Welcome to the AAVSO
Long Period Variable Section!
AAVSO LPV Section Leaders:
Administrator: Dr. Matthew Templeton
Science Advisors: Dr. Laszlo Kiss, Dr. John Percy,
Dr. Lee Anne Willson
Noise Characteristics of Long-Term Visual Light Curves
by Matthew Templeton and Margarita Karovska
January 23, 2013
Red noise, incoherent variations that exhibit stronger power at lower frequencies, are observed in a number of astrophysical phenomena. (See Kiss, Szabo, & Bedding 2006, and Templeton & Karovska 2009 for examples in AGB and supergiant stars; see Uttley, McHardy, & Papadakis (2002) and Rothschild et al. (2011) for examples from AGN. This noise manifests itself in observational data as a power-law underlying any periodic signals. The character of this noise seems to have broadly similar properties for variability in different types of object but there is no clear pattern in the character of red noise as a function of other properties (e.g. spectral type, pulsation period, or other stellar characteristics). Our aim in this study is to explore the parameter space of both stellar properties and data properties, and determine whether any of these relate to the observed power law spectra in Mira variables, or any other class of variable star for which the AAVSO has visual data. We discuss the power spectral properties of large samples of Mira variables from the AAVSO International Database, along with smaller samples of other variable star classes.
Presented at the 221st AAS Meeting in Long Beach, CA, January 9, 2013
by Lee Anne Willson and Massimo Morengo
July 18, 2012
Mira variables share essential characteristics: High visual amplitude, periods of hundreds of days, red colors (spectral types M, S, and C), and the presence of emission lines at some phases. They are fundamental mode pulsators, with progenitor masses ranging from >1 to several solar masses. In this review, we summarize what is known from modeling and observational studies, including recent measurements from optical and IR interferometry, and studies involving large samples of stars particularly in the Magellanic Clouds. While we have a good idea of how these stars fit into the big picture of stellar evolution, many important details remain to be settled by a combination of more ambitious models and new observational techniques. Carrying on observations of bright Mira variables will be essential for interpreting observations of large numbers of fainter sources as well as for assessing the completeness and accuracy of the models.
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 Alberio (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.
The faint stars in the comparison star sequence for T Draconis
The Biggest Star in the Universe
by Bob King
Astronomy is full of superlatives. Farthest, closest, hottest, densest, biggest, smallest. It’s fun to prowl around the sky in search of these extremes.
Two nights ago, I found myself star-hopping across Canis Major the Greater Dog in search of this or that gas cloud and spotted the star VY Canis Majoris on my atlas. The use of the lettered name “VY” tells us first off that this is a variable star whose light is not constant like the sun’s.
A quick check on the American Association of Variable Star Observers (AAVSO) website shows that VY varies between magnitudes 7.4 at brightest to 9.6. For the past few months it’s been around 8.0, bright enough to see in ordinary binoculars.
But its variability is not exactly the reason I wanted to acquaint you with this star. VY is special for an entirely different reason – it’s the largest star known! Astronomers estimate its diameter at some 2,000 times the size of the sun. And since the sun is no slouch at 864,000 miles across, VY is truly a monster.
Bulletin 77: Predicted Dates of Maxima and Minima of 381 Long Period Variables for 2014
February 27, 2014
The AAVSO Bulletin is one of the AAVSO's longest-running publications, dating to the days of Leon Campbell. The Bulletin itself has been used as a planning tool by amateur and professional astronomers alike for much of the past Century, while the data generated for preparation of the Bulletin -- AAVSO Maxima and Minima of Long Period Variables -- are themselves an important data resource for researchers of LPVs. Bulletin 77 for 2014 has predictions through February 2015.
Click here to access the AAVSO Bulletin
Getting Started with the AAVSO LPV Section
January 24, 2013
The AAVSO LPV Section is intended to be a means for the AAVSO to encourage the observation of Long-Period Variables (LPVs), to serve as a resource clearing house for LPV related science and information for observer, and as a social hub for members of the extended AAVSO community interested in the science and observation of Long-Period Variables. Browse the site to learn more about LPVs and how your observations will help science uncover more about these important variable stars.
Quarterly Data Reports now in the AAVSO Newsletter
January 23, 2013
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!
The LPV Double Trouble Campaign
February 4, 2012
Stars we call "Double Trouble" are stars that have close companions that create difficulties for visual and CCD observers alike.
You can read all about it on the LPV Section campaign page:
To join in the discussion please go to the LPV forum page on the LPV Double Trouble Campaign.
The AAVSO LPV Circular
February 1, 2012
One of the new initiatives of the LPV Section for 2012 is the LPV Circular.
This is an email you can receive each Wednesday listing all the Mira and Semi-regular variable stars that have observations submitted to the AAVSO International Database in the last 30 days. The circular application calculates the mean visual magnitude of all the observations for each day and lists the observer codes of those observers who supplied data for the prior 30 day period.
At the end of the circular is a key to the observer codes, so you can tell who everyone is.
You can subscribe to the LPV Circular here, or simply read the posts when they come out each Wednesday.
Some of the potential uses for this circular are:
The LPV Section is making a concerted effort to bring back the fun and excitement of observing Long Period Variable Stars, and we plan to create a place and an atmosphere where the visual observing community knows they are valued and appreciated and can share in their love of the stars and the art of variable star observing.
The LPV Circular is just the first of several new initiatives and campaigns we plan to launch this year. So join in and stay tuned. We've just begun!
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. But epsilon Aurigae is in full eclipse now, and will remain faint for most of this year, so maybe you’re ready for some new stars to satisfy your new addiction.
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!
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