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Sökning: WFRF:(Tartaglia Leonardo) > Engelska

  • Resultat 1-10 av 38
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1.
  • Abbott, B. P., et al. (författare)
  • Optically targeted search for gravitational waves emitted by core-collapse supernovae during the first and second observing runs of advanced LIGO and advanced Virgo
  • 2020
  • Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 101:8
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the results from a search for gravitational-wave transients associated with core-collapse supernovae observed within a source distance of approximately 20 Mpc during the first and second observing runs of Advanced LIGO and Advanced Virgo. No significant gravitational-wave candidate was detected. We report the detection efficiencies as a function of the distance for waveforms derived from multidimensional numerical simulations and phenomenological extreme emission models. The sources with neutrino-driven explosions are detectable at the distances approaching 5 kpc, and for magnetorotationally driven explosions the distances are up to 54 kpc. However, waveforms for extreme emission models are detectable up to 28 Mpc. For the first time, the gravitational-wave data enabled us to exclude part of the parameter spaces of two extreme emission models with confidence up to 83%, limited by coincident data coverage. Besides, using ad hoc harmonic signals windowed with Gaussian envelopes, we constrained the gravitational-wave energy emitted during core collapse at the levels of 4.27 x 10(-4) M(circle dot)c(2) and 1.28 x 10(-1) M(circle dot)c(2) for emissions at 235 and 1304 Hz, respectively. These constraints are 2 orders of magnitude more stringent than previously derived in the corresponding analysis using initial LIGO, initial Virgo, and GEO 600 data.
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2.
  • Anand, Shreya, et al. (författare)
  • Collapsars as Sites of r-process Nucleosynthesis : Systematic Photometric Near-infrared Follow-up of Type Ic-BL Supernovae
  • 2024
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 962:1
  • Tidskriftsartikel (refereegranskat)abstract
    • One of the open questions following the discovery of GW170817 is whether neutron star (NS) mergers are the only astrophysical sites capable of producing r-process elements. Simulations have shown that 0.01–0.1 M⊙ of r-process material could be generated in the outflows originating from the accretion disk surrounding the rapidly rotating black hole that forms as a remnant to both NS mergers and collapsing massive stars associated with long-duration gamma-ray bursts (collapsars). The hallmark signature of r-process nucleosynthesis in the binary NS merger GW170817 was its long-lasting near-infrared (NIR) emission, thus motivating a systematic photometric study of the light curves of broad-lined stripped-envelope (Ic-BL) supernovae (SNe) associated with collapsars. We present the first systematic study of 25 SNe Ic-BL—including 18 observed with the Zwicky Transient Facility and 7 from the literature—in the optical/NIR bands to determine what quantity of r-process material, if any, is synthesized in these explosions. Using semi-analytic models designed to account for r-process production in SNe Ic-BL, we perform light curve fitting to derive constraints on the r-process mass for these SNe. We also perform independent light curve fits to models without the r-process. We find that the r-process-free models are a better fit to the light curves of the objects in our sample. Thus, we find no compelling evidence of r-process enrichment in any of our objects. Further high-cadence infrared photometric studies and nebular spectroscopic analysis would be sensitive to smaller quantities of r-process ejecta mass or indicate whether all collapsars are completely devoid of r-process nucleosynthesis.
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3.
  • Andrews, Jennifer E., et al. (författare)
  • SN 2017gmr : An Energetic Type II-P Supernova with Asymmetries
  • 2019
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 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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4.
  • Bose, Subhash, et al. (författare)
  • ASASSN-15nx : A Luminous Type II Supernova with a Perfect Linear Decline
  • 2018
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 862:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a luminous Type II supernova, ASASSN-15nx, with a peak luminosity of M-v = -20 mag that is between those of typical core-collapse supernovae and super-luminous supernovae. The post-peak optical light curves show a long, linear decline with a steep slope of 2.5 mag (100 day)(-1) (i.e., an exponential decline in flux) through the end of observations at phase approximate to 260 day. In contrast, the light curves of hydrogen-rich supernovae (SNe II-P/L) always show breaks in their light curves at phase similar to 100 day, before settling onto Co-56 radioactive decay tails with a decline rate of about 1 mag (100 day)(-1). The spectra of ASASSN-15nx do not exhibit the narrow emission-line features characteristic of Type IIn SNe, which can have a wide variety of light-curve shapes usually attributed to strong interactions with a dense circumstellar medium (CSM). ASASSN-15nx has a number of spectroscopic peculiarities, including a relatively weak and triangular-shaped H alpha emission profile with no absorption component. The physical origin of these peculiarities is unclear, but the long and linear post-peak light curve without a break suggests a single dominant powering mechanism. Decay of a large amount of Ni-56 (M-Ni = 1.6 +/- 0.2 M-circle dot) can power the light curve of ASASSN-15nx, and the steep light-curve slope requires substantial gamma-ray escape from the ejecta, which is possible given a low-mass hydrogen envelope for the progenitor. Another possibility is strong CSM interactions powering the light curve, but the CSM needs to be sculpted to produce the unique light-curve shape and avoid producing SN IIn-like narrow emission lines.
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5.
  • Dastidar, Raya, et al. (författare)
  • SN 2015ba : a Type IIP supernova with a long plateau
  • 2018
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 479:2, s. 2421-2442
  • Tidskriftsartikel (refereegranskat)abstract
    • We present optical photometry and spectroscopy from about a week after explosion to similar to 272 d of an atypical Type IIP supernova, SN 2015ba, which exploded in the edge-on galaxy IC 1029. SN 2015ba is a luminous event with an absolute V-band magnitude of -17.1 +/- 0.2 mag at 50 d since explosion and has a long plateau lasting for similar to 123 d. The distance to the SN is estimated to be 34.8 +/- 0.7 Mpc using the expanding photosphere and standard candle methods. High-velocity H Balmer components constant with time are observed in the late-plateau phase spectra of SN 2015ba, which suggests a possible role of circumstellar interaction at these phases. Both hydrodynamical and analytical modelling suggest a massive progenitor of SN 2015ba with a pre-explosion mass of 24-26 M-circle dot. However, the nebular spectra of SN 2015ba exhibit insignificant levels of oxygen, which is otherwise expected from a massive progenitor. This might be suggestive of the non-monotonical link between O-core masses and the zero-age main sequence mass of pre-supernova stars and/or uncertainties in the mixing scenario in the ejecta of supernovae.
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6.
  • Dastidar, R., et al. (författare)
  • The optical properties of three Type II supernovae : 2014cx, 2014cy, and 2015cz
  • 2021
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 504:1, s. 1009-1028
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the photometric and spectroscopic analysis of three Type II supernovae (SNe): 2014cx, 2014cy, and 2015cz. SN 2014cx is a conventional Type IIP with shallow slope (0.2 mag/50 d) and an atypical short plateau (∼86 d). SNe 2014cy and 2015cz show relatively large decline rates (0.88 and 1.64 mag/50 d, respectively) at early times before settling to the plateau phase, unlike the canonical Type IIP/L SN light curves. All of them are normal luminosity SN II with an absolute magnitude at mid-plateau of M50V,14cx=−16.6±0.4mag⁠, M50V,14cy=−16.5±0.2mag⁠, and M50V,15cz=−17.4±0.3mag⁠. A relatively broad range of 56Ni masses is ejected in these explosions (0.027–0.070 M⊙). The spectra shows the classical evolution of  SNe  II, dominated by a blue continuum with broad H lines at early phases and narrower metal lines with P Cygni profiles during the plateau. High-velocity H  i features are identified in the plateau spectra of SN 2014cx at 11 600  kms −1, possibly a sign of ejecta-circumstellar interaction. The spectra of SN 2014cy exhibit strong absorption profile of H i similar to normal luminosity events whereas strong metal lines akin to sub-luminous SNe. The analytical modelling of the bolometric light curve of the three events yields similar progenitor radii within errors (478, 507, and 660 R ⊙ for SNe 2014cx, 2014cy, and 2015cz, respectively), a range of ejecta masses (15.0, 22.2, and 20.6 M ⊙ for SNe 2014cx, 2014cy, and 2015cz), and a modest range of explosion energies (3.3–7.2 foe where 1 foe=10 51erg).
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7.
  • De, Kishalay, et al. (författare)
  • The Zwicky Transient Facility Census of the Local Universe. I. Systematic Search for Calcium-rich Gap Transients Reveals Three Related Spectroscopic Subclasses
  • 2020
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 905:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Using the Zwicky Transient Facility alert stream, we are conducting a large spectroscopic campaign to construct a complete, volume-limited sample of transients brighter than 20 mag, and coincident within 100 '' of galaxies in the Census of the Local Universe catalog. We describe the experiment design and spectroscopic completeness from the first 16 months of operations, which have classified 754 supernovae. We present results from a systematic search for calcium-rich gap transients in the sample of 22 low-luminosity (peak absolute magnitude M > -17), hydrogen-poor events found in the experiment. We report the detection of eight new events, and constrain their volumetric rate to greater than or similar to 15% +/- 5% of the SN Ia rate. Combining this sample with 10 previously known events, we find a likely continuum of spectroscopic properties ranging from events with SN Ia-like features (Ca-Ia objects) to those with SN Ib/c-like features (Ca-Ib/c objects) at peak light. Within the Ca-Ib/c events, we find two populations distinguished by their red (g - r approximate to 1.5 mag) or green (g - r approximate to 0.5 mag) colors at the r-band peak, wherein redder events show strong line blanketing features and slower light curves (similar to Ca-Ia objects), weaker He lines, and lower [Ca II]/[O I] in the nebular phase. We find that all together the spectroscopic continuum, volumetric rates, and striking old environments are consistent with the explosive burning of He shells on low-mass white dwarfs. We suggest that Ca-Ia and red Ca-Ib/c objects arise from the double detonation of He shells, while green Ca-Ib/c objects are consistent with low-efficiency burning scenarios like detonations in low-density shells or deflagrations.
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8.
  • Fiore, Achille, et al. (författare)
  • Detailed spectrophotometric analysis of the superluminous and fast evolving SN 2019neq
  • 2024
  • Ingår i: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 527:3, s. 6473-6494
  • Tidskriftsartikel (refereegranskat)abstract
    • SN 2019neq was a very fast evolving superluminous supernova. At a redshift z = 0.1059, its peak absolute magnitude was −21.5 ± 0.2 mag in g band. In this work, we present data and analysis from an extensive spectrophotometric follow-up campaign using multiple observational facilities. Thanks to a nebular spectrum of SN 2019neq, we investigated some of the properties of the host galaxy at the location of SN 2019neq and found that its metallicity and specific star formation rate are in a good agreement with those usually measured for SLSNe-I hosts. We then discuss the plausibility of the magnetar and the circumstellar interaction scenarios to explain the observed light curves, and interpret a nebular spectrum of SN 2019neq using published SUMO radiative-transfer models. The results of our analysis suggest that the spin-down radiation of a millisecond magnetar with a magnetic field B ≃ 6×1014 G could boost the luminosity of SN 2019neq.
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9.
  • Fremling, C., et al. (författare)
  • ZTF18aalrxas : A Type IIb Supernova from a Very Extended Low-mass Progenitor
  • 2019
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 878:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate ZTF18aalrxas, a double-peaked Type IIb core-collapse supernova (SN) discovered during science validation of the Zwicky Transient Facility. ZTF18aalrxas was discovered while the optical emission was still rising toward the initial cooling peak (0.7 mag over 2 days). Our observations consist of multi-band (ultraviolet and optical) light curves (LCs), and optical spectra spanning from approximate to 0.7 to approximate to 480 days past the explosion. We use a Monte-Carlo based non-local thermodynamic equilibrium model that simultaneously reproduces both the Ni-56-powered bolometric LC and our nebular spectrum. This model is used to constrain the synthesized radioactive nickel mass (0.17 M-circle dot) and the total ejecta mass (1.7 M-circle dot) of the SN. The cooling emission is modeled using semi-analytical extended envelope models to constrain the progenitor radius (790-1050 R-circle dot) at the time of explosion. Our nebular spectrum shows signs of interaction with a dense circumstellar medium (CSM), and this spectrum is modeled and analyzed to constrain the amount of ejected oxygen (0.3-0.5 M-circle dot) and the total hydrogen mass (approximate to 0.15 M-circle dot) in the envelope of the progenitor. The oxygen mass of ZTF18aalrxas is consistent with a low (12-13 M-circle dot) zero-age main-sequence mass progenitor. The LCs and spectra of ZTF18aalrxas are not consistent with massive single-star SN Type IIb progenitor models. The presence of an extended hydrogen envelope of low mass, the presence of a dense CSM, the derived ejecta mass, and the late-time oxygen emission can all be explained in a binary model scenario.
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10.
  • Gangopadhyay, Anjasha, et al. (författare)
  • Optical studies of two stripped-envelope supernovae – SN 2015ap (Type Ib) and SN 2016P (Type Ic)
  • 2020
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 497:3, s. 3770-3789
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the photometric and spectroscopic studies of a Type Ib SN 2015ap and a Type Ic SN 2016P. SN 2015ap is one of the bright (MV = −18.04 mag) Type Ib while SN 2016P lies at an average value among the Type Ic SNe (MV = −17.53 mag). Bolometric light-curve modelling of SNe 2015ap and 2016P indicates that both the SNe are powered by 56Ni + magnetar model with 56Ni masses of 0.01 and 0.002 M⊙, ejecta masses of 3.75 and 4.66 M⊙, spin period P0 of 25.8 and 36.5 ms, and magnetic field Bp of 28.39 × 1014 and 35.3 × 1014 G, respectively. The early spectra of SN 2015ap show prominent lines of He with a ‘W’ feature due to Fe complexes while other lines of Mg ii, Na i, and Si ii are present in both SNe 2015ap and 2016P. Nebular phase [O i] profile indicates an asymmetric profile in SN 2015ap. The [O i]/[Ca ii] ratio and nebular spectral modelling of SN 2015ap hint towards a progenitor mass between 12 and 20 M⊙.
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  • Resultat 1-10 av 38

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