Документ взят из кэша поисковой машины. Адрес оригинального документа : http://mavr.sao.ru/hq/lizm/conferences/pdf/1999/2000_1_p26-p48.pdf Дата изменения: Wed Feb 24 18:49:36 2010 Дата индексирования: Sat Jun 26 16:46:07 2010 Кодировка: Поисковые слова: m 8

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I I . S p a t i a l d i s t r i b u t i o n
D . O . K u d r y a v t s e v , I . I . R o m a n y u k S p e c ia l A s t r o p h y s i c a l O b s e r v a t o r y o f t h e R u s s i a n A S , N i z h n i j A r k h y z 3 5 7 1 4 7 , R u s s i a

A b s t r a c t . T h e p a p e r d e s c r i b e s t h e o n g o i n g s t u W e p r e s e n t g e n e r a l i n f o r m a t i o n a b o u t t h e s e s t a r l o n g i t u d i n a l c o m p o n e n t o f t h e m a g n e t i c f i e l d ) i . e . s e e n p r e d o m i n a n t l y f r o m o n e p o l e ) . D i f f e r e r e v e r s i v e s t a r s a n d t h e i r f r a c t i o n i n o p e n c l u s t e r T h e f r a c t i o n o f s t a r s w i t h t i m e s l a r g e r f o r n o n - r e v e r s i r o t a t i o n a l a n d m a g n e t i c p o t h e a n g l e b e t w e e n t h e r o t a

d y s d an nce s h

o f m a g n e t i c c h e m i c a i v i d e d i n t o r e v e r s i v e d n o n - r e v e r s i v e ( w i t s i n s p a t i a l d i s t r i b u t a v e b e e n f o u n d .

l l y p e c u l i a r ( M C P ) s t a r s . ( c h a n g i n g t h e s i g n o f t h e h m a i n l y t h e s a m e s i g n , i o n o f r e v e r s i v e a n d n o n -

m e a s u r e d s u r f a c e f i e l d B S a m o n g s l v e s t a r s . T h i s i n d i c a t e s t h a t n a r r o w - l l e s , s u p p o r t i n g c o n c l u s i o n o f J . L a n d s t i o n a l a n d m a g n e t i c a x e s f o r s l o w r o t

o w l y r o t a t i n g S r C r E u s t a r s i s 2 i n e s t a r s a r e o b s e r v e d b o t h f r o m t r e e t a n d G . M a t h y s ( 1 9 9 9 ) t h a t a t o r s i s s m a l l .

1 . I n t r o d u c t i o n
I n t h e f i r s t p a p e r o f t h i s s e r i e s ( R o m a n y u k , 2 0 0 0 , t h i s i s s u e , h e r e i n a f t e r P a p e r 1 ) w e p r e s e n t e d a s a m p l e o f m a g n e t i c c h e m i c a l l y p e c u l i a r ( M C P ) s t a r s . T h e s a m p l e i n c l u d e s 2 1 1 C P s t a r s w i t h r e l i a b l y m e a s u r e d m a g n e t i c f i e l d s . T h e s t u d y o f m a g n e t i c C P s t a r s i s b e i n g c o n t i n u e d a n d i n t h i s p a p e r w e a n a l y z e t h e i r s p a t i a l d i s t r i b u t i o n i n o u r G a l a x y a n d d i s c u s s s o m e g e n e r a l p r o p e r t i e s . I t s h o u l d b e n o t e d t h a t t h e l a r g e s t s a m p l e o f C P s t a r s c o n t a i n i n g a b o u t 6 7 0 0 s t a r s m a i n l y b r i g h t e r t h a n 1 1 m a g n i t u d e h a s b e e n c o l l e c t e d b y R e n s o n e t a l . ( 1 9 9 1 ) . A b o u t 2 0 0 0 d i f f e r e n t t y p e C P s t a r s b r i g h t e r t h a n 9 . 5 m a g a r e c o n t a i n e d i n t h e H i p p a r c o s c a t a l o g u e ( G o m e s e t a l . , 1 9 9 8 ) . A b o u t h a l f o f t h e m a r e p r o b a b l y m a g n e t i c : H e - r i c h ( o r H e - s t r o n g ) , H e - w e a k , H g - M n , S i , S i + ( i . e . S i + o t h e r p e c u l i a r i t i e s ) a n d t h e c o o l e s t C P s t a r s w i t h S r , C r a n d E u p e c u l i a r i t i e s . N o n - m a g n e t i c C P s t a r s a r e : A m ( w i t h e n h a n c e d m e t a l l i n e s ) a n d B o o s t a r s ( w i t h w e a k m e t a l l i n e s ) . S o m e d a t a o f a m a g n e t i c f i e l d o f A m s t a r s h a v e b e e n a l r e a d y r e p o r t e d ( f o r e x a m p l e , K u v s h i n o v , 1 9 7 2 ) b u t t h e y a r e n o t g e n e r a l l y a c c e p t e d y e t . M a g n e t i c m e a s u r e m e n t s o f B o o s t a r s s h o w " z e r o " r e s u l t s ( I l i e v e t a l . , 1 9 8 8 , B o h l e n d e r a n d L a n d s t r e e t , 1 9 9 0 ) . A s w e m e n t i o n e d i n P a p e r 1 , t h e f r a c t i o n o f C P s t a r s i s a b o u t 1 5 % o f t h e u p p e r m a i n - s e q u e n c e s t a r s i n t h e s p e c t r a l r a n g e B 5 - F 5 . I t i s v e r y l i k e l y t h a t a l l H e - r , H e - w k , H g - M n , S i , S i + a n d S r C r E u s t a r s a r e m a g n e t i c , b u t a c t u a l l y w e h a v e f o u n d o n l y 2 1 1 M C P s t a r s , t h e p r e s e n c e o f a m a g n e t i c f i e l d f o r t h e r e s t o f t h e m ( a b o u t 8 0 % ) n e e d s t o b e c o n f i r m e d .

2 . G e n e r a l p a r a m e t e r s o f m a g n e t i c C P s t a r s
W e p r e s e n t s o m e g e n e r a l p a r a m e t e r s o f 2 1 1 M C P s t a r s f r o m o u r s a m p l e i n T a b l e 1 w h i c h s h o w s i n s u c c e s s i o n : H D / B D n u m b e r , a n o t h e r n a m e o f t h e s t a r ( i f a v a i l a b l e ) , H I P n u m b e r i n t h e H i p p a r c o s c a t a l o g u e , S p a n d p e c -- s p e c t r a l c l a s s a n d p e c u l i a r i t y t y p e ( t a k e n m a i n l y f r o m t h e p a p e r b y G l a g o l e v s k i j a n d C h u n a k o v a ( 1 9 8 6 ) ) , m a g n i t u d e V a n d c o l o u r - V t a k e n f r o m t h e H i p p a r c o s c a t a l o g u e , P -- p e r i o d i n d a y s ( f r o m t h e c a t a l o g u e o f C a t a l a n o a n d R e n s o n ( 1 9 9 8 ) o r f r o m o r i g i n a l p a p e r s f o r e a c h s t a r o f o u r s a m p l e -- r e f e r e n c e s s e e i n P a p e r 1 ) . W e c a n c o n c l u d e , t h a t t h e r a t i o o f t h e n u m b e r o f C P s t a r s w i t h m e a s u r e d m a g n e t i c f i e l d a n d t h e n u m b e r o f a l l C P s t a r s f r o m t h e H i p p a r c o s c a t a l o g u e v a r i e s s t r o n g l y f r o m t y p e t o t y p e : m a g n e t i c f i e l d s w e r e f o u n d i n 6 4 % o f H e - r a n d 5 7 % o f H e - w k i n c o m p a r i s o n w i t h 8 % o f S i - s t a r s . W e s u p p o s e t h a t t h e s e d i f f e r e n c e s a r e m a i n l y d u e t o o b s e r v a t i o n a l s e l e c t i o n , b e c a u s e S i p e c u l i a r i t i e s c a n e a s i l y b e f o u n d o n l o w d i s p e r s i o n s p e c t r a w h i c h a r e u s u a l l y u s e d f o r s p e c t r a l c l a s s i f i c a t i o n o f f a i n t s t a r s . T h i s i s w h y , f a i n t C P s t a r s a r e m a i n l y c l a s s i f i e d a s S i s t a r s . P e c u l i a r i t i e s o f S r , C r o r E u c a n o n l y b e s e e n o n t h e s p e c t r a w i t h h i g h e r r e s o l u t i o n , b e c a u s e o f t h i s t h e y w e r e f o u n d i n a s m a l l e r f r a c t i o n o f c o o l s t a r s . O u r n e x t s t e p i s a c o m p a r i s o n o f t h e n u m b e r o f M C P s t a r s f r o m o u r s a m p l e w i t h t h a t f o r C P s t a r s f r o m t h e H i p p a r c o s c a t a l o g u e ( G o m e s e t a l . , 1 9 9 8 ) . T h e n u m b e r o f d i f f e r e n t t y p e p e c u l i a r s t a r s i n b o t h c a t a l o g u e s a n d t h e i r r a t i o s ( H I P / M C P ) a r e g i v e n i n T a b l e 2 .

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o f m e a s u r e m e n t s o f B e h a d b e e n m a d e f o r 7 9 m a g n e t i c C P s t a r s . W e k n o w n o w o n l y 3 o f t h e m w i t h a n e s s e n t i a l n o n - d i p o l a r c o m p o n e n t : H D 3 2 6 3 3 ( R e n s o n , 1 9 8 4 ) , H D 3 7 7 7 6 ( T h o m p s o n a n d L a n d s t r e e t , 1 9 8 5 ) a n d H D 1 3 3 8 8 0 ( L a n d s t r e e t , 1 9 9 0 ) , d e t a i l e d r e f e r e n c e s c a n b e f o u n d i n P a p e r 1 . T h e r e s t 7 6 o f t h e s e s t a r s s h o w s i n u s o i d a l v a r i a t i o n s o f B e c o n s t a n t B e , s u g g e s t i n g a d i p o l a r m a g n e t i c f i e l d o f t h e w e l l - k n o w n M C P s t a r s . A l l v a r i a t i o n s a r e t h e r e s u l t o f r o t a t i o n o f a " c h e m i c a l l y s p o t t e d " s t a r w h e n t h e m a g n e t i c a n d r o t a t i o n a x e s a r e n o t c o - a x i a l ( w e l l - k n o w n o b l i q u e r o t a t o r m o d e l ) . A s t u d y o f t h e w e l l - k n o w n M C P s t a r s s h o w s t h a t t h e

T h e l a r g e f r a c t i o n o f m a g n e t i c s t a r s a m o n g h e l i u m C P s t a r s i s p r o b a b l y c o n n e c t e d w i t h t h e s m a l l n u m b e r o f t h e s e s t a r s a n d t h e m o r e d e t a i l i n v e s t i g a t i o n o f e a c h o f t h e m . O n t h e o t h e r h a n d , t h e p o s s i b i l i t y t h a t t h e i n c r e a s e d f r a c t i o n o f m a g n e t i c s t a r s a m o n g h e l i u m s t a r s r e f l e c t s t h e r e a l s i t u a t i o n m a y n o t b e e x c l u d e d . T h e d i s t r i b u t i o n o f t h e n u m b e r o f M C P s t a r s i n b r i g h t n e s s V a n d c o l o u r B - V i s d e m o n s t r a t e d i n F i g . 1. I t i s s e e n f r o m F i g . 1 t h a t t h e n u m b e r o f m a g n e t i c C P s t a r s s t r o n g l y d e c r e a s e s f o r o b j e c t s f a i n t e r t h a n 8 m a g n i t u d e s . M a g n e t i c f i e l d o b s e r v a t i o n s n e e d a h i g h s p e c t r a l r e s o l u t i o n a n d t h e r e f o r e t h e y h a v e b e e n m a d e o n l y fo r b r i g h t s t a r s , e v e n u s i n g m o d e r n t e c h n i q u e . C o l o u r s B - V o f p r a c t i c a l l y a l l M C P s t a r s a r e i n t h e r a n g e f r o m - 0 . 2 t o + 0 . 3 m a g n i t u d e .

p h y s i c a l c o n d i t i o n s i n a n e s s e n t i a l p a r t o f t h e m a r e d i f f e r e n t a t t h e m a g n e t i c p o l e a n d m a g n e t i c e q u a t o r . T h e d e p e n d e n c e o f p e c u l i a r i t y d i s t r i b u t i o n o n m a g n e t i c l a t i t u d e h a s b e e n s t u d i e d b y F l o q u e t ( 1 9 7 9 ) f o r 1 8 s t a r s , b u t w e a r e i g n o r a n t o f s y s t e m a t i c s t u d i e s i n t h i s a r e a m a d e o v e r t h e p a s s e d 2 0 y e a r s . W e w i l l n o w a t t e m p t t o d o t h i s u s i n g m o d e r n o b s e r v a t i o n a l d a t a . A l l 2 1 1 s t a r s f r o m o u r s a m p l e m a y b e d i v i d e d i n t o 3 g r o u p s : r e v e r s i v e , n o n - r e v e r s i v e a n d p o o r l y s t u d i e d m a g n e t i c s t a r s . 1 . R e v e r s i v e m a g n e t i c s t a r s . T h e s e s t a r s h a v e r e l i a b l y m e a s u r e d l o n g i t u d i n a l f i e l d s B e , t h e n u m b e r o f m e a s u r e m e n t s [n ] > 5 , t h e B e c u r v e c h a n g e s t h e s i g n . 2 . N o n - r e v e r s i v e s t a r s . T h e s e s t a r s h a v e r e li a b l y m e a s u r e d l o n g i t u d i n a l f i e l d s , t h e n u m b e r o f m e a s u r e m e n t s [ n ] > 5 , b u t t h e B e c u r v e h a s m a i n l y t h e s a m e s i g n . T h e c r i t e r i o n f o r d i s t i n g u i s h i n g b e t w e e n r e v e r s i v e a n d n o n - r e v e r s i v e m a g n e t i c C P s t a r s i s t h e f o l l o w i n g : t h e s t a r i s n o n - r e v e r s i v e i f t h e B e c u r v e h a s t h e s a m e s i g n f o r a t l e a s t 2 / 3 o f t h e p e r i o d o r m o r e . I n t h e s i m p l e s t c a s e o f a s i n e c u r v e o f B e a n d r a n d o m

3 . R e v e r s iv e a n d n o n - r e v e r s iv e m a g n e tic C P s ta r s
M a g n e t i c f i e l d d a t a f o r m o s t o f C P s t a r s o f o u r s a m p l e h a v e b e e n o b t a i n e d f r o m t h e l o n g i t u d i n a l c o m p o n e n t ( B e ) m e a s u r e m e n t s . W e n o t e d e a r l i e r ( i n P a p e r 1 ) , t h a t a s u f f i c i e n t l y l a r g e n u m b e r ( o v e r 1 0 f o r e a c h s t a r )


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s p a t i a l d i s t r i b u t i o n o f r o t a t i o n a l a n d m a g n e t i c a x e s , t h e f r a c t i o n N o f s u c h s e l e c t e d n o n - r e v e r s i v e s t a r s c a n b e c a l c u l a t e d u s i n g t h e e x p r e s s i o n

a n d t h e r a t i o o f n o n - r e v e r s i v e a n d r e v e r s i v e s t a r s i s 1 . 7 5 . I f t h e p e r i o d i s u n k n o w n , b o t h B e e x t r e m a m u s t b e o f t h e s a m e s i g n o r o n e o f t h e e x t r e m a m u s t a t l e a s t b e m o r e t h a n t w i c e a s l a r g e a s t h e s e c o n d . 3 . P o o r l y s t u d i e d s t a r s . T h e s e a r e r e a l l y m a g n e t i c C P s t a r s b u t w i t h a s m a l l n u m b e r o f B e m e a s u r e m e n t s , t h e r e f o r e i t i s i m p o s s i b l e t o d e c i d e w h e t h e r t h e s e s t a r s a r e r e v e r s i v e o r n o n - r e v e r s i v e . T h i s g r o u p c o n t a i n s a l s o M C P s t a r s w i t h m e a s u r e d s u r f a c e f i e l d s B s b u t w i t h l a c k i n g B e m e a s u r e m e n t s , a n d t h e s t a r s w i t h v e r y s m a l l m a g n e t i c f i e l d s w h e n m e a s u r e m e n t s a r e h i g h l y u n c e r t a i n . I t c a n b e i n f e r r e d t h a t r e v e r s i v e s t a r s a r e s e e n f r o m b o t h t h e m a g n e t i c e q u a t o r s a n d t h e m a g n e t i c p o l e s , w h i l e n o n - r e v e r s i v e s t a r s a r e p r e d o m i n a n t l y s e e n f r o m t h e m a g n e t i c p o l e s . W e m a y e x p e c t s o m e r e g u l a r i t i e s i n d i s t r i b u t i o n o f c h e m i c a l a n o m a l i e s w i t h m a g n e t i c l a t i t u d e ( F l o q u e t , 1 9 7 9 ) a n d r e v e r s i v e a n d n o n - r e v e r s i v e s t a r s m a y t h e r e f o r e s h o w d i f f e r e n t t y p e s o f p e c u l i a r i t i e s . I n t h e c a s e o f v e r y l o n g - p e r i o d s t a r s ( p e r i o d P > 5 y e a r s ) , t h e s i g n o f B e u s u a l l y d o e s n o t c h a n g e d u r i n g t h e p e r i o d o f o b s e r v a t i o n a n d w e c a n s t u d y p r a c t i c a l l y t h e s a m e p a r t o f t h e s t a r ' s s u r f a c e . F o r t h i s r e a s o n w e w i l l c o n s i d e r v e r y l o n g - p e r i o d M C P s t a r s , s u c h a s H D 2 0 1 6 0 1 ( P i s a b o u t 7 5 y e a r s ) , a s n o n - r e v e r s i v e . T h e d i s t r i b u t i o n o f M C P s t a r s f o r r e v e r s i v e , n o n - r e v e r s i v e a n d p o o r l y s t u d i e d s t a r s a c c o r d i n g t o t h e t y p e s o f p e c u l i a r i t i e s a n d t h e r a t i o n o n r e v e r s i v e / r e v e r s i v e ( N / R ) i s p r e s e n t e d i n T a b l e 3 . N o t e t h a t w e p r e s e n t i n t h e t a b l e t h e d a t a o n 1 9 3 M C P s t a r s o f 5 p e c u l i a r i t y t y p e s . T h e r e s t 1 8 o f t h e t o t a l o f 2 1 1 a r e : a f e w H g - M n , A m a n d s t a r s w i t h r a r e l y s e e n p e c u l i a r i t i e s , a n d s o m e n o n - c l a s s i f i e d p o o r l y k n o w n f a i n t A p s t a r s . A s u p e r f i c i a l a n a l s h o w s i n t e r e s t i n g f e a t e x a m p l e , t h e f r a c t i o (N /R = 2 . 5 0 ) i s e s s e n s t a r s ( N / R = 1 . 5 5 ) . y s i s o f t h e d a t a u r e s i n d i f f e r e n t t n o f n o n - r e v e r s i t i a l l y l a r g e r t h a n f r o m T a b l y p e s t a r s . v e H e - r s t h a t o f H e e 3 F o r t a r s - w k

c o n c e n t r a t e s a r o u n d t h e m a g n e t i c p o l e s , w h e r e t h e m a g n e t i c l i n e s o f f o r c e a r e p e r p e n d i c u l a r t o t h e s u r f a c e o f t h e s t a r . T h e s a m e i s p o s s i b l y t r u e f o r t h e d i s t r i b u t i o n o f s i l i c o n . I f t h e s t a r i s v i e w e d f r o m t h e m a g n e t i c p o l e , o n l y s i l i c o n a n o m a l i e s a r e m o s t l y o b s e r v a b l e ; i f s i l i c o n a n d o t h e r a n o m a l i e s a r e o b s e r v e d , t h e s t a r r o t a t e s s o t h a t b o t h t h e p o l e a n d e q u a t o r a r e v i s i b l e . A b o u t h a l f o f t h e c o o l e s t M C P s t a r s w i t h p e c u l i a r i t i e s o f C r , E u a n d S r h a v e i n s u f f i c i e n t n u m b e r o f B e m e a s u r e m e n t s . V e r y o f t e n d i f f e r e n t p e c u l i a r i t i e s ( f o r e x a m p l e , C r a n d E u ) v a r y i n a n t i p h a s e w i t h t h e p e r i o d o f r o t a t i o n . T h e r e f o r e t h e y a r e c o n c e n t r a t e d i n d i f f e r e n t p a r t s o f t h e s t a r a n d o u r s h a l l o w a n a l y s i s c a n n o t p r o v i d e a d e q u a t e r e s u l t s ; t h e s t u d y n e e d s t o b e c o n t i n u e d a n d a d e t a i l a n a l y s i s t o b e m a d e . A s w a s d e m o n s t r a t e d i n P a p e r 1 , w e h a d c o l l e c t e d 4 9 M C P s t a r s w i t h s u r f a c e m a g n e t i c f i e l d m e a s u r e m e n t s . S i n c e d i r e c t m e a s u r e m e n t s o f B S a r e p o s s i b l e o n l y f o r s t a r s w i t h v e r y n a r r o w l i n e s ( v s in i < 1 0 k m / s ) , t h e s a m p l e o f s t a r s w i t h m e a s u r e d B s v a l u e s i n c l u d e s e i t h e r s l o w l y r o t a t i n g s t a r s ( s m a l l v ) o r s t a r s v i s i b l e f r o m t h e p o l e o f r o t a t i o n ( s m a l l s i n i ) o r b o t h v a l u e s a r e s m a l l . L e t u s c o n s i d e r t h e f r a c t i o n o f s t a r s w i t h m e a s u r e d B 8 a m o n g r e v e r s i v e a n d n o n - r e v e r s i v e C P s t a r s . W e e x c l u d e h o t H e s t a r s f r o m o u r c o n s i d e r a t i o n b e c a u s e t h e y a r e f a s t r o t a t o r s a n d o n l y f o r t h e s t a r H D 3 7 7 7 6 w i t h a n e n o r m o u s f i e l d d i r e c t o b s e r v a t i o n o f s p l i t t e d Z e e m a n c o m p o n e n t s i s p o s s i b l e . T a k i n g i n t o a c c o u n t t h e a b o v e r s i v e s t a r s w i t h B 8 m e a s u r e m t i o n i s 7 / 3 9 = 1 7 . 9 % ) a n d 1 w i t h B S m e a s u r e m e n t s a m o n g 6 2 9 . 5 % ) . v e s a i d , e n t s a m 8 n o n - r 1 ( f r a c t i w e h a v e 7 r e o n g 3 9 ( f r a c e v e r s i v e s t a r s o n i s 1 8 / 6 1 =

I f t h e c o o l e s t s t a r s w i t h a n o m a l o u s S r , C r a n d E u a b u n d a n c e s w e r e c o n s i d e r e d , t h e d i f f e r e n c e s w o u l d b e s t i l l l a r g e r : 5 s t a r s ( 2 5 % ) w i t h m e a s u r e d B s o u t o f 2 0 f o r r e v e r s i v e , a n d 1 4 ( 5 0 % ) o u t o f 2 8 f o r n o n - r e v e r s i v e s t a r s . T h e l a r g e r f r a c t i o n o f n o n - r e v e r s i v e s t a r s a m o n g s l o w r o t a t o r s i n d i c a t e s t h a t t h e y a r e s e e n m o s t l y f r o m o n e p o l e . T h e p r e s e n t e d d a t a s u p p o r t t h e r e s u l t o f L a n d s t r e e t a n d M a t h y s ( 1 9 9 9 ) , t h a t t h e a n g l e s t a r s i s s m a l l ( n o n - o b l i q u e r o t a t o r ) . ( b e t w e e n t h e m a g n e t i c a n d r o t a t i o n a l a x e s ) i n s l o w r o t a t i n g

T h i s m a y s u g g e s t t h a t H e i n h o t M C P s t a r s c o n c e n t r a t e s m a i n l y a r o u n d t h e m a g n e t i c p o l e s . O f c o u r s e , a d e t a i l i n v e s t i g a t i o n i s s t i l l t o b e m a d e b u t w e w a n t t o n o t e t h a t a m o n g 9 H e - s t a r s 5 a r e n o n r e v e r s i v e , w h i l e 2 r e v e r s i v e H e - r s t a r s ( H D 3 7 7 7 6 a n d H D 6 4 7 4 0 ) w i t h a v a i l a b l e m a g n e t i c f i e l d m o d e l i n g s h o w e n h a n c e d h e l i u m a r o u n d t h e m a g n e t i c p o l e s ( K h o k h l o v a e t a l . , 2 0 0 0 ; B o h l e n d e r e t a l . , 1 9 8 7 ) . T h i s i s a n a d d i t i o n a l s u p p o r t o f o u r p o i n t o f v i e w : h e l i u m

4 . S p a t i a l d i s t r i b u t i o n
T h e s o l a r s y s t e m i s l o c a t e d a t t h e p e r i p h e r y o f o u r G a l a x y , a t a d i s t a n c e o f a b o u t 8 p c f r o m t h e c e n t r e i n t h e O r i o n s p i r a l a r m . I n t h e n e a r e s t n e i g h b o u r h o o d t h e s p i r a l a r m i s d i r e c t e d a l o n g a l i n e w i t h g a l a c t i c l o n g i t u d e s f r o m Z = 6 0 ° t o l = 2 4 0 ° . T h e G o u l d B e l t i s a r e g i o n w i t h h i g h e r c o n c e n t r a t i o n o f A a n d s t a r s i n t h e d i r e c t i o n w i t h g a l a c t i c l o n g i t u d e s f r o m l = 2 3 0 ° t o l = 2 6 0 ° t o a d i s t a n c e a s g r e a t a s 3 0 0 - 4 0 0 p c .


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Figur e 1:

The distribution of the number of MCP stars in V and B-V.

give n above . Amon g thes e 8 3 non-reversiv e star s w e hav e foun d 3 6 wit h (+) , (i.e . see n mainl y fro m th e positiv e pol e o f th e dipola r magneti c field ) an d 4 7 wit h (-) . W e disregar d thi s peculiarit y for th e tim e bein g bu t wil l kee p i t i n mind . O f 8 3 star s 3 5 non-reversiv e star s (4 2 % ) ar e mem ber s o f differen t ope n clusters . Thi s implie s tha t th e fractio n o f non-reversiv e star s i n cluster s i s 2 time s highe r tha t o f reversiv e stars . Tw o explanation s o f thi s effect ca n b e suggested . The dat a o n th e spatia l distribution : equatoria l First , thi s i s th e resul t o f observationa l selection . an d fo r th e epoc h 2000.0 , galacti c coordinates Sinc e peculiaritie s concentrat e mostl y a t th e magneti c coordinates l an d b , membershi p i n cluster s an d par poles , peculia r star s ar e the n easie r t o fin d amon g allaxes (in milliarcseconds ) for star s o f ou r sampl e ar e non-reversiv e stars . Second , thi s effect reflect s rea l presented i n th e nex t 3 tables . Membershi p i n clus spatia l orientatio n o f magneti c stars , connecte d wit h ters was take n fro m Kopylo v (1987 ) an d reference s generatio n an d evolutio n o f magneti c field s i n ou r therein an d fro m Renso n catalogu e (1988) . Reversiv e Galaxy . stars are presente d i n Tabl e 4 . I f w e restric t ourselve s t o inspectio n o f onl y th e Thus , w e hav e foun d 5 1 reversiv e MC P stars , 1 1 o f younges t ope n cluster s i n Orio n an d Scorpi o whic h the m (22 % ) ar e member s o f differen t ope n clusters . consis t mainl y o f ho t He-stars , w e wil l ge t a mor e Longitudinal magneti c field componen t change s th e impressiv e picture . sing , these star s hav e larg e spectra l variation s an d W e hav e foun d 5 reversiv e an d 1 0 non-reversiv e ar e bes t suite d for mappin g o f chemica l anomalie s o n MC P star s i n Orio n (4(+) an d 6 (-) ) an d 3 reversiv e the surface of th e star . an d 1 3 non-reversiv e MC P star s i n Scorpi o (3(+ ) an d Non-reversiv e magneti c star s ar e liste d i n Tabl e 5 . 1 0 (-)) , a tota l o f 8 reversiv e an d 2 3 non-reversive . I t shoul d no t b e left ou t o f accoun t tha t amon g Thus , w e selecte d 8 3 stars , th e longitudina l com 2 3 non-reversiv e star s 7 ar e (+ ) an d 1 6 ar e (-) . ponen t B o f magneti c fiel d o f whic h ha s mainl y th e W e checke d man y time s th e "zero-point " o f th e sam e sign. Th e selectio n criteri a i n thi s grou p wer e
e

Let u s examin e th e spatia l distributio n o f MC P stars o f ou r sample . Th e Hipparco s result s ar e be ing extensively discusse d i n literature . Th e parallaxe s available i n th e Catalogu e (ESA , 1992 ; 1997 ) can not b e applie d t o al l case s t o determin e distances , mainly becaus e o f th e influenc e o f duplicity . Therefor e th e Hipparcos tea m continue s t o prin t reduce d data , main dat a o n C P star s wer e publishe d b y Gome s e t al. (1998), Nort h e t al . (1998 ) an d others . W e wil l make use o f th e dat a fro m thes e papers .


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scal e o f magneti c observatio n an d hav e no t foun d an y "zero-point " instrumenta l shift s i n measurement s o f Babcock , Landstree t an d hi s co-authors , an d ou r ow n measurements . Therefor e w e canno t se e an y obviou s instrumenta l effects whic h shoul d possibl y lea d t o suc h results . Thi s ma y resul t fro m poo r statistics . O n th e othe r hand , thi s migh t sugges t tha t mag neti c field s o f youn g MC P star s i n cluster s coul d equall y for m a t a tim e fro m a reli c fiel d i n th e Galaxy . Genera l dat a for poorl y studie d MC P star s ar e presen t i n Tabl e 6 . Thi s grou p contain s a tota l o f 7 7 stars , 1 6 o f the m (2 1 % ) ar e member s o f clusters . Th e fractio n i s th e sam e a s tha t o f reversiv e stars . Not e tha t mor e tha n hal f (4 0 o f 77 ) star s o f thi s grou p ar e coo l SrCrE u stars , basicall y wit h measure d B bu t wit h a smal l numbe r o f B measurements .
8 e

duced , becaus e clos e binar y system s ar e no t spatiall y resolve d an d th e paralla x determinatio n i s strongl y affecte d b y orbita l motions . Hipparco s tea m (Gome s e t al. , 1998 , North , 1998 ) ha s considere d an d reduce d th e dat a o n C P star s an d publishe d correcte d dis tance s d fro m th e Su n an d z distanc e fro m th e plan e o f th e Galaxy . W e wil l construc t suc h a distributio n for MC P star s fro m ou r sampl e usin g th e dat a fro m th e paper s indicate d above . Th e result s ar e presente d i n Fig . 3 . Th e spatia l distributio n o f MC P star s i s th e sam e a s for al l C P stars ; al l MC P ar e uppe r main-sequenc e stars . W e presen t th e dat a o n distances , prope r motion s an d velocitie s i n th e nex t 3 tables . W e conside r onl y th e star s wit h know n parallaxes . Informatio n o n d an d , an d z wa s take n fro m Gome s e t al . (1998) , v -- fro m HIP , v ar e ou r calculations . I n cas e whe n th e dat a o n reduce d d an d z wer e no t avail able , w e calculate d distanc e d usin g direc t paralla x measuremen t fro m Hipparco s catalogu e (ESA , 1997) , indicatin g i t a s d .
r cal c

195 star s o f ou r sampl e (92% ) hav e measure d Hipparco s parallaxes . Thi s permit s u s t o construc t a ver y reliabl e spatia l distributio n o f MC P star s i n ou r Galax y u p t o a distanc e o f 200-30 0 p c fro m th e Sun . Th e distributio n o f MC P star s o f ou r 3 group s i n galacti c coordinate s l an d b i s demonstrate d i n Fig . 2 . Th e Hipparco s parallaxe s ofte n nee d t o b e re -

Tabl e 7 contain s th e dat a for reversiv e stars . Th e dat a for non-reversiv e star s ar e presente d i n


37

Table 8. Th e dat a for poorl y studie d MC P star s ar e liste d in Table 9. Recentl y Romanyu k (1994 ) ha s foun d tha t ther e exist essentia l difference s i n th e spatia l distributio n o f non-reversiv e star s (+ ) an d (- ) i n differen t direction s in th e Galaxy . W e will no w conside r thi s proble m usin g a ne w sample o f stars . W e selec t tw o perpendicula r direc tions i n th e plan e o f ou r Galaxy : 1 alon g an d 2 acros s th e Orion loca l spira l arm . Calculat e th e numbe r o f MC P star s alon g thes e direction s insid e th e angle s o f 60°. Explanatio n se e i n Fig . 4 . For econom y o f spac e conside r no w onl y rever sive an d non-reversiv e C P star s i n Table s 1 0 an d 11 , respectively . Not e tha t th e Scorpi o cluste r ( l = 310 - 355° , b = 1 0 - 40° ) i s include d i n ou r discus sion, bu t Orio n ( l = 20 1 - 208° , b = -1 7 -: - -20° ) i s not . Calculation s sho w tha t 1 5 reversiv e magneti c star s are distribute d alon g th e Orio n spira l ar m an d ap proximatel y th e sam e number , 21 , alon g th e perpen dicular direction . Rati o 21/1 5 = 1.40. Th e dat a for non-reversiv e star s ar e give n i n Ta ble 11 . Non-reversiv e star s behav e i n a quit e differen t

way : 1 8 star s ar e distribute d alon g th e spira l ar m an d 3 9 i n a perpendicula r direction . Rati o 39/1 8 = 2.1 7 i s essentiall y large r tha n rati o 21/1 5 = 1.40 for reversiv e stars . Fo r 1 8 non-reversiv e star s distribute d alon g th e Orio n ar m 1 3 ar e (+ ) an d 5 ar e (-) , for 3 9 observe d i n a directio n perpendicula r t o th e spira l ar m 1 3 ar e (+ ) an d 2 6 ar e (-) . Thi s indicates , tha t ther e exis t grea t difference s i n spatia l distributio n o f (+ ) an d (- ) non-reversiv e stars . Whil e th e numbe r o f star s (+ ) i s equal : 1 3 alon g an d 1 3 acros s th e loca l spira l arm , for star s (--) w e ob serv e grea t differences : 5 alon g th e ar m an d 2 6 acros s it . Probabilit y o f rando m appearanc e o f suc h spatia l distributio n o f star s i s les s tha n 0.02% , therefor e th e abov e mentione d effect ma y no t b e a resul t o f rando m coincidenc e i n th e cas e o f smal l numbe r o f measure ments . Thi s proble m need s a mor e detai l study . Sinc e mos t o f star s (--) ar e member s o f Sco-Ce n association , w e planne d t o mak e a mor e detai l stud y o f MC P stars , member s o f cluster s an d associations . A ver y roug h estimat e o f velocitie s show s tha t the y ar e equa l i n al l direction s an d d o no t differ fro m thes e o f al l C P stars .


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origi n o f magneti c field; i n thi s cas e MC P star s i n cluster s for m simultaneousl y an d orientatio n o f thei r rotationa l an d magneti c axe s ca n b e mor e o r les s co linear . Acknowledgements . W e would like t o than k our colleagues from th e Stella r Magnetis m Laborator y of SAO RA S an d participant s o f th e presen t meeting , especially J . Landstreet , for helpful discussions an d th e Russian Foundatio n for Basic Researc h for partia l financial suppor t (RFB R gran t 99-02-26086) .

Reference s
Bohlender D. , Brown D. , Landstree t J. , Thompso n I., 1987, Astrophys . J, , 323 , 325 Bohlender D. , Landstree t J. , 1990, Mon . Not . R . Astron . Soc , 247 , 606 Catalan o F.A. , Renso n P. , 1998, Astron . Astrophys . Suppl . Ser., 127 , 421 ESA, 1992, Th e Hipparco s Inpu t Catalogue , ESA SP-1136 ESA , 1997, Th e Hipparco s Catalogue , ESA SP-1200 Floque t M., 1979, Astron . Astrophys . Suppl . Ser., 74 , 2 , 250 Glagolevskij Yu.V., Chunakov a N.M. , 1986, Bull. Spec . Astrophys . Obs. , 22 , 3 9 Gomes A.E. , Lur i X. , Greine r S., Figuera s F. , Nort h P., Royer F. , Torr a J. , Mennessier M.O. , 1998, Astron . Astrophys. , 336 , 953 Iliev I.Kh., Barzova I.S. , Glagolevskij Yu.V., Bychkov V.D. , Elkin V.G. , Romanyu k I.I. , Shtol V.G. , 1988, in: Glagolevskij Yu.V. , Kopylov I.M. (eds.) Magneti c stars , Leningrad , Nauka , 8 7 Khokhlova V.L., Vasilchenko D. , Romanyu k I.I., 2000, Pis'm a Astron . Zh. , (in press ) Kopylov I.M., 1987, Bull. Spec . Astrophys . Obs. , 24 , 4 4 Kuvshinov V.M. , 1972, Atron . Tsirc , 682 , 3 Landstree t J.D. , 1990, Astrophys . J. , 352 , 1 , L 5 Landstree t J.D. , Mathy s G. , 1999, Astron . Astrophys. , (in preparation ) Renson P., 1984, Astron . Astrophys. , 139 , 1 , 131 Renson P. , 1988, Astron . Astrophys . Suppl . Ser., 76 , 127 Renson P., Farragian a R., Catalan o F. , 1991(a), Astron . Astrophys . Suppl . Ser., 89 , 3 , 429 Romanyu k I.I., 1994, Bull. Spec . Astrophys . Obs. , 38,11 9 Romanyu k I.I., 2000, thi s issue Thompso n LB. , Landstree t J.D. , 1985, Astrophys . J. , 289 , 1, L9

5. Conclusion s
I n thi s par t o f ou r stud y o f magneti c chemicall y pe culia r star s w e presen t th e dat a o n thei r parameters : magnitude , colour , coordinates , period , parallax , ve locities . Ou r divisio n o f star s int o reversiv e an d non reversiv e permit s ne w features , for instance , i n th e spatia l distributio n o f star s an d membershi p i n clus ters , t o b e found . I t i s demonstrate d tha t amon g coo l SrCrE u star s th e fractio n o f star s wit h measure d surfac e field B for non-reversiv e star s i s tw o time s tha t o f reversive . Thi s indicate s tha t amon g slowl y rotatin g star s th e (betwee n th e rotationa l an d magneti c axes ) angl e ca n b e small , supportin g th e wor k o f Landstree t an d Mathy s (1999) . W e hav e foun d tha t fractio n o f non-reversiv e He star s i n th e ope n cluster s Or i an d Sc o i s 2 time s highe r tha n tha t o f reversiv e stars . Thi s fac t i s possi bl y cause d b y bot h observationa l selectio n an d reli c
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