X-Ray and Optical Observations of XTE J0052-723 a Transient Be/X-Ray Pulsar in the Small Magellanic Cloud

Abstract

On December 27th 2000 during our regular SMC monitoring program with Rossi X-ray Timing Explorer, strong pulsations were detected with a period of 4.78 seconds. Subsequent slew observations performed on Jan 9th and 13th across the field of view allowed localisation of the pulsar's position to RA: 0 52 17, Dec: 72 19 51 (J2000). The outburst continued until Jan 24th, 7 PCA observations were obtained during this period, yielding a maximum X-ray luminosity ~10^38 ergs/s. Following calculation of the pulsar position, optical observations of the RXTE error box were made on Jan 16th 2001 with the 1m telescope of the South African Astronomical Observatory (SAAO) while the source was still in X-ray outburst. Candidate Be stars identified from their photometric colours were subsequently observed with the SAAO 1.9m on Nov 7th 2001 to obtain spectra. Only one of the photometrically identified stars [MA93]537 showed prominent H$α$ emission, with a double peaked line-profile (EW= -43.3+/-0.7 A, separation velocity= 200+/-15 km/s) confirming the presence of a substantial circumstellar disk.