Astronomy:HD 118285

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Short description: SPB star in the constellation Chamaeleon.
HD 118285
DYChaLightCurve.png
A light curve for DY Chamaeleontis, plotted from TESS data[1]
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Chamaeleon
Right ascension  13h 39m 11.99015s[2]
Declination −75° 41′ 01.6128″[2]
Apparent magnitude (V) 6.32[3] (6.34 - 6.38)[4]
Characteristics
Evolutionary stage main sequence star[5]
Spectral type B8 IV[6]
U−B color index −0.26[7]
B−V color index +0.01[7]
Variable type SPB[4]
Astrometry
Radial velocity (Rv)18.2±2.3[8] km/s
Proper motion (μ) RA: −20.690[2] mas/yr
Dec.: −14.712[2] mas/yr
Parallax (π)3.7743 ± 0.0289[2] mas
Distance864 ± 7 ly
(265 ± 2 pc)
Absolute magnitude (MV)−0.54[9]
Details
Mass3.63±0.12[5] M☉
Radius5.52±0.28[10] R☉
Luminosity293+50−42[5] L☉
Temperature11,350+79−78[5] K
Metallicity [Fe/H]0.00[11] dex
Rotational velocity (v sin i)67[12] km/s
Age309[13] Myr
Other designations
DY Cha, CD−75°632, CPD−75°882, FK5 503, GC 18406, HD 118285, HIP 66607, HR 5115, SAO 257069[14]
Database references
SIMBADdata

HD 118285, also known as HR 5115, is a variable star located in the southern circumpolar constellation Chamaeleon. DY Chamaeleontis (DY Cha) is its variable star designation. It has an average apparent magnitude of 6.32,[3] placing it near the limit for naked eye visibility. The object is located relatively far at a distance of 864 light years based on Gaia DR3 parallax measurements but is receding with a heliocentric radial velocity of 18 km/s.[8] At its current distance, HD 118285's brightness is diminished by 0.58 magnitudes due to interstellar dust.[15]

HD 118285's variability was first observed in a 1998 Hipparcos survey focusing on the discovery of slowly pulsating B-type stars (SPB).[16] It was later confirmed to be an SPB star and given the variable designation DY Chamaeleontis.[17] It fluctuates between magnitudes 6.34 and 6.38 in the visual passband with a period of 23 hours.[4]

This is a slightly evolved B-type star with a stellar classification of B8 IV.[6] Contrary to the classification, stellar evolution models from Zorec and Royer (2012) model it as a dwarf star that has completed 89.1% of its main sequence life.[5] It has 3.6 times the mass of the Sun[5] and 5.5 times its girth.[10] It radiates 293 times the luminosity of the Sun from its photosphere at an effective temperature of 11,350 K,[5] giving it a bluish-white hue. It is estimated to be 309 million years old[13] and spins modestly with a projected rotational velocity of 67 km/s.[12]

References

  1. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 
  2. ↑ 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H. 
  4. ↑ 4.0 4.1 4.2 Samus’, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (January 2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports 61 (1): 80–88. doi:10.1134/S1063772917010085. ISSN 1063-7729. Bibcode: 2017ARep...61...80S. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Zorec, J.; Royer, F. (January 2012). "Rotational velocities of A-type stars IV: Evolution of rotational velocities". Astronomy & Astrophysics 537: A120. doi:10.1051/0004-6361/201117691. ISSN 0004-6361. Bibcode: 2012A&A...537A.120Z. 
  6. ↑ 6.0 6.1 Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations −90° to −53°. Bibcode: 1975mcts.book.....H. 
  7. ↑ 7.0 7.1 Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory 4: 99–110. Bibcode: 1966CoLPL...4...99J. 
  8. ↑ 8.0 8.1 Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759–771. doi:10.1134/S1063773706110065. ISSN 1063-7737. Bibcode: 2006AstL...32..759G. 
  9. ↑ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A. 
  10. ↑ 10.0 10.1 Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants". Astronomy & Astrophysics 426 (1): 297–307. doi:10.1051/0004-6361:20035930. ISSN 0004-6361. Bibcode: 2004A&A...426..297K. 
  11. ↑ Gontcharov, G. A. (December 2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters 38 (12): 771–782. doi:10.1134/S1063773712120031. ISSN 1063-7737. Bibcode: 2012AstL...38..771G. 
  12. ↑ 12.0 12.1 Levato, H.; Grosso, M. (June 2004). "New Projected Rotational Velocities of All Southern B-type Stars of the Bright Star Catalogue". Astronomical Society of the Pacific 215: 51. Bibcode: 2004IAUS..215...51L. 
  13. ↑ 13.0 13.1 Gontcharov, G. A. (November 2012). "Spatial distribution and kinematics of OB stars". Astronomy Letters 38 (11): 694–706. doi:10.1134/S1063773712110035. ISSN 1063-7737. Bibcode: 2012AstL...38..694G. 
  14. ↑ "DY Cha". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=DY+Cha. 
  15. ↑ Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society 472 (4): 3805–3820. doi:10.1093/mnras/stx2219. ISSN 0035-8711. Bibcode: 2017MNRAS.472.3805G. 
  16. ↑ Waelkens, C.; Aerts, C.; Kestens, E.; Grenon, M.; Eyer, L. (February 1998). "Study of an unbiased sample of B stars observed with Hipparcos: the discovery of a large amount of new slowly pulsating B stars". Astronomy and Astrophysics 330: 215–221. ISSN 0004-6361. Bibcode: 1998A&A...330..215W. 
  17. ↑ Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V.; Frolov, M. S.; Antipin, S. V.; Kireeva, N. N.; Pastukhova, E. N. (January 1999). "The 74th Special Name-list of Variable Stars". Information Bulletin on Variable Stars 4659: 1. ISSN 0374-0676. Bibcode: 1999IBVS.4659....1K. 
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