Unveiling the hard X-ray Galactic sky with IBIS

1. 5th Science AGILE Workshop, ASDC, Frascati,12-13 Jun 2008 Unveiling the hard X-ray Galactic sky with IBIS Vito Sguera INAF/IASF Bologna On behalf of the IBIS Survey Team

2. OUTLINE • General overview of the third IBIS catalog • HMXBs in the INTEGRAL era: Supergiant Fast X-ray Transients (SFXTs) Obscured HMXBs • Possible associations with MeV-TeV sources

3. Input dataset third IBIS catalog • All public and Core Programme data revolutions 12 to 429 • Spans a range from Nov 2002 to May 2006 ~ 3.5 years • 24,075 pointed Science Windows • Total telescope time of ~ 57 Ms

4. Sky coverage All-sky galactic projection - contours at 500ks intervals

5. images light curves spectra The third IBIS catalog lists 421 soft gamma-ray sources

6. Source populations

7. HMXBs distribution Bodaghee et al. 2007

8. Be HMXBs About35% of HMXBs in the IBIS catalog areBe X-ray binaries • neutron star • main sequence Be star • wind accretion from the dense • equatorial disk • long orbital periods (20-300 days) • particularly eccentric orbits • mostly transient systems • several weeks or months

9. about 65% of HMXBs in the third IBIS cat areSGXBswithmassivesupergiant early type (OB) companion donor SGXBs before the INTEGRAL era • bright and persistentX-ray sources, not strongly absorbed • X-ray luminosities in the range1036-1038 erg s-1 • orbital period in the range 1.4-14 days • nearlycircularorbit because of the evolutionary timescale involved, up to recently SGXBs were believed to be very rare objects, a dozen SGXBs have been discovered in our Galaxy in almost 40 years of X-ray astronomy! (Liu et al. 2000)

10. SGXBs in the INTEGRAL era Since its launch in 2002, in just a few years INTEGRAL tripled the population of SGXBs in our Galaxy! The majority of newly discovered SGXBs are persistent hard X-ray sources which escaped previous detections because of their strongly obscured nature, NH ≥ 1023 cm-2 population of persistent strongly absorbed SGXBs (i.e. Walter et al. 2006, Chaty et al. 2006) The remaining are not strongly absorbed. They escaped previous detections because of theirfast X-ray transient nature, a characteristic never seen before from “classical persistent SGXBs” new class: Supergiant Fast X-ray Transients, SFXTs (i.e. Sguera et al. 2005, 2006, 2007, Negueruela et al. 2005,2006)

11. IGR J16318-4848, prototype of highly absorbed and persistent SGXBs Courvoisier et al. 2003, Walter et al. 2003 NH ~ 1024 cm-2 Fe Kα ~6.4 keV, Fe Kβ~7.1 keV Lx ~1036 erg s-1(20-100 keV, 5 kpc )

12. Supergiant Fast X-ray Transients • most of the time in quiescence, • luminosity values or upper limits in the range 1032 – 1033 erg s-1 • fast X-ray flares lasting less than a day, typically few hours • peak luminosity of 1036 – 1037 erg s-1 • dinamical range 103 - 104 • To date, in just a few years 9 SFXTs reported in the literature • 5 SFXTs are newly discovered sources by INTEGRAL • The remaining 4 SFXTs were previously discovered by other X-ray satellites (ASCA, BeppoSAX, RXTE), however INTEGRAL detected several fast hard X-ray outbursts unveiling or strongly confirming their fast X-ray transient nature

13. XTE J1739-302, prototype of SFXTs Sguera et al. 2005 Duration~ 2 hoursOutburstluminosity ~ 2x1036 erg s-1 (20-60 keV) Quiescent luminosity ~ 5x1032 erg s-1

14. TeV HMXBs In the last years, gamma-ray HMXBs became subjects of very major interest in VHE astronomy.To date, 4 HMXBs have been detected at TeV energies Albert et al. (2007,2006), Aharonian et al. (2005a,2005b) LS I+61 303 LS 5039 9.5σ, 20-100 keV 10σ, 20-100 keV PSR B1259-63 Cygnus X-1 5σ, 30-50 keV 4400σ, 20-100 keV • different mechanisms to explain VHE emission from HMXBs: • leptonic and hadronic jet models (Romero et al. 2005, Paredes et al. 2006, Dermer et al. 2006, Bosch-Ramon et al. 2006) • interaction between the relativistic wind of a young NS and the stellar wind (Maraschi et al. 1981, Dubus et al. 2006) • Cheng-Ruderman mechanism in the magnetosphere of an accreting NS (Orellana et al. 2007)

15. HESS J1841-055 & AX J1841.0-0535 • Aharonian et al. (2008) • HESS J1841-055 • extended morphology • (semi-major axis 24 arcminutes) • bipolar morphology with two peaks (possibly three) • HESS J1841-055 could be the blend of more than one source • from catalog research, Aharonian et al. (2008) reported a • positional correlation with: PSR J1841-0524, PSR J1838-0549, • SNR G26.6-0.1, AX J1841.0-0535 (SFXT) • AX J1841.0-0535 (SFXT) • neutron star 4.7 sec • quiescent Lx ~ 2x1034 erg s-1 • peak Lx ~ 5x1036 erg s-1 • point-like nature and transient behaviour of • AX J1841.0-0535 do not agree with the • extended HESS emission • it could eventually be responsible for a • fraction of the entire TeV emission 10σ, 20-100 keV, ~  3 Ms exposure

16. IGR J20188+3647 & AGILE transient in Cygnus Sguera et al. 2007 IBIS significance image (17-30 keV, 2,000 s exposure ) of the transient IGR J20188+3647(7σdetection), 30 minutes activity, flux 33 mCrab, upper limit 1 mcrab (1Ms) • 3EGJ2016+3657 green probability contours (50%, 68%, 95% and 99%) with its associated blazar (cross point) • 3EG J2021+3716 purple probability contours (50%, 68%, 95% and 99%) with its associated pulsar (diamond) • MILAGRO TeV source MGRO J2019+37 (yellow circle) (Abdo et al. 2007) • AGILEtransient (white circle): strongly variable, lasting only 1 day(Chen et al. 2007)

17. HESS J1632-478 & IGR J16320-4751 • HESS J1632-478(Aharonian et al. 2006) • elongated shape (semi-major axis 12 arcmin, semi-minor axis 3 arcmin) • flux above 200 GeV about 12% of the flux from the Crab • from catalog research, positional correlation • with AX J163252-4746 an IGR J16320-4751(Aharonian et al. 2006) • IGR J16230-4751 • persistent SGXB, Lx~ 1036 erg s-1 20-100 keV • highly absorbed, NH~ 1023 cm-2 • NS 1300 s, 9 days • the point like nature of IGR do not agree with the • extended HESS emission • it could eventually be responsible for a • fraction of the entire TeV emission 18σ, 20-100 keV, ~ 3.2 Ms

18. Example of another important and unexpected INTEGRAL discovery Hard X-ray emission from Anomalous X-ray Pulsars • X-ray luminosities 1034 – 1036 , steady source but outbursts also detected (transient AXPs) • spin periods (5-12 seconds) • no rotation powered, no accretion powered (no apparent optical counterpart) • the so called magnetar model (decay of a very strong magnetic field, 1014 - 1015 G) • is able to explain the observed characteristics of AXPs • AXPs were traditionally considered as soft X-ray sources (0.5-10 keV) with thermal • like spectra (kT ~ 0.4- 0.7 keV) plus a steep power law component (Г~ 3- 4) Recently, INTEGRAL discovered hard X-ray tails from AXPs, described by a power law models with Г~1-1.5 and no sign of break up to ~150 keV, but there must be a break somewhere between 150-750 keV. (Kuiper et al. 2004,2006) A new energy window (E>10 keV) has been opened providing an important dagnostic to study magnetars (Kuiper et al. 2006)

19. This is not the end of the story…. fourth IBIS catalog on going Input dataset ~ 40,000 pointed science windows, i.e. twice the previous IBIS cat; the rate of discovery of HMXBs could hugely increase