TITLE:   GCN CIRCULAR
NUMBER:  25618
SUBJECT: LIGO/Virgo S190901ap : GRAWITA spectroscopic observation of candidate ZTFabvizsw 
DATE:    19/09/02 23:07:12 GMT
FROM:    Lina Tomasella at INAF,Padova  <lina.tomasella@inaf.it>

I. Salmaso, L. Tomasella, S. Benetti (INAF Padova), P. D’Avanzo (INAF Brera), E. Cappellaro (INAF Padova), M.T. Botticella (INAF Napoli), R. Martone (Ferrara University), A. Rossi (INAF Bologna), E. Brocato (INAF Teramo), on behalf of GRAWITA report:


We used the Asiago 1.82m Copernico telescope equipped with the AFOSC spectrograph and camera to observe one of the candidate transient found by the Zwicky Transient Facility (ZTFabvizsw; Kool et al. GCN 25616) localized in the region of the gravitational wave trigger S190901ap (LVC et al. GCN 25606, GCN 25614). 

Optical images were obtained with the uBVgriz filters. Two optical spectra (1800s, 2400s exposure time) were obtained using the grism gr4 (wavelength range ~ 340-820 nm, resolution 1.4 nm). The spectrum is typical of a Galactic K or M star. Thus it could be a Galactic variable, although a rarer case of stellar microlensing event could not be excluded (see Benetti et al. 1995, Astron. Astrophys. Letters, 294, L37).