SCOPERTE DUE SUPERNOVAE IN TRE GIORNI ALL’OSSERVATORIO DI MONTARRENTI: SN2014ac in NGC5838 e SN2014ah in CGCG68-91

Le attività di survey per la ricerca di oggetti transienti extragalattici del team dell’Osservatorio Astronomico Provinciale di Montarrenti (SI) composto da Simone Leonini, Massimo Conti, Giacomo Guerrini, Paolo Rosi e Luz Marina Tinjaca Ramirez, hanno portato ad una duplice scoperta di supernovae  in tre giorni.

Nella notte tra il 9 ed 10 marzo, il telescopio Ritchey-Chretien (D=0.53m - f/8.7) dell’osservatorio senese ha ripreso la galassia NGC5837, candidata ad accogliere eventi esplosivi. La spirale face-on, localizzata nella costellazione di Bootes, brilla di Mag. 13.7 a circa 375 milioni di anni luce di distanza. I controlli effettuati hanno mostrato la presenza di un ospite di Mag. +16.56CR +/-0.16 (USNO B1) a 8arcsec ovest e 10arcsec sud dal nucleo della galassia.
Nessuna sorgente di apparenza stellare era presente in quella posizione nelle nostre immagini passate, inclusa una ripresa la settimana precedente.
Individuato il transiente e stabilito che poteva trattarsi di un nuovo oggetto extragalattico, abbiamo contattato gli astronomi dell’INAF-Osservatorio Astronomico di Padova che, a poco più di due ore dalla nostra “detection”, hanno potuto caratterizzare la supernova attraverso il telescopio “Copernico” da 1.82m di Cima Ekar, classificandola di tipo Ia, pochi giorni dopo il suo massimo di luminosità.

In modo indipendente, anche gli astronomi della Public ESO Spectroscopic Survey for Transient Objects (PESSTO) dall'osservatorio di La Silla (Chile), confermavano con il New Technology Telescope (D=3.58m) natura e tipologia di supernova (ATel. 5970).

La notte seguente, il telescopio ed i controllori del Montarrenti Observatory Supernovae Search erano ancora al  lavoro. Un oggetto molto luminoso (Mag. +15.38CR +/-0.17 – USNO B1), dalle “curiose” coordinate galattiche (AR 11h55m30s.83; DEC. +11°55’26”.3), veniva individuato nell’alone della piccola galassia lenticolare CGCG68-91 (PGC037426), posta nel campo di NGC3968, oggetto principale della nostra ricerca. La sorgente, posta nella costellazione del Leone alla distanza di circa 290 milioni di anni luce, veniva subito identificata come probabile fenomeno esplosivo, non presente nelle nostre immagini “master”.

Anche in questo caso gli astronomi di Padova, con l'ausilio del telescopio “Galileo” da 1.22m di Asiago, hanno potuto classificare l’oggetto dopo poche ore dalla nostra segnalazione come supernova di tipo Ia, circa una settimana prima del suo massimo di luminosità.
Lo stesso oggetto, denominato PS1-14uw, veniva anche identificato e caratterizzato come possibile supernova dal programma di ricerca del PS1 Science Consortium operante con il telescopio Pan-STARRS1 dal Mount Haleakala (Hawaii).
 
Le circolari elettroniche dell’International Astronomical Union CBET 3830 e 3835 designavano ufficialmente le supernovae rispettivamente SN2014ac e SN2014ah aprendo la “stagione di caccia” 2014 dell’Italian Supernovae Search Project.

Simone Leonini

SN 2014ac in NGC5838

SN 2014ah in CGC G68-91

Telegrammi della scoperta da parte del CBAT

Electronic Telegram No. 3830
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director: Daniel W. E. Green; 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

SUPERNOVA 2014ac IN NGC 5837 = PSN J15044009+1237540
Simone Leonini, Siena, Italy, reports the discovery of an apparent
supernova (mag about 16.6) by G. Guerrini, M. Conti, P. Rosi, L. M. Tinjaca
Ramirez, and himself on two unfiltered CCD images (limiting mag about 19.0)
taken on Mar. 9.993 UT at the Montarrenti Observatory in the course of an
automatic survey of the Italian Supernovae Search Project using a 0.53-m
f/8.7 Ritchey-Chretien telescope (+ Apogee Alta U47 CCD camera). The new object
is located at R.A. = 15h04m40s.09 +/- 0s.23, Decl. = +12d37'54".0 +/- 0".2
(equinox 2000.0), which is 8" west and 10" south of the nucleus of the
galaxy NGC 5837. No stellar source is visible at this position on Palomar Sky
Survey infrared, red, and blue plates (1997 July 8, F plate; 1991 May 15, J plate;
and 1991 May 15, N plate; limiting mag 19.5). The discovery image is posted
at URL http://www.astrofilisenesi.it/public/Sne/Uploads/PSN_NGC5837.jpg.
The variable was designated PSN J15044009+1237540 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2014ac based on the
spectroscopic confirmation reported below. Additional CCD magnitudes for
2014ac: 2014 Feb. 24, [18.7 (Leonini et al.); Mar. 3, [17.0 (Leonini et
al.); Mar. 13.008, 16.7 (Gianluca Masi, Francesca Nocentini, and Patrick Schmeer;
remotely using a 43-cm f/6.8 corrected Dall-Kirkham robotic telescope near
Ceccano, Italy; position end figures 40s.08, 54".0); 13.028, V = 17.3 (M.
Martignoni, Magnago, Italy; 0.25-m f/10 Schmidt-Cassegrain reflector;
position end figures 40s.09, 54".3); 13.069, 17.7 (Federica Luppi and Luca Buzzi,
Varese, Italy; 0.60-m f/4.6 reflector; position end figures 40s.08, 54".2;
image posted at website URL http://www.astrogeo.va.it/pub/TOCP/PSN_N5837.jpg).

L. Tomasella, S. Benetti, E. Cappellaro, A. Pastorello, P. Ochner, N.
Elias-Rosa, and M. Turatto, Osservatorio Astronomico di Padova, Istituto
Nazionale di Astrofisica; and S. Ciroi, Dipartimento di Fisica e Astronomia,
Universita' di Padova, report that a noisy optical spectrogram (range
340-820 nm; resolution 1.3 nm) of PSN J15044009+1237540 = SN 2014ac, obtained on
Mar. 10.98 UT with the Asiago 1.82-m Copernico Telescope (+ AFOSC), shows it to
be a type-Ia supernova. Adopting for the host galaxy, NGC 5837, a redshift z
0.0287 (Fisher et al. 1995, Ap.J. Suppl. 100, 69; via NED), a good match is
found with several type-Ia supernovae at a few days after maximum. The
expansion velocity deduced from the Si II 635.5-nm absorption is about 10500
km/s. The Asiago classification spectra are posted at website URL
http://sngroup.oapd.inaf.it; classification was made via GELATO (Harutyunyan
et al. 2008, A.Ap. 488, 383) and SNID (Blondin and Tonry 2007, Ap.J. 666,
1024).

N. Walton, M. Fraser, N. Blagorodnova, Institute of Astronomy; S.
Taubenberger, Max-Planck-Institut fuer Astrophysik, Garching; M. Dennefeld,

Institut Astrophysique de Paris; S. Benetti and A. Pastorello, Osservatorio
Astronomico di Padova, Istituto Nazionale di Astrofisica (INAF); C. Inserra,
S. Smartt, K. Smith, and D. Young, Queen's University, Belfast; M. Sullivan,
University of Southampton; S. Valenti, Las Cumbres Observatory Global
Telescope; O. Yaron and A. Gal-Yam, Weizmann Institute for Science; C.
Knapic, R. Smareglia, and M. Molinaro, Trieste Astronomical Observatory, INAF; and
I. Manulis, Weizmann Institute for Science, on behalf of the Public European
Southern Observatory (ESO) Spectroscopic Survey for Transient Objects
(PESSTO; see website URL http://www.pessto.org), report that a spectrogram was taken
of PSN J15044009+1237540 = SN 2014ac on the ESO's New Technology Telescope at
La Silla on Mar. 10, using EFOSC2 and Grism 13 (398.5-931.5 nm; 1.8-nm
resolution). Cross-correlation of the spectrum with a library of template
spectra using SNID (Blondin and Tonry 2007, Ap.J. 666, 1024) gives a best
match to several normal type-Ia supernovae at the redshift of NGC 5837 (z
0.029) and around maximum light.

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

(C) Copyright 2014 CBAT
2014 March 19 (CBET 3830) Daniel W. E. Green

Electronic Telegram No. 3835
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director: Daniel W. E. Green; 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

SUPERNOVA 2014ah IN PGC 37426 = PSN J11553083+1155263
Simone Leonini, Siena, Italy, reports the discovery of an apparent
supernova (mag about 15.4) by himself with M. Conti, G. Guerrini, P. Rosi,
and L. M. Tinjaca Ramirez on two unfiltered CCD images (limiting mag about 18.6)
taken on Mar. 12.002 UT in the course of the Italian Supernovae Search
Project using a 0.53-m f/8.7 Ritchey-Chretien telescope (+ Apogee Alta U47 camera)
at their Montarrenti Observatory. The new object is located at R.A. 11h55m30s.83
+/- 0".2, Decl. = +11d55'26".3 +/- 0".2 (equinox 2000.0), which
is 4" east of the nucleus of the galaxy PGC 37426 = MCG +02-30-44. No
stellar source is visible at this position on their previous image taken on Mar. 3
(limiting mag about 19.0). The discovery image is posted at website URL
http://www.astrofilisenesi.it/public/Sne/Uploads/PSN_PGC037426.jpg. The
variable was designated PSN J11553083+1155263 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2014ah based on the
spectroscopic confirmation reported below. Additional CCD magnitudes for
2014ah: Mar. 12.993, 16.3 (Gianluca Masi, Francesca Nocentini, and Patrick
Schmeer; remotely using a 43-cm telescope near Ceccano, Italy; position end
figures 30s.87, 26".3); 12.995, V = 16.5 (Massimiliano Martignoni, Magnago,
Italy; 0.25-m Schmidt-Cassegrain reflector; position end figures 30s.85,
24".9); 14.120, 17.1 (Federica Luppi and Luca Buzzi, Varese, Italy; position
end figures 30s.84, 26".1; reference stars from CMC-14 catalogue; image
posted at URL http://www.astrogeo.va.it/pub/TOCP/PSN_P37426.jpg); 15.084,
16.1 (S. Foglia and G. Galli, Pogliano Milanese, Italy; 0.28-m f/6.8 reflector +
ST8XME camera; position end figures 30s.89, 26".3; UCAC-4 reference stars).

P. Ochner, S. Benetti, L. Tomasella, E. Cappellaro, A. Pastorello, N.
Elias-Rosa, and M. Turatto, Osservatorio Astronomico di Padova, Istituto
Nazionale di Astrofisica, report that an optical spectrogram (range 335-790
nm; resolution 0.9 nm) of PSN J11553083+1155263 = SN 2014ah, obtained on
Mar. 10.98 UT with the Asiago 1.22-m Galileo Telescope (+ Boller & Chivens
spectrograph), shows it to be a type-Ia supernova. Adopting for the host
galaxy (PGC 37426 = MCG +02-30-44 = CGCG 68-91) a radial velocity of 6303
km/s (SDSS Data Release 4, via NED), a good match is found with the spectrum
of SN 2003du (Stanishev et al. 2007, A.Ap. 469, 645) about a week before
maximum light. The expansion velocity, deduced from the Si II 635.5-nm
absorption, is about 10400 km/s. The Asiago classification spectra are
posted at website URL http://sngroup.oapd.inaf.it; classification was made
via GELATO (Harutyunyan et al. 2008, A.Ap. 488, 383) and SNID (Blondin and
Tonry 2007, Ap.J. 666, 1024).

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

(C) Copyright 2014 CBAT
2014 March 22 (CBET 3835) Daniel W. E. Green