On 2019 August 14, the LIGO and Virgo interferometers detected a high-significance event labelled S190814bv. Preliminary analysis of the GW data suggests that the event was likely due to the merger ...of a compact binary system formed by a BH and a NS. ElectromagNetic counterparts of GRAvitational wave sources at the VEry Large Telescope (ENGRAVE) collaboration members carried out an intensive multi-epoch, multi-instrument observational campaign to identify the possible optical/near infrared counterpart of the event. In addition, the ATLAS, GOTO, GRAWITA-VST, Pan-STARRS and VINROUGE projects also carried out a search on this event. Our observations allow us to place limits on the presence of any counterpart and discuss the implications for the kilonova (KN) possibly generated by this NS-BH merger, and for the strategy of future searches. Altogether, our observations allow us to exclude a KN with large ejecta mass $M\gtrsim 0.1\,\mathrm{M_\odot}$ to a high ($>90\%$) confidence, and we can exclude much smaller masses in a subsample of our observations. This disfavours the tidal disruption of the neutron star during the merger. Despite the sensitive instruments involved in the campaign, given the distance of S190814bv we could not reach sufficiently deep limits to constrain a KN comparable in luminosity to AT 2017gfo on a large fraction of the localisation probability. This suggests that future (likely common) events at a few hundreds Mpc will be detected only by large facilities with both high sensitivity and large field of view. Galaxy-targeted observations can reach the needed depth over a relevant portion of the localisation probability with a smaller investment of resources, but the number of galaxies to be targeted in order to get a fairly complete coverage is large, even in the case of a localisation as good as that of this event.
Unveiling the enigma of ATLAS17aeu Melandri, A.; Rossi, A.; Benetti, S. ...
Astronomy & astrophysics,
01/2019, Volume:
621
Journal Article
Peer reviewed
Open access
Aims. The unusual transient ATLAS17aeu was serendipitously detected within the sky localisation of the gravitational wave trigger GW 170104. The importance of a possible association with ...gravitational waves coming from a binary black hole merger led to an extensive follow-up campaign, with the aim of assessing a possible connection with GW 170104. Methods. With several telescopes, we carried out both photometric and spectroscopic observations of ATLAS17aeu, for several epochs, between ∼3 and ∼230 days after the first detection. Results. We studied in detail the temporal and spectroscopic properties of ATLAS17aeu and its host galaxy. Although at low significance and not conclusive, we found similarities to the spectral features of a broad-line supernova superposed onto an otherwise typical long-GRB afterglow. Based on analysis of the optical light curve, spectrum, and host galaxy spectral energy distribution, we conclude that the redshift of the source is probably z ≃ 0.5 ± 0.2. Conclusions. While the redshift range we have determined is marginally compatible with that of the gravitational wave event, the presence of a supernova component and the consistency of this transient with the Ep–Eiso correlation support the conclusion that ATLAS17aeu was associated with the long gamma-ray burst GRB 170105A. This rules out the association of the GRB 170105A/ATLAS17aeu transient with the gravitational wave event GW 170104, which was due to a binary black hole merger.
The results of calculations of the probability of a leak appearing in the tube band of steam generator in a VVÉR-440 reactor system during operation are presented. The MAVR-1.1 computer code is used ...to calculate the probability of the formation of a leak and rupture of one of the heat exchanger tubes. The binomial distribution is used to determine the probability of the number of tubes that do not satisfy the plugging criterion. A leak in a tube bank is calculated as a sum of leaks in individual tubes. The probability of such a leak is calculated as a random sum. The calculations show that the parameters of test measures (pressure of the hydraulic tests, reliability of nondestructive testing for defects) and the sequence in which they are performed have a large effect on the failure probability of a tube bank during reactor operation. The computational results and the experience gained in operating steam generators show that the algorithm and the method developed for computing the leak probability could be helpful for estimating the strength reliability of heat exchanger tubes.PUBLICATION ABSTRACT
Knowledge of radial velocities, elemental abundances, and accretion properties of members of star-forming regions is important for the authors understanding of stellar and planetary formation. ...Existing 2MASS archive data and the Spitzer c2d survey of the Chamaeleon II dark cloud have provided disk properties of a large number of young stars. They complement these data with optical spectroscopy with the aim of providing physical stellar parameters and accretion properties. They use FLAMES/UVES and FLAMES/GIRAFFE spectroscopic observations of 40 members of the Chamaeleon II star-forming region to measure radial velocities through cross-correlation technique, lithium abundances by means of curves of growth, and for a suitable star elemental abundances of Fe, Al, Si, Ca, Ti, and Ni using the code MOOG. They derive a radial velocity distribution for the Chamaeleon II stars, which is peaked at ... . They find dependencies of ... and of ... in the similar to 0.1 M-1.0 M mass regime, as well as a mean mass accretion rate for Chamaeleon II of ... (ProQuest: ... denotes formulae/symbols omitted.)
We report the discovery of a candidate to quadrupole gravitationally lensed system KiDS0239-3211 based on the public data release 3 of the KiDS survey and machine learning techniques.
The results of a computational investigation of the possibility of and the safety conditions for switching from a 4- to an 8-yr time interval between technical inspections of the main circulation ...pipeline and the pressure compensator vessel in VVER-1000 reactors are presented. To this end, calculations of the critical and admissable sizes of defects in the main metal and weld seams in the operating regime, in accident situations, and during earthquakes have been performed. Calculations of the time for a through defect to reach a critical size for different operating periods have been performed. The influence of the hydrotesting pressure and the time interval between such tests on the operational safety and the effect of the time between technical inspections on the reliability of the indicated first-loop components of a VVER-1000 reactor with respect to the criterion of fracture resistance, taking account of the probabilistic nature of the initial data, is analyzed. The calculations were performed using normative and certified procedures geared toward the typical characteristics of steel and structures and the conditions of fabrication, assembly, and operation.
Core-collapse stripped-envelope supernova (SN) explosions reflect the diversity of physical parameters and evolutionary paths of their massive star progenitors. We have observed the Type Ic SN ...iPTF15dld (z = 0.047), reported by the Palomar Transient Factory. Spectra were taken starting 20 rest-frame days after maximum luminosity and are affected by a young stellar population background. Broad spectral absorption lines associated with the SN are detected over the continuum, similar to those measured for broad-lined, highly energetic SNe Ic. The light curve and maximum luminosity are instead more similar to those of low luminosity, narrow-lined Ic SNe. This suggests a behaviour whereby certain highly stripped-envelope SNe do not produce a large amount of 56Ni, but the explosion is sufficiently energetic that a large fraction of the ejecta is accelerated to higher than usual velocities. Here, we estimate SN iPTF15dld had a main-sequence progenitor of 20–25 M⊙, produced a 56Ni mass of ~0.1–0.2 M⊙, had an ejecta mass of 2–10 M⊙, and a kinetic energy of 1–18 × 1051 erg.
Quadruply lensed quasars are extremely rare objects, but incredibly powerful cosmological tools. Only few dozen are known in the whole sky. Here we present the spectroscopic confirmation of two new ...quadruplets WG0214-2105 and WG2100-4452 discovered by Agnello & Spiniello (2018) within the Dark Energy Survey (DES) public footprints. We have conducted spectroscopic follow-up of these systems with the Southern African Large Telescope as part of a program that aims at confirming the largest possible number of optically selected strong gravitational lensing systems in the Equatorial and Southern Hemisphere. For both systems, we present the spectra for the sources and deflectors that allowed us to estimate the source redshifts and unambiguously confirm their lensing nature. For the brighter deflector (WG2100-4452), we measure the stellar velocity dispersion from the spectrum. We also obtain photometry for both lenses, directly from DES multi-band images, isolating the lens galaxies from the quasar images. One of the quadruplets, WG0214-2105, was also observed by Pan-STARRS, allowing us to estimate the apparent brightness of each quasar image at two different epochs, and thus to find evidence for flux variability. This result could suggest a microlensing event for the faintest components, although intrinsic variability cannot be excluded with only two epochs. Finally, we present simple lens models for both quadruplets, obtaining Einstein radii, SIE velocity dispersions, ellipticities, and position angles of the lens systems, as well as time delay predictions assuming a concordance cosmological model.
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