V509 Cassiopeiae

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V509 Cassiopeiae
V509CasLightCurve.png
The visual band light curve for V509 Cassiopeiae, adapted from Percy and Zsoldos (1992) [1]
Observation data
Epoch J2000.0        Equinox J2000.0
Constellation Cassiopeia
Right ascension 23h 00m 05.1s [2]
Declination +56° 56′ 43″ [2]
Apparent magnitude  (V)+4.6 - +6.1 [3]
Characteristics
Spectral type G0Ia0 (K5Ia0 - A6Ia+ [4] ) [5]
U−B color index +1.33 [6]
B−V color index +1.0 - +1.7 [5]
Variable type SRd [3]
Astrometry
Radial velocity (Rv)−50.20 [7]  km/s
Proper motion (μ)RA: −2.787 [8]   mas/yr
Dec.: −2.054 [8]   mas/yr
Parallax (π)0.2078 ± 0.0899  mas [8]
Distance 4,810±430 [9]   pc
Absolute magnitude  (MV)−8.6 (variable) [5]
Details
Mass 11 [5]   M☉
Radius 390-910 [5]   R☉
Luminosity 269,000 [9] (180,000 [10] -400,000) [5]   L☉
Temperature 4,000-8,000 [5]   K
Metallicity [Fe/H]0.0 [11]   dex
Other designations
HR  8752, HD  217476, FK5  3839, HIP  113561, SAO  35039, AAVSO  2255+56
Database references
SIMBAD data

V509 Cassiopeiae (V509 Cas or HR 8752) is one of two yellow hypergiant stars found in the constellation Cassiopeia, which also contains Rho Cassiopeiae.

Contents

HR 8752 is around 15,700 light-years from Earth. It has an apparent magnitude that has varied from below +6 in historical times to a peak of +4.6 and now around +5.3 and is classified as a semiregular variable star of type SRd. It is undergoing strong mass loss as part of its rapid evolution and has recently passed partway through the yellow evolutionary void by ejecting around a solar mass of material in 20 years. [5]

A hot main sequence companion (B1V) was described in 1978 on the basis of a colour excess in the ultraviolet.

Observations

Brightness

HR 8752 is a naked eye star but it has no Bayer or Flamsteed designation, and is not recorded in other catalogues before the 19th century. When first recorded in the Radcliffe Observatory catalogue in 1840 it was 6th magnitude, and it is assumed it had been 6th magnitude or fainter before then. The star is slightly variable on a timescale of around a year, but the average brightness increased steadily, reaching magnitude 5.0 in the 1950s. [3] [12]

The brightness climbed to magnitude 4.75 by 1973, but the exact onset of this event was not well observed. [13] Since then the star has been studied much more closely. It peaked at magnitude 4.6 in 1976, then dropped quickly to magnitude 4.9 by 1979, then oscillated between magnitudes 4.75 and 4.85 for the next decade. Since then the brightness has generally decreased, with somewhat irregular variations of less than a tenth of a magnitude, to magnitude 5.3 in 2000 and may have stabilised at that level. [3]

There are possible historical records of new stars in Cassiopeia that could correspond to earlier outbursts of HR 8752, but the association is highly speculative. [5]

Spectrum

Spectral types and colour comparisons for HR 8752 have been made regularly for over a century. The star was recognised as somewhat unusual and probably highly luminous, but not variable. It was actually proposed as a spectral standard for type G0Ia. [14]

The colour of the star as measured by the difference between blue and visual magnitudes (B−V) may have decreased slightly from about 1.2 in 1900 to 0.8 in the 1960s. Measurements in different eras are not always calibrated to the same spectral bands, and the values have to be de-reddened to account for interstellar extinction, but the small change corresponds to records of the spectrum and are considered to be real. The colour then reddened dramatically to a B−V value of as much as 1.6 magnitudes in 1973, dropped rapidly to 0.02 by 2000, and has remained about constant since then. The detailed observations available since 1960 also show rapid colour variations of about 0.2 magnitudes on scales of 1–5 years super-imposed on the overall trends. [5]

The spectral type over the same period has changed from a G0 hypergiant at the start of the 20th century, to early K in 1973, then rapidly back to G0 by 1977, continuing to reach A6 Ia+ in 2011. These spectral types are compatible with the observed colour changes, indicating changes in the temperature of the star or its dense winds. The spectrum contains nitrogen and helium emission lines with unusual P Cygni profiles, including "inverse P Cygni" and double-peaked line profiles. Forbidden NII lines and a triple-peaked Hα line have strengthened dramatically since 1993, and the profiles have also changed indicating developments in circumstellar material probably ejected from the star. [4]

Properties

It appears that HR 8752 is not just varying in brightness and fluctuating in temperature and size like most unstable stars, but is actually undergoing a secular evolutionary shift from cooler to hotter temperatures.

The temperature can be estimated with some accuracy from the spectral and colour observations. The calculated effective temperature increased from 4,500K in 1900 to 5,000K in 1960. At that stage the luminosity was around 243,000 L☉ and the radius 680 R☉.

The star then varied erratically until 1973 when it rapidly expanded and cooled. A detailed spectral analysis in 1977 reported a temperature low of 4,000K, with a peak luminosity in 1976 of 400,000 L☉ with a radius of over 900 R☉. The surface gravity at this time was calculated to be log(g) = -2, indicating that the visible surface was effectively detached from the star. The star then rapidly returned to around its previous temperature of 5,000K, a luminosity of 316,000 L☉, and radius of 776 R☉. [15]

Starting in 1985, HR 8752 began a startling change, increasing in temperature to around 8,000K and decreasing in size to 400 R☉ by 2000, with a luminosity of 213,000 L☉. Since then the physical parameters have been more stable although the stellar wind continues to change. The surface gravity has returned to a more normal value for a luminous supergiant near log(g) = 1.0. This change means that in a few decades the star has passed through a region of instability on the H–R diagram where no stars are observed, an evolutionary change that has not been observed in any other star. [5]

Elemental abundances derived from the spectrum indicate approximately solar metallicity, although some elements are enhanced due to the evolutionary state of HR 8752. [15] [16]

Evolutionary state

HR 8752 in comparison to other yellow hypergiants and luminous blue variables Lbvstar.png
HR 8752 in comparison to other yellow hypergiants and luminous blue variables

Prior to 1973, HR 8752 was a cool yellow hypergiant with an early G spectral type. Following a dramatic shedding of its outer layers, it has now jumped to mid-A hypergiant and is not expected to return to its cool state. Models of a 25-40 M☉ ZAMS star show it crossing the "yellow evolutionary void" instability region first towards cooler temperatures, then later back towards hotter temperatures. The yellow evolutionary void is named because very few stars are found in that part of the H–R diagram. This is likely to be because the evolution of stars with such parameters is extremely rapid, perhaps even almost instant in astronomical terms.

The first crossing of the yellow evolutionary void is very rapid but the star does not experience major instability. The second crossing, returning to hotter temperatures after a time as a yellow hypergiant, involves crossing a region, or possibly two regions, where the star experiences major instability, expected to show as episodes of strong mass loss. HR 8752 has crossed the first of the two major zones of instability and is expected to migrate to even hotter temperatures over a timescale on the order of a thousand years. Based on its current observed state, HR 8752 is estimated to now have 11 M☉ left from an initial 25 M☉ and is likely to become a relatively low-luminosity luminous blue variable before evolving further into a Wolf–Rayet star. [5]

The ultimate fate of all massive stars is a core collapse and some sort of supernova explosion. Below about 20 M☉ this is expected to occur as a type II supernova from a red supergiant progenitor. More massive stars evolve into Wolf–Rayet stars before exploding as a type Ib or Ic supernova. For some intermediate range of masses, stars are thought to undergo core collapse at the yellow hypergiant or LBV stage of their lives, resulting in a type IIb or perhaps IIn supernova. HR 8752 may be such a star, and may never make it beyond its current evolutionary state before exploding. [17]

Possible binary

HR 8752 may have a companion. Measurements of the ultraviolet spectral distribution show an excess that corresponds to the output of a B1 main-sequence star. The absolute magnitude was estimated at -4.5, approximately 40 times fainter than the primary at visual wavelengths. Although the stars must be fairly close (< 1400AU), no radial velocity variations have been detected in the spectral lines of the primary, and no lines are observed which can be attributed directly to the secondary. The observed spectrum may be mostly from a shell surrounding both stars. [18] It has been suggested that some variations in spectral line profiles are caused by variations in colliding winds or disturbances of previously ejected material, caused during a periastron passage of the companion. [4]

Related Research Articles

<span class="mw-page-title-main">Supergiant</span> Type of star that is massive and luminous

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<span class="mw-page-title-main">Red supergiant</span> Stars with a supergiant luminosity class with a spectral type of K or M

Red supergiants (RSGs) are stars with a supergiant luminosity class and a stellar classification K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Antares A are the brightest and best known red supergiants (RSGs), indeed the only first magnitude red supergiant stars.

<span class="mw-page-title-main">Cassiopeia (constellation)</span> Constellation in the northern celestial hemisphere

Cassiopeia is a constellation and asterism in the northern sky named after the vain queen Cassiopeia, mother of Andromeda, in Greek mythology, who boasted about her unrivaled beauty. Cassiopeia was one of the 48 constellations listed by the 2nd-century Greek astronomer Ptolemy, and it remains one of the 88 modern constellations today. It is easily recognizable due to its distinctive 'W' shape, formed by five bright stars.

<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">Rho Cassiopeiae</span> Yellow hypergiant star in the constellation Cassiopeia

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<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.

<span class="mw-page-title-main">Mu Cephei</span> Red supergiant star in the constellation Cepheus

Mu Cephei, also known as Herschel's Garnet Star, Erakis, or HD 206936, is a red supergiant or hypergiant star in the constellation Cepheus. It appears garnet red and is located at the edge of the IC 1396 nebula. Since 1943, the spectrum of this star has served as a spectral standard by which other stars are classified.

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

Phi Cassiopeiae is a multiple star in the constellation Cassiopeia with a combined apparent magnitude of +4.95. The two brightest components are A and C, sometimes called φ1 and φ2 Cas. φ Cas A is an F0 bright supergiant of magnitude 4.95 and φ Cas C is a 7.08 magnitude B6 supergiant at 134".

<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">HR Carinae</span> Star in the constellation Carina

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<span class="mw-page-title-main">6 Cassiopeiae</span> Star in the constellation Cassiopeia

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<span class="mw-page-title-main">VY Canis Majoris</span> Star in the constellation Canis Major

VY Canis Majoris is an extreme oxygen-rich (O-rich) red hypergiant (RHG) or red supergiant (RSG) and pulsating variable star 1.2 kiloparsecs from the Solar System in the slightly southern constellation of Canis Major. It is one of the largest known stars, one of the most luminous and massive red supergiants, and one of the most luminous stars in the Milky Way.

<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.

<span class="mw-page-title-main">HD 33579</span> Star in the constellation Dorado

HD 33579 is a white/yellow hypergiant and one of the brightest stars in the Large Magellanic Cloud (LMC). It is a suspected variable star.

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

TZ Cassiopeiae(TZ Cas, HIP 117763, SAO 20912) is a variable star in the constellation Cassiopeia with an apparent magnitude of around +9 to +10. It is approximately 8,400 light-years away from Earth. The star is a red supergiant star with a spectral type of M3 and a temperature around 3,600 K.

<span class="mw-page-title-main">IRC +10420</span> Star in the constellation Aquila

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

PZ Cassiopeiae is a red supergiant star located in the constellation of Cassiopeia, and a semi-regular variable star.

<span class="mw-page-title-main">HD 179821</span> Star in the constellation Aquila

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<span class="mw-page-title-main">HR 5171</span> Star in the constellation Centaurus

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<span class="mw-page-title-main">B324</span> Star in the Triangulum Galaxy

B324 is a yellow hypergiant in the Triangulum Galaxy, located near the giant H II region IC 142 around 2.7 million light years away. It is the brightest star in the Triangulum Galaxy in terms of apparent magnitude.

References

  1. ↑ Percy, J. R.; Zsoldos, E. (September 1992). "Photometry of yellow semiregular variables : HR 8752 (= V 509 Cassiopeiae)". Astronomy and Astrophysics. 263: 123–128. Bibcode:1992A&A...263..123P . Retrieved 26 November 2021.
  2. 1 2 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv: 0708.1752 . Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID   18759600.
  3. 1 2 3 4 Zsoldos, E. (1986). "Historical light curve of HR 8752". The Observatory. 106: 156. Bibcode:1986Obs...106..156Z.
  4. 1 2 3 Lobel, A.; De Jager, K.; Nieuwenhuijzen, H. (2013). "Long-term Spectroscopic Monitoring of Cool Hypergiants HR 8752, IRC+10420, and 6 Cas near the Yellow Evolutionary Void". 370 Years of Astronomy in Utrecht. Proceedings of a Conference Held 2–5 April. 470: 167. Bibcode:2013ASPC..470..167L.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 Nieuwenhuijzen, H.; De Jager, C.; Kolka, I.; Israelian, G.; Lobel, A.; Zsoldos, E.; Maeder, A.; Meynet, G. (2012). "The hypergiant HR 8752 evolving through the yellow evolutionary void" (PDF). Astronomy & Astrophysics. 546: A105. Bibcode:2012A&A...546A.105N. doi: 10.1051/0004-6361/201117166 .
  6. ↑ Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  7. ↑ 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.
  8. 1 2 3 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR.
  9. 1 2 Klochkova, V. G. (2019). "Unity and Diversity of Yellow Hypergiants Family". Astrophysical Bulletin. 74 (4): 475–489. arXiv: 1911.09387 . Bibcode:2019AstBu..74..475K. doi:10.1134/S1990341319040138. S2CID   208202411.
  10. ↑ van Genderen, A. M.; Lobel, A.; Nieuwenhuijzen, H.; Henry, G. W.; De Jager, C.; Blown, E.; Di Scala, G.; Van Ballegoij, E. J. (2019). "Pulsations, eruptions, and evolution of four yellow hypergiants". Astronomy and Astrophysics. 631: A48. arXiv: 1910.02460 . Bibcode:2019A&A...631A..48V. doi:10.1051/0004-6361/201834358. S2CID   203836020.
  11. ↑ Fry, M. A.; Aller, L. H. (1975). "A comparison of galactic and Large Magellanic Cloud G-type supergiants by a method of spectrum synthesis". Astrophysical Journal Supplement Series. 29: 55. Bibcode:1975ApJS...29...55F. doi:10.1086/190332.
  12. ↑ Percy, J. R.; Zsoldos, E. (1992). "Photometry of yellow semiregular variables - HR 8752 (= V509 Cassiopeiae)". Astronomy and Astrophysics. 263: 123. Bibcode:1992A&A...263..123P. ISSN   0004-6361.
  13. ↑ Rufener, F. (1976). "Second catalogue of stars measured in the Geneva Observatory photometric system". Astronomy and Astrophysics. 26: 275. Bibcode:1976A&AS...26..275R.
  14. ↑ Walker, E. N. (1983). "B and V photometry of HR 8752". Monthly Notices of the Royal Astronomical Society. 203 (2): 403–408. Bibcode:1983MNRAS.203..403W. doi: 10.1093/mnras/203.2.403 .
  15. 1 2 Lambert, D. L.; Luck, R. E. (1978). "Spectrum variations of the superluminous star HR 8752". Monthly Notices of the Royal Astronomical Society. 184 (3): 405. Bibcode:1978MNRAS.184..405L. doi: 10.1093/mnras/184.3.405 .
  16. ↑ Luck, R. E. (1975). "An analysis of the superluminous star HR 8752". Astrophysical Journal. 202: 743. Bibcode:1975ApJ...202..743L. doi: 10.1086/154028 .
  17. ↑ Groh, J. H.; Meynet, G.; Ekström, S. (2013). "Massive star evolution: Luminous blue variables as unexpected supernova progenitors". Astronomy & Astrophysics. 550: L7. arXiv: 1301.1519 . Bibcode:2013A&A...550L...7G. doi:10.1051/0004-6361/201220741. S2CID   119227339.
  18. ↑ Stickland, D. J.; Harmer, D. L. (1978). "The discovery of a hot companion to HR 8752". Astronomy and Astrophysics. 70: L53. Bibcode:1978A&A....70L..53S.
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