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Featured B Multiple supernovae from a star

  1. Nov 9, 2017 #1

    mfb

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    iPTF14hls was a supernova discovered in 2014. Typically they reach a brightness peak quickly and then fade over few months - but this star had several oscillations in brightness. To make it more confusing, archives from 1954 show a supernova at the same spot.

    News article
    This model can lead to multiple eruptions, but it doesn't fit well to other observations like the continuous observation of hydrogen from the star.

    Press release
    Nature article
     
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  3. Nov 9, 2017 #2
    If you do not have a subscription to Nature, here is the free preprint: https://arxiv.org/abs/1711.02671
     
  4. Nov 9, 2017 #3

    Chronos

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    Are we sure this is actually the same star recorded on the 1954 photographic plate? It appears there is no record of any spectral data for iPTF14hls prior to its most recent outburst,
     
  5. Nov 9, 2017 #4

    mfb

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    It could have been a different star that happened to be at the same spot.
    We know this star is usual even if we consider the recent observations alone, so a relation to this star doesn't sound unreasonable. If in doubt, one very weird event is more likely than one weird event plus an unrelated freak coincidence.
     
  6. Nov 10, 2017 #5

    wolram

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    <Moderator's note: eventual redundancies due to merger.>

    I can not see why this star should be different from the probably thousands of a similar mass in the universe,
    Do we have to reconsider the mass of a star that will form a Black Hole?

    https://www.sciencedaily.com/releases/2017/11/171108131839.htm

    Supernovae, the explosions of stars, have been observed in the thousands and in all cases they marked the death of a star.

    But in a study published today in the journal Nature, the team discovered a remarkable exception; a star that exploded multiple times over a period of more than fifty years. Their observations, which include data from Keck Observatory on Maunakea, Hawaii, are challenging existing theories on these cosmic catastrophes.
     
    Last edited by a moderator: Nov 10, 2017
  7. Nov 10, 2017 #6
    A second supernova is impossible. After a supernova the only thing that is left is either a neutron star or a black hole.

    I'm just tossing out a few possibilities here with out knowing a lot and also being new to astrophysics: Binary star that just has it's twin die. Light from a supernova somewhere else being bent by curved space-time to appear in the same spot.
     
  8. Nov 10, 2017 #7

    mfb

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    That doesn't explain the multiple fluctuations since 2014.
    Two supernovae at the same spot (within the angular resolution) wouldn't have gotten any attention, as that can happen by random chance once in a while. The clear structure since 2014 is the key point.
    That doesn't work, and it wouldn't be necessary anyway. There are many stars within the resolution of the 1954 observations.
     
  9. Nov 10, 2017 #8
    It would appear that they were unsure how to classify the 1954 supernova.
    The supernova lasted between 45 and 50 days after peak brightness. It was also suggested that the progenitor may have been an OB-type star, except that it lacked the hydrogen lines and was dominated by helium in its spectra.

    The hydrogen detected in the spectra of iPTF14hls would suggest that it is not the same star as the 1954 supernova.

    Source: The Spectrum of the Supernova of 1954 in NCG 4214 - Publications of the Astronomical Society of the Pacific, Volume 75, Number 443, April 1963
     
    Last edited: Nov 10, 2017
  10. Nov 10, 2017 #9
    How about a Thorne–Żytkow object?

    I know that when a neutron star siphons material from a companion it becomes an X-ray pulsar (Be X-ray binary) during that period, but what if the neutron star periodically shed this outer layer of material from its companion in a similar manner as a white dwarf that has exceeded the Chandrasekhar limit? Normally there is nothing left of the white dwarf after a Type Ia supernova, but would that process also apply to a neutron star?
     
  11. Nov 13, 2017 #10
    The phenomena of interest, I believe, is the "pulsational pair instability" which is driven by pressure changes through spontaneous symmetry breakings at the high energies.
    From what I understand this causes a hiccough similar to a nova (not supernova) but is sourced from deeper within the core. Outer layers of materia can be ejected, but there remains sufficient mass and pressure to prevent either full supernova or collapse.

    Maybe similarly massive stars of equivalent temperatures may one day be observed to exhibit similar effects.
     
  12. Nov 14, 2017 at 12:07 PM #11
    Haven't read through this entire thread, but reading the initial post, I would like to point out that a supernova within a binary star system will lead to oscillations in magnitude.
     
  13. Nov 14, 2017 at 9:18 PM #12

    mfb

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    If these stars are somewhat frequent in today’s universe, Gaia should find many of them. About 10 observations per year won’t be sufficient to follow the curves in detail, but enough to note weird behavior.
     
  14. Nov 15, 2017 at 9:24 PM #13
    Could it be that there is more than one object, not related to each other, but which just happen to be in the same line of sight.
     
  15. Nov 16, 2017 at 2:43 AM #14
    That would appear to be the case. The 1954 supernova in NGC4214 does not have the same distribution of elements in its spectrum as iPTF14hls. While iPTF14hls is rich with hydrogen, the 1954 supernova lacks hydrogen but is rich in helium. The 1954 supernova had the hallmark signature of a Type I supernova, and iPTF14hls is classified as a Type II-P supernova.
     
  16. Nov 16, 2017 at 3:20 AM #15

    BillTre

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    Could it be a series of large things (stars, gas clouds) falling into a black hole? (longer event time frame)
    What would that look like?
     
  17. Nov 16, 2017 at 7:03 AM #16

    mfb

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    5 supernovae at the same spot since 2014? Certainly not.
    The 1954 event: Maybe, see the earlier discussion.
     
  18. Nov 17, 2017 at 4:15 AM #17
    Which is why I think it has to be something unusual, like a Thorne–Żytkow object. Or perhaps instead of a neutron star at the center of a red super giant, maybe it is a black hole at the core of some super giant. Whatever it may be, it has to be able to withstand the blast of repeated supernovae and have a source of considerable mass.
     
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