The Discovery of SN 1996ae in NGC 5775.

Antonio Vagnozzi for Team S. Lucia.

The Astrometric Observatory in S. Lucia at Stroncone (Terni) was born ten years ago, thanks to Antonio Vagnozzi's passion for astronomy; he started the astronomic activity, building himself a great part of the devices with which the observatory is equipped.

As time went by, many people were involved, people who, despite their different competence, converged their knowledge towards astronomy. Now the Team is made up of ten people, aging from 20 to 70.

The Observatory, the cupola of which is 480 cm wide, is equipped with a Ritchey-Cretien 500 mm f/7.5 telescope, a 200 mm f/7.5 guide telescope, and a 250 mm f/13 Baker-Schmidt, a ST4 and a ST6 CCD cameras and four computers.

In the beginning, the Team Activity was finalized to searching and measuring asteroids: until today, 100 new asteroids were discovered, five of which were named.

In October 1994 the search for extra galactic Supernovae began. With the help of Emiliano Gregori, we chose about 900 galaxies amid spiral and irregular ones from the NGC catalogue, with magnitude until 13.5 and a declination between +65 and -25 . An archive and observation administration program, created by Gianni Bernabei, is remarkably carrying out its duties. Up until now we have archived about 600 images from the first observation, and 100 from the second, thanks to the automatic telescope aiming control program written by Vairo Risoldi.

In February 1995, with the 6165 circular from the Minor Planet Center, we received the pre-discovery for SN 1995F in Ngc 2726 galaxy. More than a year had to be waited before we could have a second chance: this time the SN could not escape from us.

The evening of May 21st, though the weather is not at its best, we (Antonio, Vincenzo and Giovanna, the only woman in the Team) start our observative session, choosing 14 galaxies: the last one is NGC5775. Shortly after midnight, when we are about to end the session, we see an image of the last galaxy on our monitor. The first doubts start to arise: in the Vickers there's no trace of that small bright dot; we check again, we take another image: it is not an asteroid, it is not a cosmic beam. The tension is rising.

We measure the magnitude: it is 16.5. We have the distance module for the galaxy: we establish a 100,000,000 l.y. distance, and the magnitude the SN should have if it were a type II: 16. The stress boosts up again. We check the circulars once more: there's NGC5575 with a SN; ours is not there. So we decide to send an e-mail message to Green: the emotion is so strong that, in the subject field, we type in "Suspect SN in NGC5577". We also send the message to Mirko Villi of the International Supernovae Network. After a few minutes the first reply from Green arrives (many others are to come. our computer clock is even saying the wrong time!): "Suspect SN in NGC5577 or in NGC5775?". We excuse ourselves straightaway: "Our galaxy is NGC5775". We wait another ten minutes: we hope for a reply from Green to come. Nothing! We calm down: it's three o'clock in the morning!

The day after everything is calm. We patiently wait, but in the evening we phone Mirko Villi: he has not received our message, his e-mail address was wrong. Anyway, from then on an incredible machine starts running.

The first confirmations are coming via Internet: John Sanford and Joe Sala from America, Nakamura from Japan, Mark Amstrong, David Strange, Terry Platt from England through Guy Hurst of "The Astronomer". No official confirmation from Green yet, only messages asking for more details. Our amateur astronomer friends Villi and Pesci tell us to be patient: there's a 3-day holiday in America!

Finally on May 27th, one week after that crucial night, when we are exhausted, the 6409 circular arrives: the SN is ours!

Today, May 29th, we received the 6410 circular: the SN 1996ae is a type II event (IIn), about 100 days after maximum; we understand it's a somehow special SN, with an unusual emission spectrum. All these things make us curious and very proud, and pay us back for the many days of wait and anxiety, which anyway we would all live once again.

Here are some images from supernova observers:

  • A.Vagnozzi, G.Piermarini, V. Russo discovery image obtained on May 21.95 U.T. with a 4 min.CCD exposure and 0.50 mt. telescope.
  • First confirmation image by John Sanford and Giuseppe (Joe) Sala, made at Anza, California, USA, made with the OCA 22" telescope and CCD Starlight Xpress, on May 24.28 UT.
  • A.Nakamura, Japan, took CCD image of NGC5775. He detected SN at reported location. He used 0.6m refl / F6 + unfiltered CCD with exposure 60 sec on May 24.6493 UT. The object is about of mag.17.