X-ray Dim Isolated Neutron Stars

X-ray Dim Isolated Neutron Stars (XDINS, German  X-ray weak isolated neutron stars ) are neutron stars with a purely thermal x-ray radiation , and a luminescence of 10 ³⁰ and 10 ³² Erg ^-1 . The XDINS are probably neutron stars between 100,000 and 1,000,000 years old that are slowly cooling. An alternative name is X-ray Thermal Neutron Stars , or XTINS for short.

properties

The X-ray spectrum corresponds to that of a black body radiation with a temperature between 40 and 100 electron volts . The X-ray radiation is very stable over longer periods of time with an upper limit of two percent, while very weak pulses with periods between 2 and 12 seconds were found. This is interpreted as the period of rotation of the neutron stars. From the slowdown of the rotation period of 10 ⁻¹⁴ s / s, a magnetic flux density of around 10 ¹³ Gauss has been deduced and a statistical spin-down age of one million years has been calculated. The luminosity in the optical spectral range is at least 10,000 times weaker than in the X-ray range. By definition, XDINS are not associated with a supernova remnant , as these neutron stars are known as Central Compact Objects in Supernova Remnants . The XDINS are also not rotating radio transient , since even long integrating radio observations show no signs of radio emission. All known XDINS show a high intrinsic motion, which suggests a relatively short distance of less than 500 parsecs . In contrast to the rotation-driven pulsars, the Isolated Neutron Stars emit more electromagnetic radiation than they gain from slowing down the rotation.

The origin of the XDINS can be calculated from the proper motion and the shock wave in the interstellar medium . They arise in nearby OB associations and their high space velocity is probably the result of a supernova explosion that created these neutron stars. The distance traveled confirms the typical age of 500,000 years for this class of Isolated Neutron Stars . It is assumed that XDINS could be the successors of the magnetars , whose magnetic field has decayed to such an extent that they can no longer generate eruptions in the form of soft gamma repeaters and unusual X-ray pulsars.

Significance for astrophysics

Since, in contrast to pulsars , X-ray pulsars and magnetars, with the XDINS the naked neutron star can be observed in a binary star system without any interaction with a magnetic field or a companion , they have a better possibility of using the equation of state of matter at densities around 10 ¹² kg / cm ³ to analyze. From the equation of state, the not yet precisely known upper mass limit of neutron stars, the Tolman-Oppenheimer-Volkoff limit , can also be better limited. In addition, the spatial density of the neutron stars can be better derived because, in contrast to the other observable types of neutron stars, the XDINS are isotropic emitters and their detection probability does not depend on the magnetic flux density .

Examples

• RX J1856-3754

Individual evidence

1. ↑ VI Kondratiev et al .: X-ray Dim Isolated Neutron Stars . In: Astrophysics. Solar and Stellar Astrophysics . 2009, arxiv : 0907.0054 .
2. ↑ Ramandeep Gill and Jeremy S. Heyl: Statistical ages and the cooling rate of X-ray dim isolated neutron stars . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1305.0930v1 .
3. ↑ SB Popov: The Zoo of Neutron Stars . In: Astrophysics. Solar and Stellar Astrophysics . 2006, arxiv : astro-ph / 0610593 .
4. ^ Adriana Mancini Pires: Peculiar isolated neutron stars and the source in the Carina Nebula . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1206.3494 .
5. ↑ Alice K. Harding: The Neutron Star Zoo . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1302.0869v1 .
6. ^ RP Mignani et al .: The birthplace and age of RX J1856.5 −3754 . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1212.3141 .
7. ↑ Sandro Mereghetti: X-ray emission from isolated neutron stars . In: Astrophysics. Solar and Stellar Astrophysics . 2010, arxiv : 1008.2891 .