The AXA has discontinued receiving data file submissions. Please
submit your data to the Czech Republic's Exoplanet Transit Database.
The AXA has discontinued receiving data file submissions. Please
submit your data to the Czech Republic's Exoplanet Transit Database.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
The summer months for northern hemisphere observers have
short observing sessions
that offer fewer BTE transit observing
opportunities. It's my impression that the
easy BTEs for the summer are not intereseting,
with one exception: XO-1. This old BTE is nearing the
end of its observing season, but I have a special
interest in it because of a possible sinusoidal
variation in mid-transit times (TTV), so I give this
object high priority for those few times when it's
observable. TrES-1, TrES-2 and TrES-3 are easy targets,
but they're "well behaved" and I don't think there's
anything more to learn about them. TrES-4 is fairly easy
to observe, and I give it medium priority because transit
propertires are not adequately characterized. HAT-P-5
is a fairly easy target, and we need transit observations
with a variety of filters, such as B-band and I-band, since
depth appears to vary in an unusual way with wavelength (increasing
depth with increasing wavelength, implying a close to grazing
transit geometry). HD 189733 is easy if you have a small
aperture or are good at defocused observing (V-mag 7.67,
29.0 mmag, 30 AXA observations). WASP-3 has weak evidence
for increasing transit length with date, and it's a fairly easy
trarget, so I'll give this one some priority. CoRoT-2
is easy (35.2 mmag, V-mag = 12.6, 13 observations in AXA),
and we need more observations in the 2009 summer season to
characterize transit shape and TTV. Among the more difficult
BTEs that can be observed are HAT-P-11 (depth 4.2 mmag, 2 observations
in the AXA database), CoRoT-3 (depth 5.2 mmag, no observations),
HAT-P-7 (7.1 mmag, 11 observations), HAT-P-2 (5.5 mmag, V-mag
8.7, no AXA transit observations) and finally HD 149026 (3.0
mmag, V-mag 8.2, 1 AXA observation). I give the highest observing
priority to this last BTE, HD 149026, but since it is bright it
should be observed in the defocsued mode by only advanced observers.
Also, the AAVSO is asking for observations of a white dwarf EB that
might harbor a planet: V1412 Aql, at 20:13:55.5 +06:42:40 (V-mag
15.75). Observations at any time are potentially useful. Submit any
interesting data to the AAVSO, or contact me for help doing this.
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 45 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...... 680
Active Observers & their Code Obs'g Site TotNr Submissions (during previous 12 months)*
Gregor Srdoc
(SG2)
Croatia
75 9A03,9A03,9926,9926,9920,9910,9903,9903,9828,9830,9830,9828,9826,9825,9824,9822,9822,9820+
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
93
9927,9926,9924,9923,9917,9817,9816,9602,9524,9516,9512,9508,9430,9418,9413,9305,9303,9207+
Veli-Pekka
Hentunen
(HVP)
Finland
28
9925,9327,9325,9308,9226,9105,9105,8a29,8b06,8b06,8b06,8b06,8b01,8b01,8b01,8a29,8a29,8a29+
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+
James Roe
(ROE)
Missouri
28 9930,9930,8918,8918,8903,8819,8801,8808,8804,8729,8729,8729
Johannes
Ohlert
(OJ2) Germany
9 9B05,9A09,9A09,9A09,9A09,9829,9829,9829,9808,9808,9705
Anthony
Ayiomamitis
(AA2)
Greece
19 9904,9828,9606,9514,8b26,8b22,8a08,8a05,8906,8903,8902
Cindy
Foote
(FC2)
Utah
59 9117,9117,9114,9109,8c11,8b18,8b17,8a29,8903,8903
Toni
Scarmato
(SFI) Italy
10 9626,9616,9426,9419,9328,9328,9326,8c06,8b20,8814
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
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
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
9322,8809
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: 2010.03.14