COMPTEL Observations of the Flaring Quasars PKS1622-297 and PKS0446+112
Zhang Shu, Li Tipei, Wu Mei
Two flaring quasars PKS1622-297 and PKS0446+112 observed by COMPTEL during
VP 423.0 and VP 36.0+36.5 have been studied with a direct demodulation method.
Images for both quasars are only obtained in the energy range 10-30 MeV and no
convincing results can be derived at lower energies. With the obtained flaring
fluxes, we find that the trends of flux evolution are different for the two
flaring quasars at MeV energies. Our flux for the flaring quasar PKS1622-297
is about a factor of 1.5 higher than the earlier report given by Collmar et al.
and, with our flux, the 10-30 MeV time variability
of flux for PKS1622-297 follows well the trend as observed by EGRET at
energies above 100 MeV, while such consistency with EGRET is hard to be seen
for the flaring quasar PKS0446+112. The 10-30 MeV light curve of PKS1622-297
shows it behaves a significant MeV variability within one month: the flux
increases first with a factor ~ 2.5 and then the major flare ends with
flux decrease of a factor ~ 4 in one month. Such time variability of flux
is also consistent well with that observed by EGRET at higher energies. For
PKS0446+112, EGRET observed a factor ~ 4 of flux decrease over one month
from VP 36.0+36.5 to VP 39 and the 10-30 MeV light curve observed by COMPTEL,
however, shows little evidence of such feature. Nevertheless, the detection
and non-detections of PKS0446+112 in the energy range 10-30 MeV still follow
the EGRET trend and the flux obtained by us indicates a MeV flare occurred
also during VP 36.0+36.5. The common feature of hard spectrum for the
two quasars may lead to their non-detections at lower COMPTEL energy range,
while the different behaviors of flux variability at MeV energies suggest
the two quasars may undergo different flaring mechanism.
File translated from TEX by TTH, version 2.32.
On 7 Sep 1999, 10:19.