The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
N Rea - One of the best experts on this subject based on the ideXlab platform.
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Quiescent State and outburst evolution of sgr 0501 4516
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: A. Camero, N Rea, Alessandro Papitto, Daniele Viganò, José A. Pons, Andrea Tiengo, Sandro MereghettiAbstract:This work was supported by the grants AYA2012-39303, SGR2009-811, and iLINK2011-0303. AP is supported by a Juan de la Cierva Fellowship in IEEC. NR is supported by a Ramon y Cajal fellowship and by an NWO Vidi Award. DV was supported by the grants AYA2010-21097-C03-02, ACOMP/2012/135, AYA 2012-39303 and SGR 2009-811.
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emission geometry radiation pattern and magnetic topology of the magnetar xte j1810 197 in its Quiescent State
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: F Ernardini, Rosalba Perna, E V Gotthelf, G L Israel, N Rea, Luigi StellaAbstract:The return to the Quiescent State of the anomalous X-ray pulsar (AXP) XTE J1810−197 following its 2003 outburst represents a unique opportunity to probe the surface emission properties of a magnetar. The Quiescent emission of XTE J1810−197 is composed of two thermal components, one arising from the whole star surface and the other from a small warm spot on it. By modelling the magnitude and shape of the pulse profile in narrow spectral bands, we have been able to constrain the physical characteristics and geometrical parameters of the system: the two angles that the line of sight and the spin axis make with respect to the warm spot axis (ψ and ξ respectively), the angular size of the spot and the overall surface temperature distribution. Our modelling accounts for the general relativistic effects of gravitational redshift and light bending near the stellar surface, and allows for local anisotropic emission. We found that the surface temperature distribution on the neutron star is consistent with the expectations of a dipole magnetic field configuration; the local radiation requires a pencil-beamed emission pattern, suggesting the presence of a magnetized atmosphere. For a typical value of the radius, R= 13 km, the viewing parameters (symmetric for an interchange between ψ and ξ) range from ψ=ξ= 38° to (ψ, ξ)=(52°, 29°). These angles are consistent with those obtained by modelling the AXP in outburst, with uncertainty contours reduced by a factor of 2.5.
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emission geometry radiation pattern and magnetic topology of the magnetar xte j1810 197 in its Quiescent State
arXiv: High Energy Astrophysical Phenomena, 2011Co-Authors: F Ernardini, Rosalba Perna, E V Gotthelf, G L Israel, N Rea, Luigi StellaAbstract:The return to the Quiescent State of the Anomalous X-ray pulsar XTE J1810-197 following its 2003 outburst represents a unique opportunity to probe the surface emission properties of a magnetar. The Quiescent emission of XTE J1810-197 is composed of two thermal components, one arising from the whole star surface, and the other from a small warm spot on it. By modeling the magnitude and shape of the pulse profile in narrow spectral bands, we have been able to constrain the physical characteristics and geometrical parameters of the system: the two angles that the line of sight and the spin axis make with respect to the warm spot axis (\psi\ and \xi\ respectively), the angular size of the spot, and the overall surface temperature distribution. Our modeling accounts for the general relativistic effects of gravitational redshift and light bending near the stellar surface, and allows for local anisotropic emission. We found that the surface temperature distribution on the neutron star is consistent with the expectations of a dipole magnetic field configuration; the local radiation requires a pencil-beamed emission pattern, suggesting the presence of a magnetized atmosphere. For a typical value of the radius, R=13 km, the viewing parameters (symmetric for an interchange between \psi\ and \xi), range from \psi=\xi=38 deg to (\psi,\xi)=(52 deg, 29 deg). These angles are consistent with those obtained by modeling the AXP in outburst, with uncertainty contours reduced by a factor of 2.5.
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Emission geometry, radiation pattern and magnetic topology of the magnetar XTE J1810−197 in its Quiescent State
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: F. Bernardini, Rosalba Perna, E V Gotthelf, G L Israel, N Rea, Luigi StellaAbstract:The return to the Quiescent State of the anomalous X-ray pulsar (AXP) XTE J1810−197 following its 2003 outburst represents a unique opportunity to probe the surface emission properties of a magnetar. The Quiescent emission of XTE J1810−197 is composed of two thermal components, one arising from the whole star surface and the other from a small warm spot on it. By modelling the magnitude and shape of the pulse profile in narrow spectral bands, we have been able to constrain the physical characteristics and geometrical parameters of the system: the two angles that the line of sight and the spin axis make with respect to the warm spot axis (ψ and ξ respectively), the angular size of the spot and the overall surface temperature distribution. Our modelling accounts for the general relativistic effects of gravitational redshift and light bending near the stellar surface, and allows for local anisotropic emission. We found that the surface temperature distribution on the neutron star is consistent with the expectations of a dipole magnetic field configuration; the local radiation requires a pencil-beamed emission pattern, suggesting the presence of a magnetized atmosphere. For a typical value of the radius, R= 13 km, the viewing parameters (symmetric for an interchange between ψ and ξ) range from ψ=ξ= 38° to (ψ, ξ)=(52°, 29°). These angles are consistent with those obtained by modelling the AXP in outburst, with uncertainty contours reduced by a factor of 2.5.
Luigi Stella - One of the best experts on this subject based on the ideXlab platform.
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emission geometry radiation pattern and magnetic topology of the magnetar xte j1810 197 in its Quiescent State
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: F Ernardini, Rosalba Perna, E V Gotthelf, G L Israel, N Rea, Luigi StellaAbstract:The return to the Quiescent State of the anomalous X-ray pulsar (AXP) XTE J1810−197 following its 2003 outburst represents a unique opportunity to probe the surface emission properties of a magnetar. The Quiescent emission of XTE J1810−197 is composed of two thermal components, one arising from the whole star surface and the other from a small warm spot on it. By modelling the magnitude and shape of the pulse profile in narrow spectral bands, we have been able to constrain the physical characteristics and geometrical parameters of the system: the two angles that the line of sight and the spin axis make with respect to the warm spot axis (ψ and ξ respectively), the angular size of the spot and the overall surface temperature distribution. Our modelling accounts for the general relativistic effects of gravitational redshift and light bending near the stellar surface, and allows for local anisotropic emission. We found that the surface temperature distribution on the neutron star is consistent with the expectations of a dipole magnetic field configuration; the local radiation requires a pencil-beamed emission pattern, suggesting the presence of a magnetized atmosphere. For a typical value of the radius, R= 13 km, the viewing parameters (symmetric for an interchange between ψ and ξ) range from ψ=ξ= 38° to (ψ, ξ)=(52°, 29°). These angles are consistent with those obtained by modelling the AXP in outburst, with uncertainty contours reduced by a factor of 2.5.
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emission geometry radiation pattern and magnetic topology of the magnetar xte j1810 197 in its Quiescent State
arXiv: High Energy Astrophysical Phenomena, 2011Co-Authors: F Ernardini, Rosalba Perna, E V Gotthelf, G L Israel, N Rea, Luigi StellaAbstract:The return to the Quiescent State of the Anomalous X-ray pulsar XTE J1810-197 following its 2003 outburst represents a unique opportunity to probe the surface emission properties of a magnetar. The Quiescent emission of XTE J1810-197 is composed of two thermal components, one arising from the whole star surface, and the other from a small warm spot on it. By modeling the magnitude and shape of the pulse profile in narrow spectral bands, we have been able to constrain the physical characteristics and geometrical parameters of the system: the two angles that the line of sight and the spin axis make with respect to the warm spot axis (\psi\ and \xi\ respectively), the angular size of the spot, and the overall surface temperature distribution. Our modeling accounts for the general relativistic effects of gravitational redshift and light bending near the stellar surface, and allows for local anisotropic emission. We found that the surface temperature distribution on the neutron star is consistent with the expectations of a dipole magnetic field configuration; the local radiation requires a pencil-beamed emission pattern, suggesting the presence of a magnetized atmosphere. For a typical value of the radius, R=13 km, the viewing parameters (symmetric for an interchange between \psi\ and \xi), range from \psi=\xi=38 deg to (\psi,\xi)=(52 deg, 29 deg). These angles are consistent with those obtained by modeling the AXP in outburst, with uncertainty contours reduced by a factor of 2.5.
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Emission geometry, radiation pattern and magnetic topology of the magnetar XTE J1810−197 in its Quiescent State
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: F. Bernardini, Rosalba Perna, E V Gotthelf, G L Israel, N Rea, Luigi StellaAbstract:The return to the Quiescent State of the anomalous X-ray pulsar (AXP) XTE J1810−197 following its 2003 outburst represents a unique opportunity to probe the surface emission properties of a magnetar. The Quiescent emission of XTE J1810−197 is composed of two thermal components, one arising from the whole star surface and the other from a small warm spot on it. By modelling the magnitude and shape of the pulse profile in narrow spectral bands, we have been able to constrain the physical characteristics and geometrical parameters of the system: the two angles that the line of sight and the spin axis make with respect to the warm spot axis (ψ and ξ respectively), the angular size of the spot and the overall surface temperature distribution. Our modelling accounts for the general relativistic effects of gravitational redshift and light bending near the stellar surface, and allows for local anisotropic emission. We found that the surface temperature distribution on the neutron star is consistent with the expectations of a dipole magnetic field configuration; the local radiation requires a pencil-beamed emission pattern, suggesting the presence of a magnetized atmosphere. For a typical value of the radius, R= 13 km, the viewing parameters (symmetric for an interchange between ψ and ξ) range from ψ=ξ= 38° to (ψ, ξ)=(52°, 29°). These angles are consistent with those obtained by modelling the AXP in outburst, with uncertainty contours reduced by a factor of 2.5.
R Wijnands - One of the best experts on this subject based on the ideXlab platform.
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The Quiescent State of the neutron-star X-ray transient GRS 1747-312 in the globular cluster Terzan 6
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Smriti Vats, R Wijnands, N Degenaar, Aastha S. Parikh, L. S. Ootes, Dany PageAbstract:We studied the transient neutron-star low-mass X-ray binary GRS 1747−312, located in the globular cluster Terzan 6, in its Quiescent State after its outburst in August 2004, using an archival XMM–Newton observation. A source was detected in this cluster and its X-ray spectrum can be fitted with the combination of a soft, neutron-star atmosphere model and a hard, power-law model. Both contributed roughly equally to the observed 0.5–10 keV luminosity (∼4.8 × 1033 erg s−1). This type of X-ray spectrum is typically observed for Quiescent neutron-star X-ray transients that are perhaps accreting in quiescence at very low rates. Therefore, if this X-ray source is the Quiescent counterpart of GRS 1747−312, then this source is also accreting at low levels in-between outbursts. Since source confusion is a likely problem in globular clusters, it is quite possible that part, if not all, of the emission we observed is not related to GRS 1747−312, and is instead associated with another source or conglomeration of sources in the cluster. Currently, it is not possible to determine exactly which part of the emission truly originates from GRS 1747−312, and a Chandra observation (when no source is in outburst in Terzan 6) is needed to be conclusive. Assuming that the detected emission is due to GRS 1747−312, we discuss the observed results in the context of what is known about other Quiescent systems. We also investigated the thermal evolution of the neutron star in GRS 1747−312, and inferred that GRS 1747−312 can be considered a typical Quiescent system under our assumptions.
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a low level accretion flare during the Quiescent State of the neutron star x ray transient sax j1750 8 2900
Monthly Notices of the Royal Astronomical Society, 2013Co-Authors: R Wijnands, N DegenaarAbstract:We report on a series of Swift/X-ray telescope observations, performed between 2012 February and 22 March, during the Quiescent State of the neutron-star X-ray binary SAX J1750.8−2900. In these observations, the source was either just detected or undetected, depending on the exposure length (which ranged from ∼0.3 to ∼3.8 ks). The upper limits for the non-detections were consistent with the detected luminosities (when fitting a thermal model to the spectrum) of ∼1034 erg s−1 (0.5-10 keV). This level is consistent with what has been measured previously for this source in quiescence. However, on March 17 the source was found to have an order of magnitude larger count rate. When fitting the flare spectrum with an absorbed power-law model, we obtained a flare luminosity of (3-4) × 1034 erg s−1 (0.5-10 keV). Follow-up Swift observations showed that this flare lasted <16 d. This event was very likely due to a brief episode of low-level accretion on to the neutron star and provides further evidence that the Quiescent State of neutron-star X-ray transients might not be as quiet as is generally assumed. The detection of this low-level accretion flare raises the question whether the Quiescent emission of the source (outside the flare) could also be due to residual accretion, albeit continuous instead of episodic. However, we provide arguments which would suggest that the lowest intensity level might instead represent the cooling of the accretion-heated neutron star.
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A low-level accretion flare during the Quiescent State of the neutron-star X-ray transient SAX J1750.8-2900
Monthly Notices of the Royal Astronomical Society, 2013Co-Authors: R Wijnands, N DegenaarAbstract:We report on a series of Swift/X-ray telescope observations, performed between 2012 February and 22 March, during the Quiescent State of the neutron-star X-ray binary SAX J1750.8−2900. In these observations, the source was either just detected or undetected, depending on the exposure length (which ranged from ∼0.3 to ∼3.8 ks). The upper limits for the non-detections were consistent with the detected luminosities (when fitting a thermal model to the spectrum) of ∼1034 erg s−1 (0.5-10 keV). This level is consistent with what has been measured previously for this source in quiescence. However, on March 17 the source was found to have an order of magnitude larger count rate. When fitting the flare spectrum with an absorbed power-law model, we obtained a flare luminosity of (3-4) × 1034 erg s−1 (0.5-10 keV). Follow-up Swift observations showed that this flare lasted
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Strong X-ray variability in the Quiescent State of the neutron star low-mass X-ray binary EXO 1745-248
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: N Degenaar, R WijnandsAbstract:The transient neutron star low-mass X-ray binary EXO 1745-248, located in the globular cluster Terzan 5, was detected during its Quiescent State with Chandra in 2003. The source displayed a 0.5-10 keV X-ray luminosity of Lq ~ 1E33 (D/5.5kpc)^2 erg/s, which was completely dominated by hard non-thermal emission. This is at odds with other non-pulsating neutron stars that typically show detectable soft thermal emission at such Quiescent luminosities. Here, we use three additional Chandra observations, performed in 2009 and 2011, to further study the Quiescent properties of EXO 1745-248. We find that the powerlaw intensity varies considerably up to a factor of ~3 within hours and by about one order of magnitude between the different epochs. We discuss the implications of the observed change in Quiescent flux for the interpretation of the hard powerlaw emission. Furthermore, we constrain the neutron star surface temperature as seen by a distant observer to kT_inf < 42 eV and the thermal bolometric luminosity to Lq,bol < 7E31 (D/5.5kpc)^2 erg/s. This confirms that EXO 1745-248 harbours a relatively cold neutron star and suggests that, for example, enhanced cooling mechanisms are operating in the stellar core, or that the binary on average resides in quiescence for hundreds of years.
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XTE J1751-305 going back to its Quiescent State
The astronomer's telegram, 2007Co-Authors: Manuel Linares, R Wijnands, M Van Der KlisAbstract:After the recent reports of activity of the accreting millisecond pulsar XTE J1751-305 (ATELs #1045, #1046 and #1051) we obtained another Swift/XRT (~4.3ksec) observation of the field starting on April 11th 2007 23:59. The source was not detected with a 2-10 keV upper limit of ~5E-14 erg/ cm2/s, corresponding to a luminosity of 3.8E32 (d/8kpc)**2 erg/s. This shows that the source decayed further and might have reached quiescence again.
Andrea Tiengo - One of the best experts on this subject based on the ideXlab platform.
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Quiescent State and outburst evolution of SGR 0501+4516
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: A. Camero, Alessandro Papitto, Nanda Rea, Daniele Viganò, José A. Pons, Andrea Tiengo, Sandro Mereghetti, Roberto Turolla, Paolo Esposito, Silvia ZaneAbstract:This work was supported by the grants AYA2012-39303, SGR2009-811, and iLINK2011-0303. AP is supported by a Juan de la Cierva Fellowship in IEEC. NR is supported by a Ramon y Cajal fellowship and by an NWO Vidi Award. DV was supported by the grants AYA2010-21097-C03-02, ACOMP/2012/135, AYA 2012-39303 and SGR 2009-811.
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Quiescent State and outburst evolution of sgr 0501 4516
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: A. Camero, N Rea, Alessandro Papitto, Daniele Viganò, José A. Pons, Andrea Tiengo, Sandro MereghettiAbstract:This work was supported by the grants AYA2012-39303, SGR2009-811, and iLINK2011-0303. AP is supported by a Juan de la Cierva Fellowship in IEEC. NR is supported by a Ramon y Cajal fellowship and by an NWO Vidi Award. DV was supported by the grants AYA2010-21097-C03-02, ACOMP/2012/135, AYA 2012-39303 and SGR 2009-811.
Thomas A Rando - One of the best experts on this subject based on the ideXlab platform.
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Transcriptional Profiling of Quiescent Muscle Stem Cells In Vivo.
Cell reports, 2017Co-Authors: Cindy T. J. Van Velthoven, Antoine De Morrée, Ingrid M. Egner, Jamie O. Brett, Thomas A RandoAbstract:Muscle stem cells (MuSCs) persist in a Quiescent State and activate in response to specific stimuli. The Quiescent State is both actively maintained and dynamically regulated. However, analyses of quiescence have come primarily from cells removed from their niche. Although these cells are still Quiescent, biochemical changes certainly occur during the isolation process. Here, we analyze the transcriptome of MuSCs in vivo utilizing MuSC-specific labeling of RNA. Notably, labeling transcripts during the isolation procedure revealed very active transcription of specific subsets of genes. However, using the transcription inhibitor α-amanitin, we show that the ex vivo transcriptome remains largely reflective of the in vivo transcriptome. Together, these data provide perspective on the molecular regulation of the Quiescent State at the transcriptional level, demonstrate the utility of these tools for probing transcriptional dynamics in vivo, and provide an invaluable resource for understanding stem cell State transitions.
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maintenance of muscle stem cell quiescence by microrna 489
Nature, 2012Co-Authors: Tom H Cheung, Navaline L Quach, Gregory W Charville, Ling Liu, Lidia Park, Abdolhossein Edalati, Bryan B Yoo, Phuong Hoang, Thomas A RandoAbstract:Among the key properties that distinguish adult mammalian stem cells from their more differentiated progeny is the ability of stem cells to remain in a Quiescent State for prolonged periods of time. However, the molecular pathways for the maintenance of stem-cell quiescence remain elusive. Here we use adult mouse muscle stem cells (satellite cells) as a model system and show that the microRNA (miRNA) pathway is essential for the maintenance of the Quiescent State. Satellite cells that lack a functional miRNA pathway spontaneously exit quiescence and enter the cell cycle. We identified quiescence-specific miRNAs in the satellite-cell lineage by microarray analysis. Among these, miRNA-489 (miR-489) is highly expressed in Quiescent satellite cells and is quickly downregulated during satellite-cell activation. Further analysis revealed that miR-489 functions as a regulator of satellite-cell quiescence, as it post-transcriptionally suppresses the oncogene Dek, the protein product of which localizes to the more differentiated daughter cell during asymmetric division of satellite cells and promotes the transient proliferative expansion of myogenic progenitors. Our results provide evidence of the miRNA pathway in general, and of a specific miRNA, miR-489, in actively maintaining the Quiescent State of an adult stem-cell population.
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stem cells in postnatal myogenesis molecular mechanisms of satellite cell quiescence activation and replenishment
Trends in Cell Biology, 2005Co-Authors: Jyotsna Dhawan, Thomas A RandoAbstract:Satellite cells are the primary stem cells in adult skeletal muscle, and are responsible for postnatal muscle growth, hypertrophy and regeneration. In mature muscle, most satellite cells are in a Quiescent State, but they activate and begin proliferating in response to extrinsic signals. Following activation, a subset of satellite cell progeny returns to the Quiescent State during the process of self-renewal. Here, we review recent studies of satellite cell biology and focus on the key transitions from the Quiescent State to the State of proliferative activation and myogenic lineage progression and back to the Quiescent State. The molecular mechanisms of these transitions are considered in the context of the biology of the satellite cell niche, changes with age, and interactions with established pathways of myogenic commitment and differentiation.
