SIMBAD references

C. B. Markwardt, University of Maryland and Goddard Space Flight Center (GSFC); M. Juda, Harvard-Smithsonian Center for Astrophysics, and J. H. Swank, GSFC, report that the Chandra X-ray Observatory observed XTE J1807-294 on Mar. 10.8 UT, and the best- fit position was determined to be R.A. = 18h06m59s.8, Decl. = -29o24'30" (equinox 2000.0; uncertainty about 1"). On Mar. 13.9, the RXTE PCA measured a 2-10-keV x-ray flux of 20 mCrab. Pulsations are still detected, and an orbital Doppler modulation is clearly evident. The best-fit orbital period is 40.0741 ± 0.0005 min, confirming it as the shortest period of any of the four accreting millisecond pulsars. Optical observations are encouraged.