| 释义 |
- Observations
- Stellar characteristics
- References
{{pp|small=yes}}{{Use dmy dates|date=October 2013}}{{Starbox begin}}{{Starbox image
| image =
| caption = VX Sagittarii, circled
}}{{Starbox observe
| epoch = J2000.0
| equinox = J2000.0 (ICRS)
| constell = Sagittarius
| ra = {{RA|18|08|04.04831}}[1]
| dec = {{DEC|-22|13|26.6327}}[1]
| appmag_v = 6.5 - 14.0[3]
}}{{Starbox character
| type = Red Hypergiant[4]
| class = M4eIa - M10eIa[5]
| appmag_1_passband = U
| appmag_1 = 11.72
| appmag_2_passband = B
| appmag_2 = 9.41
| appmag_3_passband = V
| appmag_3 = 6.52
| appmag_4_passband = I
| appmag_4 = 2.11
| appmag_5_passband = J
| appmag_5 = 1.23
| appmag_6_passband = H
| appmag_6 = 0.13
| appmag_7_passband = K
| appmag_7 = −0.50
| appmag_8_passband = L
| appmag_8 = −1.61
| r-i =
| v-r =
| b-v =
| u-b =
| j-h =
| j-k =
| variable = SRc[3]
}}{{Starbox astrometry
| radial_v = {{val|+6.47|3.37}}[4]
| prop_mo_ra = {{val|+0.36|0.76}}[4]
| prop_mo_dec = {{val|-2.92|0.78}}[4]
| parallax = 0.64
| p_error = 0.04
| parallax_footnote = [4]
| dist_ly =
| dist_pc =
| absmag_v =
| absmag_bol ={{Starbox detail
| mass = 12[11]
| radius = {{nowrap|between 1,120 and 1,550[4]}}, {{nowrap|1,350–1,940 (pulsation)[13]}}
| luminosity = {{nowrap|{{val|195,000|62,000}}[4]}}, 110,000–190,000[13]
| temperature = 2,900[16] (near min), {{nowrap|3,200-3,400 (near max)[11]}}, {{nowrap|2,400–3,300[13]}}
}}{{Starbox catalog
| names = VX Sgr, HIP 88838, BD−22°4575, CD−22°12589, HD 165674, 2MASS J18080404-2213266, AAVSO 1802-22
}}{{Starbox reference
| Simbad = VX+Sgr
}}{{Starbox end}}VX Sagittarii is a red supergiant or red hypergiant located more than 1.5 kiloparsec away from the Sun in the constellation of Sagittarius. It is a pulsating variable star with an unusually large magnitude range. It is also one of the largest stars discovered so far, with a radius varying between {{convert|1350 and 1940|solar radius|km au|lk=on}}. ObservationsThe star is classed as a cool semiregular variable of type SRc with a pulsational period of 732 days. The variations sometimes have an amplitude comparable to a long period variable, at other times they are much smaller. The spectral type varies between M4e around visual maximum and M9.8e at minimum light, and the luminosity class is Ia indicating a bright supergiant. The spectrum shows emission lines indicating that the star is losing mass through a strong stellar wind.[13] The annual parallax of VX Sagittarii has been measured extremely accurately using VLBI and found to be {{val|0.64|0.06|u="}}, indicating a distance of about 5,100 light years. This is compatible with the distance to Sagittarius OB1, the stellar association that VX Sagittarii is thought to belong to. Its radial velocity and proper motions are also consistent with other members of the association.[4] Stellar characteristicsThe effective temperature of VX Sagittarii is apparently highly variable from around 2,400 K at visual minimum to around 3,300 K near maximum. Such low temperatures are comparable to the very coolest AGB stars and unprecedented for a massive supergiant.[11][13] Its atmosphere is highly extended, irregular, and variable during the pulsations of the star, but the bolometric luminosity varies much less than the visual brightness and is calculated to be about {{solar luminosity|195,000}}. At an effective temperature of 3,300 K, the radius is expected to be somewhere between {{solar radius|1,120}} and {{solar radius|1,550}}.[4] Older studies frequently calculated higher luminosities.[1][25] The atmosphere of VX Sgr shows molecular water layers and SiO masers in the atmosphere, typical of an OH/IR star. References1. ^{{cite journal|bibcode=1988A&AS...72..259D|title=Mass loss rates in the Hertzsprung-Russell diagram|journal=Astronomy and Astrophysics Supplement Series|volume=72|pages=259|author1=De Jager|first1=C.|last2=Nieuwenhuijzen|first2=H.|last3=Van Der Hucht|first3=K. A.|year=1988}}
2. ^{{cite journal|bibcode=2010A&A...523A..18D|arxiv=1008.1083|title=Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles. II. CO line survey of evolved stars: Derivation of mass-loss rate formulae|journal=Astronomy and Astrophysics|volume=523|pages=A18|author1=De Beck|first1=E.|last2=Decin|first2=L.|last3=De Koter|first3=A.|last4=Justtanont|first4=K.|last5=Verhoelst|first5=T.|last6=Kemper|first6=F.|last7=Menten|first7=K. M.|year=2010|doi=10.1051/0004-6361/200913771}}
3. ^1 2 3 4 5 {{cite journal| author1=Lockwood, G.W. |author2=Wing, R. F.| title=The light and spectrum variations of VX Sagittarii, an extremely cool supergiant |journal=Monthly Notices of the Royal Astronomical Society| volume=198|issue=2| pages=385–404 |year=1982 |bibcode=1982MNRAS.198..385L | doi=10.1093/mnras/198.2.385}}
4. ^1 2 3 4 5 6 7 8 9 {{cite journal|arxiv=1804.00894|doi=10.3847/1538-4357/aabba6|bibcode=2018ApJ...859...14X|title=The Parallax of the Red Hypergiant VX Sgr with Accurate Tropospheric Delay Calibration|journal=The Astrophysical Journal|volume=859|issue=1|pages=14|year=2018|last1=Xu|first1=Shuangjing|last2=Zhang|first2=Bo|last3=Reid|first3=Mark J|last4=Menten|first4=Karl M|last5=Zheng|first5=Xingwu|last6=Wang|first6=Guangli}}
5. ^1 2 {{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|author1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 }}
6. ^1 {{Cite journal | last1 = Kiss | first1 = L. L. | last2 = Szabó | first2 = G. M. | last3 = Bedding | first3 = T. R. |author3-link= Tim Bedding| doi = 10.1111/j.1365-2966.2006.10973.x | title = Variability in red supergiant stars: Pulsations, long secondary periods and convection noise | journal = Monthly Notices of the Royal Astronomical Society | volume = 372 | issue = 4 | pages = 1721–1734 | year = 2006 | pmid = | pmc = |arxiv = astro-ph/0608438 |bibcode = 2006MNRAS.372.1721K }}
7. ^1 2 {{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|author1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}
8. ^1 {{Cite journal | last1 = Chen | first1 = X. | last2 = Shen | first2 = Z. Q. | last3 = Xu | first3 = Y. | doi = 10.1088/1009-9271/7/4/09 | title = Measuring the Distance of VX Sagittarii with SiO Maser Proper Motions | journal = Chinese Journal of Astronomy and Astrophysics | volume = 7 | issue = 4 | pages = 531 | year = 2007 | pmid = | pmc = }}
9. ^1 2 3 4 {{Cite journal| arxiv=0911.4422| author=Chiavassa | title=VLTI/AMBER spectro-interferometric imaging of VX Sgr's inhomogenous outer atmosphere | journal=Astronomy and Astrophysics | volume=511 | pages=A51 |year=2009 | author2=Lacour | author3=Millour | author4=Driebe | author5=Wittkowski | author6=Plez | author7=Thiebeaut | author8=Josselin | author9=Freytag | doi=10.1051/0004-6361/200913288 |bibcode = 2010A&A...511A..51C }}
10. ^1 {{Cite journal|arxiv=1010.5369v1|author1=Nicolas Mauron|author2=Eric Josselin|title=The mass-loss rates of red supergiants and the de Jager prescription|journal=Astronomy & Astrophysics|volume=526|pages=A156|year=2010|doi=10.1051/0004-6361/201013993|bibcode = 2011A&A...526A.156M }}
11. ^1 {{cite journal|bibcode=2007A&A...462..711G|arxiv=astro-ph/0609106|title=Lithium and zirconium abundances in massive Galactic O-rich AGB stars|journal=Astronomy and Astrophysics|volume=462|issue=2|pages=711|author1=García-Hernández|first1=D. A|last2=García-Lario|first2=P|last3=Plez|first3=B|last4=Manchado|first4=A|last5=d'Antona|first5=F|last6=Lub|first6=J|last7=Habing|first7=H|year=2007|doi=10.1051/0004-6361:20065785}}
[3][4][5][6][7][8][9][10][11]
}} | <<< 4. Westerlund 1-26 | 6. HR 5171 A >>> |
{{Stars of Sagittarius}} 10 : Sagittarius (constellation)|Objects with variable star designations|M-type hypergiants|Semiregular variable stars|Hipparcos objects|Henry Draper Catalogue objects|Durchmusterung objects|2MASS objects|Emission-line stars|M-type supergiants |