Context. Both multi-messenger astronomy and new high-throughput wide-field surveys require flexible tools for the selection and analysis of astrophysical transients. Aims. Here we introduce the alert ...management, photometry, and evaluation of light curves (AMPEL) system, an analysis framework designed for high-throughput surveys and suited for streamed data. AMPEL combines the functionality of an alert broker with a generic framework capable of hosting user-contributed code; it encourages provenance and keeps track of the varying information states that a transient displays. The latter concept includes information gathered over time and data policies such as access or calibration levels. Methods. We describe a novel ongoing real-time multi-messenger analysis using AMPEL to combine IceCube neutrino data with the alert streams of the Zwicky Transient Facility (ZTF). We also reprocess the first four months of ZTF public alerts, and compare the yields of more than 200 different transient selection functions to quantify efficiencies for selecting Type Ia supernovae that were reported to the Transient Name Server (TNS). Results. We highlight three channels suitable for (1) the collection of a complete sample of extragalactic transients, (2) immediate follow-up of nearby transients, and (3) follow-up campaigns targeting young, extragalactic transients. We confirm ZTF completeness in that all TNS supernovae positioned on active CCD regions were detected. Conclusions. AMPEL can assist in filtering transients in real time, running alert reaction simulations, the reprocessing of full datasets as well as in the final scientific analysis of transient data. This is made possible by a novel way of capturing transient information through sequences of evolving states, and interfaces that allow new code to be natively applied to a full stream of alerts. This text also introduces a method by which users can design their own channels for inclusion in the AMPEL live instance that parses the ZTF stream and the real-time submission of high-quality extragalactic supernova candidates to the TNS.
ABSTRACT
An open question in SN Ia research is where the boundary lies between ‘normal’ Type Ia supernovae (SNe Ia) that are used in cosmological measurements and those that sit off the Phillips ...relation. We present the spectroscopic modelling of one such ‘86G-like’ transitional SN Ia, SN 2021rhu, that has recently been employed as a local Hubble Constant calibrator using a tip of the red-giant branch measurement. We detail its modelling from −12 d until maximum brightness using the radiative-transfer spectral-synthesis code tardis. Please check and correct this paper accordingly. We base our modelling on literature delayed-detonation and deflagration models of Chandrasekhar mass white dwarfs, as well as the double-detonation models of sub-Chandrasekhar mass white dwarfs. We present a new method for ‘projecting’ abundance profiles to different density profiles for ease of computation. Due to the small velocity extent and low outer densities of the W7 profile, we find it inadequate to reproduce the evolution of SN 2021rhu as it fails to match the high-velocity calcium components. The host extinction of SN 2021rhu is uncertain but we use modelling with and without an extinction correction to set lower and upper limits on the abundances of individual species. Comparing these limits to literature models we conclude that the spectral evolution of SN 2021rhu is also incompatible with double-detonation scenarios, lying more in line with those resulting from the delayed-detonation mechanism (although there are some discrepancies, in particular a larger titanium abundance in SN 2021rhu compared to the literature). This suggests that SN 2021rhu is likely a lower luminosity, and hence lower temperature, version of a normal SN Ia.
Signals for site-specific nitrogen-top-dressing can be obtained by a sensor mounted on a tractor. The plant appearance can serve as a criterion. The question is which plant criteria provide pertinent ...information and how this can be indicated. Increasing the nitrogen-supply changes leaf colour from yellow-green to blue-green via the chlorophyll-concentration in the leaves and leads to growth of plants. Present sensing systems measure either chlorophyll concentration in the leaves, total area of the leaves or crop resistance against bending. The aim and purpose of this study is to outline prospects for application. Therefore, the emphasis is on results and not on experimental methods, to which references are given. Mainly optical sensing systems relying on reflectance or fluorescence are dealt with. Good signals of the nitrogen-supply can be obtained from the red edge plus the near infrared range of the reflectance. The results with some new spectral indices were better than those with standard spectral indices. Fluorescence sensing instead of reflectance sensing eliminates erroneous signals from bare soil. However, only low supply rates were clearly indicated. The biomass of the crop or the total area of its leaves is a very important criterion. Reflectance indices can take this into account. Fluorescence signals are barely influenced by this parameter.
Context.
With a rapidly rising number of transients detected in astronomy, classification methods based on machine learning are increasingly being employed. Their goals are typically to obtain a ...definitive classification of transients, and for good performance they usually require the presence of a large set of observations. However, well-designed, targeted models can reach their classification goals with fewer computing resources.
Aims.
The aim of this study is to assist in the observational astronomy task of deciding whether a newly detected transient warrants follow-up observations.
Methods.
This paper presents SNGuess, a model designed to find young extragalactic nearby transients with high purity. SNGuess works with a set of features that can be efficiently calculated from astronomical alert data. Some of these features are static and associated with the alert metadata, while others must be calculated from the photometric observations contained in the alert. Most of the features are simple enough to be obtained or to be calculated already at the early stages in the lifetime of a transient after its detection. We calculate these features for a set of labeled public alert data obtained over a time span of 15 months from the Zwicky Transient Facility (ZTF). The core model of SNGuess consists of an ensemble of decision trees, which are trained via gradient boosting.
Results.
Approximately 88% of the candidates suggested by SNGuess from a set of alerts from ZTF spanning from April 2020 to August 2021 were found to be true relevant supernovae (SNe). For alerts with bright detections, this number ranges between 92% and 98%. Since April 2020, transients identified by SNGuess as potential young SNe in the ZTF alert stream are being published to the Transient Name Server (TNS) under the AMPEL_ZTF_NEW group identifier. SNGuess scores for any transient observed by ZTF can be accessed via a web service
https://ampel.zeuthen.desy.de/api/live/docs
. The source code of SNGuess is publicly available
https://github.com/nmiranda/SNGuess
.
Conclusions.
SNGuess is a lightweight, portable, and easily re-trainable model that can effectively suggest transients for follow-up. These properties make it a useful tool for optimizing follow-up observation strategies and for assisting humans in the process of selecting candidate transients.
Prospects and results for optical systems for site-specific on-the-go control of nitrogen-top-dressing in Germany are discussed. The biomass of a crop is a more reliable indicator of the nitrogen ...status than the chlorophyll concentration. The fluorescence signals depend solely on the chlorophyll concentration and not per se on the biomass of the crop. The results indicate that none of the methods analyze the nitrogen status directly. Either the development of the canopy, the chlorophyll concentration within the leaves or both phenomena together is used as indicators of the nitrogen supply. These indicators can also depend on diseases, on deficiency of other nutrients or lack of water. It is suggested that pre-supposition is a healthy crop which is well supplied with water and other nutrients.
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