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Article: Gamma-ray bursts: Afterglows from cylindrical jets

TitleGamma-ray bursts: Afterglows from cylindrical jets
Authors
KeywordsGamma-rays: bursts
ISM: jets and outflows
Radiation mechanisms: non-thermal
Stars: neutron
Issue Date2001
PublisherBlackwell Publishing Ltd. The Journal's web site is located at http://www.blackwellpublishing.com/journals/MNR
Citation
Monthly Notices Of The Royal Astronomical Society, 2001, v. 325 n. 2, p. 599-606 How to Cite?
AbstractNearly all previous discussions on beaming effects in gamma-ray bursts (GRBs) have assumed a conical geometry. However, more and more observations on relativistic jets in radio galaxies, active galactic nuclei, and 'microquasars' in the Galaxy have shown that many of these outflows are not conical, but cylindrical, i.e. they maintain constant cross-sections at large scales. Thus it is necessary to discuss the possibility of gamma-ray bursts being due to highly collimated cylindrical jets, not conical ones. Here we study the dynamical evolution of cylindrical jets and discuss their afterglows. Both analytical and numerical results are presented. It is shown that when the lateral expansion is not taken into account, a cylindrical jet typically remains highly relativistic for ∼108-109 s. During this relativistic phase, the optical afterglow at first decays as Sv ∝ t-p/2, where p is the index characterizing the power-law energy distribution of electrons. Then the light curve steepens to 5v ∝ t-(p+1)/2 due to cooling of electrons. After entering the non-relativistic phase (i.e. t ≥ 1011 s), the afterglow is Sv ∝ t-(5p-4)/6. However, if the cylindrical jet expands laterally at the comoving sound speed, then the decay becomes Sv ∝ t-p and Sv ∝ t-(15/-21)10 - t-(15p-20)/10 in the ultrarelativistic and in the non-relativistic phase respectively. Note that in both cases the light curve turns flatter after the relativistic-Newtonian transition point, which differs markedly from the behaviour of a conical jet. It is suggested that some GRBs with afterglows decaying as t-1.1-t-1.3 may be due to cylindrical jets, not necessarily isotropic fireballs.
Persistent Identifierhttp://hdl.handle.net/10722/81064
ISSN
2015 Impact Factor: 4.952
2015 SCImago Journal Rankings: 2.806
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorCheng, KSen_HK
dc.contributor.authorHuang, YFen_HK
dc.contributor.authorLu, Ten_HK
dc.date.accessioned2010-09-06T08:13:21Z-
dc.date.available2010-09-06T08:13:21Z-
dc.date.issued2001en_HK
dc.identifier.citationMonthly Notices Of The Royal Astronomical Society, 2001, v. 325 n. 2, p. 599-606en_HK
dc.identifier.issn0035-8711en_HK
dc.identifier.urihttp://hdl.handle.net/10722/81064-
dc.description.abstractNearly all previous discussions on beaming effects in gamma-ray bursts (GRBs) have assumed a conical geometry. However, more and more observations on relativistic jets in radio galaxies, active galactic nuclei, and 'microquasars' in the Galaxy have shown that many of these outflows are not conical, but cylindrical, i.e. they maintain constant cross-sections at large scales. Thus it is necessary to discuss the possibility of gamma-ray bursts being due to highly collimated cylindrical jets, not conical ones. Here we study the dynamical evolution of cylindrical jets and discuss their afterglows. Both analytical and numerical results are presented. It is shown that when the lateral expansion is not taken into account, a cylindrical jet typically remains highly relativistic for ∼108-109 s. During this relativistic phase, the optical afterglow at first decays as Sv ∝ t-p/2, where p is the index characterizing the power-law energy distribution of electrons. Then the light curve steepens to 5v ∝ t-(p+1)/2 due to cooling of electrons. After entering the non-relativistic phase (i.e. t ≥ 1011 s), the afterglow is Sv ∝ t-(5p-4)/6. However, if the cylindrical jet expands laterally at the comoving sound speed, then the decay becomes Sv ∝ t-p and Sv ∝ t-(15/-21)10 - t-(15p-20)/10 in the ultrarelativistic and in the non-relativistic phase respectively. Note that in both cases the light curve turns flatter after the relativistic-Newtonian transition point, which differs markedly from the behaviour of a conical jet. It is suggested that some GRBs with afterglows decaying as t-1.1-t-1.3 may be due to cylindrical jets, not necessarily isotropic fireballs.en_HK
dc.languageengen_HK
dc.publisherBlackwell Publishing Ltd. The Journal's web site is located at http://www.blackwellpublishing.com/journals/MNRen_HK
dc.relation.ispartofMonthly Notices of the Royal Astronomical Societyen_HK
dc.subjectGamma-rays: burstsen_HK
dc.subjectISM: jets and outflowsen_HK
dc.subjectRadiation mechanisms: non-thermalen_HK
dc.subjectStars: neutronen_HK
dc.titleGamma-ray bursts: Afterglows from cylindrical jetsen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0035-8711&volume=325&spage=599&epage=606&date=2001&atitle=Gamma-Ray+Bursts:+Afterglows+from+Cylindrical+Jetsen_HK
dc.identifier.emailCheng, KS: hrspksc@hkucc.hku.hken_HK
dc.identifier.authorityCheng, KS=rp00675en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1046/j.1365-8711.2001.04472.xen_HK
dc.identifier.scopuseid_2-s2.0-0013042918en_HK
dc.identifier.hkuros62290en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0013042918&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume325en_HK
dc.identifier.issue2en_HK
dc.identifier.spage599en_HK
dc.identifier.epage606en_HK
dc.identifier.isiWOS:000170568100017-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridCheng, KS=9745798500en_HK
dc.identifier.scopusauthoridHuang, YF=7501574835en_HK
dc.identifier.scopusauthoridLu, T=7402684810en_HK

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