V4998 Sagittarii

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V4998 Sagittarii
LBV G0.120-0.048.jpg
V4998 Sagittarii and its surrounding shell nebula. The nebula appears as a transparent bubble-like body encircling the star.
Credit: HST\NIMCOS
Observation data
Epoch J2000       Equinox J2000
Constellation Sagittarius
Right ascension 17h 46m 05.625s [1]
Declination −28° 51′ 31.92″ [1]
Characteristics
Evolutionary stage LBV [2] [3]
Apparent magnitude  (B)19.5 [1]
Apparent magnitude  (R)17.2 [1]
Apparent magnitude  (J)12.534 [1]
Apparent magnitude  (H)9.239 [1]
Apparent magnitude  (K)7.462 [1]
Variable type LBV [2]
Astrometry
Distance 8,000 [2]   pc
Details
Radius 463 [lower-alpha 1]   R☉
Luminosity 4,000,000 [2]   L☉
Temperature 12,000 [4]   K
Other designations
V4998 Sagittarii, LBV G0.120-0.048, LBV3, 2MASS  J17460562-2851319, SSTGC  595621
Database references
SIMBAD data

V4998 Sagittarii is a luminous blue variable star (LBV) in the constellation of Sagittarius. Located some 25,000 light-years away, the star is positioned about 7 pc (23 ly) away from a starburst cluster known as the Quintuplet cluster. It has an ejection nebula measuring over 0.8 pc in diameter, formed 5000-10,000 years ago through large eruptions. The star has a large mass comparable to the Pistol Star and a luminosity of around 4 million times the Sun (L☉). This places the star as one of the most massive and luminous stars known.

Contents

Observational history

Quintuplet cluster region centred on the Pistol Star, with V4998 Sgr at top right Quintuplet cluster region (1002.3379).jpg
Quintuplet cluster region centred on the Pistol Star, with V4998 Sgr at top right

The star was first discovered in a 1993 survey that searched for bright near-infrared sources within 0.55°2 of the Galactic Center. The survey used 1–20 micron photometry and used a two channel InSb detector on the 1 meter ANU telescope in Australia. 50 objects were targeted and most of them had bolometric magnitudes below -5. The star itself was observed in May 1987. Its position, JHKLNMQ magnitudes, right ascension, declination, and silicate absorption were noted. The survey was conducted by Tetsuya Nagata, A. R. Hyland, S. M. Straw, Shuji Sato, and Kimiaki Kawara. The survey named the star NHS93 22; NHS standing for the three leading scientists in the survey (Nagata, Hyland, and Straw), 93 signifying the date of discovery, and 22 indicating that it was the 22nd star observed. [5]

The next observation was made by the 2MASS survey, which took place in 1997-2001. The star was designated 2MASS J17460562-2851319 and its position, luminosity, and JHKs magnitudes were catalogued. [1] After that, the star was observed in a 2001 survey called the Study of Long Period Variables stars near the Galactic Centre. The survey named the star GMC2001 10-1, GMC standing for Glass, Matsumoto, and Carter. [6] It was observed by the Infrared Array Camera on board the Spitzer Space Telescope in a 2008 survey covering 2.0 by 1.4 degrees (280 by 210 pc) and was given the name SSTGC 595621. [7] It was also observed by a 2009 near-infrared survey that targeted the Galactic Center. The star was designated MKN2009 in that survey, MKN standing for the three leading scientists (Matsunaga, Kawadu, and Nishiyama) and 2009 specifying the date of the survey. [8]

A near-infrared (K band) light curve for V4998 Sagittarii, adapted from Mauerhan et al. (2010) V4998SgrLightCurve.png
A near-infrared (K band) light curve for V4998 Sagittarii, adapted from Mauerhan et al. (2010)

A narrowband imaging survey of the Galactic Center region conducted by the Hubble Space Telescope (HST) Near Infrared Camera and Multi Object Spectrometer (NICMOS) revealed LBV G0.120-0.048 as a strong source of Paschen-alpha (Paschen-α) emission which exceeded that of the Pistol star. [2] Therefore the star was selected for spectroscopy. The survey, which was conducted in 2010, confirmed that the star was a luminous blue variable and the star was designated LBV G0.120-0.048, LBV meaning luminous blue variable and G0.120-0.048 standing for its Galactic coordinates. [2] It was also found through the use of Pα imaging that the star had a large ejection nebula with a diameter over 0.8 pc which was ejected by it 5000-10,000 years ago through large eruptions. [2] The star's spectrum was studied and it was found that the spectrum was similar to the Pistol star so a mass similar to the Pistol star was assumed. [2] The extinction rates were measured and a luminosity of about 4,000,000 L☉ was obtained. [2] It also has the designation MMC2010 from a 2010 survey, MMC standing for the three leading scientists of the survey, Mauerhan, Morris, and Cotera. In 2011, a survey led by Dong, Wang, and Cotera reached for stars in the Galactic centre that emitted Paschen-α. The stars targeted were the ones detected from the HST/NICMOS Paschen-α survey of the Galactic Centre. V4998 Sagittarii was one of the stars observed and it was given another designation of DWC2011 92. [9]

In 2014 a group decided to study the LBVs in the Quintuplet cluster. The mass of the star's nebula was measured at 6.2 M☉. Also measured was the star's effective temperature and it was found to be 12,000 K. [4] The star was designated LBV3 in that survey because it was the third LBV in the Quintuplet cluster. [4]

Characteristics

V4998 Sgr's high mass compresses its core and accelerates fusion primarily by the CNO cycle which leads to a luminosity of about 4,000,000 L☉ and a temperature of 12000 K. It boasts a large ejection nebula with a diameter of about 0.8 parsec (2.5 ly) and a mass of 6.2 M☉. [4] Since comparable nebulae typically last no more than 10,000 years, V4998 Sagittarii is presumed to have undergone a massive eruption 5000-10,000 years ago. [4]

The star is a projected 7 pc (23 ly) away from the Quintuplet starburst cluster, which lies in the direction of the Galactic Center. The cluster contains around 100 O-type stars and several Wolf–Rayet stars. There are also two other luminous blue variables beside V4998 Sagittarii: the Pistol star and qF362. [2]

Evolution

The star's high mass loss rate combined with its eruptions will strip off its hydrogen layers and expose a hot helium core. It will proceed to the Wolf–Rayet sequence. It will eventually start fusing heavy elements in its core, and when it develops a large iron core the star will collapse in on itself and explode as a type Ib or Ic supernovae. Depending on the amount of mass lost before the supernova explosion, the remnant will be a neutron star or black hole. A black hole is predicted for the most massive stars such as this one. [10]

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">Pistol Nebula</span>

The Pistol Nebula is located in the constellation Sagittarius. It surrounds one of the most luminous stars known, the Pistol Star. Both are located 25,000 light years away from Earth in the Quintuplet cluster, near the center of the Milky Way galaxy. The nebula contains approximately 9.3 solar masses worth of ionized gas that was ejected by the star several thousand years ago.

<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 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">LBV 1806−20</span> Likely binary star in the constellation Sagittarius

LBV 1806−20 is a candidate luminous blue variable (LBV) and likely binary star located around 28,000 light-years (8,700 pc) from the Sun, towards the center of the Milky Way. It has an estimated mass of around 36 solar masses and an estimated variable luminosity of around two million times that of the Sun. It is highly luminous but is invisible from the Solar System at visual wavelengths because less than one billionth of its visible light reaches us.

<span class="mw-page-title-main">Arches Cluster</span>

The Arches Cluster is the densest known star cluster in the Milky Way, about 100 light-years from its center in the constellation Sagittarius, 25,000 light-years from Earth. Its discovery was reported by Nagata et al. in 1995, and independently by Cotera et al. in 1996. Due to extremely heavy optical extinction by dust in this region, the cluster is obscured in the visual bands, and is observed in the X-ray, infrared and radio bands. It contains approximately 135 young, very hot stars that are many times larger and more massive than the Sun, plus many thousands of less massive stars.

<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">HD 97950</span> Multiple star system in the constellation Carina

HD 97950, is the central core of a super star cluster within the NGC 3603 H II region. It was catalogued as a single star, but has now been resolved into one of the densest clusterings of stars in the galaxy.

<span class="mw-page-title-main">Quintuplet cluster</span> Dense star cluster of massive young stars in the constellation of Sagittarius

The Quintuplet cluster is a dense cluster of massive young stars about 100 light years from the Galactic Center (GC). Its name comes from the fact it has five prominent infrared sources residing in it. Along with the Arches Cluster it is one of two in the immediate GC region. Due to heavy extinction by dust in the vicinity, it is invisible to optical observation and must be studied in the X-ray, radio, and infrared bands.

<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.

<span class="mw-page-title-main">WR 102ea</span> Star in the constellation Sagittarius

WR 102ea is a Wolf–Rayet star in the Sagittarius constellation. It is the third most luminous star in the Quintuplet cluster after WR 102hb. With a luminosity of 2,500,000 times solar, it is also one of the most luminous stars known. Despite the high luminosity it can only be observed at infra-red wavelengths due to the dimming effect of intervening dust on visual light.

<span class="mw-page-title-main">Wray 17-96</span> Star in Scorpius

Wray 17-96 is a very luminous star in the Scorpius constellation, about 20,000 light-years (7 kpc) away. It is a suspected luminous blue variable (LBV), although it has not shown the characteristic spectral variations.

<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">WR 102c</span>

WR 102c is a Wolf–Rayet star located in the constellation Sagittarius towards the galactic centre. It is only a few parsecs from the Quintuplet Cluster, within the Sickle Nebula.

<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">V4650 Sagittarii</span> Luminous blue variable star in the constellation Sagittarius

V4650 Sagittarii (qF362) is a luminous blue variable star (LBV) in the constellation of Sagittarius. Located some 25,000 light years away, the star is positioned on the edge of a starburst cluster known as the Quintuplet cluster.

WR 111 is a Wolf-Rayet (WR) star in the constellation Sagittarius. It is magnitude 7.8 and lies about 5,150 light-years away. It is one of the brightest and most closely studied WR stars.

<span class="mw-page-title-main">GCIRS 16SW</span> Binary star in the Galactic Center in the constellation Sagittarius

GCIRS 16SW, also known as S97, is a contact binary star located in the Galactic Center. It is composed of two hot massive stars of equal size that orbit each other with a period of 19.5 days. The stars are so close that their atmospheres overlap, and the two stars form an eclipsing binary varying in brightness by 0.35 magnitudes at infrared wavelengths.

References

  1. 1 2 3 4 5 6 7 8 Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  2. 1 2 3 4 5 6 7 8 9 10 11 Mauerhan, J. C.; Morris, M. R.; Cotera, A.; Dong, H.; Wang, Q. D.; et al. (April 2010). "Discovery of a Luminous Blue Variable with an Ejection Nebula Near the Quintuplet Cluster". The Astrophysical Journal. 713 (1): L33–L36. arXiv: 1002.3379 . Bibcode:2010ApJ...713L..33M. doi:10.1088/2041-8205/713/1/L33. S2CID   42696538.
  3. ↑ Clark, J. S.; Lohr, M. E.; Patrick, L. R.; Najarro, F.; Dong, H.; Figer, D. F. (2018). "An updated stellar census of the Quintuplet cluster". Astronomy and Astrophysics. 618: A2. arXiv: 1805.10139 . Bibcode:2018A&A...618A...2C. doi:10.1051/0004-6361/201833041. S2CID   53501337.
  4. 1 2 3 4 5 Lau, R. M.; Herter, T. L.; Morris, M. R.; Adams, J. D. (2014). "Nature Versus Nurture: Luminous Blue Variable Nebulae in and Near Massive Stellar Clusters at the Galactic Center". The Astrophysical Journal. 785 (2): 120. arXiv: 1403.5298 . Bibcode:2014ApJ...785..120L. doi:10.1088/0004-637X/785/2/120. S2CID   118447462.
  5. ↑ Nagata, Tetsuya; Hyland, A. R.; Straw, S. M.; Sato, Shuji; Kawara, Kimiaki (1993). "Bright near-infrared sources within 1 deg of the Galactic center. I - Survey and 1-20 micron photometry". Astrophysical Journal. 406: 501. Bibcode:1993ApJ...406..501N. doi: 10.1086/172462 .
  6. ↑ Glass, I. S.; Matsumoto, S.; Carter, B. S.; Sekiguchi, K. (2001). "Large-amplitude variables near the Galactic Centre". Monthly Notices of the Royal Astronomical Society. 321 (1): 77–95. Bibcode:2001MNRAS.321...77G. doi: 10.1046/j.1365-8711.2001.03971.x .
  7. ↑ Ramírez, Solange V.; Arendt, Richard G.; Sellgren, Kris; Stolovy, Susan R.; Cotera, Angela; Smith, Howard A.; Zadeh, Farhad Yusef (2008). "Point Sources from a Spitzer IRAC Survey of the Galactic Center". The Astrophysical Journal Supplement Series. 175 (1): 147–164. arXiv: 0709.3113 . Bibcode:2008ApJS..175..147R. doi:10.1086/524015. S2CID   17768615.
  8. ↑ Matsunaga, Noriyuki; Kawadu, Takahiro; Nishiyama, Shogo; Nagayama, Takahiro; Hatano, Hirofumi; Tamura, Motohide; Glass, I. S.; Nagata, Tetsuya (2009). "A near-infrared survey of Miras and the distance to the Galactic Centre". Monthly Notices of the Royal Astronomical Society. 399 (4): 1709–1729. arXiv: 0907.2761 . Bibcode:2009MNRAS.399.1709M. doi: 10.1111/j.1365-2966.2009.15393.x . S2CID   13447758.
  9. ↑ Dong, H.; Wang, Q. D.; Morris, M. R. (2011). "A multiwavelength study of evolved massive stars in the Galactic Centre". Monthly Notices of the Royal Astronomical Society. 425 (2): 884–906. arXiv: 1204.6298 . Bibcode:2012MNRAS.425..884D. doi: 10.1111/j.1365-2966.2012.21200.x . S2CID   119217006.
  10. ↑ Ødegaard, K. J. R. (1996). "Evolution of very massive stars". Wolf–Rayet stars in the framework of stellar evolution. Liège International Astrophysical Colloquia. Vol. 33. Liège: Université de Liège. p. 81. Bibcode:1996LIACo..33...81O.

Notes

  1. ↑ Applying the Stefan-Boltzmann Law with a nominal solar effective temperature of 5,772  K:
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