Acquisition and processing of X ray data from Southern Hemisphere sk

Bowyer, C. S.

English

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Space Sciences L a b e r a t o r y  
University of Ca1 i f o r n i a  
Berkeley, Cal i forn ia  94720 
Summary and Current S ta tus  Report 
STUDY OF X-RAY EMISSION FROM SELECTED REGIONS 
OF THE SOUTHERN HEMISPHERE SKY 
Supported by NASA Grant NGR 05-003-278 
Principal  Inves t iga tor :  Professor C .  S t u a r t  Bowyer 
January 1 , 1971 
Space Sciences Laboratory Series 11 Issue 90 
CONTENTS 
I . L I S T  OF PUBLfCATIONS BASED ON WORK SUPPORTED BY 
T H I S  GRANT . . . . . . . . . . . . . . . . . . . . .  
I1 . SUMMARY OF WORK CARRIED OUT I N  1970 . . . . . . . . .  
I11 . W O R K I N P R O G R E S S  . . . . . . . . . . . . . . . . . .  
. . . . . . . . . . . . . . . . . .  I V  . FINANCIAL STATUS 
P a g e  
I .  LIST OF PUBLICATIONS BASED ON WORK SUPPORTED BY THIS GRANT 
Journa l  A r t i c l e s  
"Simultaneous Radio and Op t i ca l  Measurements of Sco XR-1 , "  M. Lampton, 
S. Bowyer, W. J .  Welch, and G.  Grasdalen (submitted t o  Ap. J .  L e t t e r s ) .  
"Feedback Control  of  P ropor t i ona l  Counter Gain," M.  Lampton (submitted 
t o  Rev. S c i e n t i f i c  I n s t r  . ; w i l l  appear i n  January 1971) . 
"X-Ray S c a t t e r i n g  From Grains  i n  t h e  Di rec t ion  of t h e  Crab Pulsar  and 
Sco XR-1," S. Bowyer, M. Lampton, and J. Mack, Nature 225, 1125, 1970. 
"Far U.V.  Photometer f o r  Space Research," S. Bowyer, F.  Paresce,  
M.  Lampton, and J. Mack, P lane ta ry  and Space Science 18 ,  835, 1970. 
"A Search f o r  Rapid Op t i ca l  O s c i l l a t i o n s  i n  Sco XR-1," M .  Lampton, 
S. Bowyer, and S. Harr inqton,  A p .  J. 162, 181, 1970. 
"Detection of X-Ray Emission from 3C273 and NGC 5128," S. Bowyer, 
M .  Lampton, J. Mack, and F. Mendonca, Ap. J .  L e t t e r s  161, L1, 1970. 
"Temperature and Emission Measure P r o f i l e s  of Two Solar  X-Ray F l a r e s , "  
S. Kahler,  R. Krepl in ,  J .  Meekins, and S. Bowyer, A p .  J. 162, 293, 1970. 
" I n t e n s i t y  of t h e  S o f t  X-Ray Background Flux ,"  S. Bowyer and G.  B. F i e l d ,  
Nature 223, 573, 1969. 
0 
"Upper Limits t o  t h e  304 and 584 A Night Helium Glow, S. Bowyer, P.  M.  
Livingston,  and R. D .  P r i c e ,  J. Geophys. R e s .  73, 1107, 1968. 
"Detect ion of an Aniso t rop ic  So f t  X-Ray Background Flux ,"  S. Bowyer, 
G .  B. F i e l d ,  and J .  Mack, Nature 217, 32, 1968. 
Abstracts 
"Measurements of Extreme U l t r a v i o l e t  Radiat ion from Cosmic Sources: 
Instrumentat ion and Prel iminary R e s u l t s , "  F. Paresce,  M. Lampton, 
and S. Bowyer, P u b l i c a t i o n s  A s t r o n o m i c a l  S o c i e t y  o f  the P a c i f i c  8 2 ,  
1037, 1970. 
"Rocket Observations of Extreme U l t r a v i o l e t  Radia t ions  i n  t h e  Night 
Airglow," F. Paresce,  S. Kurnar, M. Lampton, and S. Bowyer, T r a n s .  
Am. G e o p h y s .  U n i o n  11, 1970. 
0 0 .  
" F i r s t  Observations of He1 584 A and H e 1 1  304 A Dayglow Radia t ions ,"  
S .  Kumar, F.  Paresce,  M.  Lampton, and S.  Bowyer, T r a n s .  Am. G e o p h y s .  
Union 11, 1970. 
"On t h e  Poss ib l e  Exis tence of a Dense I n t e r g a l a c t i c  Medium," S. Bowyer 
and G.  B. F i e l d ,  B u l l e t i n  o f  the A m e r i c a n  A s t r o n o m i c a l  S o c i e t y  1 ,  
2 ,  1969. 
"Helium a s  a Major Cons t i tuen t  of  t h e  Jovian Atmosphere," S. Bowyer, 
M .  Lampton, and F. Paresce,  B u l l e t i n  o f  the A m e r i c a n  A s t r o n o m i c a l  
S o c i e t y  1 ,  2 ,  1969. 
"The Attempt t o  Detec t  t h e  E a r t h ' s  Geocoronal Helium Emissions; Pas t  
Resu l t s  and Future  Prospec ts , ' '  S. Bowyer, J. Mack, and F. Paresce ,  
T r a n s .  Am. G e o p h y s .  union 4 9 ,  731, 1968. 
,- - LI. SULWARV OF WORK CARRTED CUT I N  1970 
Analysis of t he  x-ray d a t a  obtained from two payloads flown i n  1969 
from Natal ,  B raz i l ,  was continued. Strong evidence was found f o r  x-ray 
emission from t h r e e  ex t r a -ga l ac t i c  ob jec t s :  M87, 3C273, and NGC 5128 
(Cen A ) .  X-ray emission from M87 had been observed previous ly  by s e v e r a l  
groups and t h e  d e t e c t i o n  of x-rays from 3C273 had been previous ly  repor ted  
a t  t h e  1 13 confidence l e v e l .  The f l u x  de tec ted  on t h e  f l i g h t  f o r  3C273 
was compatible with t h i s  previous measurement wi th in  the  s t a t i s t i c a l  
l i m i t a t i o n s  of t h e  two experiments. 
The x-ray da t a  from Cen A were found t o  f i t  b e s t  a p o i n t  source 
co inc iden t  with the  o p t i c a l  galaxy. An upper l i m i t  t o  t he  s i z e  of t h i s  
source i s  1.5'. No emission was de t ec t ed  from the  extended r a d i o  ha lo .  
The observed x-ray f l u x  of t h i s  o b j e c t  f e l l  below t h e  ex t r apo la t ed  co re  
r a d i o  spectrum. 
Work continued i n  t h e  extreme u l t r a v i o l e t  region of t h e  spectrum 
0 
(100 t o  1000 A ) ,  inc luding  development of labora tory  equipment a s  w e l l  
a s  f l i g h t  experiments. An extremely promising source was developed f o r  
u se  i n  t h e  labora tory  c a l i b r a t i o n  system. The source i s  a cont inuous 
d ischarge  device which provides i n t e n s e  l i n e  emission over a wide range 
0 
of wavelengths t o  below 200 A.  
Two extreme u l t r a v i o l e t  photometers covering the  wavelength ranges 
0 0 
200-800 A and 200-500 A were flown on an Aerobee sounding rocke t  launched 
from White Sands Miss i l e  Range, New Mexico, a t  0955 MST on June 15 ,  1970. 
The XUV dayglow r a d i a t i o n s  measured by these  photometers have been i d e n t i -  
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f i e d  a s  resonant ly  s c a t t e r e d  He I 584 A and He I1 304 A.  Obserirations were 
made i n  t h e  a l t i t u d e  range of 90 t o  185 km. A t  t he  peak a l t i t u d e ,  t h e  
0 
He I 584 A i n t e n s i t y  from the  zen i th  was found t o  be 210 2 70 r a y l e i g h s ,  
0 
while t he  He I1 304 A i n t e n s i t y  was found t o  be 9.5 k 3.1 r ay l e ighs .  The 
a l t i t u d e  p r o f i l e  a s  wel l  a s  t h e  absolu te  i n t e n s i t i e s  can be g ros s ly  accounted 
f o r  on the  b a s i s  of resonant  s c a t t e r i n g  of s o l a r  r a d i a t i o n  from t e r r e s t r i a l  
helium i n  combination with atmospheric- a t t enua t ion  
0 0 
Four photometers covering t h e  wavelength ranges 200-500 A ,  200-800 A ,  
0 0 
700-1100 A ,  and 1050-1500 A were flown on a Nike-Tomahawk sounding rocket  
Launched from Thumbs, India., on March l C ,  1976, at 0205 :ST, A preliminary 
analys is  of the  da ta  obtained has been ca r r i ed  out  and the  r e s u l t s  a r e  
in te rp re ted  a s  the  product of so la r  r ad ia t ion  resonantly sca t tered  by 
hydrogen and helium i n  the  e a r t h ' s  geocorona. Al t i tude  p r o f i l e s  of the  
304 He 11, 584 H e  I ,  and 1216 H I f luxes  have been obtained and a r e  i n  
reasonable agreement with t h e o r e t i c a l  predic t ions .  
A study was made on the  transparency of the  i n t e r s t e l l a r  medium t o  
XW rad ia t ion .  It  was concluded t h a t ,  although the  medium was indeed 
q u i t e  absorbing a t  these wavelengths, the  ex ten t  of t h i s  absorption had been 
overemphasized i n  previous s tudies  and there  is a t  l e a s t  some expectat ion 
t h a t  l imi ted  astronomical observations a t  X W  wavelengths can be made. An 
instrument was developed su i t ab le  f o r  a search f o r  XUV objec ts  i n  the  n ight  
sky and was flown a s  a piggyback experiment on an Aerobee rocket.  A s igna l  
subs tan t i a l ly  above background was observed which may be an X W  source. 
A number of ground-based s tud ies  were ca r r i ed  out  i n  an attempt t o  
understand the  x-ray source Sco XR-1. The Crossley 36-inch telescope a t  
Lick Observatory was used i n  combination with a high-speed data system t o  
search f o r  o s c i l l a t i o n s  i n  the  o p t i c a l  output of t h i s  objec t .  Power 
spect ra  were obtained f o r  frequencies between 0.002 and 500 Hz, which cover 
the  observed range of pulsar  frequencies and the  predicted range of funda- 
mental radial-mode vibra t ions  of white dwarfs and neutron s t a r s .  No 
p e r s i s t e n t  o s c i l l a t i o n s  were detected a t  these frequencies. 
An attempt was made t o  determine the  r e l a t i o n  between the longer-term 
o p t i c a l  va r i a t ions  and the  poss ib le  va r i a t ion  of the radio  output of t h i s  
objec t .  Radio da ta  were obtained using the  NASA 210-ft radio antenna a t  
Goldstone, and simultaneous o p t i c a l  observations were made with the  Crossley 
telescope.  A radio  f l a r e  was observed a s  well a s  a slower va r i a t ion  i n  the  
radio  output  of t h i s  ob jec t .  From a comparison of the  o p t i c a l  and rad io  
da ta  it was c l e a r  t h a t  on any given night  there  was no apparent c o r r e l a t i o n  
between the  o p t i c a l  and radio i n t e n s i t y ;  spetzif ical ly,  the radio Elare 
observed was nei ther  accompanied nor preceded by an o p t i c a l  f l a r e .  Nightly 
,iver,iqc.s of  ktoth C h c .  optical and radio  briqhtnoss were computc-d to search 
i < ) I  \ ' c > s s r  l)li. io1-rcji.r l i , L r n  corri>l,it ions of t h c .  d,lt,i, hil t  no obvi oils i - o r r  r at-ion 
was apparent.  These d a t a  suggest t h a t  encryy i~ not promptly supplied to 
the radio envelope from the cen t ra l  x-ray objec t .  
111. WORK IN PROGRESS 
Work i n  progress can be broken i n t o  two major ca tegor ies :  1) i n s t r u -  
mental development and 2) analys is  of da ta  obtained on previous f l i g h t s  
and from r e s u l t s  of laboratory work. In the  area  of instrument develop- 
ment we have been concentrat ing our e f f o r t s  on s o f t  x-ray de tec to r s .  A 
more complete account of t h i s  work i s  provided i n  a forthcoming proposal 
and w i l l  not be repeated here. I n  regard t o  the  analys is  of da ta  already 
i n  hand from f l i g h t  and laboratory work, we bel ieve we w i l l  have use fu l  
r e s u l t s  i n  the  following areas:  
a )  The poss ib le  de tec t ion  of an XW source. 
A de ta i l ed  analys is  of da ta  from our previous f l i g h t  leads  us t o  
bel ieve t h a t  we may have detected a source rad ia t ing  pr imar i ly  
0 
i n  the  170 t o  600 A band. 
b)  A laboratory source fo r  XUV r ad ia t ion .  
We have developed a simple, compact source of XUV rad ia t ion  which 
provides a s t a b l e  long-l ifet ime source of l i n e  emission a t  wave- 
0 
lengths from 270 t o  1200 A.  This source provides a number of 
d i s t i n c t  advantages over XW sources current ly  employed. 
c )  XUV absorption by the  i n t e r s t e l l a r  medium. 
We have ca r r i ed  ou t  a study which leads us t o  bel ieve t h a t  the  
i n t e r s t e l l a r  medium may be much more transparent  than here tofore  
believed. 
d )  Existence of an i n t e r c l u s t e r  gas i n  a c l u s t e r  of ga laxies .  
We believe we have data  which ind ica te  the presence of an 
i n t e r c l u s t e r  gas i n  a well known c l u s t e r  of galaxies.  
e )  Source Spectrum Data Analysis. 
A number of p ro jec t s  underway require a sophis t ica ted  data  
analys is  program f o r  f u l l  r e a l i z a t i o n .  This i s  especia l ly  
~rnpol-tant at s o f t  x-r,lv cneryies where instrklrnc~ntal broadeninq 
oecorcles prono-i~~iccti . P. co115,l deldble e f fo r t  has been ~radc to 
great1 y i n c r ~ a s e  t i l t .  sor)liist i ca t ion  of the cornputcl- proqram 
employed t o  de r ive  source spec t r a  from f l i g h t  propor t iona l  colrnter 
d a t a ,  The f l i g h t  da t a  a r e  a convolution of t he  t r u e  x-ray source 
mechanism, absorpt ion by t h e  i n t e r s t e l l a r  medium and by t h e  
r e s i d u a l  overhead atmosphere, a l l  i n  combination with the  quantum 
e f f i c i e n c y  of t h e  de t ec to r  and d e t e c t o r  broadening e f f e c t s .  The 
program developed so lves  t he  i n t e g r a l  equat ion 
where : 
2 
G i s  t h e  observed spectrum i n  counts/cm sec keV 
q i s  t h e  d e t e c t o r  e f f i c i e n c y  
T is t e r r e s t r i a l  atmosphere absorpt ion 
N i s  t h e  column dens i ty  of t h e  i n t e r s t e l l a r  medium 
0 is  the  x-ray c ros s  s ec t ion  of t h e  i n t e r s t e l l a r  medium 
F i s  t h e  i n t r i n s i c  source spectrum 
R i s  t h e  instrumental  broadening func t ion  
Y is the  energy channel of t h e  d e t e c t o r  
A is a f i t t i n g  f a c t o r  dependent upon the  source d i s t a n c e  
and s t r eng th .  
The program opera tes  by assuming a form f o r  F(E) , computing t h e  
i n t e g r a l ,  and varying f r e e  parameters u n t i l  t he  b e s t  f i t  wi th  
observa t ions  is  obtained.  The f r e e  parameters a r e  gene ra l ly  N ,  
t he  column dens i ty  of t h e  i n t e r s t e l l a r  medium i n  the  l i n e  of 
s i g h t ,  and T, t h e  source temperature.  Four bas i c  forms f o r  t h e  
t h e  source func t ion  F ( E )  a r e  computed: 
1) Thermal Bremsstrahlung, exponent ial  approximation 
2 )  Thermal Brensstrahlung, Elwert approximation 
3 )  Power Law (synchrotron) 
4 )  Black Body. 
The output  of t he  program c o n s i s t s  of a comparison of t he  goodness 
of f i t  of each of t he  four  types of source func t ions  aga ins t  t h e  
experimental dcka fo r  a w i d r  v a r i e t y  of values of N and T .  This  
permits a dctcrmlnat ion o r  t h e  most probable source mechanism crnti 
, t l so  t-he mosl l i l tely va1uc.s of N and T assoc ia ted  with t h i s  rncch<rni:;~n. 
f )  X-ray source locat ions  and spect ra  i n  t h e  Southern sky. 
We have determined t h e  loca t ion  of t h e  sources we observed i n  the  
Southern sky on our l a s t  f l i g h t .  We have only t o  analyze the  
s p e c t r a l  r e s u l t s  obtained f o r  these  sources with the  a i d  of the  
above program. 
g )  Spectra of ex t raga lac t i c  objec ts .  
We have some spec t ra l  r e s u l t s  on M-87. These da ta  have only t o  
be processed with t h e  a i d  of the  above program t o  provide useful  
r e s u l t s .  
IV. FINANCIAL STATUS 
Our primary source of funding f o r  t h i s  work has been NASA Grant 
NGR 05-003-278. The funds i n  t h i s  g ran t  were exhausted approximately s i x  
months ago; however, it was unnecessary t o  request  addi t ional  funding a t  
t h a t  time because of various stopgap funds we were able t o  obta in  
(primari ly from Manned Spacecraft Center i n  Houston). These funds w i l l  
be f u l l y  expended by March 1, 1971. 


Study of X-ray emission from selected regions of the Southern Hemisphere sky Summary report

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