Epsilon Aurigae and Citizen Sky

It's back! The AAVSO podcast for 365 Days of Astronomy is here.

In this episode, I interview Rebecca Turner, project manager for Citizen Sky to find out all about the strange star epsilon Aurigae and the AAVSO’s citizen science project to study it. This will be the largest citizen science research project in history, and the goal is to understand one of the most enigmatic stars in the sky.

Busy signal

Hi, thanks for stopping in. That sound you here is a busy signal. I'm on the road again and have been pretty busy in June between preparing for this trip, writing three Restless Universe podcasts and trying to keep my grass mowed between all the rain showers!

I'll be back to posting to the blog any day. I hope to have some interesting pieces about Charles Scovil, Director of the Stamford Observatory who I am staying with for a few days. I'm going to interview him about the history of the observatory and his role as director. Chaz is also a long time AAVSO member/observer/past president/recipient of the Director's Award, etc., etc. I plan to ask him about some of the colorful and amazing AAVSO people he's known over the last fifty years.

I'll be spending the rest of the week at AAVSO headquarters in Cambridge, MA. With any luck I'll have some interesting tidbits to share about that trip too. So stay with me. I haven't abandoned the blog. I'm just out gathering up some more material.

Carnival of Space #106

The Carnival just keeps going and going and going...

This week's host Next Big Future has put together a fine collection of blogs.

Preferentially placing the pieces about futuristic technology, some of which is here now, towards the front end of the carnival is all well and good.

If you dig a little deeper, you'll find the rest of the entries in Carnival of Space #106 are worthy of investigation also.

Dr. Andrew Drake Interview

Andrew Drake is a Research Scientist with Caltech's CACR (Center for Advanced Computer Research) in California. His astronomical interests are varied, and include exoplanet discovery, microlensing of Machos and other baryonic dark matter, Supernovae/Hypernovae and mining large data sets. He is the principle investigator for the Catalina Real-time Transient Survey.

Because one of the byproducts of the CRTS is the discovery of numerous cataclysmic variables I thought it would be interesting to have him to tell us about the methods and goals of the CRTS team, and what they are doing with all the new science coming out of their survey.

Mike: Hi Andrew. Thanks for granting this interview. Let's start off with a description of the Catalina Real-time Transient Survey, the methodology, it's science goals, and then discuss what your group is doing and what you're learning. So first, what telescopes and instruments are used for CRTS?

Andrew: It is my pleasure. The Catalina Real-time Transient Survey (CRTS) currently uses data from the Catalina Sky Survey's (CSS) 0.7m Schmidt telescope. The CSS team hunts for Near Earth Objects (NEOs) while we hunt for other kinds of stationary optical transients.

Mike: What is the observing cadence and how much of the sky do you cover?

Andrew: The Schmidt has an eight square degree fov and covers the visible sky between -30 and +70 degrees.

However, we avoid the Galactic plane by 10 degrees because of crowding. About 1200 square degrees is observed four times on each of the 21 darkest nights per lunation, to V~20.

Mike: Your interest and the science you are going after seems to relate mostly to supernovae in general and then supernovae in faint galaxies, correct? What are you hoping to learn from the survey?

Andrew: Our interest is in optical transients of all kinds. However, we are particular interested in the rare kinds of transient phenomena that can only be found through synoptic surveys covering a very large area. Two particular types of transients that have become of interest since we started the survey, supernovae in faint galaxies, and hypernovae.

Mike: In order to study these supernovae you need a way to filter out all the other stuff you're not looking for, which includes asteroids, cataclysmic variables, other types of variables, image artifacts, etc. You have to be able to classify objects quickly and accurately. I imagine that is one of the bigger challenges in your work. How do you go about doing that?

Andrew: Filtering artifacts and asteroids is perhaps the most difficult part of the survey. Fortunately most asteroids are known to the depth of our observations and can be removed using the ephemeris files that the Minor Planet Center (MPC) distributes. Additional asteroids and artifacts can be removed checking for motion, or offsets, between images. Even so, there is a balance between missing some real transients with strict filtering or allowing some junk through with looser filtering. We have never tried to filter CVs because we know many people are interested in them, particularly when they are in outburst. To improve classification we follow-up almost everything we discover with the Palomar 60" and also make this data public. Our hope is to obtain fully automated classification network to replace the final classification which still must be done by a person (gathering all data sources, cross-checking and making a decision). We hope our future automated classification will enable rapid robotic follow-up of short timescale transients.

Mike: What results have you found so far in your supernovae studies?

Andrew: One surprise to us was that a large fraction of the supernova we find are in intrinsically very faint galaxies. This is not expected because there is much more stellar mass in large galaxies and nobody has seen this before. We believe the reason this has been missed in the past is that most searches for nearby supernovae follow only a few hundred very bright galaxies. The increased SN rate in faint galaxies appears to be mainly due to an extremely high star formation rate in some low mass dwarf galaxies. One particularly interesting SN we discovered was 2008fz.

Mike: What was so special about SN2008fz? Was this a hypernova? What is the difference between a supernova and a hypernova?

Andrew: SN2008fz was a type IIn supernova discovered by CRTS and appears to be the most energetic supernova ever discovered. Such bright supernovae are often called hypernovae and are proposed to be the result of either the collapse of a massive star like Eta Carinae or an extremely massive population III star. The exact origin of hypernovae is not yet clear as few have been discovered. They up to a few magnitudes brighter thanregular type Ia and type II SN and have also been linked to exceptionally bright gamma ray bursts.

Mike: Now you've developed some tools and resources for amateurs and others to use to follow up on newly discovered CVs from CRTS. Tell us about that.

Andrew: When we classify our detections place them on a number of web pages where we hope people will find and follow them. New bright CVs are among our most common discoveries, although we include known CV outbursts also. As with all our discoveries these are made public as quickly as possible. Our hope was that people would work with us on the discoveries or at least inform us that they are following CVs, as they do with supernovae. Unfortunately, we find that they are taken from the webpages and circulated to email lists where they are quickly renamed and followed and even published under that name. Nevertheless, we are continuing to openly publish the new CV discoveries.

Mike: You're also logging data collected serendipitously on known CVs. Is there a plan to share these observations with AAVSO or other researchers? Is there maybe a project here for the CV section, or perhaps the data mining section, to convert your data into a format that can be periodically entered into the AAVSO International Database?

Andrew: Yes, as we cover a large fraction of the sky every lunation we realized that the data would regularly cover thousands of CVs and other interesting variables. We thought it may be useful for us to provide up to date measurements for known interesting objects so that CV astronomers might follow-up those that that they deem interesting. We certainly hope that the AAVSO will ingest this data.

Mike: So what are the plans for the future? Are you going to expand the project? How long do you think you will continue?

Andrew: Soon we hope to start processing the data from two additional dedicated CSS telescopes that use the same camera setup. There are also plans to expand the fields of the existing telescopes by a large factor. Depending on funding we plan to continue for three more years. Part of our goal is to make all the past CSS data public so that everyone may perform their own searches for variables, etc., among the tens of terabytes of existing images and photometry.

Mike: Well, I wish you the best of luck. Let's do this again some time. You can bring us up to date on what has developed for you and your team, and it will give us an opportunity to thank you for all the interesting CVs you're going to discover for us in the meantime!

Andrew: You are most welcome.

Vote for the best science blog post of 2009!

There is a lot of great science blogging going on out there. The people over at Three Quarks Daily are sponsoring a contest to select the best science blogs of 2009. Details of the contest can be found here.

Just reading the blog posts on this list (click here) will make you realize how much great science blogging is going on. I've found several new favorite blogs and writers!

Results of this public voting round (the top twenty most voted for posts) will be posted on the 3QD main page on June 8, 2009, so you have a few days to catch up on your blog surfing before picking the best of the best.

The ultimate winners of the contest, as decided by Steven Pinker, will be announced on June 21, 2009.

Yes, there are a few Simostronomy posts in the running. But you've read those already. Try some of the other offerings before making your choice. THEN vote for one of my blogs!

Tracking Penguin Poop From Space

This was just too interesting at first glance to ignore when it whizzed into my Google reader.

British scientists studying emperor penguin colonies in Antartica have come up with a clever way of spotting the birds from space. Apparently, the penguins themselves are difficult to make out in satellite imagery, but the places on the ice that they call home for months at a time eventually get pretty dirty. Penguin poop can be seen from space!

"We can't see actual penguins on the satellite maps because the resolution isn't good enough," said mapping expert Peter Fretwell. "But during the breeding season the birds stay at a colony for eight months. The ice gets pretty dirty and it's the guano stains that we can see."

These guys are prety excited about poop. It has helped them locate 10 new colonies of penguins. Now that they know where the penguins are, they can get to the more difficult task of counting the birds in order to track population movements and changes over time. Amazing what you can do with satellites, isn't it?

Carnival of Space #105

This week's carnival has several surprises, not the least of which is the switch in authors of Space Disco, which up until recently was Dave Mosher's gig. Now my friend Ian O'Neill from Astroengine.com has taken on the writing duties for Discovery Space. Whoa, time warp!

There are some really good entries in this weeks space fair, so head over right now. Click here to be transported to the 105th Carnival of Space!

The Frozen Dome

Normally, if I heard or read the words 'Dome C' I would think they referred to the third dome in a cluster of structures at some observatory. Recently, I've come to learn that Dome C is also the name for one of the coldest places on earth, one of several summits on the Antarctic Ice Shelf.

Ironically, there is still an astronomical link. Dome C is considered to be one of the best potential sites for a new observatory on the face of our planet. For one thing, the Sun never gets higher than 38 degrees above the horizon, so there is a lot of night time for observing from the south polar region. Even better, there is almost no infrared sky glow, the air is extremely dry, there is almost no aerosol or dust, and no light pollution. The Antarctic Plateau is the largest desert on Earth, so there is very little precipitation and a very high percentage of cloud-free time. Surprisingly, the wind is also quite mild at Dome C, averaging a mere 6 mph in winter. That is a good thing, considering the average annual temperature is -55C, with lows of -80C and balmy highs in the -25C range. Who needs wind chill when it's that cold?

Most importantly, the seeing is typically 2.5 times better at Dome C than at the best existing observatories. Star images taken through a telescope at Dome C would be 2.5 times sharper and 6 times brighter.

The image on the left is a simulation of a star field as observed from the best existing observatory sites; the image in the middle is the same star field as observed from Dome C. To see as many stars from a mid-latitude observatory, you would need to build a telescope 2.5 times bigger, which would cost ten times as much, and would give the image on the right, which makes the stars look brighter but doesn't improve the sharpness of the image.

Image and text from 'Exceptional astronomical seeing conditions above Dome C in Antarctica', by
by Jon S. Lawrence, Michael C. B. Ashley, Andrei Tokovinin, and Tony Travouillon, published in Nature, 16 September 2004.

Three interesting papers have been released to the pre-print server arXiv.org describing the PILOT program (the Pathfinder for an International Large Optical Telescope), a proposed observatory on Dome C in Antarctica. The first paper presents an overview of the instrumentation suite and its expected performance, a summary of the key science goals and a discussion of the future of Antarctic astronomy.

Paper 2 describes a series of projects dealing with the distant Universe. One potential project that caught my eye is the search for pair-instability supernovae (PISNe) and gamma-ray burst afterglows. These could be our best glimpses into stars formed in the very early days of the Universe. PISNe are predicted to be the product of super massive stars formed in the early history of the Universe. These stars were formed before there were any heavier elements, so their unique chemical composition and masses resulted in a different kind of final disruption of the supernovae progenitors in this era. The light curves of these PISNe are predicted to be have slower rise times and to stay bright for much longer than SN closer to home. This is pretty cutting edge astrophysics, seeing as how no PISN has ever been found.

PILOT could also examine some of the first evolved galaxies and galaxy clusters to inform us of the processes in the evolution of structure in the Universe. They also propose a large-area weak-lensing survey and a program to obtain supernovae infrared light-curves to examine the nature and evolution of dark energy and dark matter.

The ability to do infra-red astronomy from the planet's surface makes PILOT a good match and essentially the only competition for the James Webb Space Telescope in the coming decade.

Paper 3 presents a series of projects dealing with the nearby Universe. Several projects are proposed that examine stellar populations in nearby galaxies and stellar clusters, to gain insight into the formation and evolution of younger galaxies and stars.

Other projects will investigate the formation processes of stellar and planetary systems. Three projects in the field of exoplanet science are proposed. These include a search for free-floating low-mass planets and dwarfs, a program of follow-up observations of gravitational microlensing events, and a study of infrared light-curves for previously discovered exoplanets.

Free-floating low-mass planets; now there is a category of interesting objects. The plan is to examine nearby star clusters to search for planets not associated with stars down to several Jupiter masses. Why would astronomers be so interested in free floating planets? Because typically, exoplanets light is difficult or impossible to disentangle from the light of their accompanying star. If we can find exoplanets free of the overpowering glare of their host stars we can study the chemical composition and atmospheric properties of these planets.

And finally a study of coronal mass ejections from the Sun, and a monitoring program searching for small-scale Low Earth Orbit satellite debris items are also proposed.

The opportunities to do exciting, results-oriented science exploration and discovery from Antarctica is is almost as mind-numbing as the night time temperatures resident astronomers and technicians will have to bear to perform the work.

Constructing, operating and maintaining a telescope at the bottom of the world under these conditions will be another great story. Now that I know about Dome C and PILOT, I'll keep an ear to the ground and let you know when there are new developments.

Double Quasar!

An IAU Circular landed in my email box today with a strange headline I found hard to ignore.

'DOUBLE QUASAR SDSS J153636.22+044127.0'

A double quasar? Wow, that has got to be rare. Is it the first one ever found? How did they determine its dual nature? If it already has a Sloan licence plate name, why are they just announcing this now?

I was hooked. I had to research this thing and get the whole story.

First of all, what are quasars? Where did the word come from and what does it mean?

Quasar is a sort of abbreviation for "quasi-stellar radio source". Its also common to refer to them as QSO's (quasi stellar objects). These are active galaxies at least 3 billion light years distant, some a lot further away. They have massive black holes in their centers that cause them to emit radiation in many wavelengths, including radio. Some have jets emanating from the core, perpendicular to the plane of the galaxy. They look like points of light because they are so far away. But make no mistake, these are mysterious galaxies from the early history of the universe.

Image credit: NASA Education and Public Outreach at Sonoma State University - Aurore Simonnet

Many quasars are variable, so I've been aware of them as observing targets for a long time. In fact, several were given names in the General Catalog of Variable Stars because they were mistakenly categorized as variable stars. BL Lac and W Com come to mind immediately.

Now what about that crazy alphanumeric name? SDSS J153636.22+044127.0

Named objects beginning with 'SDSS' are objects discovered by the Sloan Digital Sky Survey. The numbers correspond to their positions in Right Ascension and Declination on the sky. The Sloan survey has discovered most of the over 200,000 known quasars.

The spectrum of this radio-quiet QSO exhibits two broad emission-line systems at slightly different redshifts in the Sloan Digital Sky Survey optical spectrum, so it was originally thought that this might be a black hole binary QSO. The separation between the two sources is less than an arc second, so very high precision images needed to be taken to distinguish the pair and determine their distance from one another.

Subsequently, measurements taken with the Very Large Array, imaging in the radio regime at 8.5 GHz, revealed two sources, separated by a mere 0.97 arcseconds. The individual sources were too small to resolve. In a paper by J. M. Wrobel and A. Laor (http://lanl.arxiv.org/abs/0905.3566) it was suggested that these two sources might actually be two quasars separated by approximately 5 parsecs, instead of a binary black hole quasar. Images and measurements with more precision would be needed to make the call.

Today the call came in. A multi-national team of astronomers report on a deep K-band image taken at the European Southern Observatory using the VLT and an instrument called HAWK-1. The image shows that the object is composed of two sources at a separation of 1". Both sources consist of a nucleus plus an extended emission. These results strongly suggest that SDSS J1536+0441 is a pair of quasars, separated by 5.3 kiloparsecs, which is consistent with the recent independent finding of two compact radio sources by Wrobel and Laor.

So, is this the first double quasar ever discovered? Unfortunately, no. They are rare but there have been several discovered before. That doesn't make this story any less remarkable for me. I hope you found it interesting.

Arto Oksanen- Finnish Amateur Astronomer Extrordinaire

Arto Oksanen is a Finnish amateur astronomer interested in observing transient objects like gamma-ray burst afterglows, supernovae, novae and cataclysmic variables. He also observes exoplanet transits, and was the first amateur to observe the transit of HD 209458b.

In 2004, Oksanen received the AAVSO Directors Award for his work in variable star research. In October 2007, Oksanen was the first to find optical afterglow of GRB 071010B, which had been detected by the Swift satellite only 17 minutes earlier.

He has also discovered two minor planets (22978 Nyrola and 103422 Laurisiren).

Arto Oksanen is an Internet technology consultant by profession. He lives in Muurame, Finland with his wife Minna and their son Atte.

Recently, Arto has been observing a very interesting eclipsing polar (a highly magnetic cataclysmic variable). We had a chance to talk about just what it is that is so interesting about this star and what his observations may contribute to the knowledge of this system and magnetic CVs in general.

Mike: Hi, Arto. In recent weeks you have been following the very interesting eclipsing polar CSS 081231:071126+440405. How many eclipse timings over how many nights have you now amassed?

Arto: Yes, I have been following it practically every clear night since the outburst, or brightening, was discovered by the Catalina Real-time Transient Survey on the last day of 2008. Since that I have observed a total of 48 eclipses during 19 nights.

Mike: What telescope or telescopes are you using to obtain the data?

Arto: Mostly the 40 cm RCOS telescope of Hankasalmi observatory. It is a very nice telescope on Paramount ME and with a SBIG STL-1001E CCD. Luckily I have got enough observing time for this project. I used the 40 cm Meade LX200 of the Nyrölä observatory for one night, observing simultaneously with the Hankasalmi telescope. Both telescopes are owned by the local astronomy club. I am the president so that helps a bit.

Mike: Are you manning the telescopes in real time, observing remotely or scripting the runs and then going to bed?

Arto: For the Hankasalmi telescope I have been observing remotely. Basically starting the same script every night and the observatory automation has taken care of observing and parking the telescope and closing the dome the following morning. Photometry is also performed remotely, by a self-written script, and the result is written in the new AAVSO format that can be uploaded by a few clicks. Observing the same object night after night is very effortless. At Nyrölä the dome is manual, so the observer has to stay there to keep the dome slit aligned with the telescope.

Mike: Can you give us an update? Is the outburst over, have you been clouded out, or are you still collecting data?

Arto: I had to stop observing at the beginning of May. Our skies got too bright for observing then. The outburst seems to continue so, I hope other observers with more southern locations will follow it. OT_J0711+44 will be in conjunction in July so the observing season is soon over for everyone, but hopefully it will remain active for fall when it will be on the morning sky.

Mike: From your location in Finland, how many hours of darkness do you get this time of year? When do you lose nighttime completely, and when does it return for you?

Arto: At this time of year (mid May) we here at 62N latitude don't get any dark hours, just a short twilight that allows us to observe bright targets on southern half of the sky. The observing season starts again in the beginning of August or so.

Mike: Are you collaborating with other astronomers to do a paper on this star? If so, who?

Arto: Yes, there has been lots of interest by professional astronomers. I am collaborating with three astronomers: Pasi Hakala from Finland, Boris Gänsicke from England and Ivan Andronov from Ukraine. Each of them is preparing a paper of this star.

Mike: Can you explain how the light curve gives clues to the geometry of this system?

Arto: OK, I will try. It is obvious that this is an eclipsing system so there are two stars and that the orbit is aligned so that the stars eclipse each other. The eclipse is very deep and very fast so the eclipsed body is much brighter and very small in size. It was found very soon that the system is a polar variable, a cataclysmic variable with a very magnetic white dwarf. The strong magnetic field does not allow the accretion disk to form but directs the accretion stream to the magnetic poles of the white dwarf. The eclipse ingress and egress are extremely fast, too fast to resolve even with 5 second exposures so the light emitting region on the white dwarf is very tiny.


Mike: What do you think is happening to the accretion stream as the outburst evolves?

Arto: The stream is like a light switch to the system: when the stream is on the system is bright (high state) and when the stream is off the system is several magnitudes fainter (low state). The star seems to be around mag 18 in low state and mag 15 on high state. The light curve shows a curious dip just before the main eclipse. This is caused by the accretion stream that eclipses the white dwarf. The pre-eclipse dip varies a lot from eclipse to eclipse and is not visible at all when the system is in low state. The bright stream shows itself also on the main eclipses as the eclipse bottom is not flat but fades two more magnitudes after the sudden 2 mag drop during the 7 minute eclipse . I think the accretion is still increasing, the pre-eclipse dips are getting deeper and wider.

Mike: What new science do you think may come from exploring the characteristics of this outburst?

Arto: Probably the most interesting feature is the pre-eclipse dips that gives the (first ever?) opportunity to directly probe the accretion stream. But it needs more observations to model the system properly and making sure of the geometry. The new science is of the accretion stream for sure and probably some more knowledge of the polars as there are not too many eclipsing systems out there.

Mike: Are there any new ideas or conclusions you can share with us, or do we have to wait for the paper?

Arto: From my observations the orbital period is 117 min 10.9 sec and the main eclipse lasts 7 min 15 sec. The eclipse is 4 magnitudes deep. The ingress and egress are shorter than 5 seconds. The eclipse bottom is V (or semi V?) shaped when the star is in high state and flat bottomed in low state. The pre-dip varies a lot from eclipse to eclipse and is visible only when the system is in high state. More detailed analysis will be on the upcoming papers.

Mike: What other objects are you observing right now?

Arto: During this spring I concentrated this star, but managed to observe some other cataclysmic variables (AM CVn, QZ Vir, CP Dra, a blazar (0716+714), a few Gamma-ray bursts and confirmed a supernova.

Mike: Thanks again for taking the time to share with us.

Arto: You’re welcome; it was a pleasure.