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IAUC 6892: SAX J0840.7+2248; Mkn 421; 1998bp

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IAUC number

                                                 Circular No. 6892
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SAX J0840.7+2248
     J. Heise and J. in 't Zand, Space Research Organization of the
Netherlands, Utrecht; R. Ricci, G. d'Andreta, and J. Muller,
BeppoSAX, Rome; and L. Piro, Istituto di Astrophysica Spaziale,
Rome, report:  "A bright, high-latitude fast x-ray transient source
has been observed on Apr. 29.366 UT in one of the Wide Field
Cameras of BeppoSAX.  The event lasted about 110 s.  The peak
intensity of the structured event reached about 1 Crab (2-25 keV).
Its position is determined at R.A. = 8h40m40s, Decl. = +22o48'.3
(equinox 2000.0; error radius 3') and the source is designated SAX
J0840.7+2248.  A follow-up observation with the BeppoSAX narrow-
field instruments is in progress."

     P. Grandi, Istituto di Astrofisica Spaziale, CNR, Rome; and L.
Chiappetti, Istituto di Fisica Cosmica e Tecnologie Relative, CNR,
Milan; L. Maraschi, Osservatorio Astronomico di Brera, Milan; and
E. Pian, Istituto di Tecnologie e Studio delle Radiazioni
Extraterrestri, CNR, Bologna; on behalf of the BeppoSAX
collaboration on the coordinated campaign for spectral variability
of Mkn 421, report:  "This object was observed with the BeppoSAX
Narrow Field Instruments on Apr. 21.08-22.13 UT.  The source was
bright and variable, and it showed a well-defined flare with an
initial 50-percent increase over 15 000 s, followed by a slower
regular decrease to about half the peak intensity.  The source was
well visible in the Phoswich Detector System up to about 50 keV.
The preliminary standard analysis indicates an average energy flux
of 3.2 x 10E-10 erg cmE-2 sE-1 in the band 2-10 keV, close to the
maximum reported by ASCA on Apr. 27 (IAUC 6888).  Another BeppoSAX
observation on Apr. 23-24 found an average flux of 1.9 x 10E-10
erg cmE-2 sE-1 (2-10 keV).  Thus the bright active state extends
at least for a week and may persist for a longer time.  Continuing
observations at all wavelengths are urged."

SUPERNOVA 1998bp IN NGC 6495
     S. Nakano, Sumoto, Japan, forwards the following position and
magnitude for SN 1998bp (cf. IAUC 6890) from a CCD image obtained
with a 0.4-m f/6 reflector by R. Kushida at Yatsugatake South Base
Observatory on Apr. 30.75 UT:  R.A. = 17h54m50s.74, Decl. =
+18o19'50".5 (equinox 2000.0), V = 15.0 (measurer Y. Kushida).

                      (C) Copyright 1998 CBAT
1998 May 1                     (6892)            Daniel W. E. Green

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