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The Crab pulsar and its pulsar-wind nebula in the optical and infrared
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
2009 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 508, no 1, 221-228 p.Article in journal (Refereed) Published
Abstract [en]

Aims. We investigate the emission mechanism and evolution of pulsars that are associated with supernova remnants. Methods: We used imaging techniques in both the optical and near infrared, using images with very good seeing (≤0.primeprime6) to study the immediate surroundings of the Crab pulsar. In the case of the infrared, we took two data sets with a time window of 75 days to check for variability in the inner part of the Crab nebula. We also measure the spectral indices of all these wisps, the nearby knot, and the interwisp medium, using our optical and infrared data. We then compared the observational results with the existing theoretical models. Results: We report variability in the three nearby wisps located to the northwest of the pulsar and also in a nearby anvil wisp in terms of their structure, position, and emissivity within the time window of 75 days. All the wisps display red spectra with similar spectral indices (α_ν = -0.58 ± 0.08, α_ν = -0.63 ± 0.07, α_ν = -0.53 ± 0.08) for the northwest triplet. The anvil wisp (anvil wisp 1) has a spectral index of α_ν = -0.62 ± 0.10. Similarly, the interwisp medium regions also show red spectra similar to those of the wisps, with the spectral index being α_ν = -0.61 ± 0.08, α_ν = -0.50 ± 0.10, while the third interwisp region has a flatter spectrum with spectral α_ν = -0.49 ± 0.10. The inner knot has a spectral index of α_ν = -0.63 ± 0.02. Also, based on archival HST data and our IR data, we find that the inner knot remains stationary for a time period of 13.5 years. The projected average velocity relative to the pulsar for this period is ≲8 ~km s-1. Conclusions: By comparing the spectral indices of the structures in the inner Crab with the current theoretical models, we find that the Del Zanna et al. model for the synchrotron emission fits our observations, although the spectral index is at the flatter end of their modelled spectra.

Place, publisher, year, edition, pages
2009. Vol. 508, no 1, 221-228 p.
Keyword [en]
ISM: supernova remnant
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
URN: urn:nbn:se:su:diva-36487DOI: 10.1051/0004-6361/200912031OAI: oai:DiVA.org:su-36487DiVA: diva2:289518
Note
Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Part of the data presented here have been taken using ALFOSC, which is owned by the Instituto de Astrofisica de Andalucia (IAA) and operated at the Nordic Optical Telescope under an agreement between IAA and the NBIfAFG of the Astronomical Observatory of Copenhagen. Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Observations of young core collapse supernova remnants
Open this publication in new window or tab >>Observations of young core collapse supernova remnants
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Studies of young remnants offer an opportunity to test theoretical models of stellar evolution, explosion models and nucleosynthesis, as well as our understanding of the compact objects in the centre of the exploded stars.

The first part of the thesis involves observations of the Crab nebula. We have used photometric and spectroscopic observations to search for a faint halo around the visible nebula, that could carry the missing mass and kinetic energy of the nebula. No halo was found. In the photometric data due to psf contamination, and in the spectroscopic no fast velocity components were present. We have also used optical and IR photometry to check for variation in the emissivity and dynamic structure of the Crab pulsar wind nebula (PWN), to try to understand the nature of plerionic PWNe. There, we measured flux variations up to 20% in the IR and also shifting of the wisps with velocities up to 0.2c. We also showed that the nearby red knot moves in tandem with the Crab pulsar.

The second part of the thesis, deals with photometric &  spectroscopic observations of SN 1987A in the LMC. The aim of the project was to monitor the evolution of the outer rings (ORs) of SN 1987A. The fading of the ORs is consistent with recombination and cooling after the initial flash ionization by the supernova. From the spectroscopic data we measured the density and temperature in the ORs where we found temperatures of ~ 12,000 K for the [N II] gas, and ~ 25,000 K for the [O III]. Finally, from the [O II], and [S II] ratios we estimated electron densities of ~ 1,000 cm-3 and ~ 2,500 cm-3, respectively. From the evolution of Hα, we argue that the highest density in the ORs could be 5,000 cm-3.

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University, 2011. 63 p.
Keyword
supernova remnants, Crab, SN 1987A
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-58319 (URN)978-91-7447-319-3 (ISBN)
Public defence
2011-10-05, FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.

Available from: 2011-09-13 Created: 2011-05-31 Last updated: 2015-07-29Bibliographically approved

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