Issue |
Astron. Astrophys. Suppl. Ser.
Volume 123, Number 3, June II 1997
|
|
---|---|---|
Page(s) | 569 - 574 | |
DOI | https://doi.org/10.1051/aas:1997173 | |
Published online | 15 June 1997 |
The long-term optical behavior of Mkn 421
1
International School for Advanced Studies, Via Beirut 2-4, 34013 Trieste, Italy e-mail: fkliu@sissa.it
2
Yunnan Observatory, Academia Sinica, P.O.Box 110, Kunming 650011, China
3
Center for Astrophysics, CCAST (World Laboratory), Beijing, China
Send offprint request to: B.F. Liu
Received:
6
February
1996
Accepted:
22
October
1996
All data available in B band for the BL Lac object Mkn 421 from 22
publications are used to construct a historical light curve, dating
back to 1900. It is found that the light curve is very complicated and
consists of a set of outbursts with very large duration. The
brightness of Mkn 421 varies from 11.6 magnitude to more than 16
magnitude. Analyses with Jurkevich method of computing periods of
cyclic phenomena reveal in the light curve two
kinds of behaviors. The first one is non-periodic with rapid, violent
variations in intensity on time scales of hours to days. The second one
is periodic with a possible period of years. Another possible
period of
years is not very significant. We have tested
the robustness of the Jurkevich method. The period of about one year
found in the light curves of Mkn 421 and of other objects is a spurious
period due to the method and the observing window. We try to explain the period of
years under the thermal instability of a slim
accretion disk around a massive black hole of mass
.
Key words: accretion, accretion disk / BL Lac objects: individual: Mkn 421
© European Southern Observatory (ESO), 1997