Bright red nova

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Photo of the prototype of the bright red Nova V838 Mon

Luminous red novae , or red novae for short , are a rare class of eruptive variable stars (a subclass of variable stars ). This class of stars develops an intense red color during an outbreak.

properties

The Luminous Red Novae include the prototype V838 Mon V4332 Sgr and V1309 Sco as well as the extragalactic stars M31RV, NGC300 OT2008, M85 OT2006-1 and M99 PTF10FQS. Although their optical light curve with a steep rise and slow fall resembles that of classic novae , there are a number of differentiating features:

  • The expansion speed of the shell accelerated during the eruption is 100 km / s instead of more than 1,000 km / s
  • the lack of highly ionized spectral lines
  • in classic novae, part of the white dwarf is blown off during the eruption. A corresponding signature can not be detected in the spectra of bright red novas.
  • the low temperature of the shed envelope a few weeks after the eruption of only 900  K in the case of V838 Mon and the occurrence of a strong infrared excess .
  • in the late stage, the spectrum of an M or L supergiant shows up
  • The luminosity of the bright red nova of around one million solar luminosities is too great in relation to the speed of the decrease in brightness for classic novas and too low for a supernova

term

In addition to the terms red nova or luminous red nova, these stars are also referred to as intermediate-luminosity transient, intermediate-luminosity optical transients or intermediate-luminosity red transients. These terms are interpreted a little wider than the term red nova, as they all contain bursts of stars with a maximum luminosity between that of a classic nova and a supernova . One type of eruption that is classified as an Intermediate-Luminosity Optical Transients but not a Luminous Red Novae is a large eruption of a Luminous Blue Variable . The discovery of this new class of variable stars is the result of systematic searches for supernovae in nearby galaxies.

Models

To explain the eruptions, the following models have been proposed:

  • An atypical nova outbreak based on a thermonuclear runaway on the surface of a white dwarf with a low mass of only 0.2 solar masses. In classical novas , the mass of the white dwarf is more than 0.5 solar masses.
  • Thermal pulses occur on or near the asymptotic giant branch when carbon ignites explosively in the core of the star . The lack of a circumstellar envelope, which is typical of stars on the Asymptotic Giant Branch, makes this scenario unlikely.
  • In a helium flash in a massive star, helium ignites in the core and the reaction produces carbon . This process of explosive burning of helium can, in some cases, lead to a large loss of mass with the ejection of a circumstellar shell.
  • An atypical supernova of the type IIn, which is exposed to strong circumstellar extinction , could reproduce the light curve of the red novae.
  • A merger burst through
  1. the fusion of two stars in a binary system: When the two stars have been approximated to the point that they have a common shell forming, then spirals of smaller companions in the larger component in, as it by friction is braked, and the reaction of the kinetic energy leads while ejecting an expanding envelope. For the binary star KIC 9832227 , it was originally assumed that such an event would occur in 2022. However, this turned out to be a mistake due to a typo.
  2. Capturing an exoplanet could release the observed energies. In recent years, many exoplanets have been discovered in narrow orbits around their central stars. If the star and the planet get too close, their atmospheres begin to interact. This increases friction and the planet crashes into the star. The energy released is sufficient to ignite the deuterium burning in the star's atmosphere and as a result the brightness increases sharply within a few days, as observed.

Observations

The models of merger bursts and the bursts of massive AGB stars with strong extinction were confirmed by observations .

Merger bursts

V1309 Sco

For the bright red Nova V1309 Sco that erupted in 2008, photometric data are available from the years before the eruption. During this period, there was an overcast light change with a period of 1.4 days. The change in light was typical for a contact system. The period decreased exponentially in the six years before the outbreak and the light curve was highly variable. In the year before the eruption, no more overcast light change was detectable. The total brightness of V1309 Sco increased continuously over the years, only to decrease by 1 mag in 2007  . In the following year the brightness only increased slowly, only to reach the maximum within a few weeks with an outbreak amplitude of 10 mag.

According to simulation calculations, the predecessor of the Red Nova was a binary star with a total mass of around 2 solar masses.

V838 Mon

The outbreak was discovered on January 6, 2002. A comparison with archive images showed that it must have taken place around January 1, 2002. The first outbreak was relatively unspectacular and comparable to the behavior of a star of the Nova type . A second outbreak was discovered on February 2, 2002. V838 Mon, in contrast to novae or supernovae, hardly lost any matter at high speed during this eruption , but instead expanded enormously and transformed into a cool supergiant with a diameter of over 1,560 million kilometers. From 2004 to 2006, the observations showed signs of a blue companion star. This is what the ever expanding envelope seems to have reached around December 2005. Finally, in October 2006, the shell reached dimensions in which the companion was completely swallowed.

SN 2009ip

A merger burst can also lead to eruptions, the luminosity of which significantly exceeds that of luminous red novae. The Supernova Impostor SN 2009ip could be the result of a merger of a supermassive star with a mass of around 100 solar masses and a massive star of around 30 solar masses. The time scales for this outbreak correspond to those of a merger burst like V838 Mon, but the luminosities are several orders of magnitude higher. However, the event could also have been caused by an unusual core collapse supernova or a large eruption of a luminous blue variable .

Explosive processes with super AGB stars

The group of red novae that do not result from a merger burst include SN 2008S, NGC300 OT2008, M85 OT2006-1, SN 2010da, SN 2010dn, PTF 10acbp, and M99 PTF10FQS. They share the following characteristics:

  • The predecessor cannot be detected optically because the optical radiation is absorbed by circumstellar dust
  • Infrared brightness places the previous star at the top of the AGB development
  • The absolute visual brightness during the outbreak reaches between −13 and −15
  • During the eruption, narrow emission lines with speeds significantly less than 3000 km / s appear
  • There is evidence of circumstellar dust in the near and mid-infrared, probably from carbonates instead of silicates is
  • The forerunner star does not survive the eruption

The birth of a massive white dwarf , a faint core collapse supernova or the eruption of a massive star have been discussed as the cause of this subgroup . The observation data best correspond to the interpretation of the birth of a massive white dwarf from a massive AGB star of around 10 solar masses. However, it cannot be ruled out that they are former red supergiants on the way to warmer temperatures.

Individual evidence

  1. ↑ Mansi M. Kasliwal et al .: PTF10FQS: A Luminous Red Nova in the Spiral Galaxy Messier 99 . In: Astrophysics. Solar and Stellar Astrophysics . 2010, arxiv : 1005.1455v1 .
  2. ^ A. Rau, SR Kulkarni, EO Ofek, L. Yan: Spitzer Observations of the New Luminous Red Nova M85 OT2006-1 . In: The Astrophysical Journal . tape 659 , no. 2 , 2007, p. 1536-1540 , doi : 10.1086 / 512672 .
  3. ↑ Todd A. Thompson, José L. Prieto, KZ Stanek, Matthew D. Kistler, John F. Beacom, Christopher S. Kochanek: A New Class of Luminous Transients and A First Census of Their Massive Stellar Progenitors . In: The Astrophysical Journal . tape 705 , no. 2 , 2009, p. 1364-1384 , doi : 10.1088 / 0004-637X / 705/2/1364 .
  4. ↑ Noam Soker and Amit Kashi: The Energy Source of Intermediate Luminosity Optical Transients . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1107.3454 .
  5. ^ E. Mason, M. Diaz, RE Williams, G. Preston, T. Bensby: The peculiar nova V1309 Scorpii / nova Scorpii 2008 - A candidate twin of V838 Monocerotis . In: Astronomy and Astrophysics . tape 516 , 2010, p. A108 , doi : 10.1051 / 0004-6361 / 200913610 .
  6. ↑ heise online: But no star explosion in 2022: Typing errors discovered in data. Retrieved on September 19, 2018 (German).
  7. ↑ Quentin J Socia, William F Welsh, Donald R Short, Jerome A Orosz, Ronald J Angione: KIC 9832227: Using Vulcan Data to Negate the 2022 Red Nova Merger Prediction . In: The Astrophysical Journal . tape 864 , no. 2 , September 7, 2018, ISSN  2041-8213 , p. L32 , doi : 10.3847 / 2041-8213 / aadc0d ( iop.org [accessed September 19, 2018]).
  8. ↑ Lawrence A. Molnar, Daniel Van Noord, Karen Kinemuchi, Jason P. Smolinski, Cara E. Alexander, Henry A. Kobulnicky, Evan M. Cook, Byoungchan Jang, Steven D. Steenwyk: KIC 9832227: A red nova precursor , American Astronomical Society Meeting 229, 2017, p. 417.04. bibcode : 2017AAS ... 22941704M
  9. ↑ Lawrence A. Molnar, Daniel M. Van Noord, Karen Kinemuchi, Jason P. Smolinski, Cara E. Alexander, Evan M. Cook, Byoungchan Jang, Henry A. Kobulnicky, Christopher J. Spedden, Steven D. Steenwyk: Prediction of a Red Nova Outburst in KIC 9832227 . In: The Astrophysical Journal . tape 840 , no. 1 . IOP Publishing, May 1, 2017, p. 1 , doi : 10.3847 / 1538-4357 / aa6ba7 , arxiv : 1704.05502 (English, iop.org ).
  10. ↑ Noam Soker and Amit Kashi: Formation of Bipolar Planetary Nebulae by Intermediate-Luminosity Optical Transients . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1108.2257 .
  11. ↑ CS Kochanek et al .: A Survey About Nothing: Monitoring a Million Supergiants for Failed Supernovae . In: Astrophysics. Solar and Stellar Astrophysics . 2008, arxiv : 0802.0456v1 .
  12. ↑ R. Tylenda, M. Hajduk, T. Kamiński, A. Udalski, I. Soszyński, M. K Szymański, M. Kubiak, G. Pietrzyński, R. Poleski, Ł Wyrzykowski, K. Ulaczyk: V1309 Scorpii: merger of a contact binary . In: Astrophysics. Solar and Stellar Astrophysics . November 1, 2010, arxiv : 1012.0163 .
  13. ↑ K. Stepien: Evolution of the progenitor binary of V1309 Scorpii before merger . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1105.2627 .
  14. ↑ International Astronomical Union Circular No. 7785
  15. ↑ International Astronomical Union Circular No. 7790
  16. ↑ International Astronomical Union Circular No. 7816
  17. ↑ bibcode : 2005A & A ... 434.1107M
  18. ↑ http://www.astronomerstelegram.org/?read=803
  19. ↑ http://www.astronomerstelegram.org/?read=966
  20. ↑ Noam Soker, Amit Kashi: Explaining the supernova impostor sn 2009ip as mergerburst . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1211.5388 .
  21. ↑ DM Szczygieł, JL Prieto, CS Kochanek, KZ Stanek, TA Thompson, JF Beacom, PM Garnavich, CE Woodward: Dust To Dust: 3 Years in the Evolution of the Unusual SN 2008S . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1202.0279v1 .
  22. ^ Roberta M. Humphreys, Howard E. Bond, Alceste Z. Bonanos, Kris Davidson, LAG Berto Monard, Jose L. Prieto, Frederick M. Walter: The Photometric and Spectral Evolution of the 2008 Luminous Optical Transient in NGC 3001 . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1109.5131v1 .