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IAUC 7020: XTE J1550-564; C/1998 M5

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                                                 Circular No. 7020
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)
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Phone 617-495-7244/7440/7444 (for emergency use only)


XTE J1550-564
     R. Jain and C. Bailyn, Yale University; and J. Orosz,
Pennsylvania State University, report YALO consortium observations
using the Yale 1-m telescope at the Cerro Tololo Interamerican
Observatory:  "We have monitored the optical counterpart to XTE
J1550-564 (IAUC 7009) nightly since Sept. 13 UT.  The source has
varied by < 0.3 mag in V since its discovery.  We have adjusted our
instrumental magnitudes so that V = 16.7 and V-I = +1.80 near Sept.
16.0, as reported by Castro-Tirado et al. (IAUC 7013), and we find
that 16.6 < V < 16.9 over the range Sept. 8.99-21.97.  Thus there
is no dramatic optical response to the large increase in the x-ray
intensity over the last several days (cf. IAUC 7019).  Between
Sept. 15.0 and 21.0, there was a trend in the V-I color where the
source became increasingly redder.  We find V-I = 1.80 +/- 0.04
near Sept. 15.0 and 1.92 +/- 0.01 near Sept. 21.0.  YALO consortium
monitoring observations of XTE J1550-564 will continue; additional
observations are encouraged."


COMET C/1998 M5 (LINEAR)
     Ephemeris extension to IAUC 7004 (elements MPC 32410):

1998 TT     R. A. (2000) Decl.   Delta     r    Elong. Phase    m1
Sept.24    19 58.56   +40 17.0   1.764   2.331  111.9   23.5   10.9
Oct.  4    19 33.49   +39 31.0   1.803   2.253  103.2   25.6   10.8
     14    19 14.39   +38 27.3   1.855   2.178   94.7   27.2   10.7
     24    19 00.91   +37 24.1   1.910   2.106   86.9   28.1   10.6
Nov.  3    18 52.20   +36 34.3   1.961   2.039   80.0   28.6   10.6
     13    18 47.31   +36 05.7   2.002   1.976   74.2   28.8   10.5
     23    18 45.45   +36 03.5   2.029   1.920   69.5   28.8   10.4
Dec.  3    18 45.95   +36 31.4   2.038   1.870   66.1   28.8   10.3
     13    18 48.29   +37 32.9   2.028   1.827   64.1   29.0   10.2
     23    18 52.10   +39 12.0   1.998   1.793   63.6   29.4   10.0

     Visual m_1 estimates:  Aug. 26.85 UT, 10.8 (V. Znojil, Brno,
Czech Republic, 25x100 binoculars); Sept. 1.00, 11.1 (R. J. Bouma,
Groningen, The Netherlands, 0.25-m reflector); 8.85, 10.6 (M.
Reszelski, Szamotuly, Poland, 0.25-m reflector); 15.92, 11.1 (J.
Carvajal, Madrid, Spain, 0.32-m reflector); 19.04, 11.5 (J. Bortle,
Stormville, NY, 0.41-m reflector).

                      (C) Copyright 1998 CBAT
1998 September 23              (7020)            Daniel W. E. Green

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