Chandra data of the X-ray source [ PMH2004 ] 47 were obtained in the ACIS Survey of ( catalog M~33 ) ( ChASeM33 ) in 2006 .
During one of the observations , the source varied from a high state to a low state and back , in two other observations it varied from a low state to respectively intermediate states .
These transitions are interpreted as eclipse ingress and egresses of a compact object in a high mass X-ray binary system .
The phase of mid eclipse is given by HJD 245 3997.476 \pm 0.006 , the eclipse half angle is 30.6 \arcdeg \pm 1.2 \arcdeg .
Adding XMM-Newton observations of [ PMH2004 ] 47 in 2001 we determine the binary period to be 1.732479 \pm 0.000027 d. This period is also consistent with ROSAT HRI observations of the source in 1994 .
No short term periodicity compatible with a rotation period of the compact object is detected .
There are indications for a long term variability similar to that detected for Her X–1 .
During the high state the spectrum of the source is hard ( power law spectrum with photon index \sim 0.85 ) with an unabsorbed luminosity of 2 \times 10 ^ { 37 } erg s ^ { -1 } ( 0.2–4.5 keV ) .
We identify as an optical counterpart a V \sim 21.0 ~ { } { mag } star with T _ { eff } > 19000 ~ { } { K } , \log ( g ) > 2.5 .
CFHT optical light curves for this star show an ellipsoidal variation with the same period as the X-ray light curve .
The optical light curve together with the X-ray eclipse can be modeled by a compact object with a mass consistent with a neutron star or a black hole in a high mass X-ray binary .
However , the hard power law X-ray spectrum favors a neutron star as the compact object in this second eclipsing X-ray binary in ( catalog M~33 ) .
Assuming a neutron star with a canonical mass of 1.4 \ > M _ { \sun } and the best fit companion temperature of 33000 K , a system inclination i = 72 \arcdeg and a companion mass of 10.9 \ > M _ { \sun } are implied .