[vsnet-alert 10765] planetary nebula Lo 4: spectroscopic outburst of central star

[Howard E. Bond]

Dear colleagues:

I have just submitted the note below to the IAU Circulars. It describes a
spectroscopic outburst of the central star of the southern planetary nebula Lo
4. The star has had 3 known previous outbursts of this type; it is only known
that the outbursts last less than about 2 weeks. The cause of the outbursts is
unknown. The star is normally at 16.6 mag, but it would be very interesting to
determine whether it has brightened during the current outburst, and to continue
to follow the star for at least the next 2 weeks. High-speed photometry of its
GW Vir-type pulsations would be especially desirable.

Howard E. Bond
Space Telescope Science Institute




CENTRAL STAR OF LONGMORE 4

The hydrogen-deficient central star of the planetary nebula Lo 4
(J2000: 10 05 45.7 -44 21 32) normally has a PG 1159-type
absorption spectrum, with the O VI 3811-3834 doublet in
emission. On three past occasions (one in 1992, two in 2006;
H.E. Bond, 2008, ASP Conf Series 391, p. 129) the spectrum has
changed temporarily to an emission-line [WCE] type, with strong
emission at the C IV+He II complex near 4659-4686 A and O VI
5291. A spectrum obtained on 2008 Nov 30.27 with the SMARTS 1.5m
telescope at Cerro Tololo by M. Hernandez and F. Walter shows
that a new emission-line outburst is underway. Spectroscopic and
photometric monitoring, including high-speed photometry of the
star's GW Vir-type pulsations, is desirable throughout the
duration of the current event.