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Major Flare-like Outburst of LMC V2434
Detected by W. Liller
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W. Liller has reported the following major outburst of LMC V2434,
a M2eIII star, which is also known as a supersoft X-ray source,
2E IPC5843-5. The object is also detected by the ROSAT X-ray satellite
many times.
The present outburst may be some kind of a major outburst of a
supersoft X-ray source, or a some kind of nova explosion, or symbiotic
outburst? X-ray outburst? Follow-up observation at all wavelengths
are very strongly and urgently requested.
The object is identified with:
GSC9166.775 052401.63 -710935.5 (2000.0) 12.61 6
USNO0150.03033259 052401.638 -710936.05 (2000.0) 11.0 13.4
2MASS 052401.570 -710934.56 (2000.0) 8.888 8.258 7.956
052401.5 -710937 (2000.0) LMCV2434 SR: 12.90 - - - - M2eIII B72
052401.3 -710922 (2000.0) 2E_IPC5843-5 ultrasoft-X
052356.1 -710940 (2000.0) 1WGAJ0523.9-7109 0.1660 2.40 0.96 1.17 0.36 obs=1993.171
052354.3 -710955 (2000.0) 1RXPJ052354-7109.9 0.3730 -0.03 -0.31
052356.4 -711010 (2000.0) 2RXP_J052356.4-711011 0.1571P -0.12 -0.12 900620
052359.1 -711003 (2000.0) 2RXP_J052359.2-711004 0.1638P -0.20 -0.07 930620
052359.8 -711004 (2000.0) 1RXPJ052359-7110.0 0.1630 -0.20 -0.04
052402.5 -710955 (2000.0) 1RXS_J052402.6-710956 0.328 -0.12 0.25
052404.9 -711009 (2000.0) 1WGAJ0524.0-7110 0.0883 2.67 0.67 1.55 0.24 obs=1993.097
052404.8 -711017 (2000.0) 2RXP_J052404.8-711018 0.1134P -0.25 -0.11 930407
052406.3 -711023 (2000.0) 1RXPJ052406-7110.4 0.1120 -0.25 -0.17
Liller's original message:
---
On a pair of Kodak Tech Pan 25 films taken through an orange filter
(Wratten 22) with a 20cm f1/5 Schmidt camera at UT June 6.9566 and June
6.9594, 2001, the star GSC 7166 755, normally near magnitude 12.6, appeared
at magnitude 9.8. On May 31.959, the star was at or very near its
quiescent brightness. The star's GSC position (2000): R.A. = 5h 24m 01.6s,
Dec. = -71d 09' 35.6".
Tonight looks hopeful and I will try my best to get a low dispersion CCD
spectrogram. Any info from Southern Hemisphere observers would be very,
very welcome.
---
W. Liller has reported the following information. The object has
quickly faded!! If the spectroscopic classification of M3eIII (in GCVS)
is correct, the phenomenon may not be a flare star event, but the
validity of the classification needs to be more closely examined.
If it is an X-ray nova like V4641 Sgr, subsequent events may be expected.
Please keep a close eye on this object.
Liller's message:
---
Tonight at UT June 7.9670, 2001, I measured the magnitude of GSC 9166 755
with a broadband V system. I get V(bb) = 12.73. The star which I reported
was at magnitude 9.8 last night has returned to its quiescent state !
I've double-checked the pair of films showing the star as bright. The
exposures were 1.5 and 2.5 minute with mid-exposure differing by 4.0
minutes. Without any question, the images are real. On the first,
shorter exposure, the star seems slightly brighter -- perhaps by 0.2 - 0.3
mags -- which suggests to me that GSC is probably a flare star.
Alternatively, it could be an extremely short duration SS Cyg type or a
super-fast nova. It could even be an errant (and nearby) asteroid, rotating
rapidly but not moving so fast that in four minutes it shows motion.
(Focal scale 670"/mm).
Tonight it is too faint for me to obtain a spectrogram. Maybe someone else
can.
---
According to ApJS 39, 389 (1979), the star is listed as B72, a foreground
LPV variable = Case 48-8. Such a short-term flare and the strong X-ray
emission is unusual for a simple LPV star. Apparently needs closer
examination of all materials. Please observe the star as frequently as
possible!
LMC V2434 is located at 05h 24m 01s.63 -71o 09' 35".5 (J2000.0)
We have been undertaking on photometric campaigns on several super-
outbursting dwarf novae and peculiar variable stars. News and call for
observations on these objects will be issued on our regular weekly
"News from VSNET" bulletins. Those who immediately need information
should make an access to the VSNET website, and click on VSNET campaign
list.
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