Chandra Observation of SN 2012A
ATel #4066; D. Pooley (Sam Houston State Univ., Eureka Scientific) on behalf of a larger collaboration
on 23 Apr 2012; 15:43 UT
Credential Certification: dave pooley (firstname.lastname@example.org)
Subjects: X-ray, Supernovae
As part of our ongoing program to investigate X-ray emission from supernovae with Chandra, we triggered a Chandra ToO observation of the Type II supernova 2012A (CBETs #2974 and #2975; ATels #3855, #3860, #3861, #3863, and #3956). The observation was taken with the ACIS-S3 instrument; it began on 2012 Apr 02.1 and has an exposure time of 9.8 ksec.
We detect two X-rays within 0.5" of the position of SN 2012A. If associated with SN 2012A, the best-fit unabsorbed flux is 9.2E-16 erg/cm^2/s [0.5-8 keV] with a 1-sigma upper limit of 1.6E-15 erg/cm^2/s, assuming a thermal bremsstrahlung spectrum with kT = 1 keV and a column density of N_H = 2.74E20 cm^-2 (Dickey & Lockman 1990). For a distance of 8.1 Mpc, this corresponds to an X-ray luminosity of 7.2E36 erg/s with an upper limit of 1.3E37 erg/s. This flux is below the detection limit of a previous 1.9 ksec Chandra observation (ObsID 7094) which occurred on 2006 May 21.8.
There are two other Chandra sources within 10" of the position of SN 2012A, both of which likely contributed to the Swift/XRT detected flux (ATel #3956). Preliminary spectral fits of these two sources indicate unabsorbed fluxes of (5.7 +/- 1.2)E-15 and (1.4 +/- 0.2)E-14 erg/cm^2/s [0.5-8 keV], using the same assumed spectral model as above. Summing the two gives a value below the Swift/XRT flux of (8.7 +/- 1.5)E-14 erg/cm^2/s reported in ATel #3956. Note that the flux given in ATel #3956 assumes a 10 keV bremsstrahlung model and is for the 0.2-10 keV band; using a 1 keV bremsstrahlung model (as above) and the 0.5-8 keV band, the Swift/XRT data yield an unabsorbed flux of (4.0 +/- 0.6)E-14 erg/cm^s/s.
Determining the contribution of SN 2012A to the Swift/XRT flux reported in ATel #3956 will require a more detailed analysis.