Astronomical Community Research Articles

Modification of the Shower Database of the IAU Meteor Data Center

Context. The Shower Database (SD) of the Meteor Data Center (MDC) has been operating for 15 yr and is used by the entire community of meteor astronomers. It contains meteor showers categorised in individual lists on the basis of their status. Since the inception of the SD, no objective rules for moving showers between individual lists have been established. The content of the SD has not yet been checked for the correctness of the meteor data contained therein. Aims. Our aims are (1) to formulate criteria for nominating meteor showers for established status, (2) to improve the rules for the removal of showers, (3) to verify and enhance the content of the SD, and (4) to improve the user area of the MDC SD. Methods. The criteria for moving showers from the Working list to the Lists of established or removed showers were generated using an empirical evaluation of their impact on the registered showers. The correctness of the parameters of each stream included in the SD was checked by comparing them with the values given in the source publications. Results. We developed a set of criteria for nominating showers to be established. We objectified rules for the temporary and permanent removal of meteor showers from the Working list. Both of our proposed new procedures were approved by a vote of the commission F1 of the IAU in July 2022. We verified more than 1350 data records of the MDC SD and introduced ~1700 corrections. We included new parameters for shower characterisation. As a result of our verification procedure, 117 showers have been moved to the List of removed showers. As of October 2022, the SD contains 923 showers, 110 of which are in the List of established showers and 813 are in the Working list. We also improved the user area of the SD and added a simple tool to allow a quick check of the similarity of a new shower to those in the database.

The impact of satellite trails on Hubble Space Telescope observations

The recent launch of low Earth orbit satellite constellations is creating a growing threat for astronomical observations with ground-based telescopes1–10 that has alarmed the astronomical community 11–16. Observations affected by artificial satellites can become unusable for scientific research, wasting a growing fraction of the research budget on costly infrastructures and mitigation efforts. Here we report the first measurements, to our knowledge, of artificial satellite contamination on observations from a low Earth orbit made with the Hubble Space Telescope. With the help of volunteers on a citizen science project (www.asteroidhunter.org) and a deep learning algorithm, we scanned the archive of Hubble Space Telescope images taken between 2002 and 2021. We find that a fraction of 2.7% of the individual exposures with a typical exposure time of 11 minutes are crossed by satellites and that the fraction of satellite trails in the images increases with time. This fraction depends on the size of the field of view, exposure time, filter used and pointing. With the growing number of artificial satellites currently planned, the fraction of Hubble Space Telescope images crossed by satellites will increase in the next decade and will need further close study and monitoring.

Industrial photogrammetry for the optical mechanical truss of the China Survey Space Telescope

The China Survey Space Telescope is the main observation stage of the Chinese space station, and is the most advanced and expensive observation equipment ever constructed in the Chinese astronomical community. The telescope is composed of multi-stage mirrors, whose relative positions determine the observation accuracy of the telescope, and an optical mechanical truss (OMT) forms the mechanical structure that supports them. This paper presents a deformation measurement scheme for the OMT, and introduces a process of deformation measurement and a data processing method for this OMT using industrial photogrammetry technology. The repeatability and accuracy of the industrial photogrammetry system were tested under ambient conditions, and the length measurement data were compared and verified with interferometry measurements.

Bridging astronomical, astrometric and geodetic scheduling for VGOS

Very Long Baseline Interferometry (VLBI) experiments are organized within the geodetic, astrometric and astronomical communities for different applications, requiring different observation strategies adopted in scheduling. Currently, the next-generation geodetic and astrometric VLBI Global Observing System (VGOS) is being established. Over the last years, evidence was presented that the delays introduced by the angular structure of the geodetic radio sources contribute significantly to the VGOS observable error budget. Consequently, correcting these structure delays through imaging will play an important part in the future, requiring a different scheduling approach. Within this work, a new source-centric VLBI scheduling approach is presented for improved imaging capabilities of geodetic observations. The algorithm is tested for a seven- and nine-station network and compared with classical geodetic schedules. Monte Carlo simulations are utilized to determine the expected geodetic and astrometric parameter precision, and two independent processing pipelines are used to assess the potential for astronomical source imaging. Based on the simulation results, it is revealed that with the new scheduling approach twice as many sources can be properly imaged. Furthermore, the precision of the Earth orientation parameter estimates is improved on average by {15}{%}, while the source position coordinate estimates are on average improved by {50}{%}. Tests with two VGOS networks of twelve and 29 antennas further reveal that the scheduling approach is also applicable to future VGOS networks.

Rotational Fingerprints of Vinylketene for Astronomical Observations

A high degree of isomerism in the realm of interstellar molecules stimulates systematic astronomical investigations of members of different families of isomers. Among them, vinyl-bearing compounds have kindled considerable interest due to recent detections of vinylamine, vinylacetylene, and vinylcyanoacetylene. Herein, we open the possibility to search for vinylketene in the interstellar space by means of its rotational transitions. The pure rotational spectrum of the title molecule was recorded in the frequency regions 195–218 and 293–324 GHz and an improved and extended set of spectroscopic parameters has been obtained for the most stable trans conformer. In addition, rotational signatures and molecular constants for the less stable cis form are reported for the first time. We provide a catalog of precise transition frequencies and intensities of vinylketene to the astronomical community and pave the way toward interstellar explorations of C4H4O isomer family.

Cosmic-CoNN: A Cosmic-Ray Detection Deep-learning Framework, Data Set, and Toolkit

Rejecting cosmic rays (CRs) is essential for the scientific interpretation of CCD-captured data, but detecting CRs in single-exposure images has remained challenging. Conventional CR detectors require experimental parameter tuning for different instruments, and recent deep-learning methods only produce instrument-specific models that suffer from performance loss on telescopes not included in the training data. We present Cosmic-CoNN, a generic CR detector deployed for 24 telescopes at the Las Cumbres Observatory, which has been made possible by the three contributions in this work: (1) We build a large and diverse ground-based CR data set leveraging thousands of images from a global telescope network. (2) We propose a novel loss function and a neural network optimized for telescope imaging data to train generic CR-detection models. At 95% recall, our model achieves a precision of 93.70% on Las Cumbres imaging data and maintains a consistent performance on new ground-based instruments never used for training. Specifically, the Cosmic-CoNN model trained on the Las Cumbres CR data set maintains high precisions of 92.03% and 96.69% on Gemini GMOS-N/S 1 × 1 and 2 × 2 binning images, respectively. (3) We build a suite of tools including an interactive CR mask visualization and editing interface, console commands, and Python APIs to make automatic, robust CR detection widely accessible by the community of astronomers. Our data set, open-source code base, and trained models are available at https://github.com/cy-xu/cosmic-conn.

Near-infrared chemical abundances of stars in the Sculptor dwarf galaxy

Owing to the recent identification of major substructures in our Milky Way (MW), the astronomical community has started to reevaluate the importance of dissolved and existing dwarf galaxies. In this work, we investigate up to 13 elements in 43 giant stars of the Sculptor dwarf galaxy (Scl) using high-signal-to-noise-ratio near-infrared (NIR) APOGEE spectra. Thanks to the strong feature lines in the NIR, we were able to determine high-resolution O, Si, and Al abundances for a large group of sample stars for the first time in Scl. By comparing the [α/Fe] (i.e., O, Mg, Si, Ca, and Ti) of the stars in Scl, Sagittarius, and the MW, we confirm the general trend that less massive galaxies tend to show lower [α/Fe]. The low [Al/Fe] (∼ − 0.5) in Scl demonstrates the value of this ratio as a discriminator with which to identify stars born in dwarf galaxies (from MW field stars). A chemical-evolution model suggests that Scl has a top-light initial mass function (IMF), with a high-mass IMF power index of ∼ − 2.7, and a minimum Type Ia supernovae delay time of ∼100 Myr. Furthermore, a linear regression analysis indicates a negative radial metallicity gradient and positive radial gradients for [Mg/Fe] and [Ca/Fe], in qualitative agreement with the outside-in formation scenario.

The Dawes Review 10: The impact of deep learning for the analysis of galaxy surveys

AbstractThe amount and complexity of data delivered by modern galaxy surveys has been steadily increasing over the past years. New facilities will soon provide imaging and spectra of hundreds of millions of galaxies. Extracting coherent scientific information from these large and multi-modal data sets remains an open issue for the community and data-driven approaches such as deep learning have rapidly emerged as a potentially powerful solution to some long lasting challenges. This enthusiasm is reflected in an unprecedented exponential growth of publications using neural networks, which have gone from a handful of works in 2015 to an average of one paper per week in 2021 in the area of galaxy surveys. Half a decade after the first published work in astronomy mentioning deep learning, and shortly before new big data sets such as Euclid and LSST start becoming available, we believe it is timely to review what has been the real impact of this new technology in the field and its potential to solve key challenges raised by the size and complexity of the new datasets. The purpose of this review is thus two-fold. We first aim at summarising, in a common document, the main applications of deep learning for galaxy surveys that have emerged so far. We then extract the major achievements and lessons learned and highlight key open questions and limitations, which in our opinion, will require particular attention in the coming years. Overall, state-of-the-art deep learning methods are rapidly adopted by the astronomical community, reflecting a democratisation of these methods. This review shows that the majority of works using deep learning up to date are oriented to computer vision tasks (e.g. classification, segmentation). This is also the domain of application where deep learning has brought the most important breakthroughs so far. However, we also report that the applications are becoming more diverse and deep learning is used for estimating galaxy properties, identifying outliers or constraining the cosmological model. Most of these works remain at the exploratory level though which could partially explain the limited impact in terms of citations. Some common challenges will most likely need to be addressed before moving to the next phase of massive deployment of deep learning in the processing of future surveys; for example, uncertainty quantification, interpretability, data labelling and domain shift issues from training with simulations, which constitutes a common practice in astronomy.

The Rapid ASKAP Continuum Survey IV: continuum imaging at 1367.5 MHz and the first data release of RACS-mid

Abstract The Australian SKA Pathfinder (ASKAP) is being used to undertake a campaign to rapidly survey the sky in three frequency bands across its operational spectral range. The first pass of the Rapid ASKAP Continuum Survey (RACS) at 887.5 MHz in the low band has already been completed, with images, visibility datasets, and catalogues made available to the wider astronomical community through the CSIRO ASKAP Science Data Archive (CASDA). This work presents details of the second observing pass in the mid band at 1367.5 MHz, RACS-mid, and associated data release comprising images and visibility datasets covering the whole sky south of $\delta_{\text{J2000}}=+49^\circ$ . This data release incorporates selective peeling to reduce artefacts around bright sources, as well as accurately modelled primary beam responses. The Stokes I images reach a median noise of 198 $\mu$ Jy PSF $^{-1}$ with a declination-dependent angular resolution of 8.1–47.5 arcsec that fills a niche in the existing ecosystem of large-area astronomical surveys. We also supply Stokes V images after application of a widefield leakage correction, with a median noise of 165 $\mu$ Jy PSF $^{-1}$ . We find the residual leakage of Stokes I into V to be $\lesssim 0.9$ – $2.4$ % over the survey. This initial RACS-mid data release will be complemented by a future release comprising catalogues of the survey region. As with other RACS data releases, data products from this release will be made available through CASDA.

Digitization of 20 years of decametric observations of the Sun and Jupiter in Nançay between 1970 and 1990

Since 1970, decametric observations of the Sun and Jupiter have been acquired on a daily basis from the radio observatory of Nançay, France. The resulting database now forms the worldwide largest set of low frequency observations of the Solar Corona between 10 and 100 MHz and of the Jovian magnetosphere between 10 and 40 MHz. The Nançay Decameter Interferometer (NDI), a two-antenna interferometer, acquired pioneer observations from 1970 to 1978, using analog radio receivers tested on the Arecibo giant radiotelescope. The large Nançay Decameter array (NDA), a phased array of 144 helical antennas, was then constructed in the late 1970s as a ground-based support to the Voyager mission and started routine observations in January 1978 in replacement of the NDI, using similar spectrometers. The NDA is still in operation today and its observations, recorded in a digital format since 1990, are public and daily made accessible to the heliospheric and magnetospheric communities at https://www.obs-nancay.fr/reseau-decametrique/. Before 1990, though, the Nançay decametric observations were recorded on analog devices, such as 35-mm films, magnetic tapes and other paper supports, physically archived at the Observatory of Paris, on its site of the Observatory of Meudon, where they could only be accessed on demand. The NDA team recently undertook a multi-year effort to inventory all the Nançay decametric archives, to refurbish and digitize them in order to preserve and promote this historical data collection, most notably by extending the current public database over the 1970–1990 time interval. We digitized the full collection of 35-mm films, corresponding to a total film length of ∼45.5 km, with a specific high resolution scanner. Each roll was scanned by a series of pixel-to-pixel contiguous images recorded in TIF format with adequate metadata and naming convention. The final ∼40 Tb data volume was archived at Paris Astronomical Data Centre and the physical films were refurbished to be archived in a perennial way. We also digitized the associated observations sheets. Finally, we took advantage of this project to also digitize a sample of 35-mm films extracted from four other historical solar data collections hosted at the Observatory of Paris and dealing with two distinct Nançay radiotelescopes and two Lyot heliographs located at the Observatories of Meudon and Haute-Provence. The digitized, documented, Nançay decametric archives have been publicly released to the community in 2020 at http://archives-decametriques.obspm.fr. After having described the instruments, the data collections and the digitization pipeline, this articles ends with a few scientific case studies, focussing on the search for Jupiter-satellite decametric emissions. For instance, the digitized NDA archives suggest the presence of Gan-A and B emissions, while these were first reported in 2018. This work is a concrete example of how historical astronomical measurements can be preserved and archived along the IAU recommendation, to the benefit of the astronomical community.

Active rejection-enhancement of spectrally tunable liquid crystal geometric phase vortex coronagraphs

Geometric phase optical elements made of space-variant anisotropic media customarily find their optimal operating conditions when a half-wave retardance condition is fulfilled, which allows imparting polarization-dependent changes to an incident wavefront. In practice, intrinsic limitations of a man-made manufacturing process or a finite spectrum of a light source lead to a deviation from the ideal behavior. This implies an implementation of strategies to compensate for the associated efficiency losses. Here, we report on how the intrinsic tunable features of self-engineered liquid crystal topological defects can be used to enhance rejection capabilities of spectrally tunable vector vortex coronagraphs. We also discuss the extent of which current models enable to design efficient devices. The simplicity and decent performance of our approach offer the possibility to an amateur astronomy community to consider the use of vortex coronography.

Impact of the COVID-19 pandemic on publishing in astronomy in the initial two years

The COVID-19 pandemic and associated lockdowns changed working conditions for many researchers worldwide. While there exists initial evidence that these conditions have had a measurable impact on the field of astronomy, a comprehensive quantitative analysis is still outstanding. We study the effects of the pandemic on the astronomy community worldwide, with a special focus on early-career and underrepresented female scientists, using public records of publications. We find that the overall output of the field, measured by the yearly paper count, has increased. This is mainly driven by boosted individual productivity in most countries. However, a decreasing number of incoming new researchers is seen in most countries we studied, indicating higher barriers for new researchers to enter the field or complete their first project during COVID. The overall improvement in productivity is not equally shared by women. A smaller fraction of papers are written by female astronomers and fewer women are among incoming new researchers as compared to pre-pandemic trends, in 14 out of 25 countries we studied. Even though female astronomers became more productive during COVID, the level of improvement is smaller than for men. Pre-COVID, female astronomers in countries such as the Netherlands, Australia and Switzerland were equally as or even more productive than their male colleagues. During COVID, on average, no single country’s female astronomers were able to be equally productive as their male colleagues.

Eureka!: An End-to-End Pipeline for JWST Time-Series Observations

$\texttt{Eureka!}$ is a data reduction and analysis pipeline for exoplanet time-series observations, with a particular focus on JWST data. Over the next 1-2 decades, JWST will pursue four main science themes: Early Universe, Galaxies Over Time, Star Lifecycle, and Other Worlds. Our focus is on providing the astronomy community with an open source tool for the reduction and analysis of time-series observations of exoplanets in pursuit of the fourth of these themes, Other Worlds. The goal of $\texttt{Eureka!}$ is to provide an end-to-end pipeline that starts with uncalibrated FITS files and ultimately yields precise exoplanet spectra. The pipeline has a modular structure with six stages, and each stage uses a "Eureka! Control File" (ECF) to allow for easy control of the pipeline's behavior. Stage 5 also uses a "Eureka! Parameter File" (EPF) to control the fitted parameters. We provide template ECFs for the MIRI, NIRCam, NIRISS, and NIRSpec instruments on JWST and the WFC3 instrument on the Hubble Space Telescope (HST). These templates give users a good starting point for their analyses, but $\texttt{Eureka!}$ is not intended to be used as a black box tool, and users should expect to fine-tune some settings for each observation in order to achieve optimal results. At each stage, the pipeline creates intermediate figures and outputs that allow users to compare $\texttt{Eureka!}$'s performance using different parameter settings or to compare $\texttt{Eureka!}$ with an independent pipeline. The ECF used to run each stage is also copied into the output folder from each stage to enhance reproducibility. Finally, while $\texttt{Eureka!}$ has been optimized for exoplanet observations (especially the latter stages of the code), much of the core functionality could also be repurposed for JWST time-series observations in other research domains thanks to $\texttt{Eureka!}$'s modularity.

Gaia–TESS synergy: improving the identification of transit candidates

Context. The TESS team periodically issues a new list of transiting exoplanet candidates based on the analysis of the accumulating light curves obtained by the satellite. The list includes the estimated epochs, periods, and durations of the potential transits. As the point spread function (PSF) of TESS is relatively wide, follow-up photometric observations at higher spatial resolution are required in order to exclude apparent transits that are actually blended background eclipsing binaries (BEBs). Aims. The Gaia space mission, with its growing database of epoch photometry and high angular resolution, enables the production of distinct light curves for all sources included in the TESS PSF, up to the limiting magnitude of Gaia. This paper reports the results of an ongoing Gaia-TESS collaboration that uses the Gaia photometry to facilitate the identification of BEB candidates and even to confirm on-target candidates in some cases. Methods. We inspected the Gaia photometry of the individual sources included in the TESS PSF, searching for periodic dimming events compatible with their ephemerides and uncertainties, as published by TESS. The performance of the search depends mainly on the number of Gaia measurements during transit and their precision. Results. Since February 2021, the collaboration has been able to confirm 126 on-target candidates and exclude 124 as BEBs. Since June 2021, when our search methodology matured, we have been able to identify on the order of 5% as on-target candidates and another 5% as BEBs. Conclusions. This synergistic approach is combining the complementary capabilities of two of the astronomical space missions of NASA and ESA. It serves to optimize the process of detecting new planets by making better use of the resources of the astronomical community.

Survey for distant solar twins (SDST) – II. Design, observations, and data

ABSTRACT Studies of solar twins have key impacts on the astronomical community, but only ∼100–200 nearby solar twins (<1 kpc) have been reliably identified over the last few decades. The aim of our survey (SDST) is to identify ∼150–200 distant solar twins and analogues (up to ≲4 kpc) closer to the Galactic Centre. We took advantage of the precise Gaia and Skymapper surveys to select Sun-like candidates in a 2-deg field, which were observed with the HERMES spectrograph on the Anglo-Australian Telescope. We successfully built up the required signal-to-noise ratio (25-per-pixel in the HERMES red band) for most targets as faint as Gaia G of 17.4 mag. The stellar photometric/astrometric parameters (e.g. Teff, log g, mass) of our candidates are derived in this paper, while the spectroscopic parameters will be presented in the third paper in this SDST series. The selection success rate – the fraction of targets which belong to solar twins or analogues – was estimated from simulated survey data and the Besançon stellar population model, and compared with the actual success rate of the survey. We find that expected and actual success rates agree well, indicating that the numbers of solar twins and analogues we discover in SDST are consistent with expectations, affirming the survey approach. These distant solar analogues are prime targets for testing for any variation in the strength of electromagnetism in regions of higher dark matter density, and can make additional contributions to our understanding of, e.g. Galactic chemical evolution in the inner Milky Way.

Search for Extraterrestrial Intelligence with the ngVLA

The next generation Very Large Array (ngVLA) will be the premiere centimeter-wave radio array in the Northern Hemisphere by the mid 2030s and thus has the potential to be one of the most effective instruments for the search for extraterrestrial intelligence (SETI). We show that, as of now, the ngVLA will be the only facility capable of detecting an extraterrestrial intelligence (ETI) signal generated by an Arecibo-like transmitter further than 300 pc. We present the optimal antenna array configurations and study the proposed frequency band coverage of the ngVLA and its implications to SETI. We argue for the ability to form of the order of 64 commensal high spectral resolution beams, as the large number of line of sights is critical to provide a competitive survey speed when compared to other modern surveys with telescopes such as MeerKAT and the future SKA. We advocate an Ethernet-based telescope architecture design for the ngVLA, which will provide a high degree of flexibility in SETI data analysis and will benefit the wider astronomy community through commensal science and open-source code, maximizing the potential scientific output of the ngVLA.

From Nobeyama Radio Observatory to the international project ALMA -Evolution of millimeter and submillimeter wave astronomy in Japan.

The establishment of the Nobeyama Radio Observatory (NRO) in 1982 was an important event that greatly influenced the subsequent development of Japanese astronomy. The 45 m radio telescope and the Nobeyama Millimeter Array (NMA) pushed Japanese radio astronomy to the forefront of the world. As a plan beyond the Nobeyama telescopes, the Japanese radio astronomy community considered a large array to achieve unprecedented resolution at millimeter and submillimeter wavelengths under the project name of the Large Millimeter and Submillimeter Array (LMSA). After long and patient discussions and negotiations with the United States and Europe, the LMSA plan eventually led to the ALMA (Atacama Large Millimeter/submillimeter Array) as an international joint project, and the ALMA was inaugurated in 2013. This paper reviews the process from the establishment of the NRO to the realization of the ALMA, including planning of the LMSA, international negotiations, site survey, instrumental developments, and initial science results.

Extreme TeV BL Lacs: a self-consistent stochastic acceleration model

ABSTRACT Lately, a specific kind of blazars drew the attention of the gamma-ray astronomy community: the extreme TeV BL Lacs, blazars that present an extremely energetic and hard emission at very high-energy. Explaining their features is still an open challenge, in fact the most used phenomenological models have difficulties to satisfactorily reproduce their spectral energy distribution. Based on a scenario we have recently proposed, we suppose that the non-thermal particles are first accelerated by a jet recollimation shock, which induces turbulence in the rest of the jet. Non-thermal particles are further accelerated by the turbulence, which hardens the particle spectra and accordingly the radiative emission. Given the physical properties of the plasma, as inferred by emission models, we expect a strong impact of the accelerating particles on the turbulence. Assuming isotropy and homogeneity, the interaction between non-thermal particles and turbulence and their spectra is modelled solving a system of two non-linear, coupled Fokker–Planck equations, while the radiative emission is calculated through the Synchrotron Self Compton model. The emission predicted by our model is then compared with the prototype extreme TeV BL Lac object 1ES 0229+200 and the parameters obtained to reproduce its SED are in line with the expectations.

Investigating the accuracy achievable in reconstructing the angular sizes of stars through stellar intensity interferometry observations

Context. In recent years, stellar intensity interferometry has seen renewed interest from the astronomical community because it can be efficiently applied to Cherenkov telescope arrays. Aims. We have investigated the accuracy that can be achieved in reconstructing stellar sizes by fitting the visibility curve measured on the ground. The large number of expected available astronomical targets, the limited number of nights in a year, and the likely presence of multiple baselines will require careful planning of the observational strategy to maximise the scientific output. Methods. We studied the trend of the error on the estimated angular size, considering the uniform disk model, by varying several parameters related to the observations, such as the total number of measurements, the integration time, the signal-to-noise ratio, and different positions along the baseline. Results. We found that measuring the value of the zero-baseline correlation is essential to obtain the best possible results. Systems that can measure this value directly or for which it is known in advance will have better sensitivity. We also found that to minimise the integration time, it is sufficient to obtain a second measurement at a baseline half-way between 0 and that corresponding to the first zero of the visibility function. This function does not have to be measured at multiple positions. Finally, we obtained some analytical expressions that can be used under specific conditions to determine the accuracy that can be achieved in reconstructing the angular size of a star in advance. This is useful to optimise the observation schedule.

Millimeter wave spectrum and search for vinyl isocyanate toward Sgr B2(N) with ALMA

Context. The interstellar detections of isocyanic acid (HNCO), methyl isocyanate (CH3NCO), and very recently also ethyl isocyanate (C2H5NCO) invite the question of whether or not vinyl isocyanate (C2H3NCO) can be detected in the interstellar medium. There are only low-frequency spectroscopic data (<40 GHz) available for this species in the literature, which makes predictions at higher frequencies rather uncertain, which in turn hampers searches for this molecule in space using millimeter (mm) wave astronomy. Aims. The aim of the present study is on one hand to extend the laboratory rotational spectrum of vinyl isocyanate to the mm wave region and on the other to search, for the first time, for its presence in the high-mass star-forming region Sgr B2, where other isocyanates and a plethora of complex organic molecules are observed. Methods. We recorded the pure rotational spectrum of vinyl isocyanate in the frequency regions 127.5–218 and 285–330 GHz using the Prague mm wave spectrometer. The spectral analysis was supported by high-level quantum-chemical calculations. On the astronomy side, we assumed local thermodynamic equilibrium to compute synthetic spectra of vinyl isocyanate and to search for it in the ReMoCA survey performed with the Atacama Large Millimeter/submillimeter Array (ALMA) toward the high-mass star-forming protocluster Sgr B2(N). Additionally, we searched for the related molecule ethyl isocyanate in the same source. Results. Accurate values for the rotational and centrifugal distortion constants are reported for the ground vibrational states of trans and cis vinyl isocyanate from the analysis of more than 1000 transitions. We report nondetections of vinyl and ethyl isocyanate toward the main hot core of Sgr B2(N). We find that vinyl and ethyl isocyanate are at least 11 and 3 times less abundant than methyl isocyanate in this source, respectively. Conclusions. Although the precise formation mechanism of interstellar methyl isocyanate itself remains uncertain, we infer from existing astrochemical models that our observational upper limit for the CH3NCO:C2H5NCO ratio in Sgr B2(N) is consistent with ethyl isocyanate being formed on dust grains via the abstraction or photodissociation of an H atom from methyl isocyanate, followed by the addition of a methyl radical. The dominance of such a process for ethyl isocyanate production, combined with the absence of an analogous mechanism for vinyl isocyanate, would indicate that the ratio C2H3NCO:C2H5NCO should be less than unity. Even though vinyl isocyanate was not detected toward Sgr B2(N), the results of this work represent a significant improvement on previous low-frequency studies and will help the astronomical community to continue searching for this species in the Universe.