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Published December 15, 1994 | Published
Journal Article Open

Multiwavelength Observations of the Be star/X-ray Binary EXO2030+375 during Outburst


We present the results from a campaign to monitor the behaviour of the Be star/X-ray binary EXO2030+375 during an X-ray outburst. The BATSE all-sky monitor on board the Compton Gamma-Ray Observatory satellite regularly detects pulsed emission from EXO2030+375 when the neutron star is near periastron. Ground-based optical spectroscopic data plus infrared photometric and polarimetric data were obtained simultaneously with these X-ray data during a typical outburst in 1993 June/July. Despite an increase in the pulsed X-ray flux by an order of magnitude, neither the infrared luminosity nor the equivalent width, strength or profile of the Hoc emission line showed any significant, correlated changes. We conclude that (i) reprocessing of the X-ray flux in the Be star circumstellar envelope, (ii) gravitational disruption of that envelope by the neutron star and (iii) enhanced emission from an Hii region formed around the neutron star are all minimal effects and below our detection threshold. We have also detected significant linear polarization in the infrared flux from EXO2030+375, and we discuss whether or not some fraction of this is intrinsic to the source.

Additional Information

© 1994 Royal Astronomical Society. Provided by the NASA Astrophysics Data System. Accepted 1994 August 17. Received 1994 August 15; in original form 1994 March 2. We thank the PATT for the allocation of observing time on the WHT and UKIRT, and are grateful for the support of service observing programmes on these telescopes and also the JKT. The WHT and JKT are operated by the Royal Greenwich Observatory at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, and the UKIRT is operated by the Royal Observatory Edinburgh. Thanks to Chris Benn, Neil O'Mahoney and Roberto Terlevich at the WHT; Colin Aspin, Joel Aycock, John Davies, Tom Geballe, Dolores Walther and Thor Wold at UKIRT; and Skip Staples and Jean Mueller at Palomar for assistance during the observations and for obtaining service data. We also thank Derek Jones at the RGO for obtaining JKT service data; Marshall Cohen and Angela Putney for helpful information about operating the Palomar spectrograph; and Lars Bildsten for comments on drafts of this paper. CE acknowledges the support of a PPARC studentship. The data reduction was mainly carried out using the Southampton University Starlink node, which is funded by PPARC.

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August 20, 2023
August 20, 2023