[vsnet-outburst 17110] ASASSN-14du (ATEL)

[Taichi Kato]

ASASSN-14du (ATEL)

   So it is a dwarf nova in outburst, as expected.

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ATEL #6311							     ATEL #6311

Title:	ASASSN-14du: optical spectroscopy indicates z=0
Author:	S. Schulze (PUC, MAS), D. Malesani (DARK/NBI), J. P. U. Fynbo
		(DARK/NBI), B. Milvang-Jensen (DARK/NBI), D. Xu (DARK/NBI), Z. Cano
		(Univ. Iceland), P. Jakobsson (Univ. Iceland), Y. Martinez-Osorio
		(Uppsala University)
Queries:	malesani at dark-cosmology.dk
Posted:	15 Jul 2014; 13:50 UT
Subjects:Optical, Request for Observations, Cataclysmic Variable,
		Nova, Star, Transient, Variables

We observed ASASSN-14du (Holoien et al., ATel #6308) with the 2.54-m Nordic
Optical Telescope (NOT) equipped with ALFOSC on 2014 July 14. We obtained
a single 30-s exposure in the SDSS r band starting at 20:59:54 UT. The
source detected by Holoien et al. (ATel #6308) is clearly detected. We
measure r(AB) = 16.76 +- 0.04 mag (calibrated against several SDSS stars).

We also obtained an optical low-resolution spectrum, starting at 21:24:45
UT. We used grism #4 covering the wavelength range from 3750 to 9000 AA,
though wavelengths above 7000 AA are affected by fringing. The observation
consisted of two individual spectra with a total exposure time of 2x800
s. The flux calibrated spectrum shows a blue continuum which can be fit
with a power-law F_nu propto nu^0.7 in the range 4000-7000 AA. We identify
several broad Balmer absorption lines at z = 0, starting from Hbeta and
up to H9, where our spectrum is cut, as well as He I 4471. No Halpha is
present. The FWHM of Hbeta and Hgamma is around 3200 km/s. No emission
features are visible in our spectrum. 

Our data indicate a transient in the Galaxy, or in its immediate proximity,
and can exclude a super-luminous SN. We encourage further observations
to monitor the evolution of this source.