P Cygni

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P Cygni
Cygnus constellation map.svg
Red circle.svg
Location of P Cygni (circled in red)
Observation data
Epoch J2000       Equinox J2000
Constellation Cygnus
Right ascension 20h 17m 47.2020s [1]
Declination +38° 01′ 58.549″ [1]
Apparent magnitude  (V)4.82 [2] (3 to 6 [3] )
Characteristics
Spectral type B1-2 Ia-0ep [4] (B1 Iapeq [3] )
U−B color index −0.58 [5]
B−V color index +0.42 [5]
Variable type LBV [3]
Astrometry
Radial velocity (Rv)−8.9 [6]  km/s
Proper motion (μ)RA: −3.723 [1]   mas/yr
Dec.: −6.798 [1]   mas/yr
Parallax (π)0.6251 ± 0.0729  mas [1]
Distance 1,610±180 [7]   pc
Absolute magnitude  (MV)−7.9 [8]
Details
Mass 37 [9]   M☉
Radius 76 [10]   R☉
Luminosity 610,000 [10]   L☉
Surface gravity (log g)2.25 [9]   cgs
Temperature 18,700 [10]   K
Metallicity 0.29 [10] He/H
Rotational velocity (v sin i)35 [11]  km/s
Other designations
Nova Cyg 1600, 34  Cyg, JP11  3218, TD1  26474, GSC  03151-03442, TYC  3151-3442-1, AG+37° 1953, 2MASS  J20174719+3801585, ALS  11097, HD  193237, MCW  849, BD+37°3871, Hen  3-1871, PLX  4837, CEL  5017, PPM  84645, P Cyg, RAFGL  5493S, GC  28218, HIP  100044, ROT  2959, GCRV  12673, HR  7763, SAO  69773, AAVSO  2014+37A
Database references
SIMBAD data

P Cygni (34 Cygni) is a variable star in the constellation Cygnus. The designation "P" was originally assigned by Johann Bayer in Uranometria as a nova. Located about 5,300 light-years (1,560 parsecs) from Earth, it is a hypergiant luminous blue variable (LBV) star of spectral type B1-2 Ia-0ep that is one of the most luminous stars in the Milky Way.

Contents

Visibility

The star is located about 5,000 to 6,000 light-years (1,500–1,800 parsecs) from Earth. Despite this vast distance, it is visible to the naked eye in suitable dark sky locations. It was unknown until the end of the 16th century, when it suddenly brightened to 3rd magnitude. It was first observed on 18 August (Gregorian) 1600 by Willem Janszoon Blaeu, a Dutch astronomer, mathematician and globe-maker. Bayer's atlas of 1603 assigned it the miscellaneous label P and the name has stuck ever since. [12] After six years the star faded slowly, dropping below naked-eye visibility in 1626. It brightened again in 1655, but had faded by 1662. Another outburst took place in 1665; this was followed by numerous fluctuations. Since 1715 P Cygni has been a fifth magnitude star, with only minor fluctuations in brightness. Today it has a magnitude of 4.8, irregularly variable by a few hundredths of a magnitude on a scale of days. [13] The visual brightness is increasing by about 0.15 magnitude per century, attributed to a slow decrease in temperature at constant luminosity. [14]

P Cygni has been called a "permanent nova" because of spectral similarities and the obvious outflow of material, and was once treated with novae as an eruptive variable; however, its behaviour is no longer thought to involve the same processes associated with true novae. [15]

Luminous blue variable

A visual band light curve for P Cygni. The main plot is from AAVSO data. The inset plot, adapted from de Groot (1988), shows the variability for the first 400 years after the star's discovery. PCygLightCurve.png
A visual band light curve for P Cygni. The main plot is from AAVSO data. The inset plot, adapted from de Groot (1988), shows the variability for the first 400 years after the star's discovery.

P Cygni is widely considered to be the earliest known example of a luminous blue variable. However, it is far from a typical example. Typically, LBVs change in brightness with a period of years to decades, occasionally hosting outbursts where the brightness of the star increases dramatically. P Cygni has been largely unvarying both in brightness and spectrum since a series of large outbursts in the 17th century. Similar events have been seen in Eta Carinae and possibly a handful of extra-galactic objects. [18]

P Cygni does show evidence for previous large eruptions around 900, 2,100, and possibly 20,000 years ago. In more recent centuries, it has been very slowly increasing in visual magnitude and decreasing in temperature, which has been interpreted as the expected evolutionary trend of a massive star towards a red supergiant stage. [18]

Evolution

Luminous blue variables like P Cygni are very rare and short lived, and only form in regions of galaxies where intense star formation is happening. LBV stars are so massive and energetic (typically 50 times the mass of the Sun and tens of thousands of times more luminous) that they exhaust their nuclear fuel very quickly. After shining for only a few million years (compared to several billion years for the Sun) they erupt in a supernova. The recent supernova SN 2006gy was likely the end of an LBV star similar to P Cygni but located in a distant galaxy. [19] P Cygni is thought to be in the hydrogen shell burning phase immediately after leaving the main sequence. [18]

It has been identified as a possible type IIb supernova candidate in modelling of the fate of stars 20 to 25 times the mass of the Sun (with LBV status as the predicted final stage beforehand). [20]

P Cygni profile

P Cygni's characteristic and eponymous line profile for H-a P Cygni Profile-en.svg
P Cygni's characteristic and eponymous line profile for H-α

P Cygni gives its name to a type of spectroscopic feature called a P Cygni profile, where the presence of both absorption and emission in the profile of the same spectral line indicates the existence of a gaseous envelope expanding away from the star. The emission line arises from a dense stellar wind near to the star, while the blueshifted absorption lobe is created where the radiation passes through circumstellar material rapidly expanding in the direction of the observer. These profiles are useful in the study of stellar winds in many types of stars. They are often cited as an indicator of a luminous blue variable star, although they also occur in other types of star. [18] [21]

In P Cygni itself, the size of the stellar wind H-alpha emission region is 5.64±0.21 milli-arcseconds. [13] At the distance of 1,600 parsecs this is a physical size of approximately 25 stellar radii.

Companion

It has been proposed P Cygni's eruptions could be caused by mass transfer to a hypothetical companion star of spectral type B that would have a mass between 3 and 6 times the mass of the Sun and would orbit P Cygni each 7 years in a high eccentricity orbit. Infall of matter into the secondary star would produce the release of gravitational energy, part of which would cause an increase of the luminosity of the system. [22]

Related Research Articles

<span class="mw-page-title-main">Blue supergiant</span> Hot, luminous star with a spectral type of B9 (or A9) or earlier

A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They are usually considered to be those with luminosity class I and spectral class B9 or earlier, although sometimes A-class supergiants are also deemed blue supergiants.

<span class="mw-page-title-main">S Doradus</span> Star in the Large Magellanic Cloud

S Doradus is one of the brightest stars in the Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way, located roughly 160,000 light-years away. The star is a luminous blue variable, and one of the most luminous stars known, having a luminosity varying widely above and below 1,000,000 times the luminosity of the Sun, although it is too far away to be seen with the naked eye.

<span class="mw-page-title-main">Luminous blue variable</span> Type of star that is luminous, blue, and variable in brightness

Luminous blue variables (LBVs) are massive evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Large Magellanic Cloud. They are considered to be rare.

Alpha Cygni variables are variable stars which exhibit non-radial pulsations, meaning that some portions of the stellar surface are contracting at the same time other parts expand. They are supergiant stars of spectral types B or A. Variations in brightness on the order of 0.1 magnitudes are associated with the pulsations, which often seem irregular, due to beating of multiple pulsation periods. The pulsations typically have periods of several days to several weeks.

<span class="mw-page-title-main">V509 Cassiopeiae</span> Star in the constellation Cassiopeia

V509 Cassiopeiae is one of two yellow hypergiant stars found in the constellation Cassiopeia, which also contains Rho Cassiopeiae.

<span class="mw-page-title-main">Yellow hypergiant</span> Class of massive star with a spectral type of A to K

A yellow hypergiant (YHG) is a massive star with an extended atmosphere, a spectral class from A to K, and, starting with an initial mass of about 20–60 solar masses, has lost as much as half that mass. They are amongst the most visually luminous stars, with absolute magnitude (MV) around −9, but also one of the rarest, with just 20 known in the Milky Way and six of those in just a single cluster. They are sometimes referred to as cool hypergiants in comparison with O- and B-type stars, and sometimes as warm hypergiants in comparison with red supergiants.

<span class="mw-page-title-main">AG Carinae</span> Luminous variable star in the constellation Carina

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<span class="mw-page-title-main">32 Cygni</span> Binary star system in the constellation Cygnus

32 Cygni is a binary star system in the Cygnus constellation. It is a 4th magnitude star, which can be seen with the naked eye under suitably dark skies. Parallax measurements give an estimated distance of 1,000 light-years (307 parsecs) from the Earth. However, Schröder et al. (2007) suggest the actual value, after correcting for Malmquist bias, may be closer to 1,174 light-years (360 parsecs). Although it is a spectrsocopic binary with components that cannot be separated visually, it has two entries in the Henry Draper Catalogue, with identical magnitudes and positions, but showing the spectral types of the two components.

<span class="mw-page-title-main">HR Carinae</span> Star in the constellation Carina

HR Carinae is a luminous blue variable star located in the constellation Carina. It is surrounded by a vast nebula of ejected nuclear-processed material because this star has a multiple shell expanding atmosphere. This star is among the most luminous stars in the Milky Way. It has very broad emission wings on the Balmer lines, reminiscent from the broad lines observed in the spectra of O and Wolf–Rayet stars. A distance of 5 kpc and a bolometric magnitude of −9.4 put HR Car among the most luminous stars of the galaxy.

<span class="mw-page-title-main">Hypergiant</span> Rare star with tremendous luminosity and high rates of mass loss by stellar winds

A hypergiant (luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term hypergiant is defined as luminosity class 0 (zero) in the MKK system. However, this is rarely seen in literature or in published spectral classifications, except for specific well-defined groups such as the yellow hypergiants, RSG (red supergiants), or blue B(e) supergiants with emission spectra. More commonly, hypergiants are classed as Ia-0 or Ia+, but red supergiants are rarely assigned these spectral classifications. Astronomers are interested in these stars because they relate to understanding stellar evolution, especially star formation, stability, and their expected demise as supernovae. A common example of a hypergiant is UY Scuti, although being a supergiant UY Scuti is considered a hypergiant by some people.

<span class="mw-page-title-main">HD 5980</span> Triple star system in the constellation Tucana

HD 5980 is a multiple star system on the outskirts of NGC 346 in the Small Magellanic Cloud (SMC) and is one of the brightest stars in the SMC.

<span class="mw-page-title-main">HD 168607</span> Star in the constellation Sagittarius

HD 168607 is a blue hypergiant and luminous blue variable (LBV) star located in the constellation of Sagittarius, easy to see with amateur telescopes. It forms a pair with HD 168625, also a blue hypergiant and possible luminous blue variable, that can be seen at the south-east of M17, the Omega Nebula.

<span class="mw-page-title-main">55 Cygni</span> Star in the constellation Cygnus

55 Cygni is a blue supergiant star in the constellation Cygnus. It is thought to be a member of the Cygnus OB7 stellar association at about 2,700 light years.

<span class="mw-page-title-main">HD 160529</span> Luminous blue variable star in the constellation Scorpius

HD 160529 is a luminous blue variable (LBV) star located in the constellation of Scorpius. With an apparent magnitude of around +6.8 cannot be seen with the naked eye except under very favourable conditions, but it is easy to see with binoculars or amateur telescopes.

<span class="mw-page-title-main">HD 50064</span> Star in the constellation Monoceros

HD 50064 is a blue supergiant located in the constellation of Monoceros, easy to see with small telescopes.

<span class="mw-page-title-main">QU Normae</span> Star in the constellation Norma

QU Normae, also known as HR 6131, is a blue supergiant star in the constellation Norma. It is also a variable star, thought to be an α Cyg variable.

R99 is a star in the Large Magellanic Cloud in the constellation Dorado. It is classified as a possible luminous blue variable and is one of the most luminous stars known.

<span class="mw-page-title-main">BC Cygni</span> Star in the constellation Cygnus

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<span class="mw-page-title-main">RW Cygni</span> Star in the constellation Cygnus

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<span class="mw-page-title-main">R71 (star)</span> Star in the Large Magellanic Cloud

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References

  1. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  2. ↑ Ducati, J. R. (2002). "VizieR On-line Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  3. 1 2 3 Samus, N. N.; Durlevich, O. V.; et al. (2004). "VizieR Online Data Catalog: Combined General Catalogue of Variable Stars (Samus+ 2004)". VizieR On-line Data Catalog: II/250. Originally Published in: 2004yCat.2250....0S. 2250: 0. Bibcode:2004yCat.2250....0S.
  4. ↑ Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2016)". VizieR On-line Data Catalog: B/Mk. Originally Published in: Lowell Observatory (October 2014). 1. Bibcode:2014yCat....1.2023S.
  5. 1 2 Smith, L. J.; Crowther, P. A.; Prinja, R. K. (1994). "A study of the luminous blue variable candidate He 3-519 and its surrounding nebula". Astronomy and Astrophysics. 281: 833. Bibcode:1994A&A...281..833S.
  6. ↑ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv: 1606.08053 . Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID   119231169.
  7. ↑ De Almeida, E S G.; Hugbart, M.; Domiciano De Souza, A.; Rivet, J-P; Vakili, F.; Siciak, A.; Labeyrie, G.; Garde, O.; Matthews, N.; Lai, O.; Vernet, D.; Kaiser, R.; Guerin, W. (2022). "Combined spectroscopy and intensity interferometry to determine the distances of the blue supergiants P Cygni and Rigel". Monthly Notices of the Royal Astronomical Society. 515 (1): 1–12. arXiv: 2204.00372 . Bibcode:2022MNRAS.515....1D. doi: 10.1093/mnras/stac1617 .
  8. ↑ Van Genderen, A. M. (2001). "S Doradus variables in the Galaxy and the Magellanic Clouds". Astronomy and Astrophysics. 366 (2): 508–531. Bibcode:2001A&A...366..508V. doi: 10.1051/0004-6361:20000022 .
  9. 1 2 Rivet, J-P; Siciak, A.; de Almeida, E. S. G.; Vakili, F.; Domiciano de Souza, A.; Fouché, M.; Lai, O.; Vernet, D.; Kaiser, R.; Guerin, W. (2020). "Intensity interferometry of P Cygni in the H α emission line: Towards distance calibration of LBV supergiant stars". Monthly Notices of the Royal Astronomical Society. 494 (1): 218–227. arXiv: 1910.08366 . Bibcode:2020MNRAS.494..218R. doi: 10.1093/mnras/staa588 . S2CID   204788654.
  10. 1 2 3 4 Najarro, F. (2001). "Spectroscopy of P Cygni". P Cygni 2000: 400 Years of Progress. 233: 133. Bibcode:2001ASPC..233..133N.
  11. ↑ Najarro, F.; Hillier, D. J.; Stahl, O. (1997). "A spectroscopic investigation of P Cygni. I. H and HeI lines". Astronomy and Astrophysics. 326: 1117. Bibcode:1997A&A...326.1117N.
  12. ↑ Also noted in La stella nuova e peregrina comparsa l'anno 1600 sul petto del cigno, scoverta nuovamente (The new and strange star appeared in the year 1600 on the chest of the Cygnus (constellation), discovered again), by Giovanni Battista Hodierno, Published by Ignazio di Lazzari, Rome (1659).
  13. 1 2 Balan, Aurelian; Tycner, C.; Zavala, R. T.; Benson, J. A.; Hutter, D. J.; Templeton, M. (2010). "THE SPATIALLY RESOLVED Hα-EMITTING WIND STRUCTURE OF P CYGNI". The Astronomical Journal. 139 (6): 2269. arXiv: 1004.0376 . Bibcode:2010AJ....139.2269B. doi:10.1088/0004-6256/139/6/2269. S2CID   46021658.
  14. ↑ Lamers, H. J. G. L. M.; De Groot, M. J. H. (1992). "Observed evolutionary changes in the visual magnitude of the luminous blue variable P Cygni". Astronomy and Astrophysics. 257: 153. Bibcode:1992A&A...257..153L.
  15. ↑ Szkody, P. (1977). "Infrared photometry of dwarf novae and possibly related objects". The Astrophysical Journal. 217: 140. Bibcode:1977ApJ...217..140S. doi:10.1086/155563.
  16. ↑ "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
  17. ↑ de Groot, Mart (March 1988). "The most luminous stars in the universe". Irish Astronomical Journal. 18: 163–170. Bibcode:1988IrAJ...18..163D.
  18. 1 2 3 4 Israelian, G.; De Groot, M. (1999). "P Cygni: An Extraordinary Luminous Blue Variable". Space Science Reviews. 90 (3/4): 493. arXiv: astro-ph/9908309v1 . Bibcode:1999SSRv...90..493I. doi:10.1023/A:1005223314464. S2CID   118671563.
  19. ↑ Smith, Nathan; Li, Weidong; Foley, Ryan J.; Wheeler, J. Craig; Pooley, David; Chornock, Ryan; Filippenko, Alexei V.; Silverman, Jeffrey M.; Quimby, Robert; Bloom, Joshua S.; Hansen, Charles (2007). "SN 2006gy: Discovery of the Most Luminous Supernova Ever Recorded, Powered by the Death of an Extremely Massive Star like η Carinae". The Astrophysical Journal. 666 (2): 1116–1128. arXiv: astro-ph/0612617 . Bibcode:2007ApJ...666.1116S. doi:10.1086/519949. S2CID   14785067.
  20. ↑ Groh, J. H.; Meynet, G.; Ekström, S. (2013). "Massive star evolution: luminous blue variables as unexpected supernova progenitors". Astronomy & Astrophysics. 550: 4. arXiv: 1301.1519 . Bibcode:2013A&A...550L...7G. doi:10.1051/0004-6361/201220741. S2CID   119227339. L7.
  21. ↑ Robinson, Keith (2007). "The P Cygni Profile and Friends". Spectroscopy: The Key to the Stars. Patrick Moore's Practical Astronomy Series. pp. 119–125. doi:10.1007/978-0-387-68288-4_10. ISBN   978-0-387-36786-6.
  22. ↑ Kashi, Amit (2010). "An indication for the binarity of P Cygni from its 17th century eruption". Monthly Notices of the Royal Astronomical Society. 405 (3): 1924. arXiv: 0912.3998 . Bibcode:2010MNRAS.405.1924K. doi: 10.1111/j.1365-2966.2010.16582.x . S2CID   118551338.
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