Multi-frequency study of the Large Magellanic Cloud Supernova Remnant J0529-6653 near Pulsar B0529-66

A distinguishing characteristic of SNRs in radio wavelengths is their predominantly non-thermal continuum emission. Generally, SNRs display a radio spectral index of α ∼ -0.5 (defined by S ∝ ν α ), although α may vary significantly, as there exists a wide variety of types of SNRs in different environments and stages of evolution (Filipović et al. 1998). For example, younger remnants can have a spectral index of α ∼ -0.8, while older SNRs and Pulsar Wind Nebulae (PWN) tend to have flatter radio spectra with α ∼ -0.2. SNRs have a great impact on the physical properties, struc-ture, and evolution of the interstellar medium (ISM). Conversely, the interstellar environments in which SNRs reside will heavily affect the remnants’ evolution.

Type II supernovae result from the core collapse of massive stars with initial masses greater than ∼ 8 ± 1M (Smartt 2009), and may leave behind compact central objects, such as neutron stars that may be observable as pulsars. However, not many SNRs from Type II supernovae are observed to host pulsars. Among the 51 confirmed and 25 possible candidate SNRs in the LMC (Klimek et al. 2010;Desai et al. 2010, Filipović et al. in prep), only three (N 49, 30 Dor B, B0540-693) have documented associations with a pulsar (Manchester et al. 2006). There are over 70 well studied SNRs in the Magellanic Clouds (MCs) as well as 19 detected pulsars. Ridley & Lorimer (2010) modelled the potentially observable radio pulsars in the MCs and predicted some 1.79×10 4 pulsars. The Milky Way (MW) has 274 SNRs (Green 2009) and ∼1900 pulsars. Therefore, the observed SNR/PSR ratio in the MCs is much less than in the MW (∼1/20). However, if the pulsar surveys are sensitivity limited, then the expected ratio of the mean distances ∼(10/50) 2 would result in the two fractions being similar. This rarity of pulsar-SNR connections may be attributed to the fact that many young neutron stars in SNRs exhibit different properties from the traditional radio pulsars (Gotthelf & Vasisht 2000). Radio pulsars remain detectable well after their SNRs have merged into the ISM; therefore, most pulsars are not in SNRs and their general properties may be different from those young ones in SNRs.

PSR B0529-66 in the LMC was the first extra-galactic pulsar discovered. It was found by McCulloch et al. (1983) using the 64-m radio telescope at the Parkes Observatory. The pulsar was studied by Costa et al. (1991) at a frequency of 600 MHz with the intent of using a polarimeter to collect integrated profiles, rotation and dispersion measures. Crawford et al. (2001) used the Parkes telescope at 20 cm and improved the radio positional accuracy to RA (J2000)=05 h 29 m 50.92 s (±0.13 s ) and DEC (J2000)=-66 • 52 38.2 (±0.9 ). Manchester et al. (2005) then included new and more detailed information on the pulsar in a catalogue along with 1532 other pulsars and in 2006 re-observed the pulsar at Parkes at a wavelength of 20 cm. Filipović et al. (1998) detected the radio source LMC B0530-6655 and suggested it to be an SNR candidate based on its non-thermal spectral index. We note that the SNR J0529-6653 (or LMC B0530-6655) lies just on the northeast edge of the arc of Hα nebulosity DEM L214 (Davies et al. 1976). Finally, Haberl & Pietsch (1999, hereafter HP99) detected a nearby ROSAT X-ray source ([HP99] 440) at a position of RA (J2000)=05 h 29 m 59.3 s and DEC (J2000)=-66 • 53 13 .

Here, we report on radio-continuum, X-ray and optical observations of the candidate LMC SNR J0529-6653 with its possible association with the LMC pulsar PSR B0529-66. Observations, data reduction and imaging techniques are described in Sect. 2. The astrophysical interpretation of the moderate-resolution total intensity and polarimetric images are discussed in Sect. 3.

We used radio observations at four frequencies (Table 1) to study and measure flux densities of SNR J0529-6653. For the 36 cm (Molonglo Synthesis Telescope -MOST) flux density measurement given in Table 1 we used unpublished images as described by Mills et al. (1984) and for the 20 cm we used image from Hughes et al. (2007). Two Australia Telescope Compact Array (ATCA) projects (C634 and C797; at 6/3cm) observations were combined with mosaic observations from project C918 (Dickel et al. 2005). Data for project C634 were taken by the ATCA on 1997 August 2, using the array configuration EW375. Four days of observations were taken from project C797: 1999 May 1-2 (array configuration: 1.5C), 1999 July 21 (array configuration 750D), and 1999 July 31 (array configuration: 1.5D). For the final image (stokes parameter I ) we exclude baselines created with the 6 th ATCA antenna, leaving the remaining five an

…(Full text truncated)…