Precursor To An Outburst?

Dwarf novae are compact binaries where one star is a sun-like star and the other member is a white dwarf, orbiting so close that it is literally stripping the outer atmosphere off its partner. The material streams over to the white dwarf but can�t slam down to the surface. Instead, it goes into orbit around the white dwarf, forming what is known as an accretion disk.

Image used with permission. Copyright Mark A. Garlick. Do not use this image without permission.

Eventually, the accretion disk builds up enough material to become unstable. The disk material falls down onto the surface of the white dwarf, causing a thermonuclear explosion that releases all kinds of energy across the electromagnetic spectrum. Optically, we see these as sudden brightenings of several magnitudes in a matter of hours. These outbursts can last from days to weeks. The system eventually simmers down into quiescence and the whole process starts over again.

The majority of these binaries have periods measured in hours. Think about that for a second. Imagine a white dwarf racing around our sun in a few hours, so close it is stripping material from the surface. Everything about these systems is extreme.

Some dwarf novae, like SS Cygni, go into outburst every couple weeks. Some may take years or decades to build up enough steam to explode into outburst. No one knows when the next outburst will occur, making these a favorite target for amateur astronomers to monitor on a nightly basis.

Occasionally, one of these cataclysmic variables will tip its hand to an upcoming outburst, by becoming active a week or more before the big event. Sometimes they will actually have a minor precursor outburst, fade to quiescence and then go into a major outburst.

Over the last couple nights, several UK observers have reported an increase in the quiescent level of V630 Cas. It has been measured peeking its head into the 15th magnitude range, slightly brighter than its normal quiescent magnitude around 16.5V.
V630 Cas is rare example of a dwarf nova with a long orbital period. Its period is measured in days, not hours.

The last recorded outburst of V630 Cas was in 1992, and lasted about three months from beginning to end. That is a long time for an outburst to last! The only other recorded outburst was in 1950. Obviously, outbursts of this system are very rare, so astronomers will be excited to catch every last detail from beginning to end of the next outburst.

This current 'activity' could be the precursor to an upcoming outburst. Observers will be paying close attention to V630 Cas in the coming weeks to make sure that a rare, and possibly long, outburst isn't missed.

I�ll let you know what happens.

Comet Simonsen

I don't observe comets very often. Unless they have reached naked eye brilliance and sport a magnificent tail, they're just not that exciting to look at. Most are faint fuzzy balls with no real tail to speak of; not what most people picture in their minds eye when they think of a comet.

That said, it would still be pretty cool to stumble upon one in the course of an evening observing variable stars. I spend a lot of time out under the stars with my eye to the eyepiece. After years observing variables, most of the star fields have become very familiar. I've seen lots of unexpected things- meteors streaking through the field of view, asteroids masquerading as new stars, satellites and aircraft blazing through the field, but I've never happened upon a comet.

Tuesday night I was working my way from Auriga, Canis Minor and Gemini heading to Cancer. Cancer has a disproportionate number of cataclysmic variables for such a small, faint constellation, so I always look forward to that part of my program. But just before I get there I make a little side trip to Hydra. I can only view faint objects to a certain angle above the horizon, and much of Hydra is just too low for me. So I only have two stars I observe in Hydra.

When I pointed the scope to the first one, CT Hydra and put my eye to the eyepiece everything seemed normal at first. CT Hya was too faint for me to see, so it was not in outburst. I checked my usual comparison stars to see how faint a limit I would record in my report. When I glanced toward the 14.0V comparison star I was shocked to see a fairly bright fuzzy blob just to the SE of it!

I moved the telescope ever so slightly, back and forth, to make sure it wasn't a reflection in the EP, and it stayed right where it was in relation to the field stars. I looked at it for a while and decided it was real enough, so I took the paper chart out of its page protector and drew the position and size of the object, as accurately as I could, in relation to the stars on the chart.

At this point, I was intrigued enough to go inside and try to identify just what comet this was that had intruded into my night of variable star observing. I fired up my planetarium program and asked it to show all comets within a degree of CT Hya. Nothing. I logged into the Minor Planet Checker website, typed in the coordinates of my 'comet' and searched for anything within 30'. Nothing.

How on earth did the surveys miss anything this bright this close to the celestial equator near new moon? Did I just discover a new comet? Now I was getting excited.

I emailed several observer friends and asked them to take CCD images of the field for confirmation. Then I logged into Global Rent A Scope (GRAS) in New Mexico, and fired up scope 4 which has a pretty enormous field of view for a CCD. I scripted it to run and take a 240 second exposure with a clear filter. If it was real, it should show up as a bright fuzzy object near the middle of the image.

No one got my message until much later or the next morning, but I did get two images of the area from the GRAS scope. I examined them online and was disappointed to see nothing where I expected a bright comet to be.

In the time it took to check for known comets, email friends, start the telescope, cool the CCD, autofocus, slew to the target, take images and upload them to the GRAS site, it had begun to cloud over here at home. I didn't get a second chance to see what was going on in the eyepiece of my telescope. I chalked it up to mysteries of the universe and turned in for the night. I also never made it to my variables in Cancer.

Thursday at lunch time, I was working on my data from Sonoita Research Observatory (SRO) in Arizona, so I had my photometry software up and running on the computer. I decided to download the images I took of the CT Hya field to see if I could detect the variable and submit a positive faint observation of it. When I pulled up the images on the screen and zoomed in, there was my comet!

It was a lot fainter than I expected to see, and it had moved considerably from the position I indicated on my chart, but it was there in both images, and it looked like it had moved in a straight line away from my original sighting between exposures.

I got excited all over again. Here was proof. I had pictures of Comet Simonsen! Not being an expert in cometary images, properties or motion, I emailed my images to several people, some of them experts in CCD imaging and photometry, for feedback. Was this a comet? Can they move this far in an hour or so? How come its so faint? Did I do something wrong? Or is this an artifact on the images?

I was hoping it was a comet. My comet...Comet Simonsen...discovered serendipitously while observing variable stars...I could see the headlines. What are the chances I could see something in the eyepiece, take CCD images of it and nothing was really there. I mean, C'mon, man. It's got to be a real comet, right?

I got the bad news later that night and then confirmation that it was "an interesting artifact, but not a comet" again the next morning. Stop the presses. It's not a comet.

I still don't know what I saw in the telescope that night. I'm gonna call it a UFO: Unidentified Frustrating Object. I'd have been a lot happier just working my way through my CVs in Cancer that night. As it turns out I missed an outburst of one of my favorite stars, SY Cnc, while I was messing around trying to discover Comet Simonsen 2009.

Stuff happens...

Carnival of Space #91

The Carnival of Space #91 is hosted this week by Brian Wang at the Next Big Future blog.


Nextbigfuture is the Lifeboat Foundation Technology Research News Website. The Lifeboat Foundation is a nonprofit nongovernmental organization dedicated to encouraging scientific advancements while helping humanity survive existential risks and possible misuse of increasingly powerful technologies, including genetic engineering, nanotechnology, and robotics/AI, as we move towards a technological singularity.

Big Eyes on a Big Star

Mass is constantly being recycled in the universe. One of the most common ways recycling is achieved is through stellar mass-loss. All stars exhibit some form of mass loss. Smaller stars can be quite stingy and hold onto their mass by burning away slowly. Other massive stars can lose prodigious amounts of mass each year. The rate at which a star loses mass depends on its initial mass, age, spectral type, luminosity class, rotation rate, evolutionary stage, even the proximity of a companion star.

The first generation of stars consisted mostly of hydrogen and helium. These stars then seeded the interstellar medium with heavier elements, shedding material via massive winds, planetary nebulae and supernova explosions.

This material then became the building blocks for the next generation of stars and planets. Understanding mass loss is essential for following the evolution of single stars, binaries, star clusters, and galaxies.

However, mass loss is among our weakest areas in understanding fundamental stellar processes. In large part, this is due to lack of detailed, direct observations of stellar photospheres and the mass-loss process. High-resolution optical interferometry with telescope arrays is beginning to provide these data, ushering in a promising a new era in mass-loss studies.

The angular resolution that a telescope can achieve is proportional to its diameter. The larger the telescope, the better its resolution. The purpose of astronomical interferometry is to mix signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection.

The Very Large Telescope Array (VLT)

Recently, a team of French astronomers captured one of the sharpest color images ever made. The team members are Jean-Baptiste Le Bouquin and Antoine M�rand (ESO), Sylvestre Lacour and St�phanie Renard (LAOG, CNRS, Grenoble, France), and Eric Thi�baut (AIRI, Observatoire de Lyon, France).

The image was taken over several consecutive nights with ESO's Very Large Telescope Interferometer (VLTI), a virtual telescope about 100 meters across. The result is an amazing image that reveals a spherical molecular shell around an evolved Mira star, T Leporis, 500 light-years away!

Image showing T Leporis' atmospheric layers and the size of the star relative to the diameter of the Earth's orbit.
(Credit: ESO)

Miras are giant pulsating variable stars. Evolved stars like this have used up most of their nuclear fuel, causing them to swell up to enormous radii and become unstable. This internal instability causes them to expand and contract more or less regularly. T Lep pulsates with a period of 380 days, and in the process loses the equivalent of the Earth�s mass every year to space. In the end, all that is left is a white dwarf, the ash of the core, surrounded by the gases lost to space from the star�s wind and tenuous grip on its outer layers. We see these stellar remnants as planetary nebula elsewhere in the galaxy. Our Sun will become a Mira in a few billion years, engulfing the inner planets in its final blaze of glory.

Mira stars are among the biggest factories of molecules and dust in the Universe. Since the molecules and dust are formed in the outer layers of a Mira's atmosphere, astronomers would like to be able to see these layers to better understand the processes of mass loss and dust formation. Until now, this has been all but impossible due to the distance to even the nearest stars. The angular size of even giant swollen stars like T Lep were too small to image from Earth.

�T Leporis looks so small from the Earth that only an interferometric facility, such as the VLTI at Paranal, can take an image of it. VLTI can resolve stars 15 times smaller than those resolved by the Hubble Space Telescope,� says Le Bouquin.

�We were able to construct an amazing image, and reveal the onion-like structure of the atmosphere of a giant star at a late stage of its life for the first time,� says team member, Antoine M�rand. �Numerical models and indirect data have allowed us to imagine the appearance of the star before, but it is quite astounding that we can now see it, and in color.

Obtaining images like these was one of the main motivations for building the Very Large Telescope Interferometer. We have now truly entered the era of stellar imaging.�

400 years after Galileo turned his tiny telescope towards the sky, we can now actually see stars atmospheres directly, using some of astronomy's most amazing new tools of discovery.

Sun Dogs

Not everything interesting in the sky is actually out in space. Sometimes our weather and atmosphere can produce some interesting sights.

Here is a picture sent to me by new AAVSO member, Dr. Douglas Allen of an atmospheric effect called sun dogs. You can see a portion of a circle, the halo, against the sky, and two bright spots either side of the sun. The bright spots are sun dogs.
















Sun dogs are created by hexagonal atmospheric ice crystals refracting sunlight. Sun dogs are visible when the sun is near the horizon and on the same horizontal plane as the observer and the ice crystals. As sunlight passes through the ice crystals, it is bent by 22 degrees before reaching our eyes, so sun dogs always appear the same distance and angle from the sun.

The movement and orientation of the ice crystals determine a sun dog's shape, sharpness, and color. Mottled, wobbling, or tall crystals, generally result in more diffuse or colorful displays. An excellent web page describing sun dogs can be found at the Atmospheric Optics website.

Despite the fact this picture was taken on a frigid, 4 degrees F, Iowa morning yesterday, sun dogs don't require cold ground temperatures. The atmospheric phenomena can be seen around the world in any season�probably even on other worlds. Octagonal ammonia crystals in the atmospheres of Jupiter and Saturn, may spawn quadruple sun dogs!

Speakers Bureau

Another interesting outreach initiative from the AAVSO is the Speakers Bureau. The Speakers Bureau is a service established for people and groups looking for enthusiastic, knowledgeable speakers to provide informative presentations for astronomy clubs, star parties, banquets, Scout Troops, Astronomy Day activities and other public and private astronomy functions.

You can see a list of the available speakers, along with the list of topics they can cover here. This is only a list of topics the speakers have spoken to in the past. If you're looking for something specific, just ask. We can probably accommodate you.

Most speakers are willing to travel a reasonable distance, generally two hours drive from home, free of charge. Reimbursement for speaking engagements requiring more miles and time can be negotiated on an individual basis with the speakers themselves. The speakers' home town and distance they will travel are included on the web page.

To request a speaker for your astronomical function simply send an email to aavso at aavso dot org with 'Speakers Bureau' in the title. We will put you in touch with the individual you request or suggest one for you.

Some of the speakers from the bureau and I will be giving talks at this years Astronomical League Convention (ALCon 2009) in New York, NY this August. If you are going to attend, look me up. I'm always glad to get to know fellow astronomers.


If you are unable to get a speaker for your event due to time, money or geographical challenges, AAVSO also offers a library of ready-made PowerPoint presentations you can use to give a talk yourself. These are available free for download from the AAVSO Education and Outreach Pages.

Send a message to space

I stumbled across this site on Twitter the other day. http://www.sentforever.com/index.cfm

Their ad reads, "SentForever transmits your personal message into deep space. Once that message starts traveling, it will continue for an eternity. If you've ever wanted to give someone special a personal and very unique gift, why not send them a message that will last forever."

The way it works is, you write your personal message and submit it to their website. Then they transmit the message into space via a large radio telescope. They send a certificate to the person you want to dedicate or send the message to, along with a personal tracking number so you can track how far the message has traveled into deep space. You can also receive e-mail updates to find-out when your message passes key milestones if you want.
This service normally costs �9.95 (approximately 20 US Dollars). Right now they are offering free messages, so I tried it out just so see how it works and what you get for your money.
It works pretty much as advertised. I wrote a message to send into space "You are not alone. There is life in the universe," submitted it and had it sent to my wife. The following day, they sent me an email notifying me of the transmission, along with a link to view the progress of my message into space at the speed of light. I checked in as I'm writing this and can see how far my message has progressed to date-

This message from Mike Simonsen was transmitted into deep space on 20 February 2009 at 04:47 UK time. Going at the speed of light, your message has traveled 37,639,662,291 miles to date.

I'm usually not in favor of doing stuff like this. I really have a problem with the companies that sell 'name a star' services. If you've ever had the uncomfortable experience of someone coming up to you at an observatory open house and asking to see 'the star named after my dear departed Aunt Mary', you know why. It's a scam, and one that can hurt people when they are told some anonymous star with an obscure catalog name can not really be named after Aunt Mary, no matter how much money they plunk down.

Then there are the people who sell real estate on the Moon or Mars. If this is done in good faith and humor as a fundraising tool for a non-profit, fine. But if it's done to make a profit off of gullible, uninformed people, I think they should be jailed.

This service though, is something different. These people actually can send a message into space that will travel forever. Sending a message that is verified electronically to a loved one as a gift or Valentine's Day card doesn't hurt anyone.

I can see how this could be used to demonstrate the scale of the solar system, our immediate stellar surroundings and the scale of the universe. How many miles are in a light year? How long will our message take to get to Pluto? How long to catch up to the Voyager spacecraft? How long to get to the nearest stars?

You could write a short eulogy for a friend or relative and have it transmitted into space, or write a message from the heart and send it to a girlfriend or spouse. Just remember, if you're going to send a love note, you can't take it back three years from now when you find out she has fangs and a mental disorder. A tattoo you can remove with some difficulty. This is forever...

And if you're going to send it to your wife, you might want to make your message a little more romantic than mine. Admittedly, I was trying to think of what it is I'd actually want to hear if I picked up a signal from deep space. Confirmation of alien intelligence, for sure!!

Now I may have to spring for the twenty bucks to send something romantic.

Refining the Distance Scale

I scan the new astrophysics papers regularly. I almost always find something I end up downloading and reading, either right then and there, or later when I have time to concentrate. Rarely do I stumble across a paper that I can't take my eyes away from, like a great novel. One of those times when, forsaking all else, you must get to the last page.

Yesterday I found a great paper. What I was most pleased with was the fact it was written in plain English, with good grammar and organization. I understood every bit of it from start to end! That almost never happens. I couldn't stop reading it.

I don't have a PhD in astronomy or physics. I do this because I love it, period. So I often find myself part way into a paper on some astrophysical phenomena that the author is trying to explain, but no lights are going on in my brain. Either the subject is too technical for me to grasp, or the author is writing about things at a level only the top five experts in the world would ever understand. Add the poor English skills of foreign scientists writing in a second language and things can get ugly fast.

At some point I have to decide to either suck it up and plow through, hoping that a light will come on somewhere in the process, or skim through the rest to see if anything interesting develops with the plot.

Rarely do I find myself whooping it up and commenting out loud about the paper in my hands.

Okay, enough teasing. The paper is Absolute Magnitudes of Dwarf Novae: Murmurs of Period Bounce by Joe Patterson. Obviously, the subject appeals to me because dwarf novae are my special area of interest. But let me quote you some examples of why I was so impressed with this paper.

The first paragraph:
"Distance is the sine qua non of astrophysics. A distance estimate is required to convert flux to luminosity, and stellar physics is all about luminosity, not flux. Unfortunately, distances to cataclysmic variables are particularly difficult to estimate, because the dominant light source is not a star, but an accretion disk- preventing straightforward application of physical methods developed for single stars."

That will never be stated more clearly, ever. Yet it has a conversational tone to it that invites you in to take a look around. Remember, this is a scientific paper!

There are some other gems near the beginning that particularly caught my attention.

"In the 1980's available data on dwarf nova eruptions consisted of a blend of photographic and visual magnitudes. But now we have access to searchable variable star records, especially that of the AAVSO. The human eye is the ideal detector for this purpose, since it is immune to changes in technology, and used by thousands of observers. Furthermore, the central wavelengths of the eye and the commonly used Johnson V filter are similar; and both detectors are broad enough to render line emission insignificant."

He gives praise to the observations of amateur observers, the AAVSO and explains why visual observations are scientifically valuable all in one breath! I have a new hero.

I won't spoil it by giving away the end, and if you want to find out what period bouncers are you're going to have to read the paper.

I'm going to print it out on fine paper, have it bound in a nice little cover, and get Joe to autograph it for me when I see him in Tucson later this month at the CV conference, 'Wild Stars in the Old West.'

Job Satisfaction

I swiped this image off Nicole Gugliucci's blog. I liked it so much, I have a copy hanging in my observatory control room now.

Still On The Rise

As a quick update to my blog about V630 Cas, the anticipated outburst is still under way. This is pretty unusual for the types of dwarf novae I normally follow. Three weeks ago we suspected it was going to go into outburst, and here it is still slowly rising.


Most of the time, a dwarf novae would have risen to maximum in a day or two, remained there for a few days and then began to trail off in brightness until it reached minimum after a week or so. Obviously, V630 Cas is a horse of a different color.

AAVSO Podcast- Restless Universe #3

Today, the AAVSO presents its March 2009 edition of Restless Universe on the 365 Days of Astronomy Podcast. This week, Travis, Rebecca and I tell you about the history and activities of the AAVSO, its members and observers. From humble beginnings in 1911 to collaborations with space telescopes today, the AAVSO is involved in the quest to understand the secret life of stars. To learn more, check out the podcast today.

Carnival of Space #93

The Carnival is back on track after the train wreck of last week.

Fortunately, this week's host, Emily Lakdawalla, at the Planetary Society Blog, was able to step up at the last minute and host the affair.

She's done a great job of organizing all the submissions into one cohesive page of entertaining and enlightening articles on space and astronomy.

So head on over to the Carnival of Space for this week, and be sure to come back next week when the Carnival will be hosted here on Simostronomy.

Feast or Famine

I've complained enough about the worst winter ever for observing here at the C. E. Scovil Observatory, so I won't add to the litany of complaints.

But there is plenty of good news to report as winter seems to be loosening its grip on Michigan.
1- The weather has been good lately. It's still cold, but at least the clouds have found someone in Nebraska or Minnesota to bother. They've thinned out here.
2- I finished insulating and paneling the roll-off shed control room. It's actually almost too warm in there at night. I was in shirt sleeves tonight, and sweating a bit around the neck. Outside temperature, -2.3C.
3- Because of the crappy weather I had a lot more time to devote to fantasy football this season, resulting in my winning the championship in two out of three leagues I played in.

Not only did I get the satisfaction of finally beating my son in the playoffs (he has owned me for five years!), I won enough money to by a new CCD autoguider and 80mm guidescope to improve my photometry results. I also bought a new awesome treadmill for the living room. Irene and I can share the miles and smiles while watching all our favorites on DVR.
4- Even though my 12" GPS still can't point worth a damn, its now taking great data once I get it parked on a variable star.
5- The new photometry software, also compliments of fantasy football, is worth every nickel and making life much more enjoyable for me.
6- Not only is my own observatory ramping up the amount of data collected each week, but my request for remote observations from the Sonoita Research Observatory was granted, and now I am getting data 3-4 times a week on my target stars from Arizona.

So we have gone from no observations for November- January to working every free minute to keep up with the glut of data coming in and reporting activity and outbursts of CVs in my program in a timely manner to CVnet and AAVSO.

Like many things in life, sometimes it's feast or famine. This month it's feast.

SimoCowboy Ready to Roll!

Next week is a conference I have been excited about attending for a long time. It's an entire week devoted to my specialty, cataclysmic variables. The list of attendees is a literal who's who of CV research.

The conference is called Wild Stars in the Old West II. This special get together doesn't come around that often. I wouldn't miss it for the world.


From the website:

"It has been ten years since the last North American Workshop on Cataclysmic Variables and nearly five years since the last international meeting on cataclysmic variables and their kin. Of particular interest since these last meetings are new results based on observational platforms such as GALEX, Spitzer, Chandra, XMM INTEGRAL and Swift/BAT, large surveys such as SDSS and planned Pan-STARRS and LSST, smaller but equally important surveys such as All Sky Automated Survey (ASAS), Catalina Sky Survey, �Pi of the Sky�, ROTSE, results from large aperture ground-based telescopes, theoretical advances, and evolutionary relationships of CVs to other binary stars."

I plan to blog about the proceedings and talks, and I'm taking a digital audio recorder to do some one on one interviews with some of the leaders in CV research. These will be turned into podcasts for Slacker Astronomy and Restless Universe.

Sunday is a travel day, and the welcome get together in Tucson. Monday, the real stuff begins. Check back for updates next week.

Yeehaw!

Wild Stars Day One Part 2

Okay, so we still don't find many stars in the CV 'period gap' with orbital periods of 2-3 hours, so in ten years since the last Wild Stars conference, and with all the new CVs discovered and measured in that time, this is a real phenomena.

We find a lot of stars piling up around three hours period and many of these are accreting at very high rates. The secondaries are losing prodigious amounts of mass to their cannibalistic white dwarf companions.

The leading theory explains this gap as the point where magnetic braking ceases and these binaries abruptly stop accreting matter from the secondary to the white dwarf. As these binaries continue to lose orbital energy through gravitational wave propagation they evolve through the period gap from 3 hours to two hours. At this point they've spiraled in close enough for the secondary to fill its Roche lobe and accretion starts up again.

From orbital period (Porb) 2 hours and less the only way the system loses orbital energy is through gravity waves. Typically these stars have low accretion rates and it takes a long time for them to build up enough material in the disk to go into outburst. So the secondaries are not losing mass very quickly, and we'd expect to see another spike in the population of CVs at shorter orbital periods.

One problem is the fact that these systems tend to be quite faint in quiescence, so they are harder to find than their bright actively outbursting friends at the longer Porbs. With the recent results of the Sloan Digital Sky Survey (SDSS) we've uncovered more ad more of these short period low accretion rate CVs, but there is still some debate about whether we have actually begun to pin down the actual spacial density of these objects. There aren't that many faint, short period CVs close to us, so they must indeed be rare objects.

CV theories also predict a minimum Porb of about 65 minutes. There may be something wrong with our models though, because observationally, the minimum seems to be closer to 80 minutes. Either we have a whole bunch of highly evolved, low accreting faint stars out there at 23rd magnitude (beyond the limit of SDSS) or there is something lacking in our understanding of the physics at this minimum threshold for CV period evolution.

To be honest, not much of this is new, or cutting edge astrophysics anymore. A lot of these same issues were being discussed ten years ago. We may have more observations and phenomenology, but we don't seem to have made any significant progress in our understanding of these Wild Stars.

That is a topic I want to interrogate Steve Howell, one of the local organizers, about tomorrow. I'll let you know what he thinks.

Wild Stars -Day One

Much of variable stars research is related to stellar evolution. We have a pretty good handle on how single stars evolve over billions of years. They are born in clouds of dust and gas, contract due to gravity until they reach a critical limit at which nuclear processes begin converting hydrogen to helium and heavier elements. At this point a star is born.

The most important factor in the evolutionary track of a star is its initial mass. Giant stars burn up their fuel quickly and die spectacularly. Dwarf stars live for tens of billions of years, miserly using up their fuel while putting out a conservative amount of energy.

A majority of stars follow an evolutionary path that eventually causes them to swell to hundreds of times their original radius, throwing off layers of their outer atmosphere via stellar winds and from their losing their gravitational grip on the outer layers of their swollen stellar atmosphere. These stars eventually become planetary nebula with white dwarfs at their centers.

These degenerate white dwarf stars are fascinating objects. They do not produce new energy, like stars. They are the remaining ash of the core of evolved stars, slowly cooling through time from their original very high temperatures. They are small and extremely dense, planet sized objects with approximately the mass of our sun squeezed into their small frames.

Things get a lot more complicated when two or more stars in orbit around each other are involved. If the stars' orbits are wide enough, each star may be able to follow its normal evolutionary path for billions of years. However, cataclysmic variables are stellar pairs, typically containing a white dwarf and a swollen M dwarf, in orbit around each other so close that the orbital period can be measured in hours. Mass is exchanged from the secondary to the white dwarf via an accretion disk. This interaction has a profound effect on the evolution of the stars involved.

Some of these white dwarfs have extremely strong magnetic fields. The accretion process is interrupted in part in intermediate polars, or completely in polars (AM Her stars). No real accretion disk is formed. Instead the mass transferred in polars slams down onto a small area at the magnetic pole of the white dwarf, or goes into strange orbits following the magnetic field lines in an intermediate polar.


Fine. We can and do observe all these properties of these binary systems now, along with the outbursts and high and low states of activity CVs are well known for. But, the burning question of the day today was "How do they get this way?"

Where do these pairs come from? Are they born as normal stars in unremarkable circumstances that somehow evolve into wild pairs of objects orbiting each other so closely they are exchanging material? How long does this take? How do they lose their orbital energy, and what is that energy converted into? Even more perplexing is, where do the magnetic fields in CVs come from?

Above: The common envelope explanation for the evolution of CVs from a pair of main sequence stars, to a pair with a Giant Branch star and main sequence dwarf to eventually becoming a white dwarf and main sequence dwarf pair (CV).

The generally accepted explanation is called the Common Envelope evolution scheme. As a pair of stars evolves, changes in the mass of one or both stars affects the orbital characteristics of the pair, and they lose energy and begin to spiral in towards each other. At a critical point in this process one star evolves to the point that it fills its Roche lobe and the pair becomes involved in a cloud of dust and gas shared by both called a 'common envelope'. We believe CVs evolve out of this phase into the semi-detached systems we see as dwarf novae and magnetic CVs.

Just how this happens is still not well understood, and how either star acquires a mega-Gauss magnetic field in the process is an even less understood process. The mystery was framed and discussed in a couple very interesting papers given in the afternoon session. James Liebert pointed out the fact that the Sloan Digital Sky Survey has found over 1200 close pairs containing a white dwarf and an M dwarf, precisely the kinds of pairs we believe are the progenitors of CVs, yet none of them have been found to contain a white dwarf with a strong magnetic field.

Nearly 25% of CVs are magnetic systems so where do they come from if not these pre-CV pairs? In fact, all highly magnetic white dwarfs appears as either single stars or components of CV binaries.

Christopher Tout proposed in the following paper that highly magnetic white dwarfs must be formed as a result of the common envelope phase of binary evolution. He went further to suggest that the single white dwarfs with the highest magnetic fields are the result of a pair of stars merging into one highly magnetic white dwarf from the common envelope phase. And the magnetic CVs we observe, polars and intermediate polars, are the result of systems that almost merge before eveolving into magnetic CVs.

There are also fundamental questions about the evolution of CV pairs. Do these stars continue to spiral in towards each other, reaching shorter and shorter periods? How does accretion and mass loss affect this evolution? How do we explain the well known 'period gap' where there are almost no actively accreting systems with orbital periods between 2 and 3 hours?

A graphical demonstration of the period gap. The vertical axis is the number of known CVs. The horizontal axis is the period in hours (top) or fractions of a day (bottom).

What is so special about this orbital period? What shuts off the accretion process at 3 hours yet lets it re-engage at less than 2 hours. What is the actual period minimum for CVs? Is it 65 minutes, as theory predicts, or is 80 minutes, as observations seem to imply?

There are lots of questions. I hope to get at least some of the answers this week. Stay tuned, and we'll find out together.

The images used in this article are from space artist Mark A. Garlick. Visit him on the web at www.space-art.co.uk and www.markgarlick.com

Wild Stars- Prelude

Travel yesterday was not without problems. After boarding my plane in Detroit, we were informed that the fuel pump that starts the engines was leaking and not working. 45 minutes later, after a 'repair' done on the spot, the plane was pushed out to the tarmac, and nothing...
No engines, no noise, no air conditioning.

Back to the gate, more repairs attempted. Finally the pilot says they're going to 'jump start' !! the engines and then we'll be on our way.

Long story short, we eventually took off two hours late.

My boss, Arne Henden, connected in Detroit from Boston to go to Phoenix, so we ended up touching down in Arizona around the same time and shared the shuttle ride from Phoenix to the University of Arizona in Tucson.

Where the shuttle dropped us off was much further from my hotel than I had anticipated. I did not enjoy walking all the way across campus dragging my luggage in the dry, high altitude desert air of Tucson. After the half way point, I was taking frequent breaks in every shady spot we came across.

The hotel is very nice, and the sympathetic staff assured me I could catch a cab to the welcome reception later that evening, which I did, in spite of the fact that just about everyone else walked.

My world was made right again after settling into my room and having a bite to eat.

The welcome reception was held in the open air second story patio of one of the micro-brewery beer houses on campus. Complimentary drinks and food lubricated the discussions as everyone got to connect or re-connect in the mild night air. I got to meet several of the 'big names' and some enthusiastic grad students.







Above: David Buckley (SAAO) and Steve Howell (NOAO)
Right: front center- Joe Patterson (Columbia University), front right- John Thorstensen (Dartmouth College)

Wild Stars Day Two

You better show up wide awake for these conferences. Tuesday morning we jumped in feet first into the crazy world of AM CVn type stars. This is a rare class of stars that has been garnering more attention lately due to their extremely short orbital periods, (we're talking 10-60 minutes here), and the fact they are sources for low frequency gravitational waves.

AM CVn spectra are totally devoid of Hydrogen lines. They show a rich Helium spectrum along with processed heavy element lines. This makes them exciting to astronomers because supernovae spectra don't show hydrogen, so these stars may be supernovae progenitors. If you want to get grant support or telescope time these days, it helps if you're proposal has something to do with the sexy topics of exoplanets, supernovae or dark matter.

There are several proposed channels for the evolution of these stars. By the third paper of the morning we had heard about all the possible ways these stars can be born and how they may die as helium Ia supernovae. AM CVn's are thought to form via 2-3 different "channels".

1-A detached white dwarf (DWD) system, formed through a series of Common Envelope evolutions, shrinks as a result of angular momentum losses due to Gravitational wave Radiation (GWR). Eventually, the less massive star fills its Roche radius and mass transfer commences. The system then evolves to higher periods due to redistribution of angular momentum.

...or, 2- a low mass helium donor transfers mass to a white dwarf accretor. The system passes through a minimum in period of ~ 10 minutes. The period increases after this minimum and mass transfer keeps falling. During this process the helium donor goes from being a non-degenerate to a degenerate star.

...or , 3- they may evolve from cataclysmic variables with evolved donors. After significant mass loss, the exposed Helium core of the donor in a CV evolves similar to #2 Helium star track.

What's truly amazing, and mind bending if you haven't had enough coffee, is the fact that we just can't find helium core white dwarfs right now. Since these may be members of binary progenitors for both supernovae and classical novae, astronomers are forced to model how these stars contribute to colossal cosmic explosions using math, physics and imagination. Then they have to figure out a way to explain it to other astronomers and survive the question and answer session after they present their talk.

Kudos to graduate student Ken Shen for his paper on Unstable Helium Shell Burning on Accreting White Dwarfs. This young man knows his stuff and can give a presentation. I predict good things for his future.

After lunch we started hearing talks closer to my areas of interest. I already mentioned the awesome 3D Gas Dynamic Modeling movies shown in the talk given by D.V. Bisikalo. Then Don Hoard talked about Dusty Toads, a topic we have seen here before a few times.

SW Sex stars is another class of stars I wanted to learn more about. It seems that all eclipsing nova-like stars in the 3-4 hour period range are SW Sex stars. But eclipses are simply a line of sight effect, so they can't be considered a pre-requisite for inclusion in the SW Sex club. So Linda Schmidtobreick and her colleagues looked at a large sample of non-eclipsing stars in the 3-4 hour period range to see if they had the rest of the required characteristics for inclusion in the SW Sex category. What they found was that most of these stars are indeed SW Sex stars. Remember, the CV period gap is from 2-3 hours, so these stars may represent an important group of stars, with periods just above the gap, in a high mass transfer state which may cause the binaries to lose contact and stop accreting as they evolve through the period gap.

Boris Gaensicke has become a rock star in the CV community. It is almost unfair to have him start the final afternoon session and then expect three more people to deliver talks on essentially the same topic- 'recent results of CV population studies and the space density of classes of CVs'. I'm just glad it wasn't me, because that is exactly what happened.

Boris hit it out of the park with his presentation. He presented results from the new CVs discovered by SDSS. The main points of his talk are that we've now determined where the missing 80 minute period spike stars predicted by CV theory are. Paula Szkody and SDSS have found them down to around 19th magnitude. They do exist, and they are significantly different from the rest of the CV population.

The spectra of the majority of these stars reveal slowly accreting, white dwarf dominated, WZ Sge-like stars. But, we have still not found the "period bouncers"; those stars with periods less than 80 minutes that are near the predicted 65 minute limit where these CVs will begin to evolve back to longer orbital periods. Boris says they will be found if we just dig another couple magnitudes deeper, and I believe him.

Wild Stars Pictorial Review

Steve Howell, head cowboy, and coiner of the famous acronym TOADs (tremendous outburst amplitude dwarf novae) welcomes everyone to the conference and explains where the bathrooms are.

His other main task for this conference seems to be getting everyone who wants one, a receipt for their expense reports. Poor Steve.

His poster on magnetic CVs has an awesome visualization. I'll try to get permission to reproduce it here. It is way cool....err, I mean hot.




Chritsian Knigge opens the paper session by reviewing what we know about the secondaries in CVs and their role in the evolution of these systems.

Check out the visualization of that bloated, star spotted, crazy looking secondary. Wild stars indeed!

More interesting is the fact that CV donor stars are larger and cooler than individual main sequence stars of equal mass. Observing these secondary properties may tell us a lot about the evolutionary track of these systems. Fascinating stuff presented very well. Two Simothumbs up for this one.

What's that? You say you don't understand magnetic braking? Don't worry, I'm in a room full of PhDs who will talk about it all day, but they don't understand it either!


Hands down winner of the animated visualizations for the conference thus far definitely goes to D.V. Bisikalo from the Russian Academy of Sciences, Moscow. His illustrations of accretion and the outflow of material into the envelope around the binary were fascinating to watch and quite detailed. The parameters and science used to achieve these results may be unrealistic, but the animations were glorious! Not only that, but watching the accretion overflow, I had an 'aha moment' for something I've been working on regarding Z Cam outbursts.




For those of you who remember my blog on 'Dusty Toads', here is one of the authors, Don Hoard, talking about surprising dusty environments around cataclysmic variables. They went hunting for information about the red secondary star of WZ Sge with the Spitzer Space Telescope and found so much dust they couldn't observe the secondary! A surprising result that may lead to, well, who knows?

I'll be interviewing Steve and Don about their dusty toads and where this new result may lead CV research.

On a personal note: it has been a lot of fun meeting the people and associating the names with the faces. I met several Japanese observers and important contributors to CVnet-Akira Arai, Hiroshima University, Izumi Hachisu, University of Tokyo, Akira Imada, Kagoshima University, Daisaku Nogami, Kwasan Observatory, Kyoto University. I also got to meet and talk with astronomers using AAVSO data for their papers here at this conference or elsewhere: Brad Schaefer, Louisiana State University, Christian Knigge, University of Southampton.

AAVSO was well represented with Arne Henden giving a poster presentation with hundreds of AAVSO light curves and Paula Szkody talking about pulsating white dwarfs in SDSS CVs.

Boris Gaensicke, who I met for the first time in Cambridge, UK last spring, seems to have his fingers in so many pies here it is quite remarkable. He is listed as a co-author or principle investigator on at least 40% (UNSCIENTIFIC SIMO-ESTIMATE) of the papers being presented.

And on a personal basis, I had the pleasure of meeting Kurtis Williams, of Professor Astronomy's Astronomy Blog .
He has been kind enough to support the AAVSO Writers Bureau with his blogs and is an all around nice guy who it is my pleasure to have met finally.

It's been a good time so far. More later.

Wild Stars- Day Three

For those of you who came in late on this one, I am in Tucson, Arizona, attending a conference on cataclysmic variables called Wild Stars in the Old West. It has been ten years since the last American CV conference, and five years since the last international CV conference. I wouldn't have missed this for the world. CVs are my thing.


Not only that, but this conference's attendees list is a literal who's who of the CV research world. I am having a ball. Writing all about it has been a pleasure too, even if I have to stay up well past midnight local time to get it done.

Day three featured talks on Magnetic CVs, Accretion Disks and Symbiotic Variables.

The morning session began with Kent Honeycutt showing results of time-resolved spectroscopy of He I and H-alpha lines in BZ Cam. He showed some slick animations that illustrate wind events in the system. Axel Schwope's paper investigated the physics of hard x-ray emitting shocks in Polars using the XMM-Newton satellite. I also learned some new acronyms in common use in Polar research. LARPs, HARPs and PREPs. Low accretion rate polars, high accretion rate polars, and pre-polars respectively. You really have to keep up with the acronyms around here or you won't have a clue what they are talking about!

David Buckley gave an animated, and at times humorous talk on the Southern African Large Telescope (SALT) and its fantastic suite of instruments, capable of doing high signal to noise time resolved photometry, spectroscopy and polarimetry. He also gave some honest insight into the pressures and demands of launching a sophisticated instrument program like this and its affects on the stressed out astronomers.

Polars were the prevailing topic in the morning sessions. Fred Walter showed results of nearly continuous coverage of EF Eri with the SMARTS telescopes since 2003, and an overview of the long term behavior of the system since the 1970's and 80's. Paul Mason explained how highly magnetic polars like AT UMa emit at radio wavelengths. It turns out that accretion disks may actually squash radio emission, so the lack of an accretion disk in polars allows radio waves to be detected from these CVs outside of an outburst. Domitilla de Martino summarized results form XMM-Newton observations of Intermediate Polars (IPs). She also pointed out some of the similarities between IPs and Polars.

After lunch we delved into the hearts of magnetic CVs and accretion disks. The first talk described an exceptionally long Chandra observation of EX Hydra and all the science they were able to glean from such a high signal to noise X-ray spectrum. They were able to explore the emission lines formed in the accretion column as well as first time ever views of a broad component that represents photo-ionization of the accreting column.

I think its amazing how these guys can glean so much science out of 140 hours of time on a space telescope. They were also able to tell the size of the accretion spot and the height of the shock area. All this from an x-ray spectrum!

Chris Mauche reported on a multi-wavelength campaign on the amazing star AE Aquarii. The combined radio, optical, UV, x-ray and gamma-ray results were presented eloquently. Chris is an excellent speaker and a brilliant astronomer. Knox Long described in detail his observations of the structure and source of winds in cataclysmic variables. The end result being, our current understanding is just about right.


The talk that generated the most interest and discussion day three was Graham Wynn's talk on RS Ophiuchi and CVs with massive white dwarfs, giant secondaries and massive accretion disks. He had six movies running at once, a conference record, demonstrating the fact that no matter what the rate of accretion, a disk was formed from the secondary wind. He then suggested some unique solutions to dramatic outbursts RS Oph and objects like it.

Big red secondaries and binaries with long periods remained the objects of interest for the last two talks on symbiotic variables. These interacting binaries present their own challenges to astronomers trying to understand binary evolution.


After the sessions were over we all piled into four buses and rode to dinner at a western steak house in Tucson. It was a fitting scene for a conference about wild stars in the old west. 13 hours after heading to the observatory I found myself walking back to the hotel in the crisp dry evening desert air. I woke up the next day with vague recollections of a dream about Willie Nelson (or was that Steve Howell?) and supernovae.

Wild Stars Pictorial Review Continued

This is Koji Mukai and Domitilla de Martino. Koji is one of the leading experts on intermediate polars in the whole world. Domitilla is also involved in IP research and presented a paper on results from the space X-ray observatory XMM Newton. For those of you who thought astronomers were geeks with no looks or personality, these two will shatter your ill-conceived notions in a matter of seconds.

Axel Schwope is another brilliant and entertaining astronomer using XMM Newton and other telescopes to examine some of the brightest polars in x-ray, optical spectroscopy and optical cyclotron spectroscopy.

I wonder what he tells people at parties when they ask him what he does?


You think astronomers don't have a sense of humor? You might be wrong. David Buckley shared this political cartoon from South Africa starring the SALT telescope. He was also brave enough to share this photo of himself in 'trying to get to first light' mode.

He really looks like Saddaam Hussein out of the foxhole.





Below, a rare sighting of Boris Gaensicke (left with pony-tail) actually sitting still!
He was chair of the session on this day. Here he is seen enjoying the talk from David Buckley (right), who looks much better with a shave and a bath.


Nerd Herd- here is a typical coffee break at the conference. The weather has been absolutely fabulous. Everyone enjoyed the outdoor courtyard gatherings in between papers.

Christpher Tout sharing ideas and sunshine during the break. Later, I pulled him aside to do an interview for a podcast. He was great.


Paula Szkody and friend discussing the merits of the poster in front of them. Paula also graced us with an interview for the podcast.

We talked about SDSS results and what is in her future. In a word- LSST. For those of you who are acronym challenged, that is the Large Synoptic Survey Telescope.





More polar humor. EF Eri is known mostly for the fact that it doesn't do anything most of the time. It's not accreting and we can examine the secondary star because there is no accretion light contribution in the way.

A little Star Trek humor lightens the mood.

Astronomy nerds can be fun...

Wild Stars- Looking Back

One of the best things about going to these meetings is you learn what astronomers are really looking at, researching, observing with space telescopes and how much the AAVSO is actually appreciated by the professional community.

There were AAVSO light curves in at least one out of three papers given here every day this week. Astronomers using sophisticated space telescopes and 8 meter telescopes on the ground are using AAVSO light curves of novae, recurrent novae, dwarf novae, symbiotic variables and all manner of CVs in their research.

The paper Brad Schaefer gave on recurrent novae was a virtual smorgasboard of historical AAVSO data. His research would be impossible without us, and he says so enthusiastically in the interview I did with him for the podcast. He has a list of five RN that he predicts will blow up in the next five to ten years, and T Pyx is NOT one of them. He is quite sure it will be the monitoring of these stars by amateurs that will result in the timely notification needed to alert astronomers to the rare opportunities these events present.

The professional CV community has given me a lot of one on one ideas to bring to amateurs about what it is they need and want, and how we can contribute in a meaningful way to their research. Steve Howell, Boris Gaensicke and Paula Szkody, talked with me one on one about what amateurs can do to help and what they have already contributed to the cause.

Personally, I learned a lot at this meeting. I was pretty fuzzy on the current hypothesis on pre-CV evolution, and the difference between symbiotic variables and common envelope binaries. I have a much clearer picture of why population studies are so important to CV
research. I was talking with Arne after the last session and telling him how by Thursday I was even beginning to understand x-ray light curves and recognizing emission, absorption, H alpha and beta lines in optical spectrum. I'm beginning to wonder how many spousal permission units it will cost me to buy a spectrograph!

I have a pretty current understanding now of what the core issues are that CV astronomers are trying to untangle, and what its gonna take to get them there. The exciting thing is WE CAN HELP. There is still a lot for amateurs to do with dwarf novae, symbiotics, recurrent novae (we practically own this field!), novae (lots of interest in novae!), and magnetic variables.

Even better, this was perfect timing, because we will probably launch the new CV Section this year after the spring meeting (if not sooner). I was able to rub elbows with all the top researchers in the field and let them know what we have planned and they are enthusiastic about the role we can play.

I got to spend some time with some of the key players from Japan who contribute to CVnet; and as usual, I was impressed with the way professional astronomers like Joe Patterson, John Thorstensen and Boris Gaensicke are willing to share the love of VSO and advise amateurs on how they can contribute to science.

It was awesome. And now my batteries and enthusiasm are fully charged. I'm glad to be home so I can get back to observing some of these wild stars myself!

Wild Stars- Day Four

Now that it is done, I am feeling a mix of relief and sadness. Relief- because four days of intensive research results presented session after session is like cramming a semester's worth of astronomy into your brain in four days. Sadness- because I could take maybe one more day, just to finish meeting and talking with some of the people I really wanted to talk to one on one. There just wasn't enough time. I think this was the most worthwhile, well-organized and relevant conference I have ever attended.

I'm not knocking any of the organizers of variable star meetings I've been to in the past, but this was all about CVs, all the rock stars of CV research were here, and I had back stage passes. It was frakkin' cool. The last day of the conference was all about things I am interested in- TOADs, Recurrent Novae and Classical Novae.

The talks of the day were also book-ended by two impressive astronomers from Japan's VSNET, Daisaku Nogami and Izumi Hachisu.

First thing in the morning session Daisaku Nogami presented impressive results of the superoutburst evolution of three very interesting CVs- WZ Sge, GW Lib and V455 And. These are three of the most significant outbursts of dwarf novae in the last couple years and Nogami had it all nailed down. The following talks on GW Lib and V455 And were almost redundant after the impressive amount of optical photometric and spectroscopic information Daisaku presented first thing in the morning.

The last talk of the morning session was about the source of negative superhumps, by Michele Montgomery. I had the pleasure of meeting her and talking for an hour or so Tuesday night, at the NOAO reception. She is an excellent presenter and had a great talk, chock full of teasers about her upcoming publication.

You just have to be intrigued by a woman who can teach you all about the minimum accretion disk tilt needed to generate negative superhumps in light curves, the parameters that affect negative superhump signal strength, and the location in the disk that contributes to this phenomena. That is sexy stuff!

Not to dismiss the other presenters who talked about classical novae and recurrent novae after lunch, but Brad Schaefer stole the show with his talk. Brad does not need a microphone to be heard in a room of 200 people. He is enthusiastic and knowledgeable about his topic, recurrent novae, and he knows how to work a room.

Some of the most exciting news from Brad were previously undiscovered eruptions of RN in past years. He and his graduate assistant relentlessly scoured all the archival data in the world to find plates and observations of recurrent novae outbursts. They found three eruptions of U Sco (1917, 1945, 1969) RS Oph in 1907, V2487 Oph in 1900 and CI Aql in 1941.

From these intensive searches, and modeling the results, Brad is able to make some bold predictions about the timing of future eruptions. In the next decade he predicts no less than five recurrent novae eruptions- V2487 Oph, V394 CrA, V745 Sco V3890 Sgr and the one he is most excited about U Sco. U Sco is predicted to erupt in 2009.3, which is RIGHT NOW!
After lunch we were shown amazing results of x-ray observations of recurrent novae and novae. There is a lot of interest in novae eruptions by professionals, more than I realized. What's more, they are making x-ray observations of these objects months and years after the initial outburst in an attempt to observe just when the accretion disk reforms and accretion begins again and what happens at this phase of the outburst.

From this I realized, amateurs need to follow many of these objects for much longer than we typically do as best we can. The AAVSO light curves sort of peter out after six months or so, and rarely is there much follow-up when a star reappears from solar conjunction. It's like we've all forgotten about them and moved on to the next big thing. Unfortunately, this is about the time they become really interesting to professionals, and from what I was seeing there may be some very interesting observational phenomena we are totally missing, like sudden rebrightenings of the systems or flickering. Amateur CV sleuths take note!One of the final talks of the conference was from Izumi Hachisu. He presented the methodology and results of his search for a relationship between the t3 time of decay (the 3 magnitude decay time from optical maximum) and the turn-on and turn-off times of supersoft x-ray emission. He presented detailed light curve analysis of classical novae detected in x-rays, and proposed best fit models that reproduce the optical and supersoft x-ray observations. If all that sounds impressive, you're right, it was. The fact that most of the data was collected with relatively small telescopes makes it that much more impressive.

That's about all I can dig out of my CV overloaded memory and notes at this point. I'm going to let this all digest for a day or two and write a summary review. I know I am looking forward to the next CV conference, which is planned for 2010 in Kyoto, Japan!