Variable Stars - Nova Oph 2017
Type Novae Click for lightcurve Close binary systems with orbital periods from 0.05 to 230 days. One of the components of these systems is a hot dwarf star that suddenly, during a time interval from one to several dozen or several hundred days, increases its brightness by 7-19 mag. in V, then returns gradually to its former brightness over several months, years, or decades. Small changes at minimum light may be present. Cool components may be giants, subgiants, or dwarfs of K-M type. The spectra of novae near maximum light resemble A-F absorption spectra of luminous stars at first. Then broad emission lines (bands) of hydrogen, helium, and other elements with absorption components indicating the presence of a rapidly expanding envelope appear in the spectrum. As the light decreases, the composite spectrum begins to show forbidden lines characteristic of the spectra of gas nebulae excited by hot stars. At minimum light, the spectra of novae are generally continuous or resemble the spectra of Wolf- Rayet stars. Only spectra of the most massive systems show traces of cool components. Some novae reveal pulsations of hot components with periods of approximately 100 s. and amplitudes of about 0.05 mag. in V after an outburst. Some novae eventually turn out to be eclipsing systems. According to the features of their light variations, novae are subdivided into fast (NA), slow (NB), very slow (NC), and recurrent (NR) categories. AAVSO Alert 582: June 15, 2017 Drs. Frederick Walter (Stony Brook University) and Paul Kuin (University College London) and colleagues have requested AAVSO observers' assistance in obtaining photometry of Nova Oph 2017 (TCP J17394608-2457555) in support of Target-of-Opportunity observations with Swift UVOT that have been triggered and are scheduled for the next ten days (2017 June 16 - 25), and possibly longer. Photometry to date indicates that Nova Oph 2017, currently at magnitude V ~15.6, may very well undergo a major dust event in the coming days, and BVRI photometry is requested. V photometry is given highest priority. Observations are requested once to a few times per night; if/when fast fading is seen, a faster cadence of observations is requested. Please submit observations to the AAVSO International Database using the name Nova Oph 2017. Once a GCVS name is announced in an IAU Circular or CBET, please use that name.
Hills Observatory: 1 January 2013 to 14 August 2018
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