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GCN Circular 20902

LIGO/Virgo G277583: Asiago spectroscopic classification of ATLAS17byo and ATLAS17cgg
2017-03-18T10:01:28Z (7 years ago)
Daniele Malesani at DARK/NBI <>
L. Tomasella, E. Cappellaro, S. Benetti (INAF OAPd), D. Malesani 
(DARK/NBI, Denmark), G. Greco (Urbino University/INFN Firenze), A. 
Rossi, E. Palazzi (INAF-IASF Bo), M. Branchesi (Urbino University/INFN 
Firenze), L. Amati (INAF-IASF Bo), L. A. Antonelli, S. Ascenzi 
(INAF-OAR), M.T. Botticella (INAF-OAC), S. Campana, S. Covino, P. 
D'Avanzo (INAF-OAB), V. D'Elia (INAF-ASDC), F. Getman, A. Grado, L. 
Limatola (INAF-OAC), M. Lisi (INAF-OAR), A. Melandri (INAF-OAB), L. 
Nicastro (INAF-IASF Bo), E. Pian (SNS-Pisa), S. Piranomonte, L. Pulone 
(INAF-OAR), G. Stratta (Urbino University/INFN Firenze), G. Tagliaferri 
(INAF-OAB), V. Testa (INAF-OAR), S. Yang (INAF-OAPD), E. Brocato 
(INAF-OAR) on behalf of GRAvitational Wave Inaf TeAm (GRAWITA) report:

We report spectroscopic observations of the ATLAS transients ATLAS17byo 
and ATLAS17cgg (Smartt et al., LVC Circ. 20881), discovered in the 
skymap (cWB_plus_LIB.fits) of G277583 (LVC Circ. 20860), with event time 
2017-03-13 22:40:09.593 UT (MJD 57825.945).

The observations were performed with the Asiago 1.82 m Copernico 
Telescope equipped with AFOSC (range 340-820 nm; resolution 1.4 nm).

Name        RA           DEC        z      Host Galaxy
ATLAS17byo  16:33:19.87 +23:43:52.4 0.033  SDSS J163319.94+234356.4
ATLAS17cgg  08:03:55.23 +26:31:12.3 0.0217 IC 0491

1) ATLAS17byo was observed at MJD=57830.05 under bad sky conditions. 
However, the noisy spectrum shows that this transient is a normal type 
Ia SN, around maximum light.

2) ATLAS17cgg was observed starting from MJD=57829.88. We took 3 spectra 
showing that this transient is a young type IIn SN. The spectra display 
a blue continuum with over-imposed Balmer emission lines with composite 
profiles (FWHM ~ 1300-1700 km/s). The best match is found with SN 1998S 
(Fassia et al. 2000 MNRAS 318) before maximum. Multiband photometry was 
also collected and a preliminary analysis shows that: u = 17.66[0.014], 
g = 17.12[0.016] AB mag; B = 17.20[0.014], V = 17.13[0.018] Vega mag

Our spectral classifications are consistent with those provided by 
Blagorodnova et al. (LVC Circ. 20897).
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