HD 300933
{{use dmy dates|date=November 2024}}
{{short description|M-type supergiant in the constellation Vela}}
{{Starbox begin}}
{{Starbox image
| image=
{{Location mark
|image=Vela constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=HD 300933
|x=262|y=719
}}
|caption=Location of HD 300933 (circled)
}}
{{Starbox observe
|epoch=J2000
|constell=Vela
|ra={{RA|10|38|02.98879}}
|dec={{DEC|-56|49|01.9334}}
}}
{{Starbox character
|type=Red supergiant
|class=M2 Iab/Ib + B2V
|variable=
}}
{{Starbox astrometry
|parallax=0.3216
|p_error=0.0315
|absmag_v=
}}
{{Starbox detail
|component1=HD 300933
|temperature= {{val|3660|170}}
}}
{{Starbox catalog
|names={{odlist|2MASS=J10380298-5649019|CD=-56°3464|CPD=-56°3586|GSC=08609-02644|HD=300933/4|IRAS=10360-5633|TIC=458199516|TYC=8609-2644-1|UCAC3=67-102813|WDS=J10380-5649AB|WISE=J103803.02-564901.9|Gaia DR3=5352006438862476288}}
}}
{{Starbox reference
|Simbad=HD+300933
}}
{{Starbox end}}
HD 300933 (CPD-56°3586) is a red supergiant of spectral type M2 Iab/Ib in the southern constellation of Vela, close to the border with Carina. With an apparent magnitude of 8.29, it is too faint to be observed by the naked eye, but can be seen through binoculars. It is part of a binary system with a massive B-type main-sequence star (spectral type B2V) designated HD 300934. It is located roughly {{convert|3100|pc|ly|abbr=off}} away from the Solar System, but is approaching at a heliocentric radial velocity of {{val|-11.05|0.42|ul=km/s}}.
Stellar properties
The binary HD 300933/4 is a probable VV Cephei-type star with a composite spectrum similar to that of V381 Cephei (HR 8164), but with weaker emission lines of Fe II, S II, and Ni II (the "II" indicates that the elements are in their singly ionized state in spectroscopic notation). A detailed analysis of the pair was first conducted in 1970, which yielded an absolute magnitude of −5.3 and −2.5 in the V band for HD 300933 and HD 300934, respectively, albeit this was calculated using a distance smaller than modern estimates, at {{convert|2500|pc|ly|abbr=off}}. With an updated value of {{val|3100|ul=pc}}, its KS band absolute magnitude is gauged at −10.8.
HD 300933 displays infrared emissions that imply the existence of circumstellar dust at a temperature of {{convert|600|K|C F}}. Despite this, the system shows no signs of ultraviolet extinction or reddening, meaning that the light path from the B star does not cross the wind from the supergiant component. This is thought to be either due to an inclined orbit or an unfavorable orbital phase when it was observed in 1987.
The star is thought to be among the largest stars, though its precise size is highly uncertain; a radius of 806 {{Solar radius|link=y}} can be calculated from the luminosity and effective temperature provided by Healy et al. (2023), whereas Messineo et al. (2019) gives a much smaller estimate of 462 {{Solar radius}} (though they use a far smaller distance of 1574 or 1585 pc, which is inconsistent with the Gaia EDR3 parallax of {{val|0.3216|0.0315|ul=mas}}).
References
{{reflist|refs=
{{cite book|page=92|title=Guide to the Sun|first1=Kenneth J. H.|last1=Phillips|location=Cambridge|publisher=Cambridge University Press|year=1992|isbn=0-521-39788-X}}.
{{cite journal | journal=VizieR On-line Data Catalog | last1=Messineo | first1=M. | last2=Brown | first2=A.G.A. | title=K-M stars of class I candidate RSGs in Gaia DR2 | date=2019 | doi=10.26093/CDS/VIZIER.51580020|bibcode=2019yCat..51580020M}} [https://vizier.cds.unistra.fr/viz-bin/VizieR-5?-ref=VIZ6749729f2114dd&-out.add=.&-source=J/AJ/158/20/catalog&recno=370 Record for this source] at VizieR. Originally published in {{bibcode|2019AJ....158...20M}}.
{{cite Gaia EDR3|5352006438862476288}}
{{cite Gaia DR3|5352006438862476288}}
{{cite simbad|title=HD 300933|access-date=2024-11-29}}
}}
{{Vela (constellation)}}