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We study the spectral and temporal characteristics of the source GS2023$+$338 (V404 Cyg) during the initial phase of its June 2015 outburst, overthe energy range of 0.5 - 150 keV. This is the first detailed study of thecharacteristics of this source based on {\it SWIFT} observations, beingreported. Based on our analysis, we understand that the source existed in thehard, intermediate and soft spectral states. We find that the evolution of thespectral parameters, the hardness intensity diagram and the rms-intensitydiagram are not similar to those observed for most of the outbursting blackhole sources. We also observe presence of weak peaked components in the powerdensity spectra during the intermediate state of the source. Dramatic changesin the spectral and temporal properties are also exhibited before the ejectionof a radio jet suggesting it to be associated with the coronal mass ejection.It seems that may be due to evacuation of the inner part of the Keplerian discfor a short duration, the disc component is not observed after the huge radioflare. The absorption features observed in the low energy spectra suggest thepresence of wind emission and the evolution of the characteristics of thevariable Fe line emission during both hard and intermediate states, indicateits origin to be probably related to the wind/outflow.

SWIFT view of the 2015 outburst of GS 2023+338 (V404 Cyg): complex evolution of spectral and temporal characteristics