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IAUC 7011: 1998dx; 1998dt; 1998dh

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                                                 Circular No. 7011
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 1998dx IN UGC 11149
     M. Modjaz, T. Shefler, E. Halderson, J. Y. King, W. D. Li,
R. R. Treffers, and A. V. Filippenko, University of California at
Berkeley, report their discovery of a supernova during the course
of the Lick Observatory Supernova Search (cf. IAUC 6627) with the
0.8-m Katzman Automatic Imaging Telescope (KAIT).  SN 1998dx was
found and confirmed on unfiltered images taken on Sept. 10.2 (mag
about 18.3) and 12.2 UT (mag about 17.9), respectively.  The object
is located at R.A. = 18h11m11s.89, Decl. = +49o51'40".7 (equinox
2000.0), which is about 20".9 east and 12".2 south of the nucleus
of UGC 11149.  A KAIT image obtained on Sept. 7.2 showed the new
star at mag 18.8, and an image taken on Sept. 3.2 already showed a
hint of the supernova.  There is nothing at the position of SN
1998dx (limiting mag about 19.0) in a KAIT image obtained on July
30.3.
     S. Jha, P. Garnavich, P. Challis, and R. Kirshner, Harvard-
Smithsonian Center for Astrophysics, report that a spectrum of SN
1998dx taken by P. Berlind with the F. L. Whipple Observatory 1.5-m
telescope (+ FAST spectrograph) on Sept. 14.2 UT reveals that it is
a type-Ia supernova near maximum light.  No direct host-galaxy
recession velocity information is available, but the prominent Si
II (rest 635.5 nm) absorption feature appears at 645 nm.  Assuming
a photospheric expansion velocity typical of maximum-light type-Ia
supernovae, such that the feature would appear at 615 nm in the
host-galaxy frame, the observed wavelength would imply a
host-galaxy recession velocity of 15 000 km/s.


SUPERNOVA 1998dt IN NGC 945
     Jha et al. also write:  "A spectrum of SN 1998dt (cf. IAUC
7006) taken by M. Calkins on Sept. 12.4 UT (equipment as above)
exhibits a blue continuum and strong absorption lines of He I and
Fe II, indicating that the supernova is of type Ib near maximum
light.  The host galaxy recession velocity is 4600 km/s, measured
from narrow emission lines of H-alpha."


SUPERNOVA 1998dh IN NGC 7541
     CCD V magnitude estimates (cf. IAUC 6989):  Aug. 15.957 UT,
14.2 (D. Hanzl, Brno, Czech Republic); 25.854, 14.65 (Hanzl);
27.974, 15.0 (D. Rodriguez, Madrid, Spain); Sept. 9.80, 15.70 +/-
0.05 (L. Kiss, Konkoly Observatory, Piszkesteto).  Unfiltered CCD
magnitude estimates (cf. IAUC 6999):  July 29.87, 14.3 (S. Moretti
and S. Tomaselli, Forli, Italy); Aug. 30.94, 15.0 (L. Boschini,
Miragolo, Bergamo, Italy).

                      (C) Copyright 1998 CBAT
1998 September 14              (7011)            Daniel W. E. Green

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