Sent: Wednesday, August 8, 2001 18:20:50 From: email@example.com (richard seymour) here's the poop: decypting all of the abbreviations is a huge task... I have placed ZIP files of much of what became the Autostar's Scrolling Text data about its STARS into my web area. You can fetch it from http://rseymour.home.wolfenet.com/astro/notes.zip Compressed, it's 163Kbytes... expanded it's over a half-megabyte. Each line in the notes file has -three- things before the colon: The HR number a COUNT digit... so that the third VAR line shows 3VAR: the record type (VAR in the above example). Perhaps by seeing a lot of the lines sitting quietly together on one screen, rather than dimly scrolling by in the darkness, some additional feeling of what's there will arise. I can only offer a few example decrypted lines, and hope they lead you to further research on your own. Below, the lines with "**" are from the Autostar. Then the explanation follows. Here goes. ** ALPHERATZ: ADS 94A, 96.6960d, K 30.8k/s, V0 -11.6k/s, asini 34.2. The star is also cataloged in the ADS (A Double Star) list as 94A The period of the orbiting stars is 96.7 days The K, V0 and asini are orbital parameters for the pair. ** Alpha CV 2.02 - 2.06V, 0.9636 or 0.966222d. The star is a Cephid Variable, ranging from 2.02 to 2.06 magnitude, with a period of 0.96 days. ** Companion 9.44V, +0.34(B-V), -0.14(U-B), G5Ve. The star's companion is 9.4 magnitude, with the BV and UB color ratios shown. It's rated as a class G5Ve star. ** Ultraviolet FeII emission The star has a line in its spectrum from the doubly-ionized (II) state of Iron (Fe) ** 6.8 B8V, 7.1 B9V, 1600y, a = 1.260". Combined mag., colors The "star" is really a double with 6.8 and 7.1 magnitude members, Stellar types B8V and B9V (v=variable), orbiting in 1600 years, visual separation 1.26 arc secs. The usual description of the star is a combined apparent total of the brightness and colors of the pair. ** BY Dra, amp. 0.032V, 0.037B, 7.655d The star is a variable, but with different amounts of variation in the colors regions "blue" and "violet", with a period of 7.6 days. (i don't know if this star -is- BY Draco, or a variable of the type exemplified by BY Draco ) ** ADS 455AB, CPM. B, 10.4v K0V. C, 12.3v at 60". Cataloged as ADS number 455AB, CPM is "Common Proper Motion", meaning that the stars are truely (not apparently) moving together through space, so are probably truly interrelated. It's a triple: each star gets a letter, with A being the main star, member B is 10.4 mag, type K0V, member C is 12.3 mag, 60 arc sec away. ** Also classified B2V, B4ne, B8III, B2-5IVe. They haven't agreed on the spectrum-determined type of star that it is, so they list a bunch of classes. ** SB Spectral Binary... they can't see that there are two stars, but the spectrum shifts in a regular manner, so they infer that there are (at least) two there. ------------------------------------------------- > first two stars in the autostar; "Acamar" and "Achener". Good choices... Acamar had "HR 897/8" which tells me that it's entry 897 in the "notes.zip" file. Easy to locate :-) And, indeed, the text from the file: > Binary with HR 898. Uncertain which component var. > Combined mag. HR 897/8, 2.91V; > combined colors, +0.125(B-V), +0.13(U-B). matches the Autostar. HR 898 -- the companion is Harvard Revised entry 898. (this one is 897) The combined magnitude is 2.91 The "V" indicates which "type" of magnitude they're describing. Astronomers have different values for "photographic" versus "visual" magnitudes... and i believe "V" means they're describing the Visual value. (there's also "photoelectric" magnitudes) > I understand the class of the first star (A4III) and thought I > understood the color index of +.125 and +.13 (about that expected > for a class"A" star) I couldn't have said that... i know almost nothing about relating color to star classes (the holes in my background are vast) > but I do not understand the (B-V) and (U-B) following the numbers. The BV and UB are the axes of the plot of the color index. The full term for such measurement is "UBV photometry" The B is the Blue photographic or photoelectric band of the UBV chart (is V "visual" or "violet"? How does Red factor in?)) Those charts are usually plotted with "absolute visual magnitude" on the vertical (y) axis, and "Color Index (B-V)" forms the X-axis. I do not know what "U-B" singifies, but if the color index is B-V (blue minus violet?) then it's whatever "U" is less blue. ahh... (i'm reading the Introduction to the Sky Catalog 2000.0, Volume 2 (Sky Pub and Cambridge Univ Press, 1985)) remember my mumble about "BY Dra" in the other note? There -is- a BY Draconis-type Variable. Young, rapidly rotating, type K or M. > Further, for the second star there is an "EB or E11" in the moving > verbal description and an "amp .02V" which are total mysteries to me. Here Meade only use one line (the "VAR" or variable characteristics line) from the data file. If you search the note.txt file for "Achernar", you'll find it's HR 472. The VAR data line says: EB or Ell, amp. 0.02V. H alpha var. emission and possible high-velocity mass loss. Expanding circumstellar shell. which again matches the Autostar. (which also has clear-text stuff added by Meade) EB: Eclipsing Binary. (explaining the variablility) However, (again from the Sky Catalog) EB is actually a specific -type- of EB, characterized by the light curve's shape. EA is an Algol-type, EB is a Beta Lyrae type, which are gravitationally distorted Ellipsoidal components. "Their light curves vary continuously with amplitudes less than 2 magnitudes"... so there's the "amp". The "Ell" is another type: also gravitationally distorted, but they do *not* eclipse eachother. The orbital motion changes how much star-surface we're seeing, hence the apparent brightness. A further note on the Notes file: Each line starts with a number (the HR entry number), a code, a colon (:) and then the text. The codes before the colon are: C - Colors; D - Double and multiple stars; DYN - Dynamical parallaxes; G - Group membership; M - Miscellaneous. N - Star names; P - Polarization; R - Stellar radii or diameters; RV - Radial and/or rotational velocities; S - Spectra; SB - Spectroscopic binaries; VAR - Variability; Not all stars in the HR listing have a "note" Stars with notes only have those pertinent to that star. have (more) fun --dick (i'm not an astronomer... i'm an engineer...) ----- continuing the abbreviations... THE B-V, U-B are, indeed color indexes. The full suite of letters are R, V, pg, B, and U with R being Red, B the blue visual magnitude, pg the photographic magnitude ( B = pg + 0.11 ) and (for nearby galaxies) V = R +0.3 (there's another set for Infrared.) R is Red (magnitude measured centered at 6800 Angstroms) V is .. yellow (mag meas. centered at 5550 Angstroms) pg is Photographic ... centered at 4300 Ang B is blue (magnitude measured centered at 4350 Angstroms) U is UltraViolet, centered at 3500 Å The color index is C = pg-V = B - V - 0.11 So U - B is the ultraviolet magnitude less the blue visual, and B - V is the Blue less the Yellow. There's a table of ten agreed-upon "standard stars" so that folks can calibrate their measurements, and there are six dwarfs of type A0 which, by convention, are defined as having zero values of B-V and U-B ... when measured above the atmosphere. (i'll wait while you check) There's "apparent magnitude" (which we see), and Absolute magnitude (magnitudes as if measured at a standard distance of ten parsecs) The absolute value is usually M, with a subscript of the color, and the apparent is usually m (lowercase), again with the subscript. Since it's hard for me to do subscripts, i'm using U and u instead. Since i knew you were going to ask, the Sun is: U=5.51 B=5.41 V=4.79 u=-26.06 b=-26.16 v=-26.78 therefore b-v= 0.62 so NOW will you use your Solar Filter? --dick
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