We identify through their X-ray spectra one certain ( W37 ) and two probable ( W17 and X4 ) quiescent low-mass X-ray binaries ( qLMXBs ) containing neutron stars in a long { \it Chandra } X-ray exposure of the globular cluster 47 Tucanae , in addition to the two previously known qLMXBs .
W37 ’ s spectrum is dominated by a blackbody-like component consistent with radiation from the hydrogen atmosphere of a 10 km neutron star .
W37 ’ s lightcurve shows strong X-ray variability which we attribute to variations in its absorbing column depth , and eclipses with a probable 3.087 hour period .
For most of our exposures , W37 ’ s blackbody-like emission ( assumed to be from the neutron star surface ) is almost completely obscured , yet some soft X-rays ( of uncertain origin ) remain .
Two additional candidates , W17 and X4 , present X-ray spectra dominated by a harder component , fit by a power-law of photon index \sim 1.6-3 .
An additional soft component is required for both W17 and X4 , which can be fit with a 10 km hydrogen-atmosphere neutron star model .
X4 shows significant variability , which may arise from either its power-law or hydrogen-atmosphere spectral component .
Both W17 and X4 show rather low X-ray luminosities , L _ { X } ( 0.5-10 keV ) \sim 5 \times 10 ^ { 31 } ergs s ^ { -1 } .
All three candidate qLMXBs would be difficult to identify in other globular clusters , suggesting an additional reservoir of fainter qLMXBs in globular clusters that may be of similar numbers as the group of previously identified objects .
The number of millisecond pulsars inferred to exist in 47 Tuc is less than 10 times larger than the number of qLMXBs in 47 Tuc , indicating that for typical inferred lifetimes of 10 and 1 Gyr respectively , their birthrates are comparable .