Attempts were made to detect optical bursts from the gamma-ray burst source GBS 0526-66 during Dec. 31, 1984 to Jan. 2, 1985 and Feb. 23 to Feb. 24, 1985, using the one meter reflector of the Kavalur Observatory. Jan. 1, 1985 coincided with the zero phase of the predicted 164 day period of burst activity from the source (Rothschild and Lingenfelter, 1984). A new optical burst photon counting system with adjustable trigger threshold was used in parallel with a high speed photometer for the observations. The best time resolution was 1 ms and maximum count rate capability was 255,000 counts s(-1). Details  of the instrumentation and observational results are presented

Bhattacharyya, J. C.

Kasturirangan, K.

Marar, T. M. K.

Rao, U. R.

Seetha, S.

Sreenivasaiah, K. V.

English

NASA Technical Reports Server

28 O_ 1.1-8
SEARCH FOR OPTICAL BURSTS FROM THE GAMMA RAY BURST
SOURCE GBS 0526-66
S.Seetha, K.V.Sreenivasaiah, T.M.K.Marar,
K.Kasturirangan, U.R.Rao
ISRO SATELLITE CENTRE
Airport Road
BANGALORE - 560 017
INDIA
&
J.C.Bhattacharyya
INDIAN INSTITUTE OF ASTROPHYSICS
BANGALORE - 560 034
INDIA
ABSTRACT
Attempts were made to detect optical bursts
from the gamma-ray burst source GBS 0526-66
during Dec. 31, 1984 - Jan. 2, 1985 and
Feb. 23 - Feb. 24, 1985, using the one metre
reflector of the Kavalur Observatoly. Jan. I,
1985 coincided withthe zero phase of the
predicted 164 day period of burst activity
from the source (Rothschild and Lingenfelter,
1984). A new optical burst photon counting
system with adjustable trigger threshold was
used in parallel with a high speed photometer
for the observations. The best time resolution
was 1 ms and maximum count rate capability was
255,000 counts s-I. Details of the instrumen-
tation and observational results are presented
in this paper.
i. Introduction. The gamma_ray burst source GBS 0526-66 of
March 5, 1979 is unique in several respects (reviewed by
Cline, 1980). It exhibited the most intense gamma-ray burst
ever recorded. It is the only source for which there is a
tentative identification of the positional error box that
lies in the direction of a previously known celestial object,
namely, the N49 supernova remnant in the Large Magellanic
cloud (Cline et al., _82). Another interesting feature of
this object is its recurrent behaviour. Based on the ordered
pattern of recurrence times of fifteen w:eaker bursts observed
bv Golenetskii et al., (1984), Rothschild and Lingenfelter
(1984) have predicted a possible 164 day period for burst
occurence from this source. On_ical bursts reaching a maximum
b_ightness of mv=8.4 have been detected from the above region
of the sky by Pedersen, et al., (1984). Of the three optical
3 O~ .1-8 
RCH F R PTICAL URSTS F OM THE A MA ~  URST 
URCE BS 526- 6 
.S etha, .V.Sreeniv saiah, . .K.Marar, 
.Kasturira gan, H.R.Rao 
I O TELLITE ENTRE 
irport oad 
NGALORE - 0 17 
DIA 
 
. .Bhattacharyya 
IAN STITUTE F STROPHY ICS 
NGALORE 60 34 
IA 
BSTRACT 
ttempts ere ade t  etect ptical ursts 
fro  the qa ma-rav burst source GBS 0526-66 
uring ~. , ~84 - J n. , 85 a d 
eb.  - eb. 4, 985, sing t e e etre 
flector f e avalur bservato:ry. n. 1, 
1985 coincided ith the zero phase of the 
predicted 164 day period of burst activity 
fr  t  urce ( othschild d ingenf lter, 
1984). A new optical burst photon counting 
syste  ith adjustable trigger threshold as 
used i  arallel ith a iqh speed photometer 
r e bservations. he est e solution 
as 1 s and axi um c unt r te pability as 
5, 0 unts l. etails f e t men-
t ti n d servational sults  resented 
in this paper. 
1. I troduction. The gamma~ray urst source BS 0526-66 f 
arch , 1979 i  ique i  s veral r spects (re ie ed by 
line, 1980). It exhibited the ost intense ga ma-ray burst 
er recor,d,ed. t i  t e ly s urce f r hich t re i  a 
tentative identification of the positional error box that 
lies in the direction of a previously known celestial ject, 
na ely, the N49 supernova re nant in the Large agellanic 
l d ( li e t 1.,~ ). nother i teresting f ture f 
t is ject is it  recurrent ehaviour. ased on t e r ered 
pattern of recurrence ti es of fifteen w:eaker bursts observed 
y olenetskii t l., ( 84), othschild d ingenf lter 
(1984) have redicted a ssible 164 day eriod f r rst 
curence fr  t is s urce. p~ical ursts r ching a axi um 
bf!"ight,ness of mv=8. 4 have been detected from the above region 
of the sky by Pedersen, et l., (1984). f the three tical 
https://ntrs.nasa.gov/search.jsp?R=19850025596 2020-03-20T17:55:20+00:00Z
24
OG 1.1-8
bursts observed by them, the burst of February 8, 1984, which
lasted nearly 400 ms, coincided with the zero phase of the 164
day period.
In order to confirm the periodic nature of GBS 0526-66
and to zero-in on the precise location of the source respon-
sible for the above gamma-ray bursts, an international
multiwavelength burst watch was co-ordinated by the European
Southern Observatory (Pedersen, 1984) around New year 1985.
January i, 1985 _3 days was estimated to correspond to the
zero phase of the 164 day period, when the burst activity was
expected to be maximum. The burst watch program consisted
of observations of the source region in all wavelength
bands of the electromagnetic spectrum ranging from gamma-rays
to radio waves. As part of this international burst watch
we carried out high speed photometric observations with the
one metre telescope of the Kavalur Observatory using a newly
built optical burst photon counting system. This instru-
mentation could record data with an integration time of 1 ms
for a total duration of 31 s after burst detection above a
preset threshold. This paper presents details of the instru-
mentation and observational results.
2. Instrumentation. A single channel photometer with a
Johnson V filter and a rectangular diaphragm of 20 x 80
arc sec centred on the error box of GBS 0526-66 was used
for the observations. Figure 1 shows a schematic of the
data recording equipment. The data was recorded in two
PMT I--->-IAMP _ DISC I-_ COUNTER_ _A_'_-_ P->-4 .....
C31034 9315 HP_'
__t I !,T"IERI -
I
, CONTROLLED TAPE I IL GIC,-M MORY RECOROER
PRINTER I
EPSON RX-80 II
BURST PHOTON COUNTING SYSTEM ]
FIG.1 SCHEMATIC OF THE HIGH SPEED PHOTOMETER
24 
OG 1.1-8 
bursts observed by them, the burst of Feb uary 8, 1984, which 
lasted nearly 400 ms, coincided with the zero phase of the 164 
day period. 
In order to confirm the periodic nature of GBS 0526-66 
and to zero-in on the precise location of the source respon-
sible for the above gamma-ray bursts, an international 
multiwavelength burst watch was c -ordinated by the European 
Southern Observatory (P d rsen, 1984) around New year 1985. 
January 1, 1985 ±3 days was estimated to correspond to the 
zero phase of the 164 day 'period, when the burst activity was 
exp cted to be maxi um. The burst watch program consisted 
of observations of the source region in all wavelength 
bands of the lectromagnetic spectrum ranging from gamma-rays 
to radio waves. As part of this international burst watch 
we carried out high speed photometric observations with the 
one m tre t lescope of the Kavalur Observatory using a newly 
built optical burst photon cou ting ystem. This instru-
mentation could record d ta with an integration time of 1 ms 
for a total duration of 31 s after burst detection above a 
pr set threshold. This aper pr sents details of the instru-
mentation and observational results. 
2. Instrumentation. A single channel photometer with a 
Johnson V filter and a rectangular diaphragm 'of 20 x 80 
arc sec centred on the error box of GBS 0526-66 was used 
for the observations. Figure 1 shows a schematic of the 
d ta recording equipment. The d ta was recorded in two 
COOLED 
PMT 
ClIO)' 
AMPI 
DISC 
9102 
r----
I 
PHOTON 
COUNTER 
9315 
I MICROPROCESSOR 
CONTROLLED 
LOGIC & MEMORY 
~MPUNG 
CONTROL 
UNIT 
9320 
CASSETTE 
TAPE 
RECORDER 
FIG.l SCHEMATIC OF THE HIGH SPEED PHOTOMETER 
PRINTER 
• 
25 OC, 1.1-8
parallel channels. The first channels was used for continuous
photometric recording at 1 sec integration time while the
second channel using the new burst photon counting system
recorded data with 1 ms resolution whenever the optical
photon counting rate exceeded a preset burst threshold.
A thermoelectrically cooled RCA C31034 tube was used
in the photometer. Output signals from the phototube were
amplified using a fast preamplifier (Ortec 9301). The
signals from the preamplifier were fed to an amplifier/
discriminator (Ortec 9302) the output of which was
parallely fed to the two channels of data recording. The
first channel which was operated continuQuSly_cQnsiS_ed_of
a fast photon counter (Ortec 9315) followed by a sampling
control unit (Ortec 9320), the output of which was printed.
The printing speed of this channel limited the integration
time to a minimum of 50 ms.
The second channel consisted of instrumentation built
solely for burst observations with a maximum storage capacity
of 255 counts/ms (255,000 c s-l) . It consisted a micro-
processor controlled logic and memory capable of storing data
of 32 sec, duration with 1 ms resolution. Of the 32 sac, one
second corresponded to preburst circulating memor X which was
frozen once the burst trigger was enabled. This gave
information on the rising portion of the burst light curve.
The rest of the 31 sac data was stored after the burst trigger
was enabled. The burst trigger was enabled based on compa-
rison of the photon count rate for 20 ms with a threshold
set by the observer. Thresholds could be set to any value
from 1 to 255 counts per 20 ms (50 counts/sec to 12750 counts/
sac). Correspondingly 20 ms data sets were compared with this
threshold and the moment the threshold was crossed, the
_nstrumentation gave an indication and stored data for the
next 31 sac. This data could then be read out and stored on
a cassette tape recorder to be retreived later and printed
out for data processinG.
3. Observations and conclusions. Although the instrumen-
tation was operational fo'r_observations during the inter-
national burst watch from December 31 to January 2, 1985,
we could not carry out any observations during this time
because of cloudy skies. However on February 23 and 24,
1985, we conducted photometric observations of_the source
_{ a total duration of 2 hours (i.e., from 15 h 42m UT to12m UT on 23 February and from 14 _ 48m UT to 16h 30m
UT on 24 February). The average phase at the time of these
observations was 0.33, as extrapolated from the zero phase
quoted by Rothschild and Lingenfelter. The count rate
measured from the comparison star SAO 249271 (mv=9) was
about 5000 counts/sac. The count rate from the diaphragm
centred on GBS 0526-66 was about 700 counts/sec. This
corresponded to 14 counts in 20 ms. The threshold was
set at 40 counts in 20 ms, to avoid spurious triggering.
25 or: .1-8 
parallel channels. The first channels was used for continuous 
photometric recording at 1 sec integration ti e hile the 
second ha nel sing t e new urst hoton ounting stem 
recorded ata ith  s r solution hen ver t e ptical 
photon counting rate exceeded a preset burst threshold. 
 t ermoele trically cooled CA 31034 t be as sed 
in the photometer. utput signals fro  the ~hototubewere 
a plified using a fast preamplifier (Ortec 9301). The 
signals fro  the preamplifier ere fed to an a plifier/ 
iscriminator rtec 302) t e utput f hich as 
parallely fed to the two channels of data recording. The 
first channel hich as operated continu~:::ms}yc'cQnsisted,)df 
a fast photon counter ( rtec 9315) followed by a sa pling 
control unit ( rtec 9320), the output of which was printed. 
The printing speed of t is channel li ited the integration 
t e   ini um f  s. 
he cond a nel nsisted f strumentation uilt 
solely f r urst bservations ith a axi um st rage capacity 
f 5 ounts/ms ( 5, 0 c -l). t nsisted a icro-
processor controlled logic and emory capable of st ring data 
f 32 s c, uration ith 1 s r solution. f t e 32 sec, e 
second corresponded to reburst circulating emory vvhich as 
zen nce  urst ger as abled. his ave 
i f rmation  t e ri i g ortion f t  urst li ht rve. 
he st f   ec ata as red fter  urst ger 
as enabled. The burst trigger as enabled based on co pa-
rison of the photon count rate for 20 ms ith a threshold 
set by the observer. hresholds could be set to any value 
fro  1 to 255 counts per 20 ms (50 counts/sec to l2j50 counts/ 
sec). correspondingly 20 s data sets ere co pared ith this 
reshold d e oment  reshold as sed,  
i strumentation ave a  i ication a d st red ata f r t  
ext  e . his ta uld n  d t d red  
a assette ta e recorder t  be r treived l t r and ri ted 
out for data processina. 
. bservations  nclusions. lt ough t  i t en-
t ti n as erational f r bservations ring t e i t r-
ational urst atch fr  ecember  t  uary , 85, 
e could t carry t any servations during t is ti e 
ecause f l dy ies. owever  bruary   , 
1985, we conducted photometric observations ofhthe source 
for a total duration of 2 hours (i.e., from 15 42m UT to 
l6h m    bruary  ro  l n m  t  l h m 
UT on 24 ebruary). he-average phase at the ti e of these 
servations as . 3, s trapolated fro  t  r  ase 
quoted by othschild and ingenfelter. The count rate 
easured fro  the co parison star SAO 249271 (m =9) was 
out 0 unts/sec. e unt t  fro  t  i ragm 
ntred   6- 6 as ut  unts/sec. is 
corresponded to 14 counts in 20 s. The threshold as 
s t t 40 counts i  20 s, t  avoid s rious tri ering. 
26 OG 1.1-8
This level corresponded to a signal level 6 sigma above the
background and to mv_10. With these settings no rise in
count rate was observed in either of the channels. This
indicates that no burst brighter than about llth magnitude
lasting for longer than 1 sec and no sharp bursts brighter
than 10th magnitude lasting for longer than 20 ms, was
recorded. It may be noted that two of the sixteen gamma-ray
bursts observed earlier from this source were detected around
a phase of 0.33. One could therefore expect an optical
burst around this phase if every gamma-ray burst is accom-
panied by an optical burst. However optical bursts are
expected to last for a very short duration, and therefore the
length of our data does not enable us to place stringent upper
limits on the occurrence of these bursts.
4. Acknowledgement. The authors thank M.R. Sharma,
C.N. Umapathy and N.S.R. Murthy for support in electronics
instrumentation and Jayakumar, K.R.N. Kutty, V.N. Padmini
and V. Devasagayam for observational and additional support
in the preparation of this paper.
References
i. Cline, T.L., 1980, Comments on Astrophysics., 9, 13.
2. Cline, T.L., et al., 1982, Astrophys. J. Lett.,
255, L. 45.
3. Golenetskii, et al., 1984, Nature, 307, 41.
4. Pedersen, H., et al., 1984, Nature 312, 46.
5. Pedersen, H.,et al., 1984, European Southern
Observatory Circular, dated Nov. 6.
6. Rothschild, R.E., and Lingenfelter, R.E., 1984,
Nature, 312, 737.
26 0(; . -8 
his l vel o resDonded t   ianal vel  iqrna bove e 
ackground and t  v,vlO. ith t ese e tings o i e  
count rate as observed i  either of t e channels. his 
i dicates t at o urst righter t an bout 11th agnitude 
sting r l nger an  ec nd o ar? ursts righter 
t an 0th agnitude l sting r nger t an 0 s, as 
r corded. t ay e oted t at t o f e i t en a ma-ray 
ursts bserved arlier fr  t is urce ere etected r und 
 hase f .33. ne ould erefore xpect n ptical 
urst r und t is hase  very a ma-ray urst  com-
anied y n ptical urst. ow ver ptical ursts re 
xpected t  st r  ery ort uration, d erefore e 
gth f ur ata oes ot able s  lace tri gent pper 
li its n t e currence f t ese ursts. 
. cknowledgement. he thors ank .R. harma, 
. . m pathy nd .S.R. ~urthy r port  lectronics 
strumentation d yakumar, .R.N. utty, .N. adm ni 
d . evasag yam r bservational d ditional port 
 e reparation f is apEr. 
eferences 
1. line, .L., 980, o ments n strophysics., ~  3. 
. line, .L., t l., 82, strophys. . ett., 
55, . 5. 
. ol netskii, t l., 984, ature, 07, 1. 
~
. edersen, ., t l., 984, ature ~, . 
. edersen, .,et l., 84, uropean outhern 
bservatory ircular, ated ov. . 
. othschild, .E., d ingenf lter, .E., 984, 
ature, 12, 37. 
• 


Search for optical bursts from the gamma ray burst source GBS 0526-66

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