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IAUC 6793: GRB 971214; 4U 1915-05

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                                                 Circular No. 6793
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)


GRB 971214
     J. Rhoads, Kitt Peak National Observatory (KPNO), for the KPNO
gamma-ray-burst follow-up team, reports:  "We imaged the field
surrounding GRB 971214 with the KPNO 0.9-m telescope in the I band
from Dec. 17.37 to 17.55 UT.  The proposed optical counterpart
(Halpern et al., IAUC 6788) was detected in a combined image with
220 min of total integration time.  The transient was at mag I =
22.9 +/- 0.4, based on stellar magnitudes and positions provided by
J. Halpern (priv. comm.) for stars of I = 15.93 and 18.46 at R.A. =
11h56m29s.86, Decl. = +65o12'15".9 (equinox 2000.0), and
11h56m25s.80, +65o11'35".9, respectively.  Images and further
details are available at http://www.noao.edu/noao/grb/971214.html."


4U 1915-05
     D. Barret, J. F. Olive, and L. Boirin, Centre d'Etude Spatiale
des Rayonnements, Toulouse; J. E. Grindlay, P. F. Bloser, and Y.
Chou, Harvard-Smithsonian Center for Astrophysics; and J. H. Swank
and A. P. Smale, Goddard Space Flight Center, NASA, report:
"Observations of the x-ray burster 4U 1915-05, obtained with the
RXTE PCA between 1996 Feb. and Oct., show clear evidence for high-
frequency quasiperiodic oscillations (HFQPO) in its persistent x-
ray emission.  The strongest signals were detected as follows:  May
16, 1016 +/- 10 Hz, 6-sigma detection, FWHM = 75 +/- 10 Hz, rms =
18 +/- 3 percent, countrate 35.6 counts/s/PCU unit (5-30 keV); May
23, 830 +/- 10 Hz, 7-sigma, 80 +/- 10 Hz, 15 +/- 2 percent, 34.8;
June 1, 935 +/- 10 Hz, 7-sigma, 70 +/- 10 Hz, 15 +/- 2 percent,
31.2; Sept. 6, 860 +/- 20 Hz, 8-sigma, 200 +/- 20 Hz, 17 +/- 2
percent, 31.6.  HFQPOs at comparable frequencies may also be
present in the May 15 and May 17 data (890, 920 Hz), with lower
significance.  Furthermore, on May 16 we see evidence (3.3 sigma)
for a second HFQPO peak at about 650 +/- 15 Hz (FWHM = 50 +/- 20 Hz,
rms = 12 +/- 2 percent).  A signal of 600 +/- 10 Hz at 5.3 sigma is
also detected in the Oct. 29 data (FWHM = 50 +/- 10 Hz, rms = 11
+/- 2 percent, 33.4 counts/s/PCU units) with no accompanying HFQPO
detection above about 900 Hz.  For the two observations for which
the countrates were significantly larger (March 13, 68.5
counts/s/PCU; May 5, 56.5), no HFQPOs were detected.  Further
analysis is continuing; nevertheless these results may be important
for the planning of further RXTE observations of the source."

                      (C) Copyright 1997 CBAT
1997 December 20               (6793)            Daniel W. E. Green

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