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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.

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New adventures of uncatchables

New adventures of Uncatchables

Sergei Popov, Bettina Posselt

(astro-ph/0609275 and work in progress)


Population of

close-by young NSs


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.

  • Magnificent seven

  • Geminga and 3EG J1853+5918

  • Four radio pulsars with thermal emission (B0833-45; B0656+14; B1055-52; B1929+10)

  • Seven older radio pulsars, without detected thermal emission.

Where are the rest?


Some old results of pop synthesis i log n log s and spatial distribution
Some old results of Pop. Synthesis-I:Log N – Log S and spatial distribution

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

Population sythesis ii recent improvements
Population sythesis – II.recent improvements

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

Population sythesis ii recent improvements1
Population sythesis – II.recent improvements

2. New cross sections & abundances

and new mass spectrum

Low mass stars masses are

treated following


Solid – new abundances, old mass

Dotted – old abundances, old mass

Dashed – new abundances, new mass

Population synthesis ii recent improvements
Population synthesis – II.recent improvements

3. Spatial distribution of ISM (NH)

instead of :

now :

Dot-dashed and dot-dot-dashed lines

represent two new models of the

ISM distribution.

First new results new maps

Popov et al. 2005

Count rate > 0.05 cts/s

b= +90°


Sco OB


b= -90°





First new results: new maps

Clearly several rich

OB associations start

to dominate in the

spatial distribution

First new results 50 000 tracks new ism model
First new results:50 000 tracks, new ISM model




First new results age and distance distributions
First new results:Age and distance distributions

1 < cts/s < 10

0.1 < cts/s < 1

0.01 < cts/s < 0.1



Where to search for more cavaliers
Where to search for more cavaliers?

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









  • New more detailed population synthesis model for local population of isolated NS is made

  • New results provide a hint to search for new coolers.

  • We predict that new objects can be identified at 0.01<cts/s<0.1 behind the Gould Belt in the directions of close-by rich OB associations, in particular Cep OB2.

  • These objects are expected to be younger and hotter than the Magnificent seven. Task for eRosita?

New adventures of uncatchables

The Magnificent Seven Vs. Uncatchables

Born in the Gould Belt.

Bright. Middle-aged.

Already detected.

Born behind the Belt.

Dimmer. Younger.