RX Telescopii

RX Telescopii is an irregular variable star in the constellation Telescopium. It has a maximum magnitude of 6.45 and a minimum magnitude 7.47. It is a red supergiant with a spectral type of M3Iab, indicating the star is an intermediate-size luminous supergiant star.[2]

RX Telescopii
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Telescopium
Right ascension 19h 06m 58.206s[1]
Declination −45° 58′ 13.54″[1]
Apparent magnitude (V) 6.45 - 7.47[2]
Characteristics
Evolutionary stage Red supergiant
Spectral type M3Iab[2]
Variable type LC[3]
Astrometry
Proper motion (μ) RA: 2.285[4] mas/yr
Dec.: -6.520[4] mas/yr
Parallax (π)0.4914 ± 0.0810[4] mas
Distanceapprox. 7,000 ly
(approx. 2,000 pc)
Details
Temperature3,200[5] K
Other designations
CD−46°12809, HD 177456, SAO 229497[6]
Database references
SIMBADdata

The distance to RX Telescopii is uncertain. It has a Gaia Data Release 2 parallax of 0.1699±0.0790 mas,[1] suggesting a distance around 6,000 parsecs.[1] A more rigorous statistical calculation gives a distance of 4,726+2,371
−1,315 pc,[7] suggesting a radius of 1,897 R☉ using an angular diameter of 3.734 mas, which would make it one of the largest stars discovered and its photosphere engulf the orbit of Jupiter, and nearing that of Saturn if it was placed in our solar system.[8] However the Gaia database has an astrometric noise value larger than the parallax itself and about ten times larger than the typical maximum for a reliable parallax, thus this distance, hence the radius, are inaccurate.[1] Gaia EDR3 published a parallax of 0.4914±0.0810 mas, corresponding to a much smaller radius of 817 R☉ using the angular diameter.[4]

References
  1. 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.
  2. BSJ (11 November 2011). "RX Telescopii". AAVSO Website. American Association of Variable Star Observers. Retrieved 26 June 2014.
  3. 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: B/gcvs. Bibcode:2009yCat....102025S.
  4. Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
  5. Wright, Candace O.; Egan, Michael P.; Kraemer, Kathleen E.; Price, Stephan D. (2003). "The Tycho-2 Spectral Type Catalog". The Astronomical Journal. 125 (1): 359. Bibcode:2003AJ....125..359W. doi:10.1086/345511.
  6. "V* RX Tel". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 26 June 2020.
  7. Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Mantelet, G.; Andrae, R. (2018). "Estimating Distance from Parallaxes. IV. Distances to 1.33 Billion Stars in Gaia Data Release 2". The Astronomical Journal. 156 (2): 58. arXiv:1804.10121. Bibcode:2018AJ....156...58B. doi:10.3847/1538-3881/aacb21. S2CID 119289017.
  8. Cruzalèbes, P.; Petrov, R. G.; Robbe-Dubois, S.; Varga, J.; Burtscher, L.; Allouche, F.; Berio, P.; Hofmann, K. H.; Hron, J.; Jaffe, W.; Lagarde, S.; Lopez, B.; Matter, A.; Meilland, A.; Meisenheimer, K.; Millour, F.; Schertl, D. (2019). "A catalogue of stellar diameters and fluxes for mid-infrared interferometry". Monthly Notices of the Royal Astronomical Society. 490 (3): 3158–3176. arXiv:1910.00542. Bibcode:2019MNRAS.490.3158C. doi:10.1093/mnras/stz2803. S2CID 203610229.


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