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SPA Variable Star Section. Annual Report 2018

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SPA Variable Star Section. Annual Report 2018 SPA Variable Star Section. Annual Report 2018. Over the course of 2018, eight members of the SPA Variable Star Section submitted observations. Those members where: Matthew Barrett, David Buehler, Tracie Heywood, Don Matthews, Keith Moseley, Jonathan Shanklin, David Smith and Robert Steele. David Buehler sent some observations from America, Keith Moseley sent in an image of Nova Persei 2018, Don Matthews used a DSLR, attached to a 20cm SCT, to follow long period variables when they were too faint for other members to see visibly. David Smith sent in two light curves of the eclipsing binaries AB Cassiopeiae and AD Andromedae. Tracie Heywood was kind enough to send in a large number of light curves. Z Ursa Majoris. Z Ursa Majoris is one of the more popular stars on our observing program, no doubt, due to the fact that it’s both circumpolar and always visible in binoculars. We have been able to follow Z UMa throughout the entire year. Z UMa has an extreme range of 6.3 – 9.8 and a more usual range of 6.9 – 8.7. However, in February of last year, we saw Z UMa reach an unusually bright maximum of 6.0. This was followed by two more maximum of 6.7 and 6.9; which is more in keeping with the star’s usual range. The period between maxima were about 85 days and 139 days respectively. Both these periods are considerable shorter then the quoted period of six months. The first two minima observed, of 8.8 and 8.7 are consistent with the stars usual brightness range. However, towards the end of the year the star fell to magnitude 9.4. The star seems to be characterised by rapid increases to maxima, followed by a longer decline to minima. RW Bootis. RW Bootis is a semi-regular variable with an extreme range of 6.4 – 9.2. However, it’s usual magnitude range is less then a magnitude (7.9 – 8.7). During 2018, the star varied between 7.8 – 8.7; which is typical behaviour. Given the low amplitude of the star, there is a fair amount of scatter in the light curve, as is to be expected. RW Bootis reached maximum in April, which was followed by a steep decline, followed by an unsteady rise to another maximum at the end of the year. In particular, RW Bootis experienced a prolonged standstill during August; when it remained at around magnitude 8.3. R Coronae Borealis. R CrB has remained in view of binoculars throughout 2018. However, with the star apparently varying by less then one magnitude, there is a lot of scatter in the light curve. Of course, it remains to be seem whether R CrB will remain this bright during 2019, or whether it will experience another fade. R Scuti. R Scuti is another very popular star and the members have managed to observe this star all year round. R Scuti always shows very complex behaviour. In 2018, R Scuti showed an amplitude of between 5.2 and 6.6, which is less then its usual amplitude of between 5.0 and 7.5. The graph shows five maxima, two in the early part of the year, one in February and another in March, and then three more in the latter half of the year. There was a maxima in July, one in September and a final maxima in November. There where three minima, a shallow minima in February and two deeper minima in June and August. AF Cygni.. AF Cygni is a popular semi-regular star, easily found near Delta Cygni in the constellation of Cygnus the Swan. Like all semi-regular stars, it is a red giant which outer layers pulsate; producing variations in brightness. AF Cygni was observed reaching maximum in September; when it reached a usually high maximum of 6.1. This is slightly outside the extreme range of 6.4 to 8.4. There was a slow rise to maximum followed by a rapid decline. T Cephei. T Cephei reach maximum brightness in May of 2018, slightly earlier then the predicted maximum of June. T Cephei remained close to maximum over the course of May and June. This maximum was followed by a slow decline to a minimum in October. R Leonis. R Leonis is a famous long period period, easily located near Regulus. It was first observed, at the beginning of the year, at magnitude 9.0, when it first became visible in binoculars. R Leonis reached maximum brightness in April 2018, when it reached a magnitude of 4.9, which is about as bright as it gets. R Leonis was still visible in binoculars at the end of the year. R Serpentis. R Serpentis is another long period variable. It reached maximum brightness in June and this maximum was characterised by a rapid increase in brightness and a slow decline. R Serpentis reached a maximum brightness of 6.1; which is not as bright as it can get, but still outside its usual range of 6.9 – 13.4. This shows why it’s always interesting to observe long-period variables, as their exact behaviour can never be predicted, and their behaviour will vary from one cycle to the next. R Ursae Majoris. The long period variable star R Ursae Majoris reached maximum in April 2018. R Ursae Majoris reach a maximum brightness of 7.1; which is a typical brightness for this star. R UMa was visible in binoculars for about three months, from March through to June. Don Matthews was instrumental in keeping the star under observation will it was too faint to be seen visually by other memebers. R Ursae Majoris shows a more symmetrical light curve then some other variable stars. S Ursa Majoris. S Ursa Majoris started the year at minimum, with a magnitude of 11.7, reached a maximum brightness of 8.1 in April, before reaching minimum in August with a magnitude of 11.9. By the end of the year, S UMa was back to a magnitude of 8.5. T Ursa Majoris. T Ursa Majoris was followed for a complete cycle of variation over the course of the year. It reached maximum brightness in February and was again at maximum, nine months later, in November. At its brightest, T UMa was at magnitude 8.1, and at its faintest, T UMa had a magnitude of 13.8. Overall, T UMa was fainter then its usual magnitude range of 7.7 – 12.9, would suggest. AD Andromedae and AB Cassiopeiae. David Smith has sent us light curves of two eclipsing binaries: AD Andromedae and AB Cassiopeiae. AD Andromedae is an eclipsing binary of the Beta Lyrae class. It has a magnitude range of 11.2 – 11.82 and a period of 0.986 days. AB Cassiopeiae is an eclipsing variable of the Algol type. It has a magnitude range of 10.1 – 11.85 and a period of 1.36 days. AD Andromedae. AD Cassiopeiae. RZ Cassiopeiae. RZ Cassiopeiae is an eclipsing variable of the Algol type. It has a magnitude range of 6.4 – 7.8 and a period of 1.195 days. Only Tracie Heywood was able to observe an eclipse of RA Cassiopeiae; on January 8th 2018. Tracie Heywood was also able to observe an eclipse of U Cephei on the evening of January 7-8th 2018. U Cephei is an eclipsing binary with a range of 6.7 – 9.3 and a period of 2.493 days. Omicron Ceti (Mira). Mira is the prototype long period variable star. Like all long-period variables, it is a red giant, which pulsates. However, molecules which form within the red giant’s outer layers selectively absorb light, which means that each cycle of variation is different. It has an extreme range of 1.7 – 10.1, but a more usual range of 3.6 – 9.3 and a period of around 11 months. In 2018, Mira was at maximum, with a recorded magnitude of 3.6 and was still, in principle, visible with the naked eye when it disappeared behind the Sun in February. When it was next observed, in October, it was at magnitude nine and quickly rose to a maximum brightness of 3.8 in November. The vice President of the SPA, Robin Scagell., photographed Mira at maximum during the month of November. Nova Persei 2018. During the month of May 2018, a bright nova was briefly visible in the constellation of Perseus. This star was originally designated as V392 Persei and was classified as a dwarf nova. A dwarf nova is an example of a cataclysmic variable, where a white dwarf and a cooler main sequence, or giant, star form a close binary. The white dwarf accretes material from its companion, and as material builds-up on the surface of the white dwarf, temperatures and pressures build until the material is throw-off, coursing the star to increase in brightness. V392 Persei was usually of magnitude 17 and would usually show outbursts of two to three magnitudes. However, on the 30th of April 2018, the Japanese observer Yuji Nakamura observed the star at magnitude 6.2. Nova Persei 2018 would soon peak at magnitude 5.6. On the 2nd of May, Keith Moseley photographed Nova Persei with a Nikon D7000 DSLR and a 135m f/2 Nikon lens, set at f/2.2, for 30s at ISO 800. He noted the nova appeared as unusually red. .
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