Nova Ophiuchi 2008
Lo scorso 25 maggio gli astrofili giapponesi Nishiyama,
Kabashima, Nishimura e Haseda hanno indipendentemente scoperto una luminosa
stella nova nella costellazione di Ofiuco, nella posizione R.A. = 17h39m50s.94,
Decl. = -23o50'01".0. La stella, al momento della scoperta, era di 10^
magnitudine; di seguito riportiamo le IAUC che ne comunicano la scoperta (8947)
e lo spettro (8948).
Uno spettro della nova è stato ottenuto anche da Riccardo
Mancini, dell'Associazione Astronomica
Isaac Newton di Tavolaia, lo scorso 2 giugno, dal quale risulta molto
evidente la riga in emissione dell'Halpha a 6563 nanometri, caratteristica delle
stelle novae. Anche altre porzioni dello spettro (nell'intervallo tra circa 4800
e 5300 A) sembrano avere righe in emissione, non risolte però causa la bassa
risoluzione utilizzata. La riga Halpha sembra infine anche molto allargata,
indice di elevata velocità (alcune centinaia di Km al secondo) dei gas intorno
alla stella.
Complimenti all'amico Mancini per l'ottimo lavoro
eseguito.
Circolare IAUC8947
NOVA OPHIUCHI 2008
The following Japanese observers have reported independent
discoveries on May 25 of an apparent tenth-magnitude nova: K.
Nishiyama (Kurume, Fukuoka-ken) and F. Kabashima (Miyaki-cho, Saga-
ken) on 60-s frames taken with a 105-mm f/5.6 lens (communicated
by S. Nakano, Sumoto, Japan); H. Nishimura (Kakegawa, Shizuoka-ken;
via Nakano); and K. Haseda (Toyohashi, Aichi; via H. Yamaoka,
Kyushu University). Nishimura and Haseda used 120-mm-f.l. camera
lenses. Other confirming reports were received after word of the
object was posted on the Central Bureau's unconfirmed-objects webpage.
CCD position measured for the apparent nova by Nishiyama and
Kabashima (0.40-m f/9.8 reflector) on May 25.750 UT: R.A. =
17h39m50s.93, Decl. = -23o50'00".9 (equinox 2000.0). Other
measured position end figures: Nishimura, 51s, 49'.1; Haseda, 47s,
50'28" (resolution 14"/pixel); S. Dvorak (near Orlando, FL, U.S.A.,
0.25-m telescope on May 26.30), 50s.90, 50'00".6; C. Jacques and E.
Pimentel (Belo Horizonte, Brazil, 0.25-m reflector remotely near
Mayhill, NM, U.S.A., on May 26.43), 50s.92, 50'01".1. E. Guido and
G. Sostero (Remanzacco, Italy, 0.25-m reflector, remotely near
Mayhill, NM), 50s.95, 50'00".9 (image posted at
http://tinyurl.com/
3v9cje). Magnitudes for the apparent nova (unfiltered CCD unless
otherwise noted): 1985 (no date), [19.5 (Jacques and Pimentel, red
Digitized Sky Survey); 1991 Aug. 11, [20: (Guido and Sostero, U.K.
Schmidt Telescope red plate); 2008 Mar. 8.82, Apr. 4.77, and May
14.70, [11.5 (Haseda); Apr. 27.094, [16.0 (H. Mikuz, Crni Vrh
Observatory; red magnitude); May 14.759, [12 (Nishimura); 19.752
and 20.694, [12.4 (Nishiyama and Kabashima); 20.745, [10 (Nishimura);
25.69, 10.3 (Haseda); 25.693 and 25.695, 10.2 (Nishiyama and
Kabashima); 25.706, 10.2 (Nishimura); 25.750, 10.2 (Nishiyama and
Kabashima); 26.30, V = 10.29, B = 11.72 (Dvorak); 26.31, B = 11.42,
V = 10.45, R = 9.81 (Guido and Sostero); 26.43, 10.4 (Jacques and
Pimentel). Visual magnitude estimates by A. Jones (Nelson, New
Zealand): May 26.40, 10.2; 26.45, 10.1.
(C) Copyright 2008 CBAT
2008 May 26 (8947) Daniel W. E. Green
Circolare IAUC8948
NOVA OPHIUCHI 2008
K. Ayani and N. Murakami, Bisei Astronomical Observatory (BAO),
write that low-resolution spectra (range 400-800 nm; resolution 0.5
nm at H_alpha) of the apparent nova announced on IAUC 8947,
obtained with the BAO 1.01-m telescope on May 26.7 UT, confirms
that the object is a nova. They show H_alpha emission (FWHM about
600 km/s) with a P-Cyg profile, its absorption minimum being blue-
shifted by 730 km/s with respect to the emission peak. H_beta and
Fe II (multiplet 42) lines also have P-Cyg profiles, although the
absorption component dominates on lines of shorter wavelength.
Further to IAUC 8947, S. Nakano reports that co-discoverers
K. Nishiyama and F. Kabashima obtained additional unfiltered CCD
frames with a 0.40-m reflector on May 26.562 UT, yielding mag 9.8
for the nova and position R.A. = 17h39m50s.94, Decl. = -23o50'01".0
(equinox 2000.0). Nakano also forwards an unfiltered CCD
observation by K. Kadota (Ageo, Japan, 0.25-m reflector) on May
26.609 that yielded mag 9.9 and a measured position identical to
that above.
Visual magnitude estimate of N Oph 2008 by W. Vollmann, Vienna,
Austria: May 26.969 UT, 10.4. Photoelectric V magnitudes by L.
Elenin, Lubertsy, Russia, contributed by E. Waagen, AAVSO: May
26.457, 10.30; 27.380, 10.14.
(C) Copyright 2008 CBAT
2008 May 27 (8948) Daniel W. E. Green
L'analisi spettrale della Nova Ophiuchi 2008 da parte di Riccardo
Mancini
