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D Jones - One of the best experts on this subject based on the ideXlab platform.
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ngc 6778 strengthening the link between extreme abundance discrepancy factors and central star binarity in planetary Nebulae
Monthly Notices of the Royal Astronomical Society, 2016Co-Authors: J Garciarojas, D Jones, R Wesson, R L M Corradi, Henri M. J. BoffinAbstract:We present new optical spectra of the nearby, bright, planetary nebula NGC 6778. The nebula has been known to emit strong recombination lines for more than 40 years but this is the first detailed study of its abundances. Heavy element abundances derived from recombination lines are found to exceed those from collisionally excited lines by a factor of ~20 in an integrated spectrum of the nebula, which is among the largest known abundance discrepancy factors. Spatial analysis of the spectra shows that the abundance discrepancy factor is strongly, centrally peaked, reaching ~40 close to the central star. The central star of NGC 6778 is known to be a short period binary, further strengthening the link between high nebular abundance discrepancy factors and central star binarity.
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planetary Nebulae what can they tell us about close binary evolution
Eas Publications Series, 2015Co-Authors: D JonesAbstract:It is now clear that a binary pathway is responsible for a significant fraction of planetary Nebulae, and the continually increasing sample of known central binaries means that we are now in a position to begin to use these systems to further our understanding of binary evolution. Binary central stars of planetary Nebulae are key laboratories in understanding the formation processes of a wide-range of astrophysical phenomena – a point well-illustrated by the fact that the only known double-degenerate, super-Chandrasekhar mass binary which will merge in less than a Hubble time is found inside a planetary nebula. Here, I briefly outline our current understanding and avenues for future investigation.
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binary central stars of planetary Nebulae discovered through photometric variability iii the central star of abell 65
The Astronomical Journal, 2015Co-Authors: David J Frew, Todd Hillwig, Melissa Louie, Orsola De Marco, Howard E Bond, D JonesAbstract:A growing number of close binary stars are being discovered among central stars of planetary Nebulae. Recent and ongoing surveys are finding new systems and contributing to our knowledge of the evolution of close binary systems. The push to find more systems was largely based on early discoveries which suggested that 10%–15% of all central stars are close binaries. One goal of this series of papers is confirmation and classification of these systems as close binaries and determination of binary system parameters. Here we provide time-resolved multi-wavelength photometry of the central star of Abell 65 as well as further analysis of the nebula and discussion of possible binary–nebula connections. Our results for Abell 65 confirm recent work showing that it has a close, cool binary companion, though several of our model parameters disagree with the recently published values. With our longer time baseline of photometric observations from 1989 to 2009 we also provide a more precise orbital period of 1.0037577 days.
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binarity and the abundance discrepancy problem in planetary Nebulae
The Astrophysical Journal, 2015Co-Authors: Romano L M Corradi, D Jones, J Garciarojas, P RodriguezgilAbstract:The discrepancy between abundances computed using optical recombination lines and collisionally excited lines is a major unresolved problem in nebular astrophysics. Here, we show that the largest abundance discrepancies are reached in planetary Nebulae with close binary central stars. We illustrate this using deep spectroscopy of three Nebulae with a post common-envelope (CE) binary star. Abell 46 and Ou 5 have O2+/H+ abundance discrepancy factors larger than 50, and as high as 300 in the inner regions of Abell 46. Abell 63 has a smaller discrepancy factor around 10, which is still above the typical values in ionized Nebulae. Our spectroscopic analysis supports previous conclusions that, in addition to “standard” hot ( ∼ 104 K) gas, there exists a colder ( ∼ 103 K), ionized component that is highly enriched in heavy elements. These Nebulae have low ionized masses, between 10−3 and 10−1 M⊙ depending on the adopted electron densities and temperatures. Since the much more massive red giant envelope is expected to be entirely ejected in the CE phase, the currently observed Nebulae would be produced much later, during post-CE mass loss episodes when the envelope has already dispersed. These observations add constraints to the abundance discrepancy problem. We revise possible explanations. Some explanations are naturally linked to binarity such as, for instance, high-metallicity nova ejecta, but it is difficult at this stage to depict an evolutionary scenario consistent with all of the observed properties. We also introduce the hypothesis that these Nebulae are the result of tidal destruction, accretion, and ejection of Jupiter-like planets.
Eric G Blackman - One of the best experts on this subject based on the ideXlab platform.
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the chandra planetary nebula survey chanplans iii x ray emission from the central stars of planetary Nebulae
The Astrophysical Journal, 2015Co-Authors: Rodolfo Montez, O De Marco, V Bujarrabal, Joel H Kastner, B Balick, Eric G Blackman, A Frank, R L M Corradi, E Behar, Marcus FreemanAbstract:We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey observations of 59 planetary Nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact Nebulae. The vast majority of these point-like X-ray-emitting sources at PN cores display relatively hard (?0.5?keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-ray emission: (1) high-temperature plasmas with X-ray luminosities, L X, that appear uncorrelated with the CSPN bolometric luminosity, L bol and (2) lower-temperature plasmas with L X/L bol ~ 10?7. We suggest these two classes correspond to the physical processes of magnetically active binary companions and self-shocking stellar winds, respectively. In many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the PN central stars. By thus honing in on the origins of X-ray emission from PN central stars, we enhance the ability of CSPN X-ray sources to constrain models of PN shaping that invoke wind interactions and binarity.
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the chandra x ray survey of planetary Nebulae chanplans probing binarity magnetic fields and wind collisions
The Astronomical Journal, 2012Co-Authors: Joel H Kastner, O De Marco, Rodolfo Montez, B Balick, David J Frew, B Miszalski, Raghvendra Sahai, Eric G Blackman, A Frank, M A GuerreroAbstract:We present an overview of the initial results from the Chandra Planetary Nebula Survey (CHANPLANS), the first systematic (volume-limited) Chandra X-Ray Observatory survey of planetary Nebulae (PNe) in the solar neighborhood. The first phase of CHANPLANS targeted 21 mostly high-excitation PNe within {approx}1.5 kpc of Earth, yielding four detections of diffuse X-ray emission and nine detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within {approx}1.5 kpc that have been observed to date, we find an overall X-ray detection rate of {approx}70% for the 35 sample objects. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks-in most cases, 'hot bubbles'-formed by energetic wind collisions is detected in {approx}30%; five objects display both diffuse and point-like emission components. The presence (or absence) of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical Nebulae are more likely to display X-ray emission (either point-like or diffuse) than molecule-rich, bipolar, or Ring-like Nebulae. All but one of the point-like CSPNe X-ray sources display X-ray spectra that are harder than expected from hot ({approx}100more » kK) central stars emitting as simple blackbodies; the lone apparent exception is the central star of the Dumbbell nebula, NGC 6853. These hard X-ray excesses may suggest a high frequency of binary companions to CSPNe. Other potential explanations include self-shocking winds or PN mass fallback. Most PNe detected as diffuse X-ray sources are elliptical Nebulae that display a nested shell/halo structure and bright ansae; the diffuse X-ray emission regions are confined within inner, sharp-rimmed shells. All sample PNe that display diffuse X-ray emission have inner shell dynamical ages {approx}< 5 Multiplication-Sign 10{sup 3} yr, placing firm constraints on the timescale for strong shocks due to wind interactions in PNe. The high-energy emission arising in such wind shocks may contribute to the high excitation states of certain archetypical 'hot bubble' Nebulae (e.g., NGC 2392, 3242, 6826, and 7009).« less
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dynamos in asymptotic giant branch stars as the origin of magnetic fields shaping planetary Nebulae
Nature, 2001Co-Authors: Eric G Blackman, Adam Frank, Andrew J Markiel, John H Thomas, Hugh M Van HornAbstract:Planetary Nebulae are thought to be formed when a slow wind from the progenitor giant star is overtaken by a subsequent fast wind generated as the star enters its white dwarf stage1. A shock forms near the boundary between the winds, creating the relatively dense shell characteristic of a planetary nebula. A spherically symmetric wind will produce a spherically symmetric shell, yet over half of known planetary Nebulae are not spherical; rather, they are elliptical or bipolar in shape2. A magnetic field could launch and collimate a bipolar outflow, but the origin of such a field has hitherto been unclear, and some previous work has even suggested that a field could not be generated3. Here we show that an asymptotic-giant-branch (AGB) star can indeed generate a strong magnetic field, having as its origin a dynamo at the interface between the rapidly rotating core and the more slowly rotating envelope of the star. The fields are strong enough to shape the bipolar outflows that produce the observed bipolar planetary Nebulae. Magnetic braking of the stellar core during this process may also explain the puzzlingly4 slow rotation of most white dwarf stars.
M Bobrowsky - One of the best experts on this subject based on the ideXlab platform.
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an hst snapshot survey of proto planetary Nebulae candidates two types of axisymmetric reflection nebulosities
The Astrophysical Journal, 2000Co-Authors: Toshiya Ueta, M Meixner, M BobrowskyAbstract:We report the results from an optical imaging survey of proto-planetary nebula candidates using the Hubble Space Telescope (HST). The goals of the survey were to image low surface brightness optical reflection nebulosities around proto-planetary Nebulae and to investigate the distribution of the circumstellar dust, which scatters the star light from the central post-asymptotic giant branch star and creates the optical reflection nebulosities. We exploited the high resolving power and wide dynamic range of HST and detected nebulosities in 21 of 27 sources. The reduced and deconvolved images are presented along with photometric and geometric measurements. All detected reflection nebulosities show elongation, and the nebula morphology bifurcates depending on the degree of the central star obscuration. The star-obvious low-level-elongated (SOLE) Nebulae show a bright central star embedded in a faint, extended nebulosity, whereas the dust-prominent longitudinally extended (DUPLEX) Nebulae have remarkable bipolar structure with a completely or partially obscured central star. The intrinsic axisymmetry of these proto-planetary nebula reflection nebulosities demonstrates that the axisymmetry frequently found in planetary Nebulae predates the proto-planetary nebula phase, confirming previous independent results. We suggest that axisymmetry in proto-planetary Nebulae is created by an equatorially enhanced superwind at the end of the asymptotic giant branch phase. We discuss that the apparent morphological dichotomy is caused by a difference in the optical thickness of the circumstellar dust/gas shell with a differing equator-to-pole density contrast. Moreover, we show that SOLE and DUPLEX Nebulae are physically distinct types of proto-planetary Nebulae, with a suggestion that higher mass progenitor AGB stars are more likely to become DUPLEX proto-planetary Nebulae.
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an hst snapshot survey of proto planetary Nebulae candidates two types of axisymmetric reflection nebulosities
arXiv: Astrophysics, 1999Co-Authors: Toshiya Ueta, M Meixner, M BobrowskyAbstract:We report the results from an optical imaging survey of proto-planetary nebula candidates using the HST. We exploited the high resolving power and wide dynamic range of HST and detected nebulosities in 21 of 27 sources. All detected reflection nebulosities show elongation, and the nebula morphology bifurcates depending on the degree of the central star obscuration. The Star-Obvious Low-level-Elongated (SOLE) Nebulae show a bright central star embedded in a faint, extended nebulosity, whereas the DUst-Prominent Longitudinally-EXtended (DUPLEX) Nebulae have remarkable bipolar structure with a completely or partially obscured central star. The intrinsic axisymmetry of these proto-planetary nebula reflection nebulosities demonstrates that the axisymmetry frequently found in planetary Nebulae predates the proto-planetary nebula phase, confirming previous independent results. We suggest that axisymmetry in proto-planetary Nebulae is created by an equatorially enhanced superwind at the end of the asymptotic giant branch phase. We discuss that the apparent morphological dichotomy is caused by a difference in the optical thickness of the circumstellar dust/gas shell with a differing equator-to-pole density contrast. Moreover, we show that SOLE and DUPLEX Nebulae are physically distinct types of proto-planetary Nebulae, with a suggestion that higher mass progenitor AGB stars are more likely to become DUPLEX proto-planetary Nebulae.
David J Frew - One of the best experts on this subject based on the ideXlab platform.
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binary central stars of planetary Nebulae discovered through photometric variability iii the central star of abell 65
The Astronomical Journal, 2015Co-Authors: David J Frew, Todd Hillwig, Melissa Louie, Orsola De Marco, Howard E Bond, D JonesAbstract:A growing number of close binary stars are being discovered among central stars of planetary Nebulae. Recent and ongoing surveys are finding new systems and contributing to our knowledge of the evolution of close binary systems. The push to find more systems was largely based on early discoveries which suggested that 10%–15% of all central stars are close binaries. One goal of this series of papers is confirmation and classification of these systems as close binaries and determination of binary system parameters. Here we provide time-resolved multi-wavelength photometry of the central star of Abell 65 as well as further analysis of the nebula and discussion of possible binary–nebula connections. Our results for Abell 65 confirm recent work showing that it has a close, cool binary companion, though several of our model parameters disagree with the recently published values. With our longer time baseline of photometric observations from 1989 to 2009 we also provide a more precise orbital period of 1.0037577 days.
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the chandra x ray survey of planetary Nebulae chanplans probing binarity magnetic fields and wind collisions
The Astronomical Journal, 2012Co-Authors: Joel H Kastner, O De Marco, Rodolfo Montez, B Balick, David J Frew, B Miszalski, Raghvendra Sahai, Eric G Blackman, A Frank, M A GuerreroAbstract:We present an overview of the initial results from the Chandra Planetary Nebula Survey (CHANPLANS), the first systematic (volume-limited) Chandra X-Ray Observatory survey of planetary Nebulae (PNe) in the solar neighborhood. The first phase of CHANPLANS targeted 21 mostly high-excitation PNe within {approx}1.5 kpc of Earth, yielding four detections of diffuse X-ray emission and nine detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within {approx}1.5 kpc that have been observed to date, we find an overall X-ray detection rate of {approx}70% for the 35 sample objects. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks-in most cases, 'hot bubbles'-formed by energetic wind collisions is detected in {approx}30%; five objects display both diffuse and point-like emission components. The presence (or absence) of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical Nebulae are more likely to display X-ray emission (either point-like or diffuse) than molecule-rich, bipolar, or Ring-like Nebulae. All but one of the point-like CSPNe X-ray sources display X-ray spectra that are harder than expected from hot ({approx}100more » kK) central stars emitting as simple blackbodies; the lone apparent exception is the central star of the Dumbbell nebula, NGC 6853. These hard X-ray excesses may suggest a high frequency of binary companions to CSPNe. Other potential explanations include self-shocking winds or PN mass fallback. Most PNe detected as diffuse X-ray sources are elliptical Nebulae that display a nested shell/halo structure and bright ansae; the diffuse X-ray emission regions are confined within inner, sharp-rimmed shells. All sample PNe that display diffuse X-ray emission have inner shell dynamical ages {approx}< 5 Multiplication-Sign 10{sup 3} yr, placing firm constraints on the timescale for strong shocks due to wind interactions in PNe. The high-energy emission arising in such wind shocks may contribute to the high excitation states of certain archetypical 'hot bubble' Nebulae (e.g., NGC 2392, 3242, 6826, and 7009).« less
Joel H Kastner - One of the best experts on this subject based on the ideXlab platform.
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the chandra planetary nebula survey chanplans iii x ray emission from the central stars of planetary Nebulae
The Astrophysical Journal, 2015Co-Authors: Rodolfo Montez, O De Marco, V Bujarrabal, Joel H Kastner, B Balick, Eric G Blackman, A Frank, R L M Corradi, E Behar, Marcus FreemanAbstract:We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey observations of 59 planetary Nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact Nebulae. The vast majority of these point-like X-ray-emitting sources at PN cores display relatively hard (?0.5?keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-ray emission: (1) high-temperature plasmas with X-ray luminosities, L X, that appear uncorrelated with the CSPN bolometric luminosity, L bol and (2) lower-temperature plasmas with L X/L bol ~ 10?7. We suggest these two classes correspond to the physical processes of magnetically active binary companions and self-shocking stellar winds, respectively. In many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the PN central stars. By thus honing in on the origins of X-ray emission from PN central stars, we enhance the ability of CSPN X-ray sources to constrain models of PN shaping that invoke wind interactions and binarity.
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the chandra x ray survey of planetary Nebulae chanplans probing binarity magnetic fields and wind collisions
The Astronomical Journal, 2012Co-Authors: Joel H Kastner, O De Marco, Rodolfo Montez, B Balick, David J Frew, B Miszalski, Raghvendra Sahai, Eric G Blackman, A Frank, M A GuerreroAbstract:We present an overview of the initial results from the Chandra Planetary Nebula Survey (CHANPLANS), the first systematic (volume-limited) Chandra X-Ray Observatory survey of planetary Nebulae (PNe) in the solar neighborhood. The first phase of CHANPLANS targeted 21 mostly high-excitation PNe within {approx}1.5 kpc of Earth, yielding four detections of diffuse X-ray emission and nine detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within {approx}1.5 kpc that have been observed to date, we find an overall X-ray detection rate of {approx}70% for the 35 sample objects. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks-in most cases, 'hot bubbles'-formed by energetic wind collisions is detected in {approx}30%; five objects display both diffuse and point-like emission components. The presence (or absence) of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical Nebulae are more likely to display X-ray emission (either point-like or diffuse) than molecule-rich, bipolar, or Ring-like Nebulae. All but one of the point-like CSPNe X-ray sources display X-ray spectra that are harder than expected from hot ({approx}100more » kK) central stars emitting as simple blackbodies; the lone apparent exception is the central star of the Dumbbell nebula, NGC 6853. These hard X-ray excesses may suggest a high frequency of binary companions to CSPNe. Other potential explanations include self-shocking winds or PN mass fallback. Most PNe detected as diffuse X-ray sources are elliptical Nebulae that display a nested shell/halo structure and bright ansae; the diffuse X-ray emission regions are confined within inner, sharp-rimmed shells. All sample PNe that display diffuse X-ray emission have inner shell dynamical ages {approx}< 5 Multiplication-Sign 10{sup 3} yr, placing firm constraints on the timescale for strong shocks due to wind interactions in PNe. The high-energy emission arising in such wind shocks may contribute to the high excitation states of certain archetypical 'hot bubble' Nebulae (e.g., NGC 2392, 3242, 6826, and 7009).« less
