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:
Best for this Season
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
Until April 12, 2010, the AXA will accept data file submissions for only
HAT-P-13 because of a collaboration between AXA and University
of Florida astronomers who will be investigating 1) anticipated
HAT-P-13b TTV during Apr/May/Jun, and 2) a possible transit by
HAT-P-13c.
Specific transit times opportunities can be determined by downloading EPHEM_BTE.zip (see http://brucegary.net/book_EOA/xls.htm) and unzipping the spreadsheet (that now supports all 55 known BTEs, showing ingress, mid-transit and egress times for any observing site and any date). The Czech Astronomical Society can also be used for determining transit observing opportunitiesfor any BTE, any site and any date: link.
This archive was promted by the fact that amateurs have no place to submit
their observations
of exoplanet
transits where
they will be processed
and displayed
in a useful format.
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 is an unmet need for
an archive that collects amateur
LCs and presents them
in a uniform format. Such
an archive will 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
is not in the public domain.
The AXA is open for anyone
to submit observations that
are likely to be added to the AXA
web pages and maintained as a historical
archive.
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)*
Gregor
Srdoc
(SG2)
Croatia
81 0408,0415,0420,0426,0428,0429,9A03,9A03,9926,9926,9920,9910,9903,9903,9828,9830,9830,9828+
Patrick Wiggins
(WPK) Utah
28
9B29,9B27,9B26,9B25,9B20,9B17,9B14,9930,9930,9922,9922,9821,9821,9818,9818,9818,9818,9810+
Joao
Gregorio
(GJ2)
Portugal
49
9B30,9A10,9A06,9A05,9A05,9720,9704,9626,9602,9601,9528,9528,9524,9524,9521,9519,9518,9516+
Ramon Naves
(NR2)
Spain
56 9908,9816,9815,9805,9729,9725,9720,9719,9718,9712,9612,9529,9527,9518,9406,9327,9324,9323+
Colin Littlefield
(LCO)
Indiana, USA
18
9920,9920,9919,9913,9905,9811,9802,9727,9714,9708,9628,9626,9328,9302,9302,9227,9224,9215+
Bruce Gary
(GBL)
Arizona
104 0622,0622,0618,0507,0502,0429,0428,0426,0424,0421,0404,9927,9926,9924,9923,9917,9817,9816+
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: 2010.07.29
