RSGC1

RSGC1 (Red Supergiant Cluster 1) 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.[3] 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.[4]

RSGC1
Spitzer image of RSGC1
Observation data (J2000 epoch)
Right ascension18h 36m 29s[1]
Declination−06° 52′ 48″[1]
Distance22.0 ± 2.9kly (6.60 ± 0.89kpc[2])
Apparent magnitude (V)not visible[2]
Apparent dimensions (V)~1.5′[3][1]
Physical characteristics
Mass~3 × 104[2] M☉
Radius1.5 ± 0.3 pc[2]
Estimated age12 ± 2 my[2][1]
Associations
ConstellationScutum

The age of RSGC1 is estimated at 10–14 million years. The cluster is heavily obscured and has not been detected in visible light. It lies close to other groupings of red supergiants known as Stephenson 2, RSGC3, Alicante 7, Alicante 8, and Alicante 10. The mass of RSGC1 is estimated at 30 thousand solar masses, which makes it one of the most massive open clusters in the Galaxy.[2]

The observed red supergiants with the mass of about 16–20 solar masses are type II supernova progenitors.[2] Over 200 main sequence stars have been detected with masses over 8 M☉, which allows the distance to be determined from main sequence fitting. Fourteen red supergiant members have been identified.[1]

Members
Prominent supergiants[2][5]
Star Spectral type Magnitude (K band) Temperature (effective, K) Absolute magnitude Luminosity (L☉) Radius (R☉)
F01M3 / M5[6]4.9623,550[6]−11.75335,000[6] 1,530[6]
F02M4 / M2[6]5.0293,700[6]−11.92215,000[6] 1,128[6]
F03M4 / M5[6]5.3333,500[6]−11.28120,000[6] 942[6]
F04M0 / M1[6]5.3423,800[6]−11.24380,000[6] 1,422[6]
F05M6 / M4[6]5.5353,500[6]−11.36190,000[6] 1,185[6]
F06M5[6]5.6133,400[6]−10.70230,000[6] 1,382[6]
F07M2 / M3[6]5.6313,600[5] - 3,800[6]−10.81190,000[6] 1,006[6]
F08M3[6]5.6543,600[6]−11.33200,000[6] 1,150[6]
F09M3 / M6[6]5.6703,600[6]−10.92150,000[6] 996[6]
F10M5 / M3[6]5.7093,600[6]−10.86235,000[6] 1,246[6]
F11M1 / M4[6]5.7223,800[6]−11.03200,000[6] 1,032[6]
F12[3]M0[6]5.8643,900[6] −10.70190,000[6] 955[6]
F13M3 / K2[6]5.9574,200[6]−11.39290,000[6] 1,017[6]
F14M3 / M1[6]6.1673,700[6]−10.2574,000[6][2] 662[6]
F15G0 / G6[6]6.6826,850[2]−10.07229,000[2] - 620,000[6] 340[2]

RSGC1-F13

RSGC1-F13 is a peculiar red supergiant which is unusually red compared to the other stars.[7] It is notable for having the highest mass-loss rate in the cluster at (2.7±0.8)×10−5 M☉/yr.[6] The star also has detected masers of SiO, H2O, and OH.[6] ALMA detects CO emission in F13 along with four other supergiants in the cluster extending hundreds of stellar radii away from the stars.[7] The CO mass loss rate is estimated to be 4.2×10−5 M☉/yr, which is an order of magnitude larger than the predicted value for the other red supergiants in the study.[7] F13 is compared with VY Canis Majoris as a similarly extreme red supergiant, both displaying stronger and possibly eruptive mass-loss.[7]

References
  1. Froebrich, D.; Scholz, A. (2013). "The main sequence of three red supergiant clusters". Monthly Notices of the Royal Astronomical Society. 436 (2): 1116–1122. arXiv:1308.6436. Bibcode:2013MNRAS.436.1116F. doi:10.1093/mnras/stt1633. ISSN 0035-8711. S2CID 31935943.
  2. Davies, B.; Figer, D. F.; Law, C. J.; Kudritzki, R. P.; Najarro, F.; Herrero, A.; MacKenty, J. W. (2008). "The Cool Supergiant Population of the Massive Young Star Cluster RSGC1". The Astrophysical Journal. 676 (2): 1016–1028. arXiv:0711.4757. Bibcode:2008ApJ...676.1016D. doi:10.1086/527350. S2CID 15639297.
  3. Figer, D. F.; MacKenty, J. W.; Robberto, M.; Smith, K.; Najarro, F.; Kudritzki, R. P.; Herrero, A. (2006). "Discovery of an Extraordinarily Massive Cluster of Red Supergiants". The Astrophysical Journal. 643 (2): 1166–1179. arXiv:astro-ph/0602146. Bibcode:2006ApJ...643.1166F. doi:10.1086/503275. S2CID 18241900.
  4. 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.
  5. Fok, Thomas K. T.; Nakashima, Jun-ichi; Yung, Bosco H. K.; Hsia, Chih-Hao; Deguchi, Shuji (2012-11-20). "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. hdl:10722/181706. ISSN 0004-637X. S2CID 53393926.
  6. Humphreys, Roberta M.; Helmel, Greta; Jones, Terry J.; Gordon, Michael S. (August 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.
  7. Decin, Leen; Richards, Anita M. S.; Marchant, Pablo; Sana, Hugues (17 March 2023). "ALMA detection of CO rotational line emission in red supergiant stars of the massive young star cluster RSGC1 -- Determination of a new mass-loss rate prescription for red supergiants". arXiv:2303.09385 [astro-ph.SR].
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