Balloonborne X ray telescopic observation of point source in Cru

Lewin, W. H. G.

Mc Clintock, J. E.

Ryckman, S. G.

Smith, W. B.

English

NASA Technical Reports Server

I Detection of a High-Energy X-Ray Flare 
from a Source i n  Crux* 
Walter H . G .  Lewin, Jeffrey E.  McClintock 
Stanley G .  Ryckman, and William B. Smith I 
CENTER FOR SPACE RESEARCH 
L ' S E T T S  I S S T I T L  TE O F  T t C H h O L O C k '  
I CSR-P-71-57 March, 1971 
https://ntrs.nasa.gov/search.jsp?R=19710022898 2020-03-11T20:15:20+00:00Z
Detec t ion  of a High-Energy X-Ray Flare 
from a Source i n  Crux* 
Walter  H.G. Lewin, J e f f r e y  E. McClintoek 
S tan l ey  G. Ryckman, and William B. Smi th  
CSR-P-71-57 March, 1 9 7 1  
Detection of a High-Energy X-Ray F la re  
from a Source i n  Crux* 
Walter H. G. Lewin, J e f f r e y  E. McClintock, 
Stanley G b  Ryckman, and W i l l i a m  B. Smith 
Center f o r  Space Research and Department of Physics 
Massachusetts I n s t i t u t e  of Technology 
ABSTRACT 
On 1969 Apr i l  16 we c a r r i e d  ou t  bal loon X-ray 
observat ions from A u s t r a l i a  (energies  above 1 8  k e ~ j  . 
We detec ted  a s t rong  X-ray f l u x  i n  t h e  range 18 t o  
36 keV from a source a t  k' = 301&3O, bs = -2k3O. 
During our observat ions t h e  X-ray f l u x  f l a r e d  up by 
about a fact-or of t h r e e .  The f l a r e  l a s t e d  f o r  a 
per iod of about one and a h a l f  hours. There i s  a l s o  
some evidence f o r  a f l u x  change i n  l e s s  than 
10 minutes. The average observed f l u x  was about 
2 keV ~ m - ~ s e c ' ~ ,  which i s  a t  l e a s t  a f a c t o r  of seven 
higher  than t h a t  observed about one month earlier 
on 1969 March 20  a t  which t i m e  no evidence f o r  X-ray 
emission fram t h i s  region of t h e  sky was found by 
Lewin, McClintock and Smith. The average f l u x  i s  
about a s  high a s  t h a t  observed by Lewin, Clark and 
Smith on 1967 October 15 from a source a t  2% = 304.8*1.5', 
b* = -1.5k2O. 
- 
This work supported by t h e  5. National  Aeronautics and 
Space Administration (gran~'~2-009-015) , t h e  Nat ional  Science 
Foundation (g ran t  GP-9365), and t h e  Off ice  of Naval Research. 
During a  ba l loon  f l i g h t  from Mildura,  A u s t r a l i a ,  on 
1969 A p r i l  16 ,  w e  c a r r i e d  o u t  X-ray obse rva t ions  of t h e  reg ion  
of t h e  sky from which we-had e a r l i e r  observed a s t r o n g  flux 
(Lewin, Clark and Smith,  1968b; 1 9 6 8 ~ ) .  On 1969 March 2 0 ,  
one month be fo re  t h e  p r e s e n t l y  r e p o r t e d  o b s e r v a t i o n s ,  we 
d i d  n o t  d e t e c t  any X-rays from t h i s  r eg ion  (Lewin, McClintack 
and Smith,  1976) .  However, on 1969 A p r i l  1 6  we d e t e c t e d  a 
f l u x  about  as s t r o n g  as t h a t  d e t e c t e d  on 1967 October 1 5 ,  
We used our  358cm2 NaT(Tl) s c i n t i l l a t i o n  d e t e c t o r  sur- 
rounded by an an t i co inc idence  j a c k e t  of p l a s t i c  s c i n t i l l a t o r ,  
The f i e l d  of view had an angu la r  width of 13' FWEM. A detailed 
d e s c r i p t i o n  of t h e  ins t rument  i s  g iven  e lsewhere  (Clark ,  Lewin 
and Smith, 1 9 6 8 ) .  A s  a r e s u l t  of mal func t ion ing  cutdown 
dev ices  t h e  ins t rument  sp lashed  down i n  t h e  Tasman Sea a f t e r  
a  -16 hour f l o a t  a t  a l t i t u d e s  above 130,000 f t .  The t e l e scope  
wi th  t h e  on-board d a t a  f i l m  washed up i n  N e w  Zealand n i n e  
months l a t e r .  A s p e c i a l  p rocess ing  technique which made t h e  
d a t a  on t h e  f i l m  l e g i b l e  was developed by Kodak Research 
Labora to r i e s .  There i s  no ambiguity i n  t h e  d a t a ;  however, t h e  
q u a l i t y  of t h e  f i l m  i s  poor;  read ing  t h e  d a t a  from t h e  f i l m  
cannot  be automated and i s  consequent ly  extremely 
time consuming. Therefore ,  a l though X-rays were d e t e c t e d  i n  
7 energy channels  i n  t h e  energy range from 18 t o  -105 k e V ,  
we have s o  f a r  analyzed on ly  t h e  d a t a  ob ta ined  i n  a  "sum 
channel" which groups t h e  f i r s t  t h r e e  channels  cover ing  t h e  
energy range from -18 t o  36 keV. 
h m During t h e  obse rva t ions  desc r ibed  he re  between 11 10 
and 1 5 ~ 1 0 ~  U.T. t h e  t e l e s c o p e  a x i s  was i n c l i n e d  29.5' t o  
t h e  v e r t i c a l  and was cont inuous ly  r o t a t e d  i n  azimuth wi th  
an average pe r iod  of about  7 minutes. I n - f l i g h t  c a l i b r a t i o n  
every  20 minutes w i th  an ~m~~~ source  demonstrated no change 
of any s i g n i f i c a n c e  i n  t h e  boundar ies  of t h e  sum channel ,  
Background r a t e s  were determined by averaging d a t a  over 
400  s e c  i n t e r v a l s ,  exc lud ing  those  p e r i o d s  when obvious sources  
w e r e  i n  t h e  f i e l d  of view, The va lues  t h u s  ob ta ined  were used 
wi th  l i n e a r  i a t e r p o l a t i o n  t o  c a l c u l a t e  t h e  background count ing  
r a t e  a t  any d e s i r e d  i n s t a n t .  A c o r r e l a t i o n  between t h e  
background count ing r a t e  and t h e  azimuthal  d i r e c t i o n  of t h e  
ins t rument  was found; t h e  count ing rate w a s  h i g h e s t  when t h e  
ins t rument  was p o i n t i n g  toward t h e  sou th-southeas t  and lowest  
when t h e  ins t rument  was p o i n t i n g  toward t h e  nor th-nor thwest ,  
Maximum d i f f e r e n c e s  from t h e  average va lue  w e r e  +2.5 p e r c e n t  
and -1.5 pe rcen t .  W e  have taken  t h i s  azimuthal  dependence 
of t h e  background i n t o  accouht ,  a l though it had only a  small 
e f f e c t  on t h e  r e s u l t s  ob ta ined .  
The azimuth o f  t h e  t e l e s c o p e  a x i s  w a s  measured cont inuous ly  
by magnetometers which were c a l i b r a t e d  i n - f l i g h t  by a  sun sensor, 
The d i r e c t i o n  of  t h e  t e l e s c o p e  a x i s  could be  determined within 
approximately 1.5'. The X-rays t h a t  w e  have d e t e c t e d  
can be a t t r i b u t e d  t o  a s i n g l e  source  whose maximum 
l i k e l i h o o d  p o s i t i o n  i s  fiS = 301?3O, b5 =-2?3O. 
I t  s e e m s  l i k e l y  t h a t  t h e  f l u x  r e p o r t e d  h e r e  i s  due t o  
t h e  h i g h l y  v a r i a b l e  source  a t  g a l a c t i c  l ong i tude  R - 301", 
which i s  desc r ibed  i n  t h e  fo l lowing  paper  (McClintock, Ricker 
and Lewin, 1971) . However, w e  cannot  exclude t h e  p o s s i b i l i t y  
t h a t  some o r  a l l  of t h e  f l u x  comes from t h e  h i g h l y  v a r i a b l e  
source  a t  g a l a c t i c  l ong i tude  kz - 304O which w e  f i r s t  de t ec t ed  
on 1967 October 15 (Lewin, Clark and Smith, 1968b; 1 9 6 8 ~ ;  
Lewin, McCEintock and Smith, 1970; see a l s o  fo l lowing  paper), 
The accuracy i n  t h e  de te rmina t ion  of t h e  g a l a c t i c  longitude 
of t h e  X-ray source  Cen XR-2, which i s  a l s o  v a r i a b l e ,  has recently 
been improved by Francey (1971) as a r e s u l t  of a r e - ana lys i s  
of  t h e  A p r i l  2 0 ,  1967 r o c k e t  d a t a  (Francey -- e t  al. 19671, H e  
-rc 
now r e p o r t s  a va lue  of R O =  320,2+1°. I f  t h i s  de te rmina t ion  
i s  c o r r e c t ,  w e  must conclude t h a t  t h e  high-energy flux 
t h a t  w e  have d e t e c t e d  . i n  1967 and 1969 ( t h i s  paper)  
i s  n o t  due to .Cen XR-2, b u t  i s  due t o  a t  leas t  one new 
v a r i a b l e  high-energy source .  I t  i s  i n t e r e s t i n g  t o  no te  
t h a t  t h e  AS&E group r e c e n t l y  (1970 December 27) observed a 
source  (F1) a t  g a l a c t i c  l ong i tude  303.7f 0.50' (Giacconi 
e t  a l . ,  1971) .  
--
We c a l c u l a t e d  t h e  average f l u x  from t h e  source  over  33  
scans  wi th  a t o t a l  e f f e c t i v e  exposure of  - 2 . 3  x l o 5  cm2see, 
W e  ob ta ined  t h e  average observed i n t e n s i t y  i n  t h e  energy channel 
18 t o  36 keV by t a k i n g  i n t o  account t h e  angu la r  response 
f u n c t i o n  of t h e  d e t e c t o r  a t  each moment t h a t  d a t a  w e r e  
r ecorded ,  and by c o r r e c t i n g  f o r  a tmospher ic  absorp t ion .  
'we have es t imated  t h i s  g a l a c t i c  l ong i tude  from f i g u r e  4 of 
t h e  AS&E paper.  
W e  fol lowed t h e  procedure desc r ibed  i n  an e a r l i e r  paper 
(Clark ,  Lewin and Smith, p.30, 1968) .  The r e s u l t s  depend on 
t h e  assumed form of t h e  spectrum i n c i d e n t  on t h e  E a r t h ' s  
atmosphere. W e  have assumed h e r e  two forms of t h e  energy 
spectrum: a power law of  t h e  form J (E)  dE a E - ' ~ E  with 
A - 1.5  and an exponen t i a l  of  t h e  farm J (E)dE  a e -E/kTdE 
wi th  kT - 5 k e V .  
I n  Table  1 We l i s t  r e s u l t s  of  f o u r  ba l loon  obse rva t ions  
cover ing  t h e  r eg ion  i n  Cen-Crux nea r  t h e  g a l a c t i c  p l ane ,  
The r e s u l t s  shown i n  t h e  t h i r d  column a r e  c a l c u l a t e d  energy 
f l u x e s  c o r r e c t e d  t o  ze ro  a tmospher ic  t h i ckness .  I n  c o l  
w e  l i s t  t h e  g a l a c t i c  coo rd ina t e s  of  r e p o r t e d  source  p o s i t i o n s  
de r ived  under t h e  assumption t h a t  on ly  one source  was predomi- 
n a n t l y  r e s p o n s i b l e  f o r  t h e  d e t e c t e d  high-energy f l u x .  W e  conclude 
t h a t  between 1969 March 20 and 1969 A p r i l  16 t h e  f l u x  i n  
t h e  18 - 36 keV energy range from t h e  source  r epo r t ed  h e r e  
equa to r  i n  t h e  v i c i n i t y  of  8 - 300° - 305O inc reased  by a t  
l e a s t  a f a c t o r  of 7 .  
An a n a l y s i s  of  each of  t h e  33 scans  over  t h e  source  
h m h m between 11 10 and 15 10 U.T. on A p r i l  16,  1969 was c a r r i e d  
o u t  u s ing  a method desc r ibed  i n  d e t a i l  i n  an ear l ier  paper  
(Lewin, Clark and Smith, 1968a) .  W e  have taken i n t o  
account  on ly  t h e  d a t a  f o r  which t h e  corresponding co l l ima to r -  
response func t ion  f (exposed f r a c t i o n  of s e n s i t i v e  c r y s t a l  
a r e a )  was g r e a t e r  than  0.30. F u r t h e r ,  w e  have inc luded  only 
t h o s e  28 scans  f o r  which, under t h e  above c o n d i t i o n ,  t h e  
e f f e c t i v e  exposure t i m e  t o  t h e  source  w a s  g r e a t e r  than 
- 1 0  seconds. 
Figure 1 shows t h e  source i n t e n s i t y  (18 - 36 keV) for 
t hese  scans p l o t t e d  versus Universal  Time. The i n t e n s i t i e s  
have been correc ted  t o  an atmospheric th ickness  of 3.50 g 
(average of l i n e  of s i g h t  t o  t h e  source) .  The cor rec t ions  
were l e s s  than 1 0 %  f o r  each scan. 
The X-ray f l u x  increased  by a t  least a  f a c t o r  of t h r e e  
h m between 1 3 ~ 4 5 ~  and 1 4  30 U.T. There seems t o  be some 
evidence t h a t  t h e  f l u x  t h e r e a f t e r  decreased rap id ly  ( i n  less 
than 1 0  minutes) ,  increased again,  and then decreased i n  a 
per iod of aboilt 30 minutes. A X2 f i t  t o  a cons tant  source 
i n t e n s i t y  gave a  value of 4 5  f o r  t h e  28 po in t s  p l o t t e d ,  
Acknowledgements 
A g r e a t  many people have cont r ibuted  t o  t h e  success  of 
these  bal loon observat ions.  W e  be l i eve  t h a t  the  most valuable  
con t r ibu t ion  was made by M r .  J. C. Hodgson and M r .  W. R, Simpson 
who found t h e  payload on Ka i t a i a  beach i n  New Zealand. We 
a l s o  a r e  very g r a t e f u l  t o  t h e  po l i ce  i n  Ka i t a i a ,  t o  t h e  
Direc tor  of t h e  Oceanographic I n s t i t u t i o n  i n  Wellington, 
t o  t h e  Defense a t t ach6  i n  Wellington, Captain Haz le t t ,  and 
t o  L t .  Col. S t .  George of t h e  DEA i n  Washington who made 
it poss ib le  f o r  t h e  recovered payload and f l i g h t  f i lm 
t o  be re turned  t o  M.I.T. We a r e  extremely g r a t e f u l  t o  
D r .  Chi lders  and Mssrs. Henn, Hahn, Swann, P a s s a r e l l ,  and 
Ol ivares  of Kodak Research Laborator ies  i n  Rochester, New York 
f o r  developing a  s p e c i a l  technique t h a t  make t h e  d a t a  on the  
d e t e r i o r a t e d  E l i g h t  f i l m  l e g i b l e .  We thank J. H i l l i e r ,  
D. S c o t t  and t h e  s t a f f  of t h e  Balloon Launching S t a t i o n  a t  
~ i l d u r a ,  A u s t r a l i a ,  f o r  c a r r y i n g  o u t  t h e  f l i g h t .  W e  a l s o  
wish t o  thank R. L e s l i e  and t h e  Aus t r a l i an  Min i s t ry  of 
Supply f o r  t h e i r  coopera t ion .  We a r e  g r a t e f u l  t o  t h e  staff 
of t h e  Meteorology Department i n  Mildura f o r  t h e i r  coopera t ion  
and w e  thank B i l l  Wilson of t h e  O f f i c e  of Naval Research 
f o r  h i s  encouragement, enthusiasm and h e l p f u l  sugges t ions ,  

Fisure Caption 
F igure  1: X-ray i n t e n s i t y  (18  - 36 keV) from a source  
a t  2% = 30i i3 ' ,  bG = -2i3', a s  observed 
on A p r i l  16 ,  1969. The i n t e n s i t i e s  (counts  ~ e c - ~ 3 5 8 - '  
~ r n ' ~ )  f o r  t h e  28  scans  over  t h e  source  have been cor-  
r e c t e d  t o  an a tmospher ic  t h i c k n e s s  of 3.50 g ~ m ' ~ ;  
c o l l i m a t o r  response has  been taken i n t o  account.  

References  
C l a r k ,  G, W,, Lewin, We H. G., and Smith ,  W. B . ,  1968 
Ap. J . ,  - 151,  21. 
Francey,  R ,  J . ,  Fenton,  A. G . ,  H a r r i e s ,  J. R,, and 
McCracken, K.  G . ,  1967 Nature - 216, 773.  
F rancey ,  R. J., 1971 p r e p r i n t .  
Giaccon i ,  R . ,  Kel logg,  E . ,  Go rens t e in ,  P.I Gursky, H., 
and Tananbaum, K .  1971 p r e p r i n t  submi t t ed  t o  Ap. S, 
Lewin, W. H .  G . ,  C l a r k ,  G .  W . ,  and Smith ,  W. B. 1968a 
Ap. J. ( L e t t e r s ) ,  - 152,  L49. 
196833 
i b i d ,  L55. 
1968c 
Nature ,  219, 1235. 
-
Lewin, W. H. G . ,  McClintock, J. E . ,  and Smith,  W.  B. 1970 
Ap.  J. ( L e t t e r s ) ,  - 159,  L193. 
McClintock, J. E . ,  R i cke r ,  G .  R . ,  Jr. ,  and Lewin, W. H, G. 
1971 submi t t ed  t o  Ap.  J. ( L e t t e r s ) .  


Detection of high-energy X-ray flare from a source in Crux

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