search around 2 × 1019 eV approaches expectations of cosmogenic photon fluxes in the case of a pure-proton composition, it is one order of magnitude above those from more realistic mixed-composition models. The inferred limits have also implications for the search of super-heavy dark matter that are discussed and illustrated.

Colour-magnitude diagrams reveal a population of blue (hot) sub-luminous objects with respect to the main sequence. These hot sub-luminous stars are the result of evolutionary processes that require stars to expel their obscuring, hydrogen-rich envelopes to reveal the hot helium core. As such, these objects offer a direct window into the hearts of stars that are otherwise inaccessible to direct observation. We showcase MeerLICHT's capabilities of detecting faint hot subdwarfs and identifying the dominant frequency in the photometric variability of these compact hot stars, in comparison to their $Gaia$ DR3 data. We hunt for oscillations, which will be an essential ingredient for accurately probing stellar interiors in future asteroseismology. Comparative MeerLICHT and $Gaia$ colour-magnitude diagrams are presented as a way to select hot subdwarfs from our sample. A dedicated frequency determination technique is developed and applied to the selected candidates to determine their dominant variability using time-series data from MeerLICHT and $Gaia$ DR3. We explore the power of both datasets in determining the dominant frequency. Using the $g-i$ colour, MeerLICHT offers a colour-magnitude diagram that is comparable in quality to that of $Gaia$ DR3. The MeerLICHT colour-colour diagrams allow for the study of different stellar populations. The frequency analysis of MeerLICHT and $Gaia$ DR3 data demonstrates the superiority of our MeerLICHT multi-colour photometry in estimating the dominant frequency compared to the sparse $Gaia$ DR3 data. MeerLICHT's multi-band photometry leads to the discovery of high-frequency faint subdwarfs. Our MeerLICHT results are a proof-of-concept of the capacity of the BlackGEM instrument currently in the commissioning stage at ESO's La Silla Observatory in Chile., Accepted from A&A journal. Publication is still in process

Herbig Ae/Be stars are young contracting stars on the radiative track in the HR diagram on their way to the main sequence. These stars provide a valuable link between high and low mass stars. Here we review the progress that has been made in our understanding of these fascinating objects and their disks since the last major review on this topic published in 1998. We begin with a general overview of these stars and their properties. We then discuss the accretion of circumstellar material onto these stars. Next we discuss the dust and gas properties of the circumstellar disk before exploring the evidence for planet formation in these disks. We conclude with a brief discussion of future prospects for deepening our understanding of these sources and propose a new working definition of Herbig Ae/Be stars., 83 pages, 29 figures, to be published in Space Science Reviews

Aims. Through the ATOMIUM project, based on an ALMA large program, we aim to present a consistent view of a sample of 17 nearby cool evolved stars (Aymptotic Giant Branch and red supergiant stars). Methods. Here we present VLT/SPHERE-ZIMPOL polarimetric maps obtained in the visible of 14 out of the 17 ATOMIUM sources. They were obtained contemporaneously with the ALMA high spatial resolution data. To help interpret the polarized signal, we produced synthetic maps of light scattering by dust, through 3D radiative transfer simulations with the RADMC3D code. Results. The degree of linear polarization (DoLP) observed by ZIMPOL spreads across several optical filters. We infer that it primarily probes dust located just outside of the point spread function, and in or near the plane of the sky, with a total optical depth close to unity in the line of sight, representing only a fraction of the total circumstellar dust. The maximum DoLP ranges from 0.03-0.38 depending on the source, fractions that can be reproduced by our 3D pilot models for grains composed of common dust species. The spatial structure of the DoLP shows a diverse set of shapes. Only for three sources do we note a correlation between the ALMA CO and SiO lines, which trace the gas density, and the DoLP, which traces the dust. Conclusion. The clumpiness of the DoLP and the lack of a consistent correlation between the gas and the dust location show that, in the inner circumstellar environment (CSE), dust formation occurs at very specific sites. This has potential consequences for the derived mass-loss rates and dust-to-gas ratio in the inner region of the CSE. Except for $\pi^1$~Gru and perhaps GY Aql, we do not detect interactions between the circumstellar wind and the hypothesized companions that shape the wind at larger scales. This suggests that the orbits of any other companions are tilted out of the plane of the sky., Comment: Accepted for publication in Astronomy & Astrophysics. 22 pages, 15 figures, 5 tables

Luminous red novae (LRNe) are transients characterized by low luminosities and expansion velocities, and are associated with mergers or common envelope ejections in stellar binaries. Intermediate-luminosity red transients (ILRTs) are an observationally similar class with unknown origins, but generally believed to either be electron capture supernovae (ECSN) in super-AGB stars, or outbursts in dusty luminous blue variables (LBVs). In this paper, we present a systematic sample of 8 LRNe and 8 ILRTs detected as part of the Census of the Local Universe (CLU) experiment on the Zwicky Transient Facility (ZTF). The CLU experiment spectroscopically classifies ZTF transients associated with nearby ($, 32 pages, 16 figures. Submitted to ApJ, comments welcome

A star tidally disrupted by a black hole can form an accretion disc with a super-Eddington mass accretion rate; the X-ray emission produced by the inner disc provides constraints on the black hole mass $M_\bullet$ and dimensionless spin parameter $a_\bullet$. Previous studies have suggested that the $M_\bullet$ responsible for the tidal disruption event 3XMM J150052.0+015452 (hereafter J150052) is $\sim$10$^{5} M_{\odot}$, in the intermediate black hole (IMBH) regime. Fitting multi-epoch XMM-Newton and Chandra X-ray spectra obtained after 2008 during the source's decade-long decay, with our latest slim accretion disc model gives $M_\bullet = 2.0^{+1.0}_{-0.3}\times10^{5} M_{\odot}$ (at 68% confidence) and $a_\bullet > 0.97$ (a 84.1% confidence lower limit). The spectra obtained between 2008-2014 are significantly harder than those after 2014, an evolution that can be well explained by including the effects of inverse-Comptonisation by a corona on the early-time spectra. The corona is present when the source accretion rate is super-Eddington, while there is no evidence for its effect in data obtained after 2014, when the mass accretion rate is around the Eddington-limit. Based on our spectral study, we infer that the corona is optically thick and warm ($kT_e=2.3^{+2.7}_{-0.8}$ keV). Our mass and spin measurements of J150052 confirm it as an IMBH and point to a rapid, near extremal, spin. These $M_\bullet$ and $a_\bullet$ values rule out both vector bosons and axions of masses $\sim10^{-16}$ eV., 11 pages, 6 figures. Accepted for publication in MNRAS

El presente estudio consiste en el análisis textual y comentario del proceso traductor de tres textos franceses de divulgación científica sobre astronomía del siglo XIX: Exposition du système du mondede Pierre-Simon Laplace, Sur la planète Neptunede Urbain Le Verrier y Astronomie populairede Camille Flammarion. Nuestro objetivo es analizar y resolver las dificultades que plantean los textos científico-técnicos e históricos, para aportar una traducción correcta desde el punto de vista terminológico, lingüístico y pragmático. Debido a la extensión de los originales, hemos realizado una selección de fragmentos de distinta temática, aunque la astronomía es el tema central de todo el conjunto. Nuestra metodología de trabajo parte con un planteamiento teórico en el que se exponen las características y dificultades de las tipologías textuales, además de un breve recorrido por la divulgación científica sobre astronomía en la Francia del siglo XIX. La segunda parte del estudio es el análisis textual y la justificación razonada de algunas de las decisiones traductológicas de nuestra propuesta. This study consists of the text analysis and the commentary in the translation process of three scientific dissemination texts about astronomy written by French astronomers from the 19th century: Exposition du système du monde, by Pierre-Simon Laplace, Sur la planète Neptune, by Urbain Le Verrier, and Astronomie populaire, by Camille Flammarion. Our aim is to analyse and solve the difficulties that scientific, technical and historical textsposes and to produce a correct translation from the terminological, linguistic and pragmatic point of view. Due to the extension of the originals, we have chosen a series of extracts about different subjects, although astronomy is the base of the whole work. Our methodology begins with a theoretical approach about the main characteristics and difficulties of textual typologies. The second part is the text analysis; we also justify some of the translation decisions that we made in our proposal.

International audience; The Anthropocene was conceptualized in 2000 to reflect the extensive impact of human activities on our planet, and subsequent detailed analyses have revealed a substantial Earth System response to these impacts beginning in the mid-20 th century. Key to this understanding was the discovery of a sharp upturn in a multitude of global socioeconomic indicators and Earth System trends at that time; a phenomenon termed the 'Great Acceleration'. It coincides with massive increases in global human-consumed energy and shows the Earth System now on a trajectory far exceeding the earlier variability of the Holocene Epoch, and in some respects the entire Quaternary Period. The evaluation of geological signals similarly shows the mid-20 th century as representing the most appropriate inception for the Anthropocene. A recent mathematical analysis has nonetheless challenged the significance of the original Great Acceleration data. We examine this analytical approach and reiterate the robustness of the original data in supporting the Great Acceleration, while emphasizing that intervals of rapid growth are inevitably time-limited, as recognised at the outset. Moreover, the exceptional magnitude of this growth remains undeniable, reaffirming the centrality of the Great Acceleration in justifying a formal chronostratigraphic Anthropocene at the rank of series/epoch.

Studi var an astrou (Brest, Lefournier, 1848) est probablement le premier texte scientifique en langue bretonne. Publier un traité d’astronomie pour instruire la population bretonnante, au milieu d’un 19e siècle littéraire marqué par le bretonisme et le néo-bardisme, relève d’une démarche rare qui se distingue fortement des motivations singularisantes et identitaires qui prévaut alors. De plus, le fait que l’ouvrage et son auteur, Paul Lebreton, soient tous deux inconnus du panorama des publications en breton pousse à saisir qui était cette plume. Enfin, autre point surprenant : cet ouvrage a été découvert par l’intermédiaire du manuscrit autobiographique d’un paysan, Julien Godest. Cet article allie donc une étude en archives, une étude de la langue d’écriture (dialectologie et sociolinguistique) et une étude du contenu de ce texte, et propose l’hypothèse d’un texte émanant du milieu protestant morlaisien et d’une plume à deux mains : Guillaume Lejean et Guillaume Ricou. Studi var an astrou (Brest, Lefournier, 1848) is probably the first scientific text in Breton. Publishing an astronomical treatise to educate the Breton population, in the middle of a 19th century literary marked by Bretonism and neo-Bardism, is a rare approach that differs strongly from the singularizing and identity motivations that prevailed at the time. In addition, the fact that the book and its author, Paul Lebreton, are both unknown to the panorama of publications in Breton leads us to identify who this writer was. Finally, another surprising point: this work was discovered through the autobiographical manuscript of a peasant, Julien Godest. This article therefore combines a study in archives, a study of the language of writing (dialectology and sociolinguistics) and a study of the content of this text, and proposes the hypothesis of a text emanating from the Morlaisian Protestant milieu and a pen in two hands: Guillaume Lejean and Guillaume Ricou.

Recently, NASA scientists and administrators have proposed a numerical scale for quantifying the Confidence of Life Detection – the CoLD scale [1]. Although the stated goal is to minimize damaging public trust with premature or overly-confident claims of detecting life beyond Earth, the CoLD scale is an inapt and easily abused tool that will do little to address the misleading terminology and sensational narratives that plague both public and scientific communications from the astrobiology community. By failing to acknowledge, much less address, the root cause(s) of these communication problems, the CoLD scale can only address the symptoms while allowing the underlying disease to progress. That the arrival of misleading claims could be confidently anticipated by the developers of the CoLD scale is itself a measure of the strength of the disease. The root cause(s) run deep and engcannot be cured with a numerical scale.

The nature of the relation between active galactic nuclei (AGN), and their host galaxies have been observed in detail throughout the Universe. Such work has found an intrinsic link between central supermassive black hole (SMBH) masses, and host galaxy properties such as the velocity dispersion of stars, and bulge mass. However, the difference in scale between SMBH and their host galaxies has led to debate on how this relation might form, and develop over time. In order to aid in understanding the relation between AGN and their host galaxies, the work throughout this thesis has therefore focused on the development and implementation of a new SED fitting code, using an up-to-date AGN SED to accurately infer both AGN and host galaxy properties. To this end, we explore the intricacies involved in producing useful property inferences using a Bayesian MCMC fitting method, whilst working to avoid common issues such as bimodality and lack of convergence. We then perform SED fitting using our methods to 711 luminous X-ray AGN at 0.7 < z < 4.5 using 10-bands of optical and infra-red photometric data for objects within XMMSERVS. Using these fits, we study the relation between AGN X-ray luminosity and host galaxy stellar mass, along with our ability to predict emission line strength and morphology from photometry alone. In order to further understand the intricacies of SED fitting, we also provide a case study into the effect of AGN SED choice on host galaxy and AGN property inferences, by comparing our AGN SED to another commonly used template. In this work, we show that it is important to consider host galaxy contamination when trying to produce a pure AGN template, and the effect that this contamination can have on AGN and host galaxy property inferences. We also find that the use of lower resolution SEDs can lead to repercussions on property inferences such as host galaxy stellar mass, which may provide incorrect assumptions on the relation between AGN and their host galaxies.

The William J. McCallion Planetarium at McMaster University, Hamilton, Canada (established 1949), is pleased to share details of the first year of outreach initiatives and statistics from its new small (6m diameter) portable planetarium. The portable planetarium, purchased with funding from the Faculty of Science, was launched in June 2022, and has the primary goal of extending astronomy-based education and outreach initiatives to underserved and underrepresented communities off campus (to supplement the fixed planetarium on campus). The portable planetarium has also allowed us to continue our reconciliation efforts and astronomy collaborations with local Indigenous communities, resulting in the co-creation of one show and further shows in development. This presentation will highlight the co-creation process, successes and challenges we have experienced during our first months of operation, and will welcome conversations from communities we may be able to visit and/or from other institutes who currently have or are seeking to set up similar programs.

Understanding stellar evolution is fundamental to astronomy, yet there remain significant gaps in our knowledge. Scientific progress requires testing our best explanations against observation, and open clusters act as key test sites for theories of stellar evolution. Observations of young open clusters enable theoretical models to be assessed at stages when stellar properties still reflect their initial conditions, and in regions of parameter space where constraints remain scarce. The Next Generation Transit Survey (NGTS) is a multi-telescope, ground-based, wide-field photometric survey which is well-suited to studying these environments, and its observations are at the heart of this thesis, which presents my research in the field of early-stage stellar evolution as conducted during my PhD. As a member of the NGTS consortium and, specifically, of the team focusing on open clusters and star forming regions, I have used NGTS data to analyse stellar rotation in the Orion Star-forming Complex and to characterise a low-mass eclipsing binary (EB) in a triple-star system located in the Blanco 1 open cluster. By combining NGTS observations with additional photometry and spectroscopy, and by developing a novel method for extracting radial velocities of close binary (or higher-order) systems, I derived the fundamental parameters of the Blanco 1 EB. With masses and radii measured to a precision better than 1 and 2 per cent, respectively, the newly-identified EB, NGTS J0002-29, becomes a benchmark addition to the current list of 19 well-characterised, low-mass, sub-Gyr, stellar-mass EBs, which constitute some of the strongest observational tests of stellar evolution theory at low masses and young ages. Long-baseline observations of 30 square degrees of the Orion Complex provided simultaneous photometry of thousands of stars, leading to my study of stellar rotation. I analysed cluster membership using astrometry from Gaia DR3 and built a pipeline to process light curves, producing an extensive and homogeneous dataset of more than 2000 rotation periods. I estimated interstellar extinction on a star-by-star basis by fitting broadband photometric data, and derived stellar ages using evolutionary models. I assigned the target stars to kinematic clusters, calculated their ages, and analysed rotation period distributions, finding evidence for mass-dependent evolution during the first 10 Myr, as well as corroboration for the idea that circumstellar discs play a role in regulating the evolution of angular momentum. These studies demonstrate the ability of modern ground-based photometric surveys to address questions about young-age stellar evolution, both on the scale of individual systems and on the scale of large clusters. This ability to operate at different scales facilitates rapid progress and helps to maximise the potential in our data for testing our theories.

The characterisation of exoplanets has made rapid progress in recent years, with observations of bulk properties such as mass and radius combining with detailed atmospheric spectroscopy to provide unprecedented insight into the nature of these remote worlds. However, these high-quality observations also require sophisticated modelling and analysis tools in order to maximise the scientific output from the data. In this thesis I present a number of advances in atmospheric modelling and retrieval, as well as internal structure models, which have been used to investigate the properties of a wide range of planets, from hot Jupiters to temperate mini-Neptunes. I conduct an assessment of the feasibility of supervised machine learning as a tool to carry out atmospheric retrievals of exoplanets. Retrieval methods commonly conduct Bayesian parameter estimation and statistical inference using sampling algorithms such as Markov Chain Monte Carlo or Nested Sampling. Recently several attempts have been made to use machine learning algorithms either to complement or replace fully Bayesian methods in order to improve computational efficiency. However, results from these algorithms sometimes disagree with contemporary Bayesian retrievals. To investigate this, I use the Random Forest supervised machine learning algorithm which has been applied previously for atmospheric retrieval. I extend the machine learning approach to develop a new algorithm, and demonstrate excellent agreement with a Bayesian retrieval of the transmission spectrum of the hot Jupiter HD~209458b. Despite this success, and achieving high computational efficiency, I still find that this machine learning approach is computationally prohibitive for high-dimensional parameter spaces that are routinely explored with Bayesian retrievals with modest computational resources. I discuss the trade offs and potential avenues for the future. I present \textsc{Aura-3D}, a three-dimensional atmospheric retrieval framework for exoplanet transmission spectra. \textsc{Aura-3D} includes a forward model that enables rapid computation of transmission spectra in 3D geometry for a given atmospheric structure and can, therefore, be used for atmospheric retrievals as well as for computing spectra from General Circulation Models (GCMs). In order to efficiently explore the space of possible 3D temperature structures in retrievals, I develop a parametric 3D pressure-temperature profile which can accurately represent azimuthally-averaged temperature structures of a range of hot Jupiter GCMs. I apply this retrieval framework to simulated JWST observations of hot Jupiter transmission spectra, obtaining accurate estimates of the day-night temperature variation across the terminator as well as the abundances of chemical species. I demonstrate an example of a model hot Jupiter transmission spectrum for which a traditional 1D retrieval of JWST-quality data returns biased abundance estimates, whereas a retrieval including a day-night temperature gradient can accurately retrieve the true abundances. The forward model also has the capability to include inhomogeneous chemistry as well as variable clouds/hazes. This new retrieval framework opens the field to detailed multidimensional atmospheric characterisation using transmission spectra of exoplanets in the JWST era. I also present a new internal structure model for super-Earths and mini-Neptunes that enables detailed characterisation of a planet's water component. I use my model to determine how the bulk properties and surface conditions of a water world affect its ocean depth, finding that oceans can be up to hundreds of times deeper than on Earth. I explore the region of mass--radius space in which planets with H-rich envelopes could host liquid H$_2$O. Such envelopes could contribute significantly to the planet radius while retaining liquid water at the surface, highlighting the exciting potential for habitable conditions to be present on planets much larger than Earth. I contribute to internal structure models of a number of sub-Neptunes whose atmospheres are set to be observed using JWST. Before such observations take place, it is vitally important to understand the interior structures of these planets, which strongly affects their possible atmospheric compositions. We use the bulk parameters and retrieved atmospheric properties to constrain the internal structure and thermodynamic conditions in the habitable-zone mini-Neptune K2-18b, for which I contribute the H$_2$O EOS. The constraints on the interior allow multiple scenarios between rocky worlds with massive H/He envelopes and water worlds with thin envelopes. We constrain the mass fraction of the H/He envelope to be $\lesssim$6\%; spanning $\lesssim$10$^{-5}$ for a predominantly water world to $\sim$6\% for a pure iron interior. The thermodynamic conditions at the surface of the H$_2$O layer range from the supercritical to liquid phases, with a range of solutions allowing for habitable conditions. We also investigate the possible compositions of the pair of planets orbiting the star TOI-776. The bulk densities of TOI-776b and c allow for a wide range of possible interior and atmospheric compositions. However, the models indicate that both planets must have retained a significant atmosphere. Upcoming observations will revolutionise our understanding of these planets, helping to uncover the mysteries of the sub-Neptune population. Finally, I discuss the latest developments in exoplanet observations, and consider how these advances may further our understanding of worlds beyond our own.

This thesis concerns the use of data from the Gaia satellite to study Galactic planetary nebulae. Gaia is a recent ESA mission measuring positions, parallaxes, proper motions, and photometry of nearly two billion stars in the Milky Way. Several thousand of these stars are passing through the planetary nebula phase, an important phase that low and intermediate mass stars experience towards the ends of their lives before becoming white dwarfs. The thesis has three main contributions. The first is the development and application of an automated technique for identifying the central stars of planetary nebulae in the Gaia catalogue. The second is a statistical method for identifying photometric variability in these central stars. Periodic photometric variability is often an indicator of binarity, which is now known to be key to the formation and shaping of a significant fraction of planetary nebulae. The method is validated through ground-based follow up observations. Finally, more precise distances from Gaia parallaxes are combined with newly obtained ground-based narrowband imagery to determine and investigate the planetary nebula luminosity function of the local Milky Way. Besides being an important extragalactic indicator, this distribution of nebula magnitudes is related to the evolution of planetary nebula central stars across different masses. Distances and photometry from Gaia allow the brightness of the nebula and the evolution of the central star to be related directly in unprecedented detail.

Most existing space solar power concepts place one or more power stations in geosynchronous Earth orbit (GEO). However, due to the limited availability of GEO orbital slots, it may not be feasible to locate a power station in GEO. To overcome this limitation, this paper presents a system analysis for a space solar power system that incorporates a constellation of power stations in a 20,184 km altitude equatorial medium Earth orbit (MEO). The orbiting power stations are based on the Caltech Space Solar Power Project architecture. The constellation consists of multiple power stations in a shared equatorial MEO each transmitting to a non-equatorial receiving station. The analysis assumes a one-to-one correspondence between the number of power stations and the number of ground stations. Like a GEO-based system, this constellation architecture enables a MEO-based system to provide near continuous power (outside of eclipse) to each ground station. It is shown that a MEO constellation with three or more power stations provides comparable transmission efficiency to a GEO-based system. The Levelized Cost of Electricity (LCOE) is then computed for MEO systems with three, four, and five power stations and compared to the LCOE for the GEO-based system. Ground station area is identified as a significant contributor to the LCOE for the MEO-based systems. The system analysis shows that a MEO constellation with as few as four power stations has an LCOE comparable to GEO, and hence, it is concluded that MEO is a viable alternative to GEO for space solar power.

Resumen El artículo analiza el rol que jugó el Observatorio Astronómico Nacional en la expansión territorial de Chile a fines del siglo XIX, a través de la relación que sostuvo con tres exploraciones geográficas asociadas a este proceso. Se propone que el Observatorio cumplió un papel central para estas exploraciones geográficas, ayudando a obtener coordenadas geográficas precisas en pos de producir mapas exactos de los territorios anexados al norte y sur de Chile. Los resultados permiten afirmar que el Observatorio Astronómico Nacional fue una institución que prestó servicios estratégicos durante la expansión territorial y, a su vez, que la geografía fue parte importante de sus trabajos científicos institucionales. Abstract The article analyzes the role played by the National Astronomical Observatory (Observatorio Astronómico Nacional) in the territorial expansion of Chile at the end of the nineteenth century, through the relationship with three geographical explorations associated with this process. It is proposed that the Observatory played a central role in these geographic explorations, helping to obtain precise geographic coordinates to produce accurate maps of the territories annexed to the north and south of Chile. The results allow us to affirm that the National Astronomical Observatory provided strategic services during territorial expansion, and geography was an important part of its institutional scientific work.

Dawn conducted an extensive exploration of dwarf planet Ceres, the largest object between the Sun and Pluto that had not previously been visited by a spacecraft. Following its arrival at Ceres in March 2015, Dawn acquired all the planned data from four circular polar orbits ranging in altitude from 13,600 km to 385 km. After the successful conclusion of the prime mission in June 2016, Dawn's mission was extended, and new investigations, not previously considered, were conducted from four new orbits ranging as low as 35 km. In 2017 the project was approved for a second and final extended mission at Ceres. Starting in April 2018, Dawn used its ion propulsion system to maneuver to two new orbits. These highly elliptical orbits enabled the acquisition of valuable new data, including significant improvements in the spatial resolution. Mission operations concluded in October 2018 upon depletion of hydrazine for attitude control. The mission provided a uniquely detailed view of the first dwarf planet discovered. This paper describes Ceres operations as well as some of the major findings there.

The problem of space flights safety arose with the beginning of the first launches of artificial Earth satellites. With expansion of the boundaries of space flights, the area of outer space that must be controlled to ensure flight safety is significantly increasing. In this study, we consider the possibility of capturing space objects into near-planetary space and further movement of these objects. Such statistical analysis is very important when planning the long-term flights. The objects of our research are both: the particles that came from deep space and the evolving asteroids of the Main asteroid belt. A special attention is paid to the evolution of the Griqua family of asteroids, which belong to the main asteroid belt, and move in orbital resonance with Jupiter.

W. G. Colgrove dedicated years of his life to the community of Western University and the city of London through his work with the Hume Cronyn Memorial Observatory and the Royal Astronomical Society of Canada. This story map walks readers through the life of W. G. Colgrove and his autobiographical scrapbook, A Place in the Sun. https://ir.lib.uwo.ca/colgrovestorymap/1000/thumbnail.jpg

The world faces a massive gender gap in science. In Ethiopia, only ~ 13% of all scientists are women, and this number becomes even lower when considering fundamental sciences. In addition, if able to continue with their studies at the secondary school level, girls avoid choosing science, technology, engineering, and mathematics (STEM) fields mainly due to the lack of support, information, and role models. This becomes even more evident when going to remote and rural areas, where 80% of the Ethiopian population lives. The SciGirls project aims to improve in the long term the gender gap in science and the current lack of girls in STEM by empowering secondary school girls from rural areas and their female science teachers through astronomy and its multidisciplinarity. To do so, we organised a strong capacity-building workshop for 30 participants from different regions of Ethiopia, with an aim to build the future advocates of STEM in rural areas through trained girls and female teachers. The SciGirls is one of the OAD-IAU 2022-funded projects, with the strong support of the Ethiopian Space Science and Geospatial Institute. Through this talk, we will share our experience, and give more details about the project and its future developments. The workshop organised was extremely successful and through our experience, we would like to motivate others to use the SciGirls as a pilot project and model in other countries and areas.&nbsp

In this thesis, we explore the relationship between molecular clouds and star formation in the Magellanic Clouds – two nearby, low-metallicity companion galaxies to the Milky Way. We first examine variations in the behavior of common tracers of molecular gas, and derive physically motivated corrections for observational biases affecting Carbon Monoxide-based metrics of molecular cloud properties in low-metallicity environments. We then study molecular cloud dynamics and the progression of star formation in the young Small Magellanic Cloud star-forming region NGC 602. Finally, we explore machine-learning based techniques to identify pre-main-sequence stars in the active star-forming region N159 in the Large Magellanic Cloud.

MICADO [1] is the Multi-AO Imaging Camera for Deep Observations and it is one of the first light instruments of the ESO Extremely Large Telescope [2, 3] (E-ELT), providing imaging and long-slit spectroscopy at near-infrared wavelengths. It will exploit single conjugate adaptive optics [4] (SCAO) with natural guide star in stand-alone mode since the first light of E-ELT. A multi-conjugate adaptive optics (MCAO) will be also accessible for this instrument with the implementation of the MAORY module [5]. In general, reconstructing the PSF of AO instrumentation is challenging, since it is much more complex than in the traditional seeing-limited case or for space based telescopes. This is even more true for E-ELT. However, a detailed knowledge of the PSF is required to fulfill most of the scientific goals [6]. For this reason, the PSF reconstruction (PSF-R) is a planned deliverable of the MICADO consortium. Our group in particular focuses on the work package in charge of the PSF-R development [7]. The goal is to provide the final user with reconstructed PSFs through an archive querying system restoring the full telemetry data synchronous to each science frame that MICADO will generate. The PSF-R service will support the state-of-the-art scientific analysis of the MICADO imaging and spectroscopic data. The PSF-R method we are currently implementing is described in Wagner et. al (2018) [8]. It consists of an up- date of Veran et al. (1997) [9]: in practice, a telemetry-only PSF-R approach is being pursued. This means that the reconstructed PSFs are obtained independently from focal plane science images. In particular, our PSF-R algorithm makes use of (i) WFS images and telemetry generated by the AO system, (ii) information by other systems monitoring the atmosphere and (iii) telemetry from the E-ELT and MICADO instrument. All these technical data need to be syn- chronous to the science observations for which the reconstructed PSFs have to be obtained. The telemetry-only PSF-R approach allows the flexibility to reconstruct the PSF even in the absence of useful point sources in the science images - a common occurrence in, but not limited to, extragalactic targets [6, 7]. In this presentation it is discussed the status of the MICADO PSF-R deliverable, demonstrating its readiness level by presenting the results of a recent application of the method to real SCAO data taken at Large Binocular Telescope (LBT) with SOUL/LUCI [10]. Archival data, accompanied by the related full telemetry, have been used to test the performances of our PSF-R algorithm. The reconstructed PSFs reproduce the observed ones with an accuracy better than 2% in Strehl ratio and 5% in full width at half maximum. It is also presented the results of the scientific evaluation of these reconstructed PSFs for a simulated, typical extragalactic case. References 1. Davies, R., Ageorges, N., Barl, L., et al. 2010, SPIE Conference Series, 7735, 77352A. doi:10.1117/12.856379 2. Gilmozzi, R. & Spyromilio, J. 2007, The Messenger, 127, 11 3. Gilmozzi, R. & Spyromilio, J. 2008, SPIE Conference Series, 7012, 701219. doi:10.1117/12.790801 4. Clenet, Y., Esposito, S., Buey, T., et al. 2015, Adaptive Optics for Extremely Large Telescopes IV (AO4ELT4), E42 5. Diolaiti, E. 2010, The Messenger, 140, 28 6. Davies, R. 2019, ’An Astrophysical Context for PSF Reconstruction’, ESO technical report 7. Simioni, M., Arcidiacono, C., Grazian, A., et al. 2020, SPIE Conference Series, 11448, 1144837. doi:10.1117/12.2561251 8. Wagner, R., Hofer, C., & Ramlau, R. 2018, Journal of Astronomical Telescopes, Instruments, and Systems, 4, 049003. doi:10.1117/1.JATIS.4.4.049003 9. Veran, J.-P., Rigaut, F., Maitre, H., et al. 1997, Journal of the Optical Society of America A, 14, 3057. doi:10.1364/JOSAA.14.003057 10. Pinna, E., Esposito, S., Hinz, P., et al. 2016, SPIE Conference Series, 9909, 99093V. doi:10.1117/12.2234444

Over 5000 exoplanets have been discovered in the last three decades, revealing a truly diverse population of worlds beyond our solar system. The field has accelerated rapidly towards characterising the atmospheres of exoplanets around the nearest and brightest stars with large observational surveys from ground-based and space-based instruments. This thesis contains an overview of state-of-the-art methods for detecting chemical species in the atmospheres of transiting exoplanets. In the first chapter, I briefly review the history, key insights, and modern techniques for detecting exoplanets and studying their atmospheres. The subsequent chapters are each based on specific aspects of the analysis of high-resolution transmission spectra in optical wavelengths, aimed towards answering key questions regarding detrending techniques and the atmospheric properties of highly irradiated giant exoplanets. I begin by assessing the robustness of telluric correction methods for removing contaminating telluric water and oxygen lines from high-resolution spectra. This is a challenging and critical task when observing from the ground since absorption from Earth’s atmosphere often overwhelms the exoplanetary signals by several orders of magnitude. I compare the performance of corrections made using a telluric spectrum derived empirically from airmass and using a model of Earth’s transmission spectrum, focusing specifically on sodium detections in the transmission spectrum of a hot Jupiter. Next, I explore the diversity of ten highly irradiated giant exoplanets with equilibrium temperatures ranging from around 1000 to 4000 K. I conduct a homogeneous survey of sodium absorption using high-resolution transmission spectra extracted from observations made with the HARPS and HARPS-N spectrographs. Using sodium as a tracer, I report uniformly measured atmospheric properties across the sample, including atmospheric heights, net day-night wind speeds, and sodium doublet line ratios. I report a new detection of sodium in one of the planets and confirm previously reported detections in the others. I also discuss how different assumptions and detrending processes can cause discrepancies in the measured absorption features, highlighting the importance of a homogeneous analysis when comparing results across multiple planets. I then use these results to perform a search for new global trends on planetary atmospheric properties, with the goal of understanding how the characteristics of the atmospheres change over a diverse sample of planets. I investigate how the homogeneously measured atmospheric heights (as probed by detections of sodium) vary with macroscopic planetary properties, revealing an empirical relationship describing the relative atmospheric heights as a function of planetary equilibrium temperature and surface gravity. I also use the sodium detections to measure net atmospheric wind velocities for all ten planets and discuss how these results can provide information about common underlying processes and dynamics. Finally, I investigate signatures of other atomic species in optical high-resolution transmission spectra of two ultra-hot Jupiters using the cross-correlation technique. In particular, I search for prominent metallic species that are expected to be present due to the extreme temperatures of these exotic atmospheres. I compare the atmospheric heights derived from high-significance detections of neutral iron between the two targets. I also discuss tentative inferences of asymmetric iron absorption features, where the signals from the atmosphere become progressively more blueshifted in the first half of the transit up to a constant value. This asymmetry is indicative of different atmospheric structure or chemistry between the morning and evening terminators. I conclude with final remarks on promising avenues for future research over the course of the next decade, where high-resolution spectroscopy will play a pivotal role in furthering our understanding about the atmospheric properties and processes of the diverse population of exoplanets., Science and Technology Facilities Council (STFC)

In this paper, we present the results of the second census of pulsars in the decametre wave range at the Ukrainian T-shaped Radio telescope, second modification (UTR-2). Over the past 10 yr, the worldwide number of discovered nearby pulsars has doubled, which means that there is some urgency to search for a low-frequency radio emission from these newly discovered sources. To increase the sensitivity of this census, the integration time was doubled compared with the first census of 2010–2013. As a result, the decametre radio emission of 20 pulsars was detected, and their flux densities and the shape of their pulses were obtained. The dispersion measures for 10 pulsars and the rotation periods for eight pulsars were refined. For several pulsars, the scattering time constant and FWHM were estimated in the decametre wave range. The upper limits of flux densities for 102 pulsars that have not yet been detected were also estimated.

In the 1760s, the international debate on the solution to determining longitude at sea is at its acme. Two solutions emerge, the mechanical and the astronomical ones. The Portuguese mathematician and astronomer José Monteiro da Rocha (1734-1819) is well aware of that debate. For him, Harrison's No. 4 marine timekeeper cannot be seen as a solution. The desirable solution could only be astronomical. In a manuscript from c. 1765, which unfortunately he fails to publish, Monteiro da Rocha is very critical of Lacaille's lunar-distance method (1759) and proposes another one. In this paper, we intend to analyse Monteiro da Rocha's criticisms and proposals, trying to understand how this manuscript fits into the international longitude debate and the Portuguese scientific scenario at the time. Concurrently, we will re-examine the classical historiography around the English vs. French priority proposal of the lunar-distance method, purging it from its mythologies to shift it towards a more open, less linear history.

Most massive galaxies contain a supermassive black hole (SMBH) at their center. When galaxies merge, their SMBHs sink to the center of the new galaxy where they are thought to eventually merge. During this process an SMBH binary is formed. The presence of two sets of broad emission lines in the optical spectrum of an active galactic nucleus (AGN) has been interpreted as evidence for two broad line regions (BLR), one surrounding each SMBH in a binary. We modeled the broad Balmer emission lines in SDSS spectra of 373 extreme variability AGNs using one broad and several narrow Gaussian components. We report on the discovery of SDSS J021647.53$-$011341.5 (hereafter J0216) as a double-peaked broad emission line source. Among the 373 AGNs there were five sources that are known double-peaked emission line sources. Three of these have been reported as candidate SMBH binaries in previous studies. We present all six objects and their double-peaked broad Balmer emission lines, and discuss the implications for a tidal disruption event (TDE) interpretation of the extreme variability assuming the double-peaked sources are SMBH binaries., 6 pages, 1 figure, 1 table. Accepted for publication in MNRAS

Fragmentations in space due to explosion or collision spawn multifarious Debris particles in space that exponentially populate the space environment and pose a threat to space activities. Therefore, for pragmatic assessment of space situation and timely dissemination of Space Situational Awareness (SSA) information, fragmentation analysis is of high significance. The Low Earth Orbit (LEO) region is the most crucial area for fragmentation studies as the spatial density is much higher in LEO as compared to the other regions of space. LEO region is also the most suited to analyze fragmentations as more small debris can be tracked compared to higher orbits. The current manuscript therefore embodies a methodology wherein it detects a fragmentation event time, location and identifies the sources for the event.

We present MeqSilhouette v2.0 (MeqSv2), a fully polarimetric, time-and frequency-resolved synthetic data generation software for simulating millimetre (mm) wavelength very long baseline interferometry (VLBI) observations with heterogeneous arrays. Synthetic data are a critical component in understanding real observations, testing calibration and imaging algorithms, and predicting performance metrics of existing or proposed sites. MeqSv2 applies physics-based instrumental and atmospheric signal corruptions constrained by empirically-derived site and station parameters to the data. The new version is capable of applying instrumental polarization effects and various other spectrally-resolved effects using the Radio Interferometry Measurement Equation (RIME) formalism and produces synthetic data compatible with calibration pipelines designed to process real data. We demonstrate the various corruption capabilities of MeqSv2 using different arrays, with a focus on the effect of complex bandpass gains on closure quantities for the EHT at 230 GHz. We validate the frequency-dependent polarization leakage implementation by performing polarization self-calibration of synthetic EHT data using PolSolve. We also note the potential applications for cm-wavelength VLBI array analysis and design and future directions., accepted for publication in MNRAS

Atmospheric mass density (AMD) plays a vital role in the drag calculation for space objects in low Earth orbit (LEO). Many empirical AMD models have been developed and used for orbit prediction and...