COS-B had Cyg X-3 within its field of view during 7 observation periods between 1975 and 1982 for in total approximately 300 days. In the skymaps (70 meV  E  5000 meV) of the Cyg-X region produced for each of these observations and in the summed map, a broad complex structure is visible in the region 72 deg approximately less than 1 approximately less than 85 deg, approximately less than 5 deg. No resolved source structure is visible at the position of Cyg X-3, but a weak signal from Cyg X-3 could be hidden in the structured gamma-ray background. Therefore, the data has been searched for a 4.8 h timing signature, as well as for a source signal in the sky map in addition to the diffuse background structure as estimated from tracers of atomic and molecular gas

Bennett, K.

Bignami, G. F.

Bloemen, J. B. G. M.

Buccheri, R.

Caraveo, P. A.

Hermsen, W.

Mayer-Hasselwander, H. A.

Oezel, M. E.

Pollock, A. M. T.

Strong, A. W.

English

Bignami, G.F.

Bloemen, J.B.G.M.

Caraveo, P.A.

Mayer-Hasselwander, H.A.

Oezel, M.E.

Pollock, A.M.T.

Strong, A.W.

NARCIS 

CYG X-3: Not seen in high-energy gamma rays by COS-B

Leiden University Scholary Publications

NASA Technical Reports Server

95 OG 2.2-2
CYG X-3: NOT SE_q IN HIGH-ENERGY GAMMA RAYS BY COS-B
W.Hermsen I , K.Bennett 6, G.F.Bignami 2, J.B.G.M.Bloemen la, R.Buccheri 3,
p.A.Caraveo 2, H.A.Mayer-Hasselwander 4, M.E. Ozel b, A.M.T.Pollock 5c,
A.W.Stron_
The Caravane Colaboration for the COS-B satellite:
I Laboratory for Space Research Leiden, Leiden, The Netherlands
2 Istltuto di Fisica Cosmica del CNR, Milano, Italy
3 Istituto di Fisica Cosmica e Informatica del CNR, Palermo, Italy
4 Max Planck Institut fiir Physik und Astrophysik, Institut f_r
Extraterrestrische Physik, Garching-bei-Mttnchen, Germany
5 Service d'Astrophysique, Centre d'Etudes Nucl_aires de Saclay, France
6 Space Science Department of the European Space Agency, ESTEC,
Noordwijk, The Netherlands
a Sterrewacht Leiden, Huygens Laboratorium, Leiden, The Netherlands
b Max-Planck-Institut f_r Radioastronomie, Bonn, Germany.
c Department of Space Research, University of Birmingham, Birmingham,
England
I. Introduction. Cyg X-3 is a very peculiar source, studied over the
entire electromagnetic spectrum. Considering here the high-energy end of
its spectrum the source has been found to be modulated with its
characteristic 4.8 h period in the hard X-ray band up to "200 keY (e.g.
13), and in the very-high-energy gamma-ray range (_I011 to 1014 eV;
e.g. review 6), and the ultra-high-energies (above 1014 eV; e.g. 8,14).
However, the experimental status regarding the detection of high-energy
( _ 5x107-5x109eV) gamma rays from Cyg X-3, modulated with its
characteristic 4.8 h period, is confusing. The first claim of a
detection of periodic emission at high-energy gamma rays from Cyg X-3
was based on only 15 excess counts (E > 40 MeV) over an expected
background of 47 counts collected during two balloon flights 3. This
result was confirmed by the SAS-2 team 5 for energies above 35 MeV.
However, analysis of successive COS-B observations of the Cyg-X region
(E >50 MeV) did not reveal the sourcel,4, 15, while the X-ray detector
aboard COS-B detected Cyg X-3 to be in a high state of activity during
some of the observation periods 17. In this paper we summarize the
results obtained from a more sensitive analysis of the complete COS-B
data on Cyg X-3.
2. Analysis and Results. COS-B had Cyg X-3 within its field of view
during 7 observation periods between 1975 and 1982 for in total "300
days. In the skymaps (70 MeV<E < 5000 MeV) of the Cyg-X region produced
for each of these observations and in the summed map, a broad complex
structure is visible in the region 72 ° _i _ 85 ° , Ibl _ 5 ° (see e.g.
Mayer-Hasselwander et al.9). No resolved source structure is visible at
the position of Cyg X-3, but a weak signal from Cyg X-3 could be hidden,
in the structured gamma-ray background. Therefore, the data has been
searched for a 4.8 h timing signature, as well as for a source signal in
the sky map in addition to the diffuse background structure as estimated
from tracers of atomic and molecular gas.
a) Timing analysis. The arrival times of gamma-ray photons (70 MeV< E <
5000 MeV) originating from a small region around the position of Cyg X-3
95 OG .2-2 
CYG -3: OT SEEN IN IGH-ENERGY GA MA YS Y COS-B 
. Hermsen 1 , .Bennett6, G.F.Bignami 2, J.B.G.M.Bloemen 1a , R. Buccheri 3, 
p.A.Caraveo2, .A.Mayer-Hasselwander4 , .E. zelb , .M.T.pollock5c , 
.W.Strong4 
he aravane olaboration for t e OS-B atellite: 
1 Laboratory for Space Research Leiden, Leiden, The etherlands 
 Is~~ uto i isica osmica el NR, ilano, Italy 
 Istituto i isica osmica e I formatica el NR, alermo, Italy 
 ax lanck Institut fUr hysik nd strophysik, nstitut fur 
xtraterrestrische hysik, arching-bei-MUnchen, ermany 
5 Service d' strophysique, Centre d'Etudes ucleaires de Saclay, France 
6 Space Science Department of the European Space Agency, ESTEC, 
oordwijk, The etherlands 
a terrewacht eiden, uygens aboratorium, eiden, The etherlands 
 ax-Planck-Institut ur adioastronomie, o n, ermany. 
c Department of Space Research, University of Birmingham, Birmingham, 
England 
1. Introduction. Cyg X-3 is a very peculiar source, studied over the 
entire electromagnetic spectrum. onsidering here the high-energy end of 
its spectrum the source has been found to be modulated with its 
characteristic 4.8 h period in the hard -ray band up to -200 keV (e.g. 
13), and in the very-high-energy gamma-ray range ('\.010 11 to 10 14 eV1 
e.g. review 6), and the ultra-high-energies (above 1014 eV1 e.g. 8,14). 
owever, the experimental status regarding the detection of high-energy 
( '\.0 5x1 0 7-5x1 0gev ) gamma rays from Cyg X-3, modulated with its 
characteristic 4.8 h period, is confusing. The first clai  of a 
detection of periodic e ission at high-energy ga ma rays fro  yg -3 
was based on only 15 excess counts (E > 40 MeV) over an expected 
background of 47 counts collected during two balloon flights 3• This 
result was confirmed by the SAS-2 tea 5 for energies above 35 eV. 
owever, a alysis f s ccessive S-B bservations f t e yg-X region 
(E >50 eV) did not reveal the source 1,4,1 , hile the -ray detector 
aboard C S-B detected Cyg -3 to be in a high state of activity during 
so e of the observation periods 17 • In t is paper e su marize the 
r sults btained fro  a ore s nsitive alysis f t e c plete S-B 
data on Cyg X-3. 
2. Ana1ysis and Results. COS-B had Cyg X-3 ithin its field of view 
during 7 observation periods between 1975 and 1982 for in total -300 
days. In the skymaps (70 MeV<E < 5000 MeV) of the Cyg-X region produced 
f r ch f t se servations a d i  t  s med ap, a r ad c plex 
structure is visible in the region 72 0 ~ 1 ~ 850 , I b I It 50 (see e. g. 
ayer-Hasselwander et al. 9 ). No resolved source structure is visible at 
the position of Cyg -3, but a eak Signal fro  Cyg -3 could be hidde" 
i  t e str ctured ga ma-ray ackground. herefore, t  ta as een 
searched for a 4.8 h ti ing signature, as ell as for a source signal in 
the sky ap in addition to the diffuse background structure as esti ated 
fr  tr cers f t ic  olecular s. 
a) Timing analysis. The arrival ti es of gamma-ray photons (70 MeV < E < 
5000 eV) originating fro  a s all region around the position of Cyg -3 
https://ntrs.nasa.gov/search.jsp?R=19850025616 2020-03-20T17:54:48+00:00Z
96 OG 2.2-2
200 _ , Figure 1: Phase histogram of the
70MeV<E<5GeV 1 arrival time, folded modulo _ 4.8 h
o I period, of gm_aa rays with energy 70
15o _ MeV < E < 5000 MeV originating from a0
E 8mall region centered on Cyg X-3.
E
too Data from ? COS-B observations are
used. The average level i8 indi-
cated.
50
.Q
Eo Xv2:0.50
Z
0 L
0 05 10
Phase
have been folded using an ephemeris derived from the COS-B X-ray data by
Van der Klis and Bonnet-Bidaud 17. The gamma-ray photons are selected
using the background-sensitive selection algorithm proposed by Ozel and
Mayer_Hasselwander I I. This algorithm optimizes the signal-to-noise ratio
taking into account the COS-B instrumental point-spread function and the
structure measured in the surrounding sky region, both as a function of
energy. In order to verify that the background levels in the phase
histograms (20 bins) are flat for each observation, also background
samples have been folded with the 4.8 h period. For each observation
period the phase histograms for the background samples and the 'source'
samples were statistically consistent with flat distributions (see Table
I). Therefore, only upper limits on the modulated emission could be
determined. For these flat distributions these upper limits are
primarily a function of the expected duty cycle. We have calculated
upper limits for three cases: the phase interval 0.05-0.85 (I) over
which the X-ray emission has been detected, and the phase intervals
0.20-0.30 (II) and 0.50-0.70 (III), in which detections of a signal from
Cyg X-3 has been reported at very-high-energy and ultra-high-energy
gamma rays • Table I gives the 2 0 upper limits for the single
observations and for the combined data. Figure I shows the corresponding
combined light curve. The upper limits are for the X-ray phases (I) one
order of magnitude below a power-law interpolation between the
very-high-energy data points and the X-ray results, and for the
ultra-high-energy phases two orders of magnitude below this
interpolation (e.g. 14).
Table I: Reduced ×2 values for 20-bin phase histograms for back-
ground (bg) and 'source' (8) sample8 and 2_ upper limit8
(ph cm-$ 8-J) to the modulated (4.8 h) flux (70-5000 MeV) from Cyg
X-_ for the three phase interval8 given in the tezt.
Obs • Epoch X 2 X 2 I I I I II
number of measurement bg s (10 -6 ) (10 -7 ) ( 10 -7 )
4 75/11/28-75/12/24 0.69 0.80 1.8 3.0 2.8
22 77/06/08-77/07/15 1.05 1.87 2.2 4.3 4.6
36 78/11/03-78/12/11 0.76 0.31 1.6 3.9 3.8
51 80/05/14-80/06/24 1.21 0.73 2.7 4.6 2.4
55 80/10/17-80/11/04 I. 11 0.75 3.1 0.9 5.0
60 81/06/03-81/07/24 0.79 1.22 2.7 1.9 2.2
63 81/11/03-82/02/18 0.64 0.50 1.0 2.5 0.4
Total I .0 I .0 I •1
Ul 
:>. 
C 
0:: 
c 
E 
 
c 
<.!) 
'0 
... 
ClI 
Ll 
E 
::J 
 
200 
150 
100 
 
 
eV (E ( 5 GeV 
x~ =0.50 
96  .2-2 
Figu'l'e 1: phase histog'l'a  f the 
'l"l'i l. tim " f l  odul  'V .   
pe'l'iod" of gamma 'l'ays with ene'l'gy 70 
e  <  <  e  'l'iginating f'l'o   
s aU 'l'egi  ae te'l'ed  yg -;5. 
Data f'l'om 7 COS-B obse'l'vations we 
se . e ve'l' ge l l is i i-
a t  • 
  
 
 
ave een lded sing  phemeris erived  e OS-B -ray ata  
an er lis a d onnet-Bi aud17 • he ga ma-ray hotons re s lected 
sing t e ackground-sensitive lection l orithm roposed y zel d 
ayer-Hasselwander11 • his al orithm ptimizes t e si nal-to-noise r tio 
t king i to ccount t e OS-B i strumental oint-spread f nction d t e 
structure easured i  t e s rrounding s y r gion, oth as a f nction f 
nergy.  rder  erify at t e ackground els  t e hase 
istograms 0 ins) re lat r ch bservation, lso ackground 
sa ples have been f lded ith t e .8 h eriod. or each bservation 
eriod t e hase istograms r t e ackground ples d t e ' urce' 
sa ples ere statistically consistent ith flat distributions (see able 
1). herefore, nly pper li its on t e odulated e ission c uld be 
etermined. or t ese t istributions t ese pper li its re 
rimarily a f nction f t e e pected uty ycle. e ave alculated 
per its r t r e ses: t e hase i terval .05-0.85  ver 
hich t e -ray ission as en etected, d t e hase i tervals 
. 0-0.30 I) d .50-0.70 I),  hich etections f  i nal  
yg -3 as en r ported t ery-high-energy a d ltra-high-energy 
a ma r ys. able 1 ives t e  0 per li its f r t e i gle 
bservations d r e bined ata. igure 1 ows e respo ding 
mbined li ht rve. he per li its re r t e -ray hases  e 
rder f agnitude elow a ower-law i terpolation et een t e 
ery-high-energy ata oints d t e -ray sults, d r t e 
ultra-high-energy phases t o orders of agnitude below t is 
i terpolation ( .g. 4). 
Obs. 
Tabl.e 1: Reduaed X 2 values fo'l' 20-bin phase histog'l'a s fo'l' baak-
g'l'ound (bg) and 'sou'l'ae' (s) samples and 20 upper> Zimits 
(ph o -2 s-l) to the odulated (4.8 h) jiux (70-5000 eV) f'l'o  yg 
-3 f 'l' t  t 'l'ee ase inte'l'Vals i  i  t  t xt. 
Epoch 2 I II III 
mber f easur ment  bg x  s (1 -6 ) (10-7 ) (10-7 ) 
 5/ 1/28-75/12/24 . 9 . 0 .  .  .8 
 7/06/08-77/07/15 . 5 . 7 .  .  .6 
 8/ 1/03-78/ 2/11 . 6 . 1 .  .9 .8 
 0/05/14-80/06/24 . 1 . 3 .  .6 .4 
 0/10/17-80/11/04 1. 11 . 5 . 1 0.9 5.0 
0 1/06/03-81/07/24 . 9 . 2 .  .  .  
3 1/ 1/03-82/02/18 . 4 . 0 .  .5 .4 
otal 1  1  1   
Figme 2: Gamma-ray 
in tensi ty  ( E  >SO0 MeV) 
distributions i n  the  
Cyg-X region. Contour 
ZeveZs: 4,6,. . ,12,14x 
10-5 photon cm-2 s-1 
sr-1, f i r s t  s tep i n  
g r q  scale a t  2x10'~ 
photon . cm-2 8-7 sr-1. 
a)  Measured by COS-B. 
b )  Estimated from the 
totaZ gas distribution 
using HI and CO data. 
m: Position o f  garruna- 
a sources12 not 
esplained by the gas. 
x: Cyg X-3 position. 
b) Spatial Analysis. The COS-B team has shown that the structured 
emission in the Cyg-X region can be explained as being the sum of (i) 
diffuse emission from the interaction between relativistic cosmic rays 
and the total-gas distribution and (ii) two pointlike sources which 
cannot be explained by the gas distribution12 ( see Figures 2 and 3c) . 
Figure 2a shows a contour plot of the gamma-ray intensities in the Cyg-X 
region for energies above 500 MeV (the highest COS-B energies with the 
best angular resolution). 
A combination of HI measurements with the recent Columbia Large- 
scale CO survey (ref's in 2,12) allows a detailed estimate of the 
diffuse emission above which any sources appear (see Figure 2b). Using 
+ Bloemen et al's2 model of the diffuse emission we have used a likelihood 
methodl2 to test the presence of a point source at the position of Cyg 
90° 80° 70° 60° 
Longitude 
Figure 3: a)  Normalized COS-B 
( t h i ck )  and SAS-2 ( t h in )  
histograms (E > 100 MeV; 
isotropic background ZeveZs 
are subtracted, for SAS-2 
from 7 ,  16) .  Thick curve: sum 
o f  the expected d i f f u se  
gamma-rau emission and that  
from two sourcesl2. Thin 
curve: d i f f u se  emission on2 g. 
b )  ContourpZot o f  soupce 
in tens i t i e s  contributing t o  
F i g .  3a. x:Cgg X-3 position. 
97 
70· 
OG 2.2-2 
Pigur> y 
500 
  
g-X 
le l ~6~ .  ~12~14~ 
-5 t  a r2 -l 
1~  
rey a ~ -5
t ._ a r2 s 1 r-1. 
)  S-B. 
) i ted f
tal
I   •
•  p mma-
ray a 12 
~ n . 
-3 iti . 
ati  nalysis. S- eam o ru u e
is o  l n u ) 
u is rom ion c i  
-g i ribu ion i) w i t ik  hi
t l  i ribu ion  i   
i  o   t l t a-r i e   
o    e the st -  it h
st l l t ).
binat o  I eas r ent  it l bi l
  v  low   t ed im  
fu is  hi  see  ). si
l e l  odel h fu  i o   ikelihoo
et 12  i t  h OSit  
' :J; 
~(/) 7 
' 10 
u 
c 
';s 
.c 
0. 
" ' 0 
-=3 
Z' 
iii 
c 
~ 1 
..., 
@ Ibl (1.0 
it  
) Ziz  -  
t iak) -2 thin) 
E  
t ia a l
t at ~ -  
~  ia  a
 ~ a f se 
ray  
 a 12 • i  
a ffuse ly  
) ra
i  a  
y  3  
98 OG 2.2-2
X-3, in addition to the total structure due to the diffuse emission and
the two sources. The analysis was performed for the total COS-B data set
in three energy ranges, treating the intensity of each component as free
parameters. No evidence for the detection of Cyg X-3 was found; Table 2
gives 2 _ upper limits to the total flux.
3. Discussion. The COS-B upper limits are significantly lower than the
flux of (4.4±1.1)xi0 -6 photon cm -2 s-I for energies above 100 MeV
reported from SAS-2 (Lamb et al.5). Lamb et al. identified in their
analysis the total excess in the Cyg-X region with Cyg X-3, and, in
addition, they claimed the total gamma-ray flux to be modulated with the
4.8 h period. However, the CO data (see Figure 2b) indicate that a
significant fraction of the gamma rays are due to diffuse emission.
Comparing the SAS-2 distribution with that measured by COS-B, we find no
evidence for an excess in the SAS-2 case due to variable, modulated
emission from Cyg X-3. Since there appears to be a systematic difference
between the COS-B and SAS-2 absolute intensities in this region, the
SAS-2 intensities being systematically lower as was already noticed by
Mayer-Hasselwander 10, we normalized the total SAS-2 intensity measured
in the longitude interval 60°<1<95 ° to that of COS-B. This comparison is
shown in Figure 3. The shapes of the two distributions are evidently
consistent, and the absolute levels agree everywhere within the _I_
level. The conclusion which may be drawn from this comparison is, that
in the total gamma-ray excess in the Cyg-X region, measured by COS-B and
SAS-2, no contribution can be identified from Cyg X-3 at the flux lev--e-I
reported from SAS-2.
Table _: 2 _ upper limits to the total time-averaged gamma-ray flux
from Cyg X-3 using the complete COS-B data.
Energy range 2o upper limit
70-150 MeV 7.5x10 -7 photon cm -2 s -I
150-300 MeV 6.5xi0 -7 photon cm -2 s-I
300-5000 MeV 4.5x10 -7 photon cm -2 s -I
References
I. Bennett et al. (1977), Astron. Astrophys. 59 , 273
2. Bloemen et al. (1985), Astron. Astrophys. subm., and 0G3.1-6.
3. Galper et al. (1976) Soy. Astron. Letters 2 , No. 6, 206-208
4. Hermsen, W. (1983), Space Science Reviews 36 , 61-92
5. Lamb et al. (1977), Astron. J. Letters 212 , L63-66
6. Lamb, R.C. (1984), Proc. Workshop on Cosmic Ray Experiments for the
Space Station Era, Baton Rouge, October 1984
7. Lebrun, F. Paul, J.A.: 1983, Astrophys. J. 266 , 276
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11. Ozel, M.E. and Mayer-Hasselwander, H.A. (1983), Astron. Astrophys.
125, 130-135.
12. Pollock et al. (1985), Astron. Astrophys. in press, and 0G3.1-9
13. Reppin et al. (1979), Astrophys. J. 234 , 329
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16. Thompson, D.J., Fichtel, C.E.: 1982, Astron. Astrophys. 109 , 352
17. Van der Klis, M., and Bonnet-Bidaud, J.M.: 1981, Astron. Astrophys.
95 , L5-L7
 O  2. -2 
-3, i  a dition t  th  t tal str cture d e to th  diff se e ission a  
t  t  s rces. e a aly is as p rf rmed f  th  t tal S-B d ta s t 
in three energy ranges, treating the intensity of each component as free 
parameters. No evidence for the detection of Cyg X-3 was found; Table 2 
g es 0 u per li its t  t  t tal f . 
3. iscussion. The COS-B upper li its are significantly lower than the 
flux of (4.4±1.1)x10-6 photon cm- 2 s-1 for energies above 100 MeV 
orted fr  S-2 (L b  le 5 ). b e  le i ntified in eir 
analysis the total excess in the Cyg-X region with Cyg X-3, and, in 
dition, t y l i ed t  t tal ma-ray fl  t   odulated ith t  
4.8 h eriod. owever, t e CO ata (see igure 2b) i icate t at a 
i nificant fr ction f t  a a r s r  e t  iffuse ission. 
omparing the S S-2 distribution ith t at easured by C S-B, e find no 
evidence for an excess in the SAS-2 case due to variable, odulated 
e ission fro  Cyg -3. Since there appears to be a systematic difference 
between the COS-B and SAS-2 absolute intensities in this region, the 
SAS-2 intensities being systematically lower as was already noticed by 
ayer-Hasselwander 10, we normalized the total SAS-2 intensity measured 
in the longitude interval 60°<1<95° to that of COS-B. his co parison is 
shown in Figure 3. The shapes of the two distributions are evidently 
c nsistent, and t e absolute le els agree everywhere ithin t e ~10 
level. The conclusion which may be drawn fro  this co parison is, that 
in the t tal ga ma-ray excess in the Cyg-X region, easured by C S-B and 
S S-2, no contribution can be i entified fro  yg -3 t t e fl x le el 
ported  AS-2. 
TabZe 2: 20 upper "limits to the totaZ time-averaged gamma-ray fiu:r: 
fro  yg X-3 using the aompZete C S-B data. 
nergy ge 0 per it 
70-150 eV 7.5x10-7 photon cm-2 s-1 
50-300 MeV 6.5x10-7 photon cm- 2 s-1 
0-5 00 eV 4.5x10-7 photon cm-2 s-1 
ef rences 
1. ennett et ale (1977), stron. strophys. 9, 273 
. loemen t le ( 985), stron. strophys. s bm., and OG3.1-6. 
3. alper et ale (1976) Sov. stron. etters , o.6, 206-208 
. ermsen, . ( 983), pace cience eviews 6, 61-92 
. amb t le ( 9 7), stron. . etters 12, 63-66 
6. Lamb, .C. (1984), Proc. orkshop on osmic Ray xperiments for the 
pace tation ra, aton ouge, ctober 1984 
. ebrun, . aul, J. .: 983, strophys. . 6, 276 
. loyd-Evans t le (1983), ature 05, 784-787 
. ayer-Hasselwander t ale (1982), stron. strophys. 05, 164-175 
0. ayer-Hasselwander, H.A. (1983), pace cience eviews 36 223-247 
11. Ozel, M.E. and Mayer-Hasselwander, H.A. (1983), Astron. Astrophys. 
125, 130-135. 
12. Pollock et ale (1985), stron. strophys. in ress, and OG3.1-9 
13. Reppin et ale (1979), strophys. J. 34  329 
14. Samorski, ., and Sta m, .: 1983, strophys. J. 268, L17-L21 
15. Swanenburg et ale (1981), Astrophys. J. etters 43, L69-L73 
16. Thompson, .J., Fichtel, C.E.: 1982, stron. strophys. 109, 352 
17. Van der Klis, M., and Bonnet-Bidaud, J. .: 1981, Astron. Astrophys. 
95 , L5-L7 


Cyg X-3:  Not seen in high-energy gamma rays by COS-B

Cyg X-3: Not seen in high-energy gamma rays by COS-B

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