Discovery of a New Supernova Remnant in the Swift Galactic Plane Survey

ATel #3415; J. M. Miller, M. R. Reynolds, D. Maitra, K. Gultekin (Michigan); N. Gehrels (NASA/GSFC); J. Kennea, M. Siegel, J. Gelbord (PSU); P. Kuin (MSSL)
on 8 Jun 2011; 17:36 UT
Credential Certification: Jon Miller (jonmm@umich.edu)

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We report the discovery of a new supernova remnant. Following the detection of an extended source in a Swift/XRT exposure in the Galactic plane, we requested a short 5 ks exposure with Chandra. The Swift observation was obtained on 22 February 2011 (observation 00042184001), and the Chandra ACIS-S observation was obtained on 03 June 2011 (observation 13419).

If characterized with a circle, the center of the remnant could be approximated with the following coordinates: 13:21:50.9, -63:33:50 (J2000), or (l,b) = 306.309034, -0.891719, with a radius of approximately 110 arcseconds. We suggest the source be designated Swift J132150.9-633350.

The position of the remnant is broadly consistent with a source in the ROSAT Bright Source Catalog (Voges et al. 1999 A&A 349 389), 1RXS J132149.8-633426. However, the spatial extent of the source and its likely nature are only clear in the Swift/XRT and Chandra/ACIS-S images owing to their coverage of X-rays above 2 keV (this line of sight suffers from a column density of 1 E+22, or higher). An Einstein source, 1ES 1318-632 (LS 3039), is spatially separated from the remnant edge by 2 arcminutes.

The remnant is strongly brightened to one edge in the Chandra/ACIS-S image. It is not yet clear if this is due to a bow shock, and structure within the remnant is possibly suggestive of structure like that seen close to the Vela pulsar in Chandra images. This structure is also evident in Spitzer/MIPS images at 24 microns obtained through the MIPSGAL survey (Carey et al., 2009, PASP, 121, 76).

The Chandra spectrum of the remnant requires a plasma component, with a temperature of approximately 0.7 keV. Lines from Ne, Fe L, Si, S, and Ar, and Fe K are evident in the spectrum. Fits with an APEC model suggest that small abundance variations are possible, relative to solar values. Imaging analysis indicates that these elements are not uniformly distributed within the remnant. Fits with a Sedov model give a temperature 1.0~keV; combining this with the extent of the remnant suggests an age of 140 (d/1 kpc) years (its distance is not yet known). Overall, the morphology and spectrum of this new remnant are somewhat similar to N132D in the LMC (e.g. Borkowski, Hendrick, & Reynolds 2007, ApJ, 671, L45).

Multi-wavelength follow-up observations are encouraged. A full paper on detailed X-ray imaging and spectroscopy of this source will be submitted soon. We thank Harvey Tananbaum and the Chandra X-ray Center for granting and executing a Director's Time observation.

Images are available here:
http://www.astro.lsa.umich.edu/~jonmm/snr_4panel.pdf
http://www.astro.lsa.umich.edu/~jonmm/color.pdf

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This Swift Galactic Plane Survey is tiling 240 square degrees of the Galactic plane, from -60 < l < 60 and -1 < b < -1. Each exposure is 500 seconds in duration, and includes simultaneous XRT (0.5-10 keV) and UVOT/UVM2 images (2000-2500 Angstroms). Exposures accumulate continually as the survey is conducted as a series of "filler" target observations. In the near future, we will start to submit weekly telegrams to list source detections, positions, and counterparts. The PI of the survey is Jon Miller and the lead scientist is Mark Reynolds. Co-Is include Dipankar Maitra, Kayhan Gultekin, Neil Gehrels, Jamie Kennea, Mike Siegel, Jonathan Gelbord, and Paul Kuin.