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Sökning: WFRF:(Pignata C)

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3.
  • Ackley, K., et al. (författare)
  • Observational constraints on the optical and near-infrared emission from the neutron star-black hole binary merger candidate S190814bv
  • 2020
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 643
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Gravitational wave (GW) astronomy has rapidly reached maturity, becoming a fundamental observing window for modern astrophysics. The coalescences of a few tens of black hole (BH) binaries have been detected, while the number of events possibly including a neutron star (NS) is still limited to a few. On 2019 August 14, the LIGO and Virgo interferometers detected a high-significance event labelled S190814bv. A 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.Aims. In this paper, we present our extensive search campaign aimed at uncovering the potential optical and near infrared electromagnetic counterpart of S190814bv. We found no convincing electromagnetic counterpart in our data. We therefore use our non-detection to place limits on the properties of the putative outflows that could have been produced by the binary during and after the merger.Methods. Thanks to the three-detector observation of S190814bv, and given the characteristics of the signal, the LIGO and Virgo Collaborations delivered a relatively narrow localisation in low latency - a 50% (90%) credible area of 5 deg(2) (23 deg(2)) - despite the relatively large distance of 26752 Mpc. ElectromagNetic counterparts of GRAvitational wave sources at the VEry Large Telescope collaboration members carried out an intensive multi-epoch, multi-instrument observational campaign to identify the possible optical and 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. In this paper, we describe the combined observational campaign of these groups.Results. Our observations allow us to place limits on the presence of any counterpart and discuss the implications for the kilonova (KN), which was possibly generated by this NS-BH merger, and for the strategy of future searches. The typical depth of our wide-field observations, which cover most of the projected sky localisation probability (up to 99.8%, depending on the night and filter considered), is r similar to 22 (resp. K similar to 21) in the optical (resp. near infrared). We reach deeper limits in a subset of our galaxy-targeted observations, which cover a total similar to 50% of the galaxy-mass-weighted localisation probability. Altogether, our observations allow us to exclude a KN with large ejecta mass M greater than or similar to 0.1 M-circle dot to a high (> 90%) confidence, and we can exclude much smaller masses in a sub-sample of our observations. This disfavours the tidal disruption of the neutron star during the merger.Conclusions. 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 hundred megaparsecs will be detected only by large facilities with both a 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.
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4.
  • Smartt, S. J., et al. (författare)
  • A kilonova as the electromagnetic counterpart to a gravitational-wave source
  • 2017
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 551:7678, s. 75-
  • Tidskriftsartikel (refereegranskat)abstract
    • Gravitational waves were discovered with the detection of binary black-hole mergers(1) and they should also be detectable from lower-mass neutron-star mergers. These are predicted to eject material rich in heavy radioactive isotopes that can power an electromagnetic signal. This signal is luminous at optical and infrared wavelengths and is called a kilonova(2-5). The gravitational-wave source GW170817 arose from a binary neutron-star merger in the nearby Universe with a relatively well confined sky position and distance estimate(6). Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC 4993, which is spatially coincident with GW170817 and with a weak, short.-ray burst(7,8). The transient has physical parameters that broadly match the theoretical predictions of blue kilonovae from neutron-star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 +/- 0.01 solar masses, with an opacity of less than 0.5 square centimetres per gram, at a velocity of 0.2 +/- 0.1 times light speed. The power source is constrained to have a power-law slope of -1.2 +/- 0.3, consistent with radioactive powering from r-process nuclides. (The r-process is a series of neutron capture reactions that synthesise many of the elements heavier than iron.) We identify line features in the spectra that are consistent with light r-process elements (atomic masses of 90-140). As it fades, the transient rapidly becomes red, and a higher-opacity, lanthanide-rich ejecta component may contribute to the emission. This indicates that neutron-star mergers produce gravitational waves and radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements.
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5.
  • Smartt, S. J., et al. (författare)
  • PESSTO : survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects
  • 2015
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 579
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. The Public European Southern Observatory Spectroscopic Survey of Transient Objects (PESSTO) began as a public spectroscopic survey in April 2012. PESSTO classifies transients from publicly available sources and wide-field surveys, and selects science targets for detailed spectroscopic and photometric follow-up. PESSTO runs for nine months of the year, January - April and August - December inclusive, and typically has allocations of 10 nights per month. Aims. We describe the data reduction strategy and data products that are publicly available through the ESO archive as the Spectroscopic Survey data release 1 (SSDR1). Methods. PESSTO uses the New Technology Telescope with the instruments EFOSC2 and SOFI to provide optical and NIR spectroscopy and imaging. We target supernovae and optical transients brighter than 20.5(m) for classification. Science targets are selected for follow-up based on the PESSTO science goal of extending knowledge of the extremes of the supernova population. We use standard EFOSC2 set-ups providing spectra with resolutions of 13-18 angstrom between 3345-9995 angstrom. A subset of the brighter science targets are selected for SOFI spectroscopy with the blue and red grisms (0.935-2.53 mu m and resolutions 23-33 angstrom) and imaging with broadband JHK(s) filters. Results. This first data release (SSDR1) contains flux calibrated spectra from the first year (April 2012-2013). A total of 221 confirmed supernovae were classified, and we released calibrated optical spectra and classifications publicly within 24 h of the data being taken (via WISeREP). The data in SSDR1 replace those released spectra. They have more reliable and quantifiable flux calibrations, correction for telluric absorption, and are made available in standard ESO Phase 3 formats. We estimate the absolute accuracy of the flux calibrations for EFOSC2 across the whole survey in SSDR1 to be typically similar to 15%, although a number of spectra will have less reliable absolute flux calibration because of weather and slit losses. Acquisition images for each spectrum are available which, in principle, can allow the user to refine the absolute flux calibration. The standard NIR reduction process does not produce high accuracy absolute spectrophotometry but synthetic photometry with accompanying JHK(s) imaging can improve this. Whenever possible, reduced SOFI images are provided to allow this. Conclusions. Future data releases will focus on improving the automated flux calibration of the data products. The rapid turnaround between discovery and classification and access to reliable pipeline processed data products has allowed early science papers in the first few months of the survey.
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6.
  • Pastorello, A., et al. (författare)
  • A luminous stellar outburst during a long-lasting eruptive phase first, and then SN IIn 2018cnf
  • 2019
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 628
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the results of the monitoring campaign of the Type IIn supernova (SN) 2018cnf (a.k.a. ASASSN-18mr). It was discovered about ten days before the maximum light (on MJD = 58 293.4 +/- 5.7 in the V band, with M-V = -18.13 +/- 0.15 mag). The multiband light curves show an immediate post-peak decline with some minor luminosity fluctuations, followed by a flattening starting about 40 days after maximum. The early spectra are relatively blue and show narrow Balmer lines with P Cygni profiles. Additionally, Fe II, O I, He I, and Ca II are detected. The spectra show little evolution with time and with intermediate-width features becoming progressively more prominent, indicating stronger interaction of the SN ejecta with the circumstellar medium. The inspection of archival images from the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) survey has revealed a variable source at the SN position with a brightest detection in December 2015 at M-r = -14.66 +/- 0.17 mag. This was likely an eruptive phase from the massive progenitor star that started from at least mid-2011, and that produced the circumstellar environment within which the star exploded as a Type IIn SN. The overall properties of SN 2018cnf closely resemble those of transients such as SN 2009ip. This similarity favours a massive hypergiant, perhaps a luminous blue variable, as progenitor for SN 2018cnf.
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7.
  • Tartaglia, L., et al. (författare)
  • The Early Detection and Follow-up of the Highly Obscured Type II Supernova 2016ija/DLT16am
  • 2018
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 853:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We present our analysis of the Type II supernova DLT16am (SN 2016ija). The object was discovered during the ongoing D < 40 Mpc (DLT40) one-day cadence supernova search at r similar to 20.1 mag in the edge-on nearby (D = 20.0 +/- 4.0 Mpc) galaxy NGC 1532. The subsequent prompt and high-cadenced spectroscopic and photometric follow-up revealed a highly extinguished transient, with E(B - V) = 1.95 +/- 0.15 mag, consistent with a standard extinction law with R-V = 3.1 and a bright (M-V = -18.48 +/- 0.77 mag) absolute peak magnitude. A comparison of the photometric features with those of large samples of SNe II reveals a fast rise for the derived luminosity and a relatively short plateau phase, with a slope of S-50V = 0.84 +/- 0.04 mag/50 days, consistent with the photometric properties typical of those of fast-declining SNe II. Despite the large uncertainties on the distance and the extinction in the direction of DLT16am, the measured photospheric expansion velocity and the derived absolute V-band magnitude at similar to 50 days after the explosion match the existing luminosity-velocity relation for SNe II.
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8.
  • Andrews, Jennifer E., et al. (författare)
  • SN 2017gmr : An Energetic Type II-P Supernova with Asymmetries
  • 2019
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 885:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We present high-cadence UV, optical, and near-infrared data on the luminous Type II-P supernova SN;2017gmr from hours after discovery through the first 180 days. SN;2017gmr does not show signs of narrow, high-ionization emission lines in the early optical spectra, yet the optical light-curve evolution suggests that an extra energy source from circumstellar medium (CSM) interaction must be present for at least 2 days after explosion. Modeling of the early light curve indicates a ?500 R progenitor radius, consistent with a rather compact red supergiant, and late-time luminosities indicate that up to 0.130;;0.026 M of Ni-56 are present, if the light curve is solely powered by radioactive decay, although the Ni-56 mass may be lower if CSM interaction contributes to the post-plateau luminosity. Prominent multipeaked emission lines of H? and [O i] emerge after day 154, as a result of either an asymmetric explosion or asymmetries in the CSM. The lack of narrow lines within the first 2 days of explosion in the likely presence of CSM interaction may be an example of close, dense, asymmetric CSM that is quickly enveloped by the spherical supernova ejecta.
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9.
  • Gall, C., et al. (författare)
  • Two transitional type Ia supernovae located in the Fornax cluster member NGC 1404 : SN 2007on and SN 2011iv
  • 2018
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 611
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an analysis of ultraviolet (UV) to near-infrared observations of the fast-declining Type Ia supernovae (SNe Ia) 2007on and 2011iv, hosted by the Fornax cluster member NGC 1404. The B-band light curves of SN 2007on and SN 2011iv are characterised by Delta m(15)(B) decline-rate values of 1.96 mag and 1.77 mag, respectively. Although they have similar decline rates, their peak B-and H-band magnitudes di ff er by similar to 0.60 mag and similar to 0.35 mag, respectively. After correcting for the luminosity vs. decline rate and the luminosity vs. colour relations, the peak B-band and H-band light curves provide distances that di ff er by similar to 14% and similar to 9%, respectively. These findings serve as a cautionary tale for the use of transitional SNe Ia located in early-type hosts in the quest to measure cosmological parameters. Interestingly, even though SN 2011iv is brighter and bluer at early times, by three weeks past maximum and extending over several months, its B - V colour is 0.12 mag redder than that of SN 2007on. To reconcile this unusual behaviour, we turn to guidance from a suite of spherical one-dimensional Chandrasekhar-mass delayed-detonation explosion models. In this context, Ni-56 production depends on both the so-called transition density and the central density of the progenitor white dwarf. To first order, the transition density drives the luminosity-width relation, while the central density is an important second-order parameter. Within this context, the di ff erences in the B - V colour evolution along the Lira regime suggest that the progenitor of SN 2011iv had a higher central density than SN 2007on.
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10.
  • Kangas, T., et al. (författare)
  • Supernova 2013fc in a circumnuclear ring of a luminous infrared galaxy : the big brother of SN 1998S
  • 2016
  • Ingår i: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 456:1, s. 323-346
  • Tidskriftsartikel (refereegranskat)abstract
    • We present photometric and spectroscopic observations of SN 2013fc, a bright type II supernova (SN) in a circumnuclear star-forming ring in the luminous infrared galaxy ESO 154-G010, observed as part of the Public ESO Spectroscopic Survey of Transient Objects. SN 2013fc is both photometrically and spectroscopically similar to the well-studied type IIn SN 1998S and to the bright type II-L SN 1979C. It exhibits an initial linear decline, followed by a short plateau phase and a tail phase with a decline too fast for Co-56 decay with full. gamma-ray trapping. Initially, the spectrum was blue and featureless. Later on, a strong broad (similar to 8000 km s(-1)) H alpha emission profile became prominent. We apply a STARLIGHT stellar population model fit to the SN location (observed when the SN had faded) to estimate a high extinction of A(V) = 2.9 +/- 0.2 mag and an age of 10(+ 3) (- 2) Myr for the underlying cluster. We compare the SN to SNe 1998S and 1979C and discuss its possible progenitor star considering the similarities to these events. With a peak brightness of B = - 20.46 +/- 0.21 mag, SN 2013fc is 0.9 mag brighter than SN 1998S and of comparable brightness to SN 1979C. We suggest that SN 2013fc was consistent with a massive red supergiant (RSG) progenitor. Recent mass loss probably due to a strong RSG wind created the circumstellar matter illuminated through its interaction with the SN ejecta. We also observe a near- infrared excess, possibly due to newly condensed dust.
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