The extended nebulae formed as pulsar winds expand into their surroundings provide information about the composition of the winds, the injection history from the host pulsar, and the material into which the nebulae are expanding. Observations from across the electromagnetic spectrum provide constraints on the evolution of the nebulae, the density and composition of the surrounding ejecta, the geometry of the systems, the formation of jets, and the maximum energy of the particles in the nebulae. Here I provide a broad overview of the structure of pulsar wind nebulae, with specific examples that demonstrate our ability to constrain the above parameters. The association of pulsar wind nebulae with extended sources of very high energy gamma‐ray emission are investigated, along with constraints on the nature of such high energy emission.
{"title":"High Energy Studies of Pulsar Wind Nebulae","authors":"P. Slane","doi":"10.1063/1.3076627","DOIUrl":"https://doi.org/10.1063/1.3076627","url":null,"abstract":"The extended nebulae formed as pulsar winds expand into their surroundings provide information about the composition of the winds, the injection history from the host pulsar, and the material into which the nebulae are expanding. Observations from across the electromagnetic spectrum provide constraints on the evolution of the nebulae, the density and composition of the surrounding ejecta, the geometry of the systems, the formation of jets, and the maximum energy of the particles in the nebulae. Here I provide a broad overview of the structure of pulsar wind nebulae, with specific examples that demonstrate our ability to constrain the above parameters. The association of pulsar wind nebulae with extended sources of very high energy gamma‐ray emission are investigated, along with constraints on the nature of such high energy emission.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81895290","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}
J. Desmurs, C. Codella, J. Santiago-García, M. Tafalla, R. Bachiller
We imaged the protostars of the nearby region NGC1333 IRAS 4 in the water maser line at 22.2 GHz by using the VLBA in phase referencing at milliarcsecond scale over four epochs spaced by one month to measure proper motions. We measure the absolute positions and proper motions of the H2O spots to investigate the kinematics of the region from where the jet is launched. Two protostars (A2 and B) have been detected in a highly variable H2O maser emission, with an active phase shorter than four weeks. A 70 AU chain of several maser spots, very well aligned, has been observed close to the B protostar. The apparent proper motions have been derived, finding that the H2O spots are moving along the N-NW direction with projected velocities between 10 and 50 km/s. We conclude that in IRAS 4B, water maser trace a highly collimated bipolar jet clearly associated with the protostar.
{"title":"A highly collimated jet from the low mass proto-star NGC1333 IRAS 4B","authors":"J. Desmurs, C. Codella, J. Santiago-García, M. Tafalla, R. Bachiller","doi":"10.22323/1.072.0071","DOIUrl":"https://doi.org/10.22323/1.072.0071","url":null,"abstract":"We imaged the protostars of the nearby region NGC1333 IRAS 4 in the water maser line at 22.2 GHz by using the VLBA in phase referencing at milliarcsecond scale over four epochs spaced by one month to measure proper motions. We measure the absolute positions and proper motions of the H2O spots to investigate the kinematics of the region from where the jet is launched. \u0000Two protostars (A2 and B) have been detected in a highly variable H2O maser emission, with an active phase shorter than four weeks. A 70 AU chain of several maser spots, very well aligned, has been observed close to the B protostar. The apparent proper motions have been derived, finding that the H2O spots are moving along the N-NW direction with projected velocities between 10 and 50 km/s. We conclude that in IRAS 4B, water maser trace a highly collimated bipolar jet clearly associated with the protostar.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79236708","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 : 2008-11-11DOI: 10.1088/1126-6708/2009/03/082
R. Akhoury, C. Gauthier, A. Vikman
In this paper we show that, for general scalar fields, stationary configurations are possible for shift symmetric theories only. This symmetry with respect to constant translations in field space should either be manifest in the original field variables or reveal itself after an appropriate field redefinition. In particular this result implies that neither k-Essence nor Quintessence can have exact steady state / Bondi accretion onto Black Holes. We also discuss the role of field redefinitions in k-Essence theories. Here we study the transformation properties of observables and other variables in k-Essence and emphasize which of them are covariant under field redefinitions. Finally we find that stationary field configurations are necessarily linear in Killing time, provided that shift symmetry is realized in terms of these field variables.
{"title":"Stationary Configurations Imply Shift Symmetry: No Bondi Accretion for Quintessence / k-Essence","authors":"R. Akhoury, C. Gauthier, A. Vikman","doi":"10.1088/1126-6708/2009/03/082","DOIUrl":"https://doi.org/10.1088/1126-6708/2009/03/082","url":null,"abstract":"In this paper we show that, for general scalar fields, stationary configurations are possible for shift symmetric theories only. This symmetry with respect to constant translations in field space should either be manifest in the original field variables or reveal itself after an appropriate field redefinition. In particular this result implies that neither k-Essence nor Quintessence can have exact steady state / Bondi accretion onto Black Holes. We also discuss the role of field redefinitions in k-Essence theories. Here we study the transformation properties of observables and other variables in k-Essence and emphasize which of them are covariant under field redefinitions. Finally we find that stationary field configurations are necessarily linear in Killing time, provided that shift symmetry is realized in terms of these field variables.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89838799","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}
R. Dunn, R. Fender, E. Koerding, C. Cabanac, Tomaso Belloni University of Southampton, I. Brera
We present preliminary results on a global study of X-ray binaries using 14 Ms of data from the Rossi X-ray Timing Explorer satellite. Our initial study on GX 339-4 is recapped as an introduction to the methods used. We use a consistent analysis scheme for all objects, with three different spectral models to fit the powerlaw and disc components. We also take into account the possibility of a line being present in the data. The resulting almost 4000 observations allow the tracking of the spectral properties of the binaries as they evolve through an outburst. Our investigations concentrate on the disc and line properties of the binaries when in outburst. We also show the Disc-Fraction Luminosity diagram for the population of X-ray binaries studied which will enable us to further links with AGN.
{"title":"A Global Study of X-ray Binaries","authors":"R. Dunn, R. Fender, E. Koerding, C. Cabanac, Tomaso Belloni University of Southampton, I. Brera","doi":"10.22323/1.062.0008","DOIUrl":"https://doi.org/10.22323/1.062.0008","url":null,"abstract":"We present preliminary results on a global study of X-ray binaries using 14 Ms of data from the Rossi X-ray Timing Explorer satellite. Our initial study on GX 339-4 is recapped as an introduction to the methods used. We use a consistent analysis scheme for all objects, with three different spectral models to fit the powerlaw and disc components. We also take into account the possibility of a line being present in the data. The resulting almost 4000 observations allow the tracking of the spectral properties of the binaries as they evolve through an outburst. Our investigations concentrate on the disc and line properties of the binaries when in outburst. We also show the Disc-Fraction Luminosity diagram for the population of X-ray binaries studied which will enable us to further links with AGN.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87226543","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 : 2008-11-10DOI: 10.1063/1.3099271 10.1088/1742-6596/172/1/012023
R. Heller, D. Homeier, S. Dreizler, Roy Ostensen Hamburger Sternwarte, U. Hamburg, I. F. Astrophysik, Georg-August-Universitat Gottingen, I. O. Astronomy, K. Leuven
We present a catalog of 857 white dwarf (WD)-M binaries from the sixth data release (DR6) of the Sloan Digital Sky Survey (SDSS), most of which were previously identified. For 636 of them, we complete a spectral analysis and derive the basic parameters of their stellar constituents and their distances from Earth. We attempt to measure fundamental parameters of these systems by completing spectral analyses. We use a Chi^2 minimization technique to decompose each combined spectrum and derive independent parameter estimates for its components. Forty-one of the stellar duets in our spectroscopic sample are optically resolved in their respective SDSS images. For these systems, we also derive a minimum true spatial separation and a lower limit to their orbital periods, typically which are some 10^4 yr. Spectra of 167 stellar duets show significant hydrogen emission and in most cases no additional He i or He ii features. We also find that 20 of the 636 WDs are fitted to be DOs, with 16 measured to have T_eff around 40,000 K. Furthermore, we identify 70 very low-mass objects, which are secondaries of masses smaller than about 0.1 solar masses, to be candidate substellar companions. Although various selection effects may play a role, the fraction 6.4 % of WD-M star binaries with orbital separations of around 500 AU is a criterion for evolutionary models of stellar binary systems. Active M dwarfs are likely present in 155 Balmer-emitting systems, corresponding to a fraction of 24.4 %. The excess of cool DOs is most likely due to additional WDs in the DB-DO T_eff range, for which no detailed fitting was completed. The trend of the M stars being closer to Earth than the WD component is probably due to an underestimation of the theoretical M star radii.
{"title":"Spectral analysis of 636 white dwarf - M star binaries from the Sloan Digital Sky Survey","authors":"R. Heller, D. Homeier, S. Dreizler, Roy Ostensen Hamburger Sternwarte, U. Hamburg, I. F. Astrophysik, Georg-August-Universitat Gottingen, I. O. Astronomy, K. Leuven","doi":"10.1063/1.3099271 10.1088/1742-6596/172/1/012023","DOIUrl":"https://doi.org/10.1063/1.3099271 10.1088/1742-6596/172/1/012023","url":null,"abstract":"We present a catalog of 857 white dwarf (WD)-M binaries from the sixth data release (DR6) of the Sloan Digital Sky Survey (SDSS), most of which were previously identified. For 636 of them, we complete a spectral analysis and derive the basic parameters of their stellar constituents and their distances from Earth. We attempt to measure fundamental parameters of these systems by completing spectral analyses. We use a Chi^2 minimization technique to decompose each combined spectrum and derive independent parameter estimates for its components. Forty-one of the stellar duets in our spectroscopic sample are optically resolved in their respective SDSS images. For these systems, we also derive a minimum true spatial separation and a lower limit to their orbital periods, typically which are some 10^4 yr. Spectra of 167 stellar duets show significant hydrogen emission and in most cases no additional He i or He ii features. We also find that 20 of the 636 WDs are fitted to be DOs, with 16 measured to have T_eff around 40,000 K. Furthermore, we identify 70 very low-mass objects, which are secondaries of masses smaller than about 0.1 solar masses, to be candidate substellar companions. Although various selection effects may play a role, the fraction 6.4 % of WD-M star binaries with orbital separations of around 500 AU is a criterion for evolutionary models of stellar binary systems. Active M dwarfs are likely present in 155 Balmer-emitting systems, corresponding to a fraction of 24.4 %. The excess of cool DOs is most likely due to additional WDs in the DB-DO T_eff range, for which no detailed fitting was completed. The trend of the M stars being closer to Earth than the WD component is probably due to an underestimation of the theoretical M star radii.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84861952","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 : 2008-11-10DOI: 10.1051/0004-6361:200810919
J. Ebrero, J. Ebrero, F. J. Carrera, M. Page, J. Silverman, X. Barcons, M. Ceballos, A. Corral, Amalia Corral, R. Ceca, M. Watson
We present the X-ray luminosity function of AGN in three energy bands (Soft: 0.5-2 keV, Hard: 2-10 keV and Ultrahard: 4.5-7.5 keV). We have used the XMS survey along with other highly complete flux-limited deeper and shallower surveys for a total of 1009, 435 and 119 sources in the Soft, Hard and Ultrahard bands, respectively. We have modeled the intrinsic absorption of the Hard and Ultrahard sources (NH function) and computed the intrinsic X-ray luminosity function in all bands using a Maximum Likelihood fit technique to an analytical model. We find that the X-ray luminosity function (XLF) is best described by a Luminosity-Dependent Density Evolution (LDDE) model. Our results show a good overall agreement with previous results in the Hard band, although with slightly weaker evolution. Our model in the Soft band present slight discrepancies with other works in this band, the shape of our present day XLF being significantly flatter. We find faster evolution in the AGN detected in the Ultrahard band than those in the Hard band. The fraction of absorbed AGN in the Hard and Ultrahard bands is dependent on the X-ray luminosity. We find evidence of evolution of this fraction with redshift in the Hard band but not in the Ultrahard band, possibly due to the low statistics. Our best-fit XLF shows that the high-luminosity AGN are fully formed earlier than the less luminous AGN. The latter sources account for the vast majority of the accretion rate and mass density of the Universe, according to an anti-hierarchical black hole growth scenario.
{"title":"The XMM-Newton Serendipitous Survey. VI. The X-ray Luminosity Function","authors":"J. Ebrero, J. Ebrero, F. J. Carrera, M. Page, J. Silverman, X. Barcons, M. Ceballos, A. Corral, Amalia Corral, R. Ceca, M. Watson","doi":"10.1051/0004-6361:200810919","DOIUrl":"https://doi.org/10.1051/0004-6361:200810919","url":null,"abstract":"We present the X-ray luminosity function of AGN in three energy bands (Soft: 0.5-2 keV, Hard: 2-10 keV and Ultrahard: 4.5-7.5 keV). We have used the XMS survey along with other highly complete flux-limited deeper and shallower surveys for a total of 1009, 435 and 119 sources in the Soft, Hard and Ultrahard bands, respectively. We have modeled the intrinsic absorption of the Hard and Ultrahard sources (NH function) and computed the intrinsic X-ray luminosity function in all bands using a Maximum Likelihood fit technique to an analytical model. We find that the X-ray luminosity function (XLF) is best described by a Luminosity-Dependent Density Evolution (LDDE) model. Our results show a good overall agreement with previous results in the Hard band, although with slightly weaker evolution. Our model in the Soft band present slight discrepancies with other works in this band, the shape of our present day XLF being significantly flatter. We find faster evolution in the AGN detected in the Ultrahard band than those in the Hard band. The fraction of absorbed AGN in the Hard and Ultrahard bands is dependent on the X-ray luminosity. We find evidence of evolution of this fraction with redshift in the Hard band but not in the Ultrahard band, possibly due to the low statistics. Our best-fit XLF shows that the high-luminosity AGN are fully formed earlier than the less luminous AGN. The latter sources account for the vast majority of the accretion rate and mass density of the Universe, according to an anti-hierarchical black hole growth scenario.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80756879","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. Moretti, C. Pagani, G. Cusumano, S. Campana, M. Perri, A. Abbey, M. Ajello, A. Beardmore, D. Burrows, G. Chincarini, O. Godet, C. Guidorzi, J. Hill, J. Kennea, J. Nousek, J. Osborne, G. Tagliaferri
I present a new analytical description of the cosmic X‐ray background (CXRB) spectrum in the 1.5–200 keV energy band, obtained by combining the new measurement performed by the Swift X‐ray telescope (XRT) with the recently published Swift burst alert telescope (BAT) measurement. A study of the cosmic variance in the XRT band (1.5–7 keV) is also presented. I find that the expected cosmic variance (expected from LogN‐LogS) scales as Ω−0.3 (where Ω is the surveyed area) in very good agreement with XRT data.
{"title":"A New Measurement of the Cosmic X‐ray Background","authors":"A. Moretti, C. Pagani, G. Cusumano, S. Campana, M. Perri, A. Abbey, M. Ajello, A. Beardmore, D. Burrows, G. Chincarini, O. Godet, C. Guidorzi, J. Hill, J. Kennea, J. Nousek, J. Osborne, G. Tagliaferri","doi":"10.1063/1.3149419","DOIUrl":"https://doi.org/10.1063/1.3149419","url":null,"abstract":"I present a new analytical description of the cosmic X‐ray background (CXRB) spectrum in the 1.5–200 keV energy band, obtained by combining the new measurement performed by the Swift X‐ray telescope (XRT) with the recently published Swift burst alert telescope (BAT) measurement. A study of the cosmic variance in the XRT band (1.5–7 keV) is also presented. I find that the expected cosmic variance (expected from LogN‐LogS) scales as Ω−0.3 (where Ω is the surveyed area) in very good agreement with XRT data.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89803539","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 the results of a combination of new stellar rotation periods and extensive information about membership in the young open clusters M 35 and M 34. The observations show that late‐type members of both M 35 and M 34 divide into two distinct groups, each with a different dependence of rotation on mass (color). We discuss these new results in the context of existing rotation data for cool stars in older clusters, with a focus on the dependence of rotation on mass and age. We mention briefly tests of rotation as an “astronomical clock” (gyrochronology), and our plans to use the Kepler space mission to push observations of stellar rotation periods beyond the age of the Hyades and the Sun.
{"title":"Young Cool Stars Divided on the Issue of Rotation","authors":"S. Meibom","doi":"10.1063/1.3099279","DOIUrl":"https://doi.org/10.1063/1.3099279","url":null,"abstract":"We present the results of a combination of new stellar rotation periods and extensive information about membership in the young open clusters M 35 and M 34. The observations show that late‐type members of both M 35 and M 34 divide into two distinct groups, each with a different dependence of rotation on mass (color). We discuss these new results in the context of existing rotation data for cool stars in older clusters, with a focus on the dependence of rotation on mass and age. We mention briefly tests of rotation as an “astronomical clock” (gyrochronology), and our plans to use the Kepler space mission to push observations of stellar rotation periods beyond the age of the Hyades and the Sun.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91414406","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 snapshot is presented of the present status of our knowledge of the TeV gamma‐ray universe. Emphasis is put on observations made using the imaging atmospheric Cherenkov technique. The capabilities of the present generation of telescopes is listed. Progress has been dramatic and several features have been different from what was anticipated. The catalog of sources includes some 78 objects and these are tabulated as extragalactic sources (24), supernovae remnants (11), pulsar wind nebulae (10), binaries (4), miscellaneous (9), diffuse high energy sources (3) and unidentified sources (20). Some comments are made on the factors influencing the past and future development of the field.
{"title":"TeV Gamma‐ray Astronomy: The Story So Far","authors":"T. Weekes","doi":"10.1063/1.3076692","DOIUrl":"https://doi.org/10.1063/1.3076692","url":null,"abstract":"A snapshot is presented of the present status of our knowledge of the TeV gamma‐ray universe. Emphasis is put on observations made using the imaging atmospheric Cherenkov technique. The capabilities of the present generation of telescopes is listed. Progress has been dramatic and several features have been different from what was anticipated. The catalog of sources includes some 78 objects and these are tabulated as extragalactic sources (24), supernovae remnants (11), pulsar wind nebulae (10), binaries (4), miscellaneous (9), diffuse high energy sources (3) and unidentified sources (20). Some comments are made on the factors influencing the past and future development of the field.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76707601","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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