Balmer jump: Difference between revisions
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Gohlanblack (talk | contribs) m add 'break' (often seen in galactic spectra); correct last decimal of Balmer series from 364.6 to the correct 364.5 (more precisely 364.50682) |
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[[File:Balmerov skok EA.jpg|right|frame|Balmer jump of two stars: [[Epsilon Orionis]] (O9.7 V) on the top and [[Beta Tauri]] (B7 III) on the bottom. The vertical blue line represents the limit of the Balmer series.]] |
[[File:Balmerov skok EA.jpg|right|frame|Balmer jump of two stars: [[Epsilon Orionis]] (O9.7 V) on the top and [[Beta Tauri]] (B7 III) on the bottom. The vertical blue line represents the limit of the Balmer series.]] |
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The '''Balmer jump''' or '''Balmer |
The '''Balmer jump''', '''Balmer discontinuity''', or '''Balmer break''' is the difference of [[Radiance|intensity]] of the [[Star|stellar]] [[continuum spectrum]] on either side of the limit of the [[Balmer series]] of [[hydrogen]], at approximately 364.5 [[Nanometre|nm]]. It is caused by [[electron]]s being completely [[Ionization|ionized]] directly from the second [[energy level]] of a hydrogen atom (bound-free absorption), which creates a continuum [[absorption (electromagnetic radiation)|absorption]] at [[wavelength]]s shorter than 364.5 nm.<ref name=mihalas>{{cite journal|bibcode=1967ApJ...149..169M|title=Statistical-Equilibrium Model Atmospheres for Early-Type Stars. I. Hydrogen Continua|journal=Astrophysical Journal|volume=149|pages=169|last1=Mihalas|first1=Dimitri|year=1967|doi=10.1086/149239}}</ref> |
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In some cases the Balmer discontinuity can show continuum [[emission (electromagnetic radiation)|emission]], usually when the Balmer lines themselves are strongly in emission.<ref name=slettebak>{{cite journal|bibcode=1957ZA.....42...67S|title=Classification of Early Type Stars of High Luminosity with Objective Prism Spectra of Low Dispersion. With 7 figures|journal=Zeitschrift für Astrophysik|volume=42|pages=67|last1=Slettebak|first1=A.|last2=Stock|first2=J.|year=1957}}</ref><ref name=knigge>{{cite journal|doi=10.1086/305617|title=Hubble Space Telescope ''Eclipse'' Observations of the Nova‐like Cataclysmic Variable UX Ursae Majoris|journal=The Astrophysical Journal|volume=499|issue=1|pages=414–428|year=1998|last1=Knigge|first1=Christian|last2=Long|first2=Knox S.|last3=Wade|first3=Richard A.|last4=Baptista|first4=Raymundo|last5=Horne|first5=Keith|last6=Hubeny|first6=Ivan|last7=Rutten|first7=Rene G. M.|bibcode=1998ApJ...499..414K|arxiv = astro-ph/9801206 }}</ref> Other hydrogen spectral series also show bound-free absorption and hence a continuum discontinuity, but the Balmer jump in the near [[ultraviolet|UV]] has been the most observed.<ref name=xiao>{{cite journal|doi= 10.1093/mnras/263.1.256|title= Electron temperature determination from nebular continuum emission in planetary nebulae and the importance of temperature fluctuations|journal= Monthly Notices of the Royal Astronomical Society|volume= 263|pages= 256–266|year= 1993|last1= Liu|first1= X.-W.|last2= Danziger|first2= J.|bibcode= 1993MNRAS.263..256L|doi-access= free}}</ref><ref name=scargle>{{cite journal|bibcode=1978ApJ...224..527S|title=Infrared excesses in early-type stars - Gamma Cassiopeiae|journal=Astrophysical Journal|volume=224|pages=527|last1=Scargle|first1=J. D.|last2=Erickson|first2=E. F.|last3=Witteborn|first3=F. C.|last4=Strecker|first4=D. W.|year=1978|doi=10.1086/156400}}</ref> |
In some cases the Balmer discontinuity can show continuum [[emission (electromagnetic radiation)|emission]], usually when the Balmer lines themselves are strongly in emission.<ref name=slettebak>{{cite journal|bibcode=1957ZA.....42...67S|title=Classification of Early Type Stars of High Luminosity with Objective Prism Spectra of Low Dispersion. With 7 figures|journal=Zeitschrift für Astrophysik|volume=42|pages=67|last1=Slettebak|first1=A.|last2=Stock|first2=J.|year=1957}}</ref><ref name=knigge>{{cite journal|doi=10.1086/305617|title=Hubble Space Telescope ''Eclipse'' Observations of the Nova‐like Cataclysmic Variable UX Ursae Majoris|journal=The Astrophysical Journal|volume=499|issue=1|pages=414–428|year=1998|last1=Knigge|first1=Christian|last2=Long|first2=Knox S.|last3=Wade|first3=Richard A.|last4=Baptista|first4=Raymundo|last5=Horne|first5=Keith|last6=Hubeny|first6=Ivan|last7=Rutten|first7=Rene G. M.|bibcode=1998ApJ...499..414K|arxiv = astro-ph/9801206 }}</ref> Other hydrogen spectral series also show bound-free absorption and hence a continuum discontinuity, but the Balmer jump in the near [[ultraviolet|UV]] has been the most observed.<ref name=xiao>{{cite journal|doi= 10.1093/mnras/263.1.256|title= Electron temperature determination from nebular continuum emission in planetary nebulae and the importance of temperature fluctuations|journal= Monthly Notices of the Royal Astronomical Society|volume= 263|pages= 256–266|year= 1993|last1= Liu|first1= X.-W.|last2= Danziger|first2= J.|bibcode= 1993MNRAS.263..256L|doi-access= free}}</ref><ref name=scargle>{{cite journal|bibcode=1978ApJ...224..527S|title=Infrared excesses in early-type stars - Gamma Cassiopeiae|journal=Astrophysical Journal|volume=224|pages=527|last1=Scargle|first1=J. D.|last2=Erickson|first2=E. F.|last3=Witteborn|first3=F. C.|last4=Strecker|first4=D. W.|year=1978|doi=10.1086/156400}}</ref> |
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Revision as of 17:02, 8 June 2021
The Balmer jump, Balmer discontinuity, or Balmer break is the difference of intensity of the stellar continuum spectrum on either side of the limit of the Balmer series of hydrogen, at approximately 364.5 nm. It is caused by electrons being completely ionized directly from the second energy level of a hydrogen atom (bound-free absorption), which creates a continuum absorption at wavelengths shorter than 364.5 nm.[1]
In some cases the Balmer discontinuity can show continuum emission, usually when the Balmer lines themselves are strongly in emission.[2][3] Other hydrogen spectral series also show bound-free absorption and hence a continuum discontinuity, but the Balmer jump in the near UV has been the most observed.[4][5]
The strength of the continuum absorption, and hence the size of the Balmer jump, depends on temperature and density in the region responsible for the absorption. At cooler stellar temperatures, the density most strongly affects the strength of the discontinuity and this can be used to classify stars on the basis of their surface gravity and hence luminosity.[6] This effect is strongest in A class stars, but in hotter stars temperature has a much larger effect on the Balmer jump than surface gravity.[2][7]
References
- ^ Mihalas, Dimitri (1967). "Statistical-Equilibrium Model Atmospheres for Early-Type Stars. I. Hydrogen Continua". Astrophysical Journal. 149: 169. Bibcode:1967ApJ...149..169M. doi:10.1086/149239.
- ^ a b Slettebak, A.; Stock, J. (1957). "Classification of Early Type Stars of High Luminosity with Objective Prism Spectra of Low Dispersion. With 7 figures". Zeitschrift für Astrophysik. 42: 67. Bibcode:1957ZA.....42...67S.
- ^ Knigge, Christian; Long, Knox S.; Wade, Richard A.; Baptista, Raymundo; Horne, Keith; Hubeny, Ivan; Rutten, Rene G. M. (1998). "Hubble Space Telescope Eclipse Observations of the Nova‐like Cataclysmic Variable UX Ursae Majoris". The Astrophysical Journal. 499 (1): 414–428. arXiv:astro-ph/9801206. Bibcode:1998ApJ...499..414K. doi:10.1086/305617.
- ^ Liu, X.-W.; Danziger, J. (1993). "Electron temperature determination from nebular continuum emission in planetary nebulae and the importance of temperature fluctuations". Monthly Notices of the Royal Astronomical Society. 263: 256–266. Bibcode:1993MNRAS.263..256L. doi:10.1093/mnras/263.1.256.
- ^ Scargle, J. D.; Erickson, E. F.; Witteborn, F. C.; Strecker, D. W. (1978). "Infrared excesses in early-type stars - Gamma Cassiopeiae". Astrophysical Journal. 224: 527. Bibcode:1978ApJ...224..527S. doi:10.1086/156400.
- ^ Bessell, Michael S. (2007). "Measuring the Balmer Jump and the Effective Gravity in FGK Stars". Publications of the Astronomical Society of the Pacific. 119 (856): 605–615. arXiv:0706.2739. Bibcode:2007PASP..119..605B. doi:10.1086/519981.
- ^ Crowther, P. A. (1997). "The effective temperatures of hot stars". International Astronomical Union Symposium. 189: 137–146. Bibcode:1997IAUS..189..137C. doi:10.1017/S0074180900116614.