# Transit LCs
# Transit LCsWhat'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
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
Related Links
Note: HD 68988 may be a transiting exoplanet
system, according
to two observations submitted to the AXA.
Confirmation of future transit predictions
is high priority.
Many exoplanets are "in season" in the winter months. HD 17156 continues to intrigue astronomers, professional and amateur alike. It is well situatied for winter observing, but with a period of 21.2 days each transit becomes a high-value target. HAT-P-8 is the latest discovery but it is observable for only 5 hours in mid-December (setting through 20 degrees elevation before midnight). WASP-11 and the newly-announced WASP-12 are perfectly situated for December observing and they need to be observed. HAT-P-9 needs observations (none in the AXA) but it's an early morning object. XO-3 is perfectly situated for December and January observations, but it is well characterized so I'm unaware of scientific value in observing it this year. XO-2, 4 & 5 are January and February objects, the 4 & 5 need observations. HAT-P-9 is a morning object, and so far the AXA has no observations for this BTE. GJ 436 is an early morning object, and it will merit observing for years to come. Finally, a new candidate for transits is HD 68988 (RA/DE = 08:18:22.2, +61:27:38, V = 8.2) which Hentunen observed to have D ~ 8.4 mmag on 2009.02.25. A tentative ephemeris for HD 68988 transits is HJD = 4888.52 + 6.27613 * E (where E is an integer). The Czech Astronomical Society has an excellent web page where HD 68988 transits can be calculated with visibility information for any observing site: link. GJ 436 not as interesting as it once was; there are no discenrible variations in transit properties.
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 rate of discovery of "bright transiting exoplanets" is growing exponentially with a doubling time of 1.1 years. The discovery rate of BTEs in the northern celestial hemisphere (orange) can serve as an estimate for what can be expected for the discovery rate of BTEs in the southern skies. By the end of 2008 there may be ~52 known BTEs using this model.
The first 21 BTE discoveries were in the north celestial hemisphere because until recently the wide field search cameras were only in the northern hemisphere. Now that southern hemisphere cameras are in operation it won't be long before there will be about as many BTEs in the southern skies. If we assume the discovery rate curve for BTEs in each celestial hemisphere has the same shape (doubling time) then the discovery rate curve for the NH (orange trace in above figure) can be shifted 2.4 years to show what can be expected for SH discoveries versus time (green trace, in above figure). By the time 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. This is unlikely to happen before the end of 2009.
"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!
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 18 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.
AXA and TransitSearch contributors (top of list is the most frequent contributor). The contributor list is for only "active " observers. To be "active" an observer must have contributed at least one observation during the previous 12 months (the date of the observation is not relevant). (Three of the observers on the lists are more active than they appear since they are contributors to the XO Project and only some of their observations can be submitted to the AXA; they are Foote, Gregorio and Vanmunster.)
Total number of LC submissions...... 550
Active Observers & their Code Obs'g Site TotNr Submissions (during previous 12 months)*
Bruce Gary
(GBL)
Arizona
86
9602,9524,9516,9512,9508,9430,9418,9413,9305,9303,9207,9128,9117,9109,8c10,8b30,8b14,8b08+
Ramon Naves
(NR2)
Spain
46
9612,9529,9527,9518,9406,9327,9324,9323,9320,9318,9313,9309,8b29,8a06,8915,8909,8818,8818+
Joao
Gregorio
(GJ2)
Portugal
42
9626,9602,9601,9528,9528,9524,9524,9521,9519,9518,9516,9501,9423,9414,9414,9410,9405,9331+
Manuel Mendez
(MQZ)
Spain
37 9608,9518,9428,9414,9330,9316,9312,9119,9115,9114,8b25,8b16,8b14,8b11,8b06,8b01,8829,8825+
Gregor
Srdoc
(SG2)
Croatia
34 9701,9620,9616,9616,9615,9613,9610,9608,9529,9526,9524,9523,9520,9518,9516,9325,9323,8a27+
Veli-Pekka Hentunen
(HVP) Finland
27 9327,9325,9308,9226,9105,9105,8a29,8b06,8b06,8b06,8b06,8b01,8b01,8b01,8a29,8a29,8a29,8a18+
James Roe
(ROE)
Missouri
26 8918,8918,8903,8819,8801,8808,8804,8729,8729,8729,8615,8617,8612,8611,8528,8525,8522+
Anthony Ayiomamitis
(AA2)
Greece
17
9606,9514,8b26,8b22,8a08,8a05,8906,8903,8902,8709,8628,8626,8613,8606,8603,8528,8503
Cindy
Foote
(FC2)
Utah
59 9117,9117,9114,9109,8c11,8b18,8b17,8a29,8903,8903,8624,7b13,8607,8607,8607+
Yenal Ogmen
(OYE)
Cyprus
11 9129,9129,9123,9121,8a11,8907,8922,8724,8710,8702,8630
Bill Norby
(NWP) Missouri
10 9630,9630,9626,9623,9619,9617,9605,9601,9521,9521
Colin Littlefield
(LC2) Indiana,
USA 10
9628,9626,9328,9302,9302,9227,9224,9215,9209,8B22
Standa Poddany
(PS2)
Czech Republic 10
9426,9426,9408,9408,8a23,8905,8905,8827,8716,8627
Toni
Scarmato
(SFI) Italy
10
9626,9616,9426,9419,9328,9328,9326,8c06,8b20,8814
Patrick Wiggins
(WPK) Utah
7 9629,9629,9625,9620,9617,9604,9604
Fabio Salvaggio+
(SFV)
Italy
6 9309,8901,8901,8706,8616,8614
Alessandro Marchini
(MXI) Italy
4 9415,9223,9202,9106
Miguel Rodriguez
(RMU)
Spain
4 9322,8809,8512,8415
Enric Forne
(FE2) Spain
4 8c16,8929,8929,8929
Ricard
Casas
(CRI) Spain
4 8929,8929,8929,8929
Nicolaj
Haarup
(HNI)
Denmark
5
8413,8320,8319,8318
Giuseppe
Marino
(MG3) Italy
3
9525,8717,8616
Shawn Dvorak
(DKS) Florida
3
9512,9512,9423
Marcin Wardak
(WMK) Poland
3 9429,9428,9425
Bart Staels
(SBL)
Belgium
8
9215,9215,8c31
Joe Garlitz
(GJP) Oregon
3 9629,9624,9616
Riccardo Papini
(PCC) Italy
2 9328,9206
Fernando Tifner
(TF2) Argentina
2 9328,8924
Peter Kalajian
(KP2)
Maine
2
8908,8911
Gustav
Muler
(MG2) Canary Islands
2
8914,8301
Tonny Vanmunster
(VMT)
Belgium
34
8511,8511
Darrel Moon
(MD2) Utah
3
8704,8703
Adam Jesiokiewicz
(JA2) Poland
2 9429,9428
Paulo Lobao
(J15) Portugal
2 9701,9630
Claudio Arena
(AC2) Italy
1 9629
Matej Mihelcic
(MHM) Slovenia
2 9426
Giorgio Corfini
(PCC) 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
Xavier Puig
(PX2) Spain
1 8929
Stelios
Kleidis
(KSM) Greece
1
8607
* 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: 2009.07.02