Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>In the current era of time-domain astronomy, it is increasingly important to have rigorous, data-driven models for classifying transients, including supernovae. We present the first application of principal component analysis to the photospheric spectra of stripped-envelope core-collapse supernovae. We use one of the largest compiled optical data sets of stripped-envelope supernovae, containing 160 SNe and 1551 spectra. We find that the first five principal components capture 79% of the variance of our spectral sample, which contains the main families of stripped supernovae: Ib, IIb, Ic, and broad-lined Ic. We develop a quantitative, data-driven classification method using a support vector machine, and explore stripped-envelope supernovae classification as a function of phase relative to <jats:italic>V</jats:italic>-band maximum light. Our classification method naturally identifies “transition” supernovae and supernovae with contested labels, which we discuss in detail. We find that the stripped-envelope supernovae types are most distinguishable in the later phase ranges of 10 ± 5 days and 15 ± 5 days relative to <jats:italic>V</jats:italic>-band maximum, and we discuss the implications of our findings for current and future surveys such as Zwicky Transient Factory and Large Synoptic Survey Telescope.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In the highly dynamic chromosphere, there exist many kinds of small-scale activities, such as spicules, surges, and Ellerman bombs. Here, we report the discovery of a new phenomenon in the chromosphere observed with the New Vacuum Solar Telescope at the Fuxian Solar Observatory. In the high tempo-spatial-resolution H<jats:italic>α</jats:italic> images, some dark or bright structures are found to fly along the curved trajectory, looking like cannonballs. Their average size, mass, and velocity are about 1.5 × 10<jats:sup>9</jats:sup> km<jats:sup>3</jats:sup>, 1.5 × 10<jats:sup>8</jats:sup> kg, and 56 km s<jats:sup>−1</jats:sup>, respectively. In the simultaneous (extreme-)ultraviolet images obtained by the <jats:italic>Solar Dynamics Observatory</jats:italic>, these cannonballs appear as brighter features compared to the surrounding area, implying that there exists some kind of heating during this process. The photospheric magnetograms show the magnetic flux emergence and interaction with the pre-existing fields. These observations reveal that the cannonballs are chromospheric material blobs launched due to the magnetic reconnection between emerging magnetic flux and the pre-existing loops.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this Letter we present the result of an axisymmetric core-collapse supernovae simulation conducted with appropriate treatments of neutrino transport and proper motions of proto-neutron stars (PNSs), in which a remarkable PNS acceleration is observed in association with asymmetric neutrino emissions 300 ms after bounce. We find that these asymmetric neutrino emissions play important roles in the acceleration of PNSs in this phase. The correlation between the PNS proper motion and the asymmetric ejecta is similar to that in a neutron star (NS) kick of hydrodynamic origin. Both electron-type neutrinos (<jats:italic>ν</jats:italic> <jats:sub>e</jats:sub>) and their anti-particles (<jats:inline-formula> <jats:tex-math> <?CDATA ${\bar{\nu }}_{{\rm{e}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlab30caieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) have a ∼10% level of asymmetry between the northern and southern hemispheres, while other heavy-leptonic neutrinos (<jats:italic>ν</jats:italic> <jats:sub> <jats:italic>x</jats:italic> </jats:sub>) have much a smaller asymmetry of ∼1%. The emissions of <jats:inline-formula> <jats:tex-math> <?CDATA ${\bar{\nu }}_{{\rm{e}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlab30caieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:italic>ν</jats:italic> <jats:sub> <jats:italic>x</jats:italic> </jats:sub> are higher in the hemisphere of stronger shock expansion, whereas the <jats:italic>ν</jats:italic> <jats:sub>e</jats:sub> emission is enhanced in the opposite hemisphere: in total, the neutrinos carry some linear momentum to the hemisphere of the stronger shock expansion. This asymmetry is attributed to the non-spherical distribution of electron-fraction (<jats:italic>Y</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>) in the envelope of PNS. Although it is similar to lepton-emission self-sustained asymmetry, the <jats:italic>Y</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> asymmetry seems to be associated with the PNS motion: the latter triggers lateral circular motions in the envelope of PNS by breaking the symmetry of the matter distribution there, which is then sustained by a combination of convection, lateral neutrino diffusion, and matter-pressure gradient. Our findings may have an influence on the current theories on the NS kick mechanism, although long-term simulations are required to assess their impact on later evolution.</jats:p>