New adventures of Uncatchables. Sergei Popov, Bettina Posselt (astro-ph/0609275 and work in progress). Population of close-by young NSs. Abstract. We present preliminary results of a new model of population synthesis of close-by young isolated neutron stars.
Sergei Popov, Bettina Posselt
(astro-ph/0609275 and work in progress)
close-by young NSsAbstract
We present preliminary results of a new model of population synthesis of close-by young isolated neutron stars.
In comparison with the previous models we include detailed initial distribution of NS progenitors and detailed distribution of the ISM. In addition we tried to vary NS mass spectrum and modified the procedure of calculating absorbed ROSAT flux.
The results suggest that new isolated cooling neutron stars should we searched at count rates 0.01<cts/s<0.1 in the direction of rich OB associations behind the Gould Belt. These sources are expected to be younger, and so hotter, than the Magnificent Seven.
Where are the rest?
Log N – Log S for close-by ROSAT NSs can be explained by standard cooling curves taking into account the Gould Belt.
Log N – Log S can be used as an additional test of cooling curves
More than ½ are in
+/- 12 degrees from
the galactic plane.
19% outside +/- 30o
12% outside +/- 40o
1. Spatial distribution of progenitor stars
Solid – new initial XYZ
Dashed – Rbelt = 500 pc
Dotted – Rbelt = 300 pc
a) Hipparcos stars up to 500 pc
[Age: spectral type & cluster age (OB ass)]
b) 49 OB associations: birth rate ~ Nstar
c) Field stars in the disc up to 3 kpc
2. New cross sections & abundances
and new mass spectrum
Low mass stars masses are
Solid – new abundances, old mass
Dotted – old abundances, old mass
Dashed – new abundances, new mass
3. Spatial distribution of ISM (NH)
instead of :
Dot-dashed and dot-dot-dashed lines
represent two new models of the
1 < cts/s < 10
0.1 < cts/s < 1
0.01 < cts/s < 0.1
We do not expect to find much more candidates at fluxes >0.1 cts/s.
Most of new candidates should be at fluxes 0.01< f < 0.1 cts/s.
So, they are expected to be young NSs (<few 100 Mys) just outside the Belt.
I.e., they should be in nearby OB associations and clusters.
Most probable candidates are Cyg OB7, Cam OB1, Cep OB2 and Cep OB3.
Orion region can also be promising.
Name l- l+ b- b+ Dist., pcCyg OB7 84 96 -5 9 600-700Cep OB2 96 108 -1 12 700Cep OB3 108 113 1 7 700-900Cam OB1 130 153 -3 8 800-900
Born in the Gould Belt.
Born behind the Belt.