New adventures of Uncatchables Sergei Popov Bettina Posselt
New adventures of Uncatchables Sergei Popov, Bettina Posselt (astro-ph/0609275 and work in progress)
Plan of the talk Ü Ü Ü 1. 2. 3. Ü Ü Intro. Pop. synthesis Some old results New improvements Initial distribution Mass spectrum and abundances ISM distribution Maps Age and distance distributions Where to search? Final conclusions 2
Magnificent Seven Name RX 1856 RX 0720 RBS 1223 RBS 1556 RX 0806 RX 0420 RBS 1774 Period, s 8. 39 10. 31 6. 88? 11. 37 3. 45 9. 44 Radioquiet (? ) Close-by Thermal emission Absorption features Long periods 3
Population of close-by young NSs Ü Magnificent seven Ü Geminga and 3 EG J 1853+5918 Ü Four radio pulsars with thermal emission (B 0833 -45; B 0656+14; B 105552; B 1929+10) Ü Seven older radio pulsars, without detected thermal emission. Where are the rest? UNCATCHABLES 4
Population synthesis: ingredients Ü Birth rate of NSs Ü Initial spatial distribution Ü Spatial velocity (kick) Ü Mass spectrum Ü Thermal evolution Ü Interstellar absorption Task: To build an artificial model of a population of some astrophysical sources and to compare the results of calculations with observations. A brief review on population synthesis in astrophysics can be found in astro-ph/0411792 Ü Detector properties 5
Population synthesis – I. Gould Belt : 20 NS Myr-1 Gal. Disk (3 kpc) : 250 NS Myr-1 • Cooling curves by • Blaschke et al. • Mass spectrum ROSAT 18° Gould Belt Arzoumanian et al. 2002 © Bettina Posselt 6
Solar vicinity Ü Solar neighborhood is not a typical region of our Galaxy Ü Gould Belt Ü R=300 -500 pc Ü Age: 30 -50 Myrs Ü 20 -30 SN per Myr (Grenier 2000) Ü The Local Bubble Ü Up to six SN in a few Myrs 7
The Gould Belt Ü Ü Ü 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 8
Initial spatial distribution A very simple model for PS-I: The Gould Belt as a flat inclined disc plus contribution from the galactic disc up to 3 kpc. 9
Mass spectrum of NSs Mass spectrum of local young NSs can be different from the general one (in the Galaxy) Ü Hipparcos data on near-by massive stars Ü Progenitor vs NS mass: Timmes et al. (1996); Woosley et al. (2002) Ü (masses of secondary objects in NS+NS) astro-ph/0305599 10
Log of the number of sources brighter than the given flux Log N – Log S calculations -3/2 sphere: number ~ r 3 flux ~ r-2 -1 disc: number ~ r 2 flux ~ r-2 Log of flux (or number counts) 11
Some results of PS-I: Log N – Log S and spatial distribution Log N – Log S for closeby 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 +/- 30 o 12% outside +/- 40 o (Popov et al. 2005 Ap&SS 299, 117) 12
Population sythesis – II. recent improvements 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 Solid – new initial XYZ Dashed – Rbelt = 500 pc Dotted – Rbelt = 300 pc 13
Population sythesis – II. recent improvements 2. New cross sections & abundances and new mass spectrum Low mass stars are treated following astro-ph/0409422 Solid – new abundances, old mass Dotted – old abundances, old mass Dashed – new abundances, new mass 14
Population synthesis – II. recent improvements 3. Spatial distribution of ISM (NH) instead of : now : Dot-dashed and dot-dashed lines Represent two new models of the ISM distribution. 15
First results: new maps Popov et al. 2005 Count rate > 0. 05 cts/s Clearly several rich OB associations start to dominate in the spatial distribution b= +90° Cep? Per? Sco OB Ori b= -90° PSRs+ Geminga+ M 7 PSRs- 16
INSs and local surrounding 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. De Zeeuw et al. 1999 Motch et al. 2006 17
50 000 tracks, new ISM model Candidates: Agueros Chieregato 18
Age and distance distributions 1 < cts/s < 10 0. 1 < cts/s < 1 0. 01 < cts/s < 0. 1 Age Distance 19
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 OB 7, Cam OB 1, Cep OB 2 and Cep OB 3. Orion region can also be promising. Name l- l+ b- b+ Dist. , pc 130 90 L=110 10 Cyg OB 7 84 96 -5 9 600 -700 Cep OB 2 96 108 -1 12 700 0 Cep OB 3 108 113 1 7 700 -900 Cam OB 1 130 153 -3 8 800 -900 -10 (ads. gsfc. nasa. gov/mw/) 20
Resume New more detailed population synthesis model for local population of isolated NS is made Ü New results provide a hint to search for new coolers. Ü 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 OB 2. Ü These objects are expected to be younger and hotter than the Magnificent seven. Ü 21
The Magnificent Seven Vs. Uncatchables Born in the Gould Belt. Bright. Middle-aged. Already observed. Born behind the Belt. Dimmer. Younger. Wanted. I thank all scientists with whom I collaborated during different stages of work on INSs and had fruitful discussions: D. Blaschke, M. Colpi, H. Grigorian, F. Haberl, V. Lipunov, R. Neuhauser, M. Prokhorov, A. Treves, J. Trumper, …. 22
Radio detection Malofeev et al. (2005) reported detection of 1 RXS J 1308. 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) 23
NS+NS binaries Pulsar mass Companion mass B 1913+16 1. 44 1. 39 B 2127+11 C 1. 35 1. 36 B 1534+12 1. 33 1. 35 J 0737 -3039 1. 34 1. 25 J 1756 -2251 1. 40 1. 18 (PSR+companion)/2 J 1518+4904 1. 35 J 1811 -1736 1. 30 J 1829+2456 1. 25 (David Nice, talk at Vancouver 2005) (Back) 24
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