star magnitude anomaly
paul Jul 22, 2003
I saw an apparent star magnitude anomaly
last night. Guide seems correct from what I can
tell based on catalogues, BUT the older SAO vM for
this star seems much more accurate (thru my telescope)
than the newer data: +8.84 (variable) versus +7.07
would someone more knowledgeable about vM please
explain this. I mention it because I have never seen
such a noticeable difference. it seemed brighter than
the variability mentioned. it appeared brighter than
the +7.4 at 22 arcmin PA104. I was estimating +7 then
found that was the SAO value.
Comments from the Hipparcos Catalog (from Guide):
Hipparcos #95413
Click here for SIMBAD data
RA (J2000.0): 19 24 33.07
declination +50 14 29.3
(Above is the computed position for J1991.25)
magnitude in Johnson V: 8.84
Magnitude varies by more than .6 magnitudes
Magnitude derived from Hipparcos data
Trigonometric parallax 3.73 ± 0.85 milliarcseconds
Proper motion in RA: -6.77 ± 0.92 milliarcseconds/year
Proper motion in dec: -19.75 ± 1.14 milliarcseconds/year
Mean BT magnitude: 10.530 ± 0.038
Mean VT magnitude: 8.980 ± 0.018
Johnson B-V colour: 1.323 ± 0.035
Johnson B-V source is Tycho-based observations
Color index (V-I) in Cousins' system: 4.57 ± 0.06
Median magnitude in Hipparcos system (Hpmag): 7.9551 ± 0.0222
Scatter on Hpmag is 0.186 magnitudes
Hpmag is based on 84 observations
Hpmag at maximum (5th percentile): 7.47
Hpmag at minimum (95th percentile): 8.25
Unsolved variable which does not fall in the other categories
BD +49 2999
Spectral type M7IIIvar
Spectral type is from miscellaneous sources
Data inferred from the Hipparcos catalog:
Distance: 268 ± 61 parsecs (870 ± 200 light-years)
Luminosity: 17.4 ± 7.9 times that of the sun
Absolute magnitude: 1.70 ± 0.49
J2000 position at current date (proper motion included):
Right ascension: 19h24.551092
Declination: +50.241405086 deg
(Above is ±11.3 milliarcseconds in RA, ±14.0 milliarcseconds in dec)
J2000 position at current date (proper motion and parallax included):
Right ascension: 19h24.551091
Declination: +50.241406067 deg
Comments from the Hipparcos Variability Annex:
Spectral type: M7IIIvar
Unsolved variable which does not fall in the other categories
Variable was newly classified by Hipparcos
Magnitude at maximum from curve fitting: 7.473
Magnitude at minimum from curve fitting: 8.249
Data from the Tycho catalog:
Johnson V magnitude: 8.777 ± 0.024
Parallax 4 ± 1 milliarcseconds
Comments from the GSC:
GSC identifier 3551 2505
RA declination posn err magnitude type
Exposure start Exp. Length Obs. ID Filter
19h24.551320m +50.241530 deg 0.1" 7.50±1.25 star
(Data comes from Tycho Input Catalog)
Comments from the PPM catalog:
PPM 37375
Magnitude: 8.1
J2000 RA: 19h 24m 33.111s
J2000 dec: +50 14' 29.62"
Proper motion in RA: 0.0000 RA seconds/year
Proper motion in dec: -0.010 arcseconds/year
J2000 position at epoch:
Right ascension: 19h24.551850m
Declination: +50.241551 deg
Mean position at current epoch:
Right ascension: 19h24.645221m
Declination: +50.248688 deg
Apparent position at current epoch:
Right ascension: 19h24.670104m
Declination: +50.248033 deg
(Above is ±254.4 milliarcseconds in RA, ±286.4 milliarcseconds in dec)
Spectral type M5
DM +49 2999
AGK +50 1370
Comments from the SAO catalog:
SAO 31632
Magnitude: 7.07
Spectral type MB
DM +49 2999
Right ascension: 19h24.550499m
Declination: +50.241354 deg
Proper motion in RA: -0.008 arcseconds/year
Proper motion in dec: -0.014 arcseconds/year
Proper motion total: 0.016 arcseconds/year
Comments from the HD catalog:
HD 182917
BD +49 2999
Visual magnitude 7.07
Photographic magnitude 8.42
Spectral type Mb
Comments from the GCVS:
Right ascension: 19h24.5510m
Declination: +50.2416 deg
Cause(s) of variability:
Z Andromeda type
Semiregular long-period type
Click here for SIMBAD data
Photometric band: V
Maximum magnitude: 5.60
Minimum magnitude: 8.49
Spectral type: M7IIIab+Be
References: 08849 00002
AAVSO designation 1921+50 ; available charts are:
q scale chart, made 3/91; field of view is 8 degrees