NGC 5281
| NGC 5281 | |
|---|---|
 | |
| Observation data (J2000epoch) | |
| Right ascension | 13h46m35s[1] |
| Declination | −62° 55′ 00″[1] |
| Distance | 4,200ly(1,300pc) |
| Apparent magnitude(V) | 5.9[1] |
| Apparent dimensions (V) | 7' |
| Physical characteristics | |
| Estimated age | 45 million years |
| Other designations | vdBH 152,Collinder276,Melotte120 |
| Associations | |
| Constellation | Centaurus |
NGC 5281is anopen clusterin the constellationCentaurus.It was discovered byNicolas Louis de Lacaillein 1751-1752 fromSouth Africa,and catalogued it as Lacaille I.7.[2][3]NGC5281 is located three and a quarter degrees southwest ofBeta Centauri.Under dark skies, it is bright enough to be spotted withnaked eye,appearing as a 6th magnitude star.[4]
Characteristics[edit]
The four bright stars of the cluster form a striking line as seen from Earth, however the cluster is sparsely populated. The brightest member of the cluster is of mag 6.61. The next two brighter stars have evolved away frommain sequence.Theturn-off massof the cluster is estimated to be at 5.6M☉.Based on the colour magnitude diagram, the age of the cluster is estimated to be 45 myrs.[5]The tidal radius of the cluster is 5.5 - 8.4 parsecs (18 - 27 light years) and represents the average outer limit of NGC 5281, beyond which a star is unlikely to remain gravitationally bound to the cluster core. The radius of the core of the cluster is about 4.3 light years, nearly the same as the distance between theSunand the closest star system,Alpha Centauri.Within the angular radius of the cluster there are 371 probable members.[6]
One of the members of the cluster is HD 119682 (mag. 7.97, spectral type B0.5V), aBe starnotable for itsX-raysemission. It has been categorised by Moffat & Vogt (1973), Mermilliod (1982), and Safi-Harb (2007), as ablue straggler,and it has also been categorised as agamma Cassiopeiaeanalog.[7]HD 119682 has been identified as the visual counterpart of the X-ray source 1WGA J1346.5-6255,[7][8]found within the radio lobes of thesupernova remnantG309.2-00.6, located 4 ± 2 kpc away,[9]with which it is unrelated.[7]Thelight curveof the star in X-rays shows significant brightness variations within hours, however, the spectral distribution appears rather stable. The spectrum obtained by the High Energy Transmission Gratings on boardChandra X-ray Observatoryseems to lack strongemission lines,including Fe Kαfluorescence.[10]
References[edit]
- ^abc "NGC 5281".SIMBAD.Centre de données astronomiques de Strasbourg.Retrieved2015-06-19.
- ^Hartmut Frommert, Christine KronbergNGC 5281seds.org
- ^Jones, K. G. (March 1969). "The search for the nebulae - VI".Journal of the British Astronomical Association.79:213–222.Bibcode:1969JBAA...79..213J.
- ^O'Meara, Stephen James (2013).Deep-Sky Companions: Southern Gems.Cambridge University Press.p. 264.Bibcode:2013dcsg.book.....O.ISBN9781107015012.
- ^Sanner, J.; Brunzendorf, J.; Will, J.-M.; Geffert, M. (15 April 2001). "Photometric and kinematic studies of open star clusters III. NGC4103, NGC5281, and NGC4755".Astronomy & Astrophysics.369(2): 511–526.arXiv:astro-ph/0101541.Bibcode:2001A&A...369..511S.doi:10.1051/0004-6361:20010196.S2CID14693975.
- ^Kharchenko, N. V.; Piskunov, A. E.; Schilbach, E.; Röser, S.; Scholz, R.-D. (3 October 2013)."Global survey of star clusters in the Milky Way".Astronomy & Astrophysics.558:A53.arXiv:1308.5822.Bibcode:2013A&A...558A..53K.doi:10.1051/0004-6361/201322302.S2CID118548517.
- ^abcSafi‐Harb, Samar; Ribo, Marc; Butt, Yousaf; Matheson, Heather; Negueruela, Ignacio; Lu, Fangjun; Jia, Shumei; Chen, Yong (10 April 2007). "A Multiwavelength Study of 1WGA J1346.5−6255: A New γ Cas Analog Unrelated to the Background Supernova Remnant G309.2−00.6".The Astrophysical Journal.659(1): 407–418.arXiv:astro-ph/0607551.Bibcode:2007ApJ...659..407S.doi:10.1086/512055.S2CID15997425.
- ^Rakowski, Cara E.; Schulz, N. S.; Wolk, S. J.; Testa, Paola (1 October 2006). "Extraordinarily Hot X-Ray Emission from the O9 Emission-Line Star HD 119682".The Astrophysical Journal.649(2): L111–L114.arXiv:astro-ph/0608321.Bibcode:2006ApJ...649L.111R.doi:10.1086/508350.S2CID119078231.
- ^Rakowski, Cara E.; Hughes, John P.; Slane, Patrick (10 February 2001). "Two New Ejecta‐dominated Galactic Supernova Remnants: G337.2−0.7 and G309.2−0.6".The Astrophysical Journal.548(1): 258–268.arXiv:astro-ph/0010091.Bibcode:2001ApJ...548..258R.doi:10.1086/318680.S2CID18235541.
- ^Torrejón, J. M.; Schulz, N. S.; Nowak, M. A.; Testa, P.; Rodes, J. J. (11 February 2013). "HOT THERMAL X-RAY EMISSION FROM THE Be STAR HD 119682".The Astrophysical Journal.765(1): 13.arXiv:1301.2913.Bibcode:2013ApJ...765...13T.doi:10.1088/0004-637X/765/1/13.S2CID53699324.
External links[edit]
- NGC 5281 onWikiSky:DSS2,SDSS,GALEX,IRAS,Hydrogen α,X-Ray,Astrophoto,Sky Map,Articles and images
