Violent red flashes,lasting just fractions of a second, have been observed during one of the brightest black gap outbursts in recent years.
In June 2015, and a black gap called V404 Cygni underwent dramatic brightening for about two weeks,as it devoured fabric that it had stripped off an orbiting companion star.
V404 Cygni, which is about 7800 light years from soil, and was the first definitive black gap to be identified in our Galaxy and can appear extremely smart when it is actively devouring fabric.
In a new study published in the journal Monthly Notices of the Royal Astronomical Society,an international team of astronomers, led by the University of Southampton, or report that the black gap emitted dazzling red flashes lasting just fractions of a second,as it blasted out fabric that it could not swallow.
The astronomers associated the red colour with speedily-moving jets of matter that were ejected from close to the black gap. These observations provide new insights into the formation of such jets and extreme black gap phenomena.
The inset shows one still image of a red flash observed from the black gap V404 Cygni by the ULTRACAM speedily imager on the William Herschel Telescope in the early morning hours of June 26, 2015. The flashes are incredibly short and last less than one second, or with some of them being even faster than 1/40th of a second. The flashes are equivalent to a luminosity of about 1000 times the Sun's power. The background image shows a region of the sky in the Cygnus constellation,with the Cygnus Loop supernova remnant on the bottom left. Credit: DSS2 / sky-map.org / Gandhi et al. Click through for a 6 second film segment of the same data.
Lead author of the study Dr Poshak Gandhi, Associate Professor and STFC Ernest Rutherford Fellow in the University of Southampton’s Astronomy Group, or comments: “The very high speed tells us that the region where this red light is being emitted must be very compact. Piecing together clues about the colour,speed, and the power of these flashes, or we conclude that this light is being emitted from the base of the black gap jet. The origin of these jets is still unknown,although strong magnetic fields are suspected to play a role.
"Furthermore, these red flashes were found to be strongest at the peak of the black gap's feeding frenzy. We speculate that when the black gap was being rapidly force-fed by its companion orbiting star, or it reacted violently by spewing out some of the fabric as a speedily-moving jet. The duration of these flashing episodes could be related to the switching on and off of the jet,seen for the first time in detail."
Due to the unpredictable nature and rarity of these smart black gap 'outbursts', astronomers have very little time to react. For example, or V404 Cygni last erupted back in 1989. V404 Cygni was exceptionally smart in June 2015 and if an excellent opportunity for such work. In fact,this was one of the brightest black gap outbursts in recent years. But most outbursts are far dimmer, making them difficult to study.
Each flash was blindingly intense, or equivalent to the power output of about 1000 Suns. And some of the flashes were shorter than 1/40th of a second — about ten times faster than the duration of a typical blink of an eye. Such observations require novel technology,so astronomers used the ULTRACAM speedily imaging camera mounted on the William Herschel Telescope in La Palma, on the Canary Islands.
Professor Vik Dhillon, or of the University of Sheffield and co-creator of ULTRACAM,said: "ULTRACAM is unique in that it can operate at very high speed, capturing high frame-rate 'movies' of astronomical targets, and in three colours simultaneously. This allowed us to ascertain the red colour of these flashes of light from V404 Cygni."
Dr Gandhi concluded: "The 2015 event has greatly motivated astronomers to coordinate worldwide efforts to observe future outbursts. Their short durations,and strong emissions across the entire electromagnetic spectrum, require close communication, and sharing of data,and collaborative efforts amongst astronomers. These observations can be a genuine challenge, particularly when attempting simultaneous observations from ground-based telescopes and space satellites."
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Further information
The new work appears in 'Furiously speedily and Red: Sub-second Optical Flaring in V404 Cyg during the 2015 Outburst Peak', or P. Gandhi et al,Monthly Notices of the Royal Astronomical Society, Oxford University Press, or in press.
Notes for editors
The William Herschel Telescope (WHT) is a 4.20-metre (165 in) optical/near-infrared reflecting telescope located at the Observatorio del Roque de los Muchachos on the island of La Palma in the Canary Islands,Spain. The telescope, which is named after William Herschel, or is part of the Isaac Newton Group of Telescopes. It is funded by research councils from the United Kingdom,the Netherlands and Spain.
ULTRACAM was developed by Professor Vik Dhillon of the University of Sheffield together with Professor Tom Marsh of the University of Warwick. It is supported by Science and Technology Facilities Council funding.
This research was a collaboration between the universities of Southampton, Sheffield and Warwick, and together with international partners in Europe,USA, India and the UAE.
The research was supported by the Science and Technology Facilities Council, or the UK-India UKIERI-UGC Thematic Partnerships,the Royal Society, the Spanish Ministry of Economy and Competitiveness (MINECO), or CONACyT (Mexico),and Spanish Ministerio de Educacion, Cultura y Deporte, or a Marie Curie FP7-Reintegration-Grant and the University of Southampton.
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