[vsnet-alert 22958] MAXI J1348-630

[Taichi Kato]

MAXI J1348-630

   Optical counterpart at 16.2 mag.  Time-resolved
photometry is encouraged.

===

ATEL #12430                                                          ATEL #12430

Title:  Optical counterpart of MAXI J1348-630
Author: D. Denisenko (Education Center on Donskaya, Moscow; SAI MSU),
                I. Denisenko, M. Evtushenko, D. Fernandez OrtiZ, I. Kotelnikov, 
M.
                Komarov, I. Larin, I. Spasic, D. Vdovin (Education Center on Don
skaya,
                Moscow)
Queries:        d.v.denisenko at gmail.com
Posted: 26 Jan 2019; 17:33 UT
Subjects:Optical, X-ray, Nova, Transient, Variables

We have observed error box of new X-ray transient MAXI J1348-630 (F. Yatabe
et al., ATel #12425) with iTelescope.Net T31 instrument (0.51-m f/6.8 reflector
+ CCD) in Siding Spring, Australia. A series of unfiltered 60-sec exposures
was taken at 16:09-16:14 UT on 2019 Jan. 26 with the T31 field of view
(0.93x0.93 degree) covering the entire 90% confidence level uncertainty
area. The combined images were compared to the scanned DSS Red plates taken
on 1994-03-10, 1994-08-12, 1997-03-31 and 1999-02-16. The only object that
stands out in the inspected field is the new optical transient at the following
position (J2000.0): R.A. = 13 48 12.88, Decl. = -63 16 28.4. The magnitude
of the object (unfiltered with the red zero point) at 2019-01-26.675 UT
is 16.18 measured using 2MASS J13480967-6315325 as reference star with
V=14.43 in APASS DR9 (A. Henden et al., 2016).  

T31 discovery image is posted at http://scan.sai.msu.ru/~denis/J1348-630-T31-201
90126.jpg

The new OT is within Swift error circle (V. D'Elia et al., GCN #23796),
82 arc sec from its center. There is no known variable star at this position
in AAVSO VSX and GCVS. The nearest star in Gaia DR2 is 1.6 arc sec away
with Gmag=21.13. Precise astrometry, spectroscopy and photometric time
series of the new OT are strongly encouraged. 

===

ATEL #12434                                                          ATEL #12434

Title:  MAXI J1348-630: Swift XRT localization, possible periodicity
Author: J. A. Kennea (PSU) and H. Negoro (Nihon U)
Queries:        jak51 at psu.edu
Posted: 27 Jan 2019; 00:49 UT
Subjects:X-ray, Transient

Following the reporting of a new X-ray transient, MAXI J1348-630 (Yatabe
et al., ATEL #12425), and it's subsequent detection by Swift's Burst Alert
Monitor (BAT), as reported by D'Elia et al (GCN #23795 and #23796), Swift
performed a 1ks Target of Opportunity observation of this transient in
Photon Counting mode, in order to accurately localize it. Analysis of the
XRT data find a bright uncatalogued X-ray source the following location:
RA/Dec(J2000) = 207.05305, -63.27411, 

RA(J2000) = 13h 48m 12.73s,  

Dec(J2000) = -63d 16m 26.8s, 

with an error radius of 1.7 arc-seconds (90% confidence), this lies 1.9
arc-seconds from the optical transient reported by Denisenko et al. (ATEL
#12430), and although the position lies slightly outside of the 90% error
region, we believe that this unambiguously confirms that the optical transient
is related to MAXI J1348-630. This optical transient is also detected by
Swift's UVOT. 

Due to the BAT detection reported in GCN #23795, we also have XRT data
in Windowed Timing mode. The WT spectra, can be well fit by  a power-law
spectrum with photon index = 1.32 +/- 0.02, and a flux of 4 x 10^-9 erg/s/cm^2
(0.5 - 10 keV).  

In addition we have performed a timing analysis of the WT data, and found
evidence of a possible periodicity around 9.8s (or perhaps at 4.9s). The
estimated pulse fraction from folding at this period is low (6%). The light-curv
e
folded at 9.8s has a sinusoidal shape, suggesting that MAXI J1348-630 may
harbor an X-ray pulsar. Follow-up observations are strongly encouraged
in order to determine if this period is real.