Discovery of a transitional Redback millisecond pulsar J1227-4853!
By Jayanta Roy!
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Neutron stars at the crossroads, 25th June 2015 ! European Week of Astronomy and Space Science
JBCA, University of Manchester!
and !!
National Centre for Radio Astrophysics (NCRA-TIFR) !
2
Paul S. Ray (NRL)!
Bhaswati Bhattacharyya (University of Manchester)!
Ben Stappers (University of Manchester)!
Jayaram N. Chengalur (NCRA-TIFR)!
Julia Deneva (NRL)!
Fernando Camilo (Colombia University)!
Tyrel J. Johnson (George Mason University)!
Michael Wolff (NRL)!
Jason W. T. Hessels (ASTRON)!
Cees G. Bassa (ASTRON)!
Evan F. Keane (University of Manchester)!
Elizabeth C. Ferrara (NASA Goddard Space Flight Center)!
Alice K. Harding (NASA Goddard Space Flight Center)!
Kent S. Wood (NRL)!
Collaborators !
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The extremely short spin period of millisecond pulsars are assumed to be ! outcome of accretion of the mass transferred by a low-mass (< Msun) ! companion star through an accretion disk.!ü
A Gyr-long mass accretion during which the system with an accretion disk appears luminous in X-ray; brighter in gamma-ray; radio continuumpowered by outflow.!
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300 known radio MSPs in our Galaxy are believed to be recycled product of accreting neutron stars in low-mass X-ray binaries.!ü
Discovery of millisecond pulsation from accreting neutron stars in LMXB supports how mass accretion is able to effectively spin-up a neutron star.!ü
PSR J1023+0038 (Archibald et al. 2009) and J1824-2452I (Papitto et al.2013) provide most convincing proof of evolutionary link shared by accreting neutron star in low-mass X-ray binary and radio millisecond pulsars. !
LMXB to MSP!
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PSR J1023+0038 with an evidence of accretion disk in 2000-2001; radio pulsar in 2009; reverse transition to LMXB in June 2013 (Stappers et al.2014, Patruno et al. 2014) à decadal time-scale between transitions !
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In last decade (2002-2013) IGR J18245-2452 has shown both rotation!powered and accretion powered activities on a time-scales of few days to ! months. The short timescales observed for transitions between !
accretion-powered and rotation-powered states are comparable with ! those for typical X-ray luminosity variations, caused by swings of the ! mass inflow rate onto the neutron star. !
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It is probable that a rotation-powered pulsar switches on during the ! X-ray quiescent states of other accreting millisecond pulsars!Transitional MSP systems!
LMXB XSS J12270-4859!
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A flat-spectrum radio emission possibility powered by outflow (Hill et al. 2011)!ü
X-ray, UV emissions compatible with accretion powered object !(de Martino D. et al. 2013)!
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Bassa et al. 2014 reported sudden ! decrease in X-ray and optical flux ! around November/December 2012!ü
Previous sign of accretion disk also ! disappeared !!
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XSS J12270-4859 may harbour an ! active rotation-powered MSP!!
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Orbital modulation of X-ray brightness(Bogdanov et al. 2014) ! Courtesy : Bassa et al. 2014
ü The Giant Metre-wave Radio Telescope (GMRT) is a radio interferometer operating at low radio frequencies (150, 244, 322, 607, 1060 to 1450 MHz)!
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Array consisting of 30 antennas of 45 metres diameter, operating at metre wavelengths -- the largest in the world at these frequencies!!ü
Simultaneous dual beam search one with HPBW ~ 40’ (incoherent with 0.4 mJy) other with 1’ (coherent with 0.1 mJy)!ü
2048 X 0.016 MHz spectrum @ 61 μs gives ! dispersion_smear < sample_resolution for ! DM up-to 100 pc cm-3!ü
Synchronous time-domain and imaging ! study!!
The GMRT!
PSR J1227-4853, 1.69ms redback MSP at a DM of 43.5 pc cm-3 discovered at 607 MHz with the GMRT !
(Roy, Bhattacharyya & Ray, Atel #5890, 2014)!
Discovery of PSR J1227-4853!
Timing of PSR J1227-4853!
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500 days of phase coherent ! timing combining !GMRT-607 MHz and ! Parkes-1390 MHz TOAs ! resulting 15 μs residuals!
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Model with four orbital period ! derivatives!ü
Companion mass of < 0.4 M!! sun!ü
Edot/a2 (4 x 1033 erg lt-s-2 s-1): ! an order of magnitude !higher than other MSP binaries!
Timing residuals!
-150 -100 -50 0 50 100 150 200
50 100 150 200 250 300 350 400 450
2014.2 2014.4 2014.6 2014.8 2015 2015.2 2015.4
Post-fit residuals (µs)
MJD - 56700 Year
GMRT 607 MHz TOAs Parkes 1390 MHz TOAs
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Roche lobe radius (0.24 Rsun) smaller than opaque part of companion orbit (4.9 Rsun)!ü
Excess DM of 0.013 seen at eclipse egress à 4 x 1016 cm-2 added electron density!ü
~ 322 TOAs from early 2014 to early June 2015!ü
A redback!CONT: J1227-48 IPOL 607.667 MHZ 22:56-END.ICL001.1 PLot file version 1 created 23-SEP-2014 18:15:16
Cont peak flux = 7.3675E-04 JY/BEAM Levs = 1.000E-05 * (12, 18.78, 29.39, 46.00, 72)
Declination (J2000)
Right ascension (J2000)
12 28 06 04 02 00 27 58 56 54 52
-48 52 30 45 53 00 15 30 45 54 00 15 30 45 55 00 CONT: J1227-48 IPOL 607.667 MHZ 19:37-20:43.ICL001.1 PLot file version 1 created 23-SEP-2014 18:15:21
Cont peak flux = 4.1868E-04 JY/BEAM Levs = 1.000E-05 * (12, 18.78, 29.39, 46.00, 72)
Declination (J2000)
Right ascension (J2000)
12 28 06 04 02 00 27 58 56 54 52
-48 52 30 45 53 00 15 30 45 54 00 15 30 45 55 00
Synchronous radio imaging!
@ eclipsing binary ! phase
@ non-eclipsing binary ! phase
Continuum flux Vs pulsed flux!
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Interstellar effects like scatter broadening or excess dispersion are not the cause of eclipse; probably absorption of radio waves are causing radio eclipse!Pre-discovery radio observations!
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Hill et al. 2009 observations shows radio emissionpowered by outflow!
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Parkes 2012 Marobservations showed marginal detections !
à rotation powered pulsed ! emission active in LMXB- ! state (Takata et al 2014)!!
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Parkes 2013 Nov 12 observations had few intermittent detections !Pulsed gamma-ray emission using Fermi-LAT !
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> 6σ significance detections of gamma-ray ! pulsations using +6months data with same ! model as in Johnson et al 2015!ü
> 0.1 GeV light curve using data over the ! radio timing-span!ü
Gamma-ray peak nearly aligned with main ! peak of 1400 MHz radio profile!ü
Partial co-location of radio-gamma-ray emission region !ü
Considerable spectral evolution of two radio peaks!Courtesy : Johnson et al 2015
Gamma-ray emission!
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Timing model with higher-order orbital period derivatives Vs Proper motion!ü
Photon flux dropped by 3x at ! transition!ü
Flux light curve with 2-day ! bins results the transition day ! as 2012 Nov 30!ü
Gradual decrease in ! gamma-ray flux at ! post-transition!ü
Propeller model to explain the !gamma-ray and X-ray flux increase!
in LMXB-state (Papitto et al. 2014)!
Courtesy to Tyrel Johnson
Summary!
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Discovery of redback PSR J1227-4853 associated with LMXB XSS J12270-4859!ü
Signature of erratic binary orbital behavior!ü
Synchronous radio imaging to revel the eclipse cause!!
