L2 Puppis
{{Short description|Star in the constellation Puppis}}
{{for|other stars with this Bayer designation|L Puppis}}
{{DISPLAYTITLE:L2 Puppis}}
{{Starbox begin
| name=L2 Puppis
}}
{{Starbox image
| image=
{{Location mark
|image=Puppis constellation map.svg|alt=|float=center|width=240
|label=|position=right
|mark=Red circle.svg|mark_width=8|mark_link=L2 Pup
|x=610|y=1050
}}
|caption=Location of L2 Puppis (circled)
}}
{{Starbox observe
| epoch=J2000
| appmag_v=5.10
2.6–6 (GCVS)
6–8 (1995 – )
| constell=Puppis
}}
{{Starbox character
| type=Red-giant branch
| variable=SRb
}}
{{Starbox astrometry
| parallax=15.61
| p_error=0.99
| absmag_v=
}}
{{Starbox detail
| luminosity={{val|1490|150|fmt=commas}}
| temperature={{val|3500|250|fmt=commas}}
| metal=
| rotation=
| rotational_velocity=
}}
{{Starbox catalog
| names=L2 Puppis, L02 Pup, HR 2748, CD−44°3227, HD 56096, LTT 2769, SAO 218549, HIP 34922
}}
{{Starbox reference
|Simbad = L2+Pup
}}
{{Starbox end}}
File:VLT SPHERE and NACO image of L2 Puppis.jpg and VLT NACO image of the nebulosity forming around L2 Puppis
(Credit: ESO/P. Kervella)]]
L2 Puppis (also known as HD 56096) is a giant star in the constellation of Puppis and is located between the bright stars Canopus and Sirius. It is a semi-regular pulsating star, and is intermittently visible to the naked eye.
History
The designation L2 has a tangled history. This star and another (OU Puppis) were both labelled with "L" by Nicolas-Louis de Lacaille when he created the constellation Puppis within Argo Navis. The two stars were labelled as "1.L" and "2.L" by Johann Elert Bode in his star catalogue published in 1801. Later authors used L1 and L2, usually with numeric subscripts (i.e. L1 and L2), but occasionally as superscripts. The subscripted designation is now universally used where typography allows for subscripts.
L2 Puppis was discovered to be variable by Benjamin Apthorp Gould in 1872, and was listed in Uranometria Argentina as 73 G. Puppis with magnitude 5.10v. It has never been given a formal variable star designation, unlike L1 Puppis which is OU Puppis.
Variability
File:L2PupLightCurve.png for L2 Puppis, plotted from Hipparcos data]]
L2 Puppis varies in apparent magnitude by about two magnitudes with a period of 140 days. The average brightness also varies slowly over several years so that the total range is given as magnitude 2.6–6.0. Since 1995 the average brightness has dropped so that the 140-day variations are now between about magnitude 6 and 8. The variation in light may be caused by a combination of radial pulsations in the star's atmosphere and by dimming from circumstellar dust.
Characteristics
L2 Puppis is most likely a red-giant branch star that has passed through the main sequence and is evolving to become a white dwarf. It is shedding mass at the rate of about {{solar mass| {{val|5|e=-7}}}} per year, forming a circumstellar dust disk and bipolar plumes of gas that are thought to be the start of a "butterfly"-type planetary nebula.
It has been calculated that the mass of L2 Puppis is currently about {{solar mass|0.66}} and its original mass was close to {{solar mass|one}} about 10 billion years ago. Other calculations give higher masses, for example {{solar mass|{{val|2|1|0.5}}}}, and younger ages such as 1.5 billion years.
L2 Puppis has a wide companion, a low-mass red dwarf separated by a minimum of 2,100 astronomical units.{{Cite journal |last=Kervella |first=Pierre |last2=Arenou |first2=Frédéric |last3=Thévenin |first3=Frédéric |date=January 2022 |title=Stellar and substellar companions from Gaia EDR3. Proper-motion anomaly and resolved common proper-motion pairs |journal=Astronomy and Astrophysics |language=en |volume=657 |pages=A7 |doi=10.1051/0004-6361/202142146 |doi-access=free |bibcode=2022A&A...657A...7K |arxiv=2109.10912 |issn=0004-6361}} It also has a visual 12th-magnitude companion, but it is actually a much more distant star not related to this system.{{cite DR3|5559704288431849472}} A hundred years ago, they were separated by about a minute of arc, but different proper motions mean that this is now about {{val|1.5|ul='}}.
Candidate planet
A candidate exoplanet has been found orbiting L2 Puppis every 4.69 years at a distance of {{Val|2.43|ul=AU}}. The mass is highly uncertain, at {{jupiter mass|12 ± 16}}, and it might just be a dense clump of gas and dust.
References
{{reflist|refs=
{{cite journal |author1=Bedding, T. R. |author1-link= Tim Bedding|author2=Kiss, L. L. |author3=Kjeldsen, H. |author4=Brewer, B. J. |author5=Dind, Z. E. |author6=Kawaler, S. D. |author7=Zijlstra, A. A. | title=The light curve of the semiregular variable L2 Puppis – II. Evidence for solar-like excitation of the oscillations | journal=Monthly Notices of the Royal Astronomical Society | volume=361 | issue=4 | pages=1375–1381 |date=August 2005 | doi=10.1111/j.1365-2966.2005.09281.x |doi-access= free| bibcode=2005MNRAS.361.1375B |arxiv = astro-ph/0507471 |s2cid= 16797010}}
}}
{{commons category|L2 Puppis}}
{{Stars of Puppis}}
{{DEFAULTSORT:Hd 56096}}
Category:Semiregular variable stars
Category:Post-asymptotic-giant-branch stars