Image 1: Artist impression of a magnetar boosting a super-luminous supernova and gamma-ray burst
Credit: Kavli IPMU
Image 3:
Light curves of ASASSN-15lh and SN 2011kl compared with normal
supernovae SN 1999em and SN 1987A.
Credit: Bersten et al.
Calculations by scientists have found highly magnetized, rapidly spinning neutron stars called magnetars could explain the energy source behind two extremely unusual stellar explosions.
Stellar explosions known as supernovae usually
shine a billion times brighter than the Sun. Super-luminous supernovae
(SLSNe) are a relatively new and rare class of stellar explosions, 10 to
100 times brighter than normal supernovae. But the energy source of
their super-luminosity, and explosion mechanisms are a mystery and
remain controversial amongst scientists.
A group of researchers led by Melina Bersten, an
Instituto de Astrofisica de La Plata Researcher and affiliate member of
Kavli IPMU, and including Kavli IPMU Principal Investigator Ken'ichi
Nomoto, tested a model that suggests that the energy to power the
luminosity of two recently discovered SLSNe, SN 2011kl and ASASSN-15lh,
is mainly due to the rotational energy lost by a newly born magnetar.
They analyzed two recently discovered super-luminous supernovae: SN
2011kl and ASASSN-15lh.
“These supernovae can be found in very distant
universe, thus possibly informing us the properties of the first stars
of the universe,” said Nomoto.
Interestingly, both explosions were found to be
extreme cases of SLSNe. First, SN 2011kl was discovered in 2011 and is
the first supernovae to have an ultra long gamma-ray burst that lasted
several hours, whereas typical long-duration gamma-ray bursts fade in a
matter of minutes. The second, ASASSN-15lh, was discovered in 2015 and
is possibly the most luminous and powerful explosion ever seen, more
than 500 times brighter than normal supernovae. For more than a month
its luminosity was 20 times brighter than the whole Milky Way galaxy.
The team performed numerical hydrodynamical calculations to explore
the magnetar hypothesis, and found both SLSNe could be understood in the
framework of magnetar-powered supernovae (see image 1). In particular,
for ASASSN-15lh, they were able to find a magnetar source with
physically allowed properties of magnetic field strength and rotation
period. The solution avoided the prohibited realm of neutro-star spins
that would cause the object to breakup due to centrifugal forces.
“These two extreme super-luminous supernovae put to the test our knowledge of stellar explosions,” said Bersten.
To confirm the team’s calculations, further
observations would need to be carried out when the material ejected by
the supernova is expected to become thin. The most powerful telescopes,
including the Hubble Space Telescope, will be required for this purpose.
If correct, these observations will allow scientists to probe the inner
part of an exploding object, and provide new insight on its origin, and
evolution of stars in the Universe.
The group’s paper was published in The Astrophysical Journal Letters in January.
Paper details
Journal: Astrophysical Journal Letters
Title: The Unusual Superluminous Supernovae SN2011KL and ASASSN-15LH
Authors: Melina C. Bersten (1,2,3) , Omar G. Benvenuto (1,2,4) , Mariana Orellana (5,6) , and Ken'ichi Nomoto (3,7)
Author affiliations:
1. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo
del Bosque S/N, B1900FWA La Plata, Argentina
2. Instituto de Astrofísica de La Plata (IALP) , CONICET, Argentina
3. Kavli Institute for the Physics and Mathematics of the Universe, The University of
Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583, Japan
4. Member of the Carrera del Investigador Científico de la Comisión de Investigaciones
Científicas de la Provincia de Buenos Aires (CIC), Argentina
5. Sede Andina, Universidad Nacional de Río Negro, Mitre 630 (8400) Bariloche, Argentina
6. Member of the Carrera del Investigador Científico y Tecnológico del CONICET, Argentina
7. Hamamatsu Professor.
DOI: 10.3847/2041-8205/817/1/L8 (Published 20 January, 2016)
Paper abstract (Astrophysical Journal Letters)
Preprint (arXiv.org)
Media contact:
Motoko Kakubayashi
Press Officer
Kavli Institute for the Physics and Mathematics of the Universe
The University of Tokyo Institutes for Advanced Study,
The University of Tokyo
TEL: +81-04-7136-5980
E-mail: press@ipmu.jp
Research contact:
Ken'ichi Nomoto
Principal Investigator and Project Professor Kavli Institute for the Physics and Mathematics of the Universe
TEL: +81-04-7136-6567
E-mail: nomoto@astron.s.u-tokyo.ac.jp
Melina C. Bersten
Researcher
Instituto de Astrofisica de La Plata
Affiliate member
Kavli Institute for the Physics and Mathematics of the Universe
E-mail: merlinada.bersten@gmail.com
Useful links
All images can be downloaded from this page: http://web.ipmu.jp/press/201603-Magnetar
