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Sökning: WFRF:(Phinney E. S.)

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  • Miller, A. A., et al. (författare)
  • The Spectacular Ultraviolet Flash from the Peculiar Type Ia Supernova 2019yvq
  • 2020
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 898:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Early observations of Type Ia supernovae (SNe Ia) provide essential clues for understanding the progenitor system that gave rise to the terminal thermonuclear explosion. We present exquisite observations of SN 2019yvq, the second observed SN Ia, after iPTF 14atg, to display an early flash of emission in the ultraviolet (UV) and optical. Our analysis finds that SN 2019yvq was unusual, even when ignoring the initial flash, in that it was moderately underluminous for an SN Ia ( mag at peak) yet featured very high absorption velocities ( km s−1 for Si ii λ6355 at peak). We find that many of the observational features of SN 2019yvq, aside from the flash, can be explained if the explosive yield of radioactive 56Ni is relatively low (we measure ) and it and other iron-group elements are concentrated in the innermost layers of the ejecta. To explain both the UV/optical flash and peak properties of SN 2019yvq we consider four different models: interaction between the SN ejecta and a nondegenerate companion, extended clumps of 56Ni in the outer ejecta, a double-detonation explosion, and the violent merger of two white dwarfs. Each of these models has shortcomings when compared to the observations; it is clear additional tuning is required to better match SN 2019yvq. In closing, we predict that the nebular spectra of SN 2019yvq will feature either H or He emission, if the ejecta collided with a companion, strong [Ca ii] emission, if it was a double detonation, or narrow [O i] emission, if it was due to a violent merger.
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3.
  • Burdge, Kevin B., et al. (författare)
  • A 62-minute orbital period black widow binary in a wide hierarchical triple
  • 2022
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 605:7908, s. 41-45
  • Tidskriftsartikel (refereegranskat)abstract
    • Over a dozen millisecond pulsars are ablating low-mass companions in close binary systems. In the original 'black widow', the eight-hour orbital period eclipsing pulsar PSR J1959+2048 (PSR B1957+20)(1), high-energy emission originating from the pulsar2 is irradiating and may eventually destroy(3) a low-mass companion. These systems are not only physical laboratories that reveal the interesting results of exposing a close companion star to the relativistic energy output of a pulsar, but are also believed to harbour some of the most massive neutron stars(4), allowing for robust tests of the neutron star equation of state. Here we report observations of ZTF J1406+1222, a wide hierarchical triple hosting a 62-minute orbital period black widow candidate, the optical flux of which varies by a factor of more than ten. ZTF J1406+1222 pushes the boundaries of evolutionary models(5), falling below the 80-minute minimum orbital period of hydrogen-rich systems. The wide tertiary companion is a rare low-metallicity cool subdwarf star, and the system has a Galactic halo orbit consistent with passing near the Galactic Centre, making it a probe of formation channels, neutron star kick physics(6) and binary evolution.
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4.
  • Kool, Erik C., et al. (författare)
  • SN 2020bqj : A Type Ibn supernova with a long-lasting peak plateau
  • 2021
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 652
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Type Ibn supernovae (SNe Ibn) are a rare class of stripped envelope supernovae interacting with a helium-rich circumstellar medium (CSM). The majority of the SNe Ibn reported in the literature display a surprising homogeneity in their fast-evolving lightcurves and are typically found in actively starforming spiral galaxies.Aims. We present the discovery and the study of SN 2020bqj (ZTF20aalrqbu), a SN Ibn with a long-duration peak plateau lasting 40 days and hosted by a faint low-mass galaxy. We aim to explain its peculiar properties using an extensive photometric and spectroscopic data set.Methods. We compare the photometric and spectral evolution of SN 2020bqj with regular SNe Ibn from the literature, as well as with other outliers in the SN Ibn subclass. We fit the bolometric and multi-band lightcurves with powering mechanism models such as radioactive decay and CSM interaction. We also model the host galaxy of SN 2020bqj.Results. The risetime, peak magnitude and spectral features of SN 2020bqj are consistent with those of most SNe Ibn, but the SN is a clear outlier in the subclass based on its bright, long-lasting peak plateau and the low mass of its faint host galaxy. We show through modeling that the lightcurve of SN 2020bqj can be powered predominantly by shock heating from the interaction of the SN ejecta and a dense CSM, combined with radioactive decay. The peculiar Type Ibn SN 2011hw is a close analog to SN 2020bqj in terms of lightcurve and spectral evolution, suggesting a similar progenitor and CSM scenario. In this scenario a very massive progenitor star in the transitional phase between a luminous blue variable and a compact Wolf-Rayet star undergoes core-collapse, embedded in a dense helium-rich CSM with an elevated opacity compared to normal SNe Ibn, due to the presence of residual hydrogen. This scenario is consistent with the observed properties of SN 2020bqj and the modeling results.Conclusions. SN 2020bqj is a compelling example of a transitional SN Ibn/IIn based on not only its spectral features, but also its lightcurve, host galaxy properties and the inferred progenitor properties. The strong similarity with SN 2011hw suggests this subclass may be the result of a progenitor in a stellar evolution phase that is distinct from those of progenitors of regular SNe Ibn.
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5.
  • Anderson, M. M., et al. (författare)
  • Caltech-NRAO Stripe 82 Survey (CNSS). III. The First Radio-discovered Tidal Disruption Event, CNSS J0019+00
  • 2020
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 903:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the discovery of a nuclear transient with the Caltech-NRAO Stripe 82 Survey (CNSS), a dedicated radio transient survey carried out with the Karl G. Jansky Very Large Array (VLA). This transient, CNSS J001947.3+003527, exhibited a turn-on over a timescale of less than or similar to 1 yr, increasing in flux density at 3 GHz from <0.14 mJy in 2014 February to 4.4 0.1 mJy in 2015 March, reaching a peak luminosity of around 2015 October. The association of CNSS J0019+00 with the nucleus (Gaia and our very-long baseline interferometry positions are consistent to within 1 pc) of a nearby S0 Seyfert galaxy at 77 Mpc, together with the radio spectral evolution, implies that this transient is most likely a tidal disruption event (TDE). Our equipartition analysis indicates the presence of a similar to 15,000 km s(-1) outflow, having energy similar to 10(49) erg. We derive the radial density profile for the circumnuclear material in the host galaxy to be proportional to R-2.5. All of these properties suggest resemblance with radio-detected thermal TDEs like ASASSN-14li and XMMSL1 J0740-85. No significant X-ray or optical emission is detected from CNSS J0019+00, although this may simply be due to the thermal emission being weak during our late-time follow-up observations. From the CNSS survey we have obtained the first unbiased measurement of the rate of radio TDEs, R(>500 mu Jy) of about 2 x 10(-3) deg(-2), or equivalently a volumetric rate of about 10 Gpc(-3) yr(-1). This rate implies that all-sky radio surveys such as the VLA Sky Survey and those planned with ASKAP, will find many tens of radio TDEs over the next few years.
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