Gamma-Ray Pulsars

One of the outstanding questions in gamma-ray astrophysics pertains to the origin of the pulsed emission in neutron stars. The EGRET instrument aboard the Compton Gamma-Ray Observatory has detected pulsed GeV gamma rays from six young, spin powered neutron stars. Spectral measurements in the 10-300GeV range will provide decisive data to sort out the issue of the seat of the acceleration in these systems. VERITAS, with its good sensitivity above 50GeV, will probe the cutoff region of the gamma-ray pulsars and solve the mystery of the accelerator mechanism. Table 4 below lists the top five targets which VERITAS will initially pursue.

**Table 4:** Five pulsars which will be observed with VERITAS.
PSR	RA	DEC	$\dot{E}$ /D² $^{\dagger}$	Comments
B0531+21	5^h 31 $^{\prime}$ 31 $^{\prime\prime}$ .4	21 $^{\circ}$ 58 $^{\prime}$ 54 $^{\prime\prime}$ .3	112	Crab Pulsar, EGRET pulsed source
B0630+18	6^h 33 $^{\prime}$ 54 $^{\prime\prime}$ .0	17 $^{\circ}$ 46 $^{\prime}$ 11 $^{\prime\prime}$ .5	3.24	GEMINGA, EGRET pulsed source
B1951+32	19^h 52 $^{\prime}$ 58 $^{\prime\prime}$ .3	32 $^{\circ}$ 52 $^{\prime}$ 40 $^{\prime\prime}$ .5	0.59	CTB 80 pulsar
B0656+14	6^h 59 $^{\prime}$ 48 $^{\prime\prime}$ .1	14 $^{\circ}$ 14 $^{\prime}$ 21 $^{\prime\prime}$ .5	0.42	EGRET pulsed source
J0538+2817	5^h 38 $^{\prime}$ 25 $^{\prime\prime}$ .0	28 $^{\circ}$ 17 $^{\prime}$ 11 $^{\prime\prime}$ .0	0.2
$^{\dagger}\dot{E}$ /D² is a measure of gamma-ray visibility where $\dot{E}$ is the spin down power in units of 10³⁶ erg s^-1 and D² is the square of the distance in units of kiloparsecs.