HD 137509
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Apus |
| Right ascension | 15h 31m 27.11494s[2] |
| Declination | −71° 03′ 43.6643″[2] |
| Apparent magnitude (V) | 6.89[3] |
| Characteristics | |
| Spectral type | B9p (SiCrFe)[4] B8 He wk SiCrFe[5] |
| B−V color index | −0.125±0.004[3] |
| Variable type | α2 CVn[6] |
| Astrometry | |
| Radial velocity (Rv) | +0.50[7] km/s |
| Proper motion (μ) | RA: −16.276[2] mas/yr Dec.: −15.503[2] mas/yr |
| Parallax (π) | 5.0410 ± 0.0503 mas[2] |
| Distance | 647 ± 6 ly (198 ± 2 pc) |
| Absolute magnitude (MV) | 0.45[3] |
| Details | |
| Mass | 3.43±0.17[8] M☉ |
| Radius | 2.81[9] R☉ |
| Luminosity | 123[3] L☉ |
| Surface gravity (log g) | 4.3[5] cgs |
| Temperature | 13,100±500[5] K |
| Rotation | 4.492 d[8] |
| Rotational velocity (v sin i) | 20±2[5] km/s |
| Age | 124[10] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 137509 is a star in the southern constellation of Apus, positioned less than a degree from the northern constellation boundary with Triangulum Australe.[12] It has the variable star designation of NN Apodis, or NN Aps for short, and ranges in brightness from an apparent visual magnitude of 6.86 down to 6.93 with a period of 4.4916 days.[6] The star is located at a distance of approximately 647 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +0.50 km/s.[7]
In 1973, W. P. Bidelman and D. J. MacConnell found this to be a peculiar A star of the silicon type.[13] During a reclassification of the spectra of southern stars in 1975, A. P. Cowley and N. Houk noted the strength of hydrogen lines and weakness of helium are more typical of a class near B9. It shows a luminosity above the main sequence, which is common for a peculiar A star. The stellar atmosphere appears deficient in helium, but shows a rich variety of metallic lines. However, there are no lines of manganese or mercury, so it's not a Hg–Mn Ap star.[14] HD 137509 is now classified as B9p (SiCrFe)[4] or B8 He wk SiCrFe,[5] matching a late-type, helium-weak Bp star with overabundances of silicon, chromium, and iron.
This star was found to be photometrically variable by L. O. Lodén and A. Sundman in 1989, and a variable spectrum was noted by H. Pedersen in 1979.[13] It has one of the strongest magnetic fields recorded for a chemically peculiar star, measured at around 29 kG,[4] and shows a strong quadrupolar component.[15] Both variances of the star allow its rotation period to be precisely measured.[13] It is classified as a Alpha2 Canum Venaticorum variable.[6] The star is about 124[10] million years old with 3.4[8] times the mass of the Sun and 2.8[9] times the Sun's radius. On average it is radiating ~123[3] times the luminosity of the Sun from its photosphere at an effective temperature of 13,100 K.[5]
References
[edit]- ^ Lanz, T.; Mathys, G. (August 1991). "The Photometric Variability of the B9p Star HD 137509". Information Bulletin on Variable Stars. 3655: 1. Bibcode:1991IBVS.3655....1L.
- ^ a b c d e 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.
- ^ a b c d e Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
- ^ a b c Shulyak, D.; et al. (2008). "Model atmospheres of magnetic chemically peculiar stars. A remarkable strong-field Bp SiCrFe star HD 137509". Astronomy and Astrophysics. 487 (2): 689–96. arXiv:0806.1296. Bibcode:2008A&A...487..689S. doi:10.1051/0004-6361:20079134. S2CID 14113957.
- ^ a b c d e f Bailey, J. D.; Landstreet, J. D. (2013). "Abundances determined using Si ii and Si iii in B-type stars: Evidence for stratification". Astronomy & Astrophysics. 551: A30. arXiv:1301.3050. Bibcode:2013A&A...551A..30B. doi:10.1051/0004-6361/201220671. S2CID 59291051.
- ^ a b c Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
- ^ a b Barbier-Brossat, M.; Petit, M.; Figon, P. (December 1994). "Third bibliographic catalogue of stellar radial velocities". Astronomy and Astrophysics Supplement. 108: 603–609. Bibcode:1994A&AS..108..603B.
- ^ a b c Netopil, Martin; et al. (July 2017). "An investigation of the rotational properties of magnetic chemically peculiar stars". Monthly Notices of the Royal Astronomical Society. 468 (3): 2745–2756. arXiv:1703.05218. Bibcode:2017MNRAS.468.2745N. doi:10.1093/mnras/stx674.
- ^ a b Shulyak, D.; et al. (2014). "Interferometry of chemically peculiar stars: Theoretical predictions versus modern observing facilities". Monthly Notices of the Royal Astronomical Society. 443 (2): 1629. arXiv:1406.6093. Bibcode:2014MNRAS.443.1629S. doi:10.1093/mnras/stu1259. S2CID 96452769.
- ^ a b Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694–706, arXiv:1606.09028, Bibcode:2012AstL...38..694G, doi:10.1134/S1063773712110035, S2CID 119108982
- ^ "9 Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-12-27.
- ^ Sinnott, Roger W.; Perryman, Michael A. C. (1997). Millennium Star Atlas. Vol. 2. Sky Publishing Corporation and the European Space Agency. p. 1009. ISBN 0-933346-83-2.
- ^ a b c Mathys, G.; Lanz, T. (July 1997). "The variations of the BP star HD 137509". Astronomy and Astrophysics. 323: 881–885. Bibcode:1997A&A...323..881M.
- ^ Cowley, A. P.; Houk, N. (August 1975). "An interesting new southern peculiar A star - HD 137509". Publications of the Astronomical Society of the Pacific. 87: 527–528. Bibcode:1975PASP...87..527C. doi:10.1086/129803.
- ^ Kochukhov, O. (July 2006). "Remarkable non-dipolar magnetic field of the Bp star HD 137509". Astronomy and Astrophysics. 454 (1): 321–325. arXiv:astro-ph/0603831. Bibcode:2006A&A...454..321K. doi:10.1051/0004-6361:20064932. S2CID 17058487.
