Unveiling the hard X-ray Galactic sky with IBIS 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

OUTLINE Obscured HMXBs Possible associations with MeV-TeV sources 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 Telescope time = SUM OF ONTIMEs

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 Telescope time = SUM OF ONTIMEs

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

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

Source populations

HMXBs distribution Bodaghee et al. 2007

Be HMXBs About 35% of HMXBs in the IBIS catalog are Be 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

SGXBs before the INTEGRAL era about 65% of HMXBs in the third IBIS cat are SGXBs with massive supergiant early type (OB) companion donor SGXBs before the INTEGRAL era bright and persistent X-ray sources, not strongly absorbed X-ray luminosities in the range 1036-1038 erg s-1 orbital period in the range 1.4-14 days nearly circular orbit 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)

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 their fast 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)

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 )

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

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

TeV HMXBs LS I+61 303 LS 5039 PSR B1259-63 Cygnus X-1 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 4400σ, 20-100 keV 5σ, 30-50 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)

HESS J1841-055 & AX J1841.0-0535 HESS J1841-055 AX J1841.0-0535 (SFXT) 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

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 (7σ detection), 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) AGILE transient (white circle): strongly variable, lasting only 1 day (Chen et al. 2007)

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

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)

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