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OCR for page 368
X-Ray Radiation from Supernova 1987A
The Results of the Kvant Module in 1987-1989
R.A. SUNYAEV, A.S. KANIOVSKY, V.V. EFREMOV, S.A. GREBENEV,
A.V. KUZNETSOV, E. CHURASOV, M. GILFANOV, N. YAMBURENKO1,
J. ENGEHAUSER, S. DOEBEREINER, W. PIETSCH, C. REPPIN,
J. TRUEMPER,2 E. KENDZIORRA, M. MAISACK, B. MONY, R. STAUBERT,3
G.K. SKINNER, T.G. PATTERSON, A.P. WILLMORE, O. AL EMAM,4
A.C. BRINKMAN, J. HETSE, J.J.M IN'T ZAND, R. JAGER5
ABSTRACT
The results of two years SN1987A hard X-ray radiation observations
by the HEXE instrument aboard the Kvant module are summarized. By
May-June 1989, the hard X-ray flux had declined more than 8.5 tunes in
comparison with the maximum of the X-ray light curve. The upper limit
on the ratio of 57Co/56Co abundances at the level of ratio of 57Fe/56Fe
abundances at the Earth by a factor of 1.5.
INI8oDucrIoN
The Roentgen international X-ray observatory on the Kvant module
of the Mir space station has been operating successfully since the beginning
of June 1987. Four telescopes mounted onboard the Kvant module cover a
wide energy range: Coded Mask Imaging Spectrometer 1TM (2-30 keV),
GSPC (2-100 keV); Phoswich type detectors HEXE (2~200 keV), and
Phoswich type detectors Pulsar X-1 (50-1300 keV).
Many of the X-ray sources were observed in 1987-1989, and appron-
mate~ 30% of the observations were devoted to SN1987N
1 Space Research Institute, Academy of Sciences, Moscow
2Max-Planck-Institut fiir Extraterrestrische Physik Garching, FOG
3Astronomisches Institut der Univemitat ldbingen, FOG
4 Space Research Laboratory, Utrecht, The Netherlands
a Department of Space Research, University of Birmingham, UK
368
OCR for page 369
HIGH-ENERGY ASTROPHYSICS
369
For the first time during two years of observing Supernova 1987A
in June 1989, the Roentgen observatory aboard the Mir-Kvant module
was not able to detect its hard X-ray radiation dunog the current series of
observations. The radiation flux in energy band 45-105 keV decreased more
than 8.5 times in comparison with the mammal flux detected in January
1988.
The results obtained during the two years of Supernova 1987A obser-
vations were given in papers (Sunyaev et al. 1987a,b, 1988, 1989~. By the
present time we have succeeded in calibrating the third and fourth detec-
tors of the HEXE device using the results of the Crab Nebula observation.
These detectors have a lower energr resolution in comparison with the
first and the second ones. Therefore, we reprocessed all the obtained data
about SN1987A hard X-rays using the results of all four detectors of the
HEXE device, which increased data significance and decreased statistical
errors.
In Figure la,b, the spectra of SN1987A hard X-ray radiation are pre-
sented. They were obtained in a series of seven intense observations earned
out from the Roentgen observatory over two years. The spectra demon-
strate an increase of the flux from August 1987 to January 1988. This
increase is connected with a rapid decreasing of the envelope transparence.
From January 1988 to June 1989 a continuous decline of the flux is ob-
served which is mainly connected with a decreasing amount of 56CD in the
envelope. Already in September 1988 a strong change of the spectral shape
was detected. Ins is explained by a decreasing of the envelope optical
thickness with respect to Thomson scattenng. The number of successive
scattenngs experienced by the majority of photons became insufflcent to
decrease the energy of the 56Co decay gamma-photons due to a multiple
recoil effect up to a value of hv < 50 keV.
Note that the sharp flux cutoff at the energies below 20 keV in August
1987 and January 1988 was connected with photoabsorption by heavy
elements. At that time the photon diffusion in the envelope, accompanied
by the recoil effect, moved the majority of photons in the band hv < 20
keV where the photoabsorption dominated.
In Figure 2 and 3, the light curves of the SN1987A emission in three
energy bands: 15~5, 45-105, 105-2130 keV (see also liable 1) are presented.
Note here especially the pO=t corresponding to observations on June 16,
1987, when the hard X-ray 6= in the 45-105 keV spectral channel was
detected at four standard deviation levels (it was first noticed by Englhauser
et al. 1989~.
The light curies (Figure 3) testified to a hard X-ray flux from the
supernova, changed smoothly in accordance with predictions of the model
of this radiation appearance due to radioactive cobalt decay in opaque
envelope. For two years of observations we have not been able to observe
OCR for page 370
370
2'
AMERICAN AND SOVIET PElkSPECTIVES
tes days(~)
9 - 320 days(33
o
- 4
~0
_5
~0
LL
~. also days (2)4
.~
20
. . . . ~. . . .
lO ~So 2 20 3 40
ENERGY (ke V)
O HEXE
~ Pulsar X-!
o TTM
2 3
JO 40
o
an>
Q , . . . ~4
~- 645 ~Y9~60
MU
~ o ~
1 ~. ,
At;
~0
50-4
:~?'r.~
1. ,& 1 · ~ s .
to S to 2 do ~
ENERGY (ke v)
~ ~1
2
~0
ENERGY flue V)
1 -a
own ~
FIGURE 1 The SN1987A X-ray spectra obtained by the Roentgen observatory in August
1987 (1) and October - November 1987 (2), December 1987 - January 1988 (3), April 1988
(4), September - October 1988 (5) and November 1988 (6), May - June 1989 (7), (diamonds
and crosses - the HEXE and Pulsar X-1 data respectively, ausses marked By circles - the
TIM telescope upper limits). The errors correspond to one standard deviation, the upper
limits - to three standard deviations (in the last graph the HEXE upper limits are shown
by tnangles). Results of the Monte-Carlo calculations carried out according to the envelope
model accepted in the present paper are presented by solid lines (time after the outburst
is shown near each cunre). In graphs 5,6,7 a 56 Co portion in the total 57Co emission is
shown tar dotted lines. Ihe relative abundance of 56Co/57Co is equal to two-abundance of
56Fe/57Fe at the Earth.
OCR for page 371
HIGH-ENERGY ASTROPHYSICS
1 987
371
1 988
15 -105 keV
co
cot
oh
o
s
Q
U.
so
-
X
-
-
J
11
!1
1;1
111
' 1
o , ,
~1 1 ~I\_'
200 300 400 500 600 800
DAY AFTER TH E EXPLOSION
FIGURE 2 The SN1987A X-ray 15-105 keV flux as a function of time according to
the HEXE observations Each point corresponds to one observational day, the errors
correspond to one standard donation. Three sigma upper limit on the flux observed in
May-June 1989 is presented.
the traces of a shock wave generated due to collision between the expanding
envelope of the supernova and a stellar wind emitted by the presupernova
on a red giant stage of the evolution. We were also unable to obsene traces
of X-ray radiation of the stellar remnant - a young pulsar or an accreting
object or any manifestations of emission connected with cosmic rays.
MIXING OF RADIOACTIVE ELEMENTS
IN TlIE EXPANDING ENVELOPE
Early detection of the SN1987A hard X-ray radiation by the Ginga
satellite and the Avant module (Dotani et al. 1987; Sunyaev et al. 1987a,b)
was the first evidence of a radioactive 56Co strong mixing over the envelope
volume (Itoh e! al. 1987; EbisuzaJ~ and Shibazaki 1988; Grebenev and
Sunyaev 1988; Pinto and Woosley 1988~. At present this conclusion is
confirmed by direct observations of a velocity dispersion of infrared lines
of the iron and cobalt ions (Ericson et al. 1988) and also by a broad
OCR for page 372
372 AMERICAN AND SOVIET PERSPECTIVES
1987 1 988
15 - 45 keV
-
o
Q
10
0
-
X
O
4
o
I I 1 1 1 /\
in 45 - 105 keV
1~
it,
TO
I I I ~
105 - 200 keV
L~1
1
\
\
1
~ T
200 300 400 500 600 800
DAY AFTER THE EXPLOSION
FIGURE 3 The SN1987A X-ray fluxes as functions of time according to the HEM data
in three colors 15-45, 45-105, and 105-200 keV. Each point presents data averaged over long
period of observations The errors correspond to one standard deviation. The results of
Monte-Carlo simulations carried out for the envelope model accepted in the present paper
are shown by solid lines.
OCR for page 373
HIGH-ENERGY ASTROPHYSICS
373
TABLE 1 The SN1987A X-ray flux evolution in accordance with data of
the HEXE device observations in 1987-1989
Day since Fluxes and 1~ errors tI0~6phot~cm~2s~:keV~~]
the outburst in :he energy bands
15 - 45 keV 45 - 105 keV
143.9 - 144.1 2. 34. 51. 12.
169. - 182. 68.2 5.7 46.7 2.1
186. - 204. 96.7 8.5 50.9 3.5
231. - 247. 83.1 8.3 57.4 3.3
258. - 266. 85. 10. 55.2 4.4
291. - 309 97. 11. 66.1 5.6
328. - 343. 100. 10. 62.6 3.5
413. - 426. 63. 9.5 51.1 3.8
444. - 446. 46. 27. 24. 12.
559. - 569. 17.2 9.6 20.5 4.1
590. - 599. 21.4 6.1 14.5 3.0
630. - 648. 12.2 4.1 10.6 2.6
820. - 840. 8.2 7.0 3.8 2.9
105 - 200 keV
18.
21.3
26.0
24.3
12.8
30.4
25.1
27.9
24.0
7.2
8.2
14.5
-2.8
17.
3.3
5.2
7.2
9.7
8.9
4.8
6.1
16.
6.5
4.7
7.0
4.2
spectral width of the 56Co direct escape gamma-lines (Matz e! al. 1988;
Rester et al. 1989~. These direct observations testier to the presence of
radioactive cobalt in the envelope layers having expansion velocities from
4~0 up to 3000 km/s. This would be impossible if the strongest mung of
envelope material due to generation of the Rayleigh-~ylor instability had
not occurred (Hachisu e! al. 1989; Arnett e! al. 1989~.
The supernova hard X-ray light curve provides an opportunity to es-
timate the distribution of radioactive cobalt over the envelope using the
simplest assumptions. The 56Co distribution (mass-fraction) consistent with
the observed light curve is shown in Figure 4 by crosses (the vertical line
of a cross corresponds to an error at one standard deviation level). The
problem of the reconstruction of cobalt distribution over the envelope is
considerably simpler if cobalt radial distribution is searched as a superpo-
sition of two Gaussians: a narrow one localized near the envelope center
and an extensive one with broader 56Co distribution over the envelope.
The regions of 56 Co distribution consistent with the observed light curve in
this simple model are also presented in Figure 4.
It is obvious that two different approaches give quite close results.
About 60~o of cobalt is in the central region of the envelope having low
OCR for page 374
374
o
CD
11
o
10°
10-1
o 10-2
C:
a:
G
On
On
C
10-3
10-4
AMERICAN AND SOVIET PERSPECTIVES
_
_~
o
MASS, M
10
FIGURE 4 Region of the most probable s6 Co distribution (mass-fraction) over the
SNl987A envelope which gates a possibility to simulate the observed X-ray light curves of
the source. The results of two independent approaches are presented. In the first approach
it is assumed that cobalt is uniformh~r distributed over five spherical layers of the envelope
(crosses, errors of the cobalt concentration in each layer are given at one sigma level).
In the second approach the 67% confidence level region of the distribution described by
superposition of two Gaussians is obtained. It is clear that both approaches give similar
results.
velocities. And about 40% is mixed over all the envelope volume. Note
that the data of only mro hard energy bands 45-200 keV were used dunog
the cobalt distribution reconstruction. The flux at lower energies strongly
depends on photoabsorption in the envelope, but the photoabsorption
efficiency strongly depends on the degree of the cobalt nii~ng.
All the calculations, the results of which were presented above and
will be discussed below, were earned out on the basis of the velocit r
OCR for page 375
HIGH-ENERGY ASTROPHYSICS
375
and density distribution model resulted from hydrodynamics simulations by
Arnett (1988~.
In Figure 3 it Is shown how the accepted model of cobalt distribution
coincides with the observed X-ray light curve. Deviations are maximal
at the beginning of the supernova X-ray observation in a soft 1545 keV
band. This points out a more strong photoabsorption in comparison with
photoabsorption ~ the used model. It may be connected with the enhanced
cobalt concentration in outer envelope layers. High X-ray and gamma-
ray radiation from these layers appeared at early stages of the envelope
expansion before the beginning of the Roentgen observatory systematical
observations.
ABUNDANCE OF 57Co
By the beginning of the second year after the explosion a 57Co isotope
can become an important energy source in the supernova envelope since
it decays 3.5 times more slowly than 56Co. The simulations of explosive
nucleosynthesis (Woosley et al. 1986; Hashi~noto et al. 1989) predicted
a ratio of 57Fe/56Fe abundances in the Earth. There are two ways to
define the abundance of 57Co in the SN1987A envelope: the first, by
direct determination of flux in the 57Co lines of 122 and 135 keV in the
supernova spectrum and the second one, by the determination of a 57Co
photon portion in the X-ray continuous spectrum in the 45-105 keV energy
band. We mean the photons emitted in the 57Co lines 122 and 136 keV, but
which undergo to multiple scattering in the envelope and decrease their
energy due to the recoil effect. Because of relatively low energy resolution
of Phosw~ch detectors, the HEXE device aboard the Mir-Kvant module
gave considerably better results when the second method was used.
The results presented below depend on an accepted envelope model
(the Arnett model [1988] is used) and on a cobalt distn~ution over the
envelope (the distribution presented in Figure 4 is used). It is also supposed
that 57Co is distributed s~Darly to 56Co.
For the whole period from September 1988 to June 1989 the Roentgen
observatory has not detected a statistically significant enhancement of X-ray
luminosity in the 45-105 keV energy band over the model predictions in
which the whole observed flux is connected with the 56Co decay. The upper
limits at three standard deviation levels for the ratio of 57 Co/56 Co relative
abundance in the supernova envelope to the Earth's 57Fe/s6Fe relative
abundance were equal to Z4 in September 1988, 3.3 in December 1988,
and 1.8 in June 1989 at the accepted assumptions. Note that the ratio of
57Fe/56Fe abundances at the Earth is 0.024 (Cameron 1986~. All the data
obtained from September 1988 to June 1989 allowed us to obtain a limit at
three standard deviation levels for a portion of 57Co decay photons in the
OCR for page 376
376
AMERICAN AND SOVIET PERSPECTIVES
light curve of the SN1987A hard X-ray radiation. This limit corresponds
to the 57Co/56Co abundance in 1.5 times exceeding the Earth's 57Fe/56Fe
relative abundance. The observations in May-June 1989 gave the upper
limit on the cobalt 122 keV line hm 3.9~10-4 photons cm~2s~: at 3
level). This limit corresponds in frames of the model being discussed to
the 57Cop6Co abundance six times exceeding the Earth's abundance of
s7Fe/~6Fe.
The data obtained in May-June 1989 also provides a possibility to set
up an upper limit on a fraction of the 22Na and 44Ti radioactive photons in
the X-ray 45-105 keV flux from SN1987A in 830 days after the explosion.
The corresponding upper limits at three standard deviation levels on mass
of 22Na and 44Ti contained in the envelope at the moment of explosion
are 1.3 10-3M~ and 9 10-3M~. These limits exceed the amount of
44Ti, M44 ~ 1.2 10-4M, and 22Na, M22 ~ 3 10-5M<3, predicted by
Hashunoto e! al. (1989) and Woosley et al. (1986) on the basis of the
explosive nucleosynthesis calculations at one order of magnitude.
LIMITS ON THE STELLAR REMNANT LUMINOSITY
The observations of the Roentgen observatory in May-June 1989 set
up strong restrictions on X-ray luminosity of a stellar remnant produced
during the explosion L~(1-6 keV) < 3.6 1036, Lo (6-15 keV) < 5.4 1036
and L=(15-105 keV) < 1.35 · 1037 erg/s for the assumed distance 55 kpc
(Sunyaev et al. 1990, Able 1). At that time a Thomson optical depth of
the envelope yet exceeded 3-4, and an X-ray spectrum of the remnant was
considerably distorted by photoabsorption and compton scattering. The
absorbed energy went on the envelope heating and was reemitted in the
infrared, subnlillimeter, and optical bands. The measurements by Bouchet
et al. (~1990) showed that emission of dust in the envelope had a black
body spectrum with T ~ 160K, and the supernova bolometnc luminosity
in 1030 days after the explosion was equal to (2.~0.1) 1038 erg/e. Using
data from Monte Carlo calculations, the upper limit on the hard X-ray flux
in the 15-105 keV band obtained by the HEXE device on the 83Oth day
and the information on the envelope emission at low frequencies indicate
that rather interesting restnchons on an intrinsic spectrum of the stellar
remnant may be obtained. For example, assuming that the remnant (pulsars
has a power law spectrum in 1-1000 keV energy band, Ion z'~= [photons
· cm~2s~ikeV~~], and using the 3cr upper limit presented above for the
X-ray 15-105 keV flux escaping the envelope on the 830th day, we obtain
the Or upper limit on the pulsar luminosity in the 1-1000 keV energy band
JIB < 2.4 · 1~ and < 4.4 · 1~8 ergs for No spectral indexes ~ = 1.5
and 2.1. In neglecting the pulsar spindown and its luminosity changing we
may find the upper limit on the energy absorbed in the envelope, that is,
OCR for page 377
HIGH-ENERGY ASTROPHYSICS
377
its low frequency luminosity on the 1100th day LIR < 1.0 1038 and 3.5
· 1038 erg/s for c' + 1.5 and 2.1 correspondingly. It is clear that in the
case when the spectral index is 1.5, such a spectrum is not able to give the
observed low frequency luminosity of the envelope. It may be easily shown
that any spectrum with cat < 1.75 does not coincide with the data obtained
by Bouchet et al. (19901.
The presented example shows a possibility for using our data to obtain
restrictions on parameters of a pulsar hidden inside the expanding envelope.
In the case when an accreting object is situated in the envelope center our
estimates are less definite. Nevertheless, such an analysis, using the HEXE
data presented above, for the object with a spectrum similar lo the spectrum
of the well-known source Cygnus X-1 in a low state (Sunyaev and Thumper
1979), also demonstrates the impossibility of satisfying the low frequency
data. If the infrared radiation is the result of dust, the reprocessing of a
central object with hard emission from the X-ray spectrum of the stellar
remnant should be soft enough
Another way to explain the excess of infrared radiation detected by
Bouchet et al. (19903 is that radioactive isotopes 57Co, 22Na and 44Ti are
more abundant in the envelope than it was assumed. Their hard radioactive
emission transforms in the opaque envelope into the low frequency emission
which was observed. As the excess luminosity on the 1100th day after the
explosion was equal to 2 · 1038 erg/s it was necessary that about 4 10-2M:,
of 57CO (that is the 57Col56Co ratio exceeded the Earth's 57Fep6Fe ratio
about 22 dines), or 9 · 10-4M~ of 22Na, or 9 10-3M of 44Ti were
hidden inside the envelope. Comparing these values with the HEXE upper
limits for 57Co, 22Na, and 44Ti abundances, M57 < 2.8 10-3M~ and M44
< 9 10-3M~, M22 < 1.3 10-3 Me, we come to the conclusion that the
assumption about the radioactive nature of excess has failed in the case of
57Co and is unlikely ~ the case of 44Ti and 22Na.
TTM/COMIS UPPER LIMITS ON THE FLUX FROM SN1987A
The 11M/COMIS instrument on board the Kvant module is a coded
mask-imaging spectrometer, sensitive in 2-30 keV energy, and with 7 .5 x
7°.5 FWHM field of view. We present below some results of the anah,rsis
of LMC field observations in November l9~June 1989.
Dunng Ohs period about 130 sessions of LMC observations were per-
formed. After the rejection of telemetric drop-outs and sessions with poorly
defined pointing, the topical exposure time for the observations analyzed here
was ~ 75,400 s.
A slice of AM image (7°.8 by 3°.4) in three energy bands is presented
on Figure 5. This unage was obtained by combining all the data of the
period November 1988-June 1989. The sources LMC X-1, LMC X-2, LMC
OCR for page 378
378
LMC X-1
LklC X-2
Ic ,N1987A
_ .
80
LMC X-2
AMERICAN AND SOVIET PERSPECTIVES
PSR 540-693
LMC X-4 LMC X-3
160-----a- -30
-
~i
1n
frM/COMIS LMC 6-15 keV
| SN1987A LMC X-4
_
PSR 540-693
ADO
40
80
140 -
1^
FIGURE 5 The 7°.8 By 3°.4 slices of LMC images in three dilierent energy bands (2-6,
6-15, and 15-Z7 keV) obtained By 1=I instrument during the observations of November
1988 - June 1989. The labels mark signifi~tl~r detected LMC sources as well as the
position of SN1987A. Coordinates shown correspond to ITM field of view. One pixel of
1TM image has size of 1.86 arcmin.
OCR for page 379
HIGH-ENERGY ASTROPHYSICS
LMC X-2 LMC X-11
379
l1M/COMIS LMC 15-27 keV
SN1 987A
PSR 540-693
-40
LMC X-4
t60~ -30
-70
LMC X-3
10
X-3, LMC X4, and 50-millisecond pulsar PSRO54~693 are significantly
detected. These sources are marked on Figure 5 by arrows as well as the
position of SN1987N
The AM observations of SN1987A in June-August l9g7 did not reveal
any significant flux from the supernova in 2-30 keV energy band on the
level 0.5 mCrab (3~) (Sunyaev e! al. 1987 a,b, 1988) when HEM and
Pulsar X-1 devices onboard Kvant detected strong hard X-ray radiation
from the supernova. The further TIM obsenations of SN1987A were
stimulated by the exciting Ginga discovery of the variable continuum of
this source in 130 keV band (Dotani ~ al. 1987; Masai et al. 1987; Masai
et al. 1988~. During observations in November 1988 to June 1989 we again
did not detect any significant flux from supernova in any part of 2-30 keV
energy band (the efficiency of the TrM detector is highest at ~ 8 keV,
and diminishes towards higher and lower energies). The upper limit in the
whole 2-27 keV energy band is equal to 0.6 mCrab for Crab-like spectrum.
The upper limits obtained in three energy subbands are presented in Able
2.
In each particular session of observations (~ 1000 sec duration) we
obtained an upper limit for the flux in the 2-27 keV band on the level
of 5 mCrab. For each week's set of intense observations in November,
December, or June, our 3a upper limit in the 2-27 keV band is on the
level of 1.2 mCrab. This upper limit is twice lower than the January 1988
OCR for page 380
OCR for page 382
OCR for page 383
OCR for page 384
Representative terms from entire chapter:
light curve
380
AMERICAN AND SOVIET PERSPECTIVES
TABLE 2 Upper limits (3 cr) of the flux from SN1987A obtained by TI M
instrument dunog the observations in November, 1988 - June, 1989
Energy (key) mCrabtl ~ ph/3ec/cm2/kev ~ 2 ergs/e
2 - 6 0.S 4~10~ 4 ~ . O ~ )0- ~ ~
6 - 15 0.9 lal0~4 1.5~10-~t
15 - 27 4.2 ~ ~o~4 4.0 30-~}
) for Crab-like spectrum
2 ) for flat photons spectrum
outburst detected by Ginga in the same spectral band (Masai et al. 1988~.
Unfortunately, the AM instrument did not operate when the source in
the standard X-ray band, detected by Ginga, was the most bright. The data
presented here corresponds to the time when the brightness of this source
in hard X-rays decreased. Therefore we can only mention here that during
periods of our observations, the standard X-ray band source in SN was in
a relatively quiescent state with no outbursts of the January 1988 type.
All the HEXE upper limits for the September 1988 to June 1989 time
span are below the TIM 3~ upper limits for the 16-17 keV band for any
power law extrapolation of detected HEXE nux towards lower energies
with photon spectral index ~ > - 4.5.
The change in shape of the SN1987A spectrum, according to the HEXE
data, in September 1988 undoubtedly shows that any flux at energies lower
than 40 keV has an origin unrelated to the radioactive decay of both 56Co
and 57Co. This fact makes a search for the flux from SN1987A ~ the
standard X-ray band of eno:rn~ous importance because it opens the way to
discover X-ray emissions of a different, unknown nature, and therefore is
more attractive for further investigation.
CONCLUSION
All the data obtained by the four HERE detectors in August 1987 to
January 1988 confirm the identification of the hard X-ray source in the
Large Magellanic Cloud having an unusual spectrum (see Figure 6) with
SN1987N The upper limits at 3
~
1.0
0.8
0.6
~ 0.4
o
o
0.0
-0.2
-0.4
-06
~1
@
@
/
t
%
\
lx ~
@
_ ~
/// ~
~ it/ ~
In//
~ ~ a'
@
/
/
06 0.4 0.2 0.0 -0.2 -0.4 -0.6
DEGREES
nG~ 6 anion of lbe ban <~ =~ ~ me Awe ~ag~lanic cloud awning
Ill. ~e=~_~,
and ~ ~ slant for 1be enemy bong 13~ (dolled ~- and ~-1~ ~ and
hem ~ pant. P=ilio~ of The ~ ARC <1 (1), PER 03~3 ha, SN1
~d. IS of me ~ d-= ~ ~1 ads of o-~1io~ am sb~
sell
382
AMERICAW AND SOVIET PERSPECTIVES
TABLE 3 The upper limits on the X-ray flues (in photons cm -2 S-1
keV~~) from LMC X-1 and PSR 054~693 at three standard deviation
level ~ accordance with the HEXE data obtained in 1987 August - 1988
January. They were reconstructed during localization used a number of
offset observations
source | ls-45 keV | 4s- 105 keV
LMC X-1 5.s 10-s ~ 0 10-6
PSR 0540-693 2.9 ~ 10 s 6. 8 · 10- 6
confident signal from the SN1987A region in spite of other X-ray sources
LMC X-1 and PSR 0540~93 having been in the HEXE field of view. Ikking
into account the donations between the direction of the telescope axis and
directions on these X-ray sources, an efficiency of the flux detecting from
different sources differed. The upper limits on the flues from SN1987A
and other sources are presented in Figure 1 and 7 and also in 1kble 4.
The weakness of the hard X-ray flux from LMC X-1 in May-June 1989
(Sunyaev et al. 1989) and the closeness of the upper limit on the LMC
X-1 hard emission obtained by the HEXE device to limits obtained during
the HEAO A2 (Wait and Marshall 19843 and HEAO A4 (Matteson and
Peterson 1987) experiments, testis to a small portion of the LMC X-1
flux to the flux detected by the Kvant module during August 1987 to April
1988. Note Hat the 0= detected in January 1988 exceeds the upper limits
obtained in May-June 1989 are about one order of magnitude.
Note in conclusion that the supernova light curie in 45-105 keV energy
band did not show a single sharp statistically confident burst similar to the
burst observed by the Ginga satellite in January 1988 in the softer energy
band. In hard X-rays the light curie was smooth as it was expected for the
light curve of the source connected with radioactive decay.
ACKNOWLEDGEMENTS
The authors are grateful to V.D. Blagov, V.M. Loznikov, VG. Rodin,
AM. Prudkog~d, the team headed by YmP. Semenov, and the cosmonauts
working aboard the Mir space station for the observatory control.
HIGH-ENERGY ASTROPHYSICS
10-1
1o2 1
LMC X-1
1
1
11
11
-
. .
>E 10 3 ,.\
I TO ~g
1 0 ~\
JO 6 ~1 1
0.5 1.0 5.0 10
_ 1
100
ENERGY (keV)
104 PSR 0540-693
C)
_ _
.O
N
C 105 _
o _
o
_
_
-
X _
lL _
10-6
3283
\
\
, , , , , ,,,, \ ,
10'
1o2
ENERGY (keV)
FIGURE 7 (a) Spectrum of LMC X-1 according to the HEAO A2 experiment (crossest
(Wait et al. 19843. The upper limits on the hard X-ray flux from this source according to
the ElEXE data. Ibe analytical approximation of the 11M instrument data is shown By a
solid line (Sunyaev et al. 1990~. (by Spectrum of PSR 0540~93 (a power law approximation)
in accordance with the observatory Einstein (Claris et al. 1982; Seward et al. 1984) and the
upper limits on the hard X-ray 0= according to the HEXE data. The spectrum obtained
by the 11M instrument (Sunyaev et al. 1990) coincides with the presented power law
approximation within the limits of experimental data errors.
384
AMERICAN AND SOVIET PERSPECTIVES
TABLE 4 The average efficiencies of the observatory Roentgen pointing
and the corresponding upper lets at three standard deviation levels on
the X-ray fluxes (in photons cm -2 s-1 keV~l) from the LMC sources
observed by the HEM device in 1989 May-June.
Source Ef f iciency 15- 45 keV45- 105 keV
. ;
SNl987A 52 % 2. 1-10 s 8 6 10-6
LMC X-1 1 32 % 8.5-10-s ~ 1.2 10-5
PSR 0540-693 45 ~3 .4 10 ~ s 9, 5 . 10~ 6
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