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3.3 Millisecond pulsars

The population of known millisecond pulsars (MSPs) is one of the fastest growing populations of relativistic binaries in globular clusters. Several ongoing searches are continuing to reveal millisecond pulsars in a number of globular clusters. Previous searches have used deep multifrequency imaging to estimate the population of pulsars in globular clusters [71Jump To The Next Citation Point]. In this approach, the expected number of pulsars beaming toward the earth, Npuls, is determined by the total radio luminosity observed when the radio beam width is comparable in diameter to the core of the cluster. If the minimum pulsar luminosity is Lmin and the total luminosity observed is L tot, then, with simple assumptions on the neutron star luminosity function,
N = -------Ltot-------. (12 ) puls Lminln (Ltot∕Lmin )
In their observations of 7 globular clusters, Fruchter and Goss have recovered previously known pulsars in NGC 6440, NGC 6539, NGC 6624, and 47 Tuc [71Jump To The Next Citation Point]. Their estimates based on Equation (12View Equation) give evidence of a population of between 60 and 200 previously unknown pulsars in Terzan 5, and about 15 each in Liller 1 and NGC 6544 [71].

Current searches include the following: Arecibo, which is searching over 22 globular clusters [104Jump To The Next Citation Point]; Green Bank Telescope (GBT), which is working alone and in conjunction with Arecibo [123104]; the Giant Metrewave Radio Telescope (GMRT), which is searching over about 10 globular clusters [66]; and Parkes, which is searching over 60 globular clusters [40]. Although these searches have been quite successful, they are still subject to certain selection effects such as distance, dispersion measure, and acceleration in compact binaries [28Jump To The Next Citation Point]. For an excellent review of the properties of all pulsars in globular clusters, see the review by Camilo and Rasio [28] and references therein. The properties of known pulsars in binary systems with orbital period less than one day are listed in Table 2, which has been extracted from the online catalog maintained by Freire [64].UpdateJump To The Next Update Information

With the ongoing searches, it can be reasonably expected that the number of millisecond pulsars in binary systems in globular clusters will continue to grow in the coming years.


Table 2: Short orbital period binary millisecond pulsars in globular clusters. Host clusters and orbital properties. See External Linkhttp://www.naic.edu/~pfreire/GCpsr.html for references to each pulsar.UpdateJump To The Next Update Information












Pulsar
Pspin
Cluster
Porb
e
M2
(ms)
(days)
(M ⊙)






J0024–7204I 3.485 47 Tuc 0.229 < 0.0004 0.015
J0023–7203J 2.101 47 Tuc 0.121 < 0.00004 0.024
J0024–7204O 2.643 47 Tuc 0.136 < 0.00016 0.025
J0024–7204P 3.643 47 Tuc 0.147 0.02
J0024–7204R 3.480 47 Tuc 0.066 0.030
J0024–7203U 4.343 47 Tuc 0.429 0.000015 0.14
J0024–7204V 4.810 47 Tuc 0.227 0.34(?)
J0024–7204W 2.352 47 Tuc 0.133 0.14
J0024–7204Y 2.196 47 Tuc 0.522 0.16
J1518+0204C 2.484 M5 0.087 0.038
J1641+3627D 3.118 M13 0.591 0.18
J1641+3627E 2.487 M13 0.118 0.02
J1701–3006B 3.594 M62 0.145 < 0.00007 0.14
J1701–3006C 3.806 M62 0.215 < 0.00006 0.08
J1701–3006E 3.234 M62 0.16 0.035
J1701–3006F 2.295 M62 0.20 0.02
B1718–19 1004.03 NGC 6342 0.258 <  0.005 0.13
J1748–2446A 11.563 Terzan 5 0.076 0.10
J1748–2446M 3.569 Terzan 5 0.443 0.16
J1748–2446N 8.667 Terzan 5 0.386 0.000045 0.56
J1748–2446O 1.677 Terzan 5 0.259 0.04
J1748–2446P 1.729 Terzan 5 0.363 0.44
J1748–2446V 2.073 Terzan 5 0.504 0.14
J1748–2446ae 3.659 Terzan 5 0.171 0.019
J1748–2021D 13.496 NGC6440 0.286 0.14
J1807–2459A 3.059 NGC 6544 0.071 0.010
J1824–2452G 5.909 M28 0.105 0.011
J1824–2452H 4.629 M28 0.435 0.2
J1824–2452J 4.039 M28 0.097 0.015
J1905+0154A 3.193 NGC6749 0.813 0.09
J1911–5958A 3.266 NGC 6752 0.837 < 0.00001 0.22
J1911+0102A 3.619 NGC 6760 0.141 < 0.00013 0.02
J1953+1846A 4.888 M71 0.177 0.032
B2127+11C 30.529 M 15 0.335 0.681 1.13
J2140–2310A 11.019 M30 0.174 < 0.00012 0.11














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