THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
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AAVSO ALERT NOTICE 248 (May 1, 1998)
1750+18 SUPERNOVA 1998bp IN NGC 6495
We have been informed by the Central Bureau for Astronomical Telegrams (IAU
Circular 6890) that Guy Hurst, Basingstoke, England, reports the discovery of
a supernova by Mark Armstrong, Rolvenden, England. Unfiltered CCD images
obtained on April 29.074, April 29.101, and April 29.128 UT showed the
supernova at magnitude 14.8. The exposures were made with a 0.26-m Schmidt
Cassegrain telescope as part of the U.K. Nova/Supernova Patrol.
No star was recorded down to magnitude 16.7 at the location of the supernova
on a CCD frame taken by Armstrong on March 20.283 UT. A CCD frame taken by
T. Boles, Wellingborough, England, in strong twilight on April 29.135 UT
showed SN 1998bp at magnitude 14.7, as estimated by Hurst.
The position provided by A. Sugie, Dynic Astronomical Observatory, Japan, and
reported by S. Nakano, Sumoto, Japan, shows SN 1998bp located at:
R.A. = 17h 54m 50.72s Decl. = +18degrees 19' 50.2" (equinox 2000.0)
and about 1" west and 13" north of the nucleus of NGC 6495. Sugie's CCD
frames taken on April 30.54 UT under poor conditions show SN 1998bp at V
magnitude 14.9 - 15.1 (IAU Circular 6890). R. Kushida, Yatsugatake South Base
Observatory, Japan, has also obtained a CCD image, taken with a 0.4-m
reflector, which shows the supernova at V magnitude 15.0 on April 30.75 as
reported by S. Nakano (IAU Circular 6892).
Spectroscopic confirmation was obtained by F. Patat, European Southern
Observatory, and M. Maia, Observatorio Nacional, Rio de Janeiro (IAU Circular
6890), using the ESO 1.5-m telescope (+ Boller & Chivens spectrograph) at La
Silla, Chile. They report that full reduction of their CCD spectrogram taken
on April 30.38 UT shows SN 1998bp to be consistant with a peculiar Type Ia
supernova roughly around maximum light.
A spectrum taken on April 30.4 UT by M. Calkins using the Whipple Observatory
1.5-m telescope (+ FAST spectrograph) and reported by S. Jha, P. Garnavich,
P. Challis, and R. Kirshner, Harvard-Smithsonian Center for Astrophysics (IAU
Circular 6891), confirms SN 1998bp to be a Type Ia supernova near maximum
Accompanying is an AAVSO 'e' scale Supernova Search Preliminary chart of NGC
6495, prepared by C. Scovil and showing the location of SN 1998bp. Please use
this chart to observe the supernova, and report your observations of 1750+18
SN 1998bp to AAVSO Headquarters, making sure you indicate which comparison
stars you used.
Congratulations to Mark Armstrong on his most recent discovery!
CHARTS AVAILABLE ON AAVSO FTP SITE
Chart links obsolete, 11/2013: Create charts using VSP at http://www.aavso.org/vsp 
Electronic copies of the AAVSO chart of SN 1998bp in NGC 6495 mentioned in
this Alert Notice are available from our FTP site:
ftp.aavso.org (220.127.116.11), in /pub/alerts/ alert248/
ftp.aavso.org (18.104.22.168), in /pub/charts/her/sn1998bp/
The chart may also be accessed through our Web site at the following address:
The answering machine at AAVSO Headquarters is on nights and weekends for your
convenience. Please call our charge-free number (800-642-3883) to report your
observations. We also encourage observers to send observations by fax to
617-354-0665 or by e-mail through the Internet to email@example.com .
Many thanks for your valuable astronomical contributions and your efforts.
Janet A. Mattei
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