(Hodgkin et al. 2013)
shows another brightening event in 2018,
with a rise amplitude of >2.5mag on a time scale of <33 days (the peak is not measured).
From r < 15.8 mag, the source subsequently declined to 19-19.5 mag in <4 months.
The current 2019 outburst, designated Gaia 19fct, reaches G < 15.1
(the peak is not yet measured) with the brightening by >4 mag to date, taking <75 days.
The optical spectrum, obtained on 29 November, 2019 (UT) with HIRES (Vogt, 1994)
and the W.M. Keck Observatory's Keck I Telescope, is absorption-dominated with no signature of the
permitted- or forbidden-line emission that was present earlier in both the faint state
and in the 2015 outburst state. Instead, the high resolution (R=37,000) spectrum
is characterized purely by absorption from broadened metal lines, with widths of about 70 km/s.
The spectral type is in the F0-F5 range if a dwarf/giant and F5-G0 if a supergiant.
BaII at 6142 A and 6497 A, an indicator of a low surface gravity atmosphere,
and LiI at 6707 A, a signature of stellar youth, are both present.
There are also ``wind lines" including MgIb, NaD, and KI 7699,
as well as clear P Cygni profiles in Halpha and in the CaII triplet.
The terminal velocity of the blueshifted absorption in these lines
is currently only about -120 km/s.
While the two previously recorded brightening events in iPTF 15afq were consistent
with moderate scale and short-lived EX Lup type events, the ongoing outburst is much larger, though obviously as-yet unknown in terms of total amplitude or duration.
The nature of the absorption spectrum in outburst may indicate
a more dramatic accretion event such as an FU Ori outburst.
Multi-color photometric follow-up over the next several months is encouraged.
