Search results for variable star

A mysterious object no more

This post is by Tabby Boyajian, one of the Planet Hunters science team at Yale

As you all know, planethunter volunteers use archive data taken with the Kepler space telescope to classify lightcurves and identify transiting planets. Since the launch of the Planethunters citizen science program, we have contributed five scientific publications reporting on the discovery of dozens of candidate and confirmed exoplanetary systems – otherwise undiscovered by the Kepler team.

The design of the project is expanding with the opportunity for Planethunter volunteers to support astronomers interested in using Kepler data for scientific research unrelated to the main exoplanet goals of the Kepler mission. We have dubbed this as our own ‘Guest Scientist’ program. The idea is that guest scientists participate in Planethunters Talk forum and make requests for the public to collect particular light curves, such as signatures of moons or rings, pulsators, variable stars, flare stars, cataclysmic variables, or microlensing events.

This schematic, by Planet Hunter Daryll LaCourse, shows off our new discovery.

This schematic, by Planet Hunter Daryll LaCourse, shows off our new discovery. (Click to make larger)

We are delighted to announce that the first paper presenting results associated with the Planethunters Guest Scientist program has been accepted for publication in the Astrophysical Journal! In this paper, the lead scientists Doug Gies and Zhao Guo from Georgia State University and Steve Howell and Martin Still from NASA AMES follow up on a mysterious object in the Kepler field identified by Planethunters, later confirming it to be an unusual type of cataclysmic variable. They perform an in-depth analysis on the Kepler lightcurve as well as observations made at the Kitt Peak National Observatory 4-m Mayall telescope and RC spectrograph. The result is a newly published paper, so take a momtent to read ‘KIC 9406652: An Unusual Cataclysmic Variable in the Kepler Field of View’ or to check out the planethunters talk thread where the object was first discovered and discussed:

Thanks you all for your enthusiasm and contributions to the scientific community. We have several other projects underway so keep an eye out for updates in the future!

More about the Discovery of PH2-b

The project’s second confirmed planet, PH2-b (a Jupiter-sized gas giant planet orbiting a Sun-like star), was discovered by several members of the PH community who classified the light curve and then posted the candidate on Talk. A volunteer-organized effort took this from a possible repeat of transits to a likely candidate that was then passed to the Science Team and subsequently validated as a real bona fided planet. Volunteer rafcioo28 who was the first person to mark a transit in Q4. Mike  Chopin was the second and the one to first  post on the Talk page about the transit in February of last year. Hans Martin Schwengeler went to look at the rest of the publicly released Kepler data months later spotting the other transits. Together rafcioo28, Mike, and Hans with the help of Abe Hoekstra, Tom Jacobs, Kian Jek, Daryll LaCourse  have discovered Planet Hunters’ 2nd confirmed planet PH2-b.  I’ve asked Mike and Hans (rafcioo28 we haven’t been able to contact thus far) write a bit about their thoughts on the discovery.

PH2_moon

Artistic rendition is a hybrid photo-illustration, showing a sunset view
from the perspective of an imagined Earthlike moon orbiting the giant planet, PH2 b. Image Credit: H. Giguere, M. Giguere/Yale University

Mike Chopin

At school, at the age of fourteen, I did a project on atomic (particle) physics which gained me a grade 1 CSE. The following year I studied and passed my Physics exam which was interesting for my school since that was a subject not on the school curriculum. After leaving school, I studied OND Engineering at Kingston Polytechnic although I only completed my first year since I longed to go travelling. My wanderlust got the better of me and I joined a shipping line as a Navigating Cadet Officer. I suppose it’s easy to see why astronomy has fascinated me since knowing about stars was part of my navigation syllabus.

My childhood hero was, and still is, Captain James Cook a man I consider to be the greatest explorer of all time. I consider myself fortunate to have visited many places this great navigator charted. In 2012 his observation of the transit of Venus in 1769 was commemorated at Venus Point in Tahiti. Although I wasn’t there for 2012, I did get to Venus Point a couple of years earlier. Like Cook, I spent some time in the Navy and have a passion for boats especially under sail. I have two complete circumnavigations under my belt; the first by sea (unfortunately via the Panama Canal and not Cape Horn) the second was by air, island hopping my way across the Pacific. I have now visited ninety six countries and hope that it won’t be too long before I join the Travellers’ Century Club.

Latterly, I was employed by Lloyds TSB (Registrars) as a project officer with my principal role as the sole technical writer writing context sensitive help for software, on-line documentation, trouble-shooting guides for the IT department and interactive eLearning modules. Following redundancy, I went freelance as a writer and have had a couple of small contracts both as a writer and as a data manager.

I am delighted to have been involved with the discovery of an exoplanet, a planet orbiting a distant sun. From the outset, I enjoyed the thrill of analysing the light signals recorded and posted on the planethunters.org website. This website invites ordinary people to take part in analysis of vast amounts of data. Often called ‘Citizen Science’ this excellent website provides clear tutorials to enable the amateur to partake in this worthwhile research project.

In its simplest form, when an exoplanet passes between our line of sight and its sun, there is a reduction in the amount of light that we receive. This effect can be seen if we plot the light output from this star against time. While trying to analyse the data, I would try to imagine the planet transiting its sun, if it was a large planet and close to its sun would it cut more light than if it had been a small planet and a giant sun? Does it have a high reflectivity (albedo) and is it inclined to its ecliptic and if so, would it add or reduce the amount of light recorded. If distant suns had multiple planets with systems similar to our own solar system, then would it be possible to identify additional planets. It was with all these ideas in mind that I began my quest for the exoplanets.

Sometimes, the pattern appeared to be too random to be able to distinguish a planet and at others, beautiful patterns could be seen as if generated by an oscilloscope, these it would seem were possible candidates for a binary star and so these were recorded also. Now and again, a pattern would emerge which would make you sit up and take notice. Using the sliders on the screen, I would drag out the ‘x’ scale to magnify a section of the screen where I was certain a transit was occurring and then I would check to see whether there was a second transit which may indicate its periodicity. It was during such an event that I found, what is recently been called, PH2-b. With, what at time was simply a planetary candidate; I posted a note to see if any of my fellow planet hunters had seen what I had seen.

Carl Sagan spoke of the ‘Pale Blue Dot’, the Earth as seen from Voyager 1 in the distant reaches of space, how exciting would it be if spectral analysis revealed this planet to have water and an atmosphere, another ‘Pale Blue dot’, now that would be truly remarkable.

Hans Martin Schwengeler

I’m a regular user (zoo3hans) on PH, more or less from the beginning two years ago. My name is Hans Martin Schwengeler and I live near Basel in Switzerland. I’m 54 years old, I’m married and we have two children. I’m a mathematician and work as a computer professional. I like to advance Science in general and Astronomy in particular. I did work a few years at the Astronomical Institute of the University of Basel (before it got closed because they decided to save some money…), mainly on Cepheids and the Hubble Constant (together with Prof. G.A. Tammann). Nowadays I’m very interested in exoplanets and spend every free minute on PH.

I’ve always been interested in stars, planets and the universe in general. So when I studied Mathematics at the ETH in Zurich it was natural to choose Astronomy as a second discipline. After working a few years on a Statistics research program (based on the Kalman Filter) I managed to get a job at the Astronomical Institute of the University of Basel (Switzerland) as a system manager. There I could work part time on research programs, mainly on Cepheids to determine the Hubble Constant (together with G.A.Tammann and Allan Sandage). I did this with the image processing software ESO-MIDAS, where we analyzed images taken by the ESO New Technology Telescope (NTT) or the Hubble Space Telescope (HST). I also used a program (written in Fortran-77) called superperiod to find the periods of the variable stars found in the galaxy images and see if they could be cepheids with periods between 2 and 100 days. With the Cepheid period-luminosity relationship we were then able to determine the distance of the Cepheid and the host-galaxy.

As soon as Michel Mayor and Didier Queloz detected the planet around 51 Pegasi, I was drawn in into exoplanets. I followed every single announcement of the detection of a new exoplanet on Exoplanet.eu and arXiv.org and elsewhere. So when I first took notice of the Planet Hunters project, I joined immediately. In the meantime the Astronomical Institute has been closed down (on monetary reasons) and I was working as a systems engineer at the Federal Office for Information Technologies and Telecommunications in Bern. I did not have anymore the tools needed to analyze light curves and so on. I also had to realize that to detect a planet transit in a Kepler light curve is not so easy as I first thought (except for the very big Jupiter-like ones). The learning curve was rather steep. Fortunately some fellow hunters had already gathered some very good insight and also some useful tools. So after some months I think I accumulated enough experience to do some real work here on PH.

So when I got the light curve for KID 12735740 I thought it looks very nice and might be a real planetary transit. Kian Jek had already commented on it favorably. The transit shape is more like an “U” instead of a “V”, the transit depth and duration is compatible with a 1.1 R_Jupiter planet with a period around 282.6 days. We can check this with Kian’s very good Planetary Calculator. The first thing I then usually do, is to have a look at the sky view  and then post this image to the PH Talk pages for others to have a look too My second step is then to download the FITS files from MAST (using the very good tools from http://www.kianjin.com/kepler/detrend.tar.gz ), detrend the curve roughly and view it by eye first (often using the program ggobi for this purpose). I upload the light curve also to PH if it looks interesting. Thirdly I may do a periodogram to find the period if a good period seems to be present (and upload it as well of course).

In the case of KID 12735740 I think all looks very good for a real planet candidate. Not much would be possible without the help of others, especially Kian Jek (aka kianjin) is invaluable here at PH. He compiles very good lists of “good candidates” or EB lists. I also find the other lists of “good Q2 candidates (non Kepler favorites)” (or Q3, Q4, etc. lists) very helpful in finding candidates and discuss them in more detail. It’s otherwise rather difficult to keep track of all the interesting cases on PH Talk. Kian does also the best detrending jobs, contamination vector determination, fitting of transit parameters, and more. nighthawk_black does perfect Keppix analysis, troyw has his amazing AKO service, capella, JKD, ajebson, gccgg, Tom128 and many other are very helpful too.So very often we work together here at PH as a good team.

In order to discriminate between real transits and instrumental or processing artifacts, I add comments to the “consolidated list of glitches” in the Science section on the PH Talk site. I collected a few bright and quiet and constant stars over the last few months / years exactly for this purpose. When I see a dip on one light curve and the same feature is also present on the other light curves, then it’s very likely a glitch.

I think the PH project is a great contribution to Science. I’d like to thank all fellow PH hunters for their help and also to Meg.

Kind regards,
Hans Martin Schwengeler (aka zoo3hans)

In addition to Mike, Hans, and rafcioo28, several others get a tip of the hat for marking transits in the discovery light curve for PH2: Sean Flanagan, Anand, and Jaroslav Pešek. Congratulations to you as well.

Planet Hunter Kian awarded the Chambliss Prize

Congratulations to Planet Hunter Kian Jek, who just received the Chambliss Amateur Achievement Award! This is the premiere award for amateur astronomers presented by the American Astronomical Society – and we think it is highly deserved. Many of you know Kian, who works tirelessly on the site and to a large part is responsible for the dramatic success of Planet Hunters. He not only plays a leading role in hunting down planets, but has been responsible as well for much of the work on variable stars that the project has produced. This award is a suitable acknowledgement of his contributions, and we hope it also serves as recognition for all of the Planet Hunters by the American Astronomical Society. When solicited for a comment on the 42 new candidates in the latest Planet Hunters paper, co-author Kian (his third paper!) wrote:

“As someone who grew up with the Apollo moon landings, whose childhood imagination was fired by Kubrick’s 2001 and the original Star Trek, I never had any doubt that planets around other stars existed and that one day we would discover them. But I never dreamed that we would find them in my lifetime, let alone being involved in their discovery. Although there are over 700 discovered since 1996, each new planet opens another door to a strange alien world, some of them we could not even imagine could exist. Planethunters is an exciting project that allows citizens and scientists participate in pushing the final frontier ever slightly further.”

A Newly Confirmed Planet and 42 Additional Planet Candidates Part 2

For our latest planet candidates paper, there were many volunteers who helped identify these potential transits on Talk. To thank all of them for their hard work and effort, their contributions are individually acknowledged here. A few people stood out organizing a  significant follow-up effort on their own working to  sort these potential candidates identified on Talk into a list of potential planet candidates. This included looking for repeat transits and performing checks  to rule out potential  false positives. To acknowledge their effort, the science asked Abe Hoekstra, Tom Jacobs, Kian Jek, Daryll LaCourse, and Hans Martin Schwengeler  to be co-authors on the paper. I’ve asked them each write a bit about this experience and about being part of Planet Hunters.

Abe Hoekstra

I am from the Netherlands and am fifty years of age. In the past I used to be a teacher. Astronomy has always been a hobby of mine, I am what they call an armchair astronomer. I couldn’t pursue a career in astronomy as I am very bad at maths and physics. Early 2011 I got my first laptop and I subscribed to the NASA Newsletter. When I was reading up on exoplanets, I came across Planet Hunters. I am very glad I can make a contribution to astronomy, however small.

When I heard my name was going to be mentioned on the Planet Hunter Planet Candidates paper, I was quite surprised, excited and very honoured. I have been so busy with eclipsing binaries, variable stars, dwarf novae and checking out dozens and dozens of collections of fellow planet hunters, that I almost forgot I made some contributions with respect to finding planetary transits.I had to check the candidates on the list to see where I made those contributions. I found  one candidate that I may have discovered first, shortly after I started here in February 2012, and another where I was among he first to spot a transit.  I also helped in  finding repeats of transit features, by checking out NASA’s Exoplanet Archive  (NEA). I definitely remember two candidates I found in other planet hunters’ collections in November.Finding a transit feature and/or repeat is very exciting. It doesn’t stop there. I am among those planet hunters that regularly check stars on Sky View and the NEA. Other hunters are very experienced in doing contamination checks, determining the length and depths of transits, and also determining the period of a planet.That is what I like about Planet Hunters. There is a great sense of community and cooperation here. I hope a lot of planet hunters get a mention in the paper. A great deal of hard work has gone into finding these planet candidates, and finding your name up there is very rewarding.Let’s hope we can add a few more candidates to the list in 2013!

Tom Jacobs

I am a graduate of the University of Washington with a non science degree in Business Administration and later commissioned as an officer in the U.S. Navy. Currently, I reside in Bellevue, Washington with my family and work as an employment consultant for workers with developmental disabilities going on 17 years. I have always been a treasure hunter and consider Planet Hunters a great way to find planet and other unique star treasures and learn some astrophysics through immersion along the way.

It is a great honor to be part of this planet candidate discovery paper as a Planet Hunters’ citizen scientist. Nothing occurs in a vacuum at Planet Hunters.  If not for all your hard work in classifying light curves and posting your finds on Talk, most likely these planet gems would have slipped away unnoticed. You all deserve as much credit as those mentioned in the  science paper.  It is all about teamwork and diligent pursuit in analyzing the Kepler light curves. We are collectively demonstrating what the incredible pattern recognition of the human mind can accomplish that challenges the high powered state of the art computer algorithms and we are having fun while doing it.

Kian Jek

I have been fascinated by the stars ever since my uncle handed me a copy of a book by H. A. Rey when I was 10 years old. It wasn’t until much later when I had children of my own that I realized that Rey also wrote the Curious George books. I guess I must have been a geek since then because the other things going on that grabbed my attention were the Apollo moon landings and the original Star Trek series.

I used to spend hours with a tiny 2-inch telescope at night looking for the Messier objects, not knowing that it was almost impossible to see them all with an aperture that small – I was hung up on M1 for a long time! It was astronomy got me hooked on science but by the time I went to college I was sidetracked by an interest in DNA and I went on to get a degree in molecular genetics at Cambridge in the UK. One of my biggest thrills while studying there was being able to use a 180-year old 12-in refractor, the Northumberland telescope (http://www.ast.cam.ac.uk/about/northumberland.telescope) during freezing winter mornings. You had to open and rotate the observatory dome using a hand-crank! At last I managed to see the Crab Nebula for the first time. It was, of course, not as impressive as the photographs in the books.

After my studies, I was again sidelined by another passion, I spent the next 20 years or so in a career in computers, ending up as a founder of an Internet service provider during the start of the dot-com craze in 1995. In December 2010 I rekindled my long-lost affair with astronomy by volunteering on Planethunters.org. I am very sure it was in December very near the beginning of the project because I remember working through Christmas Day 2010 writing a javascript planetary calculator.

It’s been two years since the Planet Hunters was initiated and I’m so proud to be a part of its community. We’ve come quite a long way since those early days in December 2010. Back then very few amateur volunteers like ourselves really knew much about exoplanet transit photometry and we were marking every dip in flux as a transit (I guess many people still do!) and we thought that going beyond 5000 classifications was a big deal – there is even a forum topic devoted to this! I won’t mention who he is because he might be embarrassed but he is one of the co-authors and among my most prolific collaborators – he has done over 100,000 classifications!

Since 2010 then we’ve learned much about determining what is and isn’t a planet candidate. We discovered that 99% of transit events weren’t even due to planets. Most of the time they were glitches and even if they were real, they turned out to be false positives, e.g eclipsing binaries (EBs) or contamination due to background blends. I recall being so frustrated by demonstrating that so many of these were EBs that I started a secondary effort to collect what we called unlisted EBs – these were EBs not identified by Kepler’s EB expert Andrej Prsa.

But over the two years we learned how to separate a good PC from a false positive. We learned how to use a periodogram and phase plots, what were pixel centroid shifts, how to analyze TPFs, how to pull down Skyview and UKIRT images and how to model a transit light curve accurately.

Although I was named in the PH-1 discovery paper, and as exciting as that discovery is, I feel that was just happenstance. My more important contribution to the Planet Hunters initiative has been in collecting, compiling and curating the efforts of the community – In the last two years the Planet Hunters have turned up a lot of potential PCs that seemed to me to be real, and by applying all the methods and techniques mentioned above I eliminated all those that failed the tests. We were disappointed a few times when many of these discoveries were overtaken by events. I recall that the list was pared down from over 50 PCs down to 20 when the February 2012 Kepler paper was released (Batalha et al 2012). But I realized that if over 30 of our independent discoveries were real PCs, that fact alone vindicated our efforts. Slowly that list went up to beyond 30 and then reached 40 PCs. In May 2012, another paper by the Princeton team (Huang et al, 2012) took out another chunk of our PCs, but we continued to persevere and by the time the data releases of July and October came around, we had even more PCs to consider. I spent the last quarter of this year rounding these up and characterizing them.

I would not have been able to do this with the help and contribution of the community. I’ve been very privileged to work with some of the smartest and dedicated citizen scientists on this site. I tried my best to follow up on every e-mail and private message you sent me – please keep them coming!

Daryll LaCourse

I’m a Canadian aerospace machinist and amateur astronomer living in the Pacific Northwest. I prefer working with Kepler data to backyard stargazing as heavy clouds and rain can’t interfere with the former.

I am very pleased to see the release of the fifth Planet Hunters discovery paper and the addition of PH2b to the family of confirmed exoplanets. Every volunteer that has participated in the Planet Hunters project thus far has played an important role in the efforts that led to the identification and consolidation of this latest candidate list, which includes a stunning array of potential habitable zone prospects. It is impressively difficult to confirm that a Kepler candidate is a bona fide exoplanet rather than a false positive; thanks to the meticulous follow up work of Ji Wang and the rest of the PH Science team we can say with confidence that these 43 candidates are very likely the real deal.

It has been a privilege to work with so many talented individuals on PH Talk as these discoveries were sifted from the many thousands of highlighted light curves. The tenacity and resourcefulness of the PH volunteers can’t be understated or underestimated, and I look forward to what we will find in 2013 as the extended mission progresses. There are already new targets of interest popping up on the radar for the team to pursue, and the single/double transit candidates (some of which are mentioned in the new paper) hint at a hidden population of long period exoplanets that have yet to fully reveal themselves to us. How will our own solar system eventually fit into this widening hierarchy of possible arrangements and configurations? How common are exoplanets within the habitable zones of Sun-like stars? These questions may not be resolved quickly, but the discovery of every new candidate brings us closer to definitive answers. Experts in the field have speculated that the first true Earth analog candidate may be found this year, which will be a very exciting and historic milestone. I don’t think it is a huge stretch of the imagination to consider that with some sharp eyed luck, it may even be found by one of you!

Hans Martin Schwengeler

I’m a regular user (zoo3hans) on PH, more or less from the beginning two years ago. My name is Hans Martin Schwengeler and I live near Basel in Switzerland. I’m 54 years old, I’m married and we have two children. I’m a mathematician and work as a computer professional. I like to advance Science in general and Astronomy in particular. I did work a few years at the Astronomical Institute of the University of Basel (before it got closed because they decided to save some money…), mainly on Cepheids and the Hubble Constant (together with Prof. G.A. Tammann). Nowadays I’m very interested in exoplanets and spend every free minute on PH.

I’m pleased to hear that I’m going to be mentioned as a co-author of the PH Habitable Zone (HZ) candidates paper. My motivation to participate in the PH project is not really to “name” a planet or such a silly thing, but to advance Science in general and Astronomy in particular. Probably I’m just a curious fellow, although I’ve got named “a cold precise German” on PH Talk by someone (actually I’m Swiss).

I think we have a few very good cases of fine planet candidates collected over the last two years, a few of them even in the HZ of their host stars. Kian Jek (kinjin) has made a good list, many other PH users have also contributed a lot to our collaborative effort. I try to classify as many stars as possible, and also to comment on promising cases, or comment avoiding glitches and other bad features. To examine a promising star, it needs a lot of time. First I just look at the light curve and try to let my brain do the pattern recognition. I actually believe it might indeed be superior to computer algorithms to discriminate between real transits and just glitches or processing artifacts. In my experience it only works down to about 2.0 R_Earth planets, below this border size they cannot be detected anymore just by eye without prior detrending of the light curve. Second I do therefore download the FITS files from MAST and detrend roughly the light curve. Further inspection of the whole Q0-Q13 detrended light curve often reveals already if it might be an interesting case or not. If I suspect a regular signal (i.e. a well defined period) is present in the data, then I try a periodogram to see if the potential transit looks symmetrical, U-shaped and so on. Also important is to check the sky view. We are dealing with stars on the sky after all.A bit frustratingly often it’s just contamination by a nearby background star. Of course I post all findings to the PH Talk pages, so others can profit from the work done so far, and to get their opinion about the case.

Although I have classified over 30000 stars so far, even I select sometimes
a glitch for a transit. It’s not an easy “game”, but rather addictive I think. I also like the teamwork aspect of the PH community. It’s great to get help from the
“specialists” out there who can do contamination vector determination, Keppix series analysis, transit curve fitting and much more. I’d like to thank them all for their great help. I thank also Meg for her great effort to vet more promising exoplanet candidates. PH is a great project!

Yours,
Hans Martin Schwengeler (aka zoo3hans)

Light curve of the week

This week we have a beautiful Delta Scuti variable that shows both primary and secondary eclipses caused by a second star. The beat-like pattern that we can see in the light curve is due to the star pulsating at two very similar, but slightly different, frequencies. Have you seen any more of these on Planet Hunters TESS?

LC-of-the-week-53122807

The Kepler in TESS

By the end of September, the first science grade K2 observations from Campaign 0  should be  made available to the astronomical community and the public. Stayed tuned to this space for updates on the data release and how we’re making Planet Hunters ready to accommodate the K2 observations. While we eagerly await the public release of the first full science grade data from K2, I’ve been thinking about how K2 serves as a stepping stone to TESS, which is expected to launch in 3 years from now.

Over its 2 year mission, TESS is going to monitor ~200,000 of the  brightest stars across the sky for the signs of exoplanet transits by taking measurements of the stars’ brightness every 2 minutes. Most of these stars will be observed for only  27 days in total (though some patches of sky will be observed longer –  see the expected sky coverage plot below) , but the worlds discovered around these bright stars, unlike most of the Kepler planet candidates and confirmed planets,  will be able to be followed-up using ground-based techniques and technology as well as from the space-based James Webb Space Telescope (JWST). This will enable astronomers to probe the composition and structure of these planets’ atmospheres as well as their bulk composition.

Expected TESS sky coverage from Ricker et al. (2014)

 

One thing that I hadn’t appreciated from TESS was the engineering images  it will take in addition to the 2 minute light curves. TESS will target a small number of bright stars at a 2 minute cadence,  but every 30 minutes TESS will take the equivalent of a full frame engineering image across its  roughly 2000 square degree field-of-view. These means we basically get the equivalent of Kepler observations but with blurrier vision (Kepler had pixels that covered 4 arcseconds per pixel. TESS’s are much larger covering 21 arcseconds) and 20x more area. Below is a simulation generated of what a subsection of one of these engineering images might look like from a presentation by TESS principal investigator George Ricker at NASA’s Exoplanet Exploration Program Analysis Group (ExoPAG) meeting back in January.

TESS_full_frame_simulation

Simulation of a portion of a TESS full frame engineering image – Image credit: TESS Team take from George Ricker’s January 2014 NASA’s Exoplanet Exploration Program Analysis Group (ExoPAG) presentation

We know from Kepler that it is possible to detect a plethora of exoplanet transits with 30 minute observations, so there is an exciting prospect of mining the engineering images. With the science that has already been done with Kepler both in the field of exoplanets and other astrophysics,  the TESS engineering images will no doubt be a treasure trove of data waiting to be tapped into.Before Kepler the only star that had been monitored to such precision and cadence was the Sun. Kepler has changed that, but TESS will take it to the next level.  With the Kepler-like quality of the engineering data, it means that if you don’t like the stars the TESS team decided to target, anyone can do an exoplanet search on other stars in the TESS field among other searches and studies like looking for supernovae or cataclysmic variables. There is a wealth of science to be mined out of the TESS full frame images, and I think there is a potential for citizen science (and likely Planet Hunters) to play a role in utilizing these observations to their fullest.

If you’re interested in learning more about the TESS spacecraft , camera design, and mission goals you can check out this paper by the TESS Team which is where I got the information for this post.

An Unusually Active SU UMa-Type Dwarf Nova

Screen Shot 2014-04-19 at 3.39.48 PM

Taichi Kato of Kyoto University and Yoji Osaki of the University of Tokyo recently published a paper on an unusual dwarf nova spotted by Planet Hunters’ volunteers that was contaminating the photometric aperture of a Kepler target star. A dwarf nova is a binary star system where one of the pair is a normal star and the other is a white dwarf. The objects orbit so closely that material from the  star is falling onto the white dwarf with an accretion disk of material around the white dwarf. The light from the system is dominated by the accretion disk. Thus changes in brightness reflect the temperature and state of the accretion disk.  This is the 2nd Planet Hunters dwarf nova/cataclysmic variable find to be published in the astronomical literature. Congratulations to the volunteers involved.  The first Planet Hunters discovery  paper was published in the Fall of last year, and you can read more about that object here.

Drs. Kato and Osaki found the discussions about this light curve from  a volunteer curated blog that highlights interesting finds from Talk and the Talk thread about this interesting source . They went on to follow-up the find and  further investigate the dwarf nova combining  ground based,  space-based telescope data, and the Kepler light curve.  They found that this dwarf nova exhibited unusual features in the light curve (brightness of the accretion disk) for having a very short orbital period of the companion star.

Congratulations to all involved in this intriguing find. You can read about the study in detail with the preprint of the paper available here.

 

Tales from Waimea Part 4 – Observing Report

This is the  second half of  part 4 of my  Keck NIRC2 observing log. (See Part 1 and Part 2, Part 3, and Part 4a).

The night you’re scheduled is the night you have, and you only worry about what the weather and conditions are when your data is being taken. Sometimes you get the only good night in the entire month of other observing runs and sometimes you get the day it rains.  You might have awesome weather and your instrument malfunctions  costing you hours as the operator and support scientist try to troubleshoot it. That’s the gamble with observing and part of the reason I love it. I’ve spent my share of time staring at humidity sensors trying to will them down to the threshold for the dome opening with no avail. You have to deal with what the night throws at you whether it’s bad weather, amazing conditions, or instrument malfunctions. If  I don’t get the conditions I want, it’s tough luck for the observer. That’s it for the semester, and you’ll need to try again and apply during the next the call for proposals. That’s the gamble of an observing run.

So I started the night doing really bright targets and sorting instrument commands  and forgetting and remembering to open the camera shutter and the appropriate dither command and offset to use as I got situated because the Kepler field wasn’t high enough in sky . When I got on to the Kepler field, I took the first test image to sort how long  the integration should be . I’m in the linear regime (which means what it sounds like. It’s the range on the detector where a photon hitting generates X electrons on the camera CCD. If I have too many counts already on the detector, then this can cause the CCD to switch regimes where it doesn’t generate X electrons any more per photon and that means you don’t know how many photons from the star you actually received) so if I want double the counts I double the exposure time. I do that and I saturate the detector (where there are too many electrons due to photons hitting a given pixel on the CCD that they  spill over onto surrounding pixels). Um…. then I go back to 4 times less and I get the peak counts I got with my first exposure (which was twice as long! What gives?).  I call  over Marc my support astronomer  because something’s up. (he was awesome and really helped me to get familiar with the instrument and get feedback on what the AO system was doing given the conditions. Thanks Marc!) o Either I’m doing something wrong or something’s up. We go through the same logic. Okay let’s double the exposure. Now we get the same peak counts as were on the previous exposure that was half as long. What’s going on?

It was perfectly clear at the summit above Keck last night, but the turbulence in the atmosphere made it a constant struggle last night. The adaptive optics system corrects for the effects of the atmosphere and reduce the smearing of the star on the CCD detector, but if you’re seeing (how big the stars appear in your images due to the atmosphere smearing) is changing  faster than the AO system can keep up and by a wide range the AO struggles to keep up. That’s because the wavefront sensors measuring how the light is hitting the telescope and direct the mirrors to deform to compensate, but that correction is no longer correct and the seeing is now something different, so you’re get a lag. I still get correction but it means that the counts in the pixel wells of the CCD that the camera actually measures are changing rapidly as the size of the star is oscillating back and forth. Not good news.

Here’s the seeing monitor from Mauna Kea for last night. You can see it was just rapidly oscillating and going towards big values. Average seeing on Mauna Kea in optical is ~0.8 arcseconds.

20130629.wrf-vs-mkam.timeseries

Red and blue points are from different elevations and you can see how widespread the points are in a short period of time. The absolute value isn’t necessarily what we measure on the telescopes, but we see the same relative changes

I’m the observer it’s my call what to do. So as Marc is explaining this could be kinda AO lag and the fact the seeing is just rapdily changing. I look at my target list notes and see that this Kepler star is at the mid range  of the Kepler Input Catalog magnitude range. It’s 13th magnitude (it was high priority) but I have a few brighter stars that are 10th magnitude (in astronomy lower magnitude equals brighter star).  The AO system is using the target to do the corrections, so if it’s not getting enough photons to adjust quickly then maybe going to a brighter star will help. So after a bit of playing around with different setups, I make the call to move to a 10th magnitude star on my list.

The same thing is happening but we’re getting better counts and the AO system seems to behaving  a bit better. So that’s it. My observing plan is out the window.  I decide targets aren’t going to get observed by priority but in order of magnitude working my way from brightest to fainter going from 10th, than 11th to 12th, and knowing I’m probably going to skip all the 13th and 14th magnitude stars. I had been mulling getting two colors (J and Ks) for each target before the start of the night. I ultimately  decide to only get Ks, and J will only be if I see a faint companion in the image. The conditions could get better, and then I’d be in business. If they do, I’ll move on to brighter targets and adjust the where I’m moving Keck to next, and the seeing did improve in value (it was still varying by the same amount) so I could get 11th and 12 magnitude stars later on before it went back to being bad right before the Kepler field set.

I can take lots of short exposures but taking lots of short exposures and reading them out has a big overhead or I can take a bunch of short exposures and coadd them together in a single read out. I go for the latter after consulting Marc. I decided that saturation is at around 10000 counts, if I can keep the counts around 2000 even if the seeing is causing flucuations by a factor of 2-3 I’m still well in the linear regime and can use the observation. I am gambling a bit in that if one of the exposures that get added to together to make the coadd is saturated I’ve ruined that entire image, but I can check to make sure the counts are what I expect for the target peak counts I’m aiming for.

I also decide to do overkill on these targets. Do 3 times as may exposures+coadds at each part of the 3 point dither and pound on the targets (sometimes repeating the dither pattern again) to try and get useful photons. This is because if there is no contaminating faint star visible, we want an estimate of how bright of a companion we could see. I’m already getting lower counts than expected and the seeing is smearing the stars out over more pixels with additional readnoise and sky background, so that decreases my sensitivtiy. I don’t want to find out that all my observations were useless because they didn’t go deep enough to detect any possible stellar contaminators around these stars.

At this point, all I can do is crank the music up, drink more caffeine,  and fight on through the rest of the night. Every target I spend several minutes taking test exposures getting a feel for the fluctuation in counts, and trying to get the peak counts in my goal ~2000-3000 counts and make sure that that exposure doesn’t seem to be giving me the danger non-linear regime counts. Then take the coadded exposure, see what the counts are and  does the average peak counts divided by the number of coadded exposures give me back around ~2000-3000 counts, if not I need to readjust. I also look at the shape of the star (or the point spread function PSF), if one of the images saturated it should start looking funky).

I can’t help going back and trying to think about where I wasted time, what I should do differently for the next time on NIRC2 and how to be better  for the next observing run. Ultimately I made a decision, on what to do for the observing scheme. Some of that came from gut feeling from my past experience observing. Things I’ve learned from watching  more senior observers who trained me when bad nights happened, when things went wrong, and asking questions during the observing run.

But did I make the right call?  Did that give me anything useful? I think there are moments I won the battle (but not the war) and the counts are linear but only fully reducing the data will tell. I’m planning on trying to do it myself, so that will take some time. I know there’s at least one source with a neighboring star that’s roughly 10% fainter than the Kepler star that I could see at one point in the night, and I managed to keep two filter band observations, to get the color so we can estimate the contaminator’s brightness in the Kepler magnitude. So I’m hoping those observations will be useful.

It’s one of those frustrating nights where all you can do is keep collecting photons, and try to deal with Mother Nature the best you can.  A big thank you to my operator Joel, who was super knowledgable, happily answered questions,  and really helped  make things go smooth once  I was on my own despite the variable weather conditions.

Ultimately, we’ll have to wait and see what the reduced data looks like.

PS. Chris posted my tour of Keck Remote Ops II yesterday, if you want to see what it’s like in Keck HQ.

Awesome People: More from ZooCon1

Today we have a guest post by Jules, fellow Planet Hunter and zooite who attended the ZooCon1. Jules is a lead moderator and blogger for the Solar Stormwatch and Moon Zoo forums as well as a volunteer on the Zooniverse Advisory Board.

Just back from the very first #zoocon1 in Chicago. I attended as a volunteer on the Zooniverse Advisory Board. As Meg said it was a chance for the science teams from new projects to meet with and learn from representatives of current projects and for everybody to meet up with Zooniverse techies and developers. It made sense then for some of the “old hands” to present an overview of their own projects. Meg’s Planet Hunters talk was particularly interesting as it highlighted the value of Talk and the great collaborative work being done there by volunteers.

A brief foray into data reduction showed the kind of work necessary to make the clicks usable. For example, there are 5,508 stars with possible transits. Removing all pulsating stars, which can be mistaken for transits, reduced the number of candidates to 3,404. Further examination of these transits reduced the pool further to 77 transit candidates – a much more manageable number.

Here’s Meg in action demonstrating the light curves of different sized planets.

The discoveries Meg highlighted included a slide showing 4 planet candidates missed by Kepler one of which is being re-investigated because of the work done by Planet Hunters. Kepler 16, the circumbinary system, also got a mention as did the impressive volunteer-led analysis on cataclysmic variables and heartbeat stars.

Old Weather, Mergers and the Milky Way Project were also put in the spotlight. Afterwards someone from one of the new projects told me how amazed they were that volunteers would want to do more than just click and another told me that they found the Planet Hunters story particularly inspiring and wanted to know how Planet Hunters had attracted these “awesome people.”

Well that’s Citizen Science for you. Volunteers come with a great mix of interests, skills and the knack of finding treasure!

Update on Dwarf Novae

Today we have a guest post by fellow Planet Hunter Daryll (nighthawk_black) updating us on the search for dwarf novae and cataclysmic variables. Daryll’s here to talk about a dwarf nova candidate found in PH Talk.

Hi Planet Hunters,

Following the guest post from GO Director Martin Still, a review of light some light curves discussed on PH Talk turned up  an interesting target somewhat similar to the serendipitous Dwarf Nova known as NIK 1. First noted by myself and several volunteers as a possible cataclysmic, we believe this to be another SU UMA type variant with over 50 quasi-periodic brightness changes observed and a defined superoutburst,  in the public Q6 data.

The activity is not visible in all quarters. An examination of the accompanying target pixel files (these are files created by the Kepler processing pipeline that show the brightness over time for each of the pixels that are added up to make a Kepler light curve and those surrounding that don’t go into making the light curve – they can help you see if the features in the Kepler light curve come from the target star or something nearby that is contaminating the target’s star aperture) reveal that the true source of the dwarf nova candidate lies in the background and likely originates from an adjacent source tagged as KID-11412049, leaving how much activity we see in the original light curve dependent on the differing aperture pixel masks used for each Quarterly roll. Unfortunately it does not appear to be an eclipsing arrangement nor has it displayed any transiting circumbinary companions.

We asked the science team to take a look at this star and they think it looks like a good dwarf nova candidate. The PH science team has applied for Directors Discretionary Time seeking additional observations in the coming Quarter (we’re all waiting to hear back if the Planet Hunters proposal has been approved) to learn more about this system including its outburst supercycle, accretion disc stability and component compositions. Early analysis indicates high mass transfer with a notably short orbital period of 76 minutes; a GALEX survey shows this location also appears to be associated with a UV source.

Screening out background binaries from transit candidates is something the community has gotten pretty sharp at and I believe more of Martin’s missing Dwarf Nova will turn up. If confirmed, this will be the 5th Superoutbursting DN in the Kepler FOV and the 17th total, so well done and keep up the eagle-eyed hunting!