Variable Star Section Research Articles

Unveiled Pulsating Nature of IX Delphinus

IX Del is a variable star that was classified as uncertain E/SD at the Variable Star Index. The SSV-UAI-GRAV (Unione Astrofili Italiani, Variable Star Section) suggested a campaign to observe the star in order to understand its true nature. The Štefánik and Ďáblice observatories in Prague also collaborated in the observing campaign of the Italian section. From 2024 August to 2024 September, 10 observing sessions were obtained with terrestrial telescopes and V-band CCDs. From the analysis of the data thus obtained, combined with the Zwicky Transient Facility data, the star IX Del has been reclassified as an RRab-type variable with a pulsation period of 0.540914 day and a range of 1.36 mag g. The Blazhko effect from the result of this work is evident.

An Independent Discovery of the 1946 Eruption of the Recurrent Nova T Coronae Borealis and an Early Prediction of a Future Outburst

One of the earliest independent discoveries of the 1946 eruption of the recurrent nova T CrB was by British amateur variable star observer, N.F.H. Knight, on 1946 February 9 at 05.40 UT. Correspondence between Knight and W.M. Lindley, the Director of the British Astronomical Association Variable Star Section, reveals what might be the first prediction of a future eruption in 2026–27.

Discovered the Long-term Variation of the Variable Star CzeV818

In this study we describe the reclassification of the variable star CzeV818, discovered in 2015 by Pavel Cagas (Skarka et al. 2017), which was cataloged as a delta Scuti variable. From the photometric study performed with the telescopes of the SSV-UAI-GRAV (Unione Astrofili Italiani, Variable Star Section), All-Sky Automated Survey for Supernovae (Kochanek et al. 2017) (ASAS-SN) and Zwicky Transient Facility (Masci et al. 2019) (ZTF) surveys and the G-spectrum obtained from Gaia DR3 (Gaia Collaboration et al. 2023) (Astrophysical parameters inference system, Apsis) data, it was possible to understand that the luminous variation was not due to pulsations but due to spots (as discussed in Roxburgh 1964), present in the photosphere with a cycle of 0.402533 day (9.66 hr). Analyzing the long-term data present in the ASAS-SN and ZTF surveys, it was possible to determine a cycle of 2900 days (7.95 yr), which is similar to the solar cycle.

Variable star data online

Roger Pickard, Andy Wilson and Gary Poyner describe the online database of the British Astronomical Association Variable Star Section, a treasure trove of observations stretching back nearly 125 years.

The structure of the October/November 2005 outburst in OJ287 and the precessing binary black hole model

Aims. The blazar OJ 287 had its biggest optical outburst in over 20 years. It occurred in October/November 2005 and was somewhat expected since similar outbursts had occurred at approximately 12 yr intervals since the early 1900s. However, a strict periodicity would have put the event nearly a year later. Here we ask whether the October/November 2005 outburst was indeed the expected 2006 outburst of OJ287. Did it follow the typical light curve behaviour of such events: a rapid initial rise in just over a week and a slower decay in the following months? Methods. In this study we use the extensive observations of The British Astronomical Association Variable Star Section, complemented by the data from The American Association of Variable Star Observers. We compare the 2005 outburst with the previous season's first peak of 1983. Results. We find that the beginning of the 2005 outburst occurred at 2005.76, a few weeks earlier than was reported previously. The timing of the outburst is consistent with the binary black hole model of Lehto and Valtonen. In accordance with this model, we find that the outburst's structural time scale is slower in 2005 than in 1983, while the 2005 outburst was fainter than the 1983 outburst, making the two outbursts about equal in energy. Thus it is quite reasonable to argue that the 2005 outburst was the expected first of the season in the optical light curve of OJ287.

Fibonacci Sequences and the Multiperiodicity of the Variable Star UW Herculis

We present an application of the methods recently developed for the study of quasicrystal structures to the analysis of multiperiodicity of semiregular variables. A light curve analysis of UW Her shows frequencies that can be included within the general scheme characterizing the Fourier spectra of Fibonacci quasiperiodic sequences. The analysed data come from the BAA Variable Star Section computerised archive.

Eclipse Observations of IP Peg During Outburst

IP Peg is a U Gem-type dwarf nova with a very high orbital inclination such that the secondary star eclipses the white dwarf primary, accretion disc and hot spot in each orbit. An observing project was set up by ‘The Astronomer’ (TA) magazine and the British Astronomical Association Variable Star Section to make visual and CCD eclipse observations of IP Peg during outbursts in the 1994/95 season.

StarList 2000: a quick reference star catalog for astronomers

THE STARLIST. StarList, by Constellation. BINARY STAR SECTION. The Visual Binaries. Orbital Elements of Selected Binaries. The Drawn Orbits. VARIABLE STAR SECTION. Graphs. Periods and Epochs of All Variables in the StarList. Appendix. Indexes.

Contributions of Amateur Astronomers to Variable-Star Observing

Astronomy is a unique field of science in which amateur astronomers have made and continue to make significant contributions.One major area of the science of astronomy is the study of variable stars. There are more than 28,000 known and catalogued stars that change in brightness – variable stars – and about 15,000 suspected to be variable. These stars need continuous and systematic observing over decades to determine their behaviour and to record any of their unusual or rare activity. However, there are not enough professional astronomers or telescopes to observe these stars regularly. Therefore, variable star astronomy needs amateur astronomers to be the record keepers for these stars. It was for this reason that as early as 1844 and continuing throughout the second half of the nineteenth and early twentieth centuries, the astronomers F.W. Argelander of Germany, Sir John Herschel and J. Baxendell of England, D.F.J. Arago of France, and E.C. Pickering of the United States all advocated systematic variable star observing for amateur astronomers. The encouraging appeals from these leading professional astronomers resulted in the formation of several organized groups of variable stars observers, first in England – the British Astronomical Association (1890), Variable Star Section; then followed by the American Association of Variable Star Observers (1911); the Association Française des Observateurs d’Etoiles Variables (1921); the Royal Astronomical Society of New Zealand, Variable Star Section (1927); and the Japanese Astronomical Study Association (1945). Today, there are about 25 variable star observer groups around the world.

The work of the variable star section of the royal astronomical society of New Zealand

The work of the variable star section of the royal astronomical society of New Zealand

Reduction of Variable-Star Observations Using Basicode

The Dutch variable star section of the ‘Nederlandse Vereniging voor Weer-en Sterrenkunde’, founded in 1960, has about 10 to 15 regular observers. Depending on the weather conditions they perform 5 to 10 thousand observations a year. Our observation-recorder Henk Feijth collects the observations on paper and, since 1985, also on computer-cassette. From these contributions Feijth compiles a list on paper for the A.A.V.S.O. The cassette is written in a special format using the BASICODE program, see 2.The reduction of the observations can be described as following:1.Every observer and computer-owner enters each observation as a DATA statement in a BASIC program. So each DATA statement is a record representing one observation, each DATA statement contains 20 characters:1- 6 Starname7-10 int(JD-2440000)11-13 fractional part (3 decimals)14: or <15-17 estimate without decimal point18-20 observer codeSo a month of observations is simply a BASIC program consisting of just DATA statements.2.The Dutch broadcasting organization (NOS) has designed a kind of ‘Universal’ BASIC called BASICODE (version 2). With the aid of BASICODE computer X can read the programs of computer Y. The observer translates his data statements (the observations) into the BASICODE format. This is saved on cassette and sent to our recorder.3.Our recorder enters the monthly observations onto the BBC micro with the aid of the BASICODE translation program. Now the recorder runs a program that changes the star name into the Harvard number. This is done for the observations of every observer. After that the whole bunch of observations is sorted in ascending order of Harvard number and JD.4.The file of observations obtained in 3 is used as a source for our own reports, a graphic representation of the observations, and for simulating A.A.V.S.O. record sheets. This ‘end product’ we send to the A.A.V.S.O.

Outburst period–energy relations in cataclysmic novae

SS Cygni is by far the best studied dwarf nova; since its discovery its brightness variations have been monitored almost continuously, mainly by members of the American Association of Variable Star Observers (AAVSO), the Variable Star Section of the British Astronomical Association and L'Association Francais D'Observateurs D'Etoiles Variables (see Fig. 1). More than 600 outbursts have been observed to date. The eruption cycle of the dwarf nova SS Cygni behaves as a relaxation oscillator, with outburst energy correlated with the following quiescent waiting period. Two distinct, wide and narrow outbursts exist. The outburst behaviour is closely related to outburst rise-time, and to the quiescent brightness level. There is a strong tendency for low-amplitude, slow rise-time outbursts to be clustered in periods associated with bright quiescent levels. We show here that the behaviour of SS Cygni is in close agreement with theoretical predictions of dynamically unstable states of the red star when it fills the Roche-lobe, and is in conflict with the assumptions of early disk instability models.

PHOTOMETRIC AND SPECTROSCOPIC OBSERVATIONS OF NOVA T PYXIDIS

T Pyxidis is a member of a small group of objects known as recurrent novae. It underwent outbursts in 1890, 1902, 1920, 1944, and most recently, in late 1966. References to the earlier outbursts have been given by Schneller (1952) and Payne-Gaposchkin (1957). Finding charts for T Pyx have been published by Humason (1938) and in an unsigned article in the March 1967 issue of Sky and Telescope. The most recent brightening of T Pyx was initially detected by Jones (1966a, 1966&). Additional observations were reported in LAU. Circular No. 1986 by the Variable Star Section of the Royal Astronomical Society of New Zealand and by Solomon (1967) from data obtained with the Smithsonian Astrophysical Observatory's Baker-Nunn cameras. Many of these data have been illustrated in the light curve plotted in Sky and Telescope. Payne-Gaposchkin (1957, p. 150) has illustrated a composite light . curve from the 1902, 1920, and 1944 outbursts of T Pyx. A comparison of her light curve with the Sky and Telescope light curve indicates that during the 1966 brightening the recurrent nova followed a pattern similar to the earlier outbursts. The recent rapid initial rise took approximately three days followed by an interval lasting some 32 days during which T Pyx slowly increased in brightness to 6.3 photovisual magnitude.