[vsnet-alert 17538] ASASSN-14ei

[Taichi Kato]

ASASSN-14ei

   Most likely it is associated with the ROSAT source.
Precursor and main outburst?  Observations are encouraged.

ASASSN-14ei 	 USNO-B1.0 0421-0026203 	ATEL 	2:55:33.3 	-47:50:42.1 	2014-07-10.37 	11.73 	SDSS 	DSS 	VIZIER 	------- 	 Unusual transient source, matches to B=17.6 star in USNO-B1. Also detected on 2014 UT July 09.36 (V~16.8), July 10.38 (V~11.9), and July 24.35 (V~12.1), and undetected (V > 17) on 2014 UT July 17.36, July 18.37, July 19.36, and before 2014 UT July 07.39.

ASASSN-14ei 20140707.39 <170V ASN
ASASSN-14ei 20140709.36 168V ASN
ASASSN-14ei 20140710.37 11.73V ASN
ASASSN-14ei 20140717.36 <170V ASN
ASASSN-14ei 20140718.37 <170V ASN
ASASSN-14ei 20140719.36 <170V ASN
ASASSN-14ei 20140724.35 121V ASN

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ATEL #6340                                                           ATEL #6340

Title:  ASAS-SN Discovery of an Unusual Outburst from USNO-B1.0 0421-0026203
Author: J. L. Prieto (Universidad Diego Portales), K. Z. Stanek, C.
                S. Kochanek, T. W.-S. Holoien, B. J. Shappee, A. B. Davis, J. Je
ncson,
                U. Basu, J. F. Beacom (Ohio State), D. Bersier (LJMU), J. Brimac
ombe
                (Coral Towers Observatory), D. Szczygiel, G. Pojmanski (Warsaw U
niversity
                Observatory)
Queries:        jose.prietok at mail.udp.cl
Posted: 24 Jul 2014; 19:20 UT
Subjects:Optical, Transient, Variables

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or
"Assassin"), using data from the double 14-cm "Cassius" telescope in Cerro
Tololo, Chile, we discovered an unusual outburst of USNO-B1.0 0421-0026203:

Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag

ASASSN-14ei  02:55:33.39   -47:50:42.0       2014-07-21.36       15.8 

ASASSN-14ei was discovered in images obtained 2014 UT July 21.36 at V~15.8
mag. We also detect the outburst in images obtained 2014 UT July 09.36
(V~16.8), July 10.38 (V~11.9), and July 24.35 (V~12.1), but we do not detect
it (V > 17) in images obtained on 2014 UT July 17.36, July 18.37, July
19.36, and before 2014 UT July 07.39. This <a href=http://www.astronomy.ohio-sta
te.edu/~assassin/followup/asassn14ei.png>figure</a>
shows the ASAS-SN light curve beginning on 2014 UT July 05.5 and spanning
20 days.  

A cross-check of the transient's ASAS-SN position in Vizier reveals that
the source of the outburst is USNO-B1.0 0421-0026203, which has an unusual
optical color (B2=17.59, R2=18.33, B2-R2=-0.79). There is also a source
detected at the position of the transient in WISE, which has a red mid-IR
color (W1=17.62 +/- 0.15, W2=16.76 +/- 0.25, W1-W2~0.9). We also note that
the ROSAT X-ray source 1RXS J025533.1-475020, located at 22 +/- 14 arcsec
from ASASSN-14ei, might be associated with the transient.  

We thank LCOGT and its staff for their continued support of ASAS-SN. For
more information about the ASAS-SN project, see the <a href=http://www.astronomy.o
hio-state.edu/~assassin/index.shtml>ASAS-SN
Homepage</a> and the list of all <a href=http://www.astronomy.ohio-state.edu/~assa
ssin/transients.html>ASAS-SN
transients</a>.