Open AccessMultiwaveband studies of the hard ROSAT SMC transient 1WGA J0053.8−7226: a new X‐ray pulsar
Author(s) -
Buckley D. A. H.,
Coe M. J.,
Stevens J. B.,
Van Der Heyden K.,
Angelini L.,
White N.,
Giommi P.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.03982.x
Subject(s) - physics , astrophysics , rosat , pulsar , photometry (optics) , stars , luminosity , astronomy , proportional counter , x ray pulsar , be star , small magellanic cloud , infrared , neutron star , subgiant , flux (metallurgy) , galaxy , optics , globular cluster , detector , materials science , metallurgy
We report on two optical candidates for the counterpart to an X‐ray source in the Small Magellanic Cloud, 1WGA J0053.8−7226, identified as a serendipitous X‐ray source from the ROSAT Position Sensitive Proportional Counter (PSPC) archive, and also observed by the Einstein Imaging Proportional Counter. Its X‐ray properties, namely the hard X‐ray spectrum, flux variability and column density, indicate a hard, transient source, with a luminosity of ∼ XTE and ASCA observations have confirmed the source to be an X‐ray pulsar, with a 46‐s spin period. Our optical observations reveal two possible candidates within the error circle. Both exhibit strong H α and weaker H β emission. The optical colours indicate that both objects are Be‐type stars. The Be nature of the stars implies that the counterpart is most likely a Be/X‐ray binary system. Subsequent infrared (IR) photometry ( JHK ) of one of the objects shows that the source varies by at least 0.5 mag, while the measured nearly simultaneously with the UBVRI and spectroscopic observations indicate an IR excess of ∼0.3 mag.