u Astrophysik Accreting Pulsars with InsightHXMT 安圣杰 IAAT Kepler Center also at IHEP CAS Andrea Santangelo New eyes on X ray astrophysical objects with Japanese and ID: 778619
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Slide1
Institut f. Astronomie u. Astrophysik
Accreting Pulsars with Insight-HXMT
安圣杰*, IAAT Kepler Center*also at IHEP CAS
Andrea Santangelo
„New
eyes
on X-ray astrophysical objects with Japanese and Chinese observatories” Workshop 2018, November 19-21, ISAS/JAXA, Tokio, Japan
Slide2Part I
Accreting
Pulsars
Slide3Most
of them are in
HMXRBs
A
few
in LMXRBs
(Her X-1, 4U1626-67, GX1+4) The distinctive feature: the magnetic field
X-ray Binaries with a NS: Pulsars...
Liu
et al. A&A, 2000, 2005
Courtesy of Scientific American
Slide4Accreting Pulsars in a nut-shell
Doroshenko, 2011
Wind, high luminosity
Disk, high luminosityWind, low luminosity
Disk, low luminosity
Wind and disk accretionThe first region of interest: The magnetosphere
How to probe the physics at the magnetosphere?
Slide5A rich science case
Physics of magnetospheric instabilities, evidence in A0535 +26 (Caballero et al. 2008, Postnov et al. 2008)
“off states”, “flaring states”, in 4U1907+09 and Vela X-1
(Doroshenko
et al., 2012)
Stable accretion from cold disk in highly magnetized stars (Tsygankov et al. 2017)
For recent (and “historical”) theory: Bozzo et al., 2018 and references therein
Slide6The relevance of Monitoring
4U 0115+63
Propeller observations origin of the low luminosity emission? (Tsygankov 2016)
Applying the Ghosh & Lamb model to X
Persei on data of RXTE/ASM and MAXI/GSC (Yatabe et al. 2018, see also
Doroshenko et al., 2014) Propeller: from
young stellar objects, white dwarfs, and neutron stars (Campana et al., 2018) X-Persei V 0332+53
Slide7Power spectra,
aperiodic Variability and break frequency 1A 0535+262
Doroshenko et al. 2014
B field can be predicted
XMM data (contribution from pulsation subtracted)
Slide8Spin frequency
No pulsations
Mukherjee 05assuming Ghosh
& Lamb model and “propeller” when expectedConsistent changes of fbreak and fspin
Disk present even at very low fluxes!
Slide9Accreting Pulsars in a nut-shell (2)
Wind, high luminosity
Disk, high luminosityWind, low luminosity
Disk, low luminosityWind and disk accretion
The second region of interest:
The accretion structure(s)
In the accretion structures most of the energy is released…
Slide10High
accretion rate
: shock is formed
, plasma is decelerated to subsonic speed and heated. The Plasma then sinks to the NS surface. Emitted photons can only escape perpendicularly to the column forming a wide Fan beam. Lower accretion rate
No shock is formed, plasma is decelerated onto the neutron star surface by Coulomb
collisions; photons are generated by Bremsstrahlung and Compton Cooling. They can escape along the accretion column, generating a pencil beamTwo “last mile” accretion modes!
Slide11After
Kuster
, 2003
Solid Column
Hollow Cylinder
Accretion Columns, yes but…
Slide12The Reflection model
In this model: one of the components emerges from the NS surface
Poutanen et al., 2013; Mushtukov et al., 2015.
Illumination of the NS surfaceA more general issue: which is the beam pattern emerging from the Neutron star and seen at infinity?
Slide13Part II
Why
accreting
pulsars studies?
Slide14Science Rationale (1)
Do we have evidences of this transition between the sub-Eddington and Super-
Eddington regime? Do we understand the formation of the spectra and of the beam components from accreting pulsars? How radiation is formed and appears to the distant observer?
Do we know how accretion works in the presence of a rather large magnetospheres… (physics of instabilities)
Astrophysics questions per se: we want to understand these systems…
Slide15Science Rationale (2)
Physics of plasmas in extreme conditions:
This will allow to address fundamental physics issues: QED effects (Santangelo et al., 2018)
NS mass and radius (Mushtukov et al., 2018; Yatabe at al., 2018)
Next challenge: Laboratory for fundamental physics
Can we probe the magnetic field in regions close to the the surface of the neutron star? Or of the neutron star? Do we observe QED effects, e.g. vacuum birefringence?
Slide16Part III
What
should
we expect from Insight-HXMT?
Slide17Cyclotron lines
A long review paper led by Rüdiger Staubert and Joachim
Trümper, (basically) accepted in A&A, 2019
Slide18Cyclotron line vs. luminosity (1)
Cyclotron line centroids vs. luminosity: negative correlation
Negative correlationV0332+53
Mihara, 1995; Tsygankov et al., 2006; Klochkov et al., 2011
Detection of the transition regime: positive correlation
Vybornov et al., 2018Doroshenko et al., 2017
Slide19Cyclotron line vs. luminosity (2)
Cyclotron line centroids vs. luminosity: positive correlation
Positive correlationHer X-1
Staubert et al., 2007Klochkov et al., 2011, 2012Malacaria
et al., 2015….
Two techniques: monitoring of the outburst, pulse amplitude analysis.Seems to be the standard…
Slide20Summary plot!
From Staubert et al., accepted (2019)
Slide21Cyclotron lines, long term behavior
Staubert et al., 2014, 2017
Her X-1
The trend seemed to stop in 2016!Discovery of the long term decay of the CRS line centroid
Slide22A very recent result: three pulsars
Ji et al., MNRAS submitted
Her X-1
Vela X-1
Cen X-3
No sign of long term decay
Slide23Accreting pulsar: cyclotron absorption line
Her X-1
40 keV
Recent cyclotron line energy increase observed with Integral and NuStar confirmed with Insight-HXMT
Staubert eta al., 2017 and references therein
Courtesy of R. Staubert and the HXMT team
Slide24Monitoring Her X-1
Systematics?
Notice systematics at few percent: HXMT team working on that.
Slide25GRO J1008-57: broad band spectrum
χ2
= 4.3（328）
Wabs*cutoffpl
100
50 keV
Depth：1.85+-0.1Ec：82+-1keVWidth：15+-1.5keV+ cyclabsCRSF at ~80 keV
highest
B
directly measured in the universe
~
10
13
tentatively observed at ~ 4σ with NuSTAR & Suzaku
4 HXMT observations ~235 ks, ~ 20σ detectionχ2= 1.4 （325）
Slide26A polished “pulsed” spectrum
LE
HE
MEZhang S.N. et al., in preparation
Slide27Phase Resolved dependence
Caveat: Preliminary results
Slide28GRO J1008-57
Time
（
hr）
Pspin
= 93 s, Porb
about 247.8 dFor details on GRO J1008-57 Kühnel et al., 2013Phase Num4 Obs.
Slide29Swift J0243.6+614
Wilson-Hodge et al., 2018; Tsygankov
et al., 2018; Doroshenko et al., 2018. Eddington limit exceeded
Be/X-ray binaryTalk by Youli Tuo: search for cyclotron line, frequency variation and torque models
Slide30Pulse profiles and correlation matrices
Exploit pulse to pulse variability
… and correlation of variability between phases
Slide31Flux resolved power spectra
Swift J0243.6+614
The break frequency depends on the
flux?
More than 100 power spectra…
Slide32Swift J0243.6+6124: Power spectra
Frequency
Power
Break frequency vs flux in 1A 0535+262
Independent
diagnostic of inner disc radiusWas found to be correlated with fluxIdea is to repeat analysis for the sourceAnalysis ongoing (no correlation so-far due to difficulties in subtraction of the pulsations/power spectra fitting)
Additional noise
low fx
intermediate fx
Peak of the outburst
(
Doroshenko
et al, 2014)
Slide33Swift J0243.6+6124:
Break frequency
Doroshenko et al. (HXMT accreting pulsars team), in prep.
Slide34Thank
you.
Contact:Andrea SantangeloAbteilung Hochenergieastrophysik
Sand 1, 72076 Tübingen · Germany
Phone: +49 7071 29-76128Andrea.Santangelo@uni-tuebingen.de