New adventures of UncatchablesNew adventures of Uncatchables

Sergei Popov, Bettina Posselt(astro-ph/0609275 and work in progress)

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AbstractAbstractWe 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.

Population of Population of close-by young NSsclose-by young NSs

Where are the rest?

UNCATCHABLES

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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

More than ½ are in+/- 12 degrees from the galactic plane.19% outside +/- 30o

12% outside +/- 40o

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

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1. Spatial distribution of progenitor stars

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 improvementsPopulation sythesis – II.recent improvements

Solid – new initial XYZDashed – Rbelt = 500 pcDotted – Rbelt = 300 pc

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Population sythesis – II.recent improvementsPopulation sythesis – II.recent improvements

2. New cross sections & abundances and new mass spectrum

Solid – new abundances, old massDotted – old abundances, old massDashed – new abundances, new mass

Low mass stars masses are treated followingastro-ph/0409422

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3. Spatial distribution of ISM (NH)

instead of :

now :

Population synthesis – II.recent improvementsPopulation synthesis – II.recent improvements

Dot-dashed and dot-dot-dashed linesrepresent two new models of theISM distribution.

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b= +90°

b= -90°

Popov et al. 2005

Count rate > 0.05 cts/s

OriSco OB

Cep?Per?

PSRs+

Geminga+

M7

PSRs-

First new results: new mapsFirst new results: new maps

Clearly several richOB associations startto dominate in thespatial distribution

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

AguerosChieregato

Candidates:

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

Age

1 < cts/s < 10 0.1 < cts/s < 1 0.01 < cts/s < 0.1

Distance

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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., pc

Cyg OB7     84      96     -5     9       600-700

Cep OB2     96     108    -1   12       700

Cep OB3    108    113     1     7       700-900

Cam OB1   130    153    -3     8       800-900

0

10

-10

L=110 90130

(ads.gsfc.nasa.gov/mw/)

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Resume Resume

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?

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The Magnificent Seven Vs. UncatchablesThe Magnificent Seven Vs. Uncatchables

Born in the Gould Belt.Bright. Middle-aged.Already detected.

Born behind the Belt.Dimmer. Younger.Wanted.