20:
29:
23:
K line spectrum of KW 326, a dwarf star in the
Praesepe open cluster. The line is very wide and very deep, and it originates in the photosphere, just like any other absorption line. Several other lines are superimposed on it. In the center, the emission due to the K line itself, which takes place in
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The main interest of the Wilson–Bappu effect is in its use for determining the distance of stars too remote for direct measurements. It can be studied using nearby stars, for which independent distance measurements are possible, and it can be expressed in a simple analytical form. In other words,
242:
In 1977, Stencel published a spectroscopic survey that showed that the wing emission features seen in the broad wings of the K line among higher luminosity late type stars, share a correlation of line width and
316:
207:
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in distant stars is very challenging, requires long observations at big telescopes. Sometimes the emission feature in the core of the K line is affected by the
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is defined as the difference in wavelength between the points on either side of the emission at an average intensity between the K1 minimum and the K2 maximum
492:
236:
235:, and since the radiation at this wavelength does not reach the Earth's surface it can only be observed with satellites such as the
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The data error, however, is quite large: about 0.5 mag, rendering the effect too imprecise to significantly improve the
408:
Cassatella, A.; Altamore, A.; Badiali, M.; Cardini, D. (2001). "On the Wilson-Bappu relationship in the Mg II k line".
355:
410:
81:
77:
57:
151:
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Pace, G.; Pasquini, L.; Ortolani, S. (2003). "The Wilson-Bappu Effect, A tool to determine stellar distances".
88:
type M. The greater the emission band, the brighter the star, which is correlated with distance empirically.
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reported on the remarkable correlation between the measured width of the aforementioned emission line and the
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The Wilson–Bappu effect is also valid for the Mg II k line. However, the Mg II k line is at 2796.34 Å in the
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131:
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266:"H and K Emission in Late-Type Stars: Dependence of Line Width on Luminosity and Related Topics"
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of a star. The distance of a star follows immediately from the knowledge of both absolute and
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472:
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According to the latest calibration, the relation between absolute visual magnitude (M
486:
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312:"The CaII-M_v Correlation (Wilson-Bappu Effect) Calibrated by HIPPARCOS Parallaxes"
49:
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and the analytical form expressing the Wilson–Bappu effect, we can determine the
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parallaxes was made in 1999 by
Wallerstein et al. A later work also used W
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369:
72:. The correlation is independent of spectral type and is applicable to
19:
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The first calibration of the Wilson–Bappu effect using distance from
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463:
Stencel, R. E. (2009). "The Wilson-Bappu Effect - 50 Years Later".
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216:. Another limitation comes from the fact that the measurement of W
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18:
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the Wilson–Bappu effect can be calibrated with stars within 100
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from the Sun. The width of the emission core of the K line (
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130:measurements on high-resolution spectra taken with
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103:) can be measured in distant stars, so, knowing W
119:of the star is either negligible or well known.
224:. In these cases an accurate measurement of W
8:
310:; Machado-Pelaez, L.; Gonzalez, G. (1999).
202:{\displaystyle M_{V}=33.2-18.0\log(W_{0})}
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145:, transformed in km/s, is the following:
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16:Correlation among statistics of a star
44:in cool stars is among the strongest
7:
247:similar to the Wilson–Bappu effect.
237:International Ultraviolet Explorer
14:
264:Wilson O.C.; Bappu, V. (1957).
141:) expressed in magnitudes and W
48:which originates in the star's
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183:
1:
356:Astronomy & Astrophysics
32:Zoom on the emission core. W
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442:10.1051/0004-6361:20010816
411:Astronomy and Astrophysics
387:10.1051/0004-6361:20030163
493:Astronomical spectroscopy
62:absolute visual magnitude
134:, but a smaller sample.
68:. This is known as the
434:2001A&A...374.1085C
379:2003A&A...401..997P
222:interstellar extinction
214:cosmic distance ladder
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117:interstellar reddening
74:stellar classification
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25:
465:ASP Conference Series
271:Astrophysical Journal
204:
31:
22:
152:
115:, provided that the
76:main sequence types
473:2009ASPC..412..251S
330:1999PASP..111..335W
284:1957ApJ...125..661W
70:Wilson–Bappu effect
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113:apparent magnitude
109:absolute magnitude
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26:
228:is not possible.
58:M. K. Vainu Bappu
24:the chromosphere.
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425:astro-ph/0106070
418:(3): 1085–1091.
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363:(3): 997–1008.
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308:Wallerstein, G.
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54:Olin C. Wilson
46:emission lines
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324:(757): 335.
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52:. In 1957,
50:chromosphere
42:Ca II K line
39:
233:ultraviolet
251:References
181:
172:−
124:Hipparcos
86:Red giant
487:Category
450:16286422
395:17029463
469:Bibcode
467:: 251.
430:Bibcode
375:Bibcode
326:Bibcode
280:Bibcode
278:: 661.
94:parsecs
64:of the
448:
393:
84:, and
446:S2CID
420:arXiv
391:S2CID
365:arXiv
175:18.0
169:33.2
66:star
56:and
40:The
438:doi
416:374
383:doi
361:401
334:doi
322:111
288:doi
276:125
178:log
132:CCD
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245:v
243:M
226:0
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192:0
188:W
184:(
166:=
161:V
157:M
143:0
139:v
128:0
105:0
100:0
98:W
82:K
78:G
34:0
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