Optical Spectroscopy of EXO 2030+375 during the transition to low X-ray flux

ATel #8927; I. A.Steele (Liverpool JMU)
on 9 Apr 2016; 14:31 UT
Credential Certification: Iain Steele (iainsteele@mac.com)

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ATel#8835 reported the progressive weakening of the regular 46 day X-ray outbursts associated with periastron passage in the High Mass X-ray binary star EXO 2030+375 staring in early 2015.

Here I report the results of occasional optical spectroscopy of the optical Be star counterpart to the source. The spectra were obtained using the dual beam medium resolution FRODOSpec spectrograph of the 2.0 meter Liverpool Telescope, La Palma. The resolution was R=5000 and the spectra cover wavelength ranges 3900-5400 and 5900-8000 Angstroms.

Five spectra have been obtained over the period 2013-07-25 to 2016-03-29, covering the period before and during the current X-ray low state. All of the spectra are very similar, showing emission lines associated with the Hydrogen Balmer series and Fe II. The following table shows the equivalent width and full width half maximum in Angstroms of the H-alpha emission line:

 
DATE       EW     FWHM 
20130725  -33.7     5.78 
20140415  -33.0     5.91 
20140914  -34.5     5.69 
20151126  -34.5     5.63 
20160329  -34.6     5.62 

So far there appears to be no obvious correlation between the low X-ray state of the source and the emission from the Be star disk.

Liverpool Telescope