What's New? is a web page that records changes to
the various
AXA web pages.
Note: '
symbol indicates AXA
fit value, not the "official"
value
To see
the light curve
plots for
an exoplanet,
click on the exoplanet's
name
(if it shows a link).
To download an
ephemeris spreadsheet
(Excel)
that shows
transit times
for all the BTEs
for an observer's
site coordinates,
click here: BTE Ephem.
Abstract for the AXA Web Pages - An Early Version
This web page is a "public domain" archive for
amateur observations of known "bright transiting
exoplanets"
(BTE), where "bright"
means V-mag < 14.
My intent is
to "preserve" amateur observations
at one convenient
location and to
promote
sharing exoplanet
observations
by many observers
to help in the search
for anomalies that
might lead to a greater
understanding of
exoplanet systems. Some
light curves (LCs)
are of transits and
others are out-of-transit
(OOT). The
archive manager
will enhance the LC by correcting
for temporal
trends and air mass curvature
using the non-transit
portion of data.
A line-segment
fit will be superimposed
on the LC measurements.
Each LC will be accompanied
by a listing of
mid-transit time,
transit length, transit
depth and an indication
of whether the transit
was early or late.
A web page is devoted to each
exoplanet, with the most
recent LCs at the top. Observers
of TransitSearch candidates
are welcome to submit
observations. It's
OK that most of them will
be featureless; this is useful
information. A web page is
devoted to LCs for TransitSearch
candidates. Most
of the data on the AXA will be transferred
to the Caltech NStED
archive in January, 2009, where it
will be available for download and
viewing a few months later. The fate
of this web page will depend
on how many of the AXA features are present
at the NStED/AXA (I wrote that before
learning about the Czech ETD).
Links Internal
to this Web Page:
Original Purpose
for this Archive
Observation
Submission Format
Sampe
of Archive
Processed
Product
Explosive
Growth of Exoplanet
Discoveries
Patterns to
Look For
Observing
Philosophy
Aperture vs.
Technique
Filter Choice
Defocusing
Comment on
Correcting
LCs for Slope and
Curvature
Practice
Images
Ground
Rules for Professional
Use of
Data Files
Future of AXA
Contributors
AXA Submission
Statistics
Software Used
Statistics
Related Links
Original Purpose for this Archive
This archive was created in 2007 becasuse at that time amateurs had no
place to submit
their
observations of exoplanet
transits
where they would be preserved
for posterity. Since it is scientifically
important to
preserve a historical
record of transit
light curves (LCs),
and since LCs that
are only present at an individual
observer's web
page are unlikely to
be preserved for later
use, there was an unmet
need for an archive of amateur
LCs that presented them in
a uniform format. Such an archive
would grow in value and could
become a useful resource many
years in the future. Only a handfull
of amateurs are associated
with a professional
group of astronomers, where
archives are preserved,
and their LC archive s are
not in the public domain.
The AXA was opened for anyone to submit
observations that were likely
to be added to the AXA web pages
and maintained as a historical
archive. In 2009 I discovered that the Czech Republic Astronomical Society
had been downloading data files from the AXA and fitting their own LC models
for display, and that they also were inviting amateurs to submit raw data
files to their web site. This web site was called the Exoplanet Transit Database,
and since it was maintained by an institution instead of an individual it
was a more suitable place for safely archiving data. I therefore discontinued
accepting data files in December, 2009, and I encourage all amateurs to
submit their data to the ETD. Occasionally I will accept data for special
observing projects, so the remainder of the material on this AXA home page
will be preserved.
The structure of the present archive allows for easy browsing for the purpose of visually searching for patterns that would otherwise be difficult to detect. I anticipate that professional astronomers with their own archive (not in the public domain) will glean information from this one as they search for patterns that can only be done with large amounts of LC data. In this way amateurs with good observing skills can contribute to the professional astronomy community's growing understanding of exoplanet systems, and possibly produce interest in anomalies that could lead to the discovery of additional exoplanets in the same exo-planetary system.
This web page describes how anyone who has observed an exoplanet, and produced a light curve (LC), can submit their observations and have them added to the archive. As the archive manager I will assess the quality of the data and if it looks acceptable (99% of submissions are acceptable) I will proceed to process it. Baseline systematics will be assessed and a fit to the data using a line-segment transit model will be over-plotted on the measured data points. The resulting LC plot will list mid-transit time, transit depth and transit length. Measured mid-transit time will be compared with an ephemeris predicted time. A notation may be made on the LC plot showing 2-minute RMS of the individual measurements.
When many transits are present on a web page devoted to an exoplanet, and ordered with the most recent LC at the top, it is easy to notice the following patterns: transists occuring early or late (implying a need for refining the orbital period), depths varying in a systematic way with filter (related to star spectral type and center miss distance) and transit length varying over time. Some of these patterns can be used by anyone to search for other exoplanets using mid-transit timing anomalies, called "transit timing variations" (TTV). Other patterns may justify a reconsideration of stellar limb darkening and center miss distance. A search for another exoplanet in the same system can also be performed using the OOT data that might contain small depth features that repeat with a different period than the main transits. Many archives exist with exoplanet transit information, but none are in the public domain, and perhaps none are structured in a way that is convenient to use for the purposes just mentioned. This web page is meant for those who are not associated with professional teams that maintain a "secret" archive.
This section used to include instructions for preparing a data file for
submission to the
AXA, but it has been moved
to a separate web
page: DataFormat.
I'll simply
show an example of a properly
formatted data file and refer
you to the above link for explanations.
Sample data
submission showing
required
format.
Here's an example of my preferred filename convention: 20080301-gj436-GJL.txt.
It conveys
the information
that the observations
began
on the date 2008
March 1 (UT), the object
was GJ 436,
and the observer's 3-letter
"observer code" is GJL
(details on the other web
page). Attach this file to
an e-mail sent to:
a
x a @
b r u c e g a r y . n e t
[remove
spaces
between characters]
Sample
of Archive Processed
Product
Two light curve formats will be presented for each data submission (starting
May 1). There
will be a top panel
LC, a bottom panel
LC, and a 4-row information
section between
the panels. In
the following
example the top
panel is a version of
the data with the two principal
systematic
errors removed (temporal
trend and air mass curvature).
This is the format
used by professional
astronomers.
Since amateurs have larger
systematic errors
I have included the lower
panel to show the same
data before removal of
these systematic errors.
The lower panel
also shows a air mass and
"loss" plots (described below).
For this example we can readily
see that the early data were
made at very high air mass, which
explains the greater noisiness
of the data and extreme
air mass curvature.
The middle section states that the transiting object is XO-1, using a
R-band filter, and mid-transit occurred on March 14, 2006 UT. The 7-segment
model fit (explained in detail at model) has a mid-transit
HJD of 2453808.9165
±
0.0010. This corresponds
to UT = 9.946
± 0.015 (based
on the date and source
coordinates).
The ephemeris predicted
HJD and UT are also
shown in the 3rd
row (green). The transit
length was measured
to be L = 2.88 ±
0.03 hours, which is slightly
longer than the consensus
value of 2.91 hours.
The transit depth is 23.0
± 0.6 mmag, which
is the same as the consensus
value. Fp is the fraction
of time the transit is "partial,"
defined using contact
times as Fp = ((t2 - t1) + (t4 - t3))
/ (t4 - t1). The solution
for Fp is 0.25 ± 0.03. F2
is the ratio of depth at t2 and
t3 divided by the depth at mid-transit,
and for this solution F2 = 0.76
± 0.22. The ephemeris
HJDo and Period (used to calculate
expected mid-transit time)
are shown. The fitted temporal
trend (-0.42 mmag/hour) and
air mass curvature coefficient
(+1.20 mmag / airmass) are
given. The entry "Early:
0.6 ± 0.9 min"
states that mid-transit
was earlier than the
ephemeris time by 0.6 minutes.
You'll note that blue entries
are specific to the
submitted observations
and green
entries
are from an ephemeris
or a consensus of previous
observations. The upper
panel includes a plot of
departures of the measured magnitudes
from the model fit,
or "O-C" (observed minus
computed). The lower panel's
large red circle data, with
SE bars, are averages of non-overlapping
groups of either
5, 7, 9, 11, 13 or 17 individual
image values. At the bottom
of the lower panel is a green
trace showing "losses" offset so that
their magnitude value is 1.0
when losses are zero (as read on the
right side). Losses refer to the effect
of clouds, dew on the corrector
plate, wind shaking the telescope
enough to broaden the point-spread-functionof
all stars so that
some of the photo electrons
spill out of the aperture
circle. For this example there
was dew formation on the corrector
plate that was evaporated
with a hair dryer at 1.1 UT,
and another dew formation just
prior to the end of observations (~0.1
magnitude loss in both cases).
I've adopted this presentation because it is quicker to produce than previous
versions. If
Caltech really does
assume responsibility
for the
AXA it won't be open
for public submissions
for at least
6 months, and
during that time I want
to minimize my workload.
A program is used to perform
chi-square fitting
of submitted data
and records a file that is
easily imported to the spreadsheet
which is
screen captured as an image
file for import to a web page.
The entire process is much
faster than the hand solution
searches I used to perform,
and this will enable
me to accept more data submissions.
If you preferred
the other versions, requiring
hand-entered values
for such things as mid-transit
time, length and depth,
then I hereby apologize
for abandoning them.
As stated
above, a description
is given
of the very
simple transit
"model" used for
fitting the submitted
measurements
at model
fitting.
Explosive Growth of Exoplanet Discoveries
The number of bright transiting exoplanets has doubled in the past year (mid-2006 to mid-2007). There may be an equal number of undiscovered transiting exoplanets among the list of 246 exoplanets discovered spectroscopically (i.e., from radial velocity variations) found on the TransitSearch.org web site. There are plenty of observing opportunities for amateurs not associated with a wide field camera survey team, like the XO Project. Even an "arm chair" amateur astronomer can become engaged with a study of existing observations. There is merit in collecting all LC observations for each object and searching for patterns. One pattern would be transit timing variations (TTV) of mid-transit times; another would be a search for shallow transits during OOT times; and a search could even be made for LC structure within a transit or just outside transit by combining and averaging many LCs. For example, an exoplanet with rings may produce a brightening just before ingress and just after egress. Some day there may be a central archive where ALL exoplanet LC observations can be found. It is appropriate for either NASA or NSF to maintain such an archive. Caltech's IPAC archive would be an appropriate place for this addition. It would also be appropriate for a European institute to host the archive. Until this happens I would like to urge my fellow amateur astronomers to share their LCs on this public archive.
The cumulative number of "bright transiting exoplanets" in the northern celestial hemisphere (blue sybmols and model fit trace) grew exponentially with a doubling time of 1.1 years during the early years, and may be slowing, as this "sigmoid" fit suggests. Survey cameras in the summer hemisphere appear to be reproducing this curve with a 3 year lag (green symbols and model fit trace). The maximum number for each hemisphere can be different, as indicated. The total number (brown data and trace) could approach 100 in about 5 years.
The first 21 BTE discoveries were in the north celestial hemisphere because until recently the wide field search cameras were only in the Earth's northern hemisphere. Now that southern hemisphere cameras are in operation it won't be long before we'll know about as many BTEs in the southern skies. If we assume the discovery rate function for BTEs will be the same for each celestial hemisphere (cumulative number doubling time of 1.1 years before "saturation") then the cumulative number curve for the NH can be shifted ~ 2.9 years to show what can be expected for the SH . Before the list of northern sky BTEs is complete to 14th magnitude the discovery rate curve will flatten out to some unknown limit which will depend on how many long period exoplanets are there to be discovered. The "sigmoid" curve fitted to the NH BTEs suggests that this will happen in 2 or 3 years. But in the meantime, the SH discoveries will accumulate, causing the total number of known BTEs to reach asn asymtote of about 100 sometime in the next 5 to 10 years.
"Exomoons" is an exciting new thing to look for in amateur transit observations,
as pointed out by
David Kipping (Sky & Telescope,
July 2009, pg 30-33;
also described at the author's web site:
http://www.homepages.ucl.ac.uk/~ucapdki/exomoons.html).
The concept is simple:
a moon of an exoplanet will cause
it to move around the parent
star with a varying orbital velocity,
causing mid-transit timing variations
(TTV) and also causing transit length
variations, TDV (Transit Duration
Variations). TTV effects for an Earth mass
moon could be as large as 2 minutes,
and the TDV effect could be as large as
1 minute. These effects could be measured by
amateurs! Come on, AXA contributors, let's
try to find them!
If an exoplanet has a debris system in the same orbit (e.g.,
volcanic ejecta
surrounding and perhaps
following the
"hot Jupiter" planet)
the debris particles
will "forward scatter
" and produce
brightness enhancements
before ingress and
after egress. The pre-ingress
and post-egress brightenings
should have a different
brightening amount
and shape. This effect is likely
to be too small for detection
using amateur observations
but unusually large,
transient ejection events
should not be ruled out.
If an exoplanet has a ring system the ring particles will also "forward scatter" and produce a brightening before ingress and after egress that can last several minutes. In 2004 Joe Garlitz and I independently noticed that amateur LC observations of TrES-1 showed a small brightening (~5 mmag) after egress, lasting ~10 minutes. Ron Bissinger did an exhaustive statistical analysis of many TrES-1 LCs and concluded that the feature was statistically significant. Subsequent HST observations failed to confrim the feature so we are left to assume that the apparent brightenings were a statistical fluke. All exoplanets should be inspected for such a feature even though the effect is probably going to be much smaller than amateur observations could detect (< 0.3 mmag according to Brown and Fortney, 2004 and Otha et al, 2008).
An exoplanet may have a moon of its own, and if its large enough it could produce a small fade either before ingress or after egress. This would probably be noticed as a change in mid-transit time since on any one transit the moon will affect only an ingress or only an egress for a given transit. Brown et al (2001) searched for this effect with HST observations of HD 209458 and found nothing. Again, amateur observations are likely to be insufficiently precise to observe such an effect unless the moon is comparble in size to the hot Jupiter.
Mid-transit time can vary if the exoplanet is accompanied by another exoplanet in an orbit with a period resonance, such as 2:1, 3:2, etc. For exoplanets with a long record of transit timing measurements these timing anomalies should be searched for.
Transit length and depth can vary if the transiting planet is close to "grazing" and another planet in a nearby orbit that inclined differently causes changes in the transiting planet's inclination. This was thought to be the situation for GJ 436 in January 2008 (Ribas et al, 2008a; Ribas has since withdrawn this suggestion in the light of later observations that offered a simpler interpretation). Still, any exoplanet with an "impact parameter" close to 1, such as GJ 436, TrES-2, TrES-3 and HD 17156, should be viewed as candidates for transit property changes due to inclination changes caused by another exoplanet in a resonant orbit.
If an exoplanet has Trojan planets (same orbital period but located at longitudes 60 ahead or behind) there may be a detectable fade at times that are offset 1/6 of a period before or after the main exoplanet transit event. For hot Jupiter periods of 3 days, for example, the Trojan features will occur ~12 hours before or after the ephemeris transit. This offset is longer than any single transit observing session, so only the OOT observations can be used for this purpose.
Sunspots will produce a small brightening during the interval Contact 2 to Contact 3 but they'd have to be large to be detected by amateur hardware. If a feature is seen on one LC it may not be seen on others unless the periods are the same (period of exoplanet orbit and period of rotation at the sunspot's latitude).
On a typical night at least one of the BTEs will undergo a transit. On those nights when none are observable check the TransitSearch candidate list. If no known BTE transits are on the schedule, and the TransitSearch candidate list is unappealing for the night, there is merit in conducting OOT observations of a BTE. Preference can be given to exoplanets that are ~1/6 of a period away from transit, since that's when Trojans would produce their transit signatures. Another consideration is "impact parameter" - the ratio of closest approach miss distance to star radius. Small impact parameters are good candidates for second exoplanet transits in outer orbits. Small impact parameter systems have flatter bottomed transit shapes (i.e., contact 1 to contact 2 is short compared with contact 2 to contact 3).
If your interest is in a search for LC transit shape anomalies, either brightenings or fadings before ingress and after egress, then give preference to observing a bright exoplanet. Although scintillation will be the same regardless of a star's brightness, the SNR (caused by Poisson noise) will be better for brighter stars.
May I suggest that you "adopt" an exoplanet that transists near midnight
and simply
observe it every
clear night. After
inspecting it
for anomalies that
you can hope are real
and repeating with
an unknown period,
the overall OOT
shapes can at least
be used to learn about
your observation's
systematics.
For example, an OOT
set of measurements would
produce a LC that
is "flat" and "horizontal"
if no systematics
were present.
However, if your polar
axis is slightly mis-aligned
(>0.1 degree),
and if your master
flat field is imperfect,
the LC will have a sloping trend
of as much as several mmag
per hour. If a small scale
feature in the master
flat is imperfectly represented
(such as a dust donut)
then features could be superimposed
on the sloping
trend line. A hot or cold pixel
(or imperfect master
dark frame) could produce
the same features. Another
systematic, that is quite
common, is for the OOT LC to be curved
in a way that is related
to air mass. This arises when
the exoplanet star is not the same
color as the reference star
(or the average color of the
reference stars, if ensemble photometry
is employed). If your OOT
observations produce an LC with
a curvature that is correlated
with air mass then you may
want to give attention to reference
star color when choosing
reference stars.
I have slowly come to appreciate some fundamental differences between
the kind of variable star observing and image analysis performed for the
AAVSO versus that required for exoplanets. Occasionally a new observer will
be handicapped by adhering to traditional variable star observing procedures.
For these
observers I recommend
reading a web page
I created that describes
the observing
task differences,
and how observing
strategy and image
analysis should be
adjusted on behalf of the
exoplanet task: Exoplanet Stars
Are Not Variable
Stars.
Whenever someone asks "what hardware is needed for observing exoplanet
transits"
I try to explain that
a more relevant question
to ask is "how competent
an observer must I be for observing
exoplanet transits?"
This idea has been dramatically
demonstrated by
an observation
that
has recently come to my
attention. Petr Svoboda
(Czech Republic)
used a 1.33-inch aperture
"telescope" (actually,
a 34 mm aperture
camera lens) with a SBIG ST-7
CCD camera to obtain the
following light curve:
Small
aperture light curve
made with a 1.33-inch
"telescope"
(34 mm camera lens).
Another impressive demonstration comes from Gregor Srdoc (Croatia) who
used
a 2.5-inch camera lens
attached to a regular DSLR
camera (12-bit) to
measure a 9.5 mmag depth transit
of XO-4. The message
from these two examples is
that "aperture isn't everything"
because technique
is important regardless of aperture.
Technique is based on
an understanding of observing
concepts, image analysis
and data analysis. I believe
that it's difficult
to teach any of this because the
best way to learn is to "flounder"
with whatever hardware is
available! So my advice to anyone who
wonders what hardware
is needed for exoplanet transit
observing is to change the question
to "how willing am I to learn
from floundering with whatever
hardware I have?" And remember, floundering
is fun!
An observing session that I designed specifically to identify the best
filter choice suggests that
CBB-band (clear with blue-blocking) is
the best overall filter for exoplanet observing. Details
of this analysis are are given at FilterPlayoff.
I don't completely understand why defocusing can improve light curve quality,
but I have demonstrated
to my satisfaction that
for the condition of
a bright target star and a nearby
interfering star
defocusing does indeed improve
light curve quality. It
will be instructive for every serious
observer to experiment
with defocusing. My demostration
is at the following two web pages:
DefocusingGeneralCase
& HD 80606 Defocused
Comment on Correcting LCs for Slope and Curvature
I disagree with the custom of professional astronomers who present transit light curve plots that have been "corrected" for a temporal trend and an air mass (extinction) correlation. The viewer has no clue about the magnitude of either correction when viewing a plot with those effects removed. As I show in my book Exoplanet Observing for Amateurs (Chapter 14, pg 82) the presence of these corrections influence such "transit parameters" as depth, shape, length and mid-transit time. There usually is a locus of points in slope/curvature parameter space (temporal slope and air mass coefficient) having equally good fits yet yielding varying results for transit parameters. Because of my experience with hand-fitting the LCs by experimenting with values for slope and curvature, and seeing the effect these choices have on transit parameters, I am reluctant to accept elaborate solutions for planet radius in a paper where there is no discussion of the slope/curvature fitting ambiguities. It's potentially misleading to simply experiment with the slope and curvature coefficients until the LC looks good, and then proceed with an elaborate chi-squared analysis seeking solutions for planet size, inclination, limb darkening, etc. without also including the slope and curvature coefficients as independent variables. Consider the following innocent-sounding description: "We then fit a linear function of time to the pre-ingress and post-egress data. A function of time proved to be a slightly better fit than the more traditional function of airmass." (reference available upon request).
I have adopted the practice of preserving the uncorrected photometry data points while applying the temporal trend and air mass correlated solutions to the "model fit" trace. These LCs may not look as pretty as the ones professionals publish, but they convey more information and are a more honest representation of the LC that was measured. Therefore, if you're used to seeing the pretty LCs with slope and curvature corrections removed, think twice before passing judgement on the sloped and curved LCs you see on the AXA web pages for each exoplanet.
I plan on adding a link to an illustration of quantitative effects upon
transit
parameters when
the slope and curvature
corrections
are treated
carelessly.
Several people have asked for a set of raw images of a real exoplanet transit
for the purpose of practicing with image analysis and spreadsheet manipulation
to achieve a useable transit light curve. So, finally, I've created a web
page where the images can be downloaded. I've added some instructions (minimal)
and a sample LC to show what can be achieved from the images. The web page
is at PracticeImages.
Ground Rules for Professional Use of
Data
Files
The description of various versions of these "ground rules" can be found at: GoundRules A short version that will be included in the header of those data files that are transferred to Caltech's IPAC computer (NStED archive), in late 2008, is presented here:
"Downloading of amateur data files is unrestricted. However, since
these data are
unpublished it is recommended
the observer
be contacted prior
to use of data. The observer
may be aware of specific
aspects of the data
that should be taken into
consideration when interpreted,
such as seeing,
clouds, wind, scintillation,
clock-setting
procedures,
optimized photometry
apertures, etc. If these
data are to be used in
a publication, it is requested
that the observer be acknowledged
by name along with a
brief description of the
hardware used."
All good things come to an end.
I don't know how good
the AXA has been, but I know
that it's coming to an
end. Slowly. The ending is a good thing,
for it signifies the achievement
of its original purpose.
I created the AXA 24 months ago to
preserve amateur transit observations
in a convenient place
where they could be used by professionals.
My intent has always been
to persuade an institution to
assume these responsibilities.
The AAVSO seemed like a natural
place for this but they couldn't
afford it. I eventually persuaded
Caltech to become involved, but their
role is limited to archiving.
The task of tabulating and analysing,
yielding such plots as TTV, depth and length
for each transiting exoplanet,
remained to be addressed. This was labor-intensive
and I sought funding to automate
it. NASA's Origins Program seemed preoccupied
with large, space-based projects,
so I was facing the prospect of
toiling indefinitely with unpaid analyses
and plotting. I discovered by accident
that the Czech Republic Astronomy Society
has been downloading AXA data files,
supplementing them with other data in the public
domain, and producing tables and plots
that resemble those on the AXA (at a
web site called Exoplanet Transit Database,
or ETD). The Czech web site not only performs
the analysis that AAVSO could not afford, but
they also accept data submissions and maintain
an archive. My goals of 18 months ago have
been achieved and I can begin to think about
resuming that retirement that officially began
10 years ago. It is a relief to know that institutions
are assuming the tasks that properly belong
with them; it was risky entrusting archiving
of potentially valuable data with an unfunded
individual who is 10 years into retirement.
For the rest of this year, 2009,
you may continue to
submit data files to the
AXA and I will process them and
post a light curve on the
AXA. I will convert these
data files to the special format
required by Caltech's
NStED archive, and transfer them
to NStED for eventual public domain
access. By the end of 2009 the NStED
will be able to accept your data
file submissions directly (using
AXA auto-fitting code translated to "C"),
and at that time you will switch
from submitting to the AXA to submitting
to the NStED. In view of the
fact that the Czech ETD is created
mostly from downloads of data that
is originally submitted to the AXA (which
I convert to a standard format for downloading
from AXA web pages), when
the NStED goes on-line (in mid-2009?) I
assume that the Czech ETD will obtain their
data by downloads from the NStED.
Therefore, whenever you submit a data file
to either the AXA (or later to NStED) you
can assume that it will also show up at the
Czech ETD, where it will be used to update tables
of observations and plots of TTV, depth and length.
This is a good arrangement because it relieves
me from the tedious task of manually updating
tables and plots, and it solves the problem of
my inability to obtain funding to automate these tasks.
Incidentally, you have the option of submitting
your data files to only the Czech ETD,
but then you wouldn't see my beautiful plot
with an auto-fit overlay, and your data would
never appear in the Caltech NStED. I therefore suggest that you continue
to submit data files to the AXA, as before
(even if you also submit
to the Czech ETD), and when
the NStED is ready to accept data
files directly I will notify
you about this transition. If you want
to see how your data compares with other
data, or if you want to see if your data is
contributing to an interesting TTV pattern,
you may check the Czech ETD web site. Here
is a web address for the Czech ETD: Czech Astronomical
Society Exoplanet Transit
Database
AXA
Submission
Statistics - at Time of 500th
Submission (2009.05.19)
Two years ago this month I received an e-mail from
Joao Gregorio
(Portugal) with a great-looking
transit light curve.
Joao must have seen my name on
the list of amateurs who helped the
XO Project discover XO-2
and XO-3, that had been announced that
month. I recognized observing
talent, more than comparable to that found
among the dozen amateurs on the amateur
XO Extended Team. I had the following
thought: "What a shame if this LC,
and the many others that were taken by amateurs
not on the XO extended team, were to fade
from the public domain and not be available
for future generations of professional
astronomers wishing to study trends of transit
properties." This was the origin of my
idea to start the AXA. How fitting, therefore,
that Joao Gregorio should be the one to make the
500th submission of data to the AXA. Joao is now
a member of the XO Extended Team of amateurs,
and he also continues to contribute to the AXA. Congratulations,
Joao!
During the 1.7 years that the AXA has existed I have
come to appreciate the strong interest in exoplanet transit observing by
amateurs in Europe. I would occasionally ask at my favorite telescope store
(Starizona, in Tucson): "Your store is usually crowded with amateurs buying
things, yet as far as I can tell there are no amateurs in Arizona observing
exoplanets; so what are the amateurs doing with the wealth of hardware that
surely exists in the Tucson area?" The answer was always something like "99.5%
of amateurs look through eyepieces, or use CCDs to take pretty pictures."
Suddenly,
one day, this made sense. Americans
are "right-brained"
and Europeans are "left-brained."
Rather, there's a slight
preference of thinking styles
in these two directions, based
on evidence that I won't bother you
with here. So, this prompted me to wonder
about the statistics of submissions
to the AXA. Did some parts of Europe stand-out
as "hot beds" of exoplanet observing? And what
about other regions of the world?
The first table, below, is a list of AXA submissions
by country,
with the country populations
and calculated submission
rates. The next table shows the
same data arranged by submission
rate. Thanks to one observer in
Cyprus (Yenal Ogmen) this country has
the highest per capita rate of AXA submissions.
The same explanation applies to Finland
(Veli-Pekka Hentunen), Croatia (Gregor Srdoc),
Portugal (Joao Gregorio) and Slovenia
(Matej Milelcic). Belgium has two active
observers (Tonny Vanmunster
and Bart Staels). Keep in mind that
in some countries, such as Italy
and the Czech Republic, amateurs have
other venues for posting their data,
so my tables below will be an under-count for
them. Incidentally, most of the
USA data are from just two observers (removing
them would lead to just 42 USA observations,
and a per capita submission rate of 0.14,
the same as Poland).
What about larger region statistics, such as Europe
and the USA?
The table below summarizes
world region statistics.
I'm surprised that no observations are coming in
from the most
populous part of the world: China,
India, Russia and Southeast
Asia (lumped together in the above
table as "Asia"). And what about
Australia and New Zealand? Come on, world,
let's catch-up to Europe!
Finally, I just want to salute you Europeans for
your involvement
with
exoplanet observing
and your contributions
to the AXA.
There are three main categories of software used
by exoplanet
observers: hardware control, image analysis
and data analysis/display. The
hardware will consist of the telescope and CCD
camera, and may also include a CFW, focuser,
autoguider, image stabilizer and dome (and maybe
some exotics others, such as cloud and rain
sensors). Several observers used different programs
for control of the telescope and CCD. Image analysis
consists of calibrating (bias, dark and flat), star
field alignment, artificial star placement and photometry
readings of star flux (or magnitude). This last task
may include one or more stars for reference, or even an
artificial star for reference, and it may also include
one or more check stars. The third category is data analysis
and display, which is almost always performed in a spreadsheet,
such as Excel.
Approximately 23 AXA contributors responded to my
inquiry
about what software they used for the above
tasks. Here is my analysis of these
responses.
Hardware Control: MaxIm DL (10), TheSky (8),
CCDSoft
(5), AstroArt (4)
Image
Analysis: MaxIm DL (8), FotoDif (5),
Iris (5), AIP4WIN (4)
Data Analysis/Display:
Excel (15), GnuPlot (4)
I was surprised by the variety of programs that are
in use for the first two of these tasks. Some that were mentioned only once
aren't listed in the above summary.
The overall most-used software is MaxIm DL, in spite
of its high
price. My software usage
is MaxIm DL, MaxIm DL and Excel.
(I also use TheSky/Six, but only offline,
for monitoring target location az/el and deciding
where to position telescope for bright star in
autoguider FOV.)
AXA and TransitSearch contributors. TotNr is the total number of submissions since inception of the AXA (2 years ago). The Submissions (during past 12 months) is used to order the most active observers at the top of the list. For the group of observers with a total of more than 18 submissions during the past 12 months exceeds 18 the of listing within that group is determined by the date of earliest of these 18 submissions (right-most date), which is a way of showing who has been most active recently.
Total number of LC submissions...... 683
Active Observers & their Code Obs'g Site TotNr Submissions (during previous 12 months)*
Bruce Gary
(GBL)
Arizona
104 1523,1309,0622,0622,0618,0507,0502,0429,0428,0426,0424,0421,0404,9927,9926,9924,9923,9917+
Gregor Srdoc
(SG2)
Croatia
81 0408,0415,0420,0426,0428,0429,9A03,9A03,9926,9926,9920,9910,9903,9903,9828,9830,9830,9828+
Joao
Gregorio
(GJ2)
Portugal
51 1607,1401,1409,9B30,9A10,9A06,9A05,9A05,9720,9704,9626,9602,9601,9528,9528,9524,9524,9521+
Ramon Naves
(NR2)
Spain
56 9908,9816,9815,9805,9729,9725,9720,9719,9718,9712,9612,9529,9527,9518,9406,9327,9324,9323+
Patrick Wiggins
(WPK) Utah
28
9B29,9B27,9B26,9B25,9B20,9B17,9B14,9930,9930,9922,9922,9821,9821,9818,9818,9818,9818,9810+
Colin Littlefield
(LCO)
Indiana, USA
18
9920,9920,9919,9913,9905,9811,9802,9727,9714,9708,9628,9626,9328,9302,9302,9227,9224,9215+
Veli-Pekka Hentunen
(HVP)
Finland
30 0502,0419,9925,9327,9325,9308,9226,9105,9105,8a29,8b06,8b06,8b06,8b06,8b01,8b01,8b01,8a29+
Manuel
Mendez
(MQZ)
Spain
37 9608,9518,9428,9414,9330,9316,9312,9119,9115,9114,8b25,8b16,8b14,8b11,8b06,8b01,8829,8825+
Bill Norby
(NWP)
Missouri
20
9825,9825,9817,9814,9807,9803,9801,9727,9723,9714,9630,9630,9626,9623,9619,9617,9605,9601+
Anthony
Ayiomamitis
(AA2)
Greece
23 0328,0328,9904,9828,9606,9514,8b26,8b22,8a08,8a05,8906,8903,8902
James Roe
(ROE)
Missouri
28
9930,9930,8918,8918,8903,8819,8801,8808,8804,8729,8729,8729
Toni Scarmato
(SFI) Italy
12
0502,0501,9626,9616,9426,9419,9328,9328,9326,8c06,8b20,8814
Johannes
Ohlert
(OJ2)
Germany
9 9B05,9A09,9A09,9A09,9A09,9829,9829,9829,9808,9808,9705
Cindy Foote
(FC2)
Utah
59
9117,9117,9114,9109,8c11,8b18,8b17,8a29,8903,8903
Standa
Poddany
(PS2)
Czech Republic 11
9B01,9426,9426,9408,9408,8a23,8905,8905,8827
Yenal Ogmen
(OYE)
Cyprus
11 9129,9129,9123,9121,8a11,8907,8922,8724
Fernando Tifner
(I32) Argentina
7 9930,9930,9926,9922,9911,9328,8925
Joe Garlitz
(GJP) Oregon
6
9828,9826,9728,9629,9624,9616
Paulo Lobao
(J15) Portugal
5 9713,9708,9703,9701,9630
Alessandro Marchini
(MXI)
Italy
5 9711,9415,9223,9202,9106
Fabio
Salvaggio+
(SFV)
Italy
8
9708,9703,9309,8901,8901
Enric
Forne
(FE2) Spain
5 9731,8c16,8929,8929,8929
Ricard
Casas
(CRI)
Spain
4
8929,8929,8929,8929
Brian Tieman
(TBJ) Illinois
3 0415,0417,0418
Pere Salom
(B81) Spain
3 9A30,9802,9726
Marcin Wardak
(WMK) Poland
3 9429,9428,9425
Shawn Dvorak
(DKS) Florida
3 9512,9512,9423
Bart Staels
(SBL)
Belgium
8 9215,9215,8c31
Peter
Kalajian
(KP2)
Maine
3
9711,8908,8911
Daniel Brown
(J06) United Kingdom
2 0503,0426
John Cordiale
(CQL)
New York
2
9A21,9A02
Claudio Arena
(AC2) Italy
2
9713,9629
Xavier Puig
(PX2)
Spain
2 9731,8929
Adam Jesiokiewicz
(JA2)
Poland
2 9429,9428
Riccardo
Papini
(PCC)
Italy
2 9328,9206
Miguel
Rodriguez
(RMU)
Spain
4
9322,880
Carlos Gonzalez
(B99)
Spain
1 9711
Giuseppe
Marino
(MG3)
Italy
3
9525
Matej Mihelcic
(MHM) Slovenia
2 9426
Giorgio Corfini
(CGI) Italy
1
9328
Claudio Lopresti
(LC3)
Italy
1 9328
Javier Salas
(SJ2) Spain
1
9317
Enrique Garcia-Melendo
(GM2) Spain
1
9314
Josep
M Coloma
(CJI) Spain
1
8c16
Petr Svoboda
(SP2) Czech
Republic
1 8b03
Ramon Costa
(CR2)
Spain
1 8929
Joal
Bel
(BJ2)
Spain
1 8929
Gustav Muler
(MG2)
Canary Islands
2 8914
Tonny
Vanmunster
(VMT)
Belgium
34
Darrel
Moon
(MD2)
Utah
3
Nicolaj
Haarup
(HNI)
Denmark
5
Stelios
Kleidis
(KSM)
Greece
1
* Date code is YMDD. Example #1: 20080317 = 8317; Example #2: 2007 December 31 = 7c31 (think HEX). Starting 2008 July 8 entries will be for date of submission, not observing date.
Some of the 3-letter observer codes for the active
observers
have links to description
of hardware
(and picture
of hardware
with observer).
RelatedLinks
Exoplanet
Observing
for Amateurs
(book, free PDF download)
Useful
spreadsheets
(BTE_ephem.xls, etc)
Jean Schneider's Extrasolar
Planet
Encyclopaedia
Greg
Laughlin's
TransitSearch
archive
Czech Astronomical
Society Exoplanet
Transit Database (ETD)
NStED
(Caltech's
NASA/IPAC/MSC
Star
and Exoplanet
Database)
Planetary
Society Catalog
of Exoplanets
Bruce's
AstroPhotos
Resume
Artwork
by Klaudia
Einhorn
AXA Logo Courtesy Matej Mihelèiè
(depicting
transit
of CoRoT-7)
WebMaster: B.
Gary. This site opened:
2007 August 06, Last Update: 2011.04.24