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ASASSN-18su: likely dwarf nova outburst (10.0 mag) in Hydra (ATel #11968)

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SPK
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ASASSN-18su: likely dwarf nova outburst (10.0 mag) in Hydra (ATel #11968)

ASASSN-18su (UGWZ:)
https://www.aavso.org/vsx/index.php?view=detail.top&oid=623474

"ASAS-SN Discovery of a Very Bright (g~10.1) Transient ASASSN-18su"
http://www.astronomerstelegram.org/?read=11968

12:57:51.258 -28:30:16.82 2018-08-17.71 10.1
Discovered in images obtained on 2018-08-17.71 UT at g~10.1, also detected at V~10.0 on 2018-08-17.97 UT; not detected (V>18.0) in subtracted images taken on 2018-08-14.98 UT and before.

ASASSN-18su 20180814.985 <180V ASN
ASASSN-18su 20180817.71 101g ASN
ASASSN-18su 20180817.974 100V ASN

"No previous outbursts are detected at the position of ASASSN-18su since ASAS-SN started observing this location in December 2013."

Complete ASAS-SN Sky Patrol V-band light curve:
https://asas-sn.osu.edu/light_curves/c2c8b600-d005-4cf0-b2f9-6b29824f5af2

The likely progenitor is PSO J125751.372-283015.290 (RA 12 57 51.347, DEC -28 30 15.32; g= 17.97, r= 18.08 mag).
Gaia DR2 data: G= 17.90 mag; parallax 5.5218 ± 0.1578 mas (distance 180 ± 5 pc); pmRA= -144.650, pmDE= -8.789 mas/yr.
Other designations: WISE J125751.42-283014.9, GALEX J125751.4-283015, 1WGA J1257.8-2830, ...

Probably a large amplitude (8 mag) outburst of a WZ Sge-type dwarf nova.

*** Spectroscopy, time-resolved photometry, and precise astrometry are urgently required. ***

Clear skies,
Patrick

AAX
AAX's picture
Hi friends,

Hi friends,

This object was observed visually in 2018-08-18 21:55 UT, mag = 9.8
using Tycho-2 comps with b-v <1.0

Alex!

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