Brightness new V906 Keel explained the shock origin

A significant part of the luminosity flash new V906 Carinae is the result of shock processes. This is the conclusion reached by the team of astronomers from 17 countries, includingn researchers, on the basis of observations of outbreaks in several ranges. Article published in Nature Astronomy.

Flash classic of new stars occur as a result
a thermonuclear explosion occurring on the surface of a white dwarf, which is included in
the composition of the binary system. For a long time it was believed that the main part of the luminosity of the new classic is due to the continued thermonuclear burning on
the surface of the white dwarf to fall on the substance of the companion. Last
observations of gamma-ray bursts. gigaelectronvolts power classic new V906 of Kiel, located in the direction of the famous Carina Nebula, show that the internal shock phenomena, when a dense mass of a substance collide at high speed, can prevail in the General luminosity
new.

In the case of classic new outer shell is a white dwarf
with a weight of from one thousandth to one ten-millionth the mass of the Sun expands
at a speed of from 500 to 5000 kilometers per second. The result is a short burst, called a transient, and the system increases the brightness in
thousands or millions of times, reaching, in some cases, the limit of visibility
to the naked eye. After the initial phase
ejection of the shell, the residual nuclear reactions are on the surface of the hot
the white dwarf and the star comes to the quasi-stable phase, the Eddington limit luminosity for white
dwarfs.

Curve optical Shine smoothly decreases from a maximum at the
as the photosphere is lowered and the maximum spectral energy is shifted to
the blue area moving from the visible range in the ultraviolet and soft
an x-ray. However, some new stars are chaotic flash
various frequency, duration and amplitude. Such phenomena are not well understood and
can be explained by the instability in the shell or accretion
disk white dwarf, or features of the transmitted portions of the mass of the companion star.

A team of researchers from 17 countries, including from, spent the extra-atmospheric observations simultaneously in optical and gamma-ray bands new stars V906 Keel and analyzed information on several well-correlated between the outbreaks in the observed areas. During such outbursts, the luminosity of the star V906 Keel was doubled — this suggests that the source was the shock wave. The researchers also found associated weak x-ray emission from the deep of the collision, which confirms that the impact energy of a collision, vyrabatyvaet initially in the form of hard x-ray emission and transformation through different mechanisms, highlighted in the range of longer wavelengths. Data obtained from radio to gamma-ray bands provide direct evidence that the shock of events — the main sources of luminosity of the classical new, and other optical transient phenomena (transients).

Optical transient V906 Carinae (ASASSN-18fv) was opened and spectroscopic
way confirmed as classic new review of the All-Sky Automated Survey March 20,
2018. To flash related Gaia was showing at this point of the object magnitude of 20.1, and on March 21 the apparent magnitude V906 Car made up 7.45. By happy coincidence, the object
came in sight of the monitor BRIght Target Explorer (BRITE)system
nanosatellites and showed unprecedented curve
Shine from the beginning of the explosive process is 16 March 2018. High
a curve resolution of the optical system Shine BRITE showed in
for the first month from the beginning of the explosion of a series of eight following
highs outbreaks. Each of the outbreaks lasted from one to three days and
had an amplitude of 0.8 magnitude. As a rule, such observation
ongoing ground-based instruments, did not give such permission and curve
Shine contained significant gaps, and so small intervals
time to recognize it was virtually impossible.

“During the peak of brightness BRITE-Toronto recorded eight short flashes of light, each was almost two times stronger than the previous one. We saw hints of these developments in ground based measurements, but has never seen them so clear. Usually we monitored the stars of this class from the Ground by using a much smaller number of observations, in addition, measurements often have large breaks and are therefore unable to fix some quick changes”, — quotes the employee of the State astronomical Institute named after Sternberg, Moscow state University Kirill Sokolovsky press service of then science Foundation.

Gigaelectronvolts observations in the gamma-range of the object V906 Keel started about 23
day since the outbreak with a telescope Large Area Telescope (LAT),
installed on cosmic gamma-ray Observatory Fermi. Gamma radiation remained
before the 46th day after the explosion. The measured flux from the object allows us to consider V906 Car the most powerful
gamma source of new stars.

Exceptional brightness of this new gamma-ray allowed
to obtain detailed light curve with multiple peaks. Comparing it with the curve
received the tool BRITE, the researchers came
to the conclusion that the peaks of gamma radiation coincide with flares in
the optical range. This correlation indicates that optical and gamma radiation
new generated processes of the same nature. Flash luminosity simultaneously in
both ranges are the result of impact events — what is happening in the case
IIn supernova explosion
type. The typical expansion speed of the shell of a new star 1000 miles
per second and the arrival time of the gamma-peaks (about a week after the outbreak) indicates
what impact the material had a high density of the order of 1010 grams
per cubic centimeter. In the case of such densities, the shock wave moves to
radiation because at speeds of 1,000 kilometers per second the gas is heated
to a temperature of tens of millions of degrees and emits hard x-rays.
Further, because of the high density x-ray radiation is depleted
and becomes more low-energy species: the optical and infrared ranges.

Time structure and luminosity other optical
transients, such as supernovae of type IIn and Ia
(related to interaction with the surrounding interstellar medium) and supernova heavy duty led the authors to the conclusion that such events have impact
nature — thus the main part of the bolometric luminosity of the objects initially
occurs in the form of x-ray radiation from the shock phenomena, which is then absorbed
and re-emitted in the optical range. The same reasoning held to the explanation of the luminosity of red new
stars, stellar mergers, and tidal destruction phenomena. Thus, the shock phenomena can explain the majority of transients — short-term phenomena in the sky are
nature. However, never before have astronomers not seen direct evidence of shock
the origin of the main part of the bolometric luminosity of a new star.

The observations show that a significant part of the luminosity manifested in
the optical range in a great degree absorbed, the energy of the shock
waves of explosive phenomena in the transients. Observations also showed that these same
the shock phenomenon can accelerate charged particles to relativistic speeds. This
by the way, the supernova shock can be a source of cosmic rays. Using
modern surveys, such as ASAS-SN, Zwicky (Zwicky) Transient Facility (ZTF) and the survey of the Observatory of Faith ruby scientists will be able in the near future to open the transients with greater luminosity. New
the stars in our galaxy remain important sites for testing the physical mechanisms
occurrence of exotic events in deep space.

About the observations of new stars in our galaxy, we receive information often enough — so, at the end of April and beginning of may 2018 new star in the constellation of Perseus can be observed with Amateur telescopes. Shock phenomena are explained and the most powerful flare of new starswhen the stellar wind overtakes gas flushed shell of the star.

Eugene Skarednov

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