ISTITUTO NAZIONALE DI ASTROFISICA IASF Roma

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EDGE, Roma 20 December 2006 P. Ubertini Hard
Fast X-Ray Transients

ISTITUTO NAZIONALE DI ASTROFISICA- IASF Roma
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The transient gamma-ray sky
CANDRA and XMM could see them in M31 and M33
L? 5 x 1034erg/s
Sources can appear in 1000s
Or a few days
Rev 169 Rev 171
Sguera et al., 2005 AA
Or a few weeks
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As well as the highly absorbed Supergiant HMXBs
(slow pulsar companion) INTEGRAL is also
discovering members of a new class of SGXBs that
was escaping by previous detections mainly
because of their fast X-ray transient behaviour
Supergiant fast X-ray transients (SFXTs)
(Sguera et al., 2005, Negueruela et al., 2006,
Smith et al., 2006, Sguera et al., 2006)
SFXTs consist (!?)of a wind accreting
compact object and an OB supergiant donor star
spend most of the time in quiscent state with LX
1031 -1033 and showing sporadic and some time
recurrent outburst with LX 1036 -1037
10,000-100,000 increase in luminosity Outbursts
duration range form minutes to hour fast
repointing needed for detailed on-set study Only
one source, IGRJ11215-5952, shows regular
recurrent outburst every 300 d most likely linked
to its orbital period (Sidoli et alk., 2006) in
t Zand (2005) proposed the clumpy wind in
early-type stars could be captured by the
compact object (OBneutron star?) producing the
X-ray flare on the short observed timescale
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From IBIS, 3rd catalogue SFXTs 6 firm
identif. and 5 candidate 1 more
Source R.A. dec F20-40 F40-100 Type (bold
New 3 Cat) flux in mCrab IGR
J08408-4503 130.203 -45.061 HMXB,SFXT IGR J11215-5952 170.450
-59.869 0.50.1 J1619.4-4945 244.895 -49.744 2.00.1
1.20.2 HMXB?,SFXT? IGR J16465-4507
251.696 -45.125 1.80.1 1.10.2 HMXB,SFXT?,XP
IGR J16479-4514 252.015
-45.216 4.50.1 2.40.2 HMXB?,SFXT? XTE
J17391-3021 264.800 -30.349 1.50.1 0.80.1
HMXB,SFXT,Be? IGR J17407-2808
265.173 -28.202 2.20.1 2.60.1 ?,SFXT?
AX J1749.1-2733 267.273 -27.554 1.50.1
1.50.1 HMXB?,SFXT? IGR J17544-2619
268.586 -26.324 1.00.1 0.30.1 HMXB,SFXT
SAX J1818.6-1703 274.657 -17.045 1.60.1
1.30.2 HMXB,SFXT AX J1841.0-0535
280.243 -5.580 1.10.1 0.70.2
HMXB,XP,Be?,SFXT IGR J18450-0435 281.259
-4.567 1.60.1 1.20.2 HMXB,SFXT
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Cat 2 6 months ago
Sguera et al., 2006
Flux from 40 to 500 mCrab, low energy (up to
40-80) BB fit with kt 3-9 keV
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• Recent results
• One more candidate, IGR J18483-031,
• and a firm Recurrent/though sporadic SFXT, IGR
  J08408-4503
• IGR J18483-0311, in the Scutum spiral arm
• A new hard X-ray transient, discovered on April
  2003 in outburst, 5 more outbursts analyzed as
  well as archival SWIFT data (details in a paper
  by Sguera et al., 2006).
• Source outburst characteristics
• Outbursts duration 0.33-1.8 d
• Peak flux (mCrab) 75-125 mCrab (average
  down to a few mCrab)
• L peak (assuming 5.7 kpc) 3.2-7.8 x 10 36
  erg/s
• Spectral parameters for the best covered
  outburst, 3-100 keV, absorbed cut-off pl (?1.4,
• Eco22 keV and NH 9x10 22 cm-2

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Recurrent/though sporadic SFXT, IGR
J08408-4503 The Super Giant FXT IGR
J08408-4503, discovered by INTEGRAL during a
bright flare, shows sporadic recurrent short
and bright flare reaching peak Luminosity of
10 36 erg/s (quiscent L 10 32 erg/s Kennea
Campana 2006) Recently Gotz et al., (astro-ph
0612437) report on 3 flares detected up to now
based on INTEGRAL SWIFT serendipity
data Characteristics broad band (0.1-200 keV)
spectra well described by power law (? 0.1)
with high energy cut-off at 15 keV, NH 10
21 cm-2 typical of a HMXBs hosting a NS The Ob5Ib
supergiant donor star parameters, wind accretion
conditions imply an orbital period period of the
order of 1 year, a spin period of the orders of
hours and a B of the order of 1013 G.
No sign of disk!
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Srong optical id programme
A strong parallel programme to identify the new
misterious sources and optical with NTT
in X-Rays with XMM-Newton, CHANDRA and
SWIFT/XRT ..
Using the optical data from Russian-Turkish 1.5m
telescope and Swift X-ray observations,
Bikmaev et al, 2006 show that IGR J00234 6141 is
most probably an INTERMEDIATE POLAR with periodic
oscillation of optical emissionwith period of
570s
4 sources, 3 in the Norma region and one closer
to the galactic centre. INTEGRAL, CHANDRA,
Optical and IR observations only one has a
column density that could be as high 1023 cm-2,
SED have been produced. 2 are very likely HMXB
(IGR J16167-4957 and IGR J16207-5129) and 2 are
not (low extinction and SED indicate later
spectral types for the putative companions)
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Using spectroscopic optical data based on
observations with Loiano 1.5m telescope and the
2.2 m ESO/MPGin La Silla more than 20 unknown new
IGR sources have been identified Be High mass,
CV and other star burst galaxy, absorbed Seyfert
etc (Masetti et al., AA, 2004-2006 I to IV )
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Super Giant X-Ray Binaries (SGXB) Super Giant
Fast X-Ray Transient (SFXT)different type of
HMXBs

• HMXB are X-Ray sources composed by young massive
  stars accreting on a compact companion BH, NS
  or WD
• A subclass contains an early type supergiant
  accreting via wind (SGXB) they are bright and
  persistent (12 known before Integral).
• Integral detect new SGXBs, but highly absorbed
  and mixture of persistent and variable, with
  slow, weakly magnetised NS as companion
• A new subclass of SGXB is emerging characterised
  by FAST TRANSIENT behaviour, named Supergiant
  Fast X-Ray Transient (SFXT)
• Sharp rise, complex time profile (multi peak)
  with absorbed spectra (lines?) fit compatible
  with pwlcut-off or thermal breemsstrahlung,
  Lx10exp36 at peak.
• What are they? possibly wind clamps on accretion
  disk in a wide orbit NS system to explain low
  emission during quiescence 1032 erg/s

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Conclusions

• The WFM, should be designed on the science
  requirements for
• WHIM
• GRB
• Blazars detection
• Galactic Compact Objects
• In the latter science case
• X-ray burst spectroscopy
• Outburst accretion processes of fast X-ray
  transients (edge detection)
• Spectroscopy and broad band monitoring of BH
  outbursts and state transitions (clue to
  understanding jet production mechanism and
  system-jet interactions)
• The rate of transient events available for study
  on the basis of the current INTEGRAL.SWIFT and
  RXTE coverage could be 50/year including
  superbursts, LMXB outbursts and SG Fast X-ray
  transient sources
• 1-2 event/month (not a real challenge for
  observing program)
• ..Absorption edges from neutral gas up to 1021-22
  cm-2 from Si, S, Oxigen?, Magnesium etc. see
  Jean presentation