Content deleted Content added
This radius came from the same source that has the 2,150 R☉ radius for Stephenson 2-18, which is unreliable due to a large uncertainty in the distance of >50%, which apply for all stars. Tags: Mobile edit Mobile web edit Advanced mobile edit |
Fixed typo. Tags: Mobile edit Mobile web edit |
||
| (4 intermediate revisions by 3 users not shown) | |||
Line 48:
{{Starbox end}}
'''Stephenson 2 DFK 49''' or '''St2-11''' is a putative post [[red supergiant]]<ref name=humphreys2020>{{cite journal |doi=10.3847/1538-3881/abab15 |arxiv=2008.01108 |last1=Humphreys |first1=Roberta M. |last2=Helmel |first2=Greta |last3=Jones |first3=Terry J. |last4=Gordon |first4=Michael S. |title=Exploring the Mass Loss Histories of the Red Supergiants |year=2020 |journal=[[The Astronomical Journal]]|volume=160 |issue=3 |page=145 |bibcode=2020AJ....160..145H |s2cid=220961677 |doi-access=free }}</ref> star in the constellation [[Scutum]], in the massive open cluster [[Stephenson 2]]. It is possibly one of the [[List of largest known stars|largest known stars]] with a radius estimated to be between {{convert|1074|solar radius|km au|abbr=off|lk=on}}<ref name="Davies2007" /> to {{convert|1,300|solar radius|km au|abbr=off|lk=off}},<ref name=humphreys2020>{{cite journal |doi=10.3847/1538-3881/abab15 |arxiv=2008.01108 |last1=Humphreys |first1=Roberta M. |last2=Helmel |first2=Greta |last3=Jones |first3=Terry J. |last4=Gordon |first4=Michael S. |title=Exploring the Mass Loss Histories of the Red Supergiants |year=2020 |journal=[[The Astronomical Journal]]|volume=160 |issue=3 |page=145 |bibcode=2020AJ....160..145H |s2cid=220961677 |doi-access=free }}</ref>
==Observation history==
Line 57:
In a later study from 2010, the same star was given the identifier number 11, and was grouped with a proposed cluster assumed to be associated with Stephenson 2, Stephenson 2-SW. The star showed maser emissions at some spectral lines. A later study corroborates this.<ref name="Masers">{{cite journal |last1=Verheyen |first1=L. |last2=Messineo |first2=M. |last3=Menten |first3=K.M. |title=SiO maser emission from red supergiants across the Galaxy |journal=Astronomy and Astrophysics |date=March 2012 |volume=541 |pages=A36 |doi=10.1051/0004-6361/201118265 |s2cid=55630819 |bibcode=2012A&A...541A..36V |arxiv=1203.4727 }}</ref> The study mentions a weak CO emission with radial velocities similar to Stephenson 2 DFK 49, but it is said to be unrelated due to being too intense for a red supergiant at Stephenson 2 DFK 49’s distance.<ref name="deguchi2010">{{cite journal |doi=10.1093/pasj/62.2.391 |title=SiO and H<sub>2</sub>O Maser Observations of Red Supergiants in Star Clusters Embedded in the Galactic Disk |year=2010 |last1=Deguchi |first1=Shuji |last2=Nakashima |first2=Jun-Ichi |last3=Zhang |first3=Yong |last4=Chong |first4=Selina S. N. |last5=Koike |first5=Kazutaka |last6=Kwok |first6=Sun |s2cid=24396370 |journal=[[Publications of the Astronomical Society of Japan]] |volume=62 |issue=2 |pages=391–407 |arxiv=1002.2492 |bibcode=2010PASJ...62..391D }}</ref>
Another study observed and studied 57 red supergiant stars across the galaxy and gave estimates of the stars' properties based on their [[Spectral Energy Distribution]]s, like [[luminosity]] and [[temperature]].
In 2016, it was compared to the [[yellow hypergiant]] star [[IRAS 18357-0604]], which can be found in the same general region as Stephenson 2.<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>
A recent study on red supergiant mass loss rates and histories notes it as the most interesting object in the cluster, because its spectral energy distribution, which has a significant [[infrared excess]], is similar to that of the famous and extreme red hypergiant [[VY Canis Majoris]]. However, Stephenson 2 DFK 49 is hotter. The study also estimates the possible mass loss rates of the star, as well as its other properties.<ref name="humphreys2020" />
==Properties==
Stephenson 2 DFK 49 was known to be an interesting object since its home cluster was first studied in depth.<ref name="Davies2007" /> An interesting note about Stephenson 2 DFK 49 is that it appears to be at the center of a bow-shock structure in infrared images. Because of its properties and likely position on the [[H-R diagram]], the authors of Davies 2007 stated that both it and [[Stephenson 2 DFK 1]] warranted further studies, especially in terms of stellar evolution. <ref name="Davies2007" /> Its properties, an earlier than usual spectral type compared to other stars in Stephenson 2, its luminosity and position on the HR Diagram indicate that it is similar to the extreme yellow hypergiant star IRC+10420 and Variable A in the [[Triangulum Galaxy]] (M33).<ref name="humphreys2020" /> Stephenson 2 DFK 49 is comparable to another extreme star in the vicinity of Stephenson 2, IRAS 18357-0604. Both are possible post-red supergiant stars,<ref name="clark" /> and both of them are comparable to the yellow hypergiant [[IRC+10420]]. [[File:Stephenson 2-18 and its surroundings.png|thumb|left|upright=1.2|[[Spitzer Space Telescope|Spitzer]] image centred on Stephenson 2-SW, with the main cluster towards upper left. The bow-shock feature centered on St2 DFK 49 (seen as a bright yellowish arc) is readily apparent.]]
===Luminosity===
In 2007, a study of the red supergiants in Stephenson 2 estimated its properties and determined a bolometric luminosity of {{Solar luminosity|245,000}}. <ref name="Davies2007" /> A 2012 study estimated and published the properties of numerous red supergiants and other supergiant stars. The study estimated Stephenson 2-11's luminosity at a much lower {{Solar luminosity|132,000}}, using [[spectral energy distribution]] (SED).<ref name="thomas">{{Cite journal|last1=Fok|first1=Thomas K. T|last2=Nakashima|first2=Jun-ichi|last3=Yung|first3=Bosco H. K|last4=Hsia|first4=Chih-Hao|last5=Deguchi|first5=Shuji|s2cid=53393926|year=2012|title=Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters|journal=[[The Astrophysical Journal]]|volume=760|issue=1|pages=65|arxiv=1209.6427|bibcode=2012ApJ...760...65F|doi=10.1088/0004-637X/760/1/65}}</ref>
Using the SED, Humphreys (2020) estimates a luminosity of {{Solar luminosity|390,000}}. However, it is noted that the estimated luminosity may be an underestimate, because it does not include excess radiation from warm dust. <ref name="humphreys2020" />
| |||