Motivated by the recent discovery of 30 new millisecond pulsars in Terzan 5 , made using the Green Bank Telescope ’ s S-band receiver and the Pulsar Spigot spectrometer , we have set out to use the same observing system in a systematic search for pulsars in other globular clusters .
Here we report on the discovery of five new pulsars in NGC 6440 and three in NGC 6441 ; each cluster previously had one known pulsar .
Using the most recent distance estimates to these clusters , we conclude that there are as many potentially observable pulsars in NGC 6440 and NGC 6441 as in Terzan 5 .
We present timing solutions for all of the pulsars in these globular clusters .
Four of the new discoveries are in binary systems ; one of them , PSR J1748 - 2021B ( NGC 6440B ) , has a wide ( P _ { b } = 20.5 d ) and eccentric ( e = 0.57 ) orbit .
This allowed a measurement of its rate of advance of periastron , \dot { \omega } = 0.00391 ( 18 ) ^ { \circ } yr ^ { -1 } .
If due to the effects of general relativity , the total mass of this binary system is 2.92 \pm 0.20 M _ { \sun } ( 1 \sigma ) , implying a median pulsar mass of 2.74 \pm 0.21 M _ { \sun } .
There is a 1 % probability that the inclination is low enough that pulsar mass is below 2 M _ { \sun } , and 0.10 % probability that it is between 1.20 and 1.44 M _ { \sun } .
If confirmed , this anomalously large mass would strongly constrain the equation of state for dense matter .
The other highly eccentric binary , PSR J1750 - 37A , has e = 0.71 , and \dot { \omega } = 0.0055 ( 3 ) ^ { \circ } yr ^ { -1 } , implying a total system mass of 1.97 \pm 0.15 M _ { \sun } and , along with the mass function , maximum and median pulsar masses of 1.65 and 1.26 M _ { \sun } respectively .