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{{short description|Star in the constellation Sagittarius}}
{{Starbox begin
{{Starbox begin
| name = HD 168625
| name = HD 168625
}}
{{Starbox image
| image = [[File:HD 168625 MUSE H-alpha.png|250px]]
| caption = HD 168625 and its nebula in [[Hydrogen-alpha]] with [[Multi-unit spectroscopic explorer|MUSE]]
}}
}}
{{Starbox observe
{{Starbox observe
| epoch = J2000
| epoch = J2000
| ra = {{RA|18|21|19.548}}<ref name=hipparcos/>
⚫
| ra = {{RA|18|21|19.548}}<ref name=hipparcos>{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653|author1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 }}</ref>
| dec = {{DEC|-16|22|16.0572}}<ref name=hipparcos/>
| dec = {{DEC|-16|22|16.0572}}<ref name=hipparcos/>
| appmag_v = 8.30–8.41<ref name=gcvs/>
| appmag_v = 8.44<ref name=clark>{{cite journal |journal = Astronomy & Astrophysics | date = 2012 |url=http://adsabs.harvard.edu/abs/1998A%26A...333..565S |title=On the nature of the galactic early-B hypergiants | last1 = Clark | first1 = J. S. |last2 = Najarro |first2=F. |last3 = Negueruela | first3 = I. |last4 = Ritchie | first4 = B. W. |last5 = Urbaneja | first5 = M. A. |last6 = Howarth | first6 = I. D. | format = pdf | arxiv = 1202.3991v1 | doi = 10.1051/0004-6361/201117472 |volume = 541 | pages = A145 |bibcode = 2012A&A...541A.145C}}</ref>
| constell = [[Sagittarius (constellation)|Sagittarius]]
| constell = [[Sagittarius (constellation)|Sagittarius]]
}}
}}
{{Starbox character
{{Starbox character
| class = B6Ia<sup>+</sup><ref name=chentsov/> {{nowrap|(B2—B8<ref name=mahy/>)}} May be B60 due to hypergiant designation
⚫
| class = B6Ia<sup>+</sup><ref name=chentsov>{{cite journal|last1=Chentsov|first1=E. L.|last2=Ermakov|first2=S. V.|last3=Klochkova|first3=V. G.|last4=Panchuk|first4=V. E.|last5=Bjorkman|first5=K. S.|last6=Miroshnichenko|first6=A. S.|title=An atlas of spectra of B6-A2 hypergiants and supergiants from 4800 to 6700Å|journal=Astronomy and Astrophysics|volume=397|issue=3|year=2003|pages=1035–1042|doi=10.1051/0004-6361:20021430|bibcode=2003A&A...397.1035C}}</ref> {{nowrap|(B2 - B8<ref name=mahy>{{cite journal|doi=10.1051/0004-6361/201628584|arxiv=1608.01087|title=Tracing back the evolution of the candidate LBV HD168625|journal=Astronomy & Astrophysics|year=2016|last1=Mahy|first1=L.|last2=Hutsemékers|first2=D.|last3=Royer|first3=P.|last4=Waelkens|first4=C.|bibcode = 2016A&A...594A..94M }}</ref>)}}
| b-v = +1.41<ref name=ducati/>
| b-v = +1.41<ref name=ducati/>
| u-b = +0.37<ref name=ducati/>
⚫
| u-b = +0.37<ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|pages=0|author1=Ducati|first1=J. R.|year=2002}}</ref>
| j-k = 0.599
| j-k = 0.599
| variable = [[Alpha Cygni variable|α Cygni]]<ref name=sterken/>
⚫
| variable = [[alpha cygni variable|alpha cygni]]<ref name=sterken>{{cite journal|bibcode=1999A&A...349..532S|title=Light variations of the blue hypergiants HD 168607 and HD 168625 (1973-1999)|journal=Astronomy and Astrophysics|volume=349|pages=532|author1=Sterken|first1=C.|last2=Arentoft|first2=T.|last3=Duerbeck|first3=H. W.|last4=Brogt|first4=E.|year=1999}}</ref>
}}
}}
{{Starbox astrometry
{{Starbox astrometry
| radial_v = −4.00<ref name=KharchenkoScholz2007/>
⚫
| radial_v = -4.00<ref name="KharchenkoScholz2007">{{cite journal|last1=Kharchenko|first1=N.V.|last2=Scholz|first2=R.-D.|last3=Piskunov|first3=A.E.|last4=Röser|first4=S.|last5=Schilbach|first5=E.|title=Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ∼55000 stars and mean radial velocities of 516 Galactic open clusters and associations|journal=Astronomische Nachrichten|volume=328|issue=9|year=2007|pages=889–896|doi=10.1002/asna.200710776|bibcode=2007AN....328..889K|arxiv = 0705.0878 }}</ref>
| prop_mo_ra = -0.71 ± 1.20<ref name=hipparcos/>
| prop_mo_ra = {{val|−0.71|1.20}}<ref name=hipparcos/>
| prop_mo_dec = +0.01 ± 0.74<ref name=hipparcos/>
| prop_mo_dec = {{val|+0.01|0.74}}<ref name=hipparcos/>
| parallax = 2.52
| parallax = 0.6212
| p_error = 1.10
| p_error = 0.0640
| parallax_footnote = <ref name=hipparcos/>
| parallax_footnote = <ref name=dr2/>
| dist_pc = 2,800<ref name=mahy/>
| dist_pc =
| absmag_v = &minus;8.39<ref name=mahy/>
| absmag_v = −8.39<ref name=mahy/>
}}
}}
{{Starbox detail
{{Starbox detail
| source = <ref name=mahy/>
| source = <ref name=mahy/>
| luminosity = 380,000
| luminosity = 380,000
| radius = 105
| temperature = 14,000
| temperature = 14,000
| gravity = 1.74
| gravity = 1.74
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}}
}}
{{Starbox catalog
{{Starbox catalog
| names = [[Variable star designation|V4030]]&nbsp;Sgr, [[Henry Draper catalogue|HD&nbsp;]]168625, [[Bonner Durchmusterung|BD]]&nbsp;-16°4830, [[Smithsonian Astrophysical Observatory Star Catalog|SAO&nbsp;]]161375, [[Hipparcos catalogue|HIP&nbsp;]]89963, [[AAVSO]]&nbsp;1815-168
| names = [[Variable star designation|V4030]] Sgr, [[Henry Draper Catalogue|HD]] 168625, [[Durchmusterung|BD]] −16°4830, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 161375, [[Hipparcos catalogue|HIP]] 89963, [[AAVSO]] 1815-168
}}
}}
{{Starbox reference
{{Starbox reference
Line 40: Line 46:
}}
}}
{{Starbox end}}
{{Starbox end}}
⚫
'''HD 168625''' ('''V4030 Sagittarii''') is a blue [[hypergiant]] star and candidate [[luminous blue variable]] located in the [[constellation]] of [[Sagittarius (constellation)|Sagittarius]] easy to see with [[amateur astronomy|amateur]] [[telescope]]s. It forms a [[double star|visual pair]] with the also blue hypergiant (and luminous blue variable) [[HD 168607]] and is located to the south-east of M17, the [[Omega Nebula]].
[[File:A Cosmic Rose with Many Names.jpg|thumb|left|upright=1.0|HD 168625 is the left star of the pair below the [[Omega Nebula]]. The other is the hypergiant [[HD 168607]].]]
⚫
'''HD 168625''' ('''V4030 Sgr''') is a blue [[hypergiant]] and candidate [[luminous blue variable]] located in the [[constellation]] of [[Sagittarius (constellation)|Sagittarius]] easy to see with [[amateur astronomy|amateur]] [[telescope]]s. It forms a [[double star|visual pair]] with the also blue hypergiant (and luminous blue variable) [[HD 168607]] and is located to the south-east of M17, the [[Omega Nebula]].


==Distance==
Its distance and association with that nebula and the mentioned star is dubious; while some authors think both stars are physically associated and belong to the [[stellar association]] [[Serpens OB1]],<ref name=Chentsov2004>
The distance of HD 168625 and its association with the Omega Nebula and HD 168607 is in doubt; while some authors think both stars are physically associated and belong to the [[stellar association]] [[Serpens OB1]],<ref name=Chentsov2004/> at a distance to the [[Sun]] of {{convert|2.2|kpc|ly|lk=on}},<ref name=Naze2011/> or for both per [[Gaia Data Release 2]] about {{convert|1.6|kpc|ly}},<ref name=dr2/> a 2002 study estimates this star is farther, at about {{convert|2.8|kpc|ly}} and unrelated to the other two objects.<ref name=Pasquali2002/>

⚫
== Physical characteristics ==
[[File:V4030SgrLightCurve.png|thumb|left|A [[Photometric_system#Photometric_letters|visual band]] [[light curve]] for V4030 Sagittarii, plotted from ''[[All Sky Automated Survey|ASAS]]'' data<ref name=ASASServer/>]]
⚫
Assuming a distance of 2.2 kiloparsecs, the star would be 220,000 times brighter than the [[Sun luminosity|Sun]], having a [[Effective temperature|surface temperature]] of 12,000 [[Kelvin|K]].<ref name=Naze2011/> At that distance it can be calculated to be losing mass through a fierce [[stellar wind]] at roughly {{val|1.46|e=-6|ul=solar masses}} per year<ref name=Umana2010/> however this is to be muted somewhat as work realized in 2012 from the [[Very Large Telescope|VLT]] reveal a [[binary star]] system &ndash; <ref name=Martayan2012/> a companion exists around 4.5 [[magnitude (astronomy)|magnitude]]s fainter than the primary.<ref name=Martayan2016/>

==Nebula==
⚫
The most notable characteristic of HD 168625 is the presence of a [[nebula]] surrounding it that was discovered in 1994<ref name=Hutsemekers1994/> and that has been studied with the help of several instruments and observatories and telescopes that include among others the [[Hubble Space Telescope]]<ref name=Pasquali2002/> and the [[Very Large Telescope|VLT]].<ref name=Umana2010/>

⚫
Said studies show that HD 168625 is actually surrounded by two nebulae: an inner one that has an elliptical shape and a very complex structure that includes arcs and filaments,<ref name=Pasquali2002/> and a much larger outer one discovered with the help of the [[Spitzer Space Telescope]] that has a [[Bipolar nebula|bipolar shape]] and that looks like a clone of the one surrounding [[Sanduleak -69° 202]], the progenitor of the [[supernova]] [[1987A]] in the [[Large Magellanic Cloud]].<ref name=Smith2007/> This suggests Sanduleak &minus;69° 202 was also a luminous blue variable as well as the possibility of HD 168625 exploding as a [[Type II supernova]] in the near future.<ref name=Smith2007/>

East-north-east of the star and nebula is HD 168701 (HIP 90001), an eclipsing [[beta Lyrae variable|binary of beta Lyrae type]].<ref name=simbad>{{cite simbad |title=HD 168701|access-date=2021-01-05}}</ref> It is at about six times the angular separation of [[HD 168607]] viewed from the solar system and is the third very bright point to the south-east of the nebula. Its parallax of 0.7106 ± 0.0451 [[milliarcseconds|mas]] implies it is about {{convert|1700|parsec}} away.<ref name=simbad/>

⚫
== References ==
⚫
{{reflist|refs=

⚫
<ref name=hipparcos>{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|last1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 |s2cid=18759600}}</ref>

⚫
<ref name=chentsov>{{cite journal|last1=Chentsov|first1=E. L.|last2=Ermakov|first2=S. V.|last3=Klochkova|first3=V. G.|last4=Panchuk|first4=V. E.|last5=Bjorkman|first5=K. S.|author5-link=Karen Bjorkman|last6=Miroshnichenko|first6=A. S.|title=An atlas of spectra of B6-A2 hypergiants and supergiants from 4800 to 6700Å|journal=Astronomy and Astrophysics|volume=397|issue=3|year=2003|pages=1035–1042|doi=10.1051/0004-6361:20021430|bibcode=2003A&A...397.1035C|doi-access=free}}</ref>

<ref name=ASASServer>{{cite web |title=ASAS All Star Catalogue |url=http://www.astrouw.edu.pl/asas/?page=aasc |publisher=The All Sky Automated Survey |access-date=8 December 2021}}</ref>

<ref name=mahy>{{cite journal|doi=10.1051/0004-6361/201628584|arxiv=1608.01087|title=Tracing back the evolution of the candidate LBV HD168625|journal=Astronomy & Astrophysics|volume=594|pages=A94|year=2016|last1=Mahy|first1=L.|last2=Hutsemékers|first2=D.|last3=Royer|first3=P.|last4=Waelkens|first4=C.|bibcode = 2016A&A...594A..94M |s2cid=119243390}}</ref>

⚫
<ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|pages=0|last1=Ducati|first1=J. R.|year=2002}}</ref>

⚫
<ref name=sterken>{{cite journal|bibcode=1999A&A...349..532S|title=Light variations of the blue hypergiants HD 168607 and HD 168625 (1973-1999)|journal=Astronomy and Astrophysics|volume=349|pages=532|last1=Sterken|first1=C.|last2=Arentoft|first2=T.|last3=Duerbeck|first3=H. W.|last4=Brogt|first4=E.|year=1999}}</ref>

⚫
<ref name=KharchenkoScholz2007>{{cite journal|last1=Kharchenko|first1=N.V.|last2=Scholz|first2=R.-D.|last3=Piskunov|first3=A.E.|last4=Röser|first4=S.|last5=Schilbach|first5=E.|title=Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations|journal=Astronomische Nachrichten|volume=328|issue=9|year=2007|pages=889–896|doi=10.1002/asna.200710776|bibcode=2007AN....328..889K|arxiv = 0705.0878 |s2cid=119323941}}</ref>

<ref name=Chentsov2004>
{{cite journal
{{cite journal
|last1=Chentsov |first1=E.L. |last2=Gorda |first2=E.S.
|last1=Chentsov |first1=E.L. |last2=Gorda |first2=E.S.
Line 52: Line 88:
|bibcode=2004AstL...30..461C
|bibcode=2004AstL...30..461C
|doi=10.1134/1.1774398
|doi=10.1134/1.1774398
|s2cid=122348932 }}</ref>
}}</ref> at a distance to the [[Sun]] of 2.2 kilo[[parsec]]s (7.200 [[light year]]s),<ref name=Naze2011>

<ref name=Naze2011>
{{cite journal
{{cite journal
|last1=Nazé |first1=Y. |last2=Rauw |first2=G. |last3=Hutsemékers |first3=D.
|last1=Nazé |first1=Y. |last2=Rauw |first2=G. |last3=Hutsemékers |first3=D.
Line 61: Line 99:
|bibcode=2012A&A...538A..47N
|bibcode=2012A&A...538A..47N
|doi=10.1051/0004-6361/201118040
|doi=10.1051/0004-6361/201118040
|arxiv = 1111.6375 |s2cid=43688343 }}</ref>
|arxiv = 1111.6375 }}</ref> others think HD 168625 is farther, at a distance estimated to be 2.8 kilo[[parsec]]s (9,100 [[light year]]s) and unrelated to the former objects.<ref name=Pasquali2002>

<ref name=Pasquali2002>
{{cite journal
{{cite journal
|last1=Pasquali |first1=A. |last2=Nota |first2=A. |last3=Smith |first3=L.J. |last4=Akiyama |first4=S. |last5=Messineo |first5=M. |last6=Clampin |first6=M.
|last1=Pasquali |first1=A. |last2=Nota |first2=A. |author2-link=Antonella Nota|last3=Smith |first3=L.J. |last4=Akiyama |first4=S. |last5=Messineo |first5=M. |last6=Clampin |first6=M.
|date=2002
|date=2002
|title=Multiwavelength Study of the Nebula Associated with the Galactic LBV Candidate HD 168625
|title=Multiwavelength Study of the Nebula Associated with the Galactic LBV Candidate HD 168625
Line 70: Line 110:
|bibcode=2002AJ....124.1625P
|bibcode=2002AJ....124.1625P
|doi=10.1086/341820
|doi=10.1086/341820
|arxiv = astro-ph/0207613 }}</ref>
|arxiv = astro-ph/0207613 |s2cid=118968760 }}</ref>


<ref name=Martayan2012>
⚫
== Physical characteristics ==

⚫
Assuming a distance of 2.2 kilo[[parsec]]s, HD 168625 is 220,000 times brighter than the [[Sun luminosity|Sun]], having a [[surface temperature]] of 12,000 [[Kelvin|K]].<ref name=Naze2011/> It is losing mass through a very strong [[stellar wind]] at a rate of roughly 1.46×10<sup>−6</sup> [[solar mass]]es per year<ref name=Umana2010/> and observations realized in 2012 with the help of the [[Very Large Telescope|VLT]] show it's actually a [[binary star]],<ref name=Martayan2012>
{{cite journal
{{cite journal
|last1=Martayan |first1=C. |last2=Lobel |first2=A. |last3=Baade |first3=D. |last4=Blomme |first4=R. |last5=Frémat |first5=Y. |last6=Lebouquin |first6=J.-B. |last7=Selman |first7=F. |last8=Girard |first8=J. |last9=Mérand |first9=A. |last10=Montagnier |first10=G. |last11=Patru |first11=F. |last12=Mawet |first12=D. |last13=Martins |first13=F. |last14=Rivinius |first14=Th. |last15=Štefl |first15=S. |last16=Zorec |first16=J. |last17=Semaan |first17=T. |last18=Mehner |first18=A. |last19=Kervella |first19=P. |last20=Sana |first20=H. |last21=Schödel |first21=R. |date=2012
|last1=Martayan |first1=C. |last2=Lobel |first2=A. |last3=Baade |first3=D. |last4=Blomme |first4=R. |last5=Frémat |first5=Y. |last6=Lebouquin |first6=J.-B. |last7=Selman |first7=F. |last8=Girard |first8=J. |last9=Mérand |first9=A. |last10=Montagnier |first10=G. |last11=Patru |first11=F. |last12=Mawet |first12=D. |last13=Martins |first13=F. |last14=Rivinius |first14=Th. |last15=Štefl |first15=S. |last16=Zorec |first16=J. |last17=Semaan |first17=T. |last18=Mehner |first18=A. |last19=Kervella |first19=P. |last20=Sana |first20=H. |last21=Schödel |first21=R. |date=2012
Line 81: Line 119:
|volume=464 |pages=293
|volume=464 |pages=293
|bibcode=2012ASPC..464..293M
|bibcode=2012ASPC..464..293M
}}</ref>
}}</ref> with the companion being around 4.5 [[magnitude (astronomy)|magnitude]]s fainter than the primary.<ref name=Martayan2016>{{cite journal

<ref name=Martayan2016>{{cite journal
|last1=Martayan |first1=C. |last2=Lobel |first2=A. |last3=Baade |first3=D. |last4=Mehner |first4=A. |last5=Rivinius |first5=T. |last6=Boffin |first6=Henry M. J. |last7= Ronny |first7= B. |last8=Girard |first8=J. |last9=Mérand |first9=A. |last10=Montagnier |first10=G. |last11=Patru |first11=F. |last12=Mawet |first12=D. |last13=Martins |first13=F. |last14=Rivinius |first14=Th. |last15=Štefl |first15=S. |last16=Zorec |first16=J. |last17=Semaan |first17=T. |last18=Mehner |first18=A. |last19=Kervella |first19=P. |last20=Sana |first20=H. |last21=Schödel |first21=R. |date=2016
|last1=Martayan |first1=C. |last2=Lobel |first2=A. |last3=Baade |first3=D. |last4=Mehner |first4=A. |last5=Rivinius |first5=T. |last6=Boffin |first6=Henry M. J. |last7= Ronny |first7= B. |last8=Girard |first8=J. |last9=Mérand |first9=A. |last10=Montagnier |first10=G. |last11=Patru |first11=F. |last12=Mawet |first12=D. |last13=Martins |first13=F. |last14=Rivinius |first14=Th. |last15=Štefl |first15=S. |last16=Zorec |first16=J. |last17=Semaan |first17=T. |last18=Mehner |first18=A. |last19=Kervella |first19=P. |last20=Sana |first20=H. |last21=Schödel |first21=R. |date=2016
|title=Luminous blue variables: An imaging perspective on their binarity and near environment
|title=Luminous blue variables: An imaging perspective on their binarity and near environment
|journal=[[Astronomy & Astrophysics]]
|journal=[[Astronomy & Astrophysics]]
|volume=587 |id=A115
|volume=587 |pages=A115 |id=A115
|bibcode=2016A&A...587A.115M
|bibcode=2016A&A...587A.115M
|arxiv = 1601.03542 |doi = 10.1051/0004-6361/201526578 }}</ref>
|arxiv = 1601.03542 |doi = 10.1051/0004-6361/201526578 |s2cid=1755296 |url=https://hal.archives-ouvertes.fr/hal-01255772/file/article12LBVn5.pdf }}</ref>


<ref name=Hutsemekers1994>
However, its most notable characteristic is the presence of a [[nebula]] surrounding it that was discovered in 1994<ref name=Hutsemekers1994>
{{cite journal
{{cite journal
|last1=Hutsemekers |first1=D. |last2=vanDrom |first2=E. |last3=Gosset |first3=E. |last4=Melnick |first4=J.
|last1=Hutsemekers |first1=D. |last2=vanDrom |first2=E. |last3=Gosset |first3=E. |last4=Melnick |first4=J.
Line 97: Line 137:
|volume=2904 |pages=906–914
|volume=2904 |pages=906–914
|bibcode=1994A&A...290..906H
|bibcode=1994A&A...290..906H
}}</ref>
⚫
}}</ref> and that has been studied with the help of several instruments and observatories and telescopes that include among others the [[Hubble Space Telescope]]<ref name=Pasquali2002/> and the [[Very Large Telescope|VLT]].<ref name=Umana2010>

<ref name=Umana2010>
{{cite journal
{{cite journal
|last1=Umana |first1=G. |last2=Buemi |first2=C.S. |last3=Trigilio |first3=C. |last4=Leto |first4=P. |last5=Hora |first5=J.L.
|last1=Umana |first1=G. |last2=Buemi |first2=C.S. |last3=Trigilio |first3=C. |last4=Leto |first4=P. |last5=Hora |first5=J.L.
Line 106: Line 148:
|bibcode=2010ApJ...718.1036U
|bibcode=2010ApJ...718.1036U
|doi=10.1088/0004-637X/718/2/1036
|doi=10.1088/0004-637X/718/2/1036
}}</ref>
|doi-access=free }}</ref>


<ref name=Smith2007>
⚫
Said studies show that HD 168625 is actually surrounded by two nebulae: an inner one that has an elliptical shape and a very complex structure that includes arcs and filaments,<ref name=Pasquali2002/> and a much larger outer one discovered with the help of the [[Spitzer Space Telescope]] that has a [[Bipolar nebula|bipolar shape]] and that looks like a clone of the one surrounding [[Sanduleak -69° 202]], the progenitor of the [[supernova]] [[1987A]] in the [[Large Magellanic Cloud]].<ref name=Smith2007>
{{cite journal
{{cite journal
|last1=Smith |first1=Nathan
|last1=Smith |first1=Nathan
Line 117: Line 159:
|bibcode=2007AJ....133.1034S
|bibcode=2007AJ....133.1034S
|doi=10.1086/510838
|doi=10.1086/510838
|arxiv = astro-ph/0611544 |s2cid=17598600
|arxiv = astro-ph/0611544 }}</ref> This suggests Sanduleak -69° 202 was also a luminous blue variable as well as the possibility of HD 168625 exploding as a [[Type II supernova]] in the near future.<ref name=Smith2007/>
}}</ref>


<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref>
⚫
== References ==

⚫
{{reflist}}
<ref name=dr2>{{cite DR2|4097796621733266432}}</ref>

}}


{{Stars of Sagittarius}}
{{Stars of Sagittarius}}


{{DEFAULTSORT:HD 168625}}
[[Category:B-type hypergiants]]
[[Category:B-type hypergiants]]
[[Category:Luminous blue variables]]
[[Category:Luminous blue variables]]

Latest revision as of 16:32, 31 August 2024

HD 168625

HD 168625 and its nebula in Hydrogen-alpha with MUSE
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 21m 19.548s[1]
Declination −16° 22′ 16.0572″[1]
Apparent magnitude (V) 8.30–8.41[2]
Characteristics
Spectral type B6Ia+[3] (B2—B8[4]) May be B60 due to hypergiant designation
U−B color index +0.37[5]
B−V color index +1.41[5]
J−K color index 0.599
Variable type α Cygni[6]
Astrometry
Radial velocity (Rv)−4.00[7] km/s
Proper motion (μ) RA: −0.71±1.20[1] mas/yr
Dec.: +0.01±0.74[1] mas/yr
Parallax (π)0.6212 ± 0.0640 mas[8]
Distanceapprox. 5,300 ly
(approx. 1,600 pc)
Absolute magnitude (MV)−8.39[4]
Details[4]
Radius105 R☉
Luminosity380,000 L☉
Surface gravity (log g)1.74 cgs
Temperature14,000 K
Rotational velocity (v sin i)60 km/s
Other designations
V4030 Sgr, HD 168625, BD −16°4830, SAO 161375, HIP 89963, AAVSO 1815-168
Database references
SIMBADdata

HD 168625 (V4030 Sagittarii) is a blue hypergiant star and candidate luminous blue variable located in the constellation of Sagittarius easy to see with amateur telescopes. It forms a visual pair with the also blue hypergiant (and luminous blue variable) HD 168607 and is located to the south-east of M17, the Omega Nebula.

Distance

[edit]

The distance of HD 168625 and its association with the Omega Nebula and HD 168607 is in doubt; while some authors think both stars are physically associated and belong to the stellar association Serpens OB1,[9] at a distance to the Sun of 2.2 kiloparsecs (7,200 ly),[10] or for both per Gaia Data Release 2 about 1.6 kiloparsecs (5,200 ly),[8] a 2002 study estimates this star is farther, at about 2.8 kiloparsecs (9,100 ly) and unrelated to the other two objects.[11]

Physical characteristics

[edit]
A visual band light curve for V4030 Sagittarii, plotted from ASAS data[12]

Assuming a distance of 2.2 kiloparsecs, the star would be 220,000 times brighter than the Sun, having a surface temperature of 12,000 K.[10] At that distance it can be calculated to be losing mass through a fierce stellar wind at roughly 1.46×10−6 solar masses per year[13] however this is to be muted somewhat as work realized in 2012 from the VLT reveal a binary star system – [14] a companion exists around 4.5 magnitudes fainter than the primary.[15]

Nebula

[edit]

The most notable characteristic of HD 168625 is the presence of a nebula surrounding it that was discovered in 1994[16] and that has been studied with the help of several instruments and observatories and telescopes that include among others the Hubble Space Telescope[11] and the VLT.[13]

Said studies show that HD 168625 is actually surrounded by two nebulae: an inner one that has an elliptical shape and a very complex structure that includes arcs and filaments,[11] and a much larger outer one discovered with the help of the Spitzer Space Telescope that has a bipolar shape and that looks like a clone of the one surrounding Sanduleak -69° 202, the progenitor of the supernova 1987A in the Large Magellanic Cloud.[17] This suggests Sanduleak −69° 202 was also a luminous blue variable as well as the possibility of HD 168625 exploding as a Type II supernova in the near future.[17]

East-north-east of the star and nebula is HD 168701 (HIP 90001), an eclipsing binary of beta Lyrae type.[18] It is at about six times the angular separation of HD 168607 viewed from the solar system and is the third very bright point to the south-east of the nebula. Its parallax of 0.7106 ± 0.0451 mas implies it is about 1,700 parsecs (5,500 ly) away.[18]

References

[edit]
  1. ^ a b c d Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. ^ Chentsov, E. L.; Ermakov, S. V.; Klochkova, V. G.; Panchuk, V. E.; Bjorkman, K. S.; Miroshnichenko, A. S. (2003). "An atlas of spectra of B6-A2 hypergiants and supergiants from 4800 to 6700Å". Astronomy and Astrophysics. 397 (3): 1035–1042. Bibcode:2003A&A...397.1035C. doi:10.1051/0004-6361:20021430.
  4. ^ a b c Mahy, L.; Hutsemékers, D.; Royer, P.; Waelkens, C. (2016). "Tracing back the evolution of the candidate LBV HD168625". Astronomy & Astrophysics. 594: A94. arXiv:1608.01087. Bibcode:2016A&A...594A..94M. doi:10.1051/0004-6361/201628584. S2CID 119243390.
  5. ^ a b Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  6. ^ Sterken, C.; Arentoft, T.; Duerbeck, H. W.; Brogt, E. (1999). "Light variations of the blue hypergiants HD 168607 and HD 168625 (1973-1999)". Astronomy and Astrophysics. 349: 532. Bibcode:1999A&A...349..532S.
  7. ^ Kharchenko, N.V.; Scholz, R.-D.; Piskunov, A.E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889–896. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
  8. ^ a b Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  9. ^ Chentsov, E.L.; Gorda, E.S. (2004). "Spatial Closeness of the White Hypergiants HD 168607 and HD 168625". Astronomy Letters. 30 (7): 145–180. Bibcode:2004AstL...30..461C. doi:10.1134/1.1774398. S2CID 122348932.
  10. ^ a b Nazé, Y.; Rauw, G.; Hutsemékers, D. (2012). "The first X-ray survey of Galactic luminous blue variables". Astronomy & Astrophysics. 538: A47. arXiv:1111.6375. Bibcode:2012A&A...538A..47N. doi:10.1051/0004-6361/201118040. S2CID 43688343. A47.
  11. ^ a b c Pasquali, A.; Nota, A.; Smith, L.J.; Akiyama, S.; Messineo, M.; Clampin, M. (2002). "Multiwavelength Study of the Nebula Associated with the Galactic LBV Candidate HD 168625". The Astronomical Journal. 124 (3): 1625–1635. arXiv:astro-ph/0207613. Bibcode:2002AJ....124.1625P. doi:10.1086/341820. S2CID 118968760.
  12. ^ "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
  13. ^ a b Umana, G.; Buemi, C.S.; Trigilio, C.; Leto, P.; Hora, J.L. (2010). "Spitzer, Very Large Telescope, and Very Large Array Observations of the Galactic Luminous Blue Variable Candidate HD 168625". The Astrophysical Journal. 718 (2): 1036–1045. Bibcode:2010ApJ...718.1036U. doi:10.1088/0004-637X/718/2/1036.
  14. ^ Martayan, C.; Lobel, A.; Baade, D.; Blomme, R.; Frémat, Y.; Lebouquin, J.-B.; Selman, F.; Girard, J.; Mérand, A.; Montagnier, G.; Patru, F.; Mawet, D.; Martins, F.; Rivinius, Th.; Štefl, S.; Zorec, J.; Semaan, T.; Mehner, A.; Kervella, P.; Sana, H.; Schödel, R. (2012). "On the Binarity of LBV Stars". ASP Conference Proceedings. 464: 293. Bibcode:2012ASPC..464..293M.
  15. ^ Martayan, C.; Lobel, A.; Baade, D.; Mehner, A.; Rivinius, T.; Boffin, Henry M. J.; Ronny, B.; Girard, J.; Mérand, A.; Montagnier, G.; Patru, F.; Mawet, D.; Martins, F.; Rivinius, Th.; Štefl, S.; Zorec, J.; Semaan, T.; Mehner, A.; Kervella, P.; Sana, H.; Schödel, R. (2016). "Luminous blue variables: An imaging perspective on their binarity and near environment" (PDF). Astronomy & Astrophysics. 587: A115. arXiv:1601.03542. Bibcode:2016A&A...587A.115M. doi:10.1051/0004-6361/201526578. S2CID 1755296. A115.
  16. ^ Hutsemekers, D.; vanDrom, E.; Gosset, E.; Melnick, J. (1994). "A dusty nebula around the luminous blue variable candidate HD 168625". Astronomy and Astrophysics. 2904: 906–914. Bibcode:1994A&A...290..906H.
  17. ^ a b Smith, Nathan (2007). "Discovery of a Nearby Twin of SN 1987A's Nebula around the Luminous Blue Variable HD 168625: Was Sk -69 202 an LBV?". The Astronomical Journal. 133 (3): 1034–1040. arXiv:astro-ph/0611544. Bibcode:2007AJ....133.1034S. doi:10.1086/510838. S2CID 17598600.
  18. ^ a b "HD 168701". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-05.
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