Nova (star)

Image by Nova Eridani 2009

A nova ( plural novae ) is a burst of brightness in a close binary star system due to an explosive ignition of hydrogen burning on the surface of a white dwarf .

definition

The term nova is derived from the Latin expression "stella nova" (new star ) and goes back to the name, coined by Tycho Brahe , of an observation of a Tychonic star in 1572 . It refers to the sudden appearance of a previously invisible star-like object in the firmament . Up until the mid-20th century, a nova was any type of star's burst of brightness with an increase to its maximum in a period of days to years and a return to rest brightness within weeks to decades. When the astrophysical cause of the eruptions was recognized, the term changed to the current definition:

A nova is the result of a thermonuclear runaway (an explosive ignition of thermonuclear reactions ) on the surface of a white dwarf. The ignited matter comes from a relatively low-mass main sequence star in a binary star system that has crossed its Roche limit or that was transferred to the white dwarf by accretion from the stellar wind. There it forms an accretion disk . A steadily growing, strongly compressed layer is created on the surface, which is heated more and more at the lower limit, until finally the nuclear fusion of the hydrogen begins and ensures a further increase in temperature. When 10 million Kelvin is reached, an explosive expansion sets in, the speed is 100 to 1,000 km per second. The maximum brightness is reached when the gas temperature has dropped to around 7,000 to 10,000 Kelvin. The envelope radius then increased to 1,000 to 10,000 times the radius of the white dwarf (to an absolute brightness between −6 and −8.5 mag). The binary star system remains largely unaffected by the nova outbreak. Again, matter from the other component can flow to the white dwarf. Novas therefore belong to the cataclysmic variables .

No longer counting among the (classic) novas:

Artist's rendering of the scenario

• The supernovae as well as the hypothetical hypernovae , in which a thermonuclear reaction transforms or destroys the exploding star.
• The dwarf novae , in which an accretion disk around a white dwarf lights up at cyclical intervals.
• The eruptions of symbiotic stars and FU Orionis stars , formerly known as extremely slow novae , which are also the result of an accretion disk lighting up.
• The Luminous Red Novae , which are created when two stars merge in a binary system.
• The Luminous Blue Variables , whose variability arises from variable stellar winds and the formation of pseudophotospheres.
• X-ray novae or soft X-ray transits, which, like dwarf novae , show instability in the accretion disk and, due to their compact companion, emit their energy mainly as X-rays .
• The hypothetical quark novae . These detonations result from theoretical models when a neutron star can no longer withstand the pressure caused by gravity and collapses into a hypothetical quark star .
• Mini-supernovae or kilo-novae have a thousand times more luminosity than normal novae and are probably formed when a neutron star merges with a neutron star or a neutron star with a black hole. Their luminosity is the result of the decay of radioactive nuclides , which are synthesized in a shock wave in such a merger.
• A macro nova is the hypothetical result of a merger of two neutron stars , from which a millisecond magnetar emerges. In a Makronova a rapidly rotating massive neutron star should with a strong magnetic field of 10 ¹¹  T formed. An amount of energy of 10 ⁴⁶  J can be extracted from the magnetic field and the torque within 100 to 10,000 seconds, and the macro-novae model is used to describe the afterglow of gamma ray bursts .
• The Un-Novae are failed core collapse supernovae in which the precursor star collapses directly into a black hole and emits little or no electromagnetic radiation.
• A hypothetical merger nova occurs when two neutron stars merge, creating a rapidly rotating and strongly magnetic neutron star with a large mass. The magnetic field of the magnetar interacts with the circumstellar environment and generates a brief burst of electromagnetic radiation, the luminosity of which exceeds that of a supernova.

In contrast, type I X-ray bursts in some X-ray binary stars are equivalent to nova bursts in cataclysmic variables . The compact star that accretes matter from its companion is a neutron star . The hydrogen and / or helium-rich matter accumulates on the surface of the neutron star and a thermonuclear runaway occurs. The radiation escapes almost exclusively as X-rays , since no optically thick stellar wind forms. Due to the higher density and temperature on a neutron star, thermonuclear reactions take place again after months. In contrast, on the surfaces of white dwarfs of cataclysmic variables, it usually takes millennia before sufficient matter is available for a new thermonuclear runaway.

outbreak

With every outbreak of brightness a nova goes through the following phases:

• The initial increase in the Praenova brightness by around 9 mag within a few days 
• A standstill from one to a few days before the actual maximum. In this phase the optical brightness hardly changes. A standstill is not always observed, which can be due to a late discovery of the nova after this section, or the standstill phase does not occur in all novas.
• The final rise to the maximum within days to weeks. The typical amplitude is 2 mag.
• This is followed by the early descent phase. The brightness falls evenly in this section by around 3.5 mag and the speed of the fall is used as a classification feature to distinguish fast from slow novae. However, there is no standard definition of these terms.
• In the transition phase the brightness drops by a further 3 mag. The decrease in brightness can be uniform, with a deep minimum due to dust formation or with quasi-periodic fluctuations in brightness. This phase can last a few weeks or years.
• This is followed by the final decrease in brightness over years or decades.

The development of the optical spectrum is complex and runs parallel to the change in brightness:

• In the premaximum spectrum there are broad absorption lines as in early stars with superimposed P-Cygni profiles . The expansion speed is between −1300 for fast and −100 km / s for slow novae. It is also known as the Fireball spectrum and the medium is heated by the shock wave of the explosion.
• The principal spectrum appears at its maximum with stronger absorption lines shifted further into the blue . The spectrum is reminiscent of an A or F supergiant with enriched lines of carbon , oxygen and nitrogen . The expansion speed is between −1000 and −150 km / s depending on the speed class of the Nova.
• The diffuse extended spectrum is similar to the principal spectrum with broader and more blue-shifted absorption lines and occurs shortly after the point of maximum brightness.
• This is followed by the Orion spectrum after a decrease in brightness of 2  mag . The spectrum is similar to that of bright O or B stars with strong stellar winds. The expansion speed is between −2700 and −1000 km / s depending on the speed class of the Nova. In addition, the first weak signs of forbidden lines appear.
• In the end, the nebulous spectrum becomes visible, which reflects many properties of a planetary nebula . Numerous forbidden lines of oxygen, nitrogen and sometimes neon occur. The excitation temperature is approximately 10 ⁶  Kelvin .

The evolution of the spectrum is interpreted as an expanding cloud of gas whose transparency decreases during the expansion, and thus the photosphere from which the light quanta without re- absorption move to the earth, inside can migrate.

In the infrared , in particular, the formation of dust from the ejected matter can be observed. The rapid growth of carbonaceous dust particles requires that, in addition to the accreted hydrogen-rich matter, part of the outer layers of the white dwarf also be accelerated beyond the escape speed. Hydrocarbons , silicon carbides and amorphous carbides have been detected in the dust . The spectral lines in the ultraviolet initially follow those described above in the optical range. In the phase of stable hydrogen burning on the white dwarf, the ultraviolet radiation increases again, as does the X-rays . Both types of radiation have their origin predominantly in the thermal radiation from the thin atmosphere around the white dwarf. Due to the low- energy X-ray radiation, a nova is one of the super soft X-ray sources at this stage . The end of the eruption is marked by the cessation of hydrogen burning on the surface of the white dwarf. This happens approximately 3 years after the outbreak began, when super-soft X-rays are no longer detectable from the nova.

Thermonuclear runaway

CNO cycle

For the understanding of novae it was essential to observe that the bolometric brightness remains constant over weeks or years and thus the cause responsible for the outbreak of brightness lasts much longer than the short optical maximum of a nova. A thermonuclear runaway provides the energy for the increase in brightness and the expanding envelope of gas.

Before the eruption, hydrogen-rich matter was transferred from the companion to the white dwarf and mixed with the thin atmosphere of the white dwarf by means of convection . The deceleration of matter as soon as it hits the white dwarf releases energy and increases the temperature in the atmosphere. When the temperature reaches a few million Kelvin , explosive hydrogen burning begins according to the Bethe-Weizsäcker cycle . Since the matter is degenerate , the released energy does not lead to an expansion, but only to a further warming of the matter. As a result, the temperature continues to rise to 10 ⁸  K and the thermonuclear runaway spreads over the entire surface of the white dwarf.

In particular, the radiation pressure accelerates the matter and a shell is repelled at the beginning of the nova eruption. Since the ignition of the thermonuclear runaway took place at the lower limit of the atmosphere of the white dwarf, some matter from the CNO crust is also accelerated into space and can be detected during the principal spectrum. If the degeneration has been reversed by further increasing the temperature, a stable hydrogen burning occurs on the white dwarf. Most of the radiation at this point is emitted as ultraviolet radiation or as scattered infrared radiation due to the thin atmosphere . During the entire eruption, the radiation pressure accelerates matter beyond its escape speed , about 10 ⁻⁴ solar masses are ejected into the interstellar medium . The eruption ends when the hydrogen in the white dwarf's atmosphere is depleted.

Numerous observations of brightness increases in the months before the nova eruption can be found in the literature. This is difficult to reconcile with the hypothesis of the thermonuclear runaway on the surface of a white dwarf, since in a calm cataclysmic variable most of the optical radiation comes from the accretion disk and in the case of long-period systems from the companion. A renewed analysis of the historical recordings of the Novae GK Per , CP Lac , LV Vul and BT Mon from the time before the eruption could not detect any increases in brightness. It is probably an overinterpretation of the photographic plates. Only in the case of V533 Her can an increase in brightness of more than 1 magnitude be seen in a period of one and a half years before the outbreak  .

Types of Novae

These are again divided into sub-categories:

• NA: very fast, fast and medium-fast novae have a decrease in brightness of more than three magnitudes within 100 days or less (example: GK Persei ).
• NB: slow novae have a decrease in brightness of three magnitudes within 150 days or more (example: RR Pictoris ).
• NC: very slow novae have a slight increase in brightness, which remains at its maximum for many years (example: RR Telescopii ).
• NR: recurrent or recurring novae that have erupted more than once in the historical period (example: CI Aquilae ).
• NL: novalike variables, objects that resemble novae but have not been adequately investigated due to their changes in brightness or their spectral properties.

Classic Novae

The classical novae occur in cataclysmic binary star systems. Here the white dwarf and his later companion circle around the common focus . The companion has exceeded its Roche limit and therefore matter flows from it to the white dwarf. This can be done via an accretion disk or, if the white dwarf has a strong magnetic field , hit the magnetic poles directly. The latter type of cataclysmic variable are called polar or AM Herculis stars .

Symbiotic Novae

The symbiotic novae , also known as type NC, are thermonuclear novae in symbiotic binary star systems consisting of a white dwarf and a red giant . The masses of white dwarfs in symbiotic novae are either greater than a solar mass and then lead to rapid novae, which belong to the recurrent novae, or the mass is between 0.4 and 0.6 solar masses and leads to very slow novae. Even the rise of a symbiotic nova can take up to two years or more, e.g. For example, AG Peg took 120 years to return to quiet brightness. The mass transfer in symbiotic novas can, in contrast to classical novas, be a result of wind accretion , whereby the white dwarf captures matter from the stellar wind of the red giant that is emitted evenly in all spatial directions. Furthermore, the symbiotic novae with a low-mass white dwarf lack the optically thick wind and only a small mass of around 10 ⁻⁷ solar masses is expelled into interstellar space. The light curve then shows a plateau of maximum light that sometimes lasts for years. During the entire eruption, a stable hydrogen burning takes place on the surface of the white dwarf, since at the beginning of the eruption no stellar wind carried away most of the atmosphere of the white dwarf and thus more hydrogen is available for the thermonuclear reactions.

Recurrent Novae

Recurrent or recurring novae of type NR are novae that have erupted more than once in a historical period. They are sometimes referred to as recurrent novas in popular science literature. The eruption mechanism is the result of a thermonuclear runaway near the surface of the white dwarf as in the classical novae. Recurrent novae are divided into three groups:

• the RS-Oph / T-CrB-RNe,
• the U-Sco-RNe,
• the T-Pyx RNe.

The first two groups are close binary star systems like the classical Novae. However, it is believed that the mass of the white dwarf is close to the Chandrasekhar limit and that there is a high rate of accretion. Because of the inverse relationship between the mass of the white dwarf and its radius, heavy white dwarfs are much more likely to reach densities at which hydrogen burns will ignite . The RS-Oph / T-CrB group of recurrent novas resembles the symbiotic novas, with the companion of the white dwarf being a red giant and the orbital duration being on the order of 100 days. In the U-Sco group, on the other hand, the companion of the white dwarf is a red dwarf star and the orbital period is in the order of a few hours.

The T-Pyx group is a heterogeneous group of novae that probably only show recurrent outbreaks at times. A normal nova outbreak heats the companion star so that it expands and transfers more matter to the white dwarf. This leads to renewed outbreaks until the companion star stops expanding and shrinks back below the Roche limit . The phase of recurrent eruptions ends after a few hundred years.

Recurrent novas are often confused with TOADs. These are dwarf novae that only show super-eruptions, and these eruptions occur at intervals of several years to decades.

Well-known recurrent novas: CI Aql , T CrB , RS Oph , T Pyx , U Sco , V1017 Sgr

Neon nova

An enrichment of the spectrum with ions of medium mass, especially neon , is observed in around 30% of all classical novae . Based on theoretical considerations, this distribution of the elements in the ejected material cannot be the result of a thermonuclear runaway on a white dwarf with a CO crust. Massive white dwarfs, on the other hand, have an enrichment of oxygen , magnesium and neon on their surface . In Neon-Novae, in addition to the Bethe-Weizsäcker cycle described above , the neon-sodium cycle also takes place, which produces unstable elements such as ²⁰ Ne. Some of these unstable elements could be detected on the basis of the characteristic decay lines in the gamma radiation range.

Helium nova

Theoretically, helium novae or helium-nitrogen novae were predicted as early as 1989. With this kind of cataclysmic variable , helium-rich matter is transferred to the white dwarf and this also ignites in the degenerate state to an explosive helium burn . Helium-rich matter is transferred from the secondary star to the white dwarf because its outer, hydrogen-rich atmosphere has already been accreted by the white dwarf , given off by stellar wind or during a common envelope phase . The best candidate for a Helium Nova so far is V445 Pup = Nova 2000 Puppis. Radial velocity measurements in the spectrum show an unusually high velocity of over 6000 km / s for the expanding envelope. Furthermore, an examination of the changes in brightness before the outbreak showed a light curve that belongs more to a merging binary star system than to a cataclysmic variable. This leaves open whether the V445 Pup is a helium nova or an unusual type II supernova .

Gamma-ray nova

Gamma-ray novae are a small group of classical and symbiotic novae , of which gamma radiation could be detected a few weeks after the outbreak . They all show a very soft gamma spectrum with energies up to a few GeV . In the case of the symbiotic Nova V407 Cygni, the high-energy radiation is likely to have originated from an acceleration of particles in the shock wave between the nova ejecta and the wind of the red giant. In contrast, the cause of the gamma radiation in the neon novae Sco 2012 and Mon 2012 is not known.

Gamma radiation should be detectable from all novae, since the thermonuclear runaway produces radioactive elements such as ⁷ Be and ²² Na, which can be identified using specific lines when they decay. These have so far been observed just as little as the 511-keV annihilation line , which is expected when positrons and electrons are annihilated during thermonuclear reactions.

Occurrence in star catalogs

The General Catalog of Variable Stars currently lists around 400 stars (almost 1% of the stars in this catalog), which are divided into a subgroup of Novae. With around 250 stars , the classic NA Novae are the largest group. The other groups in this catalog are NB , NC , NL and NR and the non-specific N .

Discovery and Statistics

In the past few years, an average of around 12 Novae per year have been discovered in the Milky Way . This is only a part of the novae erupting each year in our galaxy due to conjunctions with the sun , interstellar extinction and a lack of observations, especially in the case of fast novas. The expected novae rate for the Milky Way is 30–80 per year, derived from the nova frequency of the Andromeda Galaxy M31 . The search for novae is mainly done by amateur astronomers . In the spiral galaxies of the local group, the novarate related to the luminosity always seems to have a value of around 2 novas per 10 ¹⁰ solar luminosities and year and is independent of the Hubble type . It has been suggested that there are significant differences in the distribution of fast and slow novae for the different Hubble types and that there is a dependence on the mean metallicity of the galaxy.

Novae as a distance indicator

Empirically, a relationship between the speed of light loss and the absolute brightness been found in maximum: . ${\displaystyle M_{V}=2{,}55\cdot \log(t_{2})-11{,}32}$

Here, M _{V is} the absolute visual brightness and t _{2 is} the time in days in which the visual brightness has fallen by two magnitudes from the maximum brightness. The great brightness of novae allows them to be used in extragalactic systems outside the local group . This behavior can be explained if the maximum brightness and the speed only depend on the mass of the white dwarf. With the mass, the pressure in the atmosphere of the white dwarf will also increase and the thermonuclear runaway will be correspondingly stronger . At the same time, the mass of the hydrogen-rich atmosphere, which is required to ignite the hydrogen burn, decreases and the eruption ends more quickly. However, in addition to recurring novae, there also appears to be a subset of novae in extragalactic systems that deviate greatly from the above relationship.

It has also been found that all novas have approximately the same absolute visual brightness of −5.5 mag 15 days after the maximum. Both methods require the precise determination of the point in time of maximum brightness.

Novae as potential precursors of type Ia supernovae

One possible scenario for the development of type Ia supernovae is the gravitational collapse of a white dwarf in a cataclysmic binary star system . When the mass of a white dwarf exceeds the Chandrasekhar limit of around 1.4 solar masses, a detonation occurs in the degenerate carbon core. However, it is not clear whether the mass of the white dwarf increases or decreases during a nova eruption.

During the eruption, part of the white dwarf's atmosphere is accelerated enough to leave the binary star system. This increases the angular momentum and extends the orbital time of a nova after the eruption. This is counteracted by the friction between the ejected matter and the companion star, which is probably also responsible for the bipolar structure of many nova residues. Furthermore, with a strong magnetic field of the white dwarf, the ionized ejected matter follows the magnetic field lines, which also reduces the angular momentum of the binary star system.

Despite these difficulties, it should be possible to measure the change in the angular momentum of the binary star system and thus also the mass of the white dwarf before and after an eruption by means of a cover light change. The two recurring novae CI Aql and U Sco resulted in values ​​for the matter shed during the nova eruption of some 10 ⁻⁶ solar masses. Within the scope of the measurement accuracy, this corresponds exactly to the accreted mass between the outbreaks. With the recurring Nova T Pyx, however, considerably more matter is shed than is accreted by the companion star between the eruptions.

There is indirect evidence that symbiotic novae are the forerunners for a fraction of around 10% of all type Ia supernovae. During the expansion of the supernova's ejected envelope, this material collides with slower moving gas and dust envelopes. These collisions could z. B. the Supernova PTF 11kx can be detected. The expansion speed of the old gas and dust envelopes is too slow to be caused by the supernova itself and far too fast to be caused by a stellar wind. In addition, there appears to be a continuous, low-density component in the circumstellar environment of the supernovae, with the density and expansion speed of this envelope showing typical values ​​for the stellar wind of a red giant. The multiple penetration of the supernova shock front through the old envelopes speaks for a cyclical ejection of the gas and dust envelopes with a distance of several decades. These properties match the well-known properties of symbiotic novae.

Nova remnant

Nova Cygni 1992 with Nova remnant a few years after the eruption

As with supernovae , an emission nebula can be detected a few years to decades after a nova outbreak . From the radial velocity during the eruption and from the observed angle of the nova remnant, it is possible to calculate the distance independently . The shape of the nebulae is often elliptical , with the proportion of elliptical or sometimes bipolar nebulae increasing with the decrease in the velocity of novas. The flattened axis lies in the orbit plane of the double star system . Therefore, the deviation from the circular shape is a result of the interaction of the ejected matter with the accretion disk and the companion in the course of the expansion. The optically thick wind from which the nova remnant is formed can be detected in the radio area as bremsstrahlung a few weeks after the eruption. The mass of the ejected matter during a nova eruption is 10 ⁻⁵ to 10 ⁻⁴ solar masses. This value is an order of magnitude higher than would be expected from theoretical models. However, this deviation could be caused by a lumpy structure of the ejecta, whereby the part of the ejected matter with the greatest density determines the radiolight curve through an interaction with the surrounding circumstellar matter and simulates a larger mass.

The hibernation scenario

After hibernation scenario ( English hibernation model ) developed a cataclysmic variables for a Nova outbreak back into a separate binary system . Due to the loss of mass during the breakout, the distance between the components increases. The heated white dwarf also increases the temperature of its companion star, which due to the bound rotation always faces it the same side and drives it out of thermal equilibrium . This leads to a temporarily increased mass flow to the white dwarf. After the end of the nova eruption, both stars cool down and the mass flow comes to a standstill. The scenario is supported by an observed decrease in brightness of old novae of 0.0015 magnitudes per year and by some cases such as GK Persei or RR Pictoris , which show dwarf nova outbreaks decades after their nova outbreaks .

This development scenario is also supported by the discovery of an old, extensive Nova shell around the Zwergnova Z Cam. From the undetectable expansion rate, an upper limit of 1300 years could be calculated since the nova envelope has interacted with interstellar matter . The type of dwarf nova of type Z Cam, a subgroup of the dwarf nova with high mass transfer rates, also corresponds to theoretical expectations. Z Cam should therefore have presented itself as a nova-like binary star system immediately after the eruption. The next development step is a dwarf nova of the type Z Cam and in a few centuries a normal dwarf nova of the U Gem type. After this, the mass transfer should come to a standstill for a period of 1,000 to 100,000 years, until the development in reverse order leads to a new nova outbreak.

Special forms

Novae are a burst of brightness as a result of the ignition of a hydrogen flame on the surface of a white dwarf. In normal novae, the hydrogen-rich gas is accreted by a companion. In the literature, however, scenarios are also discussed where the hydrogen comes from other sources:

• Close binary star system consisting of two white dwarfs lose torque due to the radiation of gravitational waves. If one of the white dwarfs has a carbon / oxygen core and a hydrogen-rich shell, sufficient heat is deposited on the white dwarf due to tidal forces in an orbital period of less than 20 minutes to reach the ignition temperature for hydrogen burning. This would be a nova explosion 10,000 to 100,000 years before the binary star system merged.
• Observations over the past decades have shown that the stars in globular clusters only have a uniform chemical composition as a first approximation. One outstanding problem is the variation in the abundance of helium within star clusters. In addition to an enrichment of matter for a second generation of stars by the stellar wind from rapidly rotating massive stars and the stellar winds from AGB stars , the hypothesis is also being discussed that individual massive white dwarfs accreted the remaining gas a few hundred million years after the formation of a globular cluster could. During the nova explosion, the chemically enriched gas was returned to the interstellar medium and a new phase of star formation was triggered by the shock wave .
• When a white dwarf forms a close binary star system with a Be star , it can accrete hydrogen as in cataclysmic systems. A Be star is a very fast spinning early star that occasionally forms a decretion disk . The white dwarf passes through the circumstellar disk and collects fresh hydrogen, which ignites like a nova on the surface of the white dwarf. Since the early star is more luminous than the nova, no optical outburst is registered, but a temporary soft X-ray source as in the super- soft X- ray sources .

List of galactic novas

The following table shows some novae that have been discovered within our own galaxy , the Milky Way , and that (under good conditions) have been visible to the naked eye. The letters and number abbreviations in front of the names indicate, according to the conventions for naming variable stars , how many variable stars within a constellation the respective nova was discovered. The second part of the name denotes the constellation. See also the stars in the category: Nova

year	nova	Maximum brightness
1891	T Aurigae	3.8 likes
1898	V1059 Sagittarii	4.5 mag
1899	V606 Aquilae	5.5 mag
1901	GK Persei	0.2 mag
1903	Nova Geminorum 1903	6 likes
1910	Nova Lacertae 1910	4.6 likes
1912	Nova Geminorum 1912	3.5 likes
1918	Nova Aquilae 1918	−1.4 mag
1920	Nova Cygni 1920	2.0 mag
1925	RR Pictoris	1.2 mag
1934	DQ Herculis	1.5 mag
1936	CP Lacertae	2.1 mag
1939	BT monocerotis	4.5 mag
1942	CP Puppis	0.4 mag
1950	DK Lacertae	5.0 likes
1960	V446 Herculis	2.8 mag
1963	V533 Herculis	3 likes
1967	HR Del	3.5 likes
1970	FH Serpentis	4.4 likes
1975	V1500 Cygni	2.0 mag
1975	V373 Scuti	6 likes
1976	NQ Vulpeculae	6 likes
1978	V1668 Cygni	6 likes
1984	QU Vulpeculae	5.2 likes
1986	V842 Centauri	4.6 likes
1991	V838 Herculis	5.0 likes
1992	V1974 Cygni	4.2 likes
1999	V1494 Aquilae	5.03 mag
1999	V382 Velorum	2.6 likes
2013	Nova Delphini 2013	4.3 likes
2013	Nova Centauri 2013	5.5 mag

See also

• Eruptive variable star
• Diffusion-induced nova

Web links

Wiktionary: Nova  - explanations of meanings, word origins, synonyms, translations

Commons : Nova  - collection of images, videos and audio files

• Central Bureau for Astronomical Telegrams: CBAT List of Novae in the Milky Way.
• Stellar time bomb discovered. Astronomers find candidates for Type Ia supernovae. With photos and animations. At: ESO.org. November 17, 2009. Retrieved April 25, 2018.

Individual evidence

1. ↑ Tycho Brahe. In: The Brockhaus Astronomy. Mannheim 2006, p. 63.
2. ↑ SN Shore, M. Livio, EPJ van den Heuvel: Interacting Binaries. Springer, Berlin 1994, ISBN 3-540-57014-4 .
3. ↑ Nova. In: Astro-Lexicon N2 in Spektrum.de. 2007, accessed March 17, 2019 . 
4. ^ Walter Lewin, Michael van der Klies: Compact Stellar X-ray Sources (Cambridge Astrophysics) . Cambridge University Press, Cambridge 2010, ISBN 978-0-521-15806-0 .
5. ↑ R. Ouyed, M. Kostka, N. Koning, DA Leahy, W. Steffen: quark nova imprint in the extreme supernova explosion SN 2006gy . In: Astrophysics. Solar and Stellar Astrophysics . 2010, arxiv : 1010.5530v1 .
6. ↑ Jens Hjorth, Joshua S. Bloom: The GRB-Supernova Connection . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1104.2274 .
7. ↑ He Gao, Xuan Ding, Xue-Feng Wu, Bing Zhang, Zi-Gao Dai: Bright broad-band afterglows of gravitational wave bursts from binary neutron star mergers as a probe of millisecond magnetars . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1301.0439 .
8. ↑ CS Kochanek et al. a .: A Survey About Nothing: Monitoring a Million Supergiants for Failed Supernovae . In: Astrophysics. Solar and Stellar Astrophysics . 2008, arxiv : 0802.0456v1 .
9. ↑ Yun-Wei Yu, Bing Zhang, He Gao: Bright “merger-nova” from the remnant of a neutron star binary merger: A signature of a newly born, massive, millisecond magnetar . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1308.0876v1 .
10. ↑ AKH Kong, E. Kuulkers, PA Charles L. Homer: The 'off' state of GX 339-4 . In: Monthly Notice of the Royal Astronomical Society . tape 312 , 2000, pp. L49-L54 , doi : 10.1046 / j.1365-8711.2000.03334.x .
11. ^ Michael F. Bode, A. Evans: Classical novae. Cambridge Univ. Press, Cambridge 2008, ISBN 978-0-521-84330-0 .
12. ↑ Steven N. Shore: Spectroscopy of Novae - A User's Manual . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1211.3176 .
13. ↑ A. Evans, RD Gehrz: Infrared emission from novae . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1209.3193 .
14. ↑ Greg J. Schwarz et al. a .: Swift X-RAY OBSERVATIONS OF CLASSICAL NOVAE. II. THE SUPER SOFT SOURCE SAMPLE . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1110.6224v1 .
15. ↑ RD Gehrz, JW Truran, RE Williams, S. Starr Field: Nucleosynthesis in Classical Novae and Its Contribution to the Interstellar Medium . In: The Publications of the Astronomical Society of the Pacific . tape 110 , 1998, pp. 3-26 , doi : 10.1086 / 316107 .
16. ^ Andrew C. Collazzi, Bradley E. Schaefer, Limin Xiao, Ashley Pagnotta, Peter Kroll, Klaus Lochel, Arne A. Henden: The Behavior of Novae Light Curves Before Eruption . In: Astrophysics. Solar and Stellar Astrophysics . 2009, arxiv : 0909.4289v1 .
17. ↑ Novae. In: Eberfing Observatory. 2018, accessed March 17, 2019 . 
18. ^ RF Webbink, M. Livio, JW Truran: The Nature of the Recurrent Novae In: Astrophysical Journal , vol. 314, pp. 653-772, 1987, doi: 10.1086 / 165095
19. ↑ Samus NN, Kazarovets EV, Durlevich OV, Kireeva NN, Pastukhova EN: General Catalog of Variable Stars, Version GCVS 5.1 In: Astronomy Reports, 2017, vol. 61, no. 1, pp. 80-88, doi: 10.1134 / S1063772917010085
20. ↑ Angelo Cassatella: Physics of Classical Novae. Springer, Berlin 1990, ISBN 3-540-53500-4 .
21. ^ J. Mikolajewska: Symbiotic Novae . In: Astrophysics. Solar and Stellar Astrophysics . 2010, arxiv : 1011.5657 .
22. ^ M. Kato: Quite Novae with Flat Maximum - No Optical Thick Winds . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1101.2554 .
23. ^ RF Webbink, M. Livio, JW Truran: The Nature of the Recurrent Novae . In: Astrophysical Journal . tape 314 , 1987, pp. 653-772 , doi : 10.1086 / 165095 .
24. ^ MF Bode: Classical and Recurrent Nova Outbursts . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1111.4941v1 .
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