extreme transient phenomena in hmxb: an overview of sfxts

Lara Sidoli (INAF-‐IASF Milano)

1 INTEGRAL Roma, 15-‐18 Oct 2013

INTEGRAL Roma, 15-‐18 Oct 2013 2


AXJ1845.0-‐0433


AXJ1845.0-‐0433

Supergiant HMXBs (PERSISTENT)

Be/X-‐ray Binaries (TRANSIENT) SFXTs

Super Orbital periods in SFXTs

IGR J16418-‐4532 P super orb = 14.73 days

P orb = 3.74 days

IGR J16479-‐4514 P super orb = 11.88 days

P orb = 3.32 days

Discovered in Swi8/BAT data (Corbet & Krimm 2013)

Confirmed by INTEGRAL/IBIS (Drave et al., Atel 5131)


SFXTs properUes: the prototype IGRJ17544-‐2619


Rampy et al. 2009

Suzaku

10 37 erg/s

Blay et al 2008

7 INTEGRAL Roma, 15-‐18 Oct 2013

Major outbursts in XTE J1739-‐302

SFXTs properUes

About 10 members Supergiant companion + Neutron Star (1/2 are X-‐ray pulsars)

X-‐ray flaring acUvity with a large dynamic range &

variability Umescale of hours imply wind accre,on

Much fainter X-‐ray emission between major outbursts (how much fainter?)


Swia/XRT monitoring SFXTs


SFXTs spend most of the Ume in an intermediate luminosity state of 1033-‐10 34 erg/s (quiescence is at 10 32 erg/s) Sidoli et al. 2008

Romano et al. 2012


Adapted from Smith et al. 2012

X-‐ray luminosity distribuUon

SFXTs X-‐ray luminosity distribuUon


SFXTs vs persistent Sg-‐HMXBs


SFXTs: high dynamic range (up to 5 orders of magnitude )

&

low average X-‐ray luminosity between bright outbursts , about 100 Umes lower than persistent HMXBs

INTEGRAL preliminary results to characterize the

hard X-‐ray variability of SFXTs

• All public archival IBIS data (almost 9 yrs)

• Targets: a sample of SFXTs, two persistent HXMBs, Crab

• Offaxis angle < 12 deg; detsig = 5; we tried both IMA (Sw) and LC (bin=100 s)

• For details on data reducUon see Paizis et al., 2013 (arXiv 1302.3456)

• Count rate Luminosity (fiing the average spectra)

• Aim: building an “INTEGRAL” luminosity distribuUon INTEGRAL Roma, 15-‐18 Oct 2013 14

INTEGRAL X-‐ray Luminosity DistribuUon

Paizis & Sidoli in prep


Are clumpy winds and different orbital configuraUons enough?

Supergiant winds are clumpy

Wind accreUon

Blay, Negueruela, Reglero 2012




Wind accreUon

Blay, Negueruela, Reglero 2012 counter-‐example

IGR J16479-‐4514 (Porb = 3.3 days)


Suzaku XIS observaUon

Sidoli et al. 2012

a =

10 34 erg/s


2 orders of magnitude higher than what is observed !

A mechanism reducing the accre,on rate is needed




Wind accreUon

Blay, Negueruela, Reglero 2012

AX J1845.0-‐0433 a 5.72 day Orbital Period in INTEGRAL data


Orbital phases of the known outbursts

Goossens et al. 2013

XTE J1739-‐302 orbital INTEGRAL light curve

INTEGRAL Roma, 15-‐18 Oct 2013 24 Drave et al. 2010 P orb = 51.47 days

XTE J1739-‐302 orbital INTEGRAL light curve

INTEGRAL Roma, 15-‐18 Oct 2013 25 Drave et al. 2010 P orb = 51.47 days

A large scale structure in the SG wind?

Are clumps enough to explain SFXTs? Implied X-‐ray variability in HMXBs by accreUon of clumpy winds

INTEGRAL Roma, 15-‐18 Oct 2013 26 Oskinova et al. 2012

The variability implied by these simulaUons is too much. A mechanism damping the variability is needed:

DestrucUon of clumps near the NS? Are the density and velocity gradients smoothed out in the accreUon wake?

INTEGRAL Roma, 15-‐18 Oct 2013 27 Oskinova et al. 2012

The variability implied by these simulaUons is too much. A mechanism damping the variability is needed:

DestrucUon of clumps near the NS? Are the density and velocity gradients smoothed out in the accreUon wake?

X-‐rays from the companion

Are clumps enough to explain SFXTs? Implied X-‐ray variability in HMXBs by accreUon of clumpy winds

Does the SFXTs flaring behaviour directly probe the density (and velocity) structure of the supergiant wind?


AccreUon in X-‐ray Pulsars

INTEGRAL Roma, 15-‐18 Oct 2013 29 Shakura et al. 2012

Lx > 4 x 10 36 erg/s Lx < 4 x 10 36 erg/s

AccreUon in X-‐ray Pulsars

INTEGRAL Roma, 15-‐18 Oct 2013 30 Shakura et al. 2012

Lx > 4 x 10 36 erg/s Lx < 4 x 10 36 erg/s

The actual accreUon rate can be significantly smaller than the Bondi mass accreUon rate


Shakura et al. 2013

IGR J17544-‐2619

INTEGRAL Roma, 15-‐18 Oct 2013 32 Drave et al. 2013, submiped to MNRAS

IGR J17544-‐2619

INTEGRAL Roma, 15-‐18 Oct 2013 33 Drave et al. 2013, submiped to MNRAS

CONCLUSIONS

Besides the flaring acUvity and the high dynamic range, the low X-‐ray luminosity between bright outbursts is difficult to explain (the accreUon rate is much lower than expected) in SFXTs.

SFXTs flares probably do not directly trace the density and the velocity of the (clumpy) wind.

The NS magnetosphere mediates accreUon (e.g. Shakura et al. 2012 accreUon model).


extreme transient phenomena in hmxb: an overview of sfxts

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