HD 168625

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HD 168625
HD 168625 MUSE H-alpha.png
HD 168625 and its nebula in Hydrogen-alpha with MUSE
Observation data
Epoch J2000       Equinox J2000
Constellation Sagittarius
Right ascension 18h 21m 19.548s [1]
Declination −16° 22′ 16.0572″ [1]
Apparent magnitude  (V)8.30–8.41 [2]
Characteristics
Spectral type B6Ia+ [3] (B2—B8 [4] ) May be B60 due to hypergiant designation
U−B color index +0.37 [5]
B−V color index +1.41 [5]
J−K color index 0.599
Variable type α Cygni [6]
Astrometry
Radial velocity (Rv)−4.00 [7]  km/s
Proper motion (μ)RA: −0.71±1.20 [1]   mas/yr
Dec.: +0.01±0.74 [1]   mas/yr
Parallax (π)0.6212 ± 0.0640  mas [8]
Distance approx. 5,300  ly
(approx. 1,600  pc)
Absolute magnitude  (MV)−8.39 [4]
Details [4]
Radius 105  R☉
Luminosity 380,000  L☉
Surface gravity (log g)1.74  cgs
Temperature 14,000  K
Rotational velocity (v sin i)60 km/s
Other designations
V4030 Sgr, HD 168625, BD −16°4830, SAO 161375, HIP 89963, AAVSO 1815-168
Database references
SIMBAD data

HD 168625 (V4030 Sagittarii) is a blue hypergiant star and candidate luminous blue variable located in the constellation of Sagittarius easy to see with amateur telescopes. It forms a visual pair with the also blue hypergiant (and luminous blue variable) HD 168607 and is located to the south-east of M17, the Omega Nebula.

Contents

Distance

The distance of HD 168625 and its association with the Omega Nebula and HD 168607 is in doubt; while some authors think both stars are physically associated and belong to the stellar association Serpens OB1, [9] at a distance to the Sun of 2.2 kiloparsecs (7,200  ly ), [10] or for both per Gaia Data Release 2 about 1.6 kiloparsecs (5,200 ly), [8] a 2002 study estimates this star is farther, at about 2.8 kiloparsecs (9,100 ly) and unrelated to the other two objects. [11]

Physical characteristics

A visual band light curve for V4030 Sagittarii, plotted from ASAS data V4030SgrLightCurve.png
A visual band light curve for V4030 Sagittarii, plotted from ASAS data

Assuming a distance of 2.2 kiloparsecs, the star would be 220,000 times brighter than the Sun, having a surface temperature of 12,000 K. [10] At that distance it can be calculated to be losing mass through a fierce stellar wind at roughly 1.46×10−6  solar masses per year [13] however this is to be muted somewhat as work realized in 2012 from the VLT reveal a binary star system – [14] a companion exists around 4.5 magnitudes fainter than the primary. [15]

Nebula

The most notable characteristic of HD 168625 is the presence of a nebula surrounding it that was discovered in 1994 [16] and that has been studied with the help of several instruments and observatories and telescopes that include among others the Hubble Space Telescope [11] and the VLT. [13]

Said studies show that HD 168625 is actually surrounded by two nebulae: an inner one that has an elliptical shape and a very complex structure that includes arcs and filaments, [11] and a much larger outer one discovered with the help of the Spitzer Space Telescope that has a bipolar shape and that looks like a clone of the one surrounding Sanduleak -69° 202, the progenitor of the supernova 1987A in the Large Magellanic Cloud. [17] This suggests Sanduleak −69° 202 was also a luminous blue variable as well as the possibility of HD 168625 exploding as a Type II supernova in the near future. [17]

East-north-east of the star and nebula is HD 168701 (HIP 90001), an eclipsing binary of beta Lyrae type. [18] It is at about six times the angular separation of HD 168607 viewed from the solar system and is the third very bright point to the south-east of the nebula. Its parallax of 0.7106 ± 0.0451 mas implies it is about 1,700 parsecs (5,500 ly) away. [18]

Related Research Articles

<span class="mw-page-title-main">Pistol Star</span> Hypergiant star in Sagittarius

The Pistol Star is an extremely luminous blue hypergiant star, one of the most luminous and massive known in the Milky Way. It is one of many massive young stars in the Quintuplet cluster in the Galactic Center region. The star owes its name to the shape of the Pistol Nebula, which it illuminates. It is located approximately 25,000 light-years from Earth in the direction of Sagittarius. The star has a large mass comparable to V4998 Sagittarii and a luminosity 3.3 million times that of the Sun (L☉). It would be visible to the naked eye as a 4th-magnitude star if it were not for the interstellar dust near the Center of the Milky Way that absorbs almost all of its visible light.

<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 rare, massive and 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.

<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

AG Carinae is a star in the constellation Carina. It is classified as a luminous blue variable (LBV) and is one of the most luminous stars in the Milky Way. The great distance and intervening dust mean that the star is not usually visible to the naked eye; its apparent brightness varies erratically between magnitude 5.7 and 9.0.

<span class="mw-page-title-main">Cygnus OB2-12</span> Blue hypergiant star

Cygnus OB2 #12 is an extremely luminous blue hypergiant with an absolute bolometric magnitude of −10.9, among the most luminous stars known in the galaxy. This makes the star nearly two million times more luminous than the Sun, although estimates were even higher when the star was first discovered. It is now known to be a binary, with the companion approximately a tenth as bright. A very approximate initial estimate of the orbit gives the total system mass as 120 M☉ and the period as 30 years.

<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. Notable examples of hypergiants include the Pistol Star, a blue hypergiant located close to the Galactic Center and one of the most luminous stars known; Rho Cassiopeiae, a yellow hypergiant that is one of the brightest to the naked eye; and Mu Cephei (Herschel's "Garnet Star"), one of the largest and brightest stars known.

Zeta<sup>1</sup> Scorpii Star in the constellation Scorpius.

Zeta1 Scorpii is a B-type hypergiant star in the constellation of Scorpius. It has an apparent visual magnitude which varies between 4.66 and 4.86. It is a member of the Scorpius OB1 association, and potentially of the open star cluster NGC 6231, also known as the "Northern jewel box" cluster. Around 36 times as massive as the Sun, it is also one of the most luminous stars known in the Galaxy, with an estimated bolometric luminosity of around 850,000 times that of the Sun and a radius 103 times that of the Sun.

<span class="mw-page-title-main">IRAS 17163−3907</span> Yellow hypergiant in the constellation Scorpius

IRAS 17163−3907, also known as Hen 3-1379, is a yellow hypergiant star located 13,000 light years from Earth in the constellation of Scorpius. The star is embedded in thick shells of expelled gases and dust, and owing to its appearance has been nicknamed by astronomers the "Fried Egg Nebula". Yellow hypergiants are in an extremely active phase of their evolution.

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

IRC +10420, also known as V1302 Aquilae, is a yellow hypergiant star located in the constellation of Aquila at a distance of 4-6 kiloparsecs of the Sun.

<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">AFGL 2298</span> Star in the constellation Aquila

AFGL 2298, also known as IRAS 18576+0341, is a luminous blue variable star (LBV) located in the constellation Aquila, very close to the galactic plane. Its distance is not well known; it may be anywhere between 23,000 and 42,000 light years away from the Earth. Despite being extremely luminous, it is extremely reddened by interstellar extinction, so its apparent magnitude is brighter for longer-wavelength passbands; in fact, in visual wavelengths it is completely undetectable.

<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">V1429 Aquilae</span> Star in the constellation Aquila

V1429 Aquilae is a candidate luminous blue variable multiple star system located in the constellation of Aquila. It is often referred to by its Mount Wilson Observatory catalog number as MWC 314. It is a hot luminous star with strong emission lines in its spectrum.

<span class="mw-page-title-main">Westerhout 31</span> Complex of star formation regions of the Milky Way

Westerhout 31, also known as W31, is a complex of star formation regions of the Milky Way located in the constellation of Sagittarius.

<span class="mw-page-title-main">AS 314</span> Protoplanetary nebula in the constellation Scutum

AS 314, also known as V452 Scuti, is a protoplanetary nebula once believed to be a white hypergiant star or luminous blue variable located in the constellation of Scutum. It has an apparent magnitude of 9.85 and can be seen with small telescopes.

<span class="mw-page-title-main">HD 316285</span> Star in the constellation Sagittarius

HDE 316285 is a blue supergiant star in the constellation Sagittarius. It is a candidate luminous blue variable and lies about 6,000 light years away in the direction of the Galactic Center.

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

R71 is a star in the Large Magellanic Cloud (LMC) in the constellation Mensa. It is classified as a luminous blue variable and is one of the most luminous stars in the LMC. It lies three arc-minutes southwest of the naked-eye star β Mensae.

<span class="mw-page-title-main">Westerlund 1-243</span> Luminous blue variable star undergoing an eruptive phase in Westerlund 1

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<span class="mw-page-title-main">V1936 Aquilae</span> Blue supergiant star in the constellation Aquila

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References

  1. 1 2 3 4 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.
  2. ↑ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. ↑ Chentsov, E. L.; Ermakov, S. V.; Klochkova, V. G.; Panchuk, V. E.; Bjorkman, K. S.; Miroshnichenko, A. S. (2003). "An atlas of spectra of B6-A2 hypergiants and supergiants from 4800 to 6700Å". Astronomy and Astrophysics. 397 (3): 1035–1042. Bibcode:2003A&A...397.1035C. doi: 10.1051/0004-6361:20021430 .
  4. 1 2 3 Mahy, L.; Hutsemékers, D.; Royer, P.; Waelkens, C. (2016). "Tracing back the evolution of the candidate LBV HD168625". Astronomy & Astrophysics. 594: A94. arXiv: 1608.01087 . Bibcode:2016A&A...594A..94M. doi:10.1051/0004-6361/201628584. S2CID   119243390.
  5. 1 2 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.
  6. ↑ Sterken, C.; Arentoft, T.; Duerbeck, H. W.; Brogt, E. (1999). "Light variations of the blue hypergiants HD 168607 and HD 168625 (1973-1999)". Astronomy and Astrophysics. 349: 532. Bibcode:1999A&A...349..532S.
  7. ↑ Kharchenko, N.V.; Scholz, R.-D.; Piskunov, A.E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889–896. arXiv: 0705.0878 . Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID   119323941.
  8. 1 2 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. ↑ Chentsov, E.L.; Gorda, E.S. (2004). "Spatial Closeness of the White Hypergiants HD 168607 and HD 168625". Astronomy Letters. 30 (7): 145–180. Bibcode:2004AstL...30..461C. doi:10.1134/1.1774398. S2CID   122348932.
  10. 1 2 Nazé, Y.; Rauw, G.; Hutsemékers, D. (2012). "The first X-ray survey of Galactic luminous blue variables". Astronomy & Astrophysics . 538: A47. arXiv: 1111.6375 . Bibcode:2012A&A...538A..47N. doi:10.1051/0004-6361/201118040. S2CID   43688343. A47.
  11. 1 2 3 Pasquali, A.; Nota, A.; Smith, L.J.; Akiyama, S.; Messineo, M.; Clampin, M. (2002). "Multiwavelength Study of the Nebula Associated with the Galactic LBV Candidate HD 168625". The Astronomical Journal . 124 (3): 1625–1635. arXiv: astro-ph/0207613 . Bibcode:2002AJ....124.1625P. doi:10.1086/341820. S2CID   118968760.
  12. ↑ "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
  13. 1 2 Umana, G.; Buemi, C.S.; Trigilio, C.; Leto, P.; Hora, J.L. (2010). "Spitzer, Very Large Telescope, and Very Large Array Observations of the Galactic Luminous Blue Variable Candidate HD 168625". The Astrophysical Journal . 718 (2): 1036–1045. Bibcode:2010ApJ...718.1036U. doi: 10.1088/0004-637X/718/2/1036 .
  14. ↑ Martayan, C.; Lobel, A.; Baade, D.; Blomme, R.; Frémat, Y.; Lebouquin, J.-B.; Selman, F.; Girard, J.; Mérand, A.; Montagnier, G.; Patru, F.; Mawet, D.; Martins, F.; Rivinius, Th.; Štefl, S.; Zorec, J.; Semaan, T.; Mehner, A.; Kervella, P.; Sana, H.; Schödel, R. (2012). "On the Binarity of LBV Stars". ASP Conference Proceedings. 464: 293. Bibcode:2012ASPC..464..293M.
  15. ↑ Martayan, C.; Lobel, A.; Baade, D.; Mehner, A.; Rivinius, T.; Boffin, Henry M. J.; Ronny, B.; Girard, J.; Mérand, A.; Montagnier, G.; Patru, F.; Mawet, D.; Martins, F.; Rivinius, Th.; Štefl, S.; Zorec, J.; Semaan, T.; Mehner, A.; Kervella, P.; Sana, H.; Schödel, R. (2016). "Luminous blue variables: An imaging perspective on their binarity and near environment" (PDF). Astronomy & Astrophysics . 587: A115. arXiv: 1601.03542 . Bibcode:2016A&A...587A.115M. doi:10.1051/0004-6361/201526578. S2CID   1755296. A115.
  16. ↑ Hutsemekers, D.; vanDrom, E.; Gosset, E.; Melnick, J. (1994). "A dusty nebula around the luminous blue variable candidate HD 168625". Astronomy and Astrophysics . 2904: 906–914. Bibcode:1994A&A...290..906H.
  17. 1 2 Smith, Nathan (2007). "Discovery of a Nearby Twin of SN 1987A's Nebula around the Luminous Blue Variable HD 168625: Was Sk -69 202 an LBV?". The Astronomical Journal . 133 (3): 1034–1040. arXiv: astro-ph/0611544 . Bibcode:2007AJ....133.1034S. doi:10.1086/510838. S2CID   17598600.
  18. 1 2 "HD 168701". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2021-01-05.
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