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Investigate about star
MISAO Project Announce Mail (August 3, 2004)
Hello. I am Seiichi Yoshida working on the MISAO project.
You can feel "Oh, I get a new star!?" many times when you see CCD
images. You will find a star not found in your past images. You will
find a star not displayed by the GUIDE. However, please be careful. If
you feel you got a new star, it is often a very popular Mira type
variable star.
Many people is observing faint comets with CCD cameras recently.
However, please be careful. If you find some object at the predicted
position, it is often a faint star at the same position and the comet
is actually invisible.
You can find some interesting stars when you observe stars with a CCD
camera. While observing an eclipsing variable, you can find the
brightness of another star in the frame changes as well. When you
measure the brightness of a comet, you can feel the data of one of the
comparison stars does not correspond to the value in the catalog.
Recently, you can easily obtain various kinds of information using
Internet. When you find a possible new star, when you observe a faint
comet, or when you find an interesting star, please investigate about
the star.
Here introduces how we investigate about a star in the course of the
MISAO Project, in order to know about it in details when we find a
possible new star or an interesting star.
Investigation of a star and utilization of the information can reduce
mistakes in your discoveries or observations. Furthermore, you can
learn various knowledge, and you can enjoy your surveys or
observations much more. Sometime you may get a chance to discover an
important rare object unexpectedly.
The following page illustrates the usage of each web service. Please
visit it.
http://www.aerith.net/misao/guide/research.html
1. Past Images
1-1. DSS (Digitized Sky Survey)
The DSS (Digitized Sky Survey) has been very popular as past images.
It has three sorts of images, Bj-band (blue), R-band (red) and I-band
(infrared) images.
There are some sites which provide the DSS images.
The following page is good for quick look.
The STScI Digitized Sky Survey
http://stdatu.stsci.edu/cgi-bin/dss_form
There are several DSS images of different date for one area. The
following page is good to look all of the images.
ASTRONOMICAL IMAGE ON-LINE ACCESS INTERFACE
http://dss.mtk.nao.ac.jp/
The following page is good to investigate very faint stars nearby the
limiting magnitude in details.
USNO Flagstaff Station Integrated Image and Catalogue Archive Service
http://www.nofs.navy.mil/data/FchPix/cfra.html
1-2. 2MASS (Two Micron All Sky Survey)
The 2MASS (Two Micron All Sky Survey) is infrared images. The images
are available at the following page.
2MASS All Sky Quicklook Image Server
http://irsa.ipac.caltech.edu/applications/2MASS/Visualizer/
1-3. ASAS (All Sky Automated Survey)
The images of the ASAS (All Sky Automated Survey) are available at the
following page.
The All Sky Automated Survey
http://www.astrouw.edu.pl/~gp/asas/asas.html
The feature of the ASAS is that new images have been added day by day.
You can look the very latest images within several days.
However, the area is limited south of Decl. +30 deg. The limiting
magnitude is not so deep.
If you find a new star like a nova, you should investigate the ASAS
images. If the star is also visible in the latest images of the ASAS,
it is surely a real new object. Please report your discovery
immediately.
1-4. Note on CCD Images
Because a CCD camera is strongly sensitive in infrared, please be sure
that a red star like a Mira type variable becomes extremely bright in
CCD images. Therefore, you should investigate the 2MASS images in
order to compare with a CCD image.
If you investigate the DSS images, you have to look the I-band
images. Some people may think that R-band images are OK, but it is not
correct.
Here shows one example. Let's see a star MisV0001, one of the new
variable stars discovered in the MISAO Project.
MisV0001
http://www.aerith.net/misao/data/misv.cgi?1
Please search the DSS R-band images of this star (with a size of 5x5
arcmin), and compare them with the discovery image in the page of
MisV0001. A bright star is visible in the CCD image, however, no
bright star is found in the DSS R-band images.
On the other hand, MisV0001 is properly visible in the 2MASS images.
If you only investigate the DSS R-band images, maybe you believe it as
a nova by mistake.
It is not rare that a 10-mag bright star in the CCD images becomes
fainter than 15 mag in R-band images, and becomes fainter than 20 mag
in Bj-band images. So please be careful.
1-5. Confirm Faint Comets
When you observe a faint comet, you have to confirm whether you really
catch the comet even if you see a faint object at the predicted
position. Especially, the position or brightness can be different from
the prediction when the comet has not been observed for a long time,
Sometimes a faint star exists by chance exactly at the predicted
position of a comet. Even if a object looks diffused, it can be
blending faint stars or a faint galaxy.
The following page introduces the examples that some 2MASS objects
were detected at the predicted position of comets, but actually they
are not comets.
Comets in 2MASS
http://www.aerith.net/astro/2MASS_comet.html
When a comet is too slow to confirm the evident motion, you should
investigate the DSS images.
1-6. Large Proper Motion
When you investigate past images, please take care of stars with large
proper motion. Especially some of the DSS images are very old, taken
in the middle of the 20th century, so the difference of position
becomes very large.
The following page introduces some examples which show how largely the
position of a star with large proper motion becomes different when
comparing recent amateur's CCD images with the DSS images.
Large Proper Motion
http://www.aerith.net/misao/report/general/proper.html
When you investigate past images, please take care of the date of the
images. If a star is not found at the position, please search in the
neighborhood because the star may locate at the different position due
to the proper motion.
If you investigate the USNO-B1.0 data, you can see the stars with
large proper motion.
2. Asteroids
If you find a possible nova or supernova, sometimes an asteroid
locates there by chance.
Sometimes you can take a CCD image by chance just when an asteroid
locates exactly overlapping on a star, then the star looks as if the
brightness changed. In that case, you can report it as a new variable
star by mistake if you do not investigate asteroids.
You can investigate asteroids at the following page.
MPChecker: Minor Planet Checker
http://scully.harvard.edu/~cgi/CheckMP
Please be careful because you cannot investigate planets at this page.
Especially when you are searching novae with a wide field camera lens,
do not discover Uranus or Neptune again. When you are searching faint
stars, take care of Pluto.
You can also investigate comets using the MPChecker. However, the
brightness of comets are not displayed there. Please be careful
because all comets within the search field will be displayed even if
they are extremely faint and invisible.
You can investigate brightness of comets at the following pages.
Comet Catalog in order of Designation (since 1995)
http://www.aerith.net/comet/catalog/index-code.html
Comet Catalog in order of Number of Periodic Comets
http://www.aerith.net/comet/catalog/index-periodic.html
3. Light Curves
You can investigate light curves of stars recorded by the automated
surveys.
Visual observers of comets always worry about the comparison stars,
whether they are variable or not. If you investigate the light curves,
you can be sure the comparison stars are not variable.
When you find a star whose brightness changes on your images, you
should investigate the light curve. It may be an eclipsing variable
which fades out repeatedly every several days, or it may be a Mira
type variable star which repeats brightening and fading every year. It
will be revealed by investigating the light curve. If the light curve
looks unusual, maybe you discover an important rare object.
3-1. ASAS (All Sky Automated Survey)
The ASAS (All Sky Automated Survey) mainly covers the southern sky.
You can investigate the light curves of stars south of Decl. +30 deg
and brighter than 14 mag at the following page.
The All Sky Automated Survey
http://www.astrouw.edu.pl/~gp/asas/asas.html
The ASAS keeps taking new images still now. When a new image is taken,
the new data are immediately added. So you can always investigate the
very latest light curves.
3-2. NSVS (Northern Sky Variability Survey)
The NSVS (Northern Sky Variability Survey) mainly covers the northern
sky.
You can investigate the light curves of stars north of Decl. -38 deg
and brighter than 15.5 mag at the following page. But the light curve
is limited to the period of about one year from 1999 to 2000.
Northern Sky Variability Survey
http://skydot.lanl.gov/nsvs/nsvs.php
4. Star Data
The DSS images or 2MASS images give you rough information. But if you
want to know the accurate value of position or brightness, or if you
want to know more information in details, you should search star
catalogs and investigate the star data.
4-1. USNO-A2.0 / USNO-B1.0
The USNO-A2.0 and USNO-B1.0 catalogs contain stars down to about 20
mag. When you want to investigate star data visible in the DSS images,
you should search these star catalogs.
It is a feature of the USNO-B1.0 catalog that it has information of
proper motion.
The star data in the USNO-A2.0 / USNO-B1.0 catalogs are available at
the following page.
USNO Flagstaff Station Integrated Image and Catalogue Archive Service
http://www.nofs.navy.mil/data/FchPix/cfra.html
4-2. 2MASS
The star data visible in the 2MASS images are available at the
following page.
GATOR
http://irsa.ipac.caltech.edu/applications/Gator/
4-3. Research Catalogs using PIXY System 2
If you have the CD-ROMs of the GSC (Guide Star Catalog) or the
USNO-A2.0 catalogs, you can investigate the star data using the PIXY
System 2 developed in the course of the MISAO Project.
The following page introduces the way to investigate star data using
the PIXY System 2.
Research Catalogs
http://www.aerith.net/misao/pixy/tutorial/catalog.html
4-4. Star Color
A star catalog contains brightness of stars in some bands. Those
brightness data show the star color.
The USNO-A2.0 catalog contains two brightness data, R and B. The
USNO-B1.0 catalog contains four brightness data, B1, B2, R1 and R2.
The 2MASS catalog contains three brightness data, J, H and Ks.
The color of a star is expressed by the difference of brightness in
two different bands. The B-V value, difference of B-band (blue)
brightness and V-band (visual) brightness, is used in standard. If the
B-V value is smaller than 0, it is a blue star. If larger than 1, it
is a red star.
Every star catalog contains the brightness data measured in the
original bands. So it is not clear how blue or red a star is based on
the data. Therefore you should convert the brightness into a standard
color value using a conversion formulas of magnitude systems.
The following page introduces the conversion formulas for various star
catalogs in order to calculate a standard color value.
Color Conversion
http://www.aerith.net/astro/color_conversion.html
When we find a new variable star in the course of the MISAO Project,
we investigate the star color in the USNO-A2.0 catalogs. If a star is
not red, it can be a short periodic variable star. Then we run the
concentrative observations. New eclipsing variable stars like MisV1105
have been discovered in this way, based on the star color.
MisV1105
http://www.aerith.net/misao/data/misv.cgi?1105
5. Research Result
5-1. SIMBAD
You can investigate the results of various researches and observations
in the past.
SIMBAD Astronomical Database
http://simbad.u-strasbg.fr/Simbad
5-2. New Variable Star
When you find a new variable star, you should investigate whether it
has been already discovered by someone or not. If a star has been
already discovered as a variable star, the SIMBAD displays the
variable star name.
Note that a variable star is not displayed if it is not issued in
papers.
5-3. Special Star
While investigating the research results in the past, sometimes you
can find interesting information unexpectedly, which lead to the
discovery of an important rare object.
Here shows one example. Let's see a star MisV1147, one of the new
variable stars discovered in the MISAO Project.
MisV1147
http://www.aerith.net/misao/data/misv.cgi?1147
Please search about this star using the SIMBAD, and you will find it
has a name HBHA 65-53. If you investigate furthermore about this name,
you will find that this star has been studied in the past, in the
research of stars with strong H-alpha emission line.
Based on this information, MisV1147 became to be observed by many
people. Then it was revealed as a young stellar object, in addition,
very special object among them.
P.S.
The past MISAO project announce mails are available at:
http://www.aerith.net/misao/
--
Seiichi Yoshida
comet@aerith.net
http://www.aerith.net/