Abstract
We introduce the Automatic Learning for the Rapid Classification of Events (ALeRCE) broker, an astronomical alert broker designed to provide a rapid and self-consistent classification of ...large etendue telescope alert streams, such as that provided by the Zwicky Transient Facility (ZTF) and, in the future, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). ALeRCE is a Chilean-led broker run by an interdisciplinary team of astronomers and engineers working to become intermediaries between survey and follow-up facilities. ALeRCE uses a pipeline that includes the real-time ingestion, aggregation, cross-matching, machine-learning (ML) classification, and visualization of the ZTF alert stream. We use two classifiers: a stamp-based classifier, designed for rapid classification, and a light curve–based classifier, which uses the multiband flux evolution to achieve a more refined classification. We describe in detail our pipeline, data products, tools, and services, which are made public for the community (see
https://alerce.science
). Since we began operating our real-time ML classification of the ZTF alert stream in early 2019, we have grown a large community of active users around the globe. We describe our results to date, including the real-time processing of 1.5 × 10
8
alerts, the stamp classification of 3.4 × 10
7
objects, the light-curve classification of 1.1 × 10
6
objects, the report of 6162 supernova candidates, and different experiments using LSST-like alert streams. Finally, we discuss the challenges ahead in going from a single stream of alerts such as ZTF to a multistream ecosystem dominated by LSST.
ABSTRACT We present the first results of the High Cadence Transient Survey (HiTS), a survey for which the objective is to detect and follow-up optical transients with characteristic timescales from ...hours to days, especially the earliest hours of supernova (SN) explosions. HiTS uses the Dark Energy Camera and a custom pipeline for image subtraction, candidate filtering and candidate visualization, which runs in real-time to be able to react rapidly to the new transients. We discuss the survey design, the technical challenges associated with the real-time analysis of these large volumes of data and our first results. In our 2013, 2014, and 2015 campaigns, we detected more than 120 young SN candidates, but we did not find a clear signature from the short-lived SN shock breakouts (SBOs) originating after the core collapse of red supergiant stars, which was the initial science aim of this survey. Using the empirical distribution of limiting magnitudes from our observational campaigns, we measured the expected recovery fraction of randomly injected SN light curves, which included SBO optical peaks produced with models from Tominaga et al. (2011) and Nakar & Sari (2010). From this analysis, we cannot rule out the models from Tominaga et al. (2011) under any reasonable distributions of progenitor masses, but we can marginally rule out the brighter and longer-lived SBO models from Nakar & Sari (2010) under our best-guess distribution of progenitor masses. Finally, we highlight the implications of this work for future massive data sets produced by astronomical observatories, such as LSST.
We present a statistical analysis of the environments of 11 supernovae (SNe) which occurred in six nearby galaxies (z ... 0.016). All galaxies were observed with MUSE, the high spatial resolution ...integral-field spectrograph mounted to the 8 m VLT UT4. These data enable us to map the full spatial extent of host galaxies up to ~3 effective radii. In this way, not only can one characterize the specific host environment of each SN, one can compare their properties with stellar populations within the full range of other environments within the host. We present a method that consists of selecting all H II regions found within host galaxies from 2D extinction-corrected H alpha emission maps. These regions are then characterized in terms of their H alpha equivalent widths, star formation rates and oxygen abundances. Identifying H II regions spatially coincident with SN explosion sites, we are thus able to determine where within the distributions of host galaxy e.g. metallicities and ages each SN is found, thus providing new constraints on SN progenitor properties. This initial pilot study using MUSE opens the way for a revolution in SN environment studies where we are now able to study multiple environment SN progenitor dependencies using a single instrument and single pointing. (ProQuest: ... denotes formulae/symbols omitted.)
Abstract
We report the observations of solar system objects during the 2015 campaign of the High cadence Transient Survey (HiTS). We found 5740 bodies (mostly Main Belt asteroids), 1203 of which were ...detected in different nights and in
g
′ and
r
′. Objects were linked in the barycenter system and their orbital parameters were computed assuming Keplerian motion. We identified 6 near Earth objects, 1738 Main Belt asteroids and 4 Trans-Neptunian objects. We did not find a
g
′−
r
′ color–size correlation for 14 <
H
g
′
< 18 (1 <
D
< 10 km) asteroids. We show asteroids’ colors are disturbed by HiTS’ 1.6 hr cadence and estimate that observations should be separated by at most 14 minutes to avoid confusion in future wide-field surveys like LSST. The size distribution for the Main Belt objects can be characterized as a simple power law with slope ∼0.9, steeper than in any other survey, while data from the 2014 HiTS campaign has a distribution consistent with previous ones (slopes ∼0.68 at the bright end and ∼0.34 at the faint end). This difference is likely due to the ecliptic distribution of the Main Belt since the 2015 campaign surveyed farther from the ecliptic than did 2014's and most previous surveys.
The study of hot corinos in solar-like protostars has been so far mostly limited to the Class 0 phase, hampering our understanding of their origin and evolution. In addition, recent evidence suggests ...that planet formation starts already during Class I phase, which therefore represents a crucial step in the future planetary system chemical composition. Hence, the study of hot corinos in Class I protostars has become of paramount importance. Here, we report the discovery of a hot corino towards the prototypical Class I protostar L1551 IRS5, obtained within the ALMA (Atacama Large Millimeter/submillimeter Array) Large Program FAUST (Fifty AU STudy of the chemistry in the disc/envelope system of solar-like protostars). We detected several lines from methanol and its isotopologues (13CH3OH and CH2DOH), methyl formate, and ethanol. Lines are bright towards the north component of the IRS5 binary system, and a possible second hot corino may be associated with the south component. The methanol lines' non-LTE analysis constrains the gas temperature (∼100 K), density (≥1.5 × 10^8 per cu.cm), and emitting size (∼10 au in radius). All CH3OH and 13CH3OH lines are optically thick, preventing a reliable measure of the deuteration. The methyl formate and ethanol relative abundances are compatible with those measured in Class 0 hot corinos. Thus, based on this work, little chemical evolution from Class 0 to I hot corinos occurs.
In the design of Wireless Mesh Networks (WMNs), one of the fundamental considerations is the reliability and availability of communication paths between network pairs in the presence of node ...failures. Reliability and deployment cost are important and are largely determined by network topology. In fact, adding redundant network components increases the reliability of a network, but also increases the cost substantially. Usually, network performance and reliability are considered separately. In this paper, we propose a new algorithm based on ear decomposition for constructing reliable WMN infrastructure that resists the failure of a single mesh node and ensures full coverage to all Mesh Clients (MCs). Via a case study, we show the tight relationship between network deployment cost, performance and reliability in a simultaneous optimization in terms of cost and traffic load balancing over network channels. The proposed multi-objective optimization model is solved using meta-heuristics which provides the network operator with a set of reliable tradeoff solutions.
ABSTRACT
The ALMA interferometer has played a key role in revealing a new component of the Sun-like star forming process: the molecular streamers, i.e. structures up to thousands of au long ...funnelling material non-axisymmetrically to discs. In the context of the FAUST ALMA LP, the archetypical VLA1623-2417 protostellar cluster has been imaged at 1.3 mm in the SO(56–45), SO(66–55), and SiO(5–4) line emission at the spatial resolution of 50 au. We detect extended SO emission, peaking towards the A and B protostars. Emission blue-shifted down to 6.6 km s−1 reveals for the first time a long (∼ 2000 au) accelerating streamer plausibly feeding the VLA1623 B protostar. Using SO, we derive for the first time an estimate of the excitation temperature of an accreting streamer: 33 ± 9 K. The SO column density is ∼ 1014 cm−2, and the SO/H2 abundance ratio is ∼ 10−8. The total mass of the streamer is 3 × 10−3M⊙, while its accretion rate is 3–5 × 10−7M⊙ yr−1. This is close to the mass accretion rate of VLA1623 B, in the 0.6–3 × 10−7M⊙ yr−1 range, showing the importance of the streamer in contributing to the mass of protostellar discs. The highest blue- and red-shifted SO velocities behave as the SiO(5–4) emission, the latter species detected for the first time in VLA1623-2417: the emission is compact (100–200 au), and associated only with the B protostar. The SO excitation temperature is ∼ 100 K, supporting the occurrence of shocks associated with the jet, traced by SiO.
We report on the serendipitous observations of solar system objects imaged during the High cadence Transient Survey 2014 observation campaign. Data from this high-cadence wide-field survey was ...originally analyzed for finding variable static sources using machine learning to select the most-likely candidates. In this work, we search for moving transients consistent with solar system objects and derive their orbital parameters. We use a simple, custom motion detection algorithm to link trajectories and assume Keplerian motion to derive the asteroid's orbital parameters. We use known asteroids from the Minor Planet Center database to assess the detection efficiency of the survey and our search algorithm. Trajectories have an average of nine detections spread over two days, and our fit yields typical errors of , e ∼ 0.07 and i ∼ 0 5 in semimajor axis, eccentricity, and inclination, respectively, for known asteroids in our sample. We extract 7700 orbits from our trajectories, identifying 19 near-Earth objects, 6687 asteroids, 14 Centaurs, and 15 trans-Neptunian objects. This highlights the complementarity of supernova wide-field surveys for solar system research and the significance of machine learning to clean data of false detections. It is a good example of the data-driven science that Large Synoptic Survey Telescope will deliver.
FAUST Vastel, C.; Alves, F.; Ceccarelli, C. ...
Astronomy and astrophysics (Berlin),
08/2022, Letnik:
664, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Aims.
Methanol is a ubiquitous species commonly found in the molecular interstellar medium. It is also a crucial seed species for the build-up of chemical complexity in star forming regions. Thus, ...understanding how its abundance evolves during the star formation process and whether it enriches the emerging planetary system is of paramount importance.
Methods.
We used new data from the ALMA Large Program FAUST (Fifty AU STudy of the chemistry in the disc/envelope system of solar protostars) to study the methanol line emission towards the BHB2007 11 protobinary system (sources A and B), where a complex structure of filaments connecting the two sources with a larger circumbinary disc has previously been detected.
Results.
Twelve methanol lines have been detected with upper energies in the 45–537 K range along with one
13
CH
3
OH transition and one methyl formate (CH
3
OCHO) line blended with one of the methanol transitions. The methanol emission is compact (FWHM ~ 0.5″) and encompasses both protostars, which are separated by only 0.2″ (28 au). In addition, the overall methanol line emission presents three velocity components, which are not spatially resolved by our observations. Nonetheless, a detailed analysis of the spatial origin of these three components suggests that they are associated with three different spatial regions, with two of them close to 11B and the third one associated with 11A. A radiative transfer analysis of the methanol lines gives a kinetic temperature of 100–140 K, an H
2
volume density of 10
6
–10
7
cm
−3
and column density of a few 10
18
cm
−2
in all three components with a source size of ~0.15″. Thus, this hot and dense gas is highly enriched in methanol with an abundance as high as 10
−5
. Using previous continuum data, we show that dust opacity can potentially completely absorb the methanol line emission from the two binary objects.
Conclusions.
Although we cannot firmly exclude other possibilities, we suggest that the detected hot methanol is resulting from the shocked gas from the incoming filaments streaming towards BHB2007 11A and B, respectively. Higher spatial resolution observations are necessary to confirm this hypothesis.
In vitro modeling of neurodegenerative diseases is now possible by using patient-derived induced pluripotent stem cells (iPS). Through them, it is nowadays conceivable to obtain human neurons and ...glia, and study diseases cellular and molecular mechanisms, an attribute that was previously unavailable to any human condition. Amyotrophic lateral sclerosis (ALS) is one of the diseases that has gained a rapid advance with iPS technology. By differentiating motor neurons from iPS cells of ALS- patients, we are studying the mechanisms underlying ALS- disease onset and progression. Here, we introduce a cellular platform to help maintain longevity of ALS iPS-motor neurons, a cellular feature relevant for most late-onset human diseases. Long term cultures of patient-derived iPS cells might prove to be critical for the development of personalized-drugs.
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