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).