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					     Ultraluminous X-ray Sources
         Counterparts & Bubbles

              Manfred Pakull, Fabien Grisé
        0bservatoire Astronomique de Strasbourg
coll: C. Motch, R. Soria, I. Smith, A. Kubota, T. Tsuru...

                X-rays from Nearby Galaxies, ESAC Sept 5-7, 2007
ULX Bubbles
LMC X-1 / N159F

           Only bright XRB that
           was known to be
           located in HII region

           Discovery of first
           X-ray ionized nebula
           XIN (HeIII region)
           Pakull&Angebault 1986
         SS433 & Cyg X-1

                      Mechanically inflated
                      bubbles due to
                      XRB jets (or SNR ?)


Gallo et al 2005
                      ! note different scale !
              6 pc
                  ULX IC 342 X-1
                                • "Tooth" nebula situated in
                                  spiral arm has a diameter of
                                  220pc (Pakull & Mirioni
                                  2002; Roberts et al 2003;
                                  Grisé et al 2006
                                • SNR-like spectrum:
                                  [OI]6300/ H=0.4
                                • X-ray or shock ionization ?
                                • Detection of supersonic
                                  expansion (see later)
from Laurent Mirioni’s thesis
ULX in Holmberg IX (M81 X-9)

                 • Discovered by Miller
                   1995: very lum. SNR
                 • But variable compact
                 • diameter = 250 pc, away
                   from young star-burst
                 • Contrary to claim by
                   Miller H/H is normal,
                 • Blue star/group near X-
                   ray position (see later)
        ULX NGC 1313 X-2

                           Previously candidate for
                           galactic neutron star !

                           location far away (9kpc)
                           from nucleus of N1313
                           no nearby starburst

                           diameter 400 pc

Laurent Mirioni’s thesis
     What powers ULX Bubbles ?

1- Photoionized by ULX (or companion star or cluster) ?
   XUV luminosity of the source

2a - SNR (HNR) of star that created ULX ?
2b - inflated by wind/jet from ULX (or superbubble
     inflated by cluster) ?
   age, explosion energy Eo, or wind/jet luminosity
X-ray photoionization
Strömgren spheres around O stars
                   Even hottest massive
                   stars (O2,3 V) do not
                   emit substantial He+
                   Ly cont (hn > 54 eV)

                   i.e., no He++ ions
                    no nebular
                   HeII4686 emission

                   very thin skin of
                   ‘warm’ OI atoms
                   [OI]6300/Ha < 0.03
           X-ray ionized nebula


                         no sharp Stroemgren
                         ‘warm’ He++ zone:
                          HeII4686 emission
                         ‘warm’ neutrals
                          strong [OI] , [SII]
Holmberg II X-1:
    2nd XIN

nebular HeII 4686
emission at the position of
the ULX (Pakull & Mirioni 2002)

‘Heel’ of Foot nebula
Xray ionized nebula in Holmberg II

                             Chandra position coincident with
                                       He III region
                          structure confirmed by Kaaret et al 04

From Laurent Mirioni’s thesis; nebula is density-bound (optically thin)
                            beyond heel
Holmberg II X-1 seen by HST
                 imaging with ACS
                 camera on HST by
                 Kaaret et al 2004:

                 Confirmation of
                 nebular morphology
                 (ionisation structure);

                 Counterpart: V=21.9,
                 Mv ~ -5.6
  HeII 4686 X-ray photon counting
                            X-ray photoionization
                            models (CLOUDY) show
                            good agreement with
                            Zanstra photon counting
                            for 4686 flux; i.e.
                             LHeII4686  LX

                            if the nebula indeed
                            “sees” the total isotropic
                            X-ray luminosity,
                            i.e. LX ~ 1040 erg/s
no, or only little, X-ray
Shock ionization
  A few elements of shock physics
Adiabatic, non-radiative shock ( no B field)
n1 = 4 n0; v1= 3/4 vs ; P1 = 3/4 r0 vs2; T1 ~ 105 K v1002

Isothermal, fully radiative shock (no B field)
n2 = M2 n0; v2 = vs; P2 = r0 vs2 ;    T2=T0


                                                  Dopita &
                                                  Sutherland 95:
                                                  vs = 400 km/s
  A few elements of shock physics
Adiabatic, non-radiative shock ( no B field)
n1 = 4 n0; v1= 3/4 vs ; P1 = 3/4 r0 vs2; T1 ~ 105 K v1002

Isothermal, fully radiative shock (no B field)
n2 = M2 n0; v2 = vs; P2 = r0 vs2 ;    T2=T0


                                                  Dopita &
                           [0I] 6300              Sutherland 95
                                                  vs = 400 km/s
   A few elements of shock physics
 Adiabatic, non-radiative shock ( no B field)
 n1 = 4 n0; v1= 3/4 vs ; P1 = 3/4 r0 vs2; T1 ~ 105 K v1002

 Isothermal, fully radiative shock (no B field)
 n2 = M2 n0; v2 = vs; P2 = r0 vs2 ;    T2=T0

For fully radiative shocks a certain fraction of the
dissipated energy (‘shock luminosity’ [erg/cm2/s])
               L = ½ r vs3
is radiated as H recombination radiation, i.e., L (~0.003 x L)

             L = 7.4x10-6 v22.4 n0 erg/cm2/s
     Shock diagnostics 1


3                      ratio as function
                       of schock vel. vs
1                      (Dopita et al 1984)

     Shock diagnostics 2: uncomplete shocks
    Distance from shock    Distance from shock
                                                  at al. 1988
  OIII5007/ H           1.0
100                                              high
                                     OIII5007   [OIII]5007/ H
                                                 ratios (>6)
10                                                uncomplete
                                                 shocks (not XIN !)

                                         H      high
1          OI6300/H                            [OI]6300/ H
                                                 ratios (>0.1)
                                                  complete
0.1                       0.0                    shocks
     Holmberg IX X-1 Nebula


   Ha [OIII] B
                                      30 "


                                      500 pc


shock ionized nebula;
breakout towards SE with incomplete shocks
                   ULX IC 342 X-1
                                 Subaru observations (Grisé et al)
Roberts et al, MNRAS (2003)

  INTEGRAL field spectrograph:
  Cont5000 H [OIII]-contours

- ‘high-ionization’ cones are not confirmed
- 5007/ H varies as function of vs and of completeness !
- i.e., no indication of non-isotropic X-ray emission
    Kinematics of ULX Nebulae
                Holm IX              NGC1313 X-2


[NII] 6584

               IC 342 X-1                Holm II

              Vexp = 80 – 150 km/s
  Pakull & Mirioni 2002
                                  NGC1313-X2 nebula
                              •   Size ~ 570 x 400 pc
                              •   V ~ 100 km/s
                              •   n ~ 0.2 cm-3
                              •   E ~ 1.0 x 1053 erg


courtesy D. Wang
see Ramsey et al 2006

  Photo- or shock- ionization ?
(with kind regards from the AGN/Liner community)

NGC 6946 X-1/MF16, a compact bubble with
strong HeII 4686 emission that cannot easily
be explained as XIN;
i.e., Lx(observed) appears much too low;
Abolmasov et al. 2006

NGC 1313 X-1: high [OI]6300/Ha ratio in
nebular neighbourhood (Pakull&Mirioni 2002)

NGC 4485/90: new IR spectral diagnostic
proposed by Vazquez et al 2007
Spitzer IR diagnostics for six
    ULXs in NGC 4485/90

                      Vazquez et al 2007
                      IR diagnostic diagram:

                      regions around 5/6
                      ULX appear to have
                      higher ionization than
                      normal HII regions;
                      i.e. AGN-like
   Energetics of ULX Bubbles
Sedov –Taylor (SNR kin Energy E0, adiabatic)
• R ~ 12.8 pc (E51/n )1/5 t42/5
• V ~ 500 km/s (E51/n )1/5 t4-3/5
• t ~ 6 105 yrs R100/V100
• E0 ~ 2 1052 erg R1003 V1002 n

Wind/jet fed bubble (mech. luminosity LW )
• R ~ 26.2 pc (L36/n )1/5 t43/5
• V ~ 15.4 km/s (L36/n )1/5 t4-2/5
• t ~ 4 105 yrs R100/V100
• LW ~ 4 1039 erg/s R1002 V1003 n

  density n from I = 7.4x10-6 v22.4 n erg/s/cm2
    Energetics of ULX Bubbles:
Direct application of previous relations yields:
 t ~ 106 yrs (robust); n ~ 0.3 – 10 cm-3 (from H intensity)
  E0~1053 erg
 ~100 SNRs in 106 yrs (excluded !),
  or hypernova ( that created ULX) ?
Supernovae – Hypernovae

                          et al. 2003
     Energetics of ULX Bubbles
Direct application of previous relations yields:
t ~ 106 yrs (robust);
  E0~1053 erg
 ~100 SNRs in 106 yrs (excluded !), or hypernova (->ULX?)

or wind/jet fed :
 LW ~ few 1039 erg/s; Mdot<10-6Msol /yr;
 vW,j ~few 0.1 c (mildly relativistic jet velocity);
  but unlike SS433, jets are not directly observed !
   Energetics of ULX Bubbles
Direct application of previous relations yields:
t ~ 106 yrs (robust); E0~1053 erg
 ~100 SNRs in 106 yrs (excluded !), hypernova (->ULX?)
 LJ~few 1039 erg/s; Mdot<10-6Msol /yr;
  i.e., we predict vJ ~ few 0.1 c, probably dark jets

• much smaller IS density (n~0.01 like in excavated wind-
  driven superbubbles) would lessen E0. and LJ.
• vs(optical) not necessarily = vexp of blastwave (X-ray);
  remember that IS medium is cloudy, like in real SNR
       ULX Bubbles: possible
     Misconceptions & Promises
•   High [OIII]5007/Hb ratio does not necessarily
       imply (beamed) X-ray ionization

•   filamantary HII regions don’t necessarily imply jets

•   If most ULXs do create (wind/jet driven) bubbles:
    then presently inactive ULX and hypothetical
    beamed ULX pointed away from us should still be
    optically visible by their bubbles ;
•   conversely, lack of many large shocked nebulae
    implies that ULX emission is NOT beamed
          Inactive ULX bubbles ?
If most ULX blow energetic bubbles, than there should
exist bubbles that were created by presently inactive ULX,
or by beamed ULX that do not point towards us.
Search for such objects has revealed only few candidates
 little beaming, certainly W/4p > 1/10 !

          NGC 1313 X-2                NGC 1313 field

 H                              H
ULX Optical Counterparts

  c.f. talk by Fabien Grisé

                              Optical data have
                              suggested O star
                              optical counterparts
                               MXRB;

                              holy grail:
                              observe RV curve
                              to derive masses
                              and decide between
                              stellar BHB vs.
                              IMBHs models
    Holmberg IX X-1 counterpart

                                  HeII 4686

Brightest object in cluster has
stellar HeII 4686 emission
                    NGC 1313 X-2


                                     HeII 4686
Pakull et al. 2005: it is the blue
component C1 of double C
(Zampieri 2004,06 07)
Stellar 4686 emission from ULX
                                Upper: SUBARU spectrum of
                                the 22.8 mag optical counter-
HeII 4686          Hol IX
                                part of Hol IX X-1. The stellar
            nebular             4686 has EW = 9A

                                Lower: ESO-VLT spectrum of
                                23.4 mag NGC 1313 X-2. Stellar
      NGC 1313 X-2              4686 EW = 10 A.
       HeII 4686      nebular   ULX counterparts resemble very
                                luminous (Mv ~ -5) LMXB, i.e. X-ray
                                heated accretion disks
                                (not SS433-like: there EWs several
                                100 A !!)
ULX optical counterparts: LMXB –
       like accretion disks

              ULXs 1313X-2, HoIX
                   Van Paradijs & McClintock 1994:

                   X-ray heated disks:
                   Lv ~ Lx1/2 a
                       ~ Lx1/2 Porb2/3 M1/3
                      ~ S
                   HeII 4686 luminosity ~ LX
                   high intrinsic Lx, no
                  beaming at work here
RV variation in NGC1313 X-2 (?)

                                  dotted line corresponds
                                  to RV of HI gas near XRS

    HeII 4686: RV = 300 km/s in 20 d
    if confirmed  Mx < 50 M (i.e., not IMBH !)
    What have we learnt ? fancies

• ULX are IMBH !        …less and less likely

• ULX are Blazars !     no: largely isotropic emitters

• ULX are thermal-  (short) phases of binary evolution !
                        no: stable nuclear-  transfer

• Counterparts are O stars !
                        no: probably accretion disks
     What have we learnt ? facts
 A significant fraction of ULX have nebulae, but
  there are not many X-ray inactive “ULX bubbles”.

 Some ULX photoionize nebulae allowing (via HeII
  4686 photon counting) to estimate total Lx and
  thus possibly excluding beaming (Hol II, MF16).

 Extent and supersonic expansion velocity of ULX
  bubbles allows to measure energetics (>20 x ESNR)
   clues to their formation or recent (relativistic)
  mass-loss history; lifetime > 1 Myr

 Direct measurements of ULX mass (via RV curve
  of accretion disk HeII 4686 emission) appears
  now feasible (but very hard to realize !)

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