View source for IRAS 18357–0604

{{short description|Star in the constellation Scutum}}

{{Starbox begin|name=IRAS 18357–0604}}
{{Starbox image
|image=[[File:The_Yellow_Hypergiant_IRAS_18357-0604.png|290px]]
|caption =The yellow hypergiant star IRAS 18357–0604, viewed by the IRAC HEALPix survey. [[Stephenson 2 DFK 1]] is on the lower left. '''Credit''': Université de Strasbourg/CNRS (2003)
}}
{{Starbox observe|epoch=J2000|ra={{RA|18|38|23.405}}<ref name=gaia/>|dec={{DEC|-6|01|26.77}}<ref name=gaia/>|appmag_v=|constell=[[Scutum (constellation)|Scutum]]}}
{{Starbox character|type=[[Yellow hypergiant]]|class=A2Ia+<ref name=clark/>|b-v=|u-b=|variable=}}
{{Starbox astrometry|radial_v=|prop_mo_ra=|prop_mo_dec=|parallax=0.4247|p_error=0.3526|parallax_footnote=<ref name=gaia/>|dist_ly=19,600|dist_pc=6,000<ref name=clark/>|absmag_v=}}
{{Starbox detail
|mass=
|radius=167{{efn |name=RadiusCalculationFromTemperatureLuminosity | Applying the [[Stefan–Boltzmann law]] with a nominal solar [[effective temperature]] of 5,772&nbsp;[[Kelvin|K]]:
:<math>\sqrt{(5772/8913)^4 * 10^{5.2}} = 167.32\ R\odot</math>}}
|luminosity=158,500<ref name=clark/>
|temperature=8,913<ref name=clark/>|metal=|rotational_velocity=|age=}}
{{Starbox catalog|names=[[2MASS]]&nbsp;J18382341-0601269, TIC 7756628}} 
{{Starbox reference|Simbad=IRAS+18357-0604}}
{{Starbox end}}

'''IRAS 18357–0604''' is a [[yellow hypergiant]] (YHG) star located in the constellation of [[Scutum (constellation)|Scutum]], estimated to be about 19,600 [[light year]]s, or 6,000 [[parsec]]s, away. IRAS 18357–0604 is remarkably similar to [[IRC +10420]], another yellow [[hypergiant]] in the constellation of [[Aquila (constellation)|Aquila]].<ref name="clark" />

== Position ==
A distance of 6,000 parsecs (inferred from the systemic velocity of the star) would place IRAS 18357–0604 within the [[red supergiant]] (RSG) "association" in the [[Scutum–Centaurus Arm|Scutum-Centaurus arm]], which contains clusters such as [[RSGC1]] and [[RSGC2]]. The luminosity derived from the distance is consistent with IRAS 18357–0604 being formed from the same star formation burst as that which created the red supergiants in the area. The star is also located about 14 arcminutes from RSGC2, so the possibility of it being a runaway from the cluster cannot be excluded, but replicating its properties in such a scenario would require an unexpectedly extreme mass-loss rate during its preceding red supergiant phase.<ref name="clark" /> 

== Properties ==
IRAS 18357–0604 is likely to be a very luminous star, like all YHGs. Assuming a distance of 6,000 parsecs, the star would have a [[Bolometer|bolometric]] luminosity of about {{solar luminosity|160,000|link=y}}. Based on its spectrum, the star likely has a temperature of about {{val|9,000|ul=K|fmt=commas}}. Applying the [[Stefan-Boltzmann law]] to these parameters means that the star has a radius of about {{solar radius|167}}.<ref name="clark" />

== Evolutionary Status ==
In the RSG agglomerate of which IRAS 18357–0604 may be a part, RSGC1 and RSGC2 represent the youngest and oldest clusters in the area. This suggests that star formation in the area peaked over the last 10-20 million years, which means that evolved stars in the area have initial masses between {{solar mass|12|link=y}} and {{solar mass|22}}. If this age and mass range is applicable to the wider RSG association, the parameters of IRAS 18357–0604 are consistent with membership of the association. Theoretical models of rotating stars are able to reproduce IRAS 18357–0604's parameters assuming an initial mass of {{solar mass|18-20}} and an age comparable to that of RSGC1 (~12 Myr). If IRAS 18357's initial mass is closer to {{solar mass|18}}, it may be the progenitor of a core-collapse type IIb [[supernova]], and it might explode in the relatively near future. Instead, if its initial mass is closer to {{solar mass|20}}, it may evolve through an [[Luminous blue variable|LBV]] stage and get slightly hotter before exploding in a type IIb supernova.<ref name=clark/>

== Notes ==
{{notelist}}

== References ==
{{reflist|refs=<ref name=gaia>{{Cite Gaia DR2|4256090905608808320}}</ref>

<ref name=clark>{{Cite journal|last1=Clark|first1=J. S.|last2=Negueruela|first2=I.|last3=González-Fernández|first3=C.|date=2014-01-01|title=IRAS 18357-0604 - an analogue of the galactic yellow hypergiant IRC +10420?|bibcode=2014A&A...561A..15C|journal=Astronomy and Astrophysics|volume=561|pages=A15|doi=10.1051/0004-6361/201322772|arxiv=1311.3956|s2cid=53372226|issn=0004-6361}}</ref>}}

{{Stars of Scutum}}

[[Category:Scutum (constellation)]]
[[Category:A-type hypergiants]]
[[Category:IRAS catalogue objects]]
{{DEFAULTSORT:IRAS 18357-0604}}