Deep XMM-Newton Observations of the “Missing Link” Binary

PSR J1023+0038 in an Accreting State

S. Bogdanov1, A. M. Archibald2,C. G. Bassa2,, A. Patruno2,3, J. W. T. Hessels2,4, G. H. Janssen2, V. M. Kaspi5, B. W. Stappers6, S. Tendulkar6 1Columbia University, 2ASTRON, 3Leiden University, 4University of Amsterdam, 5McGill University, 6Jodrell Bank, 7Caltech

References

Archibald et al. 2009, Science, 324, 1411

Archibald et al. 2010, ApJ, 722, 88

Bogdanov et al. 2011, ApJ, 742, 97

Deller et al. 2012, ApJ, 756, L25

Halpern et al. 2013, Astronomer’s Telegram, #5514

Patruno et al. 2014, 781, L3

Stappers et al. 2014, 790, 39

PSR J1023+0038:

• Eclipsing binary radio millisecond pulsar

(Archibald et al. 2009)

• P = 1.69 ms

• Pb = 4.2 h

• Ė 41034 erg s1

• D = 1.368 kpc (Deller et al. 2012)

• At the end of 2013 June, the pulsed radio

emission ceased, accompanied by a

dramatic increase in -ray, X-ray, and

optical luminosity (Patruno et al. 2014;

Halpern et al. 2013; Stappers et al. 2014)

• The accretion disk first seen in 2001 has

reappeared!

• XMM-Newton observed PSR J1023+0038

starting on 2013 November 10 for 134 ks.

Fig. 1 Chandra ACIS-S light curve of PSR J1023+0038 from

2010 March 24 when the binary was in a disk-free, radio-loud

state. The X-ray emission (LX 11032 erg s1) is strongly

modulated at the binary period. This can be explained by a

partial geometric occultation of an intra-binary shock formed

by the interaction of the pulsar wind and the companion

(Archibald et al. 2010; Bogdanov et al. 2011).

The underlying physical mechanism responsible for the X-ray flares and dips

is unknown as there are three plausible explanations: a) the propeller

mechanism; b) intra-binary shock due to an active pulsar wind; c) low-level

accretion. Further multi-wavelength observations are required to resolve

this essential mystery of PSR J1023+0038 and similar systems.

Fig. 2 XMM-Newton EPIC 0.310 keV light curve of PSR J1023+0038 from 2013 November

10. In addition to the more than an order-of-magnitude increase in mean X-ray flux (red

line), the periodic modulations have been replaced by stochastic variability that includes

intense flares and peculiar flux “dips”. The dips are aperiodic and exhibit no energy

dependence. As such, they must be of an entirely different nature than those in the X-ray

dipper variety of low-mass X-ray binaries. The blue triangles show the simultaneous Swift

UVOT UVW1 filter data.

Fig. 3 XMM-Newton OM B filter photometric light curve binned at a 10 s resolution (black)

showing rapid flickering, modulation at the orbital period, and optical flares correlated with

the X-ray ones (red). Gaps in the data are due to interruptions in exposure. The blue triangles

show the simultaneous Swift UVOT UVW1 filter data.

Fig. 4 XMM-Newton MOS1/2 spectra of PSR J1023+0038 in the high, low (“dip”), and flare

states. The 0.3 10 keV luminosities in the three states are 1.01034, 2.91033, and 5.4 1032

erg s1, respectively. In all cases, the spectrum is well characterized by an absorbed power-law

with 1.7