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Visual Observing of CVs and Other Stars

Visual Observing of CVs and Other Stars. Stephen Hovell VSSS3, 9 June 2014. Diagram by Dana Berry (Astronomical Visualization Laboratory at the Space Telescope Science Institute) :. Motivation.

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Visual Observing of CVs and Other Stars

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  1. Visual Observing of CVs and Other Stars Stephen Hovell VSSS3, 9 June 2014 Diagram by Dana Berry (Astronomical Visualization Laboratory at the Space Telescope Science Institute):

  2. Motivation Nightly coverage of some of our most important cataclysmic variables – by any observing method – has declined significantly over the past decade... Matthew Templeton, AAVSO Science Director, 2011

  3. Broad Types of Variables1. Cataclysmic Variables (CVs) CVs – interacting binary star systems with a white dwarf primary and a low mass, main sequence Sun-like secondary. The secondary loses material onto the white dwarf via accretion.

  4. Types of Cataclysmic Variables (CVs) • Novae and Supernovae • Recurrent Novae • Nova–like Variables • Dwarf Novae • There are others!

  5. CVs – Novae and Supernovae Classical novae outbursts are caused by the sudden nuclear fusion of hydrogen–rich material on the surface of the white dwarf.

  6. CVs – Recurrent Novae (NR) They lie between classical and dwarf novae. They have been defined as having two or more outbursts within 100 year

  7. CVs – Nova-like (NL) Variables These have similar spectra to other types of CVs in the visual light, but have not been seen to erupt.

  8. CVs – Dwarf Novae (DNe or UGs) • Outbursts result from temporary increases in the rate of accretion onto the white dwarf, caused by the additional material accreted onto the surface. • U Gem – prototype • Classified according to their light curve • UGSS, UGSU, UGZ, UGWZ

  9. Dwarf Novae: UGSS characterized by an increase in brightness by 2–6 magnitudes in one to two days, returning to their original brightness over several days

  10. Dwarf Novae: UGSU • show two types of outbursts: normal and supermaxima + ‘superhumps’

  11. Dwarf Novae: UGZ • show cyclic outbursts but sometimes after an outburst they exhibit standstillssomewhere between maximum and minimum.

  12. Dwarf Novae: UGWZ • subtype of UGSUs. The interval between super-outbursts is measured in decades, while normal outbursts are few and far between.(1978, 2001)

  13. Broad Types of Variables: 2. RCBs • carbon rich stars that stay at maximum brightness with periodic and unpredictable declines

  14. Some Personal Highlights • Fun and the unexpected • GR Ori – Nova? UGWZ • U Sco – a recurrent nova • S Aps – an RCB

  15. GR Orionis– Nova? UGWZ • 800 days of observations

  16. GR Orionis– Nova? UGWZ • Report unusual events ASAP!

  17. U Scorpii – a recurrent nova • Internet Notification

  18. S Aps – an RCB • Patience • Lowest recorded decline

  19. 2. Decline in Visual Observations • The problem • How serious is the decline? • Reasons for the decline • What can be done about it?

  20. The problem • AAVSO Forum : What’s happened to DX AND? • “thelack of serious encouragement aimed at our visual observers has resulted in a steady decline of enthusiasm in this area, reflected in the ever sparser coverage of a great many formerly well observed stars” (Bortle, 2014) • “some stars that were once regularly visited by AAVSO (and VSS RASNZ) observers get almost no love these days” (Simonsen 2014)

  21. How serious is the decline? • Three ‘legacy stars’ – VW Hyi, CN Ori, SS Cyg • Changes in observations over 60 years • Declines started in the mid 1990s • Fairly consistent across the three stars • A parallel decline in the number of observers • The decline has tailed off

  22. Reasons for the decline • Emergence of new technologies • Their decreasing cost • Software and the Internet Photo: David Ahn

  23. Reasons for the decline • Telescope design - APOs, large Dobs, Solar… • Rise in Imaging • Are visual observers looked down on as ‘poor cousins’? • The eye has been replaced by the New Technologies

  24. Prior to 1995 most observations were nightly or weekly visual observations and the goal was to monitor these objects for phenomena that occurred on timescales from days to years. Now a much larger fraction of data submitted consists of instrumental time-series of short-term phenomena. This shift in focus has drawn a number of observers away from long-term monitoring to these more focused, short-term projects. It has also brought about a shift from visual to CCD; while the number of visual observations of all variables submitted per year is now about half the number submitted in the mid-1990s. When visual observers do observe, they do not do so in the numbers they once did. Templeton, 2011

  25. Reasons for the decline • Disinterest and lack of awareness of scientific value • All-sky surveys • “…while I believe ASAS are trying to make their data available, there have been no public ASAS data releases in several years.  As a result, coverage of some southern variables has all but disappeared.” Matthew Templeton, 2014

  26. Reasons for the decline • Light pollution • Old observers like Albert Jones moving on • Increase in recreational observing • “as far as I can see, though Astronomy clubs have many ‘advanced’ amateurs with top notch equipment, their interests are almost entirely social and recreational… not scientific” Mike Linnolt, 2014

  27. How Can We Address the Decline?(i) Attracting New Observers • Be proactive • A good place to start • Talk to local societies • Visual observing is fun!

  28. How Can We Address the Decline?(i) Attracting New Observers • Part of an international network • Be a Mentor • AAVSO training manual • Show people how to make an observation – Follow up • Explain the scientific value of visual observing

  29. The Value of Visual Observations • Short learning curve • Relatively inexpensive compared with CCD etc. – naked eye, binoculars, small telescopes. • Quick response – see it, estimate it, report it. • More targets reached each night – find it, observe it, move on to next target.

  30. The Value of Visual Observations • Visual data provides a personal ongoing record(AAVSO’s LCG) • You may be the only person on the planet observing an outburst or a non-outburst • Visual Observing helps you to learn the Night Sky • Professionals WANT them – over 5000 requests per year.

  31. How Can We Address the Decline?(ii) Retaining Experienced Observers Although it's fun to see 4 magnitudes fainter using a CCD, the message that needs to be made is that ‘coverage’ of these variables [CVs] is usually more important than magnitude depth. This makes observing cataclysmic variables an ideal past-time for visual observers with modest equipment. Richard Stanton AAVSO 2014:

  32. (ii) Retaining Experienced Observers • AAVSO Support • Under-observed stars • CVNET Circular • Mynewsflash (MNF) • CVNET Website • activity at a glance • VSNETalerts (Taichi Kato, Kyoto University)

  33. How Can We Address the Decline?(iii) Capitaliseon the NTs • Working in partnership • Using NTs to make snapshots • JoschHamsch(Belgium) is a good example

  34. So What Can I Do? Suggestions for Visual Observers • The Bright Realm – Binoculars and Small Telescopes • Legacy Stars

  35. So What Can I Do? Suggestions for Visual Observers • The Fainter Realm for Bigger Telescopes 10”+ • Rare Events eg RCB fades, NR, UGWX • partnership with professionals and academics (Brad Schaeffer – FM Sgr)

  36. What Else Can I Do? –Suggestions for Visual Observers • Transient Events • Campaign Targets

  37. What Else Can I Do? –Suggestions for Visual Observers • Where the Surveys aren’t looking • Low on the horizon • Circumpolar regions • Milky Way • “As you can see, there are still thousands of stars visual observers can observe and still contribute to science”

  38. 4. Conclusion Rod Stubbings’ work on identifying OQ CAR as a UGZ “…is a perfect example of how the ground we visual observers stand on may be shifting… but there is still plenty of good footing if you think about what you are doing and adjust your program to the strengths of visual observing.” “Who knows what other interesting behavior might be detected by visual observers patiently and persistently observing their objects of interest night after night, year after year? One thing is certain. If you’re not looking, you won’t see it.” Mike Simonsen 2014, Leaderof CV Section

  39. “There is still plenty of work for visual observers. Instead of wondering what to do, make up your own projects on variable stars. For example, ASAS3 (the All Sky Auto–mated Survey) has been around for a long time and collected data on so many stars you might ask, why observe them? I have been looking at the ASAS3 light curves and noticed a lot of stars with incomplete light curves or in some cases no observ–ations.” Rod Stubbings 2014, one of the most prolific visual observers in the world

  40. “I sincerely hope that anyone reading this will realize that serious work can be undertaken with only basic gear. If one has access to a modern telescope with all the bells and whistles, please have a go at variable star observing. But do not despair if you do not have such equipment, as so much needs to be done and can be accomplished with very modest gear. I know – been there, done that. The main thing is to have fun.” Legendary observer,Albert Jones 2009

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