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Europese Veranderlijke Sterren Bijeenkomst
Universiteitsmuseum Groningen, Nederland
22-24 oktober 2010

English version

• Prof. Dr. Adriaan Blaauw (voormalig directeur Kapteyn Instituut Groningen, voormalig directeur Europese Zuidelijke Sterrenwacht, voormalig voorzitter van de Internationale Astronomische Unie),
• Dr. Arne Henden (voormalig medewerker van de U.S. Naval Observatory, nu directeur van de AAVSO),
• Prof. Dr. Jan-Willem Pel (Kapteyn Instituut Groningen) en
• Prof. Dr. Frank Verbunt (Universiteit Utrecht).

1. NS Station
2. Universiteitsmuseum
3. University guesthouse

• Je kunt naar Bremen, Duitsland (luchthaven code BRE) vliegen en van daaruit met de Public Express Bus naar Groningen. Deze bus vertrekt vier keer per dag vanaf het vliegveld, om 6.30, 13.30, 17.15 en 23.45 uur. De busrit duurt 2 uur en 15 minuten en kost 25 Euro voor een retourticket.
• Je kunt naar Schiphol (Amsterdam), Nederland (luchthaven code AMS) vliegen en van daaruit met de trein naar Groningen. U kunt uw treinreis plannen met www.ns.nl/cs/Satellite/travellers. Kies Schiphol als vertrekstation en Groningen als aankomststation.

• 14.30: Registration at Kapteyn Institute

• 15.30: A Photometric Survey of the Sky (Arne Henden)

• • The positions of stars are well-known, with many ground-based and satellite surveys covering the entire sky.  The brightness of stars, and their colour or temperature, is a different story.  There is no existing photometric catalogue of the entire sky going fainter than what you can see with a pair of binoculars. An enormous amount of large telescope time is spent every year to measure the brightness of stars for scientific projects. The AAVSO is currently conducting an all-sky survey in five wavelength bands to finally solve this problem. The talk will give details of what kind of telescopes, cameras and software are needed, how you perform such a survey, and potential uses of the final database.

• 16.30: Reception, followed by a visit to Blaauw Observatory

• 10.00: Registration at the University Museum

• 10.30: Welcome (Theo Jurriens)

• 10.45: How it began (Georg Comello)

• • In June 1959 I started observing variable stars using a 42 mm refractor. This hap­pened in close correspondence with a Belgian society: Société´ Belge d'Astronomie. So the seed of the Werkgroep Veranderlijke Sterren der KNVWS (the Variable Stars Section of the Royal Dutch Society of Meteorology and Astronomy) lies in Belgium. In March 1960 I started my job for Dr. Lucas Plaut at the Kapteyn Laboratory (Nowa­days it is called Kapteyn Institute). I had to estimate the brightness of mainly RR Lyrae stars on the photographic plates of the Palomar-Groningen Survey. Dr. Plaut was very interested in my amateur observations on variable stars and he was sur­prised about the fact that I did those in close collaboration with a Belgian organization. He took the initiative to start a variable star section within the NVWS. The section was founded in the library of the Utrecht Observatory on the 23^rd of October 1960. Since that date the Variable Stars Section is actively promoting the observation of variable stars. In this talk a short report is given on the history of the Section. Further an overview is given of the problems we had to obtain good charts and useful sequen­ces. This was not easy at the beginning.

• 11.15: Half a century of variable star research (Jan Willem Pel)

• • Like in every other field in astronomy, the scope of variable star research has changed dramatically over the past 50 years. During these decades - thanks to the developments in space research and radioastronomy - nearly the entire electromagnetic spectrum has become accessible for astronomical observations. This led to the discovery of fascinating new classes of variable objects such as pulsars and X-ray binaries. The body of observational data on variable stars that we have today is not only very much bigger, but also much more diverse than what we had around 1960. At the same time there has been tremendous progress in our theoretical understanding of stellar physics. Starting in the late 1950's the theories of stellar structure, evolution and pulsation developed rapidly. For the first time it became possible to make detailed comparisons between theory and observations of stars. Variable stars turned out to be invaluable as test objects for astrophysical theory. At the same time they play a crucial role as 'standard candles' for the cosmic distance scale. This talk will summarize some highlights from the past half century.

• 12.00: The Work and Life of Lukas Plaut (Adriaan Blaauw)

• • abstract missing

• 12.30: Contributions of the WVS to the AAVSO (Arne Henden)

• • There have been decades of collaborative observing between the WVS and the AAVSO, plus many prior years of European contributions to our observational database. I will highlight some of the important observers, where your observations have been critical for projects, and make predictions for the future.

• 13.00: Lunch

• 14.00: YY Boo and TT Ari, very interesting variable stars (Josch Hambsch)

• • YY Boo, an Algol like eclipsing binary star, has been found to show also pulsations with high amplitude of 0.1 mag. In a multi-site and multi-month observing campaign in 2010 the complete light curve of this star has been measured in B and V photometric filters. TT Ari is one of the most mysterious cataclysmic variables which has been extensively observed during the last decline in brightness in October 2009, which was the first since the 1980ties. During several months the star was observed showing sometimes variations during one night from 13.5 to 16.5 mag. Results about both stars during their respective campaign will be shown and discussed.

• 14.30: The Deeply Eclipsing Polar "OT_J0711+44" (Arto Oksanen)

• • Summary of observations of the newly discovered deeply eclipsing polar CSS 081231:071126+440405 made by Arto Oksanen at the Hankasalmi observatory in Finland. Several light curves covering 22 nights, 52 eclipses and over 5200 data points will be presented. Preliminary results of the analysis will be discussed.

• 15.00: Using an amateur robotic telescope for observing variable stars (Frans Nieuwenhout)

• • Since 2005 a telescope has been established in the North of Holland which can be operated from a distance via internet. It has turned out to be a suitable instrument for doing variable star observations. The presentation will show with some examples how this is being done. It can be useful tool to gain some first experience by those people considering to start observing with a CCD camera.

• 15.15: Break and Group Picture

• 15.45: A Search for Dwarf Novae (Patrick Wils)

• • Cross-matching blue objects from the Sloan Digital Sky Survey and the Galaxy Evolution Explorer with the astrometric catalogues USNO-B1.0, GSC2.3 and CMC14, and those with large magnitude differences, revealed some 70 dwarf novae candidates.  Several of those have been confirmed spectroscopically or have recently been observed in outburst.  Data from the Catalina Real-time Transient Survey indicate that the recently discovered dwarf novae have less frequent outbursts compared to those known before. This suggests that a large number of dwarf novae are still unknown.

• 16.15: Supernovae (Frank Verbunt)

• • abstract missing

• 17.00: The Future of Amateur Variable-Star Observing (Arne Henden)

• • PanSTARRs is beginning its survey of the sky.  ASAS is now covering both northern and southern hemispheres.  LSST is just around the corner.  Do these and other surveys leave room for the amateur to contribute?  I'll discuss this important topic, plus give some ideas of future projects and instrumentation where amateurs will be major players for a long time to come. The Future of Amateur Variable-Star Observing  (This talk will be followed by a discussion).

• 19.00: Reception followed by dinner

• 10.00: Registration at the University Museum

• 10.30: Period Changes in SY Herculis (Erwin van Ballegoij)

• • Although the well known Mira variable SY Herculis is extensively studied since the 1960ties, it is still not possible to predict the time of maximum with sufficient accuracy. A first study by Ahnert (1976) showed that the period of SY Her is not constant, but changes from time to time. In this follow-up study the period evolution of SY Her is followed from 1967 until 2010 using AAVSO data.

• 11.00: The challenge of observing transits of exoplanets (Frans Nieuwenhout)

• • An exoplanet transit causes a dip in stellar intensity of at most a few tens of milli-magnitude. To measure these requires careful attention to reduce all possible sources of error to to a sufficiently low level. Some difficulties will be discussed and ways to overcome them will be shown. A few examples of transits will be given.

• 11.30: Time Series CCD Photometry from Nyrölä and Hankasalmi observatories (Arto Oksanen)

• • The two country-side observatories of Astronomical association Jyväskylän Sirius will be described. The both observatories have 40 cm telescopes that have been optimized for time-series CCD photometry, but the observing is very different between a "manual" observatory versus a fully automated one. The most important photometric observations made at the observatories will be presented.

• 12.00: Variable Stars from the Chandra Guide Camera (Arne Henden)

• • The Aspect Camera, the main guide camera for the Chandra X-Ray Satellite, monitors 4-6 stars continuously for hours to days in order to control the positioning of the satellite.  The photometric observations are downloaded to the ground, and checked to ensure proper star acquisition and guiding.  The generated light curves have also been examined for stellar variability, and nearly a thousand stars have been found to be variable.  These are all in the 8-10mag range, easy to observe with small telescopes, yet are almost all new variables.  The majority are low-amplitude stars, ideal for CCD or DSLR observing, but there are some higher amplitude eclipsing systems and long-period variables that can be followed visually. This talk will present some of the stars, give the website where you can examine the light curves, and suggest a campaign to monitor as many of these stars as possible.

• 12.30: Departure to Franeker with Lunchbox

• Discovery of the Eclipsing Binary VSX J194712.7+361748*** (Yenal Ögmen)

• 50 Years of Variable Star Observing in the Netherlands* (Erwin van Ballegoij)