1. Space Cowboys Odissey: Beyond the Gould Belt Sergei Popov, Bettina Posselt (co-authors: F. Haberl, R. Neuhauser, J. Truemper, R. Turolla) astro-ph/0609275, 0710.1547 and A&A in press

2. 2 The new zoo of neutron stars During last >10 years it became clear that neutron stars can be born very different. In particular, absolutely non-similar to the Crab pulsar. o Compact central X-ray sources in supernova remnants. o Anomalous X-ray pulsars o Soft gamma repeaters o The Magnificent Seven o Unidentified EGRET sources o Transient radio sources (RRATs) o Calvera ….

3. 3 Magnificent Seven NamePeriod, s RX 1856 7.05 RX 0720 8.39 RBS 1223 10.31 RBS 1556 6.88? RX 0806 11.37 RX 0420 3.45 RBS 1774 9.44 Radioquiet (?) Close-by Thermal emission Absorption features Long periods

4. 4 Population of close-by young NSs  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? UNCATCHABLES

5. 5 Log N – Log S Log of flux (or number counts) Log of the number of sources brighter than the given flux -3/2 sphere: number ~ r 3 flux ~ r -2 -1 disc: number ~ r 2 flux ~ r -2 calculations

6. 6 Population synthesis: ingredients  Birth rate of NSs  Initial spatial distribution  Spatial velocity (kick)  Mass spectrum  Thermal evolution  Interstellar absorption  Detector properties A brief review on population synthesis in astrophysics can be found in astro-ph/0411792 and in Physics-Uspekhi (2007). To build an artificial model of a population of some astrophysical sources and to compare the results of calculations with observations. Task:

7. 7 Gould Belt : 20 NS Myr -1 Gal. Disk (3kpc) : 250 NS Myr -1 Arzoumanian et al. 2002 ROSAT Cooling curves by Blaschke et al. Mass spectrum 18° Gould Belt Population synthesis – I.

8. 8 The Gould Belt  Poppel (1997)  R=300 – 500 pc  Age 30-50 Myrs  Center at 150 pc from the Sun  Inclined respect to the galactic plane at 20 degrees  2/3 massive stars in 600 pc belong to the Belt

9. 9 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 ~ N star c) Field stars in the disc up to 3 kpc Population synthesis – II. recent improvements We use the same normalization for NS formation rate inside 3 kpc: 270 per Myr. Most of NSs are born in OB associations. For stars <500 pc we even try to take into account if they belong to OB assoc. with known age.

10. 10 Effects of the new spatial distribution on Log N – Log S Solid – new initial XYZ Dashed – R belt = 500 pc Dotted – R belt = 300 pc There are no significant effects on the Log N – Log S distribution due to more clumpy initial distribution of NSs. But, as we’ll see below, the effect is strong for sky distribution.

11. 11 Mass spectrum of NSs  Mass spectrum of local young NSs can be different from the general one (in the Galaxy)  Hipparcos data on near-by massive stars  Progenitor vs NS mass: Timmes et al. (1996); Woosley et al. (2002) astro-ph/0305599 (masses of secondary objects in NS+NS)

12. 12 Population synthesis – II. recent improvements 2. New cross sections & abundances and new mass spectrum Low mass progenitors for the dotted mass spectrum are treated following astro-ph/0409422. The new spectrum looks more “natural”. But the effect is....

13. 13 Effects of the new mass spectrum and abundances on the Log N – Log S Solid – new abundances, old mass Dotted – old abundances, old mass Dashed – new abundances, new mass... Effect is negligible We also introduced new abundances, and calculated count rate more accurately than before. Still, the effect is small.

14. 14 3. Spatial distribution of ISM (N H ) instead of : now : Population synthesis – II. recent improvements Hakkila (see astro-ph/0609275 for details) Modification of the old one N H inside 1 kpc

15. 15 Effects of the new ISM distribution Dot-dashed and dot-dot-dashed lines Represent two new models of the ISM distribution. Again, the effect is not very significant for Log N – Log S, but it is strong for the sky distribution (see below).

16. 16 b= +90° b= -90° Popov et al. 2005 Count rate > 0.05 cts/s Ori Sco OB Cep?Per? PSRs+ Geminga+ M7 PSRs- First results: new maps Clearly several rich OB associations start to dominate in the spatial distribution

17. 17 INSs and local surrounding De Zeeuw et al. 1999 Motch et al. 2006 Massive star population in the Solar vicinity (up to 2 kpc) is dominated by OB associations. Inside 300-400 pc the Gould Belt is mostly important.

18. 18 50 000 tracks, new ISM model Agueros Chieregato Candidates: radiopulsars Magn. 7

19. 19 Age and distance distributions Age 1 < cts/s < 100.1 < cts/s < 10.01 < cts/s < 0.1 Distance New cands.

20. 20 Different models: age distributions Bars with vertical lines: old model for R belt =500 pc White bars: new initial dist Black bars: new ISM (analyt.) and new initial distribution Diagonal lines: new ISM (Hakkila) and new initial distribution

21. 21 Different models: distance distr.

22. 22 Where to search for more cowboys? 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 90 130 (ads.gsfc.nasa.gov/mw/)

23. 23 56 EGRET sources Recently Crawford et al. (astro-ph/0608225) presented a study of 56 well-identified EGRET error boxes. The idea was to find radio pulsars. Nothing was found. Obviously, they can be geminga-like sources, or represent some other subpopulation of cooling NSs.

24. 24 OB runaway stars Another possibility to find new ICoNSs is to search for (un)bound compact companions of OB runaway stars. More than one hundred OB runaway stars are known in 1 kpc around the Sun (astro-ph/9809227). Unbounded NSs Bounded NSs (for BHs done in astro-ph/0511224) bh Optical star Sayer et al. 1996 and Philp et al. 1996 looked for radio pulsars as companions of runaway stars. It is reasonable to look for M7-like companions around young OB stars.

25. 25 Calvera et al. Recently, Rutledge et al. reported the discovery of an enigmatic NS candidated dubbed Calvera. It can be an evolved (aged) version of Cas A source, but also it can be a M7-like object, who’s progenitor was a runaway (or, less probably, hypervelocity) star.

26. 26 CCO vs. M7 Gotthelf and Halpern (2007) presented evidence in favor of hypothesis that among CCOs there is a population of NSs born with long spin periods (few tenths of a second) and small magnetic fields (<10 12 G). These sources are hot. The M7 sources are hot, too, but they seem to belong to different populations. This can be explained by accreted envelopes in CCOs (Kaminker et al. 2006). It is necessary to make a general population synthesis, which would include all types of isolated NSs.

27. 27 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.  New ways to find candidates can be discussed.

28. 28 The Magnificent Seven Vs. Uncatchables Born in the Gould Belt. Bright. Middle-aged. Already observed. Born behind the Belt. Dimmer. Younger. Wanted. That’s all!

29. 29 Radio detection Malofeev et al. (2005) reported detection of 1RXS J1308.6+212708 (RBS 1223) in the low-frequency band (60-110 MHz) with the radio telescope in Pushchino. In 2006 Malofeev et al. reported radio detection of another one. (back)

30. 30 NS+NS binaries Pulsar Pulsar mass Companion mass B1913+16 1.44 1.39 B2127+11C 1.35 1.36 B1534+12 1.33 1.35 J0737-3039 1.34 1.25 J1756-2251 1.40 1.18 (PSR+companion)/2 J1518+4904 1.35 J1811-1736 1.30 J1829+2456 1.25 (David Nice, talk at Vancouver 2005) (Back)Back