Multi - frequency radio spectral studies of the supernova remnant G 78 . 2 + 2 . 1

نویسندگان

  • X. Zhang
  • Y. Zheng
  • T. L. Landecker
  • L. A. Higgs
چکیده

A new map of the SNR G78.2+2.1 at 232 MHz is presented. This map is used with other images at 408, 1420, 2695 and 4800 MHz to investigate the total spectral index of the SNR and the variation of spectral index across it. The integrated spectral index is α = 0.54 ± 0.02 (where S ν ∝ ν −α). Maps of the spectral-index variation across the source are derived using a method which calculates a differential spectral index. This method is independent of offset errors and large-scale background variations. Systematic spectral-index variations of ∼ ± 0.15 are found, consistently in the many independent pairs of data sets. Regions of higher spectral index (steeper spectra) appear around the periphery of the remnant and in its central area. Regions of lower spectral index (flatter spectra) are also found within the remnant. The latter may result from a change in the nature of the non-thermal emission or may represent " contamination " from underlying patches of thermal emission. There is no clear correlation of spectral index with intensity across the SNR. Theoretical reasons for spectral-index variations have been explored but no clear interpretation of the apparent spectral steepening near the shock front has been found nor has an explanation of the steep-spectrum central region.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

ar X iv : a st ro - p h / 02 02 26 2 v 1 1 3 Fe b 20 02 Spectral Components of the Radio Composite Supernova Remnant G 11 . 2 − 0 . 3

We present a high-resolution radio study of the supernova remnant (SNR) G11.2−0.3 using archival VLA data. Spectral tomography is performed to determine the properties of this composite-type SNR’s individual components, which have only recently been distinguished through X-ray observations. Our results indicate that the spectral index of the pulsar wind nebula (PWN), or plerion, is αP = 0.25 +0...

متن کامل

New shell radio supernova remnant G 16 . 2 − 2 . 7

The extended radio source G16.2−2.7 is detected as a new previously uncataloged Galactic supernova remnant. Its non-thermal radio spectrum has spectral index α = −0.51, with Sν(1GHz) = 2.08 Jy, as being measured with the RATAN-600 radio telescope. The NRAO VLA Sky Survey (NVSS) map at 1.4 GHz shows a shelllike bilateral structure. The similar smoothed image from the Effelsberg survey at 2.7 GHz...

متن کامل

Multi-frequency observations of SNR J0453–6829 in the LMC A composite supernova remnant with a pulsar wind nebula

Context. The Large Magellanic Cloud (LMC) is rich in supernova remnants (SNRs) which can be investigated in detail with radio, optical and X-ray observations. SNR J0453–6829 is an X-ray and radio-bright remnant in the LMC, within which previous studies revealed the presence of a pulsar wind nebula (PWN), making it one of the most interesting SNRs in the Local Group of galaxies. Aims. We study t...

متن کامل

A multi-frequency radio study of the supernova remnant HB9

We present a new radio map of HB9 at 232 MHz made at the Beijing Astronomical Observatory. We also present previously unpublished maps at 151 MHz, from the new Cambridge Low-Frequency Synthesis Telescope Survey, and at 4750 MHz, from the Effelsberg Telescope. These radio maps are compared with previously published maps at 408, 1420, and 2695 MHz, thus providing the most complete frequency cover...

متن کامل

The Radio Spectral Index and Expansion of 3 C 58

We present new observations of the plerionic supernova remnant 3C 58 with the VLA at 74 and 327 MHz. In addition, we re-reduced earlier observations at 1.4 and 4.9 GHz taken in 1973 and 1984. Comparing these various images, we Ðnd that (1) the remnant has a Ñat and relatively uniform spectral-index distribution, (2) any expansion of the remnant with time is signiÐcantly less than that expected ...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 1997