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Supernova remnants and their pulsar wind nebulae
Stockholm University, Faculty of Science, Department of Astronomy. (Supernovae)
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Massive stars die in powerful stellar explosions, so-called supernovae. In most cases, a neutron star or a black hole is expected to form in the center. The ejected material in these explosions expands out into the surroundings for tens of thousands of years, forming a supernova remnant. If a rapidly rotating neutron star, i.e. pulsar, has been created in the center, a pulsar wind nebula (PWN) will form around it. This thesis focuses mainly on the composite supernova remnant SNR B0540-69.3, as well as the pulsar\psr. This object has a dynamical PWN for which detailed observations have been done using various ground-based and space-borne telescopes. The thesis also includes a detailed study of the Crab-like supernova remnant 3C 58, which allowed us to detect optical emission from the pulsar+PWN system. This made it become the third PWN, after the Crab nebula and the 0540 PWN, to be seen in the optical.

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University , 2012. , 44 p.
Keyword [en]
pulsars, supernovae, ISM
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
URN: urn:nbn:se:su:diva-79103ISBN: 978-91-7447-466-4 (print)OAI: oai:DiVA.org:su-79103DiVA: diva2:547281
Public defence
2012-09-24, FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2012-09-03 Created: 2012-08-27 Last updated: 2012-09-03Bibliographically approved
List of papers
1. The young pulsar PSR B0540-69.3 and its synchrotron nebula in the optical and X-rays
Open this publication in new window or tab >>The young pulsar PSR B0540-69.3 and its synchrotron nebula in the optical and X-rays
2004 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 425, no 3, 1041-1060 p.Article in journal (Refereed) Published
Abstract [en]

The young PSR B0540-69.3 in the LMC is the only pulsar (except the Crab pulsar) for which a near-UV spectrum has been obtained. However, the absolute flux and spectral index of the HST/FOS spectrum are significantly higher than suggested by previous broad-band time-resolved groundbased UBVRI photometry. To investigate this difference, observations with ESO/VLT/FORS1 and analysis of HST/WFPC2 archival data were done. We show that the HST and VLT spectral data for the pulsar have ⪆50% nebular contamination and that this is the reason for the above-mentioned difference. The broadband HST spectrum for the range 3300-8000 Å is clearly nonthermal and has a negative spectral index, Fν ∝ ν-α with αν = 1.07+0.20-0.19. This is different from the almost flat spectrum of the Crab pulsar, and also steeper than for the previously published broadband photometry of PSR B0540-69.3. We have also studied the spatial variations of the brightness and spectral index of the Pulsar Wind Nebula (PWN) around the pulsar, and find no significant spectral index variation over the PWN. The HST data show a clear asymmetry of the surface brightness distribution along the major axis of the torus-like structure of the PWN with respect to the pulsar position, also seen in Chandra/HRC X-ray images. This is different from the Crab PWN and likely linked to the asymmetry of the surrounding SN ejecta. The HST/WFPC2 archival data have an epoch separation of 4 years, and this allows us to estimate the proper motion of the pulsar. We find a motion of 4.9±2.3 mas yr-1 (corresponding to a transverse velocity of 1190±560 km s-1) along the southern jet of the PWN. If this is confirmed at a higher significance level by future observations, this makes PSR B0540-69.3 the third pulsar with a proper motion aligned with the jet axis of its PWN, which poses constraints on pulsar kick models. To establish the multiwavelength spectrum of the pulsar and its PWN, we have included recent Chandra X-ray data, and discuss the soft pulsar X-ray spectrum based on spectral fits including absorption by interstellar gas in the Milky Way, LMC as well as the supernova ejecta. We have compared the multiwavelength spectra of PSR B0540-69.3 and the Crab pulsar, and find that both PSR B0540-69.3 and the Crab pulsar have a weaker flux in the optical than suggested by a low-energy power-law extension of the X-ray spectrum. This optical depression is more severe for PSR B0540-69.3 than for the Crab pulsar. The same trend is seen for the PWNe of the two pulsars, and continues for low energies also out in the radio band. We discuss possible interpretations of this behavior. Based on observations performed at the European Southern Observatory, Paranal, Chile (ESO Program 67.D-0519).

Keyword
stars: pulsars: general, stars: pulsars: individual: PSR B0540-69.3, ISM: supernova remnants, stars: supernovae: general, astrometry
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-30956 (URN)10.1051/0004-6361:20040499 (DOI)
Available from: 2009-11-01 Created: 2009-11-01 Last updated: 2012-08-28Bibliographically approved
2. Optical observations of the young supernova remnant SNR 0540-69.3 and its pulsar
Open this publication in new window or tab >>Optical observations of the young supernova remnant SNR 0540-69.3 and its pulsar
2005 (English)In: Advances in Space Research, ISSN 0273-1177, Vol. 35, no 6, 1106-1111 p.Article in journal (Refereed) Published
Abstract [en]

We have used the ESO NTT/EMMI and VLT/FORS1 instruments to examine the LMC supernova remnant 0540-69.3 as well as its pulsar (PSR B0540-69) and pulsar-powered nebula in the optical range. Spectroscopic observations of the remnant covering the range of 3600 7350 Å centered on the pulsar produced results consistent with those of [Kirshner, R.P., Morse, J.A., Winkler, P.F., et al. The penultimate supernova in the Large Magellanic Cloud - SNR 0540-69.3. Astrophys.J. 342, 260 271, 1989.] but also revealed many new emission lines. The most important are [Ne III] λλ3869, 3967 and Balmer lines of hydrogen. In both the central part of the remnant, as well as in nearby H II regions, the [O III] temperature is higher than ˜2 × 104 K, but lower than previously estimated. For PSR B0540-69, previous optical data are mutually inconsistent: HST/FOS spectra indicate a significantly higher absolute flux and steeper spectral index than suggested by early time-resolved groundbased UBVRI photometry. We show that the HST and VLT spectroscopic data for the pulsar have ≳50% nebular contamination, and that this is the reason for the previous difference. Using HST/WFPC2 archival images obtained in various bands from the red part of the optical to the NUV range we have performed an accurate photometric study of the pulsar, and find that the spectral energy distribution of the pulsar emission has a negative slope with α=1.07-0.19+0.20. This is steeper than derived from previous UBVRI photometry, and also different from the almost flat spectrum of the Crab pulsar. We also estimate that the proper motion of the pulsar is 4.9 ± 2.3 mas year‑1, corresponding to a transverse velocity of 1190 ± 560 km s‑1, projected along the southern jet of the pulsar nebula.

Keyword
Supernova remnants, Pulsars, Spectroscopy, Photometry, Astrometry, Supernova remnants: individual: SNR 0540-69.3, Pulsars: individual: PSR B0540-69.3
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-30952 (URN)10.1016/j.asr.2005.01.071 (DOI)
Available from: 2009-11-01 Created: 2009-11-01 Last updated: 2012-08-28Bibliographically approved
3. Optical identification of the 3C 58 pulsar wind nebula
Open this publication in new window or tab >>Optical identification of the 3C 58 pulsar wind nebula
Show others...
2008 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 486, no 1, 273-282 p.Article in journal (Refereed) Published
Abstract [en]

Context: The Crab-like supernova remnant 3C 58 contains the young pulsar PSR J0295+6449, which powers a radio plerion and a compact torus-like pulsar wind nebula visible in X-rays. Aims: We have performed deep optical imaging of the 3C 58 field to detect the optical counterpart of the pulsar and its wind nebula. Methods: The imaging was carried out with the Nordic Optical Telescope. We also analyzed the archival images of the field obtained with the Chandra/ACIS-S and HRC-S in X-rays and with the Spitzer/IRAC in the mid-infrared. Results: We detect a faint extended elliptical optical object with B=24.06 m ± 0.08 and V=23.11 m ± 0.04, whose center and peak brightness position are consistent at the sub-arcsecond level with the position of the pulsar. The morphology of the object and the orientation of its major axis are in excellent agreement with the torus region of the pulsar wind nebula seen almost edge on in the X-rays, although its extension is only about a half of what is in X-rays. This suggests that in the optical we see only the brightest central part of the torus nebula with the pulsar. The position and morphology of the object are also practically identical to the counterpart of the torus region recently detected in the mid-infrared bands. We do not resolve any point-like source within the nebula that could be identified with the pulsar and estimate that the contribution of the pulsar to the observed optical flux is ⪉10%. Using the archival Chandra/ACIS-S data we analyzed the spectrum of the pulsar+nebula X-ray emission extracted from the spatial region constrained by the optical/infrared source position and extent and find that a single absorbed power law provides an acceptable spectral fit. Combining this fit with the optical and infrared fluxes of the detected candidate torus nebula counterpart, we compile a tentative multi-wavelength spectrum of the central part of the pulsar nebula. Within the uncertainties of the interstellar extinction towards 3C 58, it is reminiscent of either the Crab or PSR B0540-69 pulsar wind nebula spectra. Conclusions: The position, morphology, and spectral properties of the detected source strongly suggest that it is the optical/mid-infrared counterpart of the 3C 58 pulsar + its wind nebula system. This makes 3C 58 the third member, together with the Crab and PSR B0540-69, of such a system as identified in the optical and mid-infrared.

Keyword
ISM: supernova remnants, stars: pulsars: individual: 3C 58, stars: neutron
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-18313 (URN)10.1051/0004-6361:200809573 (DOI)
Available from: 2009-01-25 Created: 2009-01-25 Last updated: 2012-08-28Bibliographically approved
4. Spectral evolution and polarization of variable structures in the pulsar wind nebula of PSR B0540-69.3
Open this publication in new window or tab >>Spectral evolution and polarization of variable structures in the pulsar wind nebula of PSR B0540-69.3
Show others...
2011 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 413, no 1, 611-627 p.Article in journal (Refereed) Published
Abstract [en]

We present high spatial resolution optical imaging and polarization observations of the PSR B0540-69.3 and its highly dynamical pulsar wind nebula (PWN) performed with Hubble Space Telescope, and compare them with X-ray data obtained with the Chandra X-ray Observatory. In particular, we have studied the bright region south-west of the pulsar where a bright 'blob' is seen in 1999. In a recent paper by De Luca et al. it was argued that the 'blob' moves away from the pulsar at high speed. We show that it may instead be a result of local energy deposition around 1999, and that the emission from this then faded away rather than moved outward. Polarization data from 2007 show that the polarization properties show dramatic spatial variations at the 1999 blob position arguing for a local process. Several other positions along the pulsar-'blob' orientation show similar changes in polarization, indicating previous recent local energy depositions. In X-rays, the spectrum steepens away from the 'blob' position, faster orthogonal to the pulsar-'blob' direction than along this axis of orientation. This could indicate that the pulsar-'blob' orientation is an axis along where energy in the PWN is mainly injected, and that this is then mediated to the filaments in the PWN by shocks. We highlight this by constructing an [S ii]-to-[O iii]-ratio map, and comparing this to optical continuum and X-ray emission maps. We argue, through modelling, that the high [S ii]/[O iii] ratio is not due to time-dependent photoionization caused by possible rapid X-ray emission variations in the 'blob' region. We have also created a multiwavelength energy spectrum for the 'blob' position showing that one can, to within 2 Sigma, connect the optical and X-ray emission by a single power law. The slope of that power law (defined from <file name=mnr_18159_mu1.gif type=gif/>) would be alpha(nu) = 0.74 +/- 0.03, which is marginally different from the X-ray spectral slope alone with alpha(nu) = 0.65 +/- 0.03. A single power law for most of the PWN is, however, not be possible. We obtain best power-law fits for the X-ray spectrum if we include 'extra' oxygen, in addition to the oxygen column density in the interstellar gas of the Large Magellanic Cloud and the Milky Way. This oxygen is most naturally explained by the oxygen-rich ejecta of the supernova remnant. The oxygen needed likely places the progenitor mass in the 20-25 M(circle dot) range, i.e. in the upper mass range for progenitors of Type IIP supernovae.

Keyword
pulsars: individual: PSR B0540-69.3, supernovae: general, ISM: individual objects: SNR 0540-69.3, ISM: supernova remnants, Magellanic Clouds
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-68538 (URN)10.1111/j.1365-2966.2010.18159.x (DOI)000289525000045 ()
Note

authorCount :7

Available from: 2012-01-04 Created: 2012-01-04 Last updated: 2017-12-08Bibliographically approved

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Citation style
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