standstill behavior in the light curve of uz serpentis orville h. brettman rivendell foundation...
TRANSCRIPT
Standstill Behavior In The Light Curve Of UZ Serpentis
Orville H. Brettman
Rivendell Foundation 13915 Hemmingsen RD. Huntley, Illinois. 60142
Electronic mail: [email protected]. Net
ABSTRACT. 3444 days of observations of UZ Serpentis are discussed. Numerous instances of standstill behavior are analyzed and the argument advanced for the reclassification
of UZ Serpentis
History
UZ Serpentis was discovered variable by Reinmuth at Konigstuhl in 1924
Parenago using the Moscow plates found that its variation resembled that of the irregular variables known as U Geminorum stars.
Herbig reports that Parenago found intervals between successive maxima to be between 20 and 36 days. Visual estimates of this range reported by Koyama et.al.during 1934-1935 indicated that the interval between outbursts were on the order of 19 – 32 days, and Herbig and others from the AAVSO found intervals to vary between 9 and 22 days.
Based on absolute visual magnitude studies of U Geminorum and SS Cygni conducted by the Gaposchkins and arguing from color magnitude estimates of Gerasimovic and Payne Herbig argued for the classification of UZ Serpentis as a U Geminorum star.
StandstillsThe Plot thickens
• Dyck published a paper in the Journal of the AAVSO in January of 1988 first calling attention to standstill behavior, which he had observed during the 1987 observing season. He noted that UZ Serpentis appeared to standstill in brightness for a period of approximately 6 months form May to October of 1987 when ‘normal’ outbursts reoccurred.
• Dyck again published in the Journal of the AAVSO in February of 1990 calling attention to yet another episode of standstill behavior in the 1989 apparition of UZ Serpentis. He also noted what he called a ‘Significant brightening‘ of the system toward the end of the standstill.
The Data
• The author began an investigation of the intermediate term behavior of UZ Serpentis in the summer of 2001 with the aid of observations of the magnitude of UZ Serpentis over nine whole and two partial apparitions of the variable, a period of 3444 days. The vast majority of the observations are visual with the remainder being CCD V band observations. All data points were provided by Janet Mattei, Director of the AAVSO, and the author is in her debt and that of the AAVSO for the provision.
• The data is presented here as 11 separate figures each represent the points of a given apparition. The very first data point was recorded on May 23, 1991 and the last was recorded on May 31, 2001.
F i g u r e ( 1 . )
U Z S e r p e n t i s J D 2 4 4 8 0 0 0 +
M a y 2 3 , 1 9 9 1 - N o v e m b e r 7 , 1 9 9 1
D u r i n g t h e a p p a r i t i o n o f 1 9 9 1 , w e s e e w h a t w i l l f o r t h e p u r p o s e s o f t h i s p a p e r b e r e f e r r e dt o a s n o r m a l b e h a v i o r .
A t t e n t i o n i s c a l l e d t o t h e p o i n t s b e t w e e n A a n d B a s w e l l a s t h e g e n e r a l a r e a b e t w e e n Ca n d D . T h e b e h a v i o r l o o k s a t f i r s t g l a n c e a s i f i t m i g h t i n d i c a t e a s t a n d s t i l l , h o w e v e r c l o s ee x a m i n a t i o n w i l l r e v e a l t h a t t h e r e a r e a n u m b e r o f i n s t a n c e s o f d i m m i n g . W h a t i s o f n o t eh o w e v e r ; a n d w e w i l l s e e m u c h m o r e o f t h i s i n s u b s e q u e n t f i g u r e s i s t h e t w o m a g n i t u d e s ,w h i c h t h e s e i n t e r r u p t e d p l a t e a u s r e s t u p o n .
A t o B s e e m s t o s e e k a r e s t a t 1 3 . 1 5 w h i l e C t o D s e e m s t o w a n t t o r e s t a t 1 3 . 5 . W e s e et h e s a m e b e h a v i o r i n l a t e r a p p a r i t i o n s , b u t f o r n o w y o u r a t t e n t i o n i s c a l l e d t o t h e s e l e v e l s .
1 2
1 3
1 4
1 5
1 6
4 0 0 4 2 0 4 4 0 4 6 0 4 8 0 5 0 0 5 2 0 5 4 0 5 6 0
A BC D
F i g u r e ( 2 . )
U Z S e r p e n t i s J D 2 4 4 8 0 0 0 +
F e b r u a r y 2 4 , 1 9 9 2 - N o v e m b e r 1 5 , 1 9 9 2
I n f i g u r e ( 2 . ) , w e s e e f o r t h e f i r s t t i m e w h a t w e w i l l r e g a r d i n t h i s p a p e r a s ' s t a n d s t i l l 'b e h a v i o r . A c c o r d i n g t o H e l l i e r ( 2 0 0 1 ) , s t a n d s t i l l s " a r e a l w a y s i n i t i a t e d b y a n o u t b u r s t "a n d " s t a n d s t i l l s a l w a y s e n d w i t h a d e c l i n e t o q u i e s c e n c e " . W e s e e t h i s b e h a v i o r f r o m ap o i n t j u s t p r i o r t o t h a t n o t e d b y a r r o w C a n d e n d i n g i n a n d a r o u n d a r r o w D . f o r t h e f i r s tt i m e i n o u r d a t a w e s e e a s t a n d s t i l l o f w e l l o v e r a m o n t h w h e r e t h e a v e r a g e b r i g h t n e s s o ft h e s t a r h a n g s n e a r t h e 1 3 . 5 m a g n i t u d e l e v e l . A f t e r t h e s t a n d s t i l l C - D w e s e e t h e s t a rb e g i n t o e x h i b i t w h a t w e w o u l d t e r m n o r m a l U G e m t y p e b e h a v i o r , f i r s t r i s i n g t o n e a r 1 2m a g n i t u d e , t h e r e t r e a t i n g t o n e a r 1 5 t h m a g n i t u d e , a n d c o n t i n u i n g t o s e e s a w t o a n d f r o f o ra p e r i o d o f m o r e o r l e s s 1 5 0 d a y s .
I t i s i n t e r e s t i n g t o n o t e h o w e v e r t h a t j u s t p r i o r t o t h e s t a n d s t i l l d e n o t e d b y C - D w e s e e a tA - B , a n o t h e r o f t h e p r e v i o u s l y n o t e d i n t e r r u p t e d p l a t e a u s w h e r e t h e s t a r h a s d i f f i c u l t yr i s i n g t o a m a g n i t u d e b r i g h t e r t h a n 1 3 . 1 f u r t h e r i t i s n o t e d t h a t t h e s e p l a t e a u s a r e p r e c e d e db y a b r i g h t e n i n g a n d s e e m t o e n d w i t h a d e c l i n e i n l i g h t . W h i l e n o t a s l o n g a s t h es t a n d s t i l l b e t w e e n C a n d D , a n d s l i g h t l y m o r e i n t e r r u p t e d o r n o i s y , i t a p p e a r s t h a t w e s e ei n t h i s a p p a r i t i o n s t a n d s t i l l b e h a v i o r o c c u r r i n g a t t w o s l i g h t l y d i f f e r e n t l i g h t l e v e l s .
T h e i n a b i l i t y t o r i s e a b o v e 1 3 . 1 m a g n i t u d e i s o n c e a g a i n s e e n t o w a r d t h e e n d o f t h ea p p a r i t i o n b e y o n d J D 2 4 4 8 9 0 0 .
1 1
1 2
1 3
1 4
1 5
1 6
6 7 5 7 2 5 7 7 5 8 2 5 8 7 5 9 2 5
AB
CD
F i g u r e ( 3 . )
U Z S e r p e n t i s J D 2 4 4 9 0 0 0 +
F e b r u a r y 1 9 , 1 9 9 3 - N o v e m b e r 2 1 , 1 9 9 3
I n f i g u r e ( 3 . ) , w e s e e a c o n t i n u a t i o n o f t h e b e h a v i o r , w h i c h w a s e x h i b i t e d n e a r t h e e n d o ft h e p r e v i o u s a p p a r i t i o n o f U Z S e r p e n t i s . U n t i l t h e p o i n t i n t h e l i g h t c u r v e d e l i n e a t e d b y Ai t i s s e e n t h a t t h e b e h a v i o r n e a r t h e e n d o f f i g u r e ( 2 . ) i s s t i l l e v i d e n t a n d t h a t t h e l i g h t o ft h e v a r i a b l e i s n o t e x c e e d i n g 1 3 . 1
F u r t h e r i f o n e r e t u r n s t o f i g u r e ( 2 . ) a n d e x a m i n e s t h e b e h a v i o r o f t h e l i g h t c u r v e n e a r J D2 4 4 8 9 2 5 i t w i l l b e s e e n t h a t a b r i g h t e n i n g h a s o c c u r r e d j u s t p r i o r t o t h i s p l a t e a u , a n dl o o k i n g n o w a t f i g u r e ( 3 ) w e s e e a d e c l i n e i n b r i g h t n e s s n e a r J D 2 4 4 9 0 0 6 2 . W h a t w eh a v e h e r e i s c l a s s i c s t a n d s t i l l b e h a v i o r a c c o r d i n g t o H e l l i e r .
C e n t e r e d o n p o i n t B w e s e e w h a t a f i r s t g l a n c e a p p e a r s t o b e a s h o r t s t a n d s t i l l . I t s h o u l db e n o t e d h o w e v e r t h a t t h i s p l a t e a u b e g i n s w i t h a d e c l i n e a n d e n d s w i t h a b r i g h t e n i n g . I t i sh o w e v e r n o t e w o r t h y t h a t t h i s p l a t e a u o c c u r s a t 1 3 . 5 m a g n i t u d e w h e r e w e s a w o u r f i r s ts t a n d s t i l l i n f i g u r e ( 2 . )
1 2
1 3
1 4
1 5
1 6
3 7 8 7 1 3 7 1 8 7 2 3 7 2 8 7
A
B
F i g u r e ( 4 . )
U Z S e r p e n t i s J D 2 4 4 9 0 0 0 +
F e b r u a r y 1 1 , 1 9 9 4 - N o v e m b e r 1 1 , 1 9 9 4
W h i l e t h e a p p a r i t i o n o f 1 9 9 4 g i v e s n o c l e a r i n d i c a t i o n o f s t a n d s t i l l b e h a v i o r i t i si n t e r e s t i n g t o n o t e t h a t w h i l e d i m m i n g s e e m s t o r e a c h l e v e l s t h a t t o t h e e y e a p p e a rr a n d o m , t h e s t a r s e e m s t o h a v e d i f f i c u l t y b r i g h t e n i n g b e y o n d 1 3 . 1 m a g n i t u d e . I t i s a l s o o fn o t e t h a t t h e a m p l i t u d e o f f l u c t u a t i o n i n c r e a s e s a f t e r t h e r a t h e r b r i g h t o u t b u r s t j u s t a f t e rJ D 2 4 4 9 5 7 5 . T h i s i s s o m e t h i n g w e w i l l s e e m u c h m o r e o f i n l a t e r a p p a r i t i o n s .
1 2
1 3
1 4
1 5
1 6
3 9 0 4 4 0 4 9 0 5 4 0 5 9 0 6 4 0
F i g u r e ( 5 . )
U Z S e r p e n t i s J D 2 4 4 9 0 0 0 +
F e b r u a r y 1 4 , 1 9 9 5 - N o v e m b e r 1 0 , 1 9 9 5
I n F i g u r e 5 w e o n c e a g a i n s e e s t a n d s t i l l l i k e a c t i v i t y a t A a n d a g a i n a t B . B o t h o f t h e s eb r i e f e p i s o d e s a p p e a r t o b e g i n w i t h a b r i g h t e n i n g a n d e n d w i t h a d e c l i n e .
1 2
1 3
1 4
1 5
1 6
7 6 1 8 1 1 8 6 1 9 1 1 9 6 1 1 0 1 1A
B
F i g u r e ( 6 . )
U Z S e r p e n t i s J D 2 4 5 0 0 0 0 +
M a r c h 8 , 1 9 9 6 - N o v e m b e r 3 , 1 9 9 6
I n F i g u r e 6 w e s e e w h a t b y a n y a c c o u n t m u s t b e a s t a n d s t i l l o f t h e v a r i a t i o n s i n t h e l i g h to u t p u t o f U Z S e r p e n t i s b e g i n n i n g a t A a n d e n d i n g a t B . T h i s s t a n d s t i l l h o w e v e r b e g i n s o na d e c l i n e i n l i g h t o u t p u t a n d s e e m s t o e n d o n a f u r t h e r d e c l i n e . A s t h e d a t a a r e r a t h e rw i d e l y s p a c e d a t s o m e p o i n t s a n d a s t h e r e i s s o m e d e g r e e o f u n c e r t a i n t y d u e t o t h e n a t u r eo f v i s u a l e s t i m a t e s t h e c o n t r a d i c t i o n w i t h H e l l i e r ' s r u l e m a y b e u n c e r t a i n .
W e c a n s a y w i t h a c e r t a i n t y t h a t t h e n a t u r e o f t h e b e h a v i o r o f t h e l i g h t o u t p u t p r i o r t o J D2 4 5 0 2 5 0 a n d t h a t a f t e r i n f i g u r e 6 a r e s o v e r y d i f f e r e n t , t h a t o n e c o u l d a s s u m e t h e m t o b ec o m i n g f r o m t w o d i f f e r e n t o b j e c t s .
1 2
1 3
1 4
1 5
1 6
1 5 0 2 0 0 2 5 0 3 0 0 3 5 0
A B
F i g u r e ( 7 . )
U Z S e r p e n t i s J D 2 4 5 0 0 0 0 +
F e b r u a r y 2 1 , 1 9 9 7 - N o v e m b e r 3 , 1 9 9 7
F i g u r e 7 p r e s e n t s n e w g l i m p s e s i n t o t h e e v e r - c h a n g i n g n a t u r e o f t h e l i g h t o u t p u t o f U ZS e r p e n t i s . A t ' A ' a n d ' B ' w e s e e w h a t m a y v e r y w e l l b e b r i e f e p i s o d e s o f s t a n d s t i l lb e h a v i o r , t h o u g h B d o e s n o t c o n f o r m t o H e l l i e r ' s r u l e . B o t h A a n d B a r e i n t e r r u p t e d b u tt h e i n t e r r u p t i o n o f A m a y w e l l b e w i t h i n t h e e r r o r o f t h e m e a s u r e s .
A t C , w e s e e b e h a v i o r s u c h a s w a s o b s e r v e d e a r l i e r w h e r e a l t h o u g h t h e r e i s v a r i a t i o n o na n o n g o i n g b a s i s t h e o u t p u t s e e m s t o h a v e d i f f i c u l t y g e t t i n g a b o v e 1 3 . 1 m a g n i t u d e .
I t i s b e c o m i n g a p p a r e n t a t t h i s p o i n t f r o m a q u a l i t a t i v e s e n s e t h a t t h e s t a r h a s t w op r e f e r r e d l e v e l s o f r e s t ; o n e d e f i n e d a t 1 3 . 1 m a g n i t u d e a n d t h e o t h e r a t 1 3 . 5 m a g n i t u d e . I na p p a r i t i o n s 2 , 5 , a n d 7 w e h a v e s e e n s t a n d s t i l l l i k e p l a t e a u s a t 1 3 . 5 m a g n i t u d e a n d i na p p a r i t i o n s 2 , 3 , 5 , a n d 6 w e h a v e s e e n s i m i l a r p l a t e a u s a t 1 3 . 1 m a g n i t u d e .
1 1
1 2
1 3
1 4
1 5
1 6
4 9 5 5 4 5 5 9 5 6 4 5 6 9 5 7 4 5
A B C
F i g u r e ( 8 . )
U Z S e r p e n t i s J D 2 4 5 0 0 0 0 +
F e b r u a r y 9 , 1 9 9 8 - N o v e m b e r 1 0 , 1 9 9 8
T h e a p p a r i t i o n r e p r e s e n t e d b y f i g u r e 8 i s n o t e w o r t h y i n t h r e e w a y s . F i r s t , t h e l i g h t o f U ZS e r p e n t i s h a s g r e a t d i f f i c u l t y g e t t i n g a b o v e t h e 1 3 . 1 m a g n i t u d e l e v e l f r o m t h e b e g i n n i n go f t h e a p p a r i t i o n u n t i l j u s t a f t e r J D 2 4 5 1 0 0 0 . S e c o n d w h e n w e d o s e e a b i t o f a p l a t e a u f o rt h e s p a c e o f a d o z e n o r s o d a y s , i t ' s w i t h n o g r e a t s u r p r i s e t h a t w e f i n d i t a t t h e 1 3 . 5m a g n i t u d e l e v e l a t t h a t p o i n t i n t h e c u r v e i n d i c a t e d b y ' A ' .
L a s t b u t n o t l e a s t a s w e w i l l s e e l a t e r i s t h e f a c t t h a t f o r t h e f i r s t t i m e i n t h e e i g h ta p p a r i t i o n s w e h a v e v i e w e d s o f a r w e s e e t h e f i r s t o c c u r r e n c e o f t h e l i g h t f r o m U ZS e r p e n t i s f a l l i n g b e l o w 1 6 m a g n i t u d e .
1 2
1 3
1 4
1 5
1 6
1 7
8 5 0 9 0 0 9 5 0 1 0 0 0 1 0 5 0 1 1 0 0 1 1 5 0
A
F i g u r e ( 9 . )
U Z S e r p e n t i s J D 2 4 5 1 0 0 0 +
F e b r u a r y 1 1 , 1 9 9 9 - N o v e m b e r 9 , 1 9 9 9
A p p a r i t i o n 9 s h o w s b e h a v i o r n o t y e t s e e n i n t h e p r e v i o u s a p p a r i t i o n s a s w e l l a s s o m e n o wf a m i l i a r .
F i r s t , w e n o t e t h a t t h e d e c l i n e t o b e l o w m a g n i t u d e 1 6 , w h i c h w a s f i r s t s e e n i n t h ep r e v i o u s a p p a r i t i o n , i s n o w n e a r l y c o m m o n p l a c e . S e c o n d o u r e y e i s d r a w n o n c e a g a i n t ot h a t l i n e o f r e s t w h i c h s e e m s t o f o r m a t 1 3 . 1 m a g n i t u d e ; a s i f t h i s m a g n i t u d e w a s i n d e e dt h e p r e f e r r e d s t a t e o f t h e s t a r s o u t p u t . T h i r d l y , o u r a t t e n t i o n i s d r a w n t o t h o s e t i m e s o fo u t b u r s t i n d i c a t e d b y t h e d e s i g n a t i o n ' A ' o n t h e c h a r t . N o t s i n c e a p p a r i t i o n t w o h a v e w es e e n s u c h b e h a v i o r , a n d t h e n n o t f o l l o w e d b y a n y t h i n g a p p r o a c h i n g t h e v i g o r o f v a r i a t i o ns e e n a f t e r J D 2 4 5 1 4 2 0 .
S u r e l y s o m e m e c h a n i s m n o t a c t i v e p r e v i o u s l y h a s ' t u r n e d o n ' h e r e . A b s e n t a l m o s t e n t i r e l yi s a n y a t t e m p t b y t h e l i g h t o u t p u t t o ' s t i c k ' a t t h e l e v e l o f 1 3 . 5 m a g n i t u d e .
1 2
1 3
1 4
1 5
1 6
1 7
2 2 0 2 7 0 3 2 0 3 7 0 4 2 0 4 7 0A
F i g u r e ( 1 0 . )
U Z S e r p e n t i s J D 2 4 5 1 0 0 0 +
F e b r u a r y 5 , 2 0 0 0 - N o v e m b e r 6 , 2 0 0 0
W h a t e v e r ' t u r n e d o n ' a t ~ J D 2 4 5 1 2 6 0 h a s b y t h e b e g i n n i n g o f a p p a r i t i o n 1 0 ' t u r n e d o f f ' ,a n d w h a t w e r e v a r i a t i o n s o f f o u r m a g n i t u d e s a r e n o w s e e n t o b e o f t h e n a t u r e o f o n e . T h a ti s u n t i l t h a t p o i n t o n f i g u r e n i n e d e s i g n a t e d b y ' A ' . T h i s o u t b u r s t c l e a r l y t r i g g e r s a s e r i e so f i n t e n s e f l u c t u a t i o n s o f o u t p u t t o w a r d t h e e n d o f t h e a p p a r i t i o n s i m i l a r t o t h o s e s e e nd u r i n g a p p a r i t i o n n i n e . I n a d d i t i o n , a s l i g h t t e n d e n c y o f t h e l i g h t o u t p u t t o w a n t t o h a n g a tt h e 1 3 . 1 m a g n i t u d e l e v e l c a n b e s e e n b e t w e e n J D 2 4 5 1 6 4 0 a n d J D 2 4 5 1 6 8 0
1 2
1 3
1 4
1 5
1 6
5 8 0 6 3 0 6 8 0 7 3 0 7 8 0 8 3 0
A
F i g u r e ( 1 1 . )
U Z S e r p e n t i s J D 2 4 5 1 0 0 0 +
F e b r u a r y 2 0 , 2 0 0 1 - M a y 3 1 , 2 0 0 1
A p p a r i t i o n 1 1 i s o n l y h a l f r e p o r t e d h e r e i n f i g u r e e l e v e n , a n d t h e f r e q u e n c y o fo b s e r v a t i o n s i s m u c h l o w e r t h a n p r e v i o u s a p p a r i t i o n s . H o w e v e r w e c a n s a y t h a t t h e l a r g ea m p l i t u d e v a r i a t i o n s s e e n i n a p p a r i t i o n s n i n e a n d t e n c o n t i n u e .
1 2
1 3
1 4
1 5
1 6
1 7
9 6 0 9 8 0 1 0 0 0 1 0 2 0 1 0 4 0 1 0 6 0
Discussion.
Kiplinger (1980) writes of Z Camelopardalis and its standstills as follows: "Although thesystem may undergo typical dwarf novae eruptions with a mean outburst period of 20days, it can also halt in its decline to minimum light for an indeterminate amount of timeat an intermediate level of luminosity. This halt at an intermediate luminosity level,referred to as a standstill generally lasts for a few days to a few hundred days and is thedistinguishing characteristic of the subclass. In a given dwarf nova, the standstillluminosity repeats at each standstill and is relatively stable with variations that aretypically less than 0.5 mag.".
From the foregoing examination of eleven apparitions of UZ Serpentis we have seenseveral interesting phenomenon not the least of which are several occurrences ofpreviously reported standstill behavior which conform to the definition of Kiplinger.Examples of standstill behavior can be found in apparitions 2, 3, 5, 6, 7, 9, and 10.
While not all standstills strictly conform to Hellier's rule, the author believes that thespread between some of the observations and the fact that most of the observations areaccomplished visually more than likely accounts for the discrepancy.
Further with a period of 4.15 hours as given by Downes et.al. (2001) UZ Serpentis falls on the high side ofthe period gap, as does Z Camelopardalis
Conclusion:
The author believes that the UZ Serpentis system should be reclassified as a ZCamelopardalis type system for the following reasons:
1. The original classification was based on color and absolute magnitude alone, withoutrecourse to long term monitoring of the light variation.
2. The system exhibits standstills of varying length in the majority of its apparitions.
3. The standstills occur at and within a magnitude range which puts them in agreementwith the earlier definition given by Kiplinger to wit: " In a given dwarf nova, thestandstill luminosity repeats at each standstill and is relatively stable with variations thatare typically less than 0.5 mag.".
The author gratefully acknowledges the assistance of the AAVSO and its Director JanetMattei without whose kind cooperation and help this study could not have beenundertaken.
References
AAVSO, 1938- 1941 Harvard Ann., 107,162,204,Downes, et.al. 2001 A Catalog and Altas of CataclysmicVariables Living edition http://icarus.stsci.edu
Dyck , G.P. 1987 JAAVSO 16,91Dyck, G. P. 1989 JAAVSO 18,105Gaposchkins 1938 Variable Stars ( Harvard MonographNo.5) p.283Hellier, C. 2001 Cataclysmic Variable stars, Springer/ PraxisHerbig, G. H. 1944 PASP 56,230Kiplinger A.L. 1980 ApJ 236: 839 - 846Koyama et.al. 1936 Astr. Nach., 259,245,Liu et.al 1999 ApJS 122, 243-255 May.Parengo, 1931 Nishni-Novgorod (Gorki)Veranderliche Sterne, 3, 112Payne, 1932 Harvard Bull., No.889,3Reinmuth 1924 Astr. Nach, 222, 305
