Tải bản đầy đủ - 0trang
Table 866. Bright or Well-Observed Novae
T A B L E 866A.-MASS
T h e mass-luminosity relation is shown in figure 33, which is based on data by G. P.
Kuiper.'" Dots and open circles represent visual and spectroscopic binaries, each component being shown separately. Crosses represent several visual binaries in the cluster of
the Hyades. Squares represent the white dwarfs. T h e symbol 0 stands for the sun.
Prepared by 0. Struve, University of California, Berkeley.
zm Astrophys. Journ., vol. 88, p. 472, 1938.
mass luminosity relation for stars.
T A B L E 867.-CLASSIFlCATlON
I Galactic nebulae-
A Planetaries . . . . . . . . . . . . . . . . . .
B Diffuse ......................
(1) Predqfninantly luminous.
(3) Conspicuously mixed . . .
( a ) Normal spirals . . . . .
(1) Early . . . . . . . . .
(2) Intermediate . . .
(3) Late ..........
(b) Barred spirals . . . . .
(1) Early . . . . . . . . .
(2) Intermediate . . .
(3) Late . . . . . . . . . .
B Irregular ....................
Extragalactic nebulae too faint to be classified, "Q"
SMITHSONIAN PHYSICAL TABLES
e . 8.
T A B L E 868.-STELLAR
Radiometric magnitude of any star = visual (or photographic) magnitude of a spectral
class A" star giving the same radiometric deflection. If v i r , n t p l . , and ltzpg are, respectively,
radiometric, photovisual, and photographic magnitude, then Color Index, C I = (?itprT M ~ , ;~ )heat index, HI,, = i i i p l i - iiz, ; HI,, = w i P g - m,. Spectral class : Henry Draper,
revised by 1). Holteit ( D H ) ; by W . W. Morgan ( W W M ) . All measures reduced to
zenith at Mount Wilson ; two reflections from fresh silver ; zinc-antimony black thermojunction; rock salt window. Stars of known or suspected variability are rejected from
All the stars were in both the Mount Wilson and Harvard observing programs.%
The reduction of the Mount Wilson and Harvard data to a common basis has been
rather difficult. The following are the principal factors that differ between the Mount
Wilson and Harvard observations.
(1) The Atmosphere.-There was more water vapor over Oak Ridge than Mount Wilson ; hence, early-type stars would be too faint at Oak Ridge.
(2) The thermocouple blacking.-Probably the surfaces were equally "black" in the
ultraviolet and visible regions ; the Harvard surfaces were blacker in the infrared;
hence, late-type stars would be too faint at Mount Wilson.
(3) The cell window.-Rock salt was used at Mount Wilson; fluorite was used at H a r vard. These are equally good throughout the ultraviolet, visible, and infrared to
the region of 6 to 8 microns. For longer wavelengths, rock salt is better. The effect
of this differelice is in the opposite direction to the thermocouple blacking in (2)
above. However, the very small percentage of stellar energy beyond 8 microns and
absorption bands in the earth's atmosphere means that the difference in the cell
windows has a very much smaller effect than the thermocouple blacking and, therefore, (2) above dominates.
A systematic difference exists between the Mount Wilson and Harvard observations
which follows a pattern predicted in accordance with factors (1) and (2) above. Therefore, corrections which are usually less than 0.1 magnitudes have been applied. T h e largest,
0.16 magnitudes, is for 51 Gem. This correction brings the two sets of data into better
agreement but there remains an apparent difference in zero-point of about 0.13 magnitudes.
Since it is impossible to determine which of these two sets of observations is in error, the
mean of the Mount Wilscn and Harvard data has been taken, corrected as indicated for
factors (1) and (2) above. These mean values are the data given in the m, column.
Spectr al class
. .. .
. . ..
.. . .
. . ..
, . ..
* P r e p a re d Iiy I<. M . Emherson, Research a n d Development B o a rd, Washington, D . C .
*M P e t t i t a n d Nicholson, Astrophys. Journ., vol. 56, p. 295, 1 9 2 2 ; vol. 68, p. 279, 1928; vol. 78, p. 320, 1933.
S t e r n a n d Emherson, i\strophys. J o u rn . , vol. 94, p. 412, 1941.
T A B L E 869.-NONGALACTIC
Some 400 considered. Distribution of magnitudes appears uniform throughout sequence.
For each stage in the sequence the total magnitude ( M T ) is related to the max diameter
( d ) by the formula: M T = C-5 log d. When minor diameter is used, C approx constant
throughout sequence ( C = 10.1). Mean absolute visual magnitude -15.2. The statistical
expression for distance in parsecs is log I1 = 4.04 0.2 M T . Masses appear to be of the
order of 2.6 X 10" X our sun's. Apparently nebulae as far as measured are distributed
uniformly in space, one to 10" parsecs3 or 1.5 x lo-'' in cgs units.
Corresponding radius of curvature of the finite universe of general relativity is of order
of 2.7 X 10" parsecs, about 600 times the distance at which normal nebulae can be detected
with the Mount Wilson ]@-inch reflector.
SMITHSONIAN PHYSICAL TABLES
T A B L E 870.-VARIABLE
STARS, G E N E R A L C H A R A C T E R I S T I C S
T h e task of cataloging and naming variable stars was delegated in 1946 by the lnternational Astronomical Union to the Sternberg Astronomical Institute i n Moscow. T h e
1948 General Catalogue lists 10,912 variable stars ; a supplement lists 265 additional variables discovered in 1948. Several thousands of variable stars in glohular clusters, in the
Magellanic Clouds, and in the nearest galaxies a r e not included in this catalog, nor a r e
thousands of stars whose variability has been announced, hut which a r e not officially
recognized pending confirmation. T h e total number of variable-star discoveries announced
until 1950 probably amount to 20,000.
stars, with the exception of eclipsing binaries (see Tahle
879), can he divided roughly into three major groups: (1) Piilsating sfars. T h e variables
of this group a r e all giants, located above the main sequence in the Russell diagram.
(2) Explosive stars. T h e variables of this group are, as f a r a s is known, dwarfish;
located below the main sequence in the Russell diagram. (3) Erratic variables, whose
light, fluctuations, mostly of an erratic nature, a r e produced by external causes (nebulosity)
or by peculiar phenomena in their atmospheres.
P u l s a t i n g stars.-CCcphcids.
Usually- divided into cluster-type variables, with periods
shorter than one day, and classical Cepheids, with periods longer than one day, although
at least five subgroups are indicated.
Cluster-type variables belong t o Population 11, have spectra ranging from A to I;,
absolute magnitudes close t o zero : most variables found in qlohular clusters belong to
this group. Periods range from Od.061 ( C Y Aquarii) to l'l.35 ( a star in the w Centauri
cluster), with the greatest concentration around 01.53. Typical variable : R R Lyrae (7".1
- 8".0 ; period O"S7 ; spectrum .4 2 - F O)., About 1,700 galactic objects and 600 stars in
globular clusters a r e known to belong to thls group.
Classical Cepheids belong t o Population I, have spectra ranging from F to K , with
marked dependence on period, and intrinsic luminosities increasing with the period (periodto -3M (ahsolute visual magnitudes). Periods range from
luminosity law) from -0".5
ld.13 ( B Q Coronae Austrinae) to 45".2 (SV Vulpeculae), with the greatest concentration
around 2'.7. Typical variable : 6 Cephei (3".8 - 4".6, period S'I.37, spectrum F 5 - G 2).
About 500 galactic stars and 2,500 stars in the Magellanic Clouds and other extragalactic
systems a r e known to belong to this group.
For both cluster-type and classical Cepheids the shape of the light curve is a function
of the period; the rise to maximum is always faster than the decline. Avcrage visual amplitude 0".75 ; photographic amplitudes 50 percent larger. Radial-velocity curves a r e in
phase with light curves (maximum approach at maximum light) ; Average amplitude
Long-period varia6lcs. Typical variable : o ( M i r a ) Ceti ( P . 0 - 10"l.l : period, 331";
spectrum J 4 6 c ) . Characterized by very large amplitudes (from 4 to 10 magnitudes, visual),
S,X,N ) with bright hydrogen emission lines near maximum light, unlate spectra ( M ,
stable light curves and periods ranging from 120" ( W Puppis) t o 1379' (BX Monocerotis).
Greatest concentration of periods around 275". Long-period variables seem to fall into
two major groups, whose periods overlap to a great extent. Stars of the first group have
nearly symmetrical light curves with moderate amplitudes and periods ranging from 120"
to 450"; they seem to belong to Population 11. Stars of the second group have strongly
asymmetrical light curve (rise faster than decline), large amplitudes and periods upward
of ZOOd; they seem t o belong to Population 1.
T h e enormous visual (and photographic) amplitudes a r e accounted for by a shift in the
effective wavelength of the radiation with phase and by the formation of strong absorption
hands at minimum light in the visilal region of the spectrum. T h e total (bolometric)
radiation has an amplitude of only one magnitude. Absolute bolometric magnitudes near
-4. About 2,600 stars are known to belong to this group.
Scnzivcyrlar rcd variahlrs. Typical variables : Af Cygni (6m.3- 8"I.O ; period 89' ;
spectrum M 6). Spectra similar tc. those of long-period variables, except for much weaker,
o r entirely absent, hydrogen emission lines. Amplitude mostly comprised between 1 and 3
magnitudes (both visual and photographic). Light curves very irregular, often erratic ;
periods ranging from 42d ( T X Tauri) t o 810" (S Persei), hut mostly comprised between
100' and 200"; several unrelated periods often occur in the same star and for many variables periods have only a statistical significance. Then mean brightness often changes
slowly, with cycles of 1,000-2,000 days. Absolute visual magnitudes high, between 0 and
Their galactic distribution suggests Population 11. Total number of recognized
RV Tazrri sfars. Typical variable: RV Tauri ( P . 7 - 11"'.8; period 39'.3; spectrum
K I V ) . Spectra Cepheid-like, hut light curves similar to those of the preceding group.
Deep and shallow minima often alternate. Periods (intervals between two successive
Prepared Iiy 1.. Tacchia Massachusetts Institute of Technoloxy.
288 Kukarkin. B. V.. and 'Parenago. P. P.. Fiziceskie Peremennye Zvjozdy, 1937; Gaposchkin, C. P.,
a n d Gaposchkin, S., Vnriahle stars, 1938; Campbell, I.., and Jacchia, I.., T h e story of variable stars, 1941.
SMITHMNIAN PHYSICAL TABLES
T A B L E 870,VARIABLE
STARS, G E N E R A L C H A R A C T E R I S T I C S (concluded)
minima, irrespective of principal and secondary) range from 16‘S (SX Centauri) to 73’
(R. Scuti). Galactic distribution suggests Population I. Only 60 stars can be safely
assigned to this group.
Gentiiiorzim stars. Typical variable : U Geminorum (8”.8 E x p l o s i v e stars.--li
14”.0 ; average cycle 97‘). Characterized by long permanence at minimum light, interrupted
by brief, sudden explosions which bring the star almost always t o the same maximum magnitude; the time between explosions might vary as from 1 to 4 for an individual star, but
the average length of cycles over long periods of time are constant for each star. Average
cycle length ranges from 13” ( A B Draconis) to 340’ ( A W Geminorum). A few stars
undergo temporary spells of continuous, irregular fluctuations. The amplitude increases
from 3 magnitudes for short-cycle stars to 5 magnitudes for long-cycle stars. Spectra are
of early type and peculiar ; hydrogen lines in emission at minimum in absorption a t mnximum galactic concentration low for short-cycle variables, greater for long-cycle ones.
Group numbers about 70 stars.
2 Camelopardalis stars. Typical variable : 2 Camelopardalis (10”’.5 - 13“.3 ; average
cycle 22”.1). Similar to the preceding, but with shorter minima and smaller amplitudes;
erratic variation is the rule rather than the exception : Less than a dozen stars are known
of this type.
Novae, repeating novae, and novaelike stars. Novae a r e stars that suddenly blaze up
with startling rapidity and then gradually fade out again. For data on bright or wellobserved novae see Table 866. A repeating (or recurrent) nova, such as T Pyx, has
several outbursts, any one of which would have identified it as a nova. A novalike star,
e.g., 2 Andromeda, from time to time shows novalike characteristics with the formation
of a shell spectrum and displaced absorption lines and later emission lines. Nebular lines
are often associated with these objects.
E r r a t i c variables.-R
Coronae Borealis stars. Supergiants with G and R spectra and
an abnormal abundance of carbon i n their atmospheres. For long periods of time (often
years) the light remains constant at maximum. At entirely irregular intervals the light
is dimmed, probably by a carbon veil, with resulting fluctuations which may reach 9 or 10
magnitudes. Typical stars : R Coronae Borealis (variable from 5”.8 to lSm.O), RY Sagittarii (variable from S”I.9 to 15”’.0 and probably fainter). Only 23 stars are known to
belong to this type.
Variables assorintrd z&th nchulosities. Stars in gaseous nebulae of the diffuse or of the
cometary type, or even in dark nebulae, often show erratic variations with various amplitudes and speeds. At least three subtypes are indicated, typified by the following stars:
T Orionis (9“’.6 - 11”.9 ; rapid ; often constant at maximum) ; R Monocerotis (10”’- 14” :
slow) ; R W Aurigae (9”I.O - 13”’.5; very rapid, no constant light at any time). About 200
stars can be attributed to one or the other of these groups.
P Cyg~iiand Be Stars. These early-type giants are normally quiescent, but occasionally
some of them undergo slow fluctuations of moderate amplitude (1” - 4“) which last over
a series of years. Typical : P Cygni (3”’ - 6”), active in the 17th century ; 7 Cassiopeiae
(lm.6- 3”.0), active after 1936.
T A B L E 871.-VISUAL
A. Visual binary stars are cafaloqrd as follows:
1. “New General Catalog of Double Stars within 120” of the North Pole” (abbreviated: A D S = Aitken Double Stars), by R. G. Aitken, Carnegie Inst. Washington Publ. 417, 1932 (2 vols.) ; contains 17,180 objects.
2. ADS is the successor to BIIS= “A General Catalog of Double Stars within
121” of the North Pole,” by S. W. Burnham, Carnegie Inst. Washington Publ.
5, 1906 (2 vols.) ; this catalog contains 13,665 pairs. About one-third of these
(mostly wide objects) are not repeated in A D S .
3. SD.S or “Southern Double Star CataloQ,” from -19” to -90” declination, by
R. T . A. Innes, B. H. Dawson, and W. H. van den Bos, Union Observatory,
Johannesburg, South Africa, 1927 (4 vols.).
4. Many zctidc double stars of interest are contained in “Measures of Proper Motion
Stars,” by S. W. Burnham, Carnegie Inst. Washington Publ. 168, 1913.
B. A full discussion of niass dctcrmbiations of visual binary stars is found in “The
Masses of the Stars with a General Catalog of Dynamical Parallaxes,” by H. N.
Russell and C. E. Moore, Univ. Chicago Press, 1940.
C. OrOits of visual binaries are listed in W. H. Finsen, “Second Catalog of Orbits of
Visual Binary Stars,” Union Obs. Circ. 100, 1938. Supplementary orbits are found
in later Union Observatory Circulars and in the Astronomical Journal.
Prepared hy G . P. Kuiper. Yerkes Observatory.
SMITHSONIAN PHYSICAL TABLES