Observations of rapid line variations of the Halpha line of SS 433 following a large optical flare

ATel #6355; S. Charbonnel, O. Garde, and J. Edlin (for the ARAS Group)
on 31 Jul 2014; 14:21 UT
Credential Certification: S. N. Shore (shore@df.unipi.it)

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Following the announcement of an extreme outburst of SS 433 (#ATel 6347) we observed the source between 3800 - 7500A at a resolution of ~600. All observations reported here were obtained on consecutive nights, 2014 Jul. 27 - 29UT. Coverage was continuous throughout the night and the observations were reduced independently. The orbital phases covered were calculated using (Goranskii et al. 1998, Astr. Rep. 41, 656; Goranskij 2011, PZ, 31, 5), JD 2450023.62+13.08211E (phase 0.0 is mid-eclipse. The first spectrum (56865.508) was obtained at orbital phase 0.00 and the last (56866.45) at phase 0.08 with a cadence of about 10 minutes and exposure times of 600 sec with a SNR ~ 10 in the continuum (e.g. 4900-5500A). In X-rays (Ginga), first contact is at about phase 0.9 and last contact at 0.1. The stationary Halpha profile displayed three strong peaks and displayed rapid variations of their ratio. Comparison with orbit-resolved observations in the literature (see Gies et al. 2002, ApJ,566,1069; Blundell et al. 2011, MNRAS, 417, 2401) shows that the profiles during these days did not match well the historical triple peaked line at the orbital phases sampled by our spectra. The central peak remained invariant to within the noise but the red peak, at around +1500 km/s, varied by a factor of two (from about 0.5 the intensity of the central peak to equality) between Jul 27.0 and Jul. 27.9. The weak emission peak at approx +3000 km/s varied by a similar fraction (at a level of 0.25 of the central peak at maximum strength). The blue peak remained constant at about 0.5 the intensity of the central peak. The FWZI remained ~8000 km/s throughout the sequence. No significant variations were seen on either the jet lines or He I 6678. The Hbeta line also shows only low amplitude, possibly statistically insignificant, variability. It is not clear whether the line profile variations are due to the outburst, they may be related to the eclipse rather than to the outburst. But if so, they are far faster than most reported in the literature. Monitoring is continuing.