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
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 508: February 17, 2015
Event: Nova Scorpii 2015 = PNV J17032620-3504140
Discovered by: Tadashi Kojima, Gunma-ken, Japan
Discovery magnitude: unfiltered DSLR magnitude 8.1, using a 150-mm f/2.8 lens and digital
Discovery date: 2015 February 11.837 UT
Spectra: Echelle spectra by Frederick Walter (Stony Brook University) taken on 2015 February
13.40 and reported in Astronomer's Telegram #7060 indicate the presence of strong H-alpha with
FWHM of 2000 km/s, along with several other emission features. See ATel #7060 for details.
Observing recommendations: Observations of all types (visual, CCD, DSLR, spectroscopy) are
strongly encouraged in following the evolution of this nova.
Hills Observatory: 1 January 2013 to 3 November 2019