[vsnet-alert 22329] ASASSN-18pe (ATEL)

[Taichi Kato]

ASASSN-18pe (ATEL)

   The presence of strong He II line may be a signature
of a massive white dwarf.

cf.
http://adsabs.harvard.edu/abs/2018arXiv180506974K

   The object already started fading according to
Kasai-san's observations.

===

ATEL #11875							     ATEL #11875

Title:	Photometry and spectroscopy of the continuing rise in brightness
		of ASASSN-18pe
Author:	U. Munari and L. Zampieri (INAF Padova), S. Moretti, A. Maitan
		and S. Tomaselli (ANS Collaboration)
Queries:	ulisse.munari at inaf.it
Posted:	20 Jul 2018; 11:19 UT
Subjects:Optical, Cataclysmic Variable, Transient

We have obtained UBVRI photometry (Landolt system) and optical 
spectroscopy of recently discovered ASASSN-18pe currently undergoing a

large amplitude outburst (Atel #11867).  Photometry was obtained on UT
July 
19.888 with the ANS Collaboration telescope 1205 (42cm) providing B=13.961,

V=13.895, R=13.801, and I=13.678, with total error budgets (including 
transformation from the instantaneous local photometric system to the 
reference Landolt equatorial standards) less than 0.01 mag in all bands.
We 
also obtain U=13.27, but with a larger uncertainty considering the sea
level 
altitude of the observing site.  This indicates a continuing (and slow)
rise 
in brightness of ASASSN-18pe, that was reported in Atel #11867 at V=14.3
two 
days earlier.  The overall color seems somewhat bluer that the SLOAN griz

values listed for quiescence in the Pan-STARRS release 1 (PS1) Survey 

Absolute optical spectrophotometry was obtained with the Asiago 1.22m 
telescope at 2.31 Ang/pix over the 3250-7950 Ang range on UT Jul 19.853.

The spectrum rises steeply toward the short wavelengths in agreement with

the blue photometric colors.  Hbeta, gamma, delta, epsilon lines stands
in 
clear absorption although with a minimal equivalent width, H9 being the

highest Hydrogen line before those further up merge into the Balmer 
continuum in absorption.  NaI 5890, 5896 doublet is also in clear 
absorption.  Only an emission component is visible in Halpha with an 
integrated flux of 6.6 (+/- 0.6) x 10(-15) erg/cm2 sec.  The strongest

emission line is HeII 4686, radiating an integrated flux of 1.34 (+/-0.11)
x 
10(-14) erg/cm2 sec, twice larger than Halpha (both lines single peaked).

No evident emission line from HeI is visible, with the possible exception
of 
a feeble 5876 Ang.  The radial velocity for all observable lines is pretty

low within the limited sensitivity of the adopted spectral dispersion.

Overall, the photometric and spectral appearances are compatible with a

CV eruption.  Worth noticing are the slow rising time (commented upon also

in Atel #11867), the unusual strength of HeII emission and the possibly
bluer colors 
compared to quiescence.