Central Bureau for Astronomical Telegrams
IAUC 4044: 4U 1323-62; NGC 3031
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Read IAUC 4045
Circular No. 4044
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
4U 1323-62
M. van der Klis and A. Parmar, European Space Agency; J. van
Paradijs, Astronomical Institute, Amsterdam; F. Jansen, Space
Research Laboratory, Leiden; and W. H. G. Lewin, Massachusetts
Institute of Technology, telex: "An EXOSAT observation of EXO 1323.5-
6180 shows that this x-ray burst source (cf. IAUC 3961) exhibits
periodic x-ray dips. Twelve dips of ~ 1 hr duration in the
(~ 5 ufu) 1-10 keV flux were observed with the medium-energy
instrument during Feb. 11.8-13.2 UT. The ephemeris of the dip
center is HJD = 2446108.187 (+/- 0.002) +/- 0.1223 (+/- 0.0003) E. A
similar dip, observed one year earlier (van der Klis et al. 1984,
18th ESLAB Symp., Scheveningen, Nov. 5-9), was centered on HJD
2445742.276. The dips do not reach the zero flux level and show
considerable variability on timescales < 1 hr. We also observed
six x-ray bursts, with a recurrence time of ~ 5.36 hr and an rms
deviation of the burst occurrence time of ~ 200 s (i.e., 1 percent
jitter). The burst peak fluxes were 10-20 times higher than the
persistent flux. The source was not detected in a quick-look
analysis of the low-energy-telescope data. From the variation of the
count rates observed when the medium-energy detectors were moved
over the source we estimate source's position to be within 15' of
R.A. = 13h23m5, Decl. = -61deg48' (equinox 1950.0). This is consistent
with the Einstein HRI database position (kindly provided by M.
Watson, Leicester University) of R.A. = 13h23m17s1, Decl. = -61deg52'35"4
(equinox 1950.0) and with the position of 4U 1323-62."
NGC 3031
P. Barr and P. Giommi, EXOSAT Observatory, report that EXOSAT
observations of the nearby emission-line galaxy NGC 3031 (M81) on
Feb. 21 have revealed an increase in the soft x-ray (0.1-4.5 keV)
flux by a factor of five, and in the 2-6-keV flux by a factor of
three, compared to Einstein Observatory measurements obtained during
1978/79. The 0.3-10-keV luminosity of NGC 3031 is now ~ 1.0 x
10**34 J/s. In addition, variability by up to 50 percent on a
timescale < 1 hr was detected. It is thus possible that Seyfert-type
activity may have commenced in this source, and optical
observations of its nuclear regions are urged.
1985 March 13 (4044) Brian G. Marsden
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