MAXI J1848-015: Swift localization at the core of GLIMPSE-C01
ATel #14420; J. A. Kennea (PSU), A. Bahramian (ICRAR), P. A. Evans, A. P. Beardmore (U Leicester), H. A. Krimm (CRESST/GSFC/USRA), P. Romano (INAF-IASFPA), K. Yamaoka (Nagoya U.), M. Serino (RIKEN), H. Negoro (Nihon U.)
on 23 Feb 2021; 02:55 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)
On February 21st, 2021, Swift performed a Target of Opportunity observation of MAXI J1848-015, a new transient discovered by MAXI on December 20th, 2020 (ATEL #14282), and localized and observed several times by NuSTAR (ATEL #14282, ATEL #14327). The Swift observation was delayed due to the object being too close to the Sun to observe when originally discovered. In 1.6ks of Photon Counting mode data, we find a previously uncatalogued source at the following coordinates: RA/Dec(J2000) = 282.20697, -1.49738, which is equivalent to:
RA(J2000) = 18h 48m 49.67s
Dec(J2000) = -01d 29m 50.6s
with estimated uncertainty of 2.3 arc seconds radius (90% containment). This position is inside the NuSTAR 66 arc-second error region, 57.5 arcseconds from the centre, and is 2.5 arc minutes from the center of the MAXI position, inside the MAXI region, and is therefore consistent with both localizations of MAXI J1848-015.
We note that this position lies close to the Fermi source 4FGL J1848.7-0129, and within the cluster GLIMPSE-C01. We note that the source appears to be consistent with being located in the core of the cluster, suggesting that this is not chance coincidence, and that MAXI J1845-015 is a member of the cluster.
In addition its position is consistent with the X-ray source 3XMM J184849.5-012950, although we note that in previous observations of the cluster by Chandra, no source consist with the Swift position was found, suggesting a previously undetected transient. We note that the position is not consistent with AX J1848.8-0129, which was previously suggested as a counterpart of MAXI J1848-015.
The spectrum is well fit either by an absorbed power-law with photon index of 2.6 +/- 0.6 and N_H = 9.5 +/- 2.5 x10^22 cm^-2, or a diskbb model with N_H = 6.6 +/- 1.5 x 10^22 cm^-2 and kT_in = 1.7 +/- 0.4 keV. The observed flux 2 x 10^-11 erg/s/cm^2 (0.3 -10 keV), 1.7(+3.8/-0.9) x 10^-10 erg/s/cm^2 corrected for absorption. Due to the high absorption and relatively low count rate (0.02 c/s), it is not possible to distinguish between the two models.
Archival Swift observations of this position have been performed, resulting in a single detection of this source previously by Swift on November 20th, 2017, at which time the source was at a level of 0.007 c/s, 4.3x fainter than in our current observation, suggesting that the source continues to be in outburst.
This work was supported by NASA Grant 80NSSC20K1103, awarded by the Swift Guest Investigator program.
