Stephenson 2 DFK 49

Last updated
Stephenson 2 DFK 49
Observation data
Epoch J2000       Equinox J2000
Constellation Scutum
Right ascension 18h 39m 05.586s [1]
Declination −06° 04′ 26.58″ [1]
Characteristics
Evolutionary stage Red supergiant [2] or post red supergiant [3]
Spectral type K4 [2]
Apparent magnitude  (K)7.324 [1]
Astrometry
Radial velocity (Rv)101 [4] -109.4 [2]  km/s
Details
Radius 1,074 [2]  –1,300 [3]   R☉
Luminosity 245,000 [2]  –390,000 [3]   L☉
Temperature 3920±112 [2]  –4,000 [3]   K
Other designations
Stephenson 2 DFK 49, St2-11, [5] DENIS J183905.5-060425 2MASS J18390558-0604265, MSX6C G026.1215-00.0345 TIC 7759844
Database references
SIMBAD data

Stephenson 2 DFK 49 or St2-11 is a putative post red supergiant [3] star in the constellation Scutum, in the massive open cluster Stephenson 2. It is possibly one of the largest known stars with a radius estimated to be between 1,074 solar radii (747,000,000 kilometres ; 4.99 astronomical units ) [2] to 1,300 solar radii (900,000,000 kilometres; 6.0 astronomical units), [3] . If it was placed at the center of the Solar System, its photosphere would potentially approach or engulf Jupiter's orbit. It loses mass at a very high rate, resulting in large amounts of infrared excess.

Contents

Observation history

The open cluster Stephenson 2 was discovered by American astronomer Charles Bruce Stephenson in 1990 in the data obtained by a deep infrared survey. [2] [6] The cluster is also known as RSGC2, one of several massive open clusters in Scutum, each containing multiple red supergiants. [7] The 49th brightest star in the K band was given an identifier number of 49. [2] The authors noted that the star likely had significant circumstellar and interstellar extinction, higher than even the other cluster members, and noted that its spectral type places it near yellow hypergiants on the Hertzsprung–Russell diagram (HR Diagram), though not as hot. [2]

An image of Stephenson 2 DFK 1, the brightest star at the centre of the image. Stephenson 2 DFK 49 is the very red and dim star to the upper-left of St2 DFK 1 Stephenson 2-18 zoomed in, 2MASS survey, 2003.png
An image of Stephenson 2 DFK 1, the brightest star at the centre of the image. Stephenson 2 DFK 49 is the very red and dim star to the upper-left of St2 DFK 1

In a later study from 2010, the same star was given the identifier number 11, and was grouped with a proposed cluster assumed to be associated with Stephenson 2, Stephenson 2-SW. The star showed maser emissions at some spectral lines. A later study corroborates this. [4] The study mentions a weak CO emission with radial velocities similar to Stephenson 2 DFK 49, but it is said to be unrelated due to being too intense for a red supergiant at Stephenson 2 DFK 49’s distance. [5] Another study observed and studied 57 red supergiant stars across the galaxy and gave estimates of the stars' properties based on their Spectral Energy Distributions, like luminosity and temperature. In 2016, it was compared to the yellow hypergiant star IRAS 18357-0604, which can be found in the same general region as Stephenson 2. [8]

A recent study on red supergiant mass loss rates and histories notes it as the most interesting object in the cluster, because its spectral energy distribution, which has a significant infrared excess, is similar to that of the famous and extreme red hypergiant VY Canis Majoris. However, Stephenson 2 DFK 49 is hotter. The study also estimates the possible mass loss rates of the star, as well as its other properties. [3]

Properties

Stephenson 2 DFK 49 was known to be an interesting object since its home cluster was first studied in depth. [2] An interesting note about Stephenson 2 DFK 49 is that it appears to be at the center of a bow-shock structure in infrared images. Because of its properties and likely position on the H-R diagram, the authors of Davies 2007 stated that both it and Stephenson 2 DFK 1 warranted further studies, especially in terms of stellar evolution. [2] Its properties, an earlier than usual spectral type compared to other stars in Stephenson 2, its luminosity and position on the HR Diagram indicate that it is similar to the extreme yellow hypergiant star IRC+10420 and Variable A in the Triangulum Galaxy (M33). [3] Stephenson 2 DFK 49 is comparable to another extreme star in the vicinity of Stephenson 2, IRAS 18357-0604. Both are possible post-red supergiant stars, [8] and both of them are comparable to the yellow hypergiant IRC+10420.

Spitzer image centred on Stephenson 2-SW, with the main cluster towards upper left. The bow-shock feature centered on St2 DFK 49 (seen as a bright yellowish arc) is readily apparent. Stephenson 2-18 and its surroundings.png
Spitzer image centred on Stephenson 2-SW, with the main cluster towards upper left. The bow-shock feature centered on St2 DFK 49 (seen as a bright yellowish arc) is readily apparent.

Luminosity

In 2007, a study of the red supergiants in Stephenson 2 estimated its properties and determined a bolometric luminosity of 245,000 L☉. [2] A 2012 study estimated and published the properties of numerous red supergiants and other supergiant stars. The study estimated Stephenson 2-11's luminosity at a much lower 132,000 L☉, using spectral energy distribution (SED). [9] Using the SED, Humphreys (2020) estimates a luminosity of 390,000 L☉. However, it is noted that the estimated luminosity may be an underestimate, because it does not include excess radiation from warm dust. [3]

Temperature and Spectrum

Davies (2007) estimated its temperature of 3,920  K , but with an uncertainty in the measurement of ± 112 K. [2] 5 years later, Fok (2012) estimated a slightly cooler temperature at 3,700  K . [9] A more recent study estimated the star's temperature at a hotter 4,000  K , based on its spectral type of K4. [3]

Size

Davies (2007) estimates a temperature of 3,920  K , with a luminosity of 245,000 L☉. Applying the Stefan-Boltzmann law, Stephenson 2 DFK 49’s radius would be 1,074 solar radii (747,000,000 kilometres ; 4.99 astronomical units ), making it one of the largest stars known. [2] A 2012 study published the estimated properties of numerous red supergiants and other supergiant stars using Spectral Energy Distributions, including Stephenson 2 DFK 49. The study estimates its temperature at a slightly cooler 3,700  K but its luminosity at a much lower 132,000 L☉. [9] This would imply a radius of only 884 solar radii (615,000,000 kilometres ; 4.11 astronomical units ), smaller than the radius implied by Davies (2007). Humphreys (2020) estimates Stephenson 2 DFK 49's temperature at 4,000  K , but a higher luminosity of 390,000 L☉. Applying the Stefan-Boltzmann law, its radius would be 1,300 solar radii (900,000,000 kilometres ; 6.0 astronomical units ), larger than the other two estimates. [3]

Mass loss and maser emissions

While Davies (2007) does not estimate a mass loss rate for Stephenson 2 DFK 49, the study mentions that it would be interesting to estimate its mass loss rate. In 2012, it was noted for having maser emissions at certain spectral lines. [4] A 2020 study later determines a mass loss rate of 1.3-7*10−4 per year based on several computer models, but it is noted that these rates are not high for other hypergiant stars such as VY Canis Majoris, NML Cygni and IRC+10420. As a possible post-red supergiant star, Stephenson 2 DFK 49 likely experiences both constant and variable mass-loss rates. [3]

Evolution and future

A star with the properties of Stephenson 2 DFK 49 would imply an initial mass of more than 25 M☉. [3]

Because Stephenson 2 DFK 49 has lost so much mass and continues to do so, and its likely status as a post-red supergiant star, it is likely on the verge of shedding all of its outer layers and becoming a luminous blue variable or a Wolf-Rayet star. [2]

Related Research Articles

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

Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars spans from about 3,400 K to over 20,000 K.

<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">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">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">MY Cephei</span> Red supergiant star in the constellation Cepheus

MY Cephei is a red supergiant located in open cluster NGC 7419 in the constellation of Cepheus. It is a semiregular variable star with a maximum brightness of magnitude 14.4 and a minimum of magnitude 15.5.

<span class="mw-page-title-main">S Persei</span> Red supergiant or hypergiant variable star in the constellation Perseus

S Persei is a red supergiant or hypergiant located near the Double Cluster in Perseus, north of the cluster NGC 869. It is a member of the Perseus OB1 association and one of the largest known stars. If placed in the Solar System, its photosphere would engulf the orbit of Jupiter. It is also a semiregular variable, a star whose variations are less regular than those of Mira variables.

<span class="mw-page-title-main">RW Cephei</span> Hypergiant star in the constellation Cepheus

RW Cephei is a K-type hypergiant and a semirregular variable star in the constellation Cepheus, at the edge of the Sharpless 132 H II region and close to the small open cluster Berkeley 94. It is among the largest stars known with a radius of 1,100 times that of the Sun (R☉), nearly as large as the orbit of Jupiter.

<span class="mw-page-title-main">WOH G64</span> Red supergiant in the constellation Dorado

WOH G64 is an unusual red supergiant (RSG) star in the Large Magellanic Cloud (LMC) satellite galaxy in the southern constellation of Dorado. It is the largest known star with a well-defined radius. It is also one of the most luminous and massive red supergiants, with a radius calculated to be around 1,540 times that of the Sun (R☉) and a luminosity around 282,000 times the solar luminosity (L☉).

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

VY Canis Majoris is an extreme oxygen-rich red hypergiant or red supergiant 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. 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">Stephenson 2</span> Massive open cluster in the constellation Scutum

Stephenson 2, also known as RSGC2, is a young massive open cluster belonging to the Milky Way galaxy. It was discovered in 1990 as a cluster of red supergiants in a photographic, deep infrared survey by the astronomer Charles Bruce Stephenson, after whom the cluster is named. It is located in the constellation Scutum at the distance of about 6 kpc from the Sun. It is likely situated at the intersection of the northern end of the Long Bar of the Milky Way and the inner portion of the Scutum–Centaurus Arm—one of the two major spiral arms.

<span class="mw-page-title-main">RSGC1</span> Massive open cluster with many red supergiants in the constellation Scutum

RSGC1 is a young massive open cluster in the Milky Way galaxy. It was discovered in 2006 in the data generated by several infrared surveys, named for the unprecedented number of red supergiant members. The cluster is located in the constellation Scutum at the distance of about 6.6 kpc from the Sun. It is likely situated at the intersection of the northern end of the Long Bar of the Milky Way and the inner portion of the Scutum–Centaurus Arm—one of its two major spiral arms.

<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">Westerlund 1 W26</span> Star in the constellation Ara

Westerlund 1 W26 or Westerlund 1 BKS AS is a red supergiant located at the outskirts of the Westerlund 1 super star cluster. It is one of the largest known stars and the most luminous supergiant stars discovered so far with radius calculated to be in excess of a thousand times the solar radius, and a luminosity of over 200,000 times the solar luminosity. If placed at the center of the Solar System, its photosphere would engulf the orbit of Jupiter.

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

HR 5171, also known as V766 Centauri, is a yellow hypergiant in the constellation Centaurus. It is said to be either an extreme red supergiant (RSG) or recent post-red supergiant (Post-RSG) yellow hypergiant (YHG), both of which suggest it is one of the largest known stars. The star's diameter is uncertain but likely to be between 1,100 and 1,600 times that of the Sun. It is 3.6 kpc from Earth.

<span class="mw-page-title-main">HD 143183</span> Star in the constellation Norma

HD 143183 is a red supergiant variable star of spectral type M3Ia in constellation Norma. It is a member of the Norma OB1 association, at a distance of about 2 kiloparsecs. It is one of the most luminous red supergiants with a luminosity over 250,000 times greater than the Sun (L☉), and is as well one of the largest stars with a radius more than a thousand times that of the Sun (R☉). Older studies frequently calculated higher luminosities and radii. It has an estimated mass loss rate of 5×10−5 M☉ per year and has been once described as a cool hypergiant. It is surrounded by a dozen early-type stars and a circumstellar nebula which extends 0.12 parsecs (0.39 ly).

<span class="mw-page-title-main">Stephenson 2 DFK 1</span> Star in the open cluster Stephenson 2

Stephenson 2 DFK 1, also known as RSGC2-01 or St2-18, is a red supergiant (RSG) or possible extreme red hypergiant (RHG) star in the constellation of Scutum. It lies near the open cluster Stephenson 2, which is located about 5.8 kiloparsecs away from Earth in the Scutum–Centaurus Arm of the Milky Way galaxy, and is assumed to be one of a group of stars at a similar distance, although some studies consider it to be an unrelated or foreground red supergiant.

<span class="mw-page-title-main">IRAS 18357–0604</span> Star in the constellation Scutum

IRAS 18357–0604 is a yellow hypergiant (YHG) star located in the constellation of Scutum, estimated to be about 19,600 light years, or 6,000 parsecs, away. IRAS 18357–0604 is remarkably similar to IRC +10420, another yellow hypergiant in the constellation of Aquila.

<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. 1 2 3 Cutri, Roc M.; et al. (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 12 13 14 15 16 Davies, B.; Figer, D. F.; Kudritzki, R. P.; MacKenty, J.; Najarro, F.; Herrero, A. (2007). "A Massive Cluster of Red Supergiants at the Base of the Scutum-Crux Arm". The Astrophysical Journal . 671 (1): 781–801. arXiv: 0708.0821 . Bibcode:2007ApJ...671..781D. doi:10.1086/522224. S2CID   1447781.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 Humphreys, Roberta M.; Helmel, Greta; Jones, Terry J.; Gordon, Michael S. (2020). "Exploring the Mass Loss Histories of the Red Supergiants". The Astronomical Journal . 160 (3): 145. arXiv: 2008.01108 . Bibcode:2020AJ....160..145H. doi: 10.3847/1538-3881/abab15 . S2CID   220961677.
  4. 1 2 3 Verheyen, L.; Messineo, M.; Menten, K.M. (March 2012). "SiO maser emission from red supergiants across the Galaxy". Astronomy and Astrophysics. 541: A36. arXiv: 1203.4727 . Bibcode:2012A&A...541A..36V. doi:10.1051/0004-6361/201118265. S2CID   55630819.
  5. 1 2 Deguchi, Shuji; Nakashima, Jun-Ichi; Zhang, Yong; Chong, Selina S. N.; Koike, Kazutaka; Kwok, Sun (2010). "SiO and H2O Maser Observations of Red Supergiants in Star Clusters Embedded in the Galactic Disk". Publications of the Astronomical Society of Japan . 62 (2): 391–407. arXiv: 1002.2492 . Bibcode:2010PASJ...62..391D. doi:10.1093/pasj/62.2.391. S2CID   24396370.
  6. ↑ Stephenson, C. B. (1990). "A possible new and very remote galactic cluster". The Astronomical Journal . 99: 1867. Bibcode:1990AJ.....99.1867S. doi:10.1086/115464.
  7. ↑ Negueruela, I.; González-Fernández, C.; Marco, A.; Clark, J. S.; Martínez-Núñez, S. (2010). "Another cluster of red supergiants close to RSGC1". Astronomy and Astrophysics. 513: A74. arXiv: 1002.1823 . Bibcode:2010A&A...513A..74N. doi:10.1051/0004-6361/200913373. S2CID   118531372.
  8. 1 2 Clark, J. S.; Negueruela, I.; González-Fernández, C. (2014-01-01). "IRAS 18357-0604 – An analogue of the galactic yellow hypergiant IRC +10420?". Astronomy and Astrophysics. 561: A15. arXiv: 1311.3956 . Bibcode:2014A&A...561A..15C. doi:10.1051/0004-6361/201322772. ISSN   0004-6361. S2CID   53372226.
  9. 1 2 3 Fok, Thomas K. T; Nakashima, Jun-ichi; Yung, Bosco H. K; Hsia, Chih-Hao; Deguchi, Shuji (2012). "Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters". The Astrophysical Journal . 760 (1): 65. arXiv: 1209.6427 . Bibcode:2012ApJ...760...65F. doi:10.1088/0004-637X/760/1/65. S2CID   53393926.
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