TeV Emission from Millisecond Pulsars in Compact Binaries? Mallory Roberts Eureka Scientific/NRL

TeV Emission from Millisecond Pulsars in Compact Binaries? Mallory Roberts Eureka Scientific/NRL

Binary Period in Days Millisecond Pulsars Spun up by a low mass companion such that their spin period P < 5ms with spin-down power and magnetospheric potential similar to young pulsars Usually circular orbits around low mass (< 0.4 solar) white dwarf, with MSP spin-axis and orbital axis aligned Companion Mass (Solar) Very long (billions of years) spindown timescales with mid-latitude distribution Many found in Globular Clusters. GC MSPs difficult to determine intrinsic spin-down due to GC gravitational potential

THE Black Widow PSR B1957+20 1.6 ms pulsar discovered by Fruchter et al. (1988) at Arecibo 9.2 hour orbit around very low mass (~0.02 solar) companion shows regular radio eclipses which is evidence of intrabinary material Fruchter et al. 1990 optical shows large orbital variation with peak magnitude ~20.3 -- evidence of illumination by pulsar (Fruchter et al 1988)

THE Black Widow PSR B1957+20 Hα nebula direct evidence of pulsar wind (Kulkarni et al. 1988) Possible standard TeV PWN? X-rays from point source and nebular tail (Stappers et al. 2003) X-rays of point source show evidence for orbital modulation, power-law spectrum (eg. Huang and Becker 2007) Interpretation is pulsar ablating companion, perhaps eventually completely evaporating it Stappers et al. 2003 Pulsar wind interacts with ablated material causing an intrabinary shock

THE Black Widow PSR B1957+20 Arons and Tavani model developed for Black Widow, adapted for PSR B1259-63. E ~ 1 x 10 35 erg/s Although circular, orbital modulation caused by obscuration by shock, intrinsic emission beaming from magnetic field, and doppler boosting Arons and Tavani 1993 Pulsar magnetic field much weaker and optical emission much fainter, but system much more compact

THE Black Widow PSR B1957+20 Shock distance of a few lt-sec may imply high B, σ at shock Possibility of hidden γ-ray sources (Tavani 1993). Black Widow proposed source of TeV emission in 1995. A&T predicted electrons accelerated to 3 TeV Estimated luminosity depends on distance to shock, fraction of wind involved, magnetic field of pulsar, optical emission from companion, magnetization of wind, ion fraction BUT primarily, still E/d 2 Raubenheimer et al. 1995.

Other Black WIdows? Between 1988 and 2007, only 2 other eclipsing MSPs with very low mass companions were discovered in the Galactic field. Both have lower E than B1957+20. The NE2001(Cordes and Lazio) DM model puts B1957+20 at 2.5 kpc instead of the 1.5kpc inferred from TC93 Can we believe NE2001?

NE2001 Probably Good, Under Certain Conditions Accurate parallax measurements since 2001 show that the estimate of 20% distance errors is generally good. However, the Galactic scale height of gas used in NE2001 seems to be wrong (eg. Gaensler et al. 2008). Chatterjee et al. 2009 Within the patchy local bubble (D<1kpc) where overall DM is low, small, unmodeled variations in density can lead to large errors MSPs tend to mid-latitudes, and we want close ones...

Lots of Distant Globular Cluster BWs Terzan 5 2 BWs + 3ecl 5.5 kpc 47 Tuc 5 BWs + 2ecl 4 kpc HESS < 7 x 10-13 Aharonian et al. 2009 M13 1 BW 7 kpc MAGIC <5x10-12 Anderhub et al. 2009 See Paulo Freire s web page of MSPs in GCs http://www.naic.edu/~pfreire/gcpsr.html

Caught in the Act of Recycling! PSR J1023+0038 1.69 ms pulsar in 4.8hr orbit discovered in GBT 350MHz Drift Scan Survey (Archibald et al. 2009) 0.2 solar mass nondegenerate companion Archibald et al. 2009 Optical observations from 2001 and earlier showed evidence for accretion disk Only 1.3 kpc away!

Surveying With the GBT Many Missed Pulsars Seen in the North! Drift Scan Survey Performed During Track Refurbishment in summer 2007 also discovered PSR J2256-10, a 2.3ms pulsar in 5hr orbit (Stairs et al. in prep) coincident with Fermi source A large 350 MHz of the Northern Sky with GBT is currently underway (PI Ransom) In 2009, survey of Fermi Bright Source List (PI Ransom) started discovered 3 new MSPs, including 1 BW Additional 15 MSPs discovered in Fermi Sources with GBT (PI Roberts), Parkes (PIs Keith, Camilo), Nancay (PI Cognard) including 3BW + 1eclipsing