NGC 2539
{{short description|Open cluster in the constellation Puppis}}
{{Infobox cluster
| name = NGC 2539
| image = File:NGC 2539.png
| caption = NGC 2539
| credit =
| type = Open Cluster
| epoch = J2000
| constellation = Puppis
{{cite simbad
| title=NGC 2539
| accessdate=2015-06-19
}}
| dist_ly = 4,440 ly
| dist_pc = 1,363 pc[http://www.univie.ac.at/webda/cgi-bin/ocl_page.cgi?dirname=ngc2539 WEBDA: NGC 2539]
| size_v = 15'
| notes =
}}
NGC 2539 is an open cluster in the constellation Puppis, located at the north edge of the constellation. It was discovered by William Herschel on January 31, 1785. It is a moderately rich cluster and with little central concentration, with Trumpler class II1m.
Characteristics
The diameter of the cluster based on the location of possible members is estimated to be 7.4 parsecs (24 light years). The core radius of the cluster is 1.98 parsecs (6.5 light years), while the tidal radius is 15.2 parsecs (50 light years) and represents the average outer limit of NGC 2539, beyond which a star is unlikely to remain gravitationally bound to the cluster core.
151 stars, probable members of the cluster, are located within the central part of the cluster and 455 probable members are located within the angular radius of the cluster.{{cite journal|last1=Kharchenko|first1=N. V.|last2=Piskunov|first2=A. E.|last3=Schilbach|first3=E.|last4=Röser|first4=S.|last5=Scholz|first5=R.-D.|title=Global survey of star clusters in the Milky Way|journal=Astronomy & Astrophysics|date=3 October 2013|volume=558|pages=A53|doi=10.1051/0004-6361/201322302|url=ftp://cdsarc.u-strasbg.fr/pub/cats/J/A%2BA/558/A53/catalog.dat|arxiv = 1308.5822 |bibcode = 2013A&A...558A..53K |s2cid=118548517 }} 19 Puppis, visible near the edge of the cluster is a foreground star.{{cite web|title=NGC 2539 in Puppis|url=http://jthommes.com/Astro/NGC2539.htm|website=jthommes.com}} The turn-off mass of the cluster is at 3.1 {{solar mass|link=yes}}. The metallicity of the cluster is 0.14, higher than the solar one.{{cite journal|last1=Reddy|first1=A. B. S.|last2=Giridhar|first2=S.|last3=Lambert|first3=D. L.|title=Comprehensive abundance analysis of red giants in the open clusters NGC 2527, 2682, 2482, 2539, 2335, 2251 and 2266|journal=Monthly Notices of the Royal Astronomical Society|date=11 April 2013|volume=431|issue=4|pages=3338–3348|doi=10.1093/mnras/stt412|doi-access=free |arxiv = 1303.1104 |bibcode = 2013MNRAS.431.3338R }} The age of the cluster has been estimated to be as high as 630 myrs.{{cite journal|last1=Choo|first1=K. J.|last2=Kim|first2=S.-L.|last3=Yoon|first3=T. S.|last4=Chun|first4=M.-Y.|last5=Sung|first5=H.|last6=Park|first6=B.-G.|last7=Ann|first7=H. B.|last8=Lee|first8=M. G.|last9=Jeon|first9=Y.-B.|last10=Yuk|first10=I.-S.|title=Search for variable stars in the open cluster NGC 2539|journal=Astronomy & Astrophysics|date=5 February 2003|volume=399|issue=1|pages=99–104|doi=10.1051/0004-6361:20021704|bibcode = 2003A&A...399...99C |doi-access=free}}{{cite journal|last1=Lapasset|first1=E.|last2=Clariá|first2=J. J.|last3=Mermilliod|first3=J.-C.|title=UBV photometric study and basic parameters of the southern open cluster NGC 2539|journal=Astronomy and Astrophysics|date=September 2000|volume=361|pages=945–951|url=https://ui.adsabs.harvard.edu/?#abs/2000A%26A...361..945L|bibcode = 2000A&A...361..945L }}
Mermilliod and Mayor studied 11 red giants within the cluster, the brightest of which was mag 9.509 and of spectral type K5I-II, and two non-members. Three of this stars were found to be spectrographic binaries, while further studies indicated that one of them is a triple system. Two more are suspected double stars.{{cite journal|last1=Mermilliod|first1=J.-C.|last2=Andersen|first2=J.|last3=Latham|first3=D. W.|last4=Mayor|first4=M.|title=Red giants in open clusters|journal=Astronomy & Astrophysics|date=23 July 2007|volume=473|issue=3|pages=829–845|doi=10.1051/0004-6361:20078007|bibcode = 2007A&A...473..829M |doi-access=free}}{{cite journal|last1=Mermilliod|first1=J. C.|last2=Mayor|first2=M.|title=Red giants in open clusters. I. Binarity and stellar evolution in five Hyades-generation clusters : NGC 2447, 2539, 2632, 6633 and 6940|journal=Astronomy and Astrophysics|date=July 1989|volume=219|pages=125–141|url=https://ui.adsabs.harvard.edu/?#abs/1989A%26A...219..125M|language=en|bibcode = 1989A&A...219..125M }} Further studies revealed seven variable stars, 5 eclipsing binaries, one delta Scuti variable and one gamma Doradus variable, with the gamma Doratus variable star membership being questionable. From the eclipsing binaries, one is field star{{cite journal|last1=Choo|first1=K. J.|last2=Kim|first2=S.-L.|last3=Yoon|first3=T. S.|last4=Chun|first4=M.-Y.|last5=Sung|first5=H.|last6=Park|first6=B.-G.|last7=Ann|first7=H. B.|last8=Lee|first8=M. G.|last9=Jeon|first9=Y.-B.|last10=Yuk|first10=I.-S.|title=Search for variable stars in the open cluster NGC 2539|journal=Astronomy & Astrophysics|date=5 February 2003|volume=399|issue=1|pages=99–104|doi=10.1051/0004-6361:20021704|bibcode = 2003A&A...399...99C |doi-access=free}} and in a further study one more eclipsing binary (specifically a W Ursae Majoris variable) was found to lie at the background.{{cite journal|last1=Kiron|first1=Y. Ravi|last2=Sriram|first2=K.|last3=Vivekananda Rao|first3=P.|title=A photometric study of contact binaries V3 and V4 in NGC 2539|journal=Bulletin of the Astronomical Society of India|date=March 2012|volume=40|page=51|url=https://ui.adsabs.harvard.edu/?#abs/2012BASI...40...51K|bibcode = 2012BASI...40...51K }}
References
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