The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Bruce Balick - One of the best experts on this subject based on the ideXlab platform.

  • bipolar Planetary Nebulae from outflow collimation by common envelope evolution
    Monthly Notices of the Royal Astronomical Society, 2020
    Co-Authors: Yangyuxin Zou, Orsola De Marco, Adam Frank, Eric G Blackman, Zhuo Chen, Thomas Reichardt, Jason Nordhaus, Bruce Balick, Jonathan Carrollnellenback
    Abstract:

    The morphology of bipolar Planetary Nebulae (PNe) can be attributed to interactions between a fast wind from the central engine and dense toroidal shaped ejecta left over from common envelope (CE) evolution. Here we use the 3-D hydrodynamic AMR code AstroBEAR to study the possibility that bipolar PN outflows can emerge collimated even from an uncollimated spherical wind in the aftermath of a CE event. The output of a single CE simulation via the SPH code PHANTOM serves as the initial conditions. Four cases of winds, all with high enough momenta to account for observed high momenta prePlanetary nebula outflows, are injected spherically from the region of the CE binary remnant into the ejecta. We compare cases with two different momenta and cases with no radiative cooling versus application of optically thin emission via a cooling curve to the outflow. Our simulations show that in all cases highly collimated bipolar outflows result from deflection of the spherical wind via the interaction with the CE ejecta. Significant asymmetries between the top and bottom lobes are seen in all cases. The asymmetry is strongest for the lower momentum case with radiative cooling. While real post CE winds may be aspherical, our models show that collimation via "inertial confinement" will be strong enough to create jet-like outflows even beginning with maximally uncollimated drivers. Our simulations reveal detailed shock structures in the shock focused inertial confinement (SFIC) model and develop a lens-shaped inner shock that is a new feature of SFIC driven bipolar lobes.

  • co spatial long slit uv optical spectra of ten galactic Planetary Nebulae with hst stis ii nebular models central star properties and he cno synthesis
    The Astrophysical Journal, 2015
    Co-Authors: R C Henry, K B Kwitter, Bruce Balick, R L M Corradi, Richard A Shaw, R J Dufour, Timothy R Miller, J F Buell
    Abstract:

    The goal of the present study is twofold. First, we employ new HST/STIS spectra and photoionization modeling techniques to determine the progenitor masses of eight Planetary Nebulae (IC 2165, IC 3568, NGC 2440, NGC 3242, NGC 5315, NGC 5882, NGC 7662, and PB 6). Second, for the first time we are able to compare each object's observed nebular abundances of helium, carbon, and nitrogen with abundance predictions of these same elements by a stellar model that is consistent with each object's progenitor mass. Important results include the following: (1) the mass range of our objects' central stars matches well with the mass distribution of other central stars of Planetary Nebulae and white dwarfs; (2) He/H is above solar in all of our objects, in most cases likely due to the predicted effects of first dredge-up; (3) most of our objects show negligible C enrichment, probably because their low masses preclude third dredge-up; (4) C/O versus O/H for our objects appears to be inversely correlated, which is perhaps consistent with the conclusion of theorists that the extent of atmospheric carbon enrichment from first dredge-up is sensitive to a parameter whose value increases as metallicity declines; (5) stellar model predictions of nebular C and N enrichment are consistent with observed abundances for progenitor star masses ≤1.5 M⊙. Finally, we present the first published photoionization models of NGC 5315 and NGC 5882.

  • the chemistry of Planetary Nebulae in the outer regions of m31
    The Astrophysical Journal, 2015
    Co-Authors: R C Henry, K B Kwitter, Bruce Balick, R L M Corradi, K Hensley
    Abstract:

    We present spectroscopy of nine Planetary Nebulae (PNe) in the outskirts of M31, all but one obtained with the 10.4 m GTC telescope. These sources extend our previous study of the oxygen abundance gradient of M31 to galactocentric radii as large as 100 kpc. None of the targets are bona fide members of a classical, metal-poor, and ancient halo. Two of the outermost PNe have solar oxygen abundances, as well as radial velocities consistent with the kinematics of the extended disk of M31. The other PNe have a slightly lower oxygen content ([O/H] ) and in some cases large deviations from the disk kinematics. These PNe support the current view that the external regions of M31 are the result of a complex interaction and merger process, with evidence for a widespread population of solar-metallicity stars produced in a starburst that occurred ~2 Gyr ago.

  • panchromatic hubble andromeda treasury ix a photometric survey of Planetary Nebulae in m31
    The Astrophysical Journal, 2014
    Co-Authors: Bruce Balick, Mark J Veyette, Benjamin F Williams, Julianne J Dalcanton, Nelson Caldwell, Morgan Fouesneau, Leo Girardi, K D Gordon
    Abstract:

    We search the Hubble Space Telescope (HST) Advanced Camera for Surveys and Wide Field Camera 3 broadband imaging data from the Panchromatic Hubble Andromeda Treasury (PHAT) survey to identify detections of cataloged Planetary Nebulae (PNs). Of the 711 PNs currently in the literature within the PHAT footprint, we find 467 detected in the broadband. For these 467, we are able to refine their astrometric accuracy from ∼0.''3 to 0.''05. Using the resolution of the HST, we are able to show that 152 objects currently in the catalogs are definitively not PNs, and we show that 32 objects thought to be extended in ground-based images are actually point-like and therefore good PN candidates. We also find one PN candidate that is marginally resolved. If this is a PN, it is up to 0.7 pc in diameter. With our new photometric data, we develop a method of measuring the level of excitation in individual PNs by comparing broadband and narrowband imaging and describe the effects of excitation on a PN's photometric signature. Using the photometric properties of the known PNs in the PHAT catalogs, we search for more PNs, but do not find any new candidates, suggesting that ground-based emission-line surveys aremore » complete in the PHAT footprint to F475W ≅ 24.« less

  • panchromatic hubble andromeda treasury ix a photometric survey of Planetary Nebulae in m31
    arXiv: Astrophysics of Galaxies, 2014
    Co-Authors: Bruce Balick, Mark J Veyette, Benjamin F Williams, Julianne J Dalcanton, Nelson Caldwell, Morgan Fouesneau, Leo Girardi, K D Gordon
    Abstract:

    We search Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3) broadband imaging data from the Panchromatic Hubble Andromeda Treasury (PHAT) survey to identify detections of cataloged Planetary Nebulae (PNe). Of the 711 PNe currently in the literature within the PHAT footprint, we find 467 detected in the broadband. For these 467 we are able to refine their astrometric accuracy from ~0."3 to 0."05. Using the resolution of HST, we are able to show that 152 objects currently in the catalogs are definitively not PNe, and we show that 32 objects thought to be extended in ground-based images are actually point-like and therefore good PN candidates. We also find one PN candidate that is marginally resolved. If this is a PN, it is up to 0.7 pc in diameter. With our new photometric data, we develop a method of measuring the level of excitation in individual PNe by comparing broadband and narrowband imaging and describe the effects of excitation on a PN's photometric signature. Using the photometric properties of the known PNe in the PHAT catalogs, we search for more PN, but do not find any new candidates, suggesting that ground-based emission-line surveys are complete in the PHAT footprint to F475W $\simeq$ 24.

Raghvendra Sahai - One of the best experts on this subject based on the ideXlab platform.

  • the chandra Planetary nebula survey chanplans ii x ray emission from compact Planetary Nebulae
    arXiv: Solar and Stellar Astrophysics, 2014
    Co-Authors: M Freeman, David J Frew, D. Jones, Joel H. Kastner, Bruce Balick, Raghvendra Sahai, Rodolfo Montez, B Miszalski, Eric G Blackman
    Abstract:

    We present results from the most recent set of observations obtained as part of the Chandra X-ray observatory Planetary Nebula Survey (ChanPlaNS), the first comprehensive X-ray survey of Planetary Nebulae (PNe) in the solar neighborhood (i.e., within ~1.5 kpc of the Sun). The survey is designed to place constraints on the frequency of appearance and range of X-ray spectral characteristics of X-ray-emitting PN central stars and the evolutionary timescales of wind-shock-heated bubbles within PNe. ChanPlaNS began with a combined Cycle 12 and archive Chandra survey of 35 PNe. ChanPlaNS continued via a Chandra Cycle 14 Large Program which targeted all (24) remaining known compact (R_neb ~1000 cm^-3), and rarely associated with PNe that show H_2 emission and/or pronounced butterfly structures. Hb 5 is one such exception of a PN with a butterfly structure that hosts diffuse X-ray emission. Additionally, of the five new diffuse X-ray detections, two host [WR]-type CSPNe, NGC 1501 and NGC 6369, supporting the hypothesis that PNe with central stars of [WR]-type are likely to display diffuse X-ray emission.

  • young Planetary Nebulae hubble space telescope imaging and a new morphological classification system
    The Astronomical Journal, 2011
    Co-Authors: Raghvendra Sahai, Mark Morris, Gregory G Villar
    Abstract:

    Using Hubble Space Telescope images of 119 young Planetary Nebulae (PNs), most of which have not previously been published, we have devised a comprehensive morphological classification system for these objects. This system generalizes a recently devised system for pre-Planetary Nebulae, which are the immediate progenitors of PNs. Unlike previous classification studies, we have focused primarily on young PNs rather than all PNs, because the former best show the influences or symmetries imposed on them by the dominant physical processes operating at the first and primary stage of the shaping process. Older PNs develop instabilities, interact with the ambient interstellar medium, and are subject to the passage of photoionization fronts, all of which obscure the underlying symmetries and geometries imposed early on. Our classification system is designed to suffer minimal prejudice regarding the underlying physical causes of the different shapes and structures seen in our PN sample, however, in many cases, physical causes are readily suggested by the geometry, along with the kinematics that have been measured in some systems. Secondary characteristics in our system, such as ansae, indicate the impact of a jet upon a slower-moving, prior wind; a waist is the signature of a strong equatorial concentration of matter, whether it be outflowing or in a bound Keplerian disk, and point symmetry indicates a secular trend, presumably precession, in the orientation of the central driver of a rapid, collimated outflow.

  • young Planetary Nebulae hubble space telescope imaging and a new morphological classification system
    arXiv: Astrophysics of Galaxies, 2011
    Co-Authors: Raghvendra Sahai, Mark Morris, Gregory G Villar
    Abstract:

    Using Hubble Space Telescope images of 119 young Planetary Nebulae, most of which have not previously been published, we have devised a comprehensive morphological classification system for these objects. This system generalizes a recently devised system for pre-Planetary Nebulae, which are the immediate progenitors of Planetary Nebulae (PNs). Unlike previous classification studies, we have focussed primarily on young PNs rather than all PNs, because the former best show the influences or symmetries imposed on them by the dominant physical processes operating at the first and primary stage of the shaping process. Older PNs develop instabilities, interact with the ambient interstellar medium, and are subject to the passage of photoionization fronts, all of which obscure the underlying symmetries and geometries imposed early on. Our classification system is designed to suffer minimal prejudice regarding the underlying physical causes of the different shapes and structures seen in our PN sample, however, in many cases, physical causes are readily suggested by the geometry, along with the kinematics that have been measured in some systems. Secondary characteristics in our system such as ansae indicate the impact of a jet upon a slower-moving, prior wind; a waist is the signature of a strong equatorial concentration of matter, whether it be outflowing or in a bound Keplerian disk, and point symmetry indicates a secular trend, presumably precession, in the orientation of the central driver of a rapid, collimated outflow.

  • the starfish twins two young Planetary Nebulae with extreme multipolar morphology
    The Astrophysical Journal, 2000
    Co-Authors: Raghvendra Sahai
    Abstract:

    We present Hα images of two objects, He 2-47 and M1-37, obtained during a Hubble Space Telescope imaging survey of young Planetary Nebulae (PNs) selected on the basis of their low-excitation characteristics. The two objects show a highly aspherical morphology, characterized by multiple lobes distributed around the central star. Such a morphology has never been seen before in any astrophysical setting. Bright structures near the minor axes indicate the presence of dense equatorial tori (seen edge-on in M1-37 and as partial elliptical rings in He 2-47). In both Nebulae, the central star is found to be offset from the geometrical center of symmetry of the waist region. The multiple lobes of He 2-47 and M1-37 have been produced fairly recently (a few hundred years ago), based on rough estimates of their expansion ages. The extreme multipolar morphology of these PNs supports the recent hypothesis of Sahai & Trauger that the primary agents for shaping PNs are high-speed collimated outflows that operate during the late asymptotic giant branch (AGB) and/or early post-AGB evolutionary phase; these outflows change their direction episodically, and/or multiple collimated outflows with different axes operate (quasi)simultaneously. Drastic modifications of existing theories or completely new ideas are needed in order to obtain a full understanding of the salient morphological features of He 2-47 and M1-37.

  • multipolar bubbles and jets in low excitation Planetary Nebulae toward a new understanding of the formation and shaping of Planetary Nebulae
    The Astronomical Journal, 1998
    Co-Authors: Raghvendra Sahai, John T Trauger
    Abstract:

    First results from a Hubble Space Telescope Wide Field Planetary Camera 2 Hα imaging survey of young Planetary Nebulae (PNs) are reported. The PNs have been selected on the basis of their low excitation characteristics. All objects imaged so far show highly aspherical morphology, with a majority characterized by multipolar bubbles distributed roughly point-symmetrically around the central star. In some objects, bipolar ansae or collimated radial structures are seen, indicating the presence of jets, whereas in others bright structures near the minor axes indicate the presence of disks or torii. The complexity, organization, and symmetry of the above structures lead us to propose that the primary agent for shaping PNs is high-speed collimated outflows or jets that operate during the late asymptotic galactic branch (AGB) and/or early post-AGB evolutionary phase, and not a preexisting equatorial density enhancement as envisioned in the currently popular model. These outflows carve out a complex imprint within an intrinsically spherical AGB circumstellar envelope (CSE). Subsequent expansion of a hot, tenuous stellar wind from the post-AGB star inside the imprinted AGB CSE then produces the observed PN, whose shape and structure depend in detail on how the characteristics of the jets change with time.

R C Henry - One of the best experts on this subject based on the ideXlab platform.

  • co spatial long slit uv optical spectra of ten galactic Planetary Nebulae with hst stis ii nebular models central star properties and he cno synthesis
    The Astrophysical Journal, 2015
    Co-Authors: R C Henry, K B Kwitter, Bruce Balick, R L M Corradi, Richard A Shaw, R J Dufour, Timothy R Miller, J F Buell
    Abstract:

    The goal of the present study is twofold. First, we employ new HST/STIS spectra and photoionization modeling techniques to determine the progenitor masses of eight Planetary Nebulae (IC 2165, IC 3568, NGC 2440, NGC 3242, NGC 5315, NGC 5882, NGC 7662, and PB 6). Second, for the first time we are able to compare each object's observed nebular abundances of helium, carbon, and nitrogen with abundance predictions of these same elements by a stellar model that is consistent with each object's progenitor mass. Important results include the following: (1) the mass range of our objects' central stars matches well with the mass distribution of other central stars of Planetary Nebulae and white dwarfs; (2) He/H is above solar in all of our objects, in most cases likely due to the predicted effects of first dredge-up; (3) most of our objects show negligible C enrichment, probably because their low masses preclude third dredge-up; (4) C/O versus O/H for our objects appears to be inversely correlated, which is perhaps consistent with the conclusion of theorists that the extent of atmospheric carbon enrichment from first dredge-up is sensitive to a parameter whose value increases as metallicity declines; (5) stellar model predictions of nebular C and N enrichment are consistent with observed abundances for progenitor star masses ≤1.5 M⊙. Finally, we present the first published photoionization models of NGC 5315 and NGC 5882.

  • the chemistry of Planetary Nebulae in the outer regions of m31
    The Astrophysical Journal, 2015
    Co-Authors: R C Henry, K B Kwitter, Bruce Balick, R L M Corradi, K Hensley
    Abstract:

    We present spectroscopy of nine Planetary Nebulae (PNe) in the outskirts of M31, all but one obtained with the 10.4 m GTC telescope. These sources extend our previous study of the oxygen abundance gradient of M31 to galactocentric radii as large as 100 kpc. None of the targets are bona fide members of a classical, metal-poor, and ancient halo. Two of the outermost PNe have solar oxygen abundances, as well as radial velocities consistent with the kinematics of the extended disk of M31. The other PNe have a slightly lower oxygen content ([O/H] ) and in some cases large deviations from the disk kinematics. These PNe support the current view that the external regions of M31 are the result of a complex interaction and merger process, with evidence for a widespread population of solar-metallicity stars produced in a starburst that occurred ~2 Gyr ago.

  • metal rich Planetary Nebulae in the outer reaches of m31
    The Astrophysical Journal, 2013
    Co-Authors: B Balick, R L M Corradi, K B Kwitter, R C Henry
    Abstract:

    Spectroscopic data of two relatively [O III]-luminous Planetary Nebulae (PNe) have been obtained with the 10.4?m Gran Telescopio Canarias. M174 and M2496 are each ~1? from the center of M31 along opposite sides of its minor axis. The ensemble of these 2 distant PNe plus 16 similarly luminous outer-disk PNe published previously by Kwitter et al. forms a homogeneous group in luminosity, metal content, progenitor mass, age, and kinematics. The main factual findings of our work are (1) O/H (and other low-mass ? elements and their ratios to O) is uniformly solar-like in all 18 PNe (12 + log(O/H) = 8.62 ? 0.14); (2) the general sky distribution and kinematics of the ensemble much more closely resemble the rotation pattern of the classical disk of M31 than its halo or bulge; (3)?the O/H gradient is surprisingly flat beyond Rg ~ 20?kpc. The PNe are too metal-rich to be bona fide members of M31's disk or halo, and (4) the abundance patterns of the sample are distinct from those in the spiral galaxies M33, M81, and NGC?300. Using standard PN age diagnostic methods, we suggest that all of the PNe formed ~2?Gyr ago in a starburst of metal-rich interstellar medium that followed an M31-M33 encounter about 3?Gyr ago. We review supporting evidence from stellar studies. Other more prosaic explanations, such as dwarf galaxy assimilation, are unlikely.

  • sulfur chlorine and argon abundances in Planetary Nebulae iv synthesis and the sulfur anomaly
    The Astronomical Journal, 2004
    Co-Authors: R C Henry, K B Kwitter, Bruce Balick
    Abstract:

    We have compiled a large sample of O, Ne, S, Cl, and Ar abundances that have been determined for 85 Galactic Planetary Nebulae in a consistent and homogeneous manner using spectra extending from 3600 to 9600 A. Sulfur abundances have been computed using the near-IR lines of [S III] λλ9069, 9532 along with [S III] temperatures. We find average values, expressed logarithmically with a standard deviation, of log(S/O) = -1.91 ± 0.24, log(Cl/O) = -3.52 ± 0.16, and log(Ar/O) = -2.29 ± 0.18, numbers consistent with previous studies of both Planetary Nebulae and H II regions. We also find a strong correlation between [O III] and [S III] temperatures among Planetary Nebulae. In analyzing abundances of Ne, S, Cl, and Ar with respect to O, we find a tight correlation for Ne-O, and loose correlations for Cl-O and Ar-O. All three trends appear to be colinear with observed correlations for H II regions. S and O also show a correlation, but there is a definite offset from the behavior exhibited by H II regions and stars. We suggest that this S anomaly is most easily explained by the existence of S+3, whose abundance must be inferred indirectly when only optical spectra are available, in amounts in excess of what is predicted by model-derived ionization correction factors in PNe. Finally for the disk PNe, abundances of O, Ne, S, Cl, and Ar all show gradients when plotted against Galactocentric distance. The slopes are statistically indistinguishable from one another, a result which is consistent with the notion that the cosmic abundances of these elements evolve in lockstep.

  • sulfur chlorine and argon abundances in Planetary Nebulae iv synthesis and the sulfur anomaly
    arXiv: Astrophysics, 2004
    Co-Authors: R C Henry, K B Kwitter, Bruce Balick
    Abstract:

    We have compiled a large sample of O, Ne, S, Cl, and Ar abundances which have been determined for 85 galactic Planetary Nebulae in a consistent and homogeneous manner using spectra extending from 3600-9600 Angstroms. Sulfur abundances have been computed using the near IR lines of [S III] 9069,9532 along with [S III] temperatures. We find average values, expressed logarithmically with a standard deviation, of log(S/O)=-1.91(+/-.24), log(Cl/O)=-3.52(+/-.16), and log(Ar/O)=-2.29(+/-.18), numbers consistent with previous studies of both Planetary Nebulae and H II regions. We also find a strong correlation between [O III] and [S III] temperatures among Planetary Nebulae. In analyzing abundances of Ne, S, Cl, and Ar with respect to O, we find a tight correlation for Ne-O, and loose correlations for Cl-O and Ar-O. All three trends appear to be colinear with observed correlations for H II regions. S and O also show a correlation but there is a definite offset from the behavior exhibited by H II regions and stars. We suggest that this S anomaly is most easily explained by the existence of S^+3, whose abundance must be inferred indirectly when only optical spectra are available, in amounts in excess of what is predicted by model-derived ionization correction factors. Finally for the disk PNe, abundances of O, Ne, S, Cl, and Ar all show gradients when plotted against galactocentric distance. The slopes are statistically indistinguishable from one another, a result which is consistent with the notion that the cosmic abundances of these elements evolve in lockstep.

Gregory G Villar - One of the best experts on this subject based on the ideXlab platform.

  • young Planetary Nebulae hubble space telescope imaging and a new morphological classification system
    The Astronomical Journal, 2011
    Co-Authors: Raghvendra Sahai, Mark Morris, Gregory G Villar
    Abstract:

    Using Hubble Space Telescope images of 119 young Planetary Nebulae (PNs), most of which have not previously been published, we have devised a comprehensive morphological classification system for these objects. This system generalizes a recently devised system for pre-Planetary Nebulae, which are the immediate progenitors of PNs. Unlike previous classification studies, we have focused primarily on young PNs rather than all PNs, because the former best show the influences or symmetries imposed on them by the dominant physical processes operating at the first and primary stage of the shaping process. Older PNs develop instabilities, interact with the ambient interstellar medium, and are subject to the passage of photoionization fronts, all of which obscure the underlying symmetries and geometries imposed early on. Our classification system is designed to suffer minimal prejudice regarding the underlying physical causes of the different shapes and structures seen in our PN sample, however, in many cases, physical causes are readily suggested by the geometry, along with the kinematics that have been measured in some systems. Secondary characteristics in our system, such as ansae, indicate the impact of a jet upon a slower-moving, prior wind; a waist is the signature of a strong equatorial concentration of matter, whether it be outflowing or in a bound Keplerian disk, and point symmetry indicates a secular trend, presumably precession, in the orientation of the central driver of a rapid, collimated outflow.

  • young Planetary Nebulae hubble space telescope imaging and a new morphological classification system
    arXiv: Astrophysics of Galaxies, 2011
    Co-Authors: Raghvendra Sahai, Mark Morris, Gregory G Villar
    Abstract:

    Using Hubble Space Telescope images of 119 young Planetary Nebulae, most of which have not previously been published, we have devised a comprehensive morphological classification system for these objects. This system generalizes a recently devised system for pre-Planetary Nebulae, which are the immediate progenitors of Planetary Nebulae (PNs). Unlike previous classification studies, we have focussed primarily on young PNs rather than all PNs, because the former best show the influences or symmetries imposed on them by the dominant physical processes operating at the first and primary stage of the shaping process. Older PNs develop instabilities, interact with the ambient interstellar medium, and are subject to the passage of photoionization fronts, all of which obscure the underlying symmetries and geometries imposed early on. Our classification system is designed to suffer minimal prejudice regarding the underlying physical causes of the different shapes and structures seen in our PN sample, however, in many cases, physical causes are readily suggested by the geometry, along with the kinematics that have been measured in some systems. Secondary characteristics in our system such as ansae indicate the impact of a jet upon a slower-moving, prior wind; a waist is the signature of a strong equatorial concentration of matter, whether it be outflowing or in a bound Keplerian disk, and point symmetry indicates a secular trend, presumably precession, in the orientation of the central driver of a rapid, collimated outflow.

D. Jones - One of the best experts on this subject based on the ideXlab platform.

  • binary central stars of Planetary Nebulae identified with kepler k2
    Monthly Notices of the Royal Astronomical Society, 2021
    Co-Authors: George H Jacoby, Todd Hillwig, Orsola De Marco, D. Jones, Kayla Martin, Matthias Kronberger, Jonathan L Hurowitz, Alison F Crocker, Josh Dey
    Abstract:

    We present the identification of 34 likely binary central stars (CSs) of Planetary Nebulae (PNe) from {\it Kepler/K2} data, seven of which show eclipses. Of these, 29 are new discoveries. Two additional CSs with more complicated variability are also presented. We examined the light curves of all `possible', `likely' and `true' PNe in every {\it Kepler/K2} campaign (0 through 19) to identify CS variability that may indicate a binary CS. For Campaigns 0, 2, 7, 15, and 16 we find 6 likely or confirmed variables among 21 PNe. Our primary effort, though, was focused on Campaign 11 which targeted a Galactic bulge field containing approximately 183 PNe, in which we identified 30 candidate variable CSs. The periods of these variables range from 2.3~h to 30~d, and based on our analysis, most are likely to be close binary star systems. We present periods and preliminary classifications (eclipsing, double degenerate, or irradiated systems) for the likely binaries based on light curve shape. From our total sample of 204 target PNe, with a correction for incompleteness due to magnitude limits, we calculate a binary fraction of PN central stars to be 20.7 percent for all the observed PNe, or 23.5 percent if we limit our sample only to `true' PNe. However these fractions are almost certainly lower limits due to the large angular size of the \emph{Kepler} pixels, which leads to reduced sensitivity in detecting variability, primarily as a result of dilution and noise from the nebula and neighbouring stars. We discuss the binary population of CSs based on these results as part of the total known sample of close binary CSs.

  • binary stars as the key to understanding Planetary Nebulae
    Nature Astronomy, 2017
    Co-Authors: D. Jones, Henri M J Boffin
    Abstract:

    Planetary Nebulae are traditionally considered to represent the final evolutionary stage of all intermediate-mass stars (∼0.7–8 M☉). Recent evidence seems to contradict this picture. In particular, since the launch of the Hubble Space Telescope, it has been clear that Planetary Nebulae display a wide range of striking morphologies that cannot be understood in a single-star scenario, instead pointing towards binary evolution in a majority of systems. Here, we summarize our current understanding of the importance of binarity in the formation and shaping of Planetary Nebulae, as well as the surprises that recent observational studies have revealed with respect to our understanding of binary evolution in general. These advances have critical implications for the understanding of mass transfer processes in binary stars—particularly the all-important but ever-so-poorly understood ‘common envelope phase’—as well as the formation of cosmologically important type Ia supernovae. Planetary Nebulae, traditionally seen as an endpoint of single stars, exhibit a variety of morphologies that cannot be explained in a single-star scenario. It is becoming clearer that perhaps even the majority of Planetary Nebulae result from binary interactions.

  • binary stars as the key to understanding Planetary Nebulae
    arXiv: Solar and Stellar Astrophysics, 2017
    Co-Authors: D. Jones, Henri M J Boffin
    Abstract:

    Planetary Nebulae are traditionally considered to represent the final evolutionary stage of all intermediate-mass stars ($\sim$0.7-8Msol). Recent evidence seems to contradict this picture. In particular, since the launch of the Hubble Space Telescope it has become clear that Planetary Nebulae display a wide range of striking morphologies which cannot be understood in a single star scenario, instead pointing towards a binary evolution in a majority of systems. Here, we summarise our current understanding of the importance of binarity in the formation and shaping of Planetary Nebulae, as well as the surprises that recent observational studies have revealed with respect to our understanding of binary evolution in general. These advances have critical implications, including for the understanding of mass transfer processes in binary stars - particularly the all-important but ever-so poorly understood `common envelope phase' - as well as the formation of cosmologically important type Ia supernovae.

  • the post common envelope central stars of the Planetary Nebulae henize 2 155 and henize 2 161
    Astronomy and Astrophysics, 2015
    Co-Authors: P Rodriguezgil, D. Jones, H M J Boffin, R Wesson, R L M Corradi, B Miszalski, S Mohamed
    Abstract:

    We present a study of Hen 2-155 and Hen 2-161, two Planetary Nebulae which bear striking morphological similarities to other Planetary Nebulae known to host close-binary central stars. Both central stars are revealed to be photometric variables while spectroscopic observations confirm that Hen 2-155 is host to a double-eclipsing, post-common-envelope system with an orbital period of 3 h 33 m making it one of the shortest period binary central stars known. The observations of Hen 2-161 are found to be consistent with a post-common-envelope binary of period ∼1 day. A detailed model of the central star of Hen 2-155 is produced, showing the nebular progenitor to be a hot, post-AGB remnant of approximately 0.62 M� , consistent with the age of the nebula, and the secondary star to be an M dwarf whose radius is almost twice the expected zero age main sequence radius for its mass. In spite of the small numbers, all main-sequence companions, of Planetary Nebulae central stars, to have had their masses and radii constrained by both photometric and spectroscopic observations have also been found to display this “inflation”. The cause of the “inflation” is uncertain but is probably related to rapid accretion, immediately before the recent common-envelope phase, to which the star has not yet thermally adjusted. The chemical composition of both Nebulae is also analysed, showing both to display elevated abundance discrepancy factors. This strengthens the link between elevated abundance discrepancy factors and close binarity in the nebular progenitor.

  • Planetary Nebulae what can they tell us about close binary evolution
    Eas Publications Series, 2015
    Co-Authors: D. Jones
    Abstract:

    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.