Unusual Stars in Landolt Standard Stars

Japanese version
Home page
Updated on May 11, 2003


Photometric observations, stars in:

UBVRI Photometric Standard Stars, Celestial Equator
Astronomical Data Center catalog No. 2118


are commonly used as reference.

This catalog name says "standard stars", which suggests only "standard" stars are listed up in this catalog. However, investigating the contents revealed that many unusual stars are also listed up.

I found two stars in large nebula.

o BD -12 134

00h47m04s -11o52'38"

This star is in a large planetary nebula NGC 246, about 4 arcmin size.

Here is the RGB composite image from DSS I, R and Bj images.

The nebula is very blue, so it may be invisible on CCD images.

o HD 46056

06h31m21s +04o50'18"

This star is also listed up in the Galactic O Stars, a catalog of blue stars, as CGO 128. It wears a large diffuse nebula, about 6 arcmin size, around the star.

Here is the RGB composite image from DSS I, R and Bj images.

In addition to those stars, I found many other unusual stars.

There are many near-by stars from the Sun. Especially, there are many white dwarfs whose U-B color is so blue as around -1 mag. The two stars with nebulae mentioned above, BD -12 134 and HD 46056, are also so blue.

There are many variable stars, too. Here is the list of variable stars with 0.2 mag or more amplitude (and with uncertain amplitude). There are much more variable stars with 0.2 mag or less amplitude in the catalog.

Landolt NameR.A.Decl.Variable Star NameAmplitude
SA 110 35318h42m17s+00o09'19"HK Aql2.0
SA 99 607h53m34s-00o49'34"NSV 37920.8
HD 6082607h36m29s+02o04'20"BE CMi0.5
HD 17363718h46m39s-07o55'56"V455 Sct0.32
HD 5788407h23m07s-04o13'16"V758 Mon0.29
HD 19163920h11m11s-08o50'28"BE Cap0.27
SA 104 30612h41m04s-00o37'11"KR Vir0.26
HD 4776106h40m01s-04o41'52"V733 Mon0.22
HD 1198301h57m32s-07o31'49"IRAS 01550-0746(24%)
HD 7909709h11m51s-06o58'28"IRAS 09093-0646(19%)
HD 19657320h38m17s+01o00'51"IRAS 20356+0050(14%)
BD -11 16200h52m15s-10o39'56"NSV 15190?
BD +05 246811h15m32s+04o57'25"NSV 18709?
HD 14085015h45m58s-01o26'36"NSV 20394?
HD 18893419h57m38s+00o14'18"NSV 24946?

I found that some of them are non-red variable stars.

HD 1736370.320.236
HD 1916390.27-0.087
HD 477610.220.159
BD -11 162?-0.081
BD +05 2468?-0.116

When observing a celestial object and measuring the brightness, stars in the UBVRI Photometric Standard Stars, Celestial Equator are often selected for the base magnitude.

However, there are many kinds of objects contained in this catalog. Please be careful when you select comparison stars from this catalog.

The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166.

The DSS images are obtained at the Astronomical Image On-line Access Interface (http://dss.mtk.nao.ac.jp/).


Copyright(C) Seiichi Yoshida (comet@aerith.net). All rights reserved.