PSR J1618-3921 and other eccentric MSPstauris/NS2015-2/Octau_1618-3919.pdf · PSR J1618-3921 and other eccentric MSPs FranckOctau,IsmaëlCognard,LucasGuillemot LaboratoiredePhysiqueetChimiedel’Environnementetdel’Espace

PSR J1618-3921 and other eccentric MSPs

Franck Octau, Ismaël Cognard, Lucas Guillemot

Laboratoire de Physique et Chimie de l’Environnement et de l’Espace

30th November 2015

8th Bonn Workshop

[email protected] (LPC2E) PSR J1618-3921 and other eccentric MSPs 30th November 2015 1 / 17

Summary

1 PSR J1618-3921: Description & context

2 PSR J1618-3921: Improving the ephemeris using timing analysis

3 Formation processes and other eccentric MSPs.

4 Conclusion

5 Bibliography


PSR J1618-3921: Description & context

Description & context

PSR J1618-3921 :Discovered by [Edwards and Bailes, 2001] in the late 1990s at the Parkes radio telescope during a survey of theintermediate Galactic latitudes

A millisecond pulsar in an eccentric binary system with a low-mass He White Dwarf companionPeriod ≈ 11 ms, Orbital period ≈ 22.8 days and eccentricity ≈ 0.027

In 2010, [Bailes, 2010] qualifies PSR J1618-3921 as "a bizarre object"

Edwards & al, 2010 Curious properties of the recycled pulsars and the potential of high precision timing. New AstronomyReviews, 54:80–86.


PSR J1618-3921: Description & context

Description & context

Several authors cite this pulsar and propose different models in order to explain the formation of such a system.[Tauris et al., 2013], [Freire and Tauris, 2014], [Antoniadis, 2014], [Knispel et al., 2015], [Jiang et al., 2015]

However, PSR J1618-3921 ephemeris was not very well known and full timing analysis had been never published.Improving parameters of the ephemeris may allow us to determine a formation model or exclude some of them !

Ephemeris from the ATNF Pulsar Catalogue of PSR J1618-3921.

Using timing analysis, we improve the ephemeris of PSR J1618-3921 thanks to the Nançay Radio Telescope.


PSR J1618-3921: Improving the ephemeris using timing analysis

Nançay data & Period variation analysis.

Nançay data overview:

Search the best spin period of the pulsar at a given date (PSRCHIVE routine pdmp) and fit of orbital parameters:

Determination of the orbital parameters using closely-spacedNUPPI observations. Two sucessives maximum are separated by

the orbital period PB ≈ 22.8 days. We are sensitive to avariation on the period of the order of magnitude ≈ 10−4.



Residuals of the phase connected solution of PSR J1618-3921.



PSR J1618-3921 ephemeris.

We assert:the composition of the system: He WhiteDwarf - Neutron starthe eccentricity of 0.027

However, the radio emission of PSR J1618-3921 is very

weak. As a consequence:Very difficult to obtain information on theproper motion of the pulsar which is animportant parameter to explain the formationprocess.Assuming we make an observation each monthduring 5 years and obtain Time of Arrivals witha rms ≈ 25µs (the actual rms with the NUPPIdata), we will be able to detect a pulsarvelocity of ≈ 10km.s−1.

Velocity of the pulsar is a key parameter to determine the

formation process of such system !


Formation processes and other eccentric MSPs.

An older triple system like PSR J1903+0327 ( [Champion et al., 2008], [Freire et al., 2011]).

Such configuration may produce eccentric system.However, this process is chaotic. And now, we knowfive such eccentric system ( [Knispel et al., 2015]).

We have to investigate other processes to explain

the formation of eccentric system !



Accretion-induced collapse (AIC) of massive White Dwarfs.

Scenario proposed by [Canal and Schatzman, 1976], [Ergma and Tutukov, 1976] :A White Dwarf accretes matter from a companion.Avoids the thermonuclear explosion and reaches the Chandrasekhar limit at a density that triggers the collapse.Small amount of mass is ejected and the binary survives

How to avoid the explosion ?Cooling the fuel: CO White Dwarf case ( [Canal and Schatzman, 1976])Less flamable fuel: ONeMg White Dwarf case ( [Miyaji et al., 1979])

[Tauris et al., 2013] compute models with different donor stars. They exclude AIC process with CO WhiteDwarf because of the central densities ρc ≈ 2− 5× 109g.cm−3 which may result in a Supernova Iaexplosion. As a consequence, they consider an ONeMg White Dwarf which accretes matter from: MainSequence Star - He WD - Giant star.

AIC with main sequence star donor (different metallicities). [Tauris et al., 2013]



Accretion-induced collapse (AIC) of massive White Dwarfs [Tauris et al., 2013].

AIC with He White Dwarf donor. [Tauris et al., 2013]. The resulting final system is composed by a Neutron Star and a COWhite Dwarf (MWD ≈ 0.6− 0.9M� and PB ≈ 2hr − 2days)

Same calculations were computed with a giant star as donor. It produces eccentric system with PB ≥ 500days.The main problem is this simulation was calculated using a point mass accreting White Dwarf which did noy allow fordetailed spin angular momentum modeling. As a consequence, we can’t calculate the eccentricity

e =

√1 +

2Eorb J2orbµG2M2

NS M22

where Eorb is the orbital energy, Jorb is the orbital angular momentum and µ is the reduced

mass of the binary system.



Rotation-delayed & Accretion-induced collapse (RD-AIC) of massive White Dwarfs [Freire and Tauris, 2014].

Possible scenario for formation of system { He WD - MSP } [Freire and Tauris, 2014].



Rotation-delayed & Accretion-induced collapse (RD-AIC) of massive White Dwarfs [Freire and Tauris, 2014].

Result from the Monte-Carlo simulation[Freire and Tauris, 2014].

Initial parameters for the simulation:

Porb,0 = 24days, He WD of mass

M2 = 0.26M�, a 1.43M� WD (typic mass of

ONeMg WD)the solid black circle: a symetric AIC(no kick, w = 0km.s−1)The V-shaped light-blue distribution:small-kick w = 10km.s−1 in randomdirectionIndigo and yellow = w = 2km.s−1

and w = 5km.s−1

Random selection of pre-AIC systems (assuming

equal probabilities), with 1.37− 1.48M� WDs

and Porb,0 = 15− 30days (corresponding to

M2 = 0.26− 0.28M�)Wide light grey distribution:w = 5km.s1Dark grey distribution: w = 2km.s1

Systems formed via RD-AIC should host low-massNeutron Stars and move with small systemic velocities,as the natal kick from the White Dwarf implosionshould be minimal.



Interaction with a circumbinary disk [Antoniadis, 2014].

Recent observations seem to show eccentric MSPs host Neutron Stars with highly scattered masses and systemicvelocities. Furthermore, [Antoniadis, 2014] proposed a model where the binary system interact with a circumbinary disk.In this model, the assumption the Neutron Star is already an active MSP is made. The magnetic pressure exceed theram pressure of the accreted matter at lagrangian L1 point. Consequently, a large fraction of the companion’s materialcarrying substantial angular momentum may escape the system through L2 and form a circumbinary disk.

3D Magneto-hydrodynamic simulation of a circumbinary accretion disk [Shi et al., 2012].




Change of the orbital elements due to the interactionof a binary with a CB disk [Antoniadis, 2014].

Initial parameters for simulation:

Porb,0 = 27days, e0 = 4× 10−4,

MNS = 1.45M� and MWD = 0.281M�Blue lines : evolution of theeccentricity ; Black lines : evolution ofthe orbital periodSolid lines : Mdisk = 1.5× 10−4M�Dotted lines : Mdisk = 10−5M�Dashed lines : Mdisk = 10−3M�

Only an interaction with a circumbinary disk ofMdisk = 1.5× 10−4M� during ≈ 50 000years issufficient to produce eccentric system witheccentricities ≈ 0.1 !




Eccentricities of Galactic field binary MSPs as a function of their orbital periods. [Antoniadis, 2014].

Initial parameters:

Pulsar mass drawn from a normal distribution with a mean of 1.45M� and σ = 0.2M�Mdisk = 1.5× 10−4M�Orbital period distribution is taken to be flat in log(Porb) between 1 and 50 daysτCB

max,150 = 105yearsInitial binary eccentricity before the CB disk formation is fixed to the Phinney (1992) prediction with a spread

following a Boltzmann distribution with σ(e20 ) =e202

Jump for Porb ≥ 10days; ↑ disk lifetime ↑ eccentricity


Conclusion

PSR J1618-3921:Part of an eccentric binary system with a He White DwarfDM = 117.95, Period ≈ 11.987294 ms, Orbital period ≈ 22.74559 days, eccentricity ≈ 0.0274441

Different models may explain formation of such system:An older triple system ? [Champion et al., 2008], [Freire et al., 2011]Rotation-Delayed Accretion-Induced-collapse [Freire and Tauris, 2014]Interaction with a circumbinary disk [Antoniadis, 2014]

The velocity of PSR J1618-3921 seems to be a key parameter to conclude about the formation process. At the presenttime, data recorded with the Nançay Radio Telescope are not sufficient to fit a proper motion. In the worst case, planan appointement in 5 years for the final conclusion of this work ! If this velocity exceeds 5km.s−1, the model of aninteraction with a circumbinary disk is privileged.

Octau et al, in prep


Bibliography

Bibliography

Antoniadis, J. (2014).On the Formation of Eccentric Millisecond Pulsars with HeliumWhite-dwarf Companions.ApJL, 797:L24.

Bailes, M. (2010).Curious properties of the recycled pulsars and the potential of highprecision timing., 54:80–86.Canal, R. and Schatzman, E. (1976).Non explosive collapse of white dwarfs.A&A, 46:229–235.Champion, D. J., Ransom, S. M., Lazarus, P., Camilo, F., Bassa, C.,Kaspi, V. M., Nice, D. J., Freire, P. C. C., Stairs, I. H., van Leeuwen,J., Stappers, B. W., Cordes, J. M., Hessels, J. W. T., Lorimer, D. R.,Arzoumanian, Z., Backer, D. C., Bhat, N. D. R., Chatterjee, S.,Cognard, I., Deneva, J. S., Faucher-Giguère, C.-A., Gaensler, B. M.,Han, J., Jenet, F. A., Kasian, L., Kondratiev, V. I., Kramer, M., Lazio,J., McLaughlin, M. A., Venkataraman, A., and Vlemmings, W.(2008).An Eccentric Binary Millisecond Pulsar in the Galactic Plane.Science, 320:1309–.Edwards, R. T. and Bailes, M. (2001).Recycled Pulsars Discovered at High Radio Frequency.ApJ, 553:801–808.

Ergma, E. V. and Tutukov, A. V. (1976).Evolution of carbon-oxygen dwarfs in binary systems., 26:69–76.Freire, P. C. C., Bassa, C. G., Wex, N., Stairs, I. H., Champion, D. J.,Ransom, S. M., Lazarus, P., Kaspi, V. M., Hessels, J. W. T., Kramer,M., Cordes, J. M., Verbiest, J. P. W., Podsiadlowski, P., Nice, D. J.,Deneva, J. S., Lorimer, D. R., Stappers, B. W., McLaughlin, M. A.,and Camilo, F. (2011).On the nature and evolution of the unique binary pulsar J1903+0327.MNRAS, 412:2763–2780.Freire, P. C. C. and Tauris, T. M. (2014).Direct formation of millisecond pulsars from rotationally delayedaccretion-induced collapse of massive white dwarfs.MNRAS, 438:L86–L90.Jiang, L., Li, X.-D., Dey, J., and Dey, M. (2015).A Strange Star Scenario for the Formation of Eccentric MillisecondPulsar/Helium White Dwarf Binaries.ArXiv e-prints.

Knispel, B., Lyne, A. G., Stappers, B. W., Freire, P. C. C., Lazarus,P., Allen, B., Aulbert, C., Bock, O., Bogdanov, S., Brazier, A.,Camilo, F., Cardoso, F., Chatterjee, S., Cordes, J. M., Crawford, F.,Deneva, J. S., Eggenstein, H.-B., Fehrmann, H., Ferdman, R., Hessels,J. W. T., Jenet, F. A., Karako-Argaman, C., Kaspi, V. M., vanLeeuwen, J., Lorimer, D. R., Lynch, R., Machenschalk, B., Madsen,E., McLaughlin, M. A., Patel, C., Ransom, S. M., Scholz, P., Siemens,X., Spitler, L. G., Stairs, I. H., Stovall, K., Swiggum, J. K.,Venkataraman, A., Wharton, R. S., and Zhu, W. W. (2015).Einstein@Home Discovery of a PALFA Millisecond Pulsar in anEccentric Binary Orbit.ArXiv e-prints.

Miyaji, S., Nomoto, K., Yokoi, K., and Sugimoto, D. (1979).Supernova Explosion Triggered by Electron Capture and Formation ofa Neutron Star.International Cosmic Ray Conference, 2:13.

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Tauris, T. M., Sanyal, D., Yoon, S.-C., and Langer, N. (2013).Evolution towards and beyond accretion-induced collapse of massivewhite dwarfs and formation of millisecond pulsars.A&A, 558:A39.


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PSR J1618-3921 and other eccentric MSPstauris/NS2015-2/Octau_1618-3919.pdf · PSR J1618-3921 and other eccentric MSPs FranckOctau,IsmaëlCognard,LucasGuillemot LaboratoiredePhysiqueetChimiedel’Environnementetdel’Espace