Electronic Telegram No. 5368
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


V745 SCORPII = NOVA SCORPII 1897
     B. E. Schaefer, Louisiana State University, Baton Rouge, reports his
discovery of a nova eruption of the recurrent nova V745 Sco at magnitude B =
12.66 +/- 0.11 on an archival photographic plate at the Harvard College
Observatory.  The Harvard plate B19719 is a 10-min exposure centered at 1897
July 3.1593 UT, with a limiting magnitude of B = 13.6, taken with the 8-inch
Bache Doublet telescope at Arequipa, Peru.  The position of the nova was
measured via DASCH to be R.A. = 17h55m22s.26, Decl. = -33d14'58".1 (equinox
J2000.0), with this position being 0".6 away from the Gaia position for V745
Sco, with the nova image having a radius of 6".4.  A 600" x 600" close-up
centered on the nova image is shown at the following website URL:
http://www.cbat.eps.harvard.edu/cbet/V745Sco_CBET5368.jpg (where the position
of V745 Sco is marked with a blue arrow, along with five comparison stars and
their B magnitudes labeled; north is at the top, east is to the left, and the
whole close-up is 600" on a side).
     The nova image is slightly trailed with an ellipticity of 0.27 at p.a.
75 degrees, exactly like all the nearby images of stars of similar brightness.
The point-spread function (PSF) is a sharp-edged smooth ellipse, just like
the images of the nearby stars.  No significant extra images appear anywhere
on this plate.  The image passes tests for plate artifacts via eye examination
under magnification of the original glass plate.  Any main-belt asteroid on
this date would show detectable trailing, and a search for main-belt asteroids
with two different computer programs produced nothing within 3.3 degrees of
the nova's position brighter than mag 15 at the time of the Harvard plate.
Gaia and other surveys show that there are no other variable stars to deep
limits at the location.  The perfect PSF and the close positional match make
for proof that the image on plate B19719 is an eruption of V745 Sco.  Three
other Harvard plates are available during this eruption, with limiting
magnitudes as follows:  Plate A2606 (1897 Aug. 4.183) has B > 17.2, plate
BO842 (1897 July 3.131) has B > 10.8, and plate BO841 (1897 July 2.1912) has
B > 10.8.  From the AAVSO light curve for the 2014 eruption, the nova peaks
at B = 10.5, is at B = 12.7 at four days after the peak, and has faded to B =
18.8 by 36 days after peak.  The three limits for the 1897 plates are easily
consistent with the 2014 light-curve shape.  V745 Sco can be now seen to have
had ordinary nova eruptions in the years 1897, 1937, 1989, and 2014.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2024 CBAT
2024 March 15                    (CBET 5368)              Daniel W. E. Green