Pub Date : 2010-04-01DOI: 10.1142/9789814304887_0003
D. Blaschke, T. Klähn, F. Weber
Depending on the density reached in the cores of neutron stars, such objects may contain stable phases of novel matter found nowhere else in the Universe. This article gives a brief overview of these phases of matter and discusses astrophysical constraints on the high-density equation of state associated with ultra-dense nuclear matter.
{"title":"Constraints on the Nuclear EOS from Neutron Star Observables","authors":"D. Blaschke, T. Klähn, F. Weber","doi":"10.1142/9789814304887_0003","DOIUrl":"https://doi.org/10.1142/9789814304887_0003","url":null,"abstract":"Depending on the density reached in the cores of neutron stars, such objects may contain stable phases of novel matter found nowhere else in the Universe. This article gives a brief overview of these phases of matter and discusses astrophysical constraints on the high-density equation of state associated with ultra-dense nuclear matter.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81852944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-01-01DOI: 10.1051/0004-6361:200810897
M. Kopernika
Context. The PICsIT detector onboard the INTEGRAL satellite was designed to provide information about emission in the soft γ-ray band for many bright sources. Due to strong and variable instrumental background, only 4 objects have been detected so far using standard software. Aims. The moderate sensitivity of PICsIT can be compensated for in the case of many objects by adopting a long exposure time, thanks to INTEGRAL’s large field of view and an observing strategy focused on the Galactic plane. With angular resolution far higher than that of all other instruments operating in a similar energy band, PICsIT is suitable for fields too crowded or too significantly affected by Galactic diffuse emission. Therefore, it is desirable to improve the spectral extraction software to both obtain more reliable results and enlarge the number of objects that can be studied. Methods. The new PICsIT spectral extraction method is based on three elements: careful modelling of the background, an energydependent pixel-illumination function, and the computation of the probability density of the source count rate. Background maps of the detector plane are prepared for short periods and relatively narrow energy bands to insure that the background dependence on time and energy is modelled well. The most important element of the new spectral extraction method is the proper treatment of the Poisson-distributed data, developed within a Bayesian framework. Results. The new method was tested extensively on both a large true data set and simulated data. Results assumed in simulations were reproduced perfectly, without any bias and with high precision. Count rates measured for Crab were far more stable than those obtained with the standard software. For weaker sources, the new method produced spectra of far higher quality and allows us to detect at least 8 additional objects. Comparison with other INTEGRAL instruments demonstrated that PICsIT is well calibrated and provides valuable information about the continuum emission in the 250 keV – 1 MeV band, detectable currently only by INTEGRAL.
{"title":"Analysis of extremely low signal-to-noise ratio data from INTEGRAL/PICsIT","authors":"M. Kopernika","doi":"10.1051/0004-6361:200810897","DOIUrl":"https://doi.org/10.1051/0004-6361:200810897","url":null,"abstract":"Context. The PICsIT detector onboard the INTEGRAL satellite was designed to provide information about emission in the soft γ-ray band for many bright sources. Due to strong and variable instrumental background, only 4 objects have been detected so far using standard software. Aims. The moderate sensitivity of PICsIT can be compensated for in the case of many objects by adopting a long exposure time, thanks to INTEGRAL’s large field of view and an observing strategy focused on the Galactic plane. With angular resolution far higher than that of all other instruments operating in a similar energy band, PICsIT is suitable for fields too crowded or too significantly affected by Galactic diffuse emission. Therefore, it is desirable to improve the spectral extraction software to both obtain more reliable results and enlarge the number of objects that can be studied. Methods. The new PICsIT spectral extraction method is based on three elements: careful modelling of the background, an energydependent pixel-illumination function, and the computation of the probability density of the source count rate. Background maps of the detector plane are prepared for short periods and relatively narrow energy bands to insure that the background dependence on time and energy is modelled well. The most important element of the new spectral extraction method is the proper treatment of the Poisson-distributed data, developed within a Bayesian framework. Results. The new method was tested extensively on both a large true data set and simulated data. Results assumed in simulations were reproduced perfectly, without any bias and with high precision. Count rates measured for Crab were far more stable than those obtained with the standard software. For weaker sources, the new method produced spectra of far higher quality and allows us to detect at least 8 additional objects. Comparison with other INTEGRAL instruments demonstrated that PICsIT is well calibrated and provides valuable information about the continuum emission in the 250 keV – 1 MeV band, detectable currently only by INTEGRAL.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2009-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72678141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We recalibrate a standard solar model seismologically to estimate the main-sequence age of the Sun. Our procedure differs from what we have done in the past by removing from the observed frequencies the effect of hydrogen ionization and the superadiabatic convective boundary layer. Our preliminary result is $t_odot=4.63 pm 0.02$ Gy.
{"title":"Further progress on solar age calibration","authors":"G. Houdek, D. Gough","doi":"10.1553/cia159s27","DOIUrl":"https://doi.org/10.1553/cia159s27","url":null,"abstract":"We recalibrate a standard solar model seismologically to estimate the main-sequence age of the Sun. Our procedure differs from what we have done in the past by removing from the observed frequencies the effect of hydrogen ionization and the superadiabatic convective boundary layer. Our preliminary result is $t_odot=4.63 pm 0.02$ Gy.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91049662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The new generation of 8 to 10 m class telescope is providing us with high‐quality spectral information on the rest‐frame ultraviolet region of star‐forming galaxies at cosmological distances. The data can be used to address questions such as, e.g., the star‐formation histories, the stellar initial mass function, the dust properties, and the energetics and chemistry of the interstellar medium. We can tackle these issues from a different angle by comparing the spectral properties of high‐redshift galaxies to those of their counterparts in the local universe. I give a review of recent developments related to observations and empirical modeling of the ultraviolet spectra of local galaxies with recent star formation. The emphasis is on the youngest stellar populations with ages less than 100 Myr. Current uncertainties will be discussed, and areas where progress is needed in the future are highlighted.
{"title":"Ultraviolet Spectra of Local Galaxies and their Link with the High‐z Population","authors":"C. Leitherer","doi":"10.1063/1.3141539","DOIUrl":"https://doi.org/10.1063/1.3141539","url":null,"abstract":"The new generation of 8 to 10 m class telescope is providing us with high‐quality spectral information on the rest‐frame ultraviolet region of star‐forming galaxies at cosmological distances. The data can be used to address questions such as, e.g., the star‐formation histories, the stellar initial mass function, the dust properties, and the energetics and chemistry of the interstellar medium. We can tackle these issues from a different angle by comparing the spectral properties of high‐redshift galaxies to those of their counterparts in the local universe. I give a review of recent developments related to observations and empirical modeling of the ultraviolet spectra of local galaxies with recent star formation. The emphasis is on the youngest stellar populations with ages less than 100 Myr. Current uncertainties will be discussed, and areas where progress is needed in the future are highlighted.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82122504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We discuss bulk viscosity due to non-leptonic processes involving hyperons and Bose-Einstein condensate of negatively charged kaons in neutron stars. It is noted that the hyperon bulk viscosity coefficient is a few order of magnitude larger than that of the case with the condensate. Further it is found that the hyperon bulk viscosity is suppressed in a superconducting phase. The hyperon bulk viscosity efficiently damps the r-mode instability in neutron stars irrespective of whether a superconducting phase is present or not in neutron star interior.
{"title":"Bulk viscosity of strange matter and r-modes in neutron stars","authors":"D. Chatterjee, D. Bandyopadhyay","doi":"10.22323/1.053.0181","DOIUrl":"https://doi.org/10.22323/1.053.0181","url":null,"abstract":"We discuss bulk viscosity due to non-leptonic processes involving hyperons and Bose-Einstein condensate of negatively charged kaons in neutron stars. It is noted that the hyperon bulk viscosity coefficient is a few order of magnitude larger than that of the case with the condensate. Further it is found that the hyperon bulk viscosity is suppressed in a superconducting phase. The hyperon bulk viscosity efficiently damps the r-mode instability in neutron stars irrespective of whether a superconducting phase is present or not in neutron star interior.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80950630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Europa is believed to have formed near the very end of Jupiter's own accretion, within a circumplanetary disk of gas and solid particles. We review the formation of the Galilean satellites in the context of current constraints and understanding of giant planet formation, focusing on recent models of satellite growth within a circumjovian accretion disk produced during the final stages of gas inflow to Jupiter. In such a disk, the Galilean satellites would have accreted slowly, in more than 10^5 yr, and in a low pressure, low gas density environment. Gravitational interactions between the satellites and the gas disk lead to inward orbital migration and loss of satellites to Jupiter. Such effects tend to select for a maximum satellite mass and a common total satellite system mass compared to the planet's mass. One implication is that multiple satellite systems may have formed and been lost during the final stages of Jupiter's growth, with the Galilean satellites being the last generation that survived as gas inflow to Jupiter ended. We conclude by discussing open issues and implications for Europa's conditions of formation.
{"title":"Origin of Europa and the Galilean Satellites","authors":"R. Canup, W. Ward","doi":"10.2307/j.ctt1xp3wdw.9","DOIUrl":"https://doi.org/10.2307/j.ctt1xp3wdw.9","url":null,"abstract":"Europa is believed to have formed near the very end of Jupiter's own accretion, within a circumplanetary disk of gas and solid particles. We review the formation of the Galilean satellites in the context of current constraints and understanding of giant planet formation, focusing on recent models of satellite growth within a circumjovian accretion disk produced during the final stages of gas inflow to Jupiter. In such a disk, the Galilean satellites would have accreted slowly, in more than 10^5 yr, and in a low pressure, low gas density environment. Gravitational interactions between the satellites and the gas disk lead to inward orbital migration and loss of satellites to Jupiter. Such effects tend to select for a maximum satellite mass and a common total satellite system mass compared to the planet's mass. One implication is that multiple satellite systems may have formed and been lost during the final stages of Jupiter's growth, with the Galilean satellites being the last generation that survived as gas inflow to Jupiter ended. We conclude by discussing open issues and implications for Europa's conditions of formation.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73440289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Pignata, J. Maza, M. Hamuy, R. Antezana, L. González, P. Gonzalez, P. López, S. Silva, G. Folatelli, D. Iturra, R. Cartier, F. Förster, B. Conuel, Daniel E. Reichart, K. Ivarsen, A. Crain, D. Foster, M. Nysewander, A. Lacluyze
The CHASE project started in 2007 with the aim of providing young southern supernovae (SNe) to the Carnegie Supernova Project (CSP) and Millennium Center for Supernova Studies (MCSS) follow‐up programs. So far CHASE has discovered 33 SNe with an average of more than 2.5 SNe per month in 2008. In addition to the search we are carrying out a follow‐up program targeting bright SNe. Our fully automated data reduction allows us to follow the evolution on the light curve in real time, triggering further observations if something potentially interesting is detected.
{"title":"The CHilean Automatic Supernova sEarch (CHASE)","authors":"G. Pignata, J. Maza, M. Hamuy, R. Antezana, L. González, P. Gonzalez, P. López, S. Silva, G. Folatelli, D. Iturra, R. Cartier, F. Förster, B. Conuel, Daniel E. Reichart, K. Ivarsen, A. Crain, D. Foster, M. Nysewander, A. Lacluyze","doi":"10.1063/1.3141608","DOIUrl":"https://doi.org/10.1063/1.3141608","url":null,"abstract":"The CHASE project started in 2007 with the aim of providing young southern supernovae (SNe) to the Carnegie Supernova Project (CSP) and Millennium Center for Supernova Studies (MCSS) follow‐up programs. So far CHASE has discovered 33 SNe with an average of more than 2.5 SNe per month in 2008. In addition to the search we are carrying out a follow‐up program targeting bright SNe. Our fully automated data reduction allows us to follow the evolution on the light curve in real time, triggering further observations if something potentially interesting is detected.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89034284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A new approach to extraction of quantum vacuum energy, in the context of the accelerated expansion, is proposed, and it is shown that experimentally realistic orders of values can be derived. The idea has been implemented in the framework of the Friedmann-Lemaitre-Robertson-Walker geometry in the language of the effective action in the relativistic formalism of Schwinger's proper time and Seeley-DeWitt's heat kernel expansion.
{"title":"Quantum vacuum and accelerated expansion","authors":"B. Broda, M. Szanecki","doi":"10.1051/eas/0936024","DOIUrl":"https://doi.org/10.1051/eas/0936024","url":null,"abstract":"A new approach to extraction of quantum vacuum energy, in the context of the accelerated expansion, is proposed, and it is shown that experimentally realistic orders of values can be derived. The idea has been implemented in the framework of the Friedmann-Lemaitre-Robertson-Walker geometry in the language of the effective action in the relativistic formalism of Schwinger's proper time and Seeley-DeWitt's heat kernel expansion.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76403612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A new line of research on Dark Stars is reviewed, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion. Weakly Interacting Massive Particles, which may be there own antipartmers, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel.
{"title":"Dark Stars: the First Stars in the Universe may be powered by Dark Matter Heating","authors":"K. Freese, P. Bodenheimer, P. Gondolo, D. Spolyar","doi":"10.1063/1.3232192","DOIUrl":"https://doi.org/10.1063/1.3232192","url":null,"abstract":"A new line of research on Dark Stars is reviewed, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion. Weakly Interacting Massive Particles, which may be there own antipartmers, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75240323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present some results of an observational and theoretical study on unresolved stellar systems based on the Surface Brightness Fluctuations (SBF) technique. It is shown that SBF magnitudes are a valuable tracer of stellar population properties, and a reliable distance indicator. SBF magnitudes, SBF‐colors, and SBF‐gradients can help to constrain within relatively narrow limits the metallicity and age of the dominant stellar component in distant stellar systems, especially if coupled with other spectro‐photometric indicators.
{"title":"Disentangling age and metallicity in distant unresolved stellar systems","authors":"M. Cantiello, E. Brocato, G.Raimondo","doi":"10.1063/1.3141573","DOIUrl":"https://doi.org/10.1063/1.3141573","url":null,"abstract":"We present some results of an observational and theoretical study on unresolved stellar systems based on the Surface Brightness Fluctuations (SBF) technique. It is shown that SBF magnitudes are a valuable tracer of stellar population properties, and a reliable distance indicator. SBF magnitudes, SBF‐colors, and SBF‐gradients can help to constrain within relatively narrow limits the metallicity and age of the dominant stellar component in distant stellar systems, especially if coupled with other spectro‐photometric indicators.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85616339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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