Low resolution International Ultraviolet Explorer (IUE) spectroscopic observations of two magnetic white dwarfs BPM25114 and K813-14 were obtained using both the SWP and LWP cameras. The first object has an observed magnetic field of 4 x 10(7) Gauss and the second has one of 3 x 10(7) Gauss. Both objects have overall spectral energy distributions appropriate for cool DA white dwarfs with T(eff) near 10,000 K and accordingly show strong lambda lambda 1400 and 1600 absorption in their spectra. Compared to non-magnetic DA white dwarfs of comparable effective temperature, there are some differences in the profiles, presumably produced by the magnetic fields in these objects. In addition, the ultraviolet spectra of a number of hot subluminous stars in the Kiso Schmidt survey were observed

Wegner, Gary A.

English

NASA Technical Reports Server

Semi-Annual Repor t  
F o r  NASA Grant  NAG5-287 
N a t i o n a l  A e r o n a u t i c s  and  Space A d m n i s t r a t i o n  
IUE Guest  Observer  Program 
Goddard Space F l i g h t  C e n t e r  
G r e e n b e l t ,  MD 20771 
U l t r a v i o l e t  S p e c t r a  o f  Two Magnet ic  
White D w a r f s  
and  
U l t r a v i o l e t  S p e c t r a  o f  Subluminous O b j e c t s  Found 
i n  t h e  Ki so  Schmidt Survey  
[BWSA-GB-182122) USLTBAVIOLETSPECTWAOPTBO M87-2S30Q 
BWGEEPIC &H%TE DHABYS bHB ULTRBYXQEET 
SPECTRA 01E;" S U B Z U B E I O U S  OBJECTS POUED IH X R ' Z  
8150 SCBFlPBT S U B B E Y  Semianaaal Repost, 1 Uaclas 
Jan, - 30 June ,9987 {Daskaoath ColH, ) 3 1 g G3d89 0083988 
Submi t t ed  by :  Gary A .  Wegner 
a n d  Astronomy 
Phone: 603/646-3329 
T r u s t e e s  of Dartmouth C o l l e g e  
PO Box 7  
Hanover, NH 03755 
D u r a t i o n :  One Year 
J a n u a r y  1, 1987 t o  June  30, 1987 
~ a r y  A. ~ e n e r  
P r i n c i p a l  I n v e s t i g a t o r  
https://ntrs.nasa.gov/search.jsp?R=19870016471 2020-03-20T10:51:13+00:00Z
ABSTRACT 
During t h e  l a s t  semi-annual p e r i o d ,  t h e  research work 
connec ted  w i t h  G r a n t  NAG5-287 f rom t h e  N a t i o n a l  Aeronau t i c s  and 
Space A d m i n i s t r a t i o n  has been  t o  c a r r y  o u t  two p r o j e c t s  i n  
c o n j u n c t i o n  w i t h  t h e  International Ul t rav io le t  Explorer ( I U E )  
s a t e l l i t e .  These are:  (1) t o  s tudy  t h e  u l t r a v i o l e t  s p e c t r a  o f  t h e  
two magnet ic  whi te  dwarfs BPM25114 and K813-14, and ( 2 )  t o  look  a t  
t h e  u l t r a v i o l e t  s p e c t r a  of subluminous s t a r s  i d e n t i f i e d  from v i s u a l  
wavelength spec t roscopy  t h a t  had been o r i g i n a l l y  d i s c o v e r e d  from 
t h e  Kiso Schmidt su rvey  f o r  u l t r a v i o l e t  e x c e s s  s tars .  
2 
INTRODUCTION 
The purpose of t h e  research w i t h  t h e  International Ul t rav io le t  
Explorer ( I U E )  being reported here has been twofold. T h e  f i r s t  
p ro jec t  t o  be discussed was t o  observe t h e  u l t r a v i o l e t  spec t r a  of 
hot subluminous s t a r s  t h a t  were o r ig ina l ly  found i n  t h e  Kiso 
Schmidt u l t r a v i o l e t  excess survey by Noguchi, Maehara, and Kondo 
(1980) and Kondo, Noguchi, and Maehara (1984) which have been 
observed spec t roscopica l ly  f r o m  t h e  ground i n  a continuing s t u d y  
f o r  which t h e  papers:  Wegner and  McMahan (1985,1986) and Wegner, 
McMahan, and Boley (1987) have already been published. The proposed 
observations progressed w e l l  and  were completed during t h e  per iod 
covered by t h i s  report  and t h e  new data obtained with t h e  IUE 
under t h e  auspices of NASA Grant NAG5-287 a r e  summarized i n  
Table I .  
Observations of t h e  u l t r a v i o l e t  spectra  of t h e  two magnetic DA 
white dwarfs BPM25114 and K813-14 using both t h e  low re so lu t ion  LWP 
and SWP cameras w e r e  a l s o  completed. This was proposed a s  a follow 
up on t h e  work reported i n  Nelan and Wegner (1985) where t h e  s t rong 
f ea tu res  found near hh1600 and 1400 i n  t he  spec t ra  of t h e  cooler 
examples of t h e  non-magnetic DA wh i t e  dwarfs w e r e  a t t r i b u t e d  t o  t h e  
H2 and H2+ quasi-molecules. The f i r s t  object  BPM25114 has an 
observed magnetic f i e l d  of 4x107 Gauss and t h e  second, K813-14 has 
one of 3x107 Gauss. These observations a r e  summarized i n  Table 11. 
The o p t i c a l  spec t r a  of these  objects and t h e  de r iva t ions  of t h e  
magnetic f i e l d s  have been described i n  Wegner ( 1 9 7 7 ) ,  Martin and 
3 
Wickramasinge (1978), Wickramasinghe and Martin ( 1 9 7 9 ) ,  Liebert  et  
al. (1985) and Wegner and McMahan (1985).  
11. OBSERVATIONAL RESULTS 
The I U E  u l t r a v i o l e t  spectra  of t h e  magnetic DA w h i t e  dwarfs 
have continued t o  reveal  t h e  presence of t h e  xh1600 and 1 4 0 0  
absorpt ions which have been s t u d i e d  i n  e a r l i e r  years i n  t h e  spectra  
of t h e  cooler  examples of t h i s  c lass  of s t a r s .  The SWP spec t ra  of 
both ob jec t s  a r e  shown i n  Figures 1 and 2 and f o r  comparison, l i k e  
spec t r a  of t h r e e  non-magnetic DA s t a r s  of comparable e f f e c t i v e  
temperature a r e  given i n  Figures 3 and 4 .  Both BPM25114 and K813-14 
have o v e r a l l  s p e c t r a l  energy d i s t r ibu t ions  appropriate  f o r  cool DA 
white dwarfs with Teff  near 10 ,000  K .  Compared t o  t h e  non-magnetic 
DA w h i t e  dwarfs , the p r o f i l e s  of hh1600 end 1 4 0 0  appear t o  be 
deeper, presumably an e f f e c t  produced by t h e  magnetic f i e l d s  i n  
these ob jec t s .  
The u l t r a v i o l e t  port ions of t h e  spec t ra  of some of t h e  Kiso 
u l t r a v i o l e t  excess objec ts  a r e  shown i n  Figures 5 and 6 .  Figure 5 
shows t h e  u l t r a v i o l e t  and v isua l  port ions of the  spectrum of t he  V 
= 1 7 . 1  Kiso u l t r a v i o l e t  excess o b j e c t  KUV01584-0939 which appears 
t o  be a new cataclysmic type var iab le .  I n  t h e  v i s i b l e  port ion of 
t h e  spectrum it shows a s t rong blue continuum and marked H e  I1 
emission notably near hh 4 6 8 6  and 5411 a s  w e l l  a s  emission f ea tu res  
a t  t h e  l oca t ions  of t h e  Balmer l i nes  which could be due t o  e i ther  
4 
H e  o r  H .  
these  f e a t u r e s .  Although obtained w i t h  only a one hour ' s  
i n t eg ra t ion ,  t h e  I U E  
i n  t h e  u l t r a v i o l e t  confirms t h e  hot continuum and a l s o  revea ls  t h e  
presence of addi t iona l  emission l i n e s  near hh 1 6 4 0  and 1243. 
Further  observation shows spectroscopic v a r i a b i l i t y  i n  
observation of t h i s  r e l a t i v e l y  f a i n t  object  
Figure 6 shows a fu r the r  example of another of t h e  recent ly  
observed ob jec t s .  T h i s  object ,  K789-37 = PG12252-0757 was shown by 
Kilkenny ( 1 9 8 6 )  t o  be a DZA white dwarf on t h e  b a s i s  of ground 
based observat ions.  The I U E  spectroscopy shows t h a t  t h i s  s t a r ' s  
u l t r a v i o l e t  spectrum i s  r i c h  i n  me ta l l i c  l i n e s  l i k e  some of t he  D Z  
s t a r s  analyzed r e c e n t l y  by Zeidler-K.T., Weidemann, and Koester 
(1985), although it appears t o  be p a r t i c u l a r l y  i n t e r e s t i n g  f o r  
studying accre t ion  and mixing processes i n  t h e  atmospheres of white 
dwarfs due t o  t h e  presence of hydrogen i n  i t s  v i s i b l e  spectrum. An 
atmospheric abundance ana lys i s  of t h i s  ob jec t  using these  da ta  i s  
planned. 
111. CONCLUSIONS 
During t h e  f i r s t  ha l f  of 1987,  work has continued t o  be 
conducted on subluminous s t a r s .  The bas i c  r e s u l t s  of these  
inves t iga t ions  can be summarized b r i e f l y  a s  follows: 
1) Observations have been completed on t h e  two magnetic cool 
DA white dwarfs and t h e y  a l l  show t h e  presence of t h e  n1400 and 
1 6 0 0  absorptions,  although t h e  r e l a t i v e  s t r eng ths  and wavelengths 
seem t o  be a f f ec t ed  by t h e  magnetic f i e l d s .  
2 )  T h e  u l t r a v i o l e t  spectra  of a number of hot subluminous 
5 
stars in the Kiso Schmidt survey have been observed. 
REFERENCES 
Kilkenny, D. , 1986,  Observatory, 106, 201.  
Kondo, M., Noguchi, T., and Maehara, H., 1984, Ann. Tokyo Astron. 
O b s . ,  2 0 ,  1 3 0 .  
Liebert, J., Schmidt, G. D., Sion, E. M. , Starrfield, S. G. , Green, 
R. F., and Boroson, T. A., 1985, Publ. Astron. SOC. P a c . ,  
97, 1 5 8 .  
Martin, B. and Wickramasinghe, D. T., 1978, Mon. Not. R. Astr. 
SOC. , 183, 5 3 3 .  
Nelan, E. P. and Wegner, G. 1985, Astrophys. J. (Letters), 
289, m i .  
Noguchi, T . ,  Maehara, H., and Kondo, M., 1980, Ann. Tokyo Astron. 
O b s . ,  20, 130. 
Wegner, G., 1977, Mem. SOC. Astr. Ital., 48, 2 7 .  
Wegner, G. and McMahan, R. K., 1985, Astron. J., 90, 1 5 1 1 .  
Wegner, G. and McMahan, R. K., 1986, Astron. J., 91, 1 3 9 .  
Wegner, G. and McMahan, R. K., and Boley, F. I., 1987, Astron. J., 
in press. 
Wickramasinghe, D. T. and Martin,B., 1979, Mon. Not. R. Astr. SOC., 
188, 1 6 5 .  
Zeidler-K.T., E.-M., Weidemann, V. , and Koester, D. , 1985, Astron. 
Astrophys. , 155, 3 5 6 .  
6 
A P P E N D I X  I. 
T h e  f o l l o w i n g  abs t rac ts  are of papers o n  t h e  mater ia l  
d i s c u s s e d  i n  t h i s  report  t h a t  were p r e s e n t e d  a t  s c i e n t i f i c  m e e t i n g s  
d u r i n g  t h e  l a s t  s e m i - a n n u a l  p e r i o d .  
A .  J o i n t  M e e t i n g  of t h e  Amer ican  A s t r o n o m i c a l  S o c i e t y  a n d  t h e  
C a n a d i a n  A s t r o n o m i c a l  S o c i e t y ,  June  18 ,  1987 i n  Vancouver ,  B. C . ,  
Canada ( B u l l .  of the A . A . S . ,  19, 756 [ 1 9 8 7 1 ) .  
U l t r av io l e t  IUE Spectroscopy of t he  Two Magnetic White 
Dwarfs BPM25114 and K813-14 
Gary Wegner (Dartmouth College) 
Low reso lu t ion  IUE spectroscopic observations of two 
magnetic white dwarfs have been obtained using both t h e  
SWP and LWP cameras. The f i r s t 7 0 b j e c t  BPM25114 has an 
observed magnetic f i e l d  of 4x10 Gauss and the  second, 
K813-14 has one of 3x10 Gauss. Both o b j e c t s  have o v e r a l l  
s p e c t r a l  energy d i s t r i b u t i o n s  appropriate  f o r  coo l  DA 
white dwarfs wi th  T 
show strong m 1 4 0 0  and 1600 absorption i n  t h e i r  spectra. 
Compared t o  non-magnetic DA white dwarfs of comparable 
e f f e c t i v e  temperature, there  are some d i f f e rences  i n  t h e  
p r o f i l e s ,  presumably produced by t h e  magnetic f i e l d s  i n  
these  ob jec t s .  
7 
near 10,OOO°K and accordingly e f f  
This work w a s  p a r t i a l l y  supported by t h e  National 
Aeronautics and Space Administration through Grant NAG5- 
287 and the  Nat ional  Science Foundation Grant AST85-15219. 
7 
B .  I A U  C o l l o q u i u m  N o .  95,  "The Second C o n f e r e n c e  on F a i n t  B l u e  
S t a r s , "  J u n e  1, 1 9 8 7  i n  Tucson ,  A r i z o n a .  
SPECTROSCOPIC SURVEYS OF FAINT BLUE STARS 
Gary Wegner, Forrest I. Boley and Steven R. Swanson 
Dartmouth College 
Robert K. McMahan 
Smithsonian Astrophysical Observatory 
Since 1984, approximately 450 faint blue stars brighter than n+, - 
17.0 magnitude, mostly from the Kiso S c W d t  ultraviolet excess survey, 
have been observed spectroscopically at 8 A resolution in the 
wavelength interval 4000 - 7000 A. The intensified Reticon scanner of 
the Mark I1 spectrograph on the 1.3 m telescope of the McGraw-Hill 
Observatory has been used for the observations. As well, some of the 
spectra of the brighter more interesting objects have been observed in 
the ultraviolet using the low resolution mode of the IUE satellite. So 
far, these observations have yielded a substantial number of 
interesting systems for further study. Here, we concentrate on the 
stellar sources, present descriptions of the spectra of several of 
them, and discuss some preliminary statistical results. This work was 
partially supported by Grant ASTSS-15219 from the National Science 
Foundation and Grant NAGS-287 from the h'ational Aeronautics and Space 
Administration. 
I I 
BPM 25114 
- 9.0 
4 m 
C 
0 u
+ r.2 -9.5 
u 
01  - 
- 10.0 
Figure I: The SWP spectrum of the magnetic 
white dwarf BPM25114. 
Figure.2: The same spectral region, but for the 
magnetic white dwarf K813-14. 
-9.0 t 
K 813- I4 
2 In
C 
8 
.+ -9.5 
B 
0)  
0 -
-10.0 
1300 1400 1500 1600 1700 1800 1900 
9 
- 
v) 
C 
0 
0 + 
R 
LL cn 
0 -
1200 1400 I6 00 1800 
i c A 1  
Figure 3: Examples of the SWP spectra of two 
non-magnetic DA white dwarfs. 
1200 1400 1600 1800 
)&A, 
Figure 4 :  Spectrum of an additional cool non- 
magnetic DA white dwarf. 
10 
U
 
E 3
h
 
K789-37 
-10 
1250 I500 I750 
G 
0 
0 
i- 
W 
z" -9 
L i z  
9 
- 10 
1950 
K789-37 
Do 2450 2700 
x3 
2950 3200 
Figure  6 :  T h e  u l t r a v i o l e t  spectrum of the DZA w h i t e  dwarf K789-37 a s  observed 
w i t h  the  I U E .  The  p o r t i o n  o f  the spectrum d e r i v e d  from the Swp image i s  a t  the  
t o p  and t h a t  f rom the LWP i s  be low.  Note the richness o f  s p e c t r a l  f e a t u r e s  i n  
the spectrum o f  t h i s  o b j e c t .  
12 
Table I 
Object 
K i s o  Objects Obse rved  w i t h  t h e  L U  
u n d e r  t h e  A u s p i c e s  of G r a n t  NAG5-287 f o r  P r o j e c t  SDIGW 
K685-09 
K685-09 
K345-30 
K345-30 
K494-04 
K494-04 
K433-03 
K789-37 
K789-37 
K789-37 
K433-03 
K1037-11 
K433-05 
Date of 
Obse r v a t  i o n  
December 30, 1 9 8 6  
December 30, 1 9 8 6  
December 30, 1 9 8 6  
December 30, 1 9 8 6  
December 30, 1 9 8 6  
December 30, 1 9 8 6  
December 31, 1 9 8 6  
December 31, 1 9 8 6  
J a n u a r y  1, 1987  
January 1, 1987  
January 1, 1987  
J a n u a r y  4 ,  1987  
F e b r u a r y  24, 1 9 8 7  
Image 
Number 
~ ~ ~ 9 8 2 5  
SWP2 9994 
LWP9826 
SWP29995 
~ ~ ~ 9 8 2 7  
SWP2 9996 
IJWP9828 
LWP9830 
LWP9836 
SWP30001 
SWP 3 0 002 
SWP30020 
SWP30374 
Object 
Log of Observa 
K813-14 
K 8 1 3 - 1 4  
BPM2 51 1 4  
BPM2 51 1 4  
13 
T a b l e  I1 
i o n s  f o r  t h e  Two ! ,dgne t i c  W h i t e  D w a r f s  
f o r  P r o j e c t  W D I G W  of G r a n t  NAGS-287 
Date of B 
O b s e r v a t i o n  
J a n u a r y  4,  1 9 8 7  
J a n u a r y  5, 1987  
F e b r u a r y  2 4  1987  
F e b r u a r y  2 5  1987  
Image 
Number 
LWP9856 
SWP30025 
LWP 10187 
SWP30386 


Ultraviolet Spectra of Two Magnetic White Dwarfs and Ultraviolet Spectra of Subluminous Objects Found in the Kiso Schmidt Survey

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