Stripped-Envelope Supernova

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A stripped envelope supernova is a core collapse supernova whose spectrum shows little or no hydrogen during the eruption. The forerunner star of the supernova lost its outer atmosphere before the explosion due to strong stellar winds or due to mass transfers in close binary star systems .

Core collapse supernova

Stars counteract the gravitational force through the thermal gas pressure , whereby the temperature is a consequence of thermonuclear reactions in or near the star nuclei. In nuclear fusions , heavy elements up to iron are produced, depending on the mass of the star. Since iron has the highest binding energy of all chemical elements, the star can no longer avoid gravitational collapse by further contraction and increasing the temperature in its core. Instead, a rise in temperature generates gamma rays that destroy existing iron atoms in an endothermic reaction by means of photo-disintegration . Furthermore, the inverse beta decay generates neutrinos which, due to their small interaction cross-section, leave the star almost unhindered and thus lead to further cooling of the core. This means that the star can no longer prevent the collapse of gravity and the core collapses into a protoneutron star . This reflects the incident matter, which runs through the star as a collision front and appears as a supernova after exiting the atmosphere.

Properties of Stripped-Envelope Supernovae

In the case of some nuclear collapse supernovae, little or no hydrogen can be detected in their spectra. These stripped-envelope supernovae are further subdivided into subclasses according to their spectrum

  • IIb with strong helium lines and weak hydrogen lines
  • Ib with strong helium lines and no hydrogen lines
  • Ic, in which neither helium lines nor hydrogen lines can be detected

In the first 100 days after the eruption, the expansion speed of stripped-envelope supernovae is remarkably steady at 4,500 km / s with only minor differences from star to star. The hydrogen- poor hypernovae form a separate group, the speed of expansion of which can reach up to a tenth of the speed of light . Stripped-envelope supernovae are at the maximum with M v = −17.8 mag less light than the thermonuclear supernovae of type Ia , the fluctuation range being up to 2 mag .

Forerunner stars

Stripped-envelope supernovae occur preferentially in interacting galaxies , in which a starburst occurred a few million years ago due to the gravitational interaction between the star islands . Therefore, the precursor stars are also likely to be only a few tens of millions of years old before they explode. From the development of the radiolight curve, conclusions can be drawn about dense circumstellar matter, which, however, does not correspond to the observed density of the presumed precursor stars , the Wolf-Rayet stars .

Modulations of the radiolight curves of some stripped-envelope supernovae and spectropolarimetric observations led to the conclusion that the precursor stars were binary , according to which the outer atmosphere was transferred to a companion by mass exchange in a close binary star system. However, these conclusions are controversial. Alternatively, the outer layers could also be lost by strong stellar winds like the luminous blue variables , which can also explode directly as a supernova.

Computational simulations suggest that all precursor stars of stripped-envelope supernovae had an original mass of around 25 solar masses and lost around 20 solar masses before the explosion. In order to reproduce the observed spectra, the II-b and Ib supernovae seem to arise in interacting binary stars, since the necessary mixing can only be achieved there. The hydrogen- and helium-deficient supernovae Ic, on the other hand, seem to originate from massive single stars. While no precursor stars for type I supernovae could be identified yet, yellow hypergiants were found in two cases at the location of IIb SN , which could no longer be detected after the explosion. Since the supernovae originate from stars with a high mass, they cannot have migrated far from where they were formed. Spectroscopic observations of stars in the vicinity of Type Ib and Ic supernovae show that they are unusually metal-rich .

Related to gamma ray bursts

With a number of long gamma ray bursts , a stripped envelope supernova was observed at the same location. These show no signs of helium or hydrogen in spectra, but they are somewhat more luminous than the corresponding supernova type Ic. This connection between a subgroup of the Gamma Ray Bursts and the Stripped-Envelope Supernovae is established by the Kollapsar model. After that, a core collapse supernova leads to a gravitational collapse in a massive star, from which a proto-neutron star emerges with a rotation period in the order of one millisecond and a strong magnetic field with a magnetic flux density of more than 10 11  T. An energy of up to 10 45  J can be extracted from this proto-neutron star within a period of 100 s. Under certain conditions, this energy emerges along the axis of rotation of the massive star and accelerates a jet to relativistic speeds. If such jets are aimed at the earth, they are registered here as long-lasting gamma-ray bursts. The magnetar collapses into a black hole within a short time, probably due to relapsing matter, after crossing the Tolman-Oppenheimer-Volkoff boundary .

However, stripped envelope supernovae are probably only the cause of a subgroup of the long gamma ray bursts. So far, supernovae at the location of GRBs have only been found for faint outbreaks, the mean luminosity of which in the range of gamma radiation is a factor of 100 to 10,000 below that of distant bursts. Furthermore, the eruptions of gamma ray bursts in connection with a stripped-envelope supernova are unusually long and cannot represent the entire population of the long GRBs.

Type Ic ultra-stripped supernovae

A small group of supernovae that are discovered during surveys show the spectral properties of a stripped-envelope supernova at a luminosity that is a factor of 100 or more below a typical supernova of type Ic. Examples are SN 2005ek, SN 2010X and SN 2005E, whose ejected mass is only 0.05 to 0.2 solar masses. The properties of these ultra-stripped supernovae suggest that the gravitational collapse occurs in a star with a mass of only 1.5 solar masses. Such a helium star can develop in a close binary star system, where a star with an iron core of 1.4 solar masses and a thin helium atmosphere can form in the course of a common envelope phase. An ultra-stripped supernova could create tight double stars consisting of two neutron stars like the double pulsar system PSR 1913 + 16 .

Individual evidence

  1. ↑ Masaomi Tanaka et al .: Three-Dimensional Explosion Geometry of Stripped-Envelope Core-Collapse Supernovae. I. Spectropolarimetric Observations . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1205.4511v1 .
  2. ↑ SM Habergham, PA James, JP Anderson: A Central Excess of Stripped-Envelope Supernovae within Disturbed Galaxies . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1205.6732v1 .
  3. ^ JI Maurer et al .: Characteristic Velocities of Stripped-Envelope Core-Collapse Supernova Cores . In: Astrophysics. Solar and Stellar Astrophysics . 2009, arxiv : 0911.3774v1 .
  4. ^ Dean Richardson, David Branch and E. Baron: Absolute-Magnitude Distributions and Light Curves of Stripped-Envelope Supernovae . In: Astrophysics. Solar and Stellar Astrophysics . 2006, arxiv : astro-ph / 0601136v1 .
  5. ↑ Keiichi Maeda: PROBING SHOCK BREAKOUT AND PROGENITORS OF STRIPPED-ENVELOPE SUPERNOVAE THROUGH THEIR EARLY RADIO EMISSIONS . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1209.1904v2 .
  6. ↑ Stuart D. Ryder et al .: Modulations in the radio light curve of the Type IIb Supernova 2001ig: Evidence for a Wolf-Rayet binary progenitor? In: Astrophysics. Solar and Stellar Astrophysics . 2004, arxiv : astro-ph / 0401035v1 .
  7. ^ Jose H. Groh, Georges Meynet, and Sylvia Ekström: Massive star evolution: Luminous Blue Variables as unexpected Supernova progenitors . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1301.1519 .
  8. ↑ Luc Dessart et al .: On the nature of supernovae Ib and Ic . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1205.5349v1 .
  9. ^ M. Ergon et al .: Optical and near-infrared observations of SN 2011dh - The first 100 days . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1305.1851v1 .
  10. ↑ Mamoru Doi et al .: INTEGRAL FIELD SPECTROSCOPY OF SUPERNOVA EXPLOSION SITES: CONSTRAINING MASS AND METALLICITY OF THE PROGENITORS - I. TYPE IB AND IC SUPERNOVAE . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1305.1105v1 .
  11. ^ Jens Hjorth: The supernova / gamma-ray burst / jet connection . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1304.7736v1 .
  12. ^ N. Bucciantini: Magnetars and Gamma Ray Bursts . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1204.2658 .
  13. ^ AJ Levan et al .: Hubble Space Telescope observations of the afterglow, supernova and host galaxy associated with the extremely bright GRB 130427A . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1307.5338v1 .
  14. ↑ TM Tauris, N. Langer, TJ Moriya, Ph. Podsiadlowski, S.-C. Yoon, SI Blinnikov: Ultra-stripped Type Ic supernovae from close binary evolution . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1310.6356v1 .