PoS(INTEGRAL 2010)151 10. This ∼ http://pos.sissa.it/ BH / NS F ´ nski 2011) predict that the ratio 50. The ratio is a natural outcome of (1) the − 30 ∼ BH / NS F 2. This is entirely consistent with the observed Galactic sample. Therefore, ∗ − ´ 0 nski ∼ ´ nski & Ziółkowski 2009) predict that the ratio of the binaries with neutron stars to the 6, while none is observed. We believe, that to remove the discrepancy, one has to take into [email protected] [email protected] ∼ value is rather too low, asof it implies the expected numberaccount of a Be+BH different X-ray history of binaries the of starthe the formation Galaxy. order rate New in stellar the population Magellanic synthesis Clouds, calculations with are the currently respect being to carried out. Speaker. there is no problem of the missing Be+BH X-Ray Binaries for theIn Galaxy the Magellanic Clouds there areneutron 95 star. Again, Be none X-ray hosts binaries a known blackout to-date. hole. specifically The Out for stellar the of population Magellanic those, synthesis Clouds 61 calculations (Ziółkowski host carried & a Belczy ones with black holes isstellar rather initial high mass functionenvelope that evolution provides (i.e. a more major neutron mechanism stars involvednaturally in selects than the progenitors formation black of of holes interacting Be andhave binaries) more X-ray that (2) likely binaries survival common probabilities) with against neutron onesenvelope stars with mergers). black (comparable holes mass A (much binaries comparison more likelyX-ray of common binaries this (48) ratio indicates with that the theorder expected number of number of only of Be confirmed – Be black – hole neutron X-ray binaries star is of the of the Be X-ray binaries with neutron stars to the ones with black holes is only In the Galaxy there are 71and Be for X-ray the binaries known reminder to-date.a the Out black nature of hole. of those, 48 a This hostThe companion a disparity neutron is stellar is star, not referred population known. to(Belczy synthesis as None, a calculations so missing far, following Be is – the known black to formation hole host X-ray of binary Be problem. X-ray binaries ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c 8th INTEGRAL Workshop: The Restless Gamma-raySeptember Universe 27-30, - 2010 Integral2010, Dublin Ireland ⃝ Krzysztof Belczy Janusz Ziółkowski Copernicus Astronomical Center, Warsaw, Poland E-mail: Astronomical Obsevatory, Warsaw University, Warsaw, Poland E-mail: On the Apparent Lack of BeBlack X-ray Holes Binaries in with the Galaxy andClouds in the Magellanic PoS(INTEGRAL 2010)151 Janusz Ziółkowski 300 days) and frequently − . Type II bursts may occur at 10 ∼ orb P ∼ ´ nski 2010) aimed at the understanding of the 2 ´ nski & Ziółkowski 2009 and references therein. years), if the other disc is very weak or absent. The X-ray emission ∼ line). They repeat on time scale of the dynamical evolution of the excretion disc α few to few tens of years (dynamical evolution of the disc, formerly known as the “activity ´ nski & Ziółkowski 2009, Ziółkowski & Belczy ∼ The more detailed description of the properties of Be XRBs systems is given,In e.g. further in discussion, Negueru- I will present the recent stellar population synthesis (SPS) calculations Be XRBs systems are known to contain two discs: excretion disc around Be star and accretion The X-ray emission from Be XRBs (with a few exceptions) is of a distinctly transient nature High mass X-ray binaries host a compact object (a neutron star or a black hole) and a massive few to few tens of years). This recurrence time scale is generally much longer than the orbital weeks to months (which is related to the orbital motion on an eccentric orbit and, on some ∼ of Be XRBs binaries isboth controlled by the by periastron the passages centrifugal (Type I gate(both bursts) mechanism, and types by which, of the in bursts). dynamical evolution turn, ofZiółkowski This is the 2002 mechanism excretion operated and disc explains references therein). the transient nature of the X-rayela emission et ( al. see 2001, Ziółkowski 2002, Belczy (Belczy disc around neutron star.scales Both discs are temporary:of a excretion Be disc star” (Negueruela disperses et and∼ al. refills 2001)), while on the time accretion discoccasions, disperses also and to refills the major on instabilities timea of scales the longer other period disc). of The accretion time disc ( might be absent over ( period (Negueruela et al. 2001). with rather short active phasesThere separated are by two much types longer of quiescentpeating) flares, intervals and (a which Type flaring II are behavior). outbursts classifiedal. (larger as 2001). and Type Type irregular; I I Negueruela outbursts burstsperiastron & are (smaller passages observed Okazaki and in of 2001, regularly systems a Negueruela re- with NS. et any highly They orbital eccentric phase. are orbits. repeating They They are at occurobserved correlated intervals close in with to H the disruption of the excretion disc around Be star (as star. The major subclassand of they high are mass referred to X-ray as binariessequence, Be consists X-ray stars binaries of of (Be a spectral XRBs). Be types TheXRBs star Be A0-O8 are stars and found with are with a Balmer massive, rather compact generally emission wide main object lines (orbital (Negueruela periods in 1998). the range The of Be Apparent Lack of Be+BH X-Ray Binaries 1. Introduction eccentric orbits and a compactare object within accretes their from Roche the lobes windGalaxy and for of in a these the Be wide Magellanic star Clouds, orbits).a and (even neutron in massive At star 109 Be present, (NS) of stars by them, 166 thehave the Be information compact presence XRBs object concerning of was the are the confirmed nature X-ray known to ofalso pulsations. in be the indicates the compact In a component the NS. (such remaining Although as one cases,or an cannot whenever X-ray exclude black we that spectrum), holes, a it it few of isknow, these fair at systems contain to present, white state dwarfs 60 that(among black majority them hole of 22 candidate them confirmed systems contain BHHowever, in NSs systems; not as e.g., the a compact Remillard Galaxy single & components. black andThis McClintock hole in disparity, We 2006; 109 binary the Ziółkowski Be containing XRBs Magellanic 2008). a with Clouds NSs Be versus type not component a single has one been with found a BH, so seems far. indeed striking. PoS(INTEGRAL 2010)151 008) . only a 0 = (5) 265 km/s). Z it hosts either donor mass is = σ Janusz Ziółkowski (1) (3) 7 (Kroupa & Weidner . 300 day; and 2 ≤ − stellar population synthesis orb P ≤ StarTrack ´ nski et al. 2008). We adopt a steep initial 3 02) for galactic binaries and low metallicity ( . 0 = 10 Gyr) we perform a time slice and extract Be X-ray binaries Z = orbital period is in the range 10 t (4) donor is a main sequence star (burning H in its core); (2) 3 (e.g., Ziółkowski 2002; McSwain & Gies 2005). /yr and is constant through the last 10 Gyr (e.g. O’Shaughnessy et al. 2008). / ⊙ (O/B star); 25 of the above systems are designated as hosting a Be star and not a regular O/B 0). The results are calibrated in such a way that the Galactic star formation rate is . ⊙ . 5 to 1 0 1 / ´ nski, Kalogera & Bulik 2002 and Belczy = = Be λ F × α We carried out the calculations for three models of SPS. In model A, it was assumed that The last condition is based on the observations indicating thatOur the set fraction of of conditions Be means that stars we among assume that whenever donor is a Be star then the accretion During our SPS calculations, we consider any system a Be X-ray binary if: We evolve a population of massive binaries using higher than 3 M the binary system will survive thecrossing situation the when Hertzsprung the gap. donor With star the will presentrather overflow state lead its of knowledge, Roche to it lobe seems a while doubtful,However, as merger since this of would model both A componentsfor used (Taam this to & be case. Sandquist a 2000,donor More standard Ivanova its realistic in & Roche seem the Taam lobe to past, 2004). binary while be we from crossing models still the the B carried statistics. Hertzsprung and outcompact gap, The C, objects the leads difference receive which calculations to at between assume birth. a the thatbirth merger Model models B and overflowing velocity B assumes by removal distribution and for of a NSs C derived the the concerns by kicks the Hobbs drawn natal from et the kicks al. radio pulsar (2005; a Maxwellian with all B stars is 1 is always efficient, independently ofXRBs). the size of the binary orbit (as is, in2.3 fact, observed SPS Models in Be/NS code (Belczy 2.2 Definition of a Be XRB for the purpose of SPS calculations a NS or a BH accretor; fraction at the level of 3.5 M star. At the present Galactic disk age ( using classification criteria defined in the following section. 2. SPS Calculations 2.1 SPS Code Apparent Lack of Be+BH X-Ray Binaries origins of the apparent disparity ofas the compared number to of no known Be knownClouds. XRBs Be This with XRBs disparity neutron with is stars black referred (NSs) to holes (106) as (BHs) a in missing the Be Galaxy – black and hole in X-ray the binary Magellanic problem. mass function (IMF) for2003). massive stars We adopt with solar a metallicity ( power-law exponent of for Magellanic Clouds binaries.50% Roche mass lobe loss overflow from is a treatedtreated via given in energy binary; balance a with e.g. non-conservative fully efficient way Meurs(e.g. transfer (with of & orbital van energy into den dispersal of Heuvel an 1989) envelope while the CE phase is PoS(INTEGRAL 2010)151 BH (1) / ´ nski NS F common (2) Janusz Ziółkowski 50. A comparison of this ratio with ´ nski & Ziółkowski (2009). 2. This is entirely consistent with the − − 30 0 ∼ ∼ BH / NS 4 F 6, while none is observed. Obviously, in contrast to the ∼ 133 km/s. = σ 7. For, more physically realistic, models B and C, this ratio was found to be, 10 (for model C). This value is rather too low, as it implies the expected number ∼ ∼ BH / NS F (2) other High Mass XRBs: 42 vs 10 (1) Be XRBs: 71 in the Galaxy vs 95 in the Magellanic Clouds In the Magellanic Clouds there are 95 Be X-ray binaries known to-date. Out of those, 61 More detailed description of the resultsNow, is let given me in remind Belczy that in the Galaxy there are 71 Be X-ray binaries known to-date. Out of The expected distributions of orbital periods and eccentricities for Be/NS and Be/BH binaries For model A the expected ratio of Be-X binaries with NSs to the ones with BHs, host a confirmed neutron star.synthesis Again, calculations none carried hosts out a specifically for black the hole. Magellanic The Clouds (Ziółkowski preliminary &Belczy stellar population respectively, 27 and 54. This relatively high ratio (for models B and C) is a natural outcome of 4. Results for the Magellanic Clouds was found to be the stellar initial mass function thatenvelope provides evolution (i.e. more neutron a stars major than mechanismnaturally black involved selects in holes the and progenitors formation of ofhave Be interacting more X-ray binaries) likely that binaries survival probabilities) with againstenvelope neutron ones mergers). with stars black (comparable holes mass (much more binaries likely common those, 48 host a confirmedpopulation neutron synthesis calculations star. presented above None, predict so thatstars the to far, the ratio is ones of known with the black to binaries holes withthe host should neutron number a be of high black confirmed hole. Be –of The Be neutron – stellar star black X-ray hole binaries X-ray (48) binariesobserved indicates is Galactic of that sample. the the order Therefore, expected of number there only for is the no Galaxy. problem of the missing Be+BH X-Ray Binaries 2011) predict that the ratio ofis the only Be X-ray binaries with neutronof stars Be+BH to X-ray the binaries ones of with the black order holes of for model C are shown ingalactic Be/NS Fig. binaries 1. is shown For in comparison, Fig. the 2. observed orbital periods distribution for 27 Galaxy, there is a problem ofbelieve, the that missing to Be+BH remove the X-Ray discrepancy, Binariesformation one for rate has the in to Magellanic the take Clouds. Magellanic intocalculations, We Clouds, account we used a with the different the galactic history scenario respect of forare to the the in the star star many formation Galaxy. ways rate. very During However, different Magellaniccompare our from Clouds the the preliminary numbers Galaxy for when three comparing classes the of population XRBs: of XRBs. Let us 3. Results for the Galaxy Apparent Lack of Be+BH X-Ray Binaries However, there are some indicationsbinaries that as natal compared kicks to neutron single stars starsa receive (e.g. Maxwellian are Podsiadlowski distribution et with smaller al. for 2004). stars Therefore, in model C assumes PoS(INTEGRAL 2010)151 , , , , ApJ 38 , (2003) (2006) 49 (2008) 223 44 598 174 ARA&A , Janusz Ziółkowski ApJ , (2008) 479 ARA&A , The Be/X-ray transient ApJ Suppl 672 , ApJ , (1998) 505 (2001) 117 Constraining Population Synthesis Models 338 369 A statistical study of 233 pulsar proper motions A&A A&A , , 5 On the formation and evolution of black hole binaries (2005) 118 Binary Population Synthesis: Methods, Normalization, and The number of evolved early-type close binaries in the Galaxy 161 X-ray Properties of Black-Hole Binaries On the Apparent Lack of Be X-ray Binaries with Black Holes The Be/X-ray transient 4U 0115+63/V635 Cas: I. A consistent model Common Envelope Evolution of Massive Binary Stars The Evolutionary Status of Be Stars: Results from a Photometric Study ApJ Suppl , Thermal Timescale Mass Transfer and the Evolution of White Dwarf Galactic-Field Initial Mass Functions of Massive Stars (2002) 407 (2004) 1058 572 On the nature of Be/X-ray binaries 601 (2003) 385 (2005) 974 ApJ ´ ´ ´ (1989) 88 (2001) 108 nski, V. Kalogera & T. Bulik, nski, V. Kalogera, F.A. Rasio, R.E. Taam, A. Zezas, T. Bulik, T.J. Maccarone & N.nski Ivanova, & J. Ziółkowski, ApJ , 341 360 , 226 369 (2009) 870 (2000) 113 R.E. Taam & E.L. Sandquist, R.A. Remillard & J.E. McClintock, A&A I. Negueruela & A.T. Okazaki, A&A I. Negueruela, A.T. Okazaki, J. Fabregat,4U M.J. 0115+63/V635 Coe, Cas: U. Munari II. & Outburst mechanisms T. Tomov, R. O’Shaughnessy, C. Kim, V. Kalogera &via K. Empirical Belczynski, Binary Compact Object Merger and Supernova Rates Ph. Podsiadlowski, S. Rappaport & Z.MNRAS Han, I. Negueruela, N. Ivanova & R.E. Taam, P. Kroupa & C. Weidner, M.V. McSwain & D.R. Gies, E.J.A. Meurs & E.P.J. van den Heuvel, G. Hobbs, D.R. Lorimer, A.G. Lyne & M. Kramer, Binaries of Southern Open Clusters K. Belczy K. Belczy Compact Object Modeling with the StarTrack Population Synthesis Code K. Belczy 707 MNRAS 1076 Surprises This work was partially supported by the Polish Ministry of Science and Higher Education (3) Low Mass XRBs: 197 vsIt 2 is obvious that formation of stars in Magellanic Clouds had to proceed in a completely [9] [6] [7] [8] [5] [2] [3] [4] [1] [14] [15] [11] [12] [13] [10] (MSHE) project 362/1/N-INTEGRAL (2009-2012). References different way from that insynthesis calculations the trying Galaxy. to take We into are account this currently fact. carrying out the new stellar population 5. Acknowledgements Apparent Lack of Be+BH X-Ray Binaries PoS(INTEGRAL 2010)151 (2008) 273 Janusz Ziółkowski 8 Suppl. (2002) 1038 73 Chin. J. Astron. Astrophys. , 6 (2011) Mem. Soc. Astron. Ital. , in preparation ´ nski, Be/X-ray Binaries Masses of Black Holes in the Universe J. Ziółkowski, J. Ziółkowski, J. Ziółkowski & K. Belczy [18] Apparent Lack of Be+BH X-Ray Binaries [16] [17]