Support ATel At Patreon

[ Previous | Next | ADS ]

MAXI J1419-613: Swift/XRT revised localization, Type-I X-ray burst detection

ATel #5780; J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), P. A. Evans (U Leicester), P. Romano (INAF-IASF PA), V. Mangano (PSU), P. Curran (Curtin), K. Yamaoka (Nagoya U) and H. Negoro (Nihon U.)
on 20 Jan 2014; 19:34 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)

Subjects: X-ray, Transient

Referred to by ATel #: 5802, 5894

We report on continued monitoring of the newly discovered X-ray transient MAXI J1421-613 (Morooka et al, ATEL #5750) with Swift's X-ray Telescope (XRT). Swift has been observing this target approximately every 2 days since the initial Swift observations at 19:50UT on January 9th, 2014, which were reported on by Kennea et al. (ATEL #5751).

The X-ray light-curve of MAXI J1421-613 can be characterized as fading for the first ~5 days starting at ~11.5 XRT c/s, and fading to ~2 XRT c/s on 19:51 on January 14th, 2014. Since then the count rate has stayed approximately flat up to the most recent observation which started 08:46UT on January 20th, 2014.

At 08:39UT on January 18th, 2014, Swift XRT detected a Type-I X-ray burst from the MAXI J1421-613. This burst also triggered Swift's Burst Alert Telescope (BAT), as reported by Baumgartner et al (GCN #15749). A detection of a Type-I X-ray burst from this system has previously been reported by INTEGRAL/JEM-X (Bozzo et al., ATEL #5765), and confirms the Neutron Star nature of the compact object in MAXI J1421-613.

Utilizing 6ks of Photon Counting (PC) mode data taken as part of the automated response to the BAT trigger, we have refined the coordinates of MAXI J1421-613, utilizing UVOT data to remove systematic errors in the astrometry. We find an updated position for MAXI J1421-613 of: RA/Dec(J2000) = 215.40504, -61.60700, which is equivalent to:

RA(J2000) = 14h 21m 37.21s,
Dec(J2000) = -61d 36' 25.2'',

with an error radius of 1.5 arc-seconds (90% confidence). The proposed ATCA radio counterpart (Coriat et al., ATEL #5759) lies 0.42 arc-seconds from the center of the revised Swift XRT position, and we therefore conclude that the ATCA radio counterpart is likely associated with MAXI J1421-613. We note that this position is 5.7 arc-seconds from the position we reported in ATEL #5751, and is not consistent with any known catalogued optical/IR source.

Fitting the Windowed Timing (WT) mode data (which are not affected by pile-up, unlike PC mode data), with an absorbed (XSPEC TBabs, abundance set to "wilm") power-law model well fits the data. We find a mean NH = 6.17 +/- 0.23 x 1022 cm-2. Fitted photon indices vary from observation to observation, but are all consistent within errors with a mean value of 2.06 +/- 0.07, showing no evidence of detectable spectral variation in the XRT data taken so far, apart from during the Type-I X-ray burst which requires the addition of a thermal component for the burst.

Observations of MAXI J1421-613 by Swift are on-going.