Radio-continuum study of Large Magellanic Cloud Supernova Remnant J0509-6731
L. M. Bozzetto, M. D. Filipovic, D. Urosevic, R. Kothes, E. J. Crawford
aa r X i v : . [ a s t r o - ph . GA ] M a r Mon. Not. R. Astron. Soc. , 1–7 (2002) Printed 11 September 2018 (MN LaTEX style file v2.2)
Radio–continuum study of Large Magellanic CloudSupernova Remnant J0509–6731
L. M. Bozzetto, M. D. Filipovi´c, D. Uroˇsevi´c, , R. Kothes, & E. J. Crawford School of Computing and Mathematics, University of Western Sydney Locked Bag 1797, Penrith South DC, NSW 1797, Australia Department of Astronomy, Faculty of Mathematics, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia Isaac Newton Institute of Chile, Yugoslavia Branch National Research Council Canada, Herzberg Institute of Astrophysics, Dominion Radio Astrophysical Observatory, P.O. Box 248,Penticton, British Columbia V2A 6J9, Canada
Released 2011 Xxxxx XX
ABSTRACT
We present a detailed study of Australia Telescope Compact Array (ATCA) observa-tions ( λ = 20, 13, 6 & 3 cm) of supernova remnant (SNR) J0509–6731 in the LargeMagellanic Cloud (LMC). The remnant has a ring morphology with brightened re-gions towards the south-western limb. We also find a second brightened inner ringwhich is only seen in the radio-continuum. The SNR is almost circular, with a diam-eter ranging from 7 to 8 pc, and a steep radio spectral index between 36 and 3 cm of α = − . ± .
02, which is characteristic of younger SNRs. We also report detectionof radially orientated polarisation across the remnant at 6 cm, with a mean fractionalpolarisation level of P ∼ = (26 ± ∼ µ G) and Σ − D (Σ = 1 . × − W m − Hz − sr − , D = 7.35 pc) to be consistent with other youngremnants. Key words: polarization – ISM: supernova remnants – Magellanic Clouds – radiocontinuum: ISM.
Supernova remnants (SNRs) play a vital role in theuniverse, enriching the interstellar medium (ISM) andsignificantly influences the ISMs evolution, structure andphysical properties. The study of SNRs in our own Galaxyis not ideal due to difficulties in estimating accuratedistances (which inhibits accurate analysis such as extentand surface brightness) and the high level of absorption inthe direction of the Galactic plane. As an alternative, theLarge Magellanic Cloud (LMC) at a proximity of 50 kpc(Macri et al. 2006) is a near ideal galaxy for the study ofSNRs due to its high active star forming regions (such as30 Dor) and location outside of the Galactic plane at anangle of 35 ◦ (van der Marel & Cioni 2001). Its distancefrom earth allows us to assume that objects located withinare at approximately the same distance, aiding in variousanalysis methodologies.In the radio-continuum, SNRs predominately emitnon-thermal continuum emission and generally exhibit aspectrum of α ∼ − . S ∝ ν α ). Although thiscan vary as there exists a wide variety of SNRs in differentstages of evolution and expanding in different environments(Filipovic et al. 1998). In this paper, we present new radio-continuum ob-servations of SNR J0509–6731, along with archival radio-continuum, X-ray & optical observations. This sourcewas originally classified by Long et al. (1981) as anSNR in their X-ray survey using the Einstein observa-tory, recording a position of RA (B1950)=05 h m s andDEC (B1950)=–67 ◦ ′ ′′ . Tuohy et al. (1982) estimate aX-ray size of ∼ ′′ , an optical size of 25 ′′ and estimateda shock velocity of > − . No object was foundat this position in the 408 MHz image by Clark, Little &Mills (1976). However, reanalysis of the 408 MHz surveydata by Tuohy et al. (1982), found weak emission at thispoint finding a flux density measurement of 95 ±
15 mJy.Tuohy et al. (1982) also observed this object at 5 GHzand measured a flux density of 30 ± − D ) diagram,SNR J0509–6731 fell below the mean line by a factor of13, which is comparable to young Galactic SNRs. Theycomment that this low Σ − D might be a result of differ-ences in the electron acceleration process in Balmer dom-inated remnants. The remnant is described as a Balmerdominated SNR expanding into a region with a relativelylow density ( n H − ) of neutral hydrogen and ar-gue for a Type Ia supernova (SN). Mathewson et al. (1983)measure an X-ray size of 27 ′′ and a radio spectrum of α = –0.46. Fusco-Femiano & Preite-Martinez (1984) esti- c (cid:13) L. M. Bozzetto et al.
Table 1.
Summary of ATCA observations reduced and used in this study.Date Scan time Right Ascension Declination Array Frequencies BWidth Chan Project(minutes) (MHz) (MHz)2011-Nov-16 49.7 5h 9m 31.00s -67 ◦ ′ ′′ EW367 5,500, 9,000 2048.0 2049 C634 a ◦ ′ ′′ EW367 5,500, 9,000 2048.0 2049 C634 a ◦ ′ ′′
6A 5,500, 9,000 2048.0 2049 C23672010-Nov-28 50.3 5h 9m 30.00s -67 ◦ ′ ′′
6A 5,500, 9,000 2048.0 2049 C23672005-Jun-24 819.7 5h 9m 51.48s -67 ◦ ′ ′′
6B 1,384, 1,472 128.0 33 C13952005-Apr-18 819.8 5h 9m 51.48s -67 ◦ ′ ′′ ◦ ′ ′′ ◦ ′ ′′ ◦ ′ ′′ ◦ ′ ′′ a – The observing procedure in this project is described in the text. mates a shock temperature of 3.1 KeV, an age of 900yr, total swept up mass of 26 M ⊙ and a shock veloc-ity of 1600 km s − , which is well below that proposed byTuohy et al. (1982) of > > × W m − Hz − sr − . van den Bergh (1988) also argues for ayounger remnant, commenting that the small diameter indi-cates an age of > − and is in agreement with an age of ′′ andgive this SNR the association [HP99] 542. Warren & Hughes(2004) confirmed that the SN ejecta had an abundance dis-tribution consistent with Type Ia SN explosion models. Theyalso found that the reverse shock is propagating back intothe Fe-rich ejecta and suggests that the brighting in thesouthwest is due to enhanced density in or a deeper penetra-tion of the reverse shock into the into a portion of the ejectashell and may be caused enhanced ambient density or intrin-sic asymmetry in the explosion itself. Rest et al. (2005) con-firmed the Type Ia classification using light echo spectra andalso established it as a SN1991T-type energetic event. Ad-ditionally, light echo apparent motion was used to estimatethe age of the SNR to be 400 ±
120 yr. Arbutina & Uroˇsevi´c(2005) used a 1 GHz flux density of 70 mJy to estimate asurface brightness–diameter of (Σ − D ) = (4 . × − Wm − Hz − sr − , 7 pc). Ghavamian et al. (2007) estimate anage of 295 - 585 yr, a shock velocity of V s > − , theydetect broad Ly β emission and classify this object as a non-radiative (adiabatic) of Type Ia. Badenes et al. (2008) foundan age of ∼
400 yr, kinetic energy of 1.4 × ergs and con-cluded that the X-ray properties of SNR J0509–6731 wereconsistent with models of an energetic 91T-type SN Ia explo-sion. Seok et al. (2008) states SNR J0509–6731 is thoughtto be dominated by thermal dust continuum with T(dust)94 ± ± × − solar masses.Kosenko et al. (2008) also find that the reverse shock hasrecently reach the iron layers of the ejecta and are in agree-ment with previous studies regarding the brightening in thesouthwest resulting from an asymmetric explosion or den-sity enhancement in the ISM. Models in this study werein good agreement with the observations with circumstellar density of 3 × − g/cm , age of ∼
400 yr and velocity of ∼ − . Desai et al. (2010) found no association be-tween this remnant and a YSO, nor the molecular clouds.Schaefer & Pagnotta (2012) found no ex-companion star toa visual magnitude limit of 26.9 within a radius of 1.43 ′′ ,which they state would infer a double degenerate SN sys-tem. Di Stefano & Kilic (2012) and Wheeler (2012) discussthe possibility of this SNR still being the result of a singledegenerate explosion.The observations, data reduction and imaging tech-niques are described in Section 2. The astrophysical inter-pretation of newly obtained moderate-resolution total inten-sity and polarimetric images in combination with archivalChandra X-ray and HST H α observations are discussed inSection 3. Five Australia Telescope Compact Array (ATCA) projects(C1395, C354, C479, C634 and C2367; at wavelengths of20 cm, 20/13 cm, 6 cm, 6/3 cm and 6/3 cm respectively)were reduced and analysed in this study. A summary ofthese projects can be seen in Table 1. Project C634 con-tain our observations of this SNR, which were taken onthe 15 th and 16 th of November 2011. These observationswere taken by the ATCA using the CABB receiver with thearray configuration EW367, at wavelengths of 3 and 6 cm( ν =9000 and 5500 MHz). The observations were carried outin the so called “snap-shot” mode, totalling ∼
50 minutes ofintegration over a 14 hour period. Source PKS B1934-638was used for primary (flux density) calibration and sourcePKS B0530-727 was used for secondary (phase) calibration.At 6 cm, the shorter baselines from the EW367 observa-tions were complemented by observations taken from projectC2367, which uses a longer baseline array configuration (6A;Table 1), allowing for a higher resolution image. However,we were unable to make use of the 3 cm data from ATCAproject C2367 due to strong interference. This lack of datameant we lost the longer baselines and as a result, no highresolution image is available at this wavelength.The miriad (Sault et al. 1995) and karma (Gooch (cid:13) , 1–7 adio–continuum study of LMC SNR J0509–6731 miriad multi-frequency syn-thesis (Sault & Wieringa 1994) and natural weighting. Theywere deconvolved with primary beam correction applied.The same procedure was used for both U and Q stokes pa-rameter maps.We measured the flux density of SNR J0509–6731 from11 separate images between 36 cm and 3 cm, which aresummarised in Table 2. We obtain five of these flux den-sity measurements from available mosaics; at 36 cm fromthe Molonglo Synthesis Telescope (MOST) mosaic image(as described in Mills et al. 1984) and from the SUMMSmosaic image (Mauch et al. 2008), 20 cm from the mosaicby Hughes et al. (2007). We also used 6 cm and 3 cm mo-saics published by Dickel et al. (2010). The remaining sixmeasurements were taken from the data reduced and anal-ysed in this study using the projects listed in Table 1. Errorsin flux density measurements predominately arose from un-certainties in defining the ‘edge’ of the remnant. However,we estimate these errors to be <
10% (with the exceptionof the 73 cm measurement, where the associated error isgiven by Tuohy et al. 1982). Using the flux density mea-surements in Table 2 (73 – 3 cm), we estimate a spectralindex of α = − .
59. However, it can be seen that the spec-trum breaks at 73 cm, where the recorded flux density is at alevel well below that which is expected (by ∼ α = − . ± . SNR J0509–6731 exhibits a ring-like morphol-ogy (Fig. 1), centred at RA (J2000)=05 h m s ,DEC (J2000)=–67 ◦ ′ ′′ . We estimate the spatial extentof SNR J0509–6731 (Fig. 1) at the 3 σ (Table 2; Col. 4)level (0.1 mJy) along the major (NW–SE) and minor(NE–SW) axes (PA=–34 ◦ ). Its size at 6 cm (5500 MHz) is31 ′′ × ′′ ± ′′ (8 × ∼ ′′ at 6 cm, about 40% of the SNR’s radius.We find a centrally brightening ring in the interior ofthis remnant (Fig. 1), something that is not common amongSNRs. We estimate the size of this ring at 6 cm to be16 ′′ × ′′ ± ′′ (4 × ◦ .There is evident correlation between our 6 cm(5500 MHz) radio-continuum emission and the optical H α Figure 1.
The top image shows the 6 cm intensity image ofSNR J0509–6731 overlaid with the approximate major (NW–SE)and minor (NE–SW) axis. The middle and lower images showthe 1-dimensional cross-section along the overlaid lines in the topimage, with a superimposed line at 3 σ . emission (Hubble Space Telescope; PropID 11015) for thisremnant (Fig. 2). This is particularly evident towards thesouth-western limb of the SNR (where radio emission is thestrongest), where we can see the radio 3 σ contour closelyfollowing the edge of the optical H α emission. The astrom-etry involved in aligning all images in this paper is within1 ′′ . We also find similarities between our 6 cm (5500 MHz)radio-continuum emission and 0.3–7.0 keV X-ray emission(Chandra; observation ID [ObsID] 776 ) as seen in Fig. 3. Taken from c (cid:13) , 1–7 L. M. Bozzetto et al.
Table 2.
Integrated flux densities of SNR J0509–6731. λ ν
ATCA R.M.S Beam Size S
Total ∆S Total
Reference(cm) (MHz) Project (mJy) ( ′′ ) (mJy) (mJy)73 408 MOST 40 157.3 × a × b × × c × × × d × × ×
300 30 3 Tuohy et al. (1982)6 5500 C634, C2367 0.1 2.6 × d × × a – From the image described in Mills et al. (1984) b – From the image described in Mauch et al. (2008) c – From the image described in Hughes et al. (2007) d – From the image described in Dickel et al. (2010) - : : . . . . . . . Right ascension D e c li na t i on Figure 2.
HST H α image of SNR J0509–6731 overlaid with 6 cmATCA contours. The contours are 3, 6, 9, 12 & 15 σ (where σ =33 µ Jy).
The optical H α emission shows highly compressed fila-ments, denoting at high angular resolution the location ofthe forward shock moving into the ISM, outlying the ellip-soidal shell region interior to which the smooth, low com-pressed radio and X-ray emission comes.The non-thermal nature of this remnant in the radio-continuum is confirmed in the spectral energy distribution(SED), shown in Fig. 4, where α = − . ± .
02. This valueis steeper in comparison with typical values of α = − . - : : . . . . . . . Right ascension D e c li na t i on Figure 3.
Chandra X-ray colour composite image ofSNR J0509–6731 at energy levels 0.3–0.6 keV (red) 0.6–0.95 keV(green) and 0.95–7.0 keV (blue). The image has been smoothedusing a gaussian filter ( σ = 2 pixel). ATCA radio contours (at6 cm) have been overlaid at levels of 3, 6, 9, 12 & 15 σ (where σ = 33 µ Jy). ment with current estimation of the remnants age, whichplaces it at ∼
400 yr (Rest et al. 2005; Ghavamian et al.2007; Kosenko et al. 2008; Badenes et al. 2008).A spectral index map was created between 13 cm and6 cm (Fig. 5) to show the spacial spectral variations in theremnant. This was achieved by convolving and re-griddingthe 6 cm image with the tasks regrid and convol , to matchthe size and resolution of the 13 cm image, which had thepoorest resolution and thus allowing no oversampling to oc- c (cid:13) , 1–7 adio–continuum study of LMC SNR J0509–6731 Figure 4.
Radio-continuum spectrum of SNR J0509–6731. Themarkers represent error margins of 10%. cur. A spectral index map was then created using these mapsfrom both observed frequencies. This was done using the miriad task maths , which calculated the spectral index ( α )of each pixel above a level of 3 σ . Pixels below this levelwere blanked in the spectral index map. We note to two dis-tinctive and opposite regions of somewhat steeper spectra( ∼ α =–0.7) marked in yellow around northern and south-ern regions of the SNR.A fractional polarisation image was created at 6 cmusing Q and U parameters (Fig. 6). A signal-to-noise cut-offof 2 σ was used for the Q and U images, while a level of 6 σ was used for the intensity image. Values that fall below thesecut-off levels are blanked in the output image. The lengthof the vectors have been reduced by 50% and placed every1.5 pixels for display purposes. The mean fractional po-larisation was calculated using flux density and polarisation:P= p S Q + S U S I where S Q , S U and S I are integrated intensities for the Q , U and I Stokes parameters. We estimate a mean fractionalpolarisation value of P = 26 ±
13% at 6 cm. The magneticfield of the remnant at 6 cm appears to be radially oriented,which is to be expected from Rayleigh-Taylor instabilities inthe decelerating remnant (Gull 1975; Chevalier 1976). Thisis consistent with similarly young SNRs in our own Galaxy,as well as in the LMC (for e.g. those listed in Table 3).Without reliable polarisation measurements at asecond frequency we cannot determine the Faraday rota-tion and thus cannot deduce the magnetic field strength.However, we make use of the equipartition formula asgiven by Arbutina et al. (2012) to estimate the magnetic spectral index α is defined by S ν = ν α , where S ν is the inte-grated flux density and ν is the frequency. -1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 - : : . . . . . Right ascension D e c li na t i on Figure 5.
Radio-continuum spectrum map of SNR J0509–6731between 13 cm and 6 cm. The sidebar quantifies the spectral indexscale. ATCA radio contours (at 6 cm) have been overlaid at 3, 6,9, 12 & 15 σ (where σ = 33 µ Jy).
Figure 6.
B-field polarisation vectors overlaid on 6 cm ATCAimage of SNR J0509–6731. The blue ellipse in the lower left cornerrepresents the synthesised beamwidth of 2.6 ′′ × ′′ and the blueline below the ellipse represents a polarization vector of 100%. field strength of this SNR. This formula is based on theBell (1978) diffuse shock acceleration (DSA) theory. Thisderivation is purely analytical, accommodated especiallyfor the estimation of magnetic field strength in SNRs.The average equipartition field over the whole shell ofSNR J0509–6731 is ∼ µ G with an estimated minimum c (cid:13) , 1–7 L. M. Bozzetto et al.
Table 3.
Comparison of SNR J0509–6731 to similar remnants.Name Age α ∗ P P λ Reference(yr) (%) (cm)0509–67.5 ∼ − .
73 26 ±
13 6 This workCassiopeia A — − .
77 8-10 6 Anderson et al. (1995)Tycho ∼ − .
65 20-30 a ∼ − .
64 6 6 DeLaney et al. (2002)SN 1006 ∼ − . d
20 Reynoso et al. (2013)N132D ∼ b − .
70 4 6 Dickel & Milne (1995)0519-6902 ∼ c − .
53 2 6 Bozzetto et al. (2012c) ∗ – Galactic spectral indices came from the catalogue by Green (2009). a – Based on the mean polarisation found for the brightened limbs b – Vogt & Dopita (2011) c – Borkowski et al. (2006) d – Higher polarisation (near the theoretical limit of ∼ energy of E min = 1.2 × ergs (see Arbutina et al. (2012);and corresponding “calculator” ). This value is typical ofyoung SNRs with a strongly amplified magnetic field.The position of SNR J0509–6731 at the surface bright-ness to diameter (Σ − D ) diagram (Σ = 1 . × − Wm − Hz − sr − , D = 7.35 pc) by Berezhko & V¨olk (2004),suggests that this remnant is in the transition phase betweenlate free expansion and early Sedov phase, with an explosionenergy of ∼ × , which evolves in an environment witha density of ∼ − . This estimate of minimum explo-sion energy is lower than that found by Badenes et al. (2008)who found a value of 1.40 × , a result of using differentmodels. Our estimate of surface brightness is comparable tovalues found for galactic remnants in rarified environments,such as Tycho’s SNR (Σ = 1 . × − W m − Hz − sr − , D = 9.3 pc) and Kepler’s SNR (Σ = 3 . × − Wm − Hz − sr − , D = 5.2 pc) (Pavlovi´c et al. 2013). We have used observations taken by the ATCA to carryout a detailed radio continuum study on SNR J0509–6731.With a size of only D ∼ = 8 × α = − . ± µ G, which is characteristicof a young remnant (e.g. Jiang et al. 2013). Its small sizealso sets this SNR apart from typical Σ − D values of SNRsat Σ = 1 . × − W m − Hz − sr − , D = 7.35 pc, though,still in close proximity to another Balmer dominated LMCSNR, SNR J0519–6902. This SNR shares the same radiallyorientated polarisation as other young Type Ia remnants,with a mean fractional polarisation level of P = (26 ± ACKNOWLEDGEMENTS
The Australia Telescope Compact Array is part of the Aus-tralia Telescope which is funded by the Commonwealth ofAustralia for operation as a National Facility managed by The calculator is available athttp://poincare.matf.bg.ac.rs/˜arbo/eqp/
CSIRO. This research is supported by the Ministry of Edu-cation and Science of the Republic of Serbia through projectNo. 176005.
REFERENCES
Anderson M. C., Keohane J. W., Rudnick L., 1995, ApJ,441, 300Arbutina B., Uroˇsevi´c D., 2005, MNRAS, 360, 76Arbutina B., Uroˇsevi´c D., Andjeli´c M. M., Pavlovi´c M. Z.,Vukoti´c B., 2012, ApJ, 746, 79Badenes C., Hughes J. P., Cassam-Chena¨ı G., Bravo E.,2008, ApJ, 680, 1149Bell A. R., 1978, MNRAS, 182, 443Berezhko E. G., V¨olk H. J., 2004, A&A, 427, 525Borkowski K. J., Williams B. J., Reynolds S. P., BlairW. P., Ghavamian P., Sankrit R., Hendrick S. P., LongK. S., Raymond J. C., Smith R. C., Points S., WinklerP. F., 2006, ApJ, 642, L141Bozzetto L. M., Filipovi´c M. D., Crawford E. J., Haberl F.,Sasaki M., Uroˇsevi´c D., Pietsch W., Payne J. L., de HortaA. Y., Stupar M., Tothill N. F. H., Dickel J., Chu Y.-H.,Gruendl R., 2012a, MNRAS, 420, 2588Bozzetto L. M., Filipovic M. D., Crawford E. J., PayneJ. L., de Horta A. Y., Stupar M., 2012b, Rev. MexicanaAstron. Astrofis., 48, 41Bozzetto L. M., Filipovi´c M. D., Crawford E. J., Sasaki M.,Maggi P., Haberl F., Uroˇsevi´c D., Payne J. L., De HortaA. Y., Stupar M., Gruendl R., Dickel J., 2013, MNRAS,432, 2177Bozzetto L. M., Filipovic M. D., Urosevic D., CrawfordE. J., 2012c, Serbian Astronomical Journal, 185, 25Chu Y.-H., Kennicutt Jr. R. C., 1988, AJ, 96, 1874de Horta A. Y., Filipovi´c M. D., Bozzetto L. M., Maggi P.,Haberl F., Crawford E. J., Sasaki M., Uroˇsevi´c D., PietschW., Gruendl R., Dickel J., Tothill N. F. H., Chu Y.-H.,Payne J. L., Collier J. D., 2012, A&A, 540, A25DeLaney T., Koralesky B., Rudnick L., Dickel J. R., 2002,ApJ, 580, 914Desai K. M., Chu Y.-H., Gruendl R. A., Dluger W., KatzM., Wong T., Chen C.-H. R., Looney L. W., Hughes A.,Muller E., Ott J., Pineda J. L., 2010, AJ, 140, 584Di Stefano R., Kilic M., 2012, ApJ, 759, 56 c (cid:13) , 1–7 adio–continuum study of LMC SNR J0509–6731 Dickel J. R., McIntyre V. J., Gruendl R. A., Milne D. K.,2010, AJ, 140, 1567Dickel J. R., Milne D. K., 1995, AJ, 109, 200Dickel J. R., van Breugel W. J. M., Strom R. G., 1991, AJ,101, 2151Filipovic M. D., Pietsch W., Haynes R. F., White G. L.,Jones P. A., Wielebinski R., Klein U., Dennerl K., Ka-habka P., Lazendic J. S., 1998, A&AS, 127, 119Fusco-Femiano R., Preite-Martinez A., 1984, ApJ, 281, 593Ghavamian P., Blair W. P., Sankrit R., Raymond J. C.,Hughes J. P., 2007, ApJ, 664, 304Gooch R., 1995, in Shaw R. A., Payne H. E., Hayes J. J. E.,eds, Astronomical Data Analysis Software and Systems IVVol. 77 of Astronomical Society of the Pacific ConferenceSeries, Space and the Spaceball. p. 144Green D. A., 2009, Bulletin of the Astronomical Society ofIndia, 37, 45Haberl F., Pietsch W., 1999, A&AS, 139, 277Hughes A., Staveley-Smith L., Kim S., Wolleben M., Fil-ipovi´c M., 2007, MNRAS, 382, 543Hughes J. P., Hayashi I., Helfand D., Hwang U., Itoh M.,Kirshner R., Koyama K., Markert T., Tsunemi H., WooJ., 1995, ApJ, 444, L81Jiang Z. J., Zhang L., Fang J., 2013, MNRAS, 433, 1271Kosenko D., Vink J., Blinnikov S., Rasmussen A., 2008,A&A, 490, 223Long K. S., Helfand D. J., Grabelsky D. A., 1981, ApJ,248, 925Macri L. M., Stanek K. Z., Bersier D., Greenhill L. J., ReidM. J., 2006, ApJ, 652, 1133Mathewson D. S., Ford V. L., Dopita M. A., Tuohy I. R.,Long K. S., Helfand D. J., 1983, ApJS, 51, 345Mauch T., Murphy T., Buttery H. J., Curran J., HunsteadR. W., Piestrzynski B., Ropbertson J. G., Sadler E. M.,2008, VizieR Online Data Catalog, 8081, 0Mills B. Y., Turtle A. J., Little A. G., Durdin J. M., 1984,Australian Journal of Physics, 37, 321Pavlovi´c M. Z., Uroˇsevi´c D., Vukoti´c B., Arbutina B.,G¨oker ¨U. D., 2013, ApJS, 204, 4Rest A., Suntzeff N. B., Olsen K., Prieto J. L., Smith R. C.,Welch D. L., Becker A., Bergmann M., Clocchiatti A.,Cook K., Garg A., Huber M., Miknaitis G., Minniti D.,Nikolaev S., Stubbs C., 2005, Nature, 438, 1132Reynoso E. M., Hughes J. P., Moffett D. A., 2013, AJ, 145,104Sault R. J., Teuben P. J., Wright M. C. H., 1995, in ShawR. A., Payne H. E., Hayes J. J. E., eds, Astronomical DataAnalysis Software and Systems IV Vol. 77 of AstronomicalSociety of the Pacific Conference Series, A RetrospectiveView of MIRIAD. p. 433Sault R. J., Wieringa M. H., 1994, A&AS, 108, 585Schaefer B. E., Pagnotta A., 2012, Nature, 481, 164Seok J. Y., Koo B.-C., Onaka T., Ita Y., Lee H.-G., LeeJ.-J., Moon D.-S., Sakon I., Kaneda H., Lee H. M., LeeM. G., Kim S. E., 2008, PASJ, 60, 453Smith R. C., Kirshner R. P., Blair W. P., Winkler P. F.,1991, ApJ, 375, 652Tuohy I. R., Dopita M. A., Mathewson D. S., Long K. S.,Helfand D. J., 1982, ApJ, 261, 473van den Bergh S., 1988, ApJ, 327, 156van der Marel R. P., Cioni M.-R. L., 2001, AJ, 122, 1807Vogt F., Dopita M. A., 2011, Ap&SS, 331, 521 Warren J. S., Hughes J. P., 2004, ApJ, 608, 261Wheeler J. C., 2012, ApJ, 758, 123Wills K. A., Pedlar A., Muxlow T. W. B., Wilkinson P. N.,1997, MNRAS, 291, 517 c (cid:13)000