Документ взят из кэша поисковой машины. Адрес оригинального документа : http://jet.sao.ru/hq/lizm/conferences/pdf/1996/1996_p82.pdf Дата изменения: Wed Apr 21 21:00:57 2010 Дата индексирования: Tue Oct 2 08:33:13 2012 Кодировка: Поисковые слова: m 5

Magneti c fiel d variabilit y o f H D 9670 7
V.D . Bychkov , L.Yu . Kostynchuk , V.G . Shtol'
1

1

2

1

Specia l Astrophysica l Observator y o f th e Russia n AS , Nizhni j Arkhy z 357147 , Russi a Odess a Stat e University , Ukrain e

2

Abstract . Th e magneti c behaviou r o f H D 9670 7 i s studie d whic h appeare d t o b e harmoni c wit h a perio d o f 2.5 5 day s an d a n amplitud e u p t o 100 0 Gs .

1

Introductio n

Extensiv e stud y o f magneti c behaviou r an d orientatio n o f magneti c field s o f A p star s i s no w unde r wa y a t th e Specia l Astrophysica l Observatory . I n th e frame s o f thi s projec t th e A p sta r H D 9670 7 ha s bee n investigated . Th e magneti c fiel d o f H D 9670 7 (H R 4330 , G C 15332 , BD+6 8 632 ) wa s firs t examine d b y Va n De n Heuve l (1971 ) usin g th e photographi c technique . Accordin g t o his mea surement s thi s sta r ha s a stron g magneti c field , howeve r th e estimate s availabl e ar e insufficient for determinatio n o f th e perio d o f variability , th e kin d o f th e magneti c curve , etc .

2

Observatio n result s

A set o f apparatu s an d technique s ha s bee n develope d a t SA O for measurin g magneti c field s o f star s (Glagolevski j e t al. , 1978 ; Bychko v e t al. , 1988 ; Najdenov , 1989 ; Shtol' , 1991 ; 1993) . Tw o technique s hav e bee n chose n for magneti c measurements . Th e principa l on e -- circula r polarizatio n measure ment s i n th e wing s o f hydroge n line s o f th e Balme r series an d wit h a mas k o f 9 o n th e 6 m telescop e wit h th e hydrogen-lin e magnetomete r (Shtol' , 1991 ; 1993) . Th e metho d allow s th e longi tudina l magneti c field t o b e estimate d i n pur e state , withou t th e influenc e o f chemica l compositio n inhomogeneities . Th e othe r metho d -- us e o f Zeema n spectr a take n wit h th e spectromete r GEC S place d a t th e coud e focu s o f th e 1 m telescop e (Musaev , 1993) . Spectr a o f H D 9670 7 ar e recorde d wit h a standar d CC D detecto r o f 580 X 530 pixel s an d reduce d wit h th e ai d o f th e packag e DECH2 0 (Galazutdinov , 1992) . Thi s metho d make s i t possibl e t o obtai n man y different informatio n o n th e spectra , i n particular , t o refine suc h a n importan t paramete r a s vsi n i , etc . I n Tabl e 1 ar e give n th e result s o f magneti c field measurement s for H D 9670 7 obtaine d b y Van De n Heuve l (1971 ) an d ou r estimates . A s i s seen from th e table , th e accurac y o f photographi c estimate s i s no t high , therefor e i t wa s decide d no t t o us e the m i n furthe r analysis .

110


MAGNETIC FIELD

VARIABILITY

OF HD

96707


112

BYCHKOV,

KOSTYNCHUK,

SHTOL

Fro m fiv e Zeema n spectrogram s th e half-widt h o f th e M g I I 448 1 lin e wa s measure d (se e Tabl e 2) . Usin g th e well-know n metho d (Slettebac k e t al. , 1975) w e hav e determine d vsi n i = 3 6 km/s . Usin g ou r dat a a n attemp t i s mad e t o fin d th e mos t likely perio d o f magneti c variabilit y from th e minimu m su m o f th e square s o f deviation s from th e sinusoi d inscribe d b y th e least-square s metho d int o a phas e se t o f estimate s convolute d consecutivel y wit h th e tentativ e periods . Th e limits , i n whic h th e perio d o f star s ma y lie, ca n b e estimate d from th e know n parameter s o f th e star . Th e maxima l perio d i s possibl e i f sin i = 1 , i.e . whe n th e axi s o f rotatio n lies i n th e pictur e plane . -- equatoria l velocity ; -- projectio n o f equatoria l velocity ; day s -- maximu m possibl e period . Th e minimu m possibl e perio d ca n b e found , from l g g , i.e . i f V for a give n sta r i s highe r tha n ~ 300 km/s , l g g will the n b e 3.5 - 3.7 bu t no t 4. 2 (Renso n e t al. , 1991) . Henc e P = 50.6 1 R/V ~ 0.5 day . Thus , fro m th e dat a availabl e th e mos t likely period , 2.5530 5 days , i s found .
e min e

Havin g foun d th e mos t likely period , determin e parameter s o f magneti c variability . I n Fig. l i s displaye d th e phas e magneti c curv e draw n fro m all hig h accurac y magneti c fiel d estimates . I f t o suppos e tha t magneti c curv e i s sinusoidal , the n

wher = = =

e 110 ± 65 G -- constan t componen t of th e magneti c field, 47 4 ± 90 G -- half-amplitud e of th e magneti c field, 2450112.10 7 -- initia l epoch ,

Th e root-mean-squar e magneti c fiel d estimat e < B > derive d fro m 1 5 estimate s b y th e proce dur e propose d b y Borr a e t al . (1983 ) i s < B > = 342 24 3 G . Thus , H D 9670 7 i s a magneti c variabl e sta r wit h a perio d o f 2.5530 5 day s an d a n amplitud e o f magneti c fiel d variabilit y abou t 1000 G .
e e


M A G N E T IC

F IE L D

V A R IA B IL IT Y

OF

HD

96707

113

References
B o r r a F . E . , L a n d s t r e e t J . D . , T h o m p s o n I . : 1 9 8 3 , A s t r o p h y s . J . S u p p l . S e r . , 5 3 , 1 5 1 . B y c h k o v V . D . , G a z h u r E . B . , G l a g o l e v s k i j Y u . V . , E l ' k i n V . G . , N a z a r e n k o A . F . , N a j d e n o v I . D . , R o m a n y u k I . I . , C h o u n t o n o v G . A . , S h t o l ' V . G . : 1 9 8 8 , i n : M a g n e t i c S t a r s , E d s . : G l a g o l e v s k i j Y u . V . , R o m a n y u k I . I . , L e n i n g r a d , N a u k a , 1 2 . G a l a z u t d i n o v G . A . : 1 9 9 2 , S A O R e p o r t , N o . 9 2 . H e u v e l E . P . J . V a n D e n : 1 9 7 1 , A s t r o n . A s t r o p h y s . , 1 1 , 4 6 1 . R e n s o n P . , C a t a l a n o F . A . , L e o n e F . : 1 9 9 1 , A s t r o n . A s t r o p h y s . S u p p l . S e r . , 8 9 , 6 1 . N a j d e n o v I . D . , D r a b e k S . V . , B y c h k o v V . D . , R o m a n y u k I . I . , G l a g o l e v s k i j Y u . V . , G a z h u r E h . . , G e o r g i e v O . Y u . : 1 9 8 9 , M i t t e i l u n g e n d e s K a r l - S c h w a r z s c h i l d o b s e r v a t o r i u m s T a u t e n b u r g , 1 2 5 , 1 1 4 . M u s a e v F . A . : 1 9 8 3 , P i s ' m a A s t r o n . Z h . , 1 9 , 7 7 6 . S h t o l ' V . G . : 1 9 9 1 , A s t r o f i z . I s s l e d . ( I z v . S A O ) , 3 3 , 1 7 6 . S l e t t e b a c k A . , C o l l i n s G . W . , B o y c e P . B . , W h i t e N . M . , P a r k i n s o n T . D . : 1 9 7 5 , A s t r o p h y s . J . S u p p l . S e r . , 2 9 , 1 3 7 .