Astronomy:CK Vulpeculae

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Short description: 1678 Nova seen in the constellation Vulpecula
CK Vulpeculae
File:Through the Hourglass CK Vulpeculae.tif
CK Vulpeculae taken by ALMA.[1]
Credit: ALMA (ESO/NAOJ/NRAO)/S. P. S. Eyres
Observation data
Equinox J2000.0]] (ICRS)
Constellation Vulpecula
Right ascension  19h 47m 38.0s[2]
Declination +27° 18′ 48″[2]
Apparent magnitude (V) max 2.6[2]
Characteristics
B−V color index 0.7[3]
Variable type unknown[3]
Astrometry
Distance10000+3000
−2000[4] ly
(3200+900
−600[4] pc)
Details
Luminosity0.9[3] L☉
Temperature14,000 – 100,000[3] K
Other designations
CK Vulpeculae, CK Vul, Nova Vul 1670, HR 7539, 11 Vul[5]
Database references
SIMBADdata

CK Vulpeculae (also Nova Vulpeculae 1670) is an object whose exact nature is unknown.[4] It was once considered to be the oldest reliably-documented nova. It consists of a compact central object surrounded by a bipolar nebula.

Models suggest CK Vulpeculae may not be a classic nova; rather it may be classified as a luminous red nova which is the result of two main sequence stars colliding and merging. A 2018 study found it was most likely the result of an unusual collision of a white dwarf and a brown dwarf. A 2020 article ruled out this proposed mechanism and proposes that CK Vulpeculae is an intermediate luminosity optical transient, i.e. an object in the luminosity gap between supernovae and novae.[4]

Eruptive history

Position of the 1670 Nova near Albireo
The location of CK Vulpeculae (circled in red)

CK Vulpeculae was discovered on June 20, 1670, by Voituret Anthelme and independently on July 25 by Johannes Hevelius. It had a brightness maximum of approximately magnitude 3 at its discovery after which it faded. A second maximum of approximately 2.6 magnitude was observed in March 1671, after which Johannes Hevelius and Giovanni Cassini observed it throughout spring and summer until it faded from naked-eye view in late August 1671. A last weakly visible brightness maximum of approximately 5.5 to 6 magnitude was observed by Hevelius in March 1672 and finally faded from view late May.[6]

This was the first nova for which there are multiple and reliable observations. The next nova to be documented as comprehensively was Nova Ophiuchi 1841.[6]

Identification

Visible light is in blue, submillimeter radiation map highlighted in green, and molecular emission in red.

John Flamsteed, who was elaborating his catalogue during these years, assigned the star the Flamsteed designation 11 Vulpeculae,[5] which has been noted later by Francis Baily as one of Flamsteed's lost stars, because it had not been detectable for centuries.[7]

In 1981, a point source near the centre of a small nebula was identified as CK Vulpeculae, with an estimated red magnitude of 20.7.[8][6] Later observations cast doubt on that identification,[9] and it is now known to be a background object. That object and another star are thought to be seen though dense nebulosity associated with CK Vulpeculae which causes them to vary dramatically in brightness.[10]

CK Vulpeculae now consists of a compact central object with gas flowing out at approximately 210 km/s into a bipolar nebula.[10] A 15" path of nebulosity seen in the 1980s lies at the centre of a 70" bipolar nebula.[11] A compact radio source is seen at the centre of this nebula, and an infrared point source, but it has not been detected at optical wavelengths.[3] The ionisation of the nebula and its radio emission indicate that the central source is still very hot and relatively luminous.[12][10] It is either inside of a cloud of cold (~ 15 K) dust or the cloud is in front of it from the Earth's perspective. Molecular gas in the vicinity is rich in nitrogen relative to oxygen.[12]

Properties

File:Radioactive molecules in the remains of a stellar collision CK Vulpeculae.tif

The luminosity of the central object, estimated from infrared dust emission, is about 0.9 L☉.[3] The luminosity required to energise the observed nebulosity is calculated at 3 L☉ from an object at 60,000 K[10] At the time of its eruption, the luminosity of CK Vulpeculae is calculated to have been at least 7,000,000 L☉.[4] Known ionic emission lines in the spectrum, and unidentified absorption features in the infrared indicate a temperature between 14,000 K and 100,000 K.[3]

Astronomers using the Atacama Large Millimetre Array (ALMA) and the Northern Extended Millimeter Array (NOEMA) radio telescopes to study CK Vulpeculae have found the first convincing evidence of a radioactive molecule outside the Earth's Solar System, which is aluminium monofluoride as the 26Al isotopologue.[14]

Nature of the eruption

In the past, a luminous red nova merger, very late thermal pulse, or a diffusion-induced nova have all been suggested but there are problems with all these explanations.[3] An analysis of the structures and isotopic abundances in the remaining nebula using the Atacama Large Millimeter Array (ALMA) in 2018 concluded that the nova and associated nebula were caused by the unusual merger of a white dwarf and brown dwarf between 1670 and 1672.[15] Although it was previously considered to be located about 2,280 ly (700 pc) away,[10] a 2020 paper ruled this out due to a larger distance for CK Vulpeculae making the intrinsic energy release too great for a stellar merger. Instead the 2020 paper concludes that the CK Vulpeculae outburst was an intermediate luminosity optical transient with an unknown cause.[4]

References

  1. ↑ "Through the Hourglass". https://www.eso.org/public/images/potw1841a/. Retrieved 8 October 2018. 
  2. ↑ 2.0 2.1 2.2 Downes, Ronald A; Webbink, Ronald F; Shara, Michael M; Ritter, Hans; Kolb, Ulrich; Duerbeck, Hilmar W (2001). "A Catalog and Atlas of Cataclysmic Variables: The Living Edition". The Publications of the Astronomical Society of the Pacific 113 (784): 764. doi:10.1086/320802. Bibcode: 2001PASP..113..764D. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Evans, A. et al. (2016). "CK Vul: A smorgasbord of hydrocarbons rules out a 1670 nova (and much else besides)". Monthly Notices of the Royal Astronomical Society 457 (3): 2871–2876. doi:10.1093/mnras/stw352. Bibcode: 2016MNRAS.457.2871E. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Banerjee, D. P. K.; Geballe, T. R.; Evans, A.; Shahbandeh, M.; Woodward, C. E.; Gehrz, R. D.; Eyres, S. P. S.; Starrfield, S. et al. (2020). "Near-infrared Spectroscopy of CK Vulpeculae: Revealing a Remarkably Powerful Blast from the Past". The Astrophysical Journal 904 (2): L23. doi:10.3847/2041-8213/abc885. Bibcode: 2020ApJ...904L..23B. 
  5. ↑ 5.0 5.1 Morton, Wagman (2003). Lost Stars. Blacksburg, Virginia: McDonald and Woodward. p. 494. ISBN 978-0-939923-78-6. 
  6. ↑ 6.0 6.1 6.2 Shara, M. M.; Moffat, A. F. J.; Webbink, R. F. (July 1, 1985). "Unraveling the oldest and faintest recovered nova - CK Vulpeculae (1670)". Astrophysical Journal 294: 271–285. doi:10.1086/163296. Bibcode: 1985ApJ...294..271S. 
  7. ↑ Baily, Francis (1845). The Catalogue of Stars of the British Association for the Advancement of Science. London: Richard and John E Taylor. p. 77. ISBN 978-1165133253. Bibcode: 1845tcot.book.....B. https://books.google.com/books?id=mxFfAAAAcAAJ&pg=PA77. 
  8. ↑ Shara, M. M.; Moffat, A. F. J. (July 1, 1982). "The recovery of CK Vulpeculae (Nova 1670) - The oldest 'old nova'". Astronomical Journal 258 (Part 2 Letters to the Editor): L41–L44. doi:10.1086/183826. Bibcode: 1982ApJ...258L..41S. 
  9. ↑ Naylor, T.; Charles, P. A.; Mukai, K.; Evans, A. (1992). "An observational case against nova hibernation". Monthly Notices of the Royal Astronomical Society 258 (3): 449–456. doi:10.1093/mnras/258.3.449. Bibcode: 1992MNRAS.258..449N. 
  10. ↑ 10.0 10.1 10.2 10.3 10.4 Hajduk, M.; van Hoof, P. A. M.; Zijlstra, A. A. (11 June 2013). "CK Vul: evolving nebula and three curious background stars". Monthly Notices of the Royal Astronomical Society 432 (1): 167–175. doi:10.1093/mnras/stt426. Bibcode: 2013MNRAS.432..167H. 
  11. ↑ Hajduk, M; Zijlstra, Albert A; Van Hoof, P. A. M; Lopez, J. A; Drew, J. E; Evans, A; Eyres, S. P. S; Gesicki, K et al. (2007). "The enigma of the oldest 'nova': The central star and nebula of CK Vul". Monthly Notices of the Royal Astronomical Society 378 (4): 1298–1308. doi:10.1111/j.1365-2966.2007.11825.x. Bibcode: 2007MNRAS.378.1298H. 
  12. ↑ 12.0 12.1 Kaminski, Tomasz; Menten, Karl M.; Tylenda, Romuald; Hajduk, Marcin; Patel, Nimesh A.; Kraus, Alexander (March 23, 2015). "Nuclear ashes and outflow in the eruptive star Nova Vul 1670". Nature 520 (7547): 322–4. doi:10.1038/nature14257. PMID 25799986. Bibcode: 2015Natur.520..322K. 
  13. ↑ "Stellar Corpse Reveals Origin of Radioactive Molecules - Observations using ALMA find radioactive isotope aluminium-26 from the remnant CK Vulpeculae". https://www.eso.org/public/news/eso1826/. Retrieved 31 July 2018. 
  14. ↑ Kamiński, T; Menten, K. M; Tylenda, R; Karakas, A; Belloche, A; Patel, N. A (2017). "Organic molecules, ions, and rare isotopologues in the remnant of the stellar-merger candidate, CK Vulpeculae (Nova 1670)". Astronomy & Astrophysics 607: A78. doi:10.1051/0004-6361/201731287. Bibcode: 2017A&A...607A..78K. 
  15. ↑ Eyres, Stewart; Evans, Aneurin; Zijlstra, Albert; Avison, Adam; Gehrz, Robert; Hajduk, Marcin; Starrfield, Sumner; Mohamed, Shazrene et al. (16 September 2018). "ALMA reveals the aftermath of a white dwarf--brown dwarf merger in CK Vulpeculae" (in en). Monthly Notices of the Royal Astronomical Society 481 (4): 4931. doi:10.1093/mnras/sty2554. Bibcode: 2018MNRAS.481.4931E. 

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