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AAVSO Long Period Variable Section

  Welcome to the AAVSO LPV Section page!

   Administrator: Andrew Pearce

   Assistant Administrator: Frank Schorr

   Science Advisors: Dr. John Percy, Dr. Lee Anne Willson 

  

                                            

                                                LATEST UPDATE (JUNE 2 2017)

Just a quick note to give an update on the LPV Section.  

The LPV of the Month page has been updated and the star in question for June is BH Cru which is in the Legacy South LPV list.  The article was provided by Frank Schorr and it is a very interesting read about a star that was only discovered less than 50 years ago and has already shown appreciable changes in it's behaviour over such a short timeframe.  Please note that all the 2016 LPV of the Month articles have now been placed on a separate LPV of the Month Archive which you can see in the blue box to the right of screen.

I would really encourage interested observers to consider contributing a brief article on their favourite LPV.  These are fairly short and high level and they try to highlight interesting features of the particular LPV's to encourage other observers, so there's no need for an extensive scientific background on LPV's to contribute!

As mentioned back in March, one of the LPV Section Science Advisors and JAAVSO Editor, Dr John Percy, has put together a list of pulsating red giants that have and continue to show interesting and/or unusual behaviour.  The list has been designated "The Percy List" and can be found in our file section (the file is titled "The Percy List.pdf").  Sebastian Otero has now included it under the list of campaigns to facilitate easier searching in VSX (titled "Percy's Unusual LPV's")

In addition to John's list we would still like to encourage all observers to follow the list of target stars in both the northern and southern hemispheres mentioned last year.  Visual and multi-colour photometry is encouraged.   It's appreciated that the very nature of LPV's is that the subleties and interesting features of their light curve only become apparent over many years.

The current target stars are as follows:

Northern Stars

S Cep, R Aur, T UMi, RS Cyg, U UMi

Southern Stars

KK Car, TT Cen, V415 Vel, L2 Pup, RZ Sco

The newly released AAVSO Target Tool includes all of the LPV's as listed in the Legacy, Legacy South and Percy lists of stars.  This is a great tool to allow you to effectively plan your LPV observing program.  It details when the particular stars were last observed and the recommended cadence for observations.  You can also configure it to list just those stars observable at your location.  Click on the button below to go straigh to the latest LPV list.

As usual, we would appreciate any feedback as to what you would like to see on the web page.

Regards

Andrew Pearce (PEX)

                             Getting Started with the AAVSO LPV Section

Whether you are an active observer (of LPVs or other variable star types) or are a newcomer curious about LPVs and the AAVSO in general (and perhaps thinking about participating in observing variable stars) we hope that you find these pages of use! A goal of ours is to continually improve the usefulness of these pages to LPV observers and to stimulate continued interest in LPVs.  I would encourage everyone to read the paper from 2009 by Mike Simonsen and Kate Hutton on the establishment of the LPV Section.  It can be found here.

The AAVSO intends for the LPV Section to encourage the observation (whether by visual means or CCD/photoelectric photometry) of LPVs, to serve as a resource clearing house for LPV related science and information for observers, and to serve as a social hub for members of the extended AAVSO community interested in the science and observation of LPVs.

When we say "LPVs" we are not referring to a specific type of variable star, but rather to a large and diverse group of different types that we have chosen to place under the LPV umbrella. We choose to limit variable star types as LPV members to those whose brightness changes are due to pulsation and with periods (or approximate periods) longer than some dozens of days, up to periods of around 1000 days. Thus, Cepheid, RR Lyrae, and delta Scuti variables are pulsators, but their periods are too short to be included as LPVs. And, we do not include eclipsing binaries or eruptive-type variables, along with many other kinds of variables.

Even so, what we include as LPVs make up quite a few kinds of pulsating stars in terms of spectral type, stellar mass, and stage of evolution. Classification, for some, is difficult, either because the star in question has not been well observed, or some physical characteristic of the object is at odds with what most of the other stars placed in the same "box" have, such as stellar mass. We suggest you read the articles describing the LPV Zoo (found by following the link provided to the upper right on this page). These articles present the "official" descriptions (given in the General Catalog of Variable Stars, the internationally accepted clearinghouse for variable star types and cataloging) of the variables we include as LPVs, and additional information that helps enhance the official descriptions. There are LPV types that will interest almost anyone!

Our "bread and butter" LPVs are the "Miras", named after the prototype omicron Ceti, or "Mira The Wonderful". Mira was known to a number of ancient cultures, e.g., the Arabs and the Greeks, as a variable star. Miras are typically lower mass stars that are in the red giant phase of their evolution. The light curves for many look stable over years of observation, yet continued observation by the AAVSO and other variable star organizations has shown more than a few to be changing their periodicity, as well as exhibiting some unusual behavior in their light curves! These changes are indicative of the evolutionary processes taking place within the stars. Yes, these changes are slow to detect in any person's  lifetime, but detecting these changes makes these stars scientifically important, and validates the continued observation of them over a long time span. We also include the semi-regular red giant pulsators, the SRa and SRb types. These LPVs exhibit less regular (periodic) light curves than do Miras, presumably because these are in a somewhat different evolutionary stage in their lives. Again, studying their light curves has revealed some to be showing noteworthy behavior. More observations over long time periods are essential, as for Miras.

Then we have the SRc LPVs. These are believed to be massive stars that are in the red (super)-giant phase of their lives, probably on the way to eventually becoming supernovae. These stars tend to have longer, but less periodic, light curves than the Miras and semiregulars. These are rare stars. Some have low amplitude brightness ranges ( <= 1 magnitude) while other have ranges of several or more magnitudes, making these latter stars easy to observe by visual means.

We also include the "L" types of variables. These are variables that have poorly defined periodicity of brightness changes. Indeed, some may not truly be variables at all. Others may just have not been observed enough to determine if they actually belong in one of the categories mentioned above. The L types include red giants and supergiants.

Another LPV group comprises the RV Tauri variables. These are yellow supergiants in a later stage of evolution than the red giants. They are believed to be low mass stars, perhaps not much more than our Sun's mass. They exhibit unique light curves. Some light curves tend to be quite regular, with others showing a bit less regular curve and a superimposed "wave" of a longer periodicity. Hence, the subtypes of RVa and RVb. These variables have periods ranging from dozens of days to 100 or so days, notably shorter than the Miras and semi-regulars. These are also rare stars because they are believed to represent a very short lived evolutionary phase in their overall lives. Stellar evolution here is at a fast pace! Continual observation of the RV Tauris will likely reveal some interesting aspects of these objects.

Then we have the SRd LPVs. This is a bit of a mixed bag of pulsating variables. Most are thought to be low mass stars and in a late giant or supergiant stage of their lives. Their spectral types are typically F, G, or K, much like the RV Tauris. It is currently thought that these two types are related, each being in a somewhat different evolutionary stage. Here again, continued observation of the SRd and RV Tauri types may shed more light as to how these stars are related and to the details of late stellar evolution of low mass stars

The great majority of the LPVs described above in the AAVSO program have brightness amplitude changes that readily allow for accurate visual observation and brightness estimates. And, of course, all are accessible for photoelectric and CCD photometry measurements.

We encourage everyone to spend some time with the page links given to the right. These pages provide a good overview of what the LPV Section is about. 

Please browse the site to learn more about LPVs and how your observations will help science uncover more about these important variable stars.

Starting with the October 2012 Newsletter, we started a column that listed the most- and least-observed stars in both the AAVSO LPV and CV Legacy programs as a means of highlighting what stars in these two key lists were and were not getting good coverage. We've repeated this with "Looking at Legacy Stars" in the January 2013 Newsletter (see page 21). We encourage you to refer to this column in your seasonal planning. You should also look through the full LPV Program and Legacy LPV, and Binocular Program lists to see which stars are right for you and worth adding to your observing program. Don't forget, we also have the AAVSO Basic Observation Planner available on the AAVSO website as well! 

Check out the LPV Discussion Forum on the AAVSO Website! There is now a discussion forum on the AAVSO website dealing with LPVs and related topics. Drop in to see what observers and researchers are talking about, ask questions and share your experiences and knowledge.

Telescopic LPVs for New Visual Observers
Okay, so you’ve been observing some naked eye and binocular variables for a while. Good for you! The stars in the AAVSO Ten Star Training Program can be fun and rewarding to observe for a lifetime.
Maybe you were drawn in by the Citizen Sky project and now you’re getting hooked on variable stars. Hey, it happens; you are not alone. 

Perhaps you already owned a telescope or you finally got that shiny new 8” Schmidt-Cassegrain you’ve had your eye on for Christmas. Now where do you look for interesting variables? I’ve got some suggestions for you. These are fun stars to observe, AAVSO still needs observations of these stars, and best of all, they are easy to find and identify, so you won’t spend cold winter nights looking for them. You can spend your time observing them instead!
Read the full story

 

My Favorite Double Star

Mike Simonsen (SXN)

If you have spent any time looking through binoculars or telescopes you have undoubtedly come across a double star or two. Someone probably showed you Albireo (beta Cygni) at a star party or tried to impress you with a view of epsilon Lyrae, the famous Double Double in Lyra. One of my favorites is Rigel, the lower foot of Orion. Not many observers know Rigel is actually a double star. It has a 6.8 magnitude companion, Rigel B, 9 arc seconds away. This would be an easy double to separate in most small telescopes, but Rigel is the seventh brightest star in the sky. As such, it is some 400 times brighter than its companion, so Rigel B gets lost in the glare of its primary. Once you know where to look it's easy to find.

Double stars are interesting to people for a number of reasons. Some like the challenge of splitting close pairs with the smallest instrument possible. Others like to measure the characteristics, such as separation, position angle and magnitudes. But what really delights most people is a pair that exhibits a striking color combination. Some of the more popular pairs include Albireo (gold/sapphire), gamma Andromedae (gold/blue), xi Bootis (yellow/red) and alpha Herculis (red/green). I don't want to get into a debate about the perceived colors of these pairs. Your mileage may vary.

My favorite double has them all beat. It is a very colorful pair, with a blue-white primary and a deep red secondary. But the best part is this. It looks different every time you look at it, because the deep red secondary is a variable star! That's right, my favorite double star is also a variable.

You knew that was coming, right?

Okay, okay, I'll end the suspense. My favorite double is the Mira variable T Draconis.

     T Draconis resides just north of the head of the dragon

As variable stars go, it couldn't be much better. It's easy to find, located just north of xi Dra in the head of the dragon. It varies quite a lot, from 6.7 to 13.2V, and has an excellent sequence. Several of the comparisons from 11th down to 13th magnitude are located very close in to the pair, making it very easy to estimate when its fainter than the blue companion. The next time you find double stars on your observing program for the night, try out T Draconis. Take the time to make an estimate of its brightness and submit it to the AAVSO. Who knows, you just might get hooked. And there are plenty of other interesting double variable stars- TU Aql, T CMi, ST Aur, Z Tau, R Cyg...

Description: http://3.bp.blogspot.com/-dWjQMLqDm08/T5V0-6zbJJI/AAAAAAAACzQ/Gckk0efwgrA/s400/T+Dra+comparioson+stars.png

The faint stars in the comparison star sequence for T Draconis

 

 

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