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Studying pulsar formation and evolution
via the accretion induced collapse of
white dwarfs
Ali Taani
Under supervision
Prof. Y.H. Zhao & Prof. C.M. Zhang
00-00-2012
On the distribution of massive white dwarfs
and it’s implication for accretion induced
collapse
توزيعات الكتل الضخمة لنجوم االقزام البيضاء ودورها في عملية
االنكماش بسبب تراكم المادة
الدكتور علي عبد الكريم الطعاني
جامعة البلقاء التطبيقية
كلية العقبة الجامعية
Overview of talk
1. Introduction: NS, PSR & WD
2. Formation of Millisecond Pulsars
3. AIC scenarios
4. SN Ia scenarios
5. Summary
6. Future work
1. Introduction:
2. Formation of Millisecond Pulsars
3. AIC scenarios
4. SDSS Data
5. References
6. Summary
Overview of talk
Ring Nebulae (M 57)
Young White Dwarf
Stars with < 6-8 M
make 0.5-1.0 M
Carbon/Oxygen white
dwarfs with radius ~
Earth and central
densities >106 gr/cm3
that simply cool with
time.
White dwarf االقزام البيضاء(WD) stars are most common end-point of stellar
evolution.
They are very old objects: the present population of WDs contains valuable
information about evolution of individual stars and history of our Galaxy.
How to Ignite a White Dwarf !!
How to Ignite a White Dwarf
Single stellar evolution does not appear to
cause thermonuclear explosions
We need to provoke a thermonuclear runaway
that proceeds at such a rate that matter
releases an energy/gram in excess of
gravitational binding energy=> Becomes
unbound!
WDs have lots of fuel (He/C/O)&gravitational
binding energies/gram less than that of nuclear
burning
Use accretion in a Binary as the trigger
Piro „05
Accreting WDs in our Galaxy <1% of WDs are in binaries where
accretion occurs, releasing
gravitational energy
Whereas nuclear fusion of HHe or
HeC releases
This contrast is further enhanced when
the WD stores fuel and burns it rapidly,
making these binaries detectable in
distant galaxies during thermonuclear
events.
Donor star
White Dwarf
Pulsars النجوم النوابض
(Pulse+Star)
Rapidly spinning, magnetized NSs.
Lighthouse Model:
- Spinning magnetic field generates a strong
electric field.
1967
“pulse” and “star,”
When pulsars were first discovered, it thought
they might be evidence of other intelligent life
(Aliens) in Galaxy
A. Hewish and J Bell
Pulsars and NSs
الفرق بين النجوم النوابض والنجوم النيترونية • All pulsars are NSs, but all NSs are not pulsars!!
• Light is emitted by charged particles moving close to
speed of light around magnetic fields.
• Whether we see a pulsar depends on the geometry.
– if polar beam sweeps by Earth‟s direction once each
rotation, NS appears to be a pulsar
Pulsars are
lighthouses
of Galaxy!
Pulsar Origins نشأتها
• MSPs are very old (~109 years).
• Mostly binary
• They have been ‘recycled’ by accretion
from an evolving binary companion.
• This accretion spins up the neutron star to
millisecond periods.
• During the accretion phase the system may
be detectable as an X-ray binary system.
•B ~10^(8-9) G
Normal Pulsars:
• Formed in supernova
• Periods between 0.03 and 10 s
• Relatively young (< 107 years)
• Mostly single (non-binary)
•B ~10^(11-13) G
Pulsars are believed (by most people) to be
rotating NSs
Millisecond Pulsars (MSPs):
PSR-B1937+21- 0.001557=642times
B0329+54, P_spin=0.7145=1.4 times
Recycled Processes
Observational Evidences
QPO, Spin 401 Hz (emitted X-rays are pulsed)
and powered X-ray MSPJ1808.4-3658
(Wijnands & Klis 98).
Double pulsars: PSR J0737-3039AB-
(Lyne+04)
Accretion Induced Collapse (AIC)
Idea: Canal & Schatzman 76, & Nomoto 81
WD accretes matter from a companion 1. Avoids thermonuclear explosion and reaches
Chandrasekhar limit at density for collapse.
2. Small amount of mass is ejected & binary survives.
1- H cores always experiment thermonuclear explosion
2- CO cores can explode(SN Ia) or collapse to NS
3- ONeMg cores collapse to a NS 4- Fe cores always collapse to a NS or BH
AIC
Electron-capture collapse of
the degenerate O-Ne-Mg
M~8-12Msun
low-mass~1.25Msun
small kick velocity
Iron-core collapse
M~ >12Msun
More Massive
Received kick velocity
M ~ 1.4 Mo
R ~ 108-109 cm
Eexplosion ~ 1050 erg
MNI < 10-3 Msun
Neutron star
M ~ 1.2 Mo
R ~ 106 cm
Electron degenerate core
AIC Rate (Uncertain)
~10^-6 - 10^-4 yr-1
e−+ p+ n0 +ne. neutronization
Double Degenerate
Merge: C-OWD
56^Ni rich flow
New optical transient surveys [e.g. Palomar Transient Factory ( PTF) and Pan-STARRs, Medium Deep Survey (MDS)] are sensitive to much fainter transients
Large Synoptic SurveyTelescope LSST , which will image entire sky to limiting magnitude∼24.5 every 3-4 nights and should detect AIC events at rate ∼ 800x10^-4 yr^-1
AIC rate of ∼10^-4 yr^-1
SNe Ia i.e, SN 2008ha (Foley+09; 10), 2005E (Perets+10) and 2002bj (Poznanski+10). Low 56^Ni masses inferred from their peak luminosities (10^−3 − 0.1Msun) consistent with quantity predicted from AIC.
Deseert+06 predicted that AIC produces an optical transient with a peak luminosity ∼ 10^41 ergs s^−1
Observation
BUT…..
Optical dim
Short time scale
High Speed of ejecta v ∼ 0.1 c, (hard to detect)
Low energy 10^48-49 ergs
Low ejecta 0.2 comparison with SN Ia>1M_sun
WD must be of the O-Ne-Mg type (or merge CO-CO)
Must have a relatively large mass, 1.0 to 1.2 Msun
This is only very seldom seen in CVs type binaries.
Physics of MSP formation and physical conditions immediately after AIC remain unclear.
Data
WD: Sloan Digital Sky Survey (SDSS) 115 well-measured WDs masses
- www.sdss.org
MSP: ATNF Pulsar Catalogue (http://www.atnf.csiro.au/research/pulsar/psrcat/)
Massive WDs
M̅= 1.18 Msun
WDs
Corbet diagram
Taani et al. 2012
Reasons that make WDs attractive candidates to AIC process
Spin-Up line…
Taani, Al-Wardat & Khasawneh 2013
Pulsar: ~2267 (radio) + ~ 250 (X-ray)
PSR in Binary:~212, NS/WD/Planet
MSP: ~279, P<20ms,75% binary
Magnetic Field: 108 G - 1015 G; ~1012 G
Spin period: 1.4 ms,10s, <P>=0.5s
Bands: Radio, Optical, X-ray
References
1- Taani A., Zhang C.M., Al-Wardat M. et al., 2012a,
AN, 333, 53
2- Taani A., Zhang C.M., Al-Wardat M. et al., 2012b,
Ap&SS, 338, 295
3- Lorimer, D.R.: Living Rev. Relativ. 11, 8 (2008).
arXiv:0811.0762
4- van den Heuvel, E.P.J.: Science 303, 1143 (2004)
5- Metzger B. D., Piro A. & Quataert E. 2009, MNRAS,
396, 304
Summary Interacting binaries are interesting and important to
observe, as they allow to study accretion effect on
their ultimate evolution.
AIC is “Failed” Thermonuclear Explosion (otherwise Type Ia SN)
AIC provides missing links between MSPs and LMXBs
WDs should be significant numbers for progenitor of MSPs.
There is a strong connection between NSs and WDs via AIC.