LT Del outburst (ATel)

Information about outbursts of eruptive stars, Be activity, ...
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Francois Teyssier
Posts: 1520
Joined: Fri Sep 23, 2011 1:01 pm
Location: Rouen
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LT Del outburst (ATel)

Post by Francois Teyssier »

A new alert on LT Del, a poorly observed symbiotic

Mag V = 12,4 so a pretty nice target for Alpy, LISA, DADOS-200, but not impossible at higher resolution
We have only one Spectrum in the base http://www.astrosurf.com/aras/Aras_Data ... /LTDel.htm
obtained by Joan Guarro
asdb_ltdel_20151128_758.png
asdb_ltdel_20151128_758.png (18.56 KiB) Viewed 4763 times




Send spectra to francoismathieu.teyssier at bbox.fr


François





Title: After 23 years the yellow symbiotic star LT Del is again in
outburst
Author: U. Munari (INAF Padova), P. Ochner (Univ. Padova), S. Dallaporta
and R. Belligoli (ANS Collaboration)
Queries: ulisse.munari@oapd.inaf.it
Posted: 9 May 2017; 11:06 UT
Subjects:Optical, Cataclysmic Variable, Variables

The ANS Collaboration photometric and spectroscopic monitoring of
symbiotic stars has detected LT Del (= Hen 2-467 = PK 063-12.1 = StHa 179)

in outburst. This is the first recorded outburst since the last one of

1994-1995, which was discovered by Passuello et al. (1994, IAUC 6065)
and
described by Arkhipova et al. (1995a, ALett 21, 339; 1995b, ALett 21,

391).

LT Del is steeply rising in brightness. Last ANS photometric observation

on UT May 6.005 found it at U=12.65, B=13.278, V=12.407, R=11.705 and
I=11.135 (+/- 0.006 in BVRI, 0.01 in U), which is almost as bright as the

peak of the 1994-1995 event. The current outburst unfolded in phase with

the egress of the WD from superior conjunction with the G6III giant
companion, a geometrical arrangement that may be responsible for the
particularly steep rise in brightness, which amounts to an average of 0.02

mag per day. All colors turned bluer, with the B-V rising to +0.87 from
an
average quiescence value (for the same orbital phase) of +1.45.

A spectrum of LT Del in outburst has been obtained on UT May 8.1 with
the Asiago 1.22m telescope (range 3200-7900 Ang, dispersion 2.31 Ang/pix).

A strong blue continuum now veils the G6III continuum features, and the

Balmer continuum is in strong emission. The outstanding emission lines

are characterized by high ionization conditions, with HeII 4686 being

slightly stronger than Hbeta (10.11 vs 9.71x10(-13) erg cm-2 s-1) and
prominent lines being OIII 3444 and 3429, OIV 3411, [NeV] 3345 and 3427
Ang.
The flux ratio of Balmer lines Ha:Hb:Hg:Hd is 3.53:1.00:0.46:0.36 consistent

with low reddening and low self absorption. The weakness of HeI emission

lines compared to those of HeII suggests density bounded conditions. No

significant nebular lines are present other than [NeV].
Peter Somogyi
Posts: 420
Joined: Sun Jul 13, 2014 8:56 am

Re: LT Del outburst (ATel)

Post by Peter Somogyi »

Fresh result from yesterday sunrise:

LT Del, 2017.05.11.078
3 x 20 min + 300/1200 Newton + Lhires III + 600/mm + ATIK 428 EXm + 35 micron slit, R~2700

H-alpha just getting resolved - even visually getting nicely separated on the raw image:
ltdel_20170511_ha.png
ltdel_20170511_ha.png (3.88 KiB) Viewed 4734 times
The left peak was decreasing a very little from exposure 1 to 3.

However, there was not much else on this coverage, and the usual He I lines (6678, 7065) remain thin:
ltdel_20170511_full.png
ltdel_20170511_full.png (4.28 KiB) Viewed 4734 times
Cheers,
Peter
Francisco Campos
Posts: 88
Joined: Sun Nov 29, 2015 10:13 pm

Re: LT Del outburst (ATel)

Post by Francisco Campos »

Hi,

a fresh spectrum from the last night, with full Moon and sparse clouds, but still profitable. Comparing this spectrum with Joan's one, looks like that LT Del continues in altered state, showing intense He I and He II emission lines.
_ltdel_20170610_014_FPC.png
_ltdel_20170610_014_FPC.png (8.19 KiB) Viewed 4635 times
Greetings
Fran
Francisco Campos
Posts: 88
Joined: Sun Nov 29, 2015 10:13 pm

Re: LT Del outburst (ATel)

Post by Francisco Campos »

Hello,

LT Del continues in outburst and the last spectrum I took last night shows a strong intensity increment in the Balmer bands. He I at 5876 A is also stronger but He I (6678A) and He II (4686 A) remain practically unchanged.

Interesting...
ltdel_ 20170722_946_FPC.png
ltdel_ 20170722_946_FPC amp.png
ltdel_ 20170722_946_FPC amp.png (22.77 KiB) Viewed 4539 times
Greetings
Fran
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