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Article: Observations of the crab nebula and its pulsar in the far-ultraviolet and in the optical

TitleObservations of the crab nebula and its pulsar in the far-ultraviolet and in the optical
Authors
KeywordsDust, Extinction
Instrumentation: Spectrographs
Pulsars: Individual (Crab Pulsar)
Supernova Remnants
Ultraviolet: Ism
Ultraviolet: Stars
Issue Date2000
PublisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205
Citation
Astrophysical Journal Letters, 2000, v. 537 n. 2 PART 1, p. 861-874 How to Cite?
AbstractWe present far-UV observations of the Crab Nebula and its pulsar made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Broad, blueshifted absorption arising in the nebula is seen in C iv λ1550, reaching a blueward velocity of ∼2500 km s -1. This can be interpreted as evidence for a fast outer shell surrounding the Crab Nebula, and we adopt a spherically symmetric model to constrain the properties of such a shell. From the line profile we find that the density appears to decrease outward in the shell. A likely lower limit to the shell mass is ∼0.3 M ⊙ with an accompanying kinetic energy of ∼1.5 × 10 49 ergs. A fast massive shell with 10 51 ergs cannot be excluded but is less likely if the density profile is much steeper than ρ(R) ∝ R -4 and the maximum velocity is ≲6000 km s -1. The observations cover the region 1140-1720 Å, which is further into the ultraviolet than has previously been obtained for the pulsar. With the time-tag mode of the spectrograph we obtain the pulse profile in this spectral regime. The profile is similar to that previously obtained by us in the near-UV, although the primary peak is marginally narrower. Together with the near-UV data, and new optical data from the Nordic Optical Telescope, our spectrum of the Crab pulsar covers the entire region from 1140 to 9250 Å. Dereddening the spectrum with a standard extinction curve we achieve a flat spectrum for the reddening parameters E(B-V) = 0.52, R = 3.1. This dereddened spectrum of the Crab pulsar can be fitted by a power law with spectral index α v = 0.11 ± 0.04. The main uncertainty in determining the spectral index is the amount and characteristics of the interstellar reddening, and we have investigated the dependence of α v on E(B-V) and R. In the extended emission covered by our 25″ × 0″.5 slit in the far-UV, we detect C IV λ1550 and He IV λ1640 emission lines from the Crab Nebula. Several interstellar absorption lines are detected along the line of sight to the pulsar. The Lyα absorption indicates a column density of (3.0 ± 0.5) × 10 21 cm -2 of neutral hydrogen, which agrees well with our estimate of E(B-V) = 0.52 mag. Other lines show no evidence of severe depletion of metals in atomic gas.
Persistent Identifierhttp://hdl.handle.net/10722/174797
ISSN
2015 Impact Factor: 5.487
2015 SCImago Journal Rankings: 3.369
References

 

DC FieldValueLanguage
dc.contributor.authorSollerman, Jen_US
dc.contributor.authorLundqvist, Pen_US
dc.contributor.authorLindler, Den_US
dc.contributor.authorChevalier, RAen_US
dc.contributor.authorFransson, Cen_US
dc.contributor.authorGull, TRen_US
dc.contributor.authorPun, CSJen_US
dc.contributor.authorSonneborn, Gen_US
dc.date.accessioned2012-11-26T08:47:29Z-
dc.date.available2012-11-26T08:47:29Z-
dc.date.issued2000en_US
dc.identifier.citationAstrophysical Journal Letters, 2000, v. 537 n. 2 PART 1, p. 861-874en_US
dc.identifier.issn2041-8205en_US
dc.identifier.urihttp://hdl.handle.net/10722/174797-
dc.description.abstractWe present far-UV observations of the Crab Nebula and its pulsar made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Broad, blueshifted absorption arising in the nebula is seen in C iv λ1550, reaching a blueward velocity of ∼2500 km s -1. This can be interpreted as evidence for a fast outer shell surrounding the Crab Nebula, and we adopt a spherically symmetric model to constrain the properties of such a shell. From the line profile we find that the density appears to decrease outward in the shell. A likely lower limit to the shell mass is ∼0.3 M ⊙ with an accompanying kinetic energy of ∼1.5 × 10 49 ergs. A fast massive shell with 10 51 ergs cannot be excluded but is less likely if the density profile is much steeper than ρ(R) ∝ R -4 and the maximum velocity is ≲6000 km s -1. The observations cover the region 1140-1720 Å, which is further into the ultraviolet than has previously been obtained for the pulsar. With the time-tag mode of the spectrograph we obtain the pulse profile in this spectral regime. The profile is similar to that previously obtained by us in the near-UV, although the primary peak is marginally narrower. Together with the near-UV data, and new optical data from the Nordic Optical Telescope, our spectrum of the Crab pulsar covers the entire region from 1140 to 9250 Å. Dereddening the spectrum with a standard extinction curve we achieve a flat spectrum for the reddening parameters E(B-V) = 0.52, R = 3.1. This dereddened spectrum of the Crab pulsar can be fitted by a power law with spectral index α v = 0.11 ± 0.04. The main uncertainty in determining the spectral index is the amount and characteristics of the interstellar reddening, and we have investigated the dependence of α v on E(B-V) and R. In the extended emission covered by our 25″ × 0″.5 slit in the far-UV, we detect C IV λ1550 and He IV λ1640 emission lines from the Crab Nebula. Several interstellar absorption lines are detected along the line of sight to the pulsar. The Lyα absorption indicates a column density of (3.0 ± 0.5) × 10 21 cm -2 of neutral hydrogen, which agrees well with our estimate of E(B-V) = 0.52 mag. Other lines show no evidence of severe depletion of metals in atomic gas.en_US
dc.languageengen_US
dc.publisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205en_US
dc.relation.ispartofAstrophysical Journal Lettersen_US
dc.subjectDust, Extinctionen_US
dc.subjectInstrumentation: Spectrographsen_US
dc.subjectPulsars: Individual (Crab Pulsar)en_US
dc.subjectSupernova Remnantsen_US
dc.subjectUltraviolet: Ismen_US
dc.subjectUltraviolet: Starsen_US
dc.titleObservations of the crab nebula and its pulsar in the far-ultraviolet and in the opticalen_US
dc.typeArticleen_US
dc.identifier.emailPun, CSJ: jcspun@hkucc.hku.hken_US
dc.identifier.authorityPun, CSJ=rp00772en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.scopuseid_2-s2.0-0034408911en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0034408911&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume537en_US
dc.identifier.issue2 PART 1en_US
dc.identifier.spage861en_US
dc.identifier.epage874en_US
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridSollerman, J=6603947073en_US
dc.identifier.scopusauthoridLundqvist, P=7004499555en_US
dc.identifier.scopusauthoridLindler, D=7003839081en_US
dc.identifier.scopusauthoridChevalier, RA=7101871369en_US
dc.identifier.scopusauthoridFransson, C=7004051800en_US
dc.identifier.scopusauthoridGull, TR=7007163365en_US
dc.identifier.scopusauthoridPun, CSJ=7003931846en_US
dc.identifier.scopusauthoridSonneborn, G=7006137500en_US

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