The result of two searches for infrared counterparts of Gamma-ray Bursters (GRB's) is reported. The first search was made using data from the Infrared Astronomy Satellite and covered 23 positions. The second search was made with the Kitt Peak 1.5 m telescope and covered 3 positions. In neither of these two searches was any infrared candidate detected

Cline, T. L.

Schaefer, B. E.

English

NASA Technical Reports Server

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SEARCHFOR INFRAREDCOUNTERPARTSOF GAMMA-RAYBURSTERS
Bradley E. Schaefer* and Thomas L. Cline
NASA/Goddard Space Flight Center, Code 661
Greenbelt, MD 20771, U.S.A.
ABSTRACT
We report here the result of two searches for infrared
counterparts of Gamma-ray Bursters (GRB's). The first
search was made using data from the IRAS satellite and
covered 23 positions. The second search was made with
the Kitt Peak 1.5 m telescope and covered 3 positions.
In neither of these two searches was any infrared
candidate detected.
1. Introduction. Despite the decade of intense gamma-ray observations
since their'discovery, nothing positive is known about the nature of
GRB's; however, there is a suspicion that neutron stars are somehow
involved. It has become apparent that gamma-ray observationsalone
cannot determine the nature of the GRB system.
Currently, one of the best hopes for a breakthrough is the
discovery of a quiescent low energy counterpart. A quiescent
counterpart would allow for very deep studies at many wavelengths with
high angular resolution. In addition, radiation from the quiescent
system will be more diagnostic of the system's components than burst
radiation. Low energy observations are cheaper, easier, more sensitive,
and easier to interpret than high energy observations. Already many
searches have been made for optical counterparts--butthe searches have
only demonstrated that the GRB's are very faint. So it seems that the
vital search for a counterpart may profitably shift to other
frequencies.
At infrared wavelengths, there are reasons to believe that the
quiescent GRB counterpart will be bright enough for a reasonable
observing program. Many leading models require the neutron star to have
a companion (e.g., Woosley and Wallace, 1982; Van Buren, 1981; Ventura
et al., 1983). The existence of the campanion is further supported by
Wood et al. (1981) on the basis of the 8-second period in GB790305. In
addit_Schaefer and Ricker (1983) have demonstrated that a large and
cool companion to the neutron star is required to explain the optical
flashes. The optical flashes ar_ readily explained by reprocessingoff
a small companion star with a 10 K temperature at a distance of 100 pc
(Rappaport and joss, 1985).
2. Results. The IRAS satellite has completed an all sky survey in four
broad bandpass filters between 12 and 100 _ (Neugebaueret al., 1984).
We have used the resulting point source catalog to search for any
* Also, University of Maryland, Department of Physics and Astronomy
College Park, MD 20742. Visiting astronomer at Kitt Peak National
Observatory
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SEARCH F R I F ARED UNTERPARTS F MMA-RAY STERS 
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infrared sources associated with any of 23 known burst positions. These
burst positions were chosen solely for their small size, so that it is
unlikely that a background source will appear inside the error box.
With one exception, no IRAS source was found in any of the boxes. The
sensitivity limits vary widely with position on the sky, but typically
are 0.25, 0.4, 0.6, and 1.0 Janskys for the 12, 25, 60, and I00
filters, respectively.
The GB790305 proves to be the one exception, as it often is. The
IRAS point source catalog indicates that a source is located within 14"
of (1950) 5h 25m 59.5s -66 ° 7' 3", which is consistent with the best
error box of Cline et al. (1982). The 12 u flux is 0.45 Jansky and the
25 u flux is 1.54 janskys. The 60 and I00 u filters provide
uninteresting upper limits. The region of the sky is extremely confused
with background point sources and diffuse emission. The distribution of
this background makes it problematic whether the point source is real.
Even if it is real, we unfortunately conclude that the emission would
undoubtedly be from the N49 supernova remnant itself: (I) The IRAS
spectral shape is indistinguishable from all other detected LMC and SMC
supernova remnants. (2) The X-ray brightnesses of all LMCand SMC
supernova remnants (Mathewson et al., 1983) are well correlated with the
IRAS detections. N49 is comparatively bright in the X-rays and, hence,
should provide infrared emission detectible by IRAS (at the observed
flux level) whether or not a GRBis along the line of sight.
Our second search for infrared counterparts was made with a 1.5m
telescope at Kitt Peak National Observatory in Arizona. We searched the
error boxes associated with the 18 April (Hurley, 1984, private
communication), 23 March (Laros et al., 1985), and 13 June (Barat et
al., 1984) 1979 GRB's. The sear_ was accomplished by raster scann_--_-ng
a 11.3" diameter aperture over the entire error box with typically
30 seconds of integration time per pixel. We looked in the K filter
(_ ~ 2.2 _) to a magnitude of 13.6 which equals 0.0023 Jansky. We found
only one infrared source in any of the three error regions. Subsequent
UBVRIJHK photometry shows that this source is a mv = 13 G-type star,
and, hence, is unlikely to be the counterpart.
It is disappointing that both our searches failed to identify any
likely candidates. However, the potential for high scientific returns
suggests that infrared searches should continue.
References
Barat, C. et al., 1984, Ap. J., 280, 150.
Cline, T. L. et al., 1982, Ap. J. Lett., 255, L45.
Laros, J. G. et al., 1985, Ap. J., 290, 728.
Mathewson, D._t al., 1983, Ap. J. Suppl., 51, 345.
Neugebauer, G. et a--1., 1984, Ap. J. Lett., 278, LI.
Rappaport, S. A. and Joss, P. C., 1985, Nature, 314, 242.
Schaefer, B. E. and Ricker, G. R., 1983, Nature, 301, 43.
Van Buren, D., 1981, Ap. J., 249, 297.
Ventura, J. et al., 1983, Nature, 301, 491.
Wood, K. S. et a--l-., 1981, Ap. J., 247, 632.
Woosley, S. E. and Wallace, R. K., 1982, Ap. J., 258, 716.
OG 1.1-9 
28 
infrared sources associated with any of 23 known burst positions. These 
burst positions w re chosen solely for their small size, so that it is 
unlikely that a background source will appear inside the er or box. 
With one exception, no IRAS source was found in any of the boxes. The 
sens tivity l mits vary widely with position on the sky, but typically 
are 0.25, 0.4, 0.6, and 1.0 Janskys for the 12, 25, 60, and 100 ~ 
filters, respectively. 
The GB790305 proves to be the one exception, as it often is. The 
IRAS pOint source c talog indicates that a source is located within 14" 
of (1950) 5h 25m 59.5s _66 0 7' 3", which is consistent with the best 
error box of Cline et ale (1982). The 12 ~ flux is 0.45 Jansky and the 
25 ~ fl ux is 1. 54 Janskys. The 60 and 100 ~ fil ters provi de 
u interesting upper l mits. The region of the sky is extremely confused 
with background pOint sources and diffuse emission. The distr bution of 
this background makes it problematic whether the point source is real. 
Even if it is real, we unfortunately conclude that the emission would 
undoubtedly be from the N49 supernova rem ant itsel f: (1) The IRAS 
spectral shape is indistinguishable from all other d tected LMC and SMC 
supernova rem ants. (2) The X-ray brightn ses of all LMC and SMC 
supernova rem ants (Mathewson et al., 1983) are well correlated with the 
IRAS d tections. N49 is comparatively bright in the X-rays and, hence, 
should provide infrared emission d tectible by IRAS (at the observed 
flux l vel) whether or not a GRB is along the line of sight. 
Our second search for infrared counte parts was made with a 1.5m 
t lescope at Kitt Peak National Observatory in Arizona. We searched the 
error boxes associ ated with the 18 April (Hurl ey, 1984, pri vate 
co munication), 23 March (Laros et al., 1985), and 13 June (Barat et 
al., 1984) 1979 GRB's. The search was accomplished by raster sca nTng 
all.3" di ameter ape ture over the enti re error box with typically 
30 seconds of integration time per pixel. We looked in the K filter 
(A ~ .2 ~) to a magnitude of 13.6 which equals .0023 Jansky. We found 
only one infrared source in any of the three error regions. Subsequent 
UBVRIJHK ph tometry shows that this source is a mv = 13 G-type star, 
and, hence, is unlikely to be the counte part. 
It is disappointing that both our searches failed to identify any 
likely candidates. How ver, the potential for high scientific returns 
suggests that infrared searches should co tinue. 
References 
B rat, C. et al., 1984, Ap. J., 280, 150. 
Cline, T. L. et al., 1982, Ap. J. Lett., 255, L45. 
Laros, J. G. er--aT., 1985, Ap. J., 290, 728. 
Mathewson, D. s. et al., 1983, Ap. J. Suppl., 51,345. 
Neugebauer, G. et al., 1984, Ap. J. Lett., 278, LI. 
Rap aport, S. A. and Joss, P. C., 1985, Nature, 314, 242. 
Schaefer, B. E. and Ri cker, G. R., 1983, Nature, 301, 43. 
Van Buren, D., 1981, Ap. J., 249, 297. 
Ventura, J. et al., 1983, Nature, 301, 491-
Wood, K. S. et al.. 1981, Ap. J., 247, 632. 
Woosley, S. E. and W llace, R. K., 1982, Ap. J., 258, 716. 


Search for infrared counterparts of gamma-ray bursters

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