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At least 1,459 records · Page 81
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Dust-planetary boundary layer interactions amplified by entrainment and advections

Mineral dust contributes to more than half of the global aerosol loading. However, the radiative impacts of dust aerosols on planetary boundary layer (PBL) structure have not been explored sufficiently. During a typical dust storm event over Tarim Basin, dust aerosols exhibit a well-mixed distribution during the daytime in spite of a shallow layer of dust particles accumulated at higher altitudes. By contrast, nocturnal dust plumes are located near the surface due to stable stratification. We demonstrate that these differentiated vertical distributions determine the spatial heterogeneity of dust loading, radiative fluxes and PBL height variations. Dust aerosols cause daytime PBL suppression and nighttime PBL promotion through modulating surface and atmospheric radiative budgets. Specifically, dust-induced cooling effect within PBL directly inhibits the daytime PBL development. PBL suppression effect is then amplified by entrainment processes resulting in excessively low PBL height, especially for dust particles below but near the PBL top. Dust plumes weaken updrafts from PBL and downdrafts of the free atmosphere, which further reduce the entrainment mixing through attenuating horizontal and vertical advection, and eventually amplify PBL suppression. At night, near-surface dust aerosols stimulate a warm and unstable lower atmosphere, generate warm advection heating and promote the PBL development. Our study highlights the importance of specifying entrainment parameters and nighttime advection activities in quantifying the dust-PBL interactions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Glass transition temperature studies of planetary ball milled glasses: Accessing the rapidly cooled glassy state in Na 4 P 2 S 7-x O x , 0 ≤ x ≤ 7, Oxy-thio phosphate glasses

This paper details the very first in-depth study of the glass transition temperature (T g ) for planetary balled milled (PBM) Na 4 P 2 S 7-x O x (NaPSO), where 0 ≤ x ≤ 7, glasses. For 0 ≤ x ≤ 5, fully amorphous, homogeneous, and chemically reacted compositions can be prepared. For samples with 5 < x ≤ 7, partially amorphous but fully chemically reacted glass-ceramics can be produced. The reproducible, thermally cyclable onset T g and the onset crystallization temperature, T c , were investigated as a function of the composition and of the short-range order (SRO) structures of the glasses. Additionally, we examined the extreme sub-T g exothermic relaxations present due to the high energy milling processing and correspondingly high effective quenching rate. Using a differential scanning calorimeter (DSC) and scanning from well below the onset T g , the glasses are observed to relax exothermally below T g . The integrated relaxation enthalpy, ΔH rel , is ~ 0 for the x = 2 glass, but is significantly exothermic for lower and higher values of x. Once the high fictive state of these glasses has been erased by scanning to above the T g , but below the T c of the glass, the DSC scans of the glasses recover normal behavior for a normally cooled glass without any relaxation exotherm. The T g s of these glasses remain relatively constant for 0 ≤ x ≤ 3, but for glasses with 3 < x ≤ 5, T g increases sharply following the combined effects of the phosphate chain length increasing caused by the formation of bridging oxygens and the increasing concentration of more charge dense non-bridging oxygens (NBOs). For x > 5, both T g and Tc decrease sharply, becoming nearly identical at x = 7 where glass formation essentially ceases. For smaller values of x, T c increases with both chain length and the structural complexity of the composition but decreases sharply for glass-ceramics of x > 5.

36 MATERIALS SCIENCE↗
DOE OSTI2019

A new method to retrieve the diurnal variability of planetary boundary layer height from lidar under different thermodynamic stability conditions

The planetary boundary layer height (PBLH) is an important parameter for understanding the accumulation of pollutants and the dynamics of the lower atmosphere. Lidar has been used for tracking the evolution of PBLH by using aerosol backscatter as a tracer, assuming aerosol is generally well-mixed in the PBL; however, the validity of this assumption actually varies with atmospheric stability. This is demonstrated here for stable boundary layers (SBL), neutral boundary layers (NBL), and convective boundary layers (CBL) using an 8-year dataset of micropulse lidar (MPL) and radiosonde (RS) measurements at the ARM Southern Great Plains, and MPL at the GSFC site. Due to weak thermal convection and complex aerosol stratification, traditional gradient and wavelet methods can have difficulty capturing the diurnal PBLH variations in the morning and forenoon, as well as under stable conditions generally. Here a new method is developed that combines lidar-measured aerosol backscatter with a stability dependent model of PBLH temporal variation (DTDS). The latter helps “recalibrate” the PBLH in the presence of a residual aerosol layer that does not change in harmony with PBL diurnal variation. The hybrid method offers significantly improved PBLH detection, with better correlation and smaller biases, under most thermodynamic conditions, especially for SBL and CBL. Relying on the physical process of PBL diurnal development, different schemes are developed for growing, maintenance, and decaying periods. Comprehensive evaluation of this new method shows much better tracking of diurnal PBLH variation and significantly smaller biases under various pollution levels.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Remote sensing of planetary boundary layer from ground and space: Structure, thermodynamics, and boundary layer clouds

The planetary boundary layer (PBL) is a critical interface between Earth's surface and atmosphere, influencing atmospheric convection, weather patterns, and air quality. Recognized by the 2017 National Academies of Sciences, Engineering, and Medicine Earth Science Decadal Survey as an Incubation Targeted Observable, high-quality and effective observation of the PBL has become a priority. This paper reviews surface-based and satellite remote sensing techniques for characterizing PBL features, including PBL height (PBLH), boundary layer thermodynamics, turbulence, and boundary layer clouds (BLCs). These elements are treated as interconnected aspects of the PBL system, while recognizing that different instruments retrieve different physical manifestations of the PBL. The review summarizes recent advances and limitations in Micro-Pulse Lidar (MPL), Doppler lidar, Raman lidar, Differential Absorption Lidar (DIAL), ceilometers, wind profilers, GNSS Radio Occultation, radar, and hyperspectral sounders. These observations help trace dynamic processes within the PBL and link PBL structure to broader weather and climate processes. The review also highlights persistent observational gaps over oceans, remote land, and polar regions, where continuous surface-based profiling is sparse. By comparing instrument capabilities, practical limitations, and interpretation issues, this review emphasizes the need for integrated remote sensing approaches and careful definition of the retrieved PBL quantities.

Boundary layer clouds↗
DOE OSTI2018

Benchmarking Geant4 for simulating galactic cosmic ray interactions within planetary bodies

Galactic cosmic rays undergo complex nuclear interactions with nuclei within planetary bodies that have little to no atmosphere. Radiation transport simulations are a key tool used in understanding the neutron and gamma-ray albedo coming from these interactions and tracing these signals back to geochemical composition of the target. In this paper, we study the validity of the code Geant4 for simulating such interactions by comparing simulation results to data from the Apollo 17 Lunar Neutron Probe Experiment. Different assumptions regarding the physics are explored to demonstrate how these impact the Geant4 simulation results. In general, all of the Geant4 results over-predict the data, however, certain physics lists perform better than others. Finally, in addition, we show that results from the radiation transport code MCNP6 are similar to those obtained using Geant4.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Look Up: Probing the Vertical Profile of New Particle Formation and Growth in the Planetary Boundary Layer With Models and Observations

Abstract The processes of new particle formation (NPF) and growth are important contributors to cloud condensation nuclei (CCN) concentrations, and CCN are important for climate from their impact on planetary radiative forcing. While the general ubiquity and importance of NPF is understood, the vertical extent and governing mechanisms of NPF and growth in the lower troposphere are uncertain. We present an analysis of four NPF events and two non‐NPF events during the HI‐SCALE field campaign at the Southern Great Plains observatory in Oklahoma, USA. First, we analyzed airborne and ground‐based observations of aerosol and gas‐phase properties. Second, we used a column aerosol chemistry and microphysics model to probe factors that influence the vertical profile of NPF. During HI‐SCALE, we found several instances of enhanced NPF occurring several hundred meters above the surface; however, the spatio‐temporal characteristics of the observed NPF made comparisons between airborne‐ and ground‐based observations difficult. The model represented the observed NPF (or lack of NPF) and particle growth at the surface to final diameters within 10 nm. The model predicted enhanced NPF rates in the upper mixed layer, and this enhancement is primarily due to the temperature dependence in the NPF schemes, but this was also dependent on the vertical profile of gas‐phase precursors measured during HI‐SCALE. We found vertical mixing in the model either enhanced or suppressed NPF rates, aerosol number concentrations, and particle growth rates at the surface. Finally, our analysis provides insights for future field campaigns and modeling efforts investigating the vertical profile of NPF.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Evaluation of the Planetary Boundary Layer Height From ERA5 Reanalysis With MOSAiC Observations Over the Arctic Ocean

The planetary boundary layer height (PBLH) is a crucial indicator reflecting the region of the atmosphere characterized by continuous turbulence. Here, we use radiosonde and surface meteorological observations (4–7 times per day, year-round measurements) during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition to derive the PBLH (PBLH MOSAiC ), and further evaluate the PBLH from the ERA5 reanalysis (PBLH ERA5 ). Comparisons between PBLH MOSAiC and PBLH ERA5 from different perspectives reveal that: (a) The overestimation of PBLH ERA5 when the sea ice concentration is >90% is significant with the centered root mean squared error reaching up to 201 m; (b) The difference between the two products is notably pronounced in cold seasons, while it is comparatively diminished in warm seasons; (c) In neutral boundary layers, differences in PBLH ERA5 are larger compared with stable and convective boundary layers. In addition, the analysis of error sources indicates that the bias of PBLH ERA5 is sensitive to the bias of vertical thermal structure and wind speed profiles in ERA5 data sets in all conditions. Finally, we find a Random Forest model effectively reduces the bias of PBLH ERA5 with the index of agreement reaching up to 0.71 in the test data set, while a multiple linear regression demonstrates comparable performance to the Random Forest model.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Multi‐Sensor Trajectory Reconstruction of the 24 April 2025 Alaska Fireball and Implications for Planetary Defense

On 24 April 2025 at 18:30:57 UTC, a bright daytime fireball over Southcentral Alaska was detected by 37 seismic stations, 16 single infrasound sensors, and four infrasound arrays, yielding 30 ballistic and multiple fragmentation arrivals. Here, the unprecedented density of seismoacoustic coverage enabled detailed reconstruction of the event using acoustic signals, with fragmentation source locations further guiding the identification of Doppler weather radar signatures of a meteorite fall. Incorporation of a radar-derived terminal point yielded a final trajectory solution, which agreed closely with an independent optical trajectory solution from video analysis. The reconstructed entry parameters from seismoacoustic analysis indicate a velocity of 25.3 km/s, an entry angle of 19°, and an energy release of ∼38 t TNT equivalent. Assuming a chondritic composition, the pre-entry object diameter was ∼0.7 m. Using orbital parameters from the optical solution, we estimate meteoroid composition as most likely an L-type ordinary chondrite. The event occurred in the sub-Arctic, where space-based optical systems face challenges in detection, demonstrating the critical role of dense ground-based seismoacoustic networks in characterizing high-latitude atmospheric entries. This uniquely well-recorded event demonstrates the capability of dense seismoacoustic networks to constrain bolide trajectories, energetics, and fragmentation, with radar and optical data providing critical confirmation and complementary perspectives. These results bridge the methodological gap between planetary-defense monitoring of natural impactors and space-traffic analyses of artificial reentries, illustrating how multi-sensor integration can deliver calibration-grade trajectories even for unpredicted events.

Fireball↗
DOE OSTI2023

Rate coefficients for rotational state-to-state transitions in H 2 O + H 2 O collisions for cometary and planetary applications, as predicted by mixed quantum-classical theory

We present new calculations of collision cross sections for state-to-state transitions between the rotational states in an H 2 O + H 2 O system, which are used to generate a new database of collisional rate coefficients for cometary and planetary applications. Calculations were carried out using a mixed quantum-classical theory approach that is implemented in the code MQCT. The large basis set of rotational states used in these calculations permits us to predict thermally averaged cross sections for 441 transitions in para- and ortho-H 2 O in a broad range of temperatures. It is found that all state-to-state transitions in the H 2 O + H 2 O system split into two well-defined groups, one with higher cross-section values and lower energy transfer, which corresponds to the dipole-dipole driven processes. The other group has smaller cross sections and higher energy transfer, driven by higher-order interaction terms. We present a detailed analysis of the theoretical error bars, and we symmetrized the state-to-state transition matrixes to ensure that excitation and quenching processes for each transition satisfy the principle of microscopic reversibility. We also compare our results with other data available from the literature for H 2 O + H 2 O collisions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Conductivity and dissociation in liquid metallic hydrogen and implications for planetary interiors

Liquid metallic hydrogen (LMH) is the most abundant form of condensed matter in our solar planetary structure. The electronic and thermal transport properties of this metallic fluid are of fundamental interest to understanding hydrogen’s mechanism of conduction, atomic or pairing structure, as well as the key input for the magnetic dynamo action and thermal models of gas giants. Here, we report spectrally resolved measurements of the optical reflectance of LMH in the pressure region of 1.4–1.7 Mbar. We analyze the data, as well as previously reported measurements, using the free-electron model. Fitting the energy dependence of the reflectance data yields a dissociation fraction of 65 ± 15%, supporting theoretical models that LMH is an atomic metallic liquid. We determine the optical conductivity of LMH and find metallic hydrogen’s static electrical conductivity to be 11,000–15,000 S/cm, substantially higher than the only earlier reported experimental values. Here, the higher electrical conductivity implies that the Jovian and Saturnian dynamo are likely to operate out to shallower depths than previously assumed, while the inferred thermal conductivity should provide a crucial experimental constraint to heat transport models.

08 HYDROGEN↗
DOE OSTI2012

SWIFT/UVOT PHOTOMETRY OF THE PLANETARY NEBULA WeBo 1: UNMASKING A FAINT HOT COMPANION STAR

We present an analysis of over 150 ks of data on the planetary nebula WeBo 1 (PN G135.6+01.0) obtained with the Swift Ultraviolet Optical Telescope (UVOT). The central object of this nebula has previously been described as a late-type K giant barium star with a possible hot companion, most likely a young pre-white dwarf. UVOT photometry shows that while the optical photometry is consistent with a large cool object, the near-ultraviolet (NUV) photometry shows far more UV flux than could be produced by any late-type object. Using model stellar atmospheres and a comparison to UVOT photometry for the pre-white dwarf PG 1159-035, we find that the companion has a temperature of at least 40,000 K and a radius of, at most, 0.056 R{sub Sun }. While the temperature and radius are consistent with a hot compact stellar remnant, they are lower and larger, respectively, than expected for a typical young pre-white dwarf. This likely indicates a deficiency in the assumed UV extinction curve. We find that higher temperatures more consistent with expectations for a pre-white dwarf can be derived if the foreground dust has a strong 'blue bump' at 2175 A and a lower R{sub V}. Our results demonstrate the ability of Swift to both uncover and characterize hot hidden companion stars and to constrain the UV extinction properties of foreground dust based solely on UVOT photometry.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

A DETAILED SPATIOKINEMATIC MODEL OF THE CONICAL OUTFLOW OF THE MULTIPOLAR PLANETARY NEBULA NGC 7026

We present extensive, long-slit, high-resolution coverage of the complex planetary nebula (PN) NGC 7026. We acquired 10 spectra using the Manchester Echelle Spectrometer at San Pedro Martir Observatory in Baja California, Mexico, and each shows exquisite detail, revealing the intricate structure of this object. Incorporating these spectra into the three-dimensional visualization and kinematic program SHAPE and using Hubble Space Telescope images of NGC 7026, we have produced a detailed structural and kinematic model of this PN. NGC 7026 exhibits remarkable symmetry consisting of three lobe pairs and four sets of knots, all symmetrical about the nucleus and displaying a conical outflow. Comparing the three-dimensional structure of this nebula to recent XMM-Newton X-ray observations, we investigate the extended X-ray emission in relation to the nebular structure. We find that the X-ray emission, while confined to the closed, northern lobes of this PN, shows an abrupt termination in the middle of the southeast lobe, which our long slit data show to be open. This is where the shocked fast wind seems to be escaping the interior of the nebula and the X-ray emission rapidly cools in this region.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

A search for planetary Nebulae with the Sloan digital sky survey: the outer regions of M31

We have developed a method to identify planetary nebula (PN) candidates in imaging data of the Sloan Digital Sky Survey (SDSS). This method exploits the SDSS's five-band sampling of emission lines in PN spectra, which results in a color signature distinct from that of other sources. Selection criteria based on this signature can be applied to nearby galaxies in which PNe appear as point sources. We applied these criteria to the whole area of M31 as scanned by the SDSS, selecting 167 PN candidates that are located in the outer regions of M31. The spectra of 80 selected candidates were then observed with the 2.2 m telescope at Calar Alto Observatory. These observations and cross-checks with literature data show that our method has a selection rate efficiency of about 90%, but the efficiency is different for the different groups of PN candidates. In the outer regions of M31, PNe trace different well-known morphological features like the Northern Spur, the NGC 205 Loop, the G1 Clump, etc. In general, the distribution of PNe in the outer region 8 < R < 20 kpc along the minor axis shows the {sup e}xtended disk{sup —}a rotationally supported low surface brightness structure with an exponential scale length of 3.21 ± 0.14 kpc and a total mass of ∼10{sup 10} M {sub ☉}, which is equivalent to the mass of M33. We report the discovery of three PN candidates with projected locations in the center of Andromeda NE, a very low surface brightness giant stellar structure in the outer halo of M31. Two of the PNe were spectroscopically confirmed as genuine PNe. These two PNe are located at projected distances along the major axis of ∼48 Kpc and ∼41 Kpc from the center of M31 and are the most distant PNe in M31 found up to now. With the new PN data at hand we see the obvious kinematic connection between the continuation of the Giant Stream and the Northern Spur. We suggest that 20%-30% of the stars in the Northern Spur area may belong to the Giant Stream. In our data we also see a possible kinematic connection between the Giant Stream and PNe in Andromeda NE, suggesting that Andromeda NE could be the core or remnant of the Giant Stream. Using PN data we estimate the total mass of the Giant Stream progenitor to be ≈10{sup 9} M {sub ☉}. About 90% of its stars appear to have been lost during the interaction with M31.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Dusty disks around central stars of planetary nebulae

Only a few percent of cool, old white dwarfs (WDs) have infrared excesses interpreted as originating in small hot disks due to the infall and destruction of single asteroids that come within the star's Roche limit. Infrared excesses at 24 μm were also found to derive from the immediate vicinity of younger, hot WDs, most of which are still central stars of planetary nebulae (CSPNe). The incidence of CSPNe with this excess is 18%. The Helix CSPN, with a 24 μm excess, has been suggested to have a disk formed from collisions of Kuiper belt-like objects (KBOs). In this paper, we have analyzed an additional sample of CSPNe to look for similar infrared excesses. These CSPNe are all members of the PG 1159 class and were chosen because their immediate progenitors are known to often have dusty environments consistent with large dusty disks. We find that, overall, PG 1159 stars do not present such disks more often than other CSPNe, although the statistics (five objects) are poor. We then consider the entire sample of CSPNe with infrared excesses and compare it to the infrared properties of old WDs, as well as cooler post-asymptotic giant branch (AGB) stars. We conclude with the suggestion that the infrared properties of CSPNe more plausibly derive from AGB-formed disks rather than disks formed via the collision of KBOs, although the latter scenario cannot be ruled out. Finally, there seems to be an association between CSPNe with a 24 μm excess and confirmed or possible binarity of the central star.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

A detailed study of the structure of the nested planetary nebula, Hb 12, the Matryoshka nebula

We present near-IR, integral field spectroscopic observations of the planetary nebula (PN) Hb 12 using Near-infrared Integral Field Spectrograph (NIFS) on Gemini-North. Combining NIFS with the adaptive optics system Altair, we provide a detailed study of the core and inner structure of this PN. We focus the analysis in the prominent emission lines [Fe II] (1.6436 μm), He I (2.0585 μm), H{sub 2} (2.1214 μm), and Br{sub γ} (2.16553 μm). We find that the [Fe II] emission traces a tilted system of bipolar lobes, with the northern lobe being redshifted and the southern lobe blueshifted. The [Fe II] emission is very faint at the core and only present close to the systemic velocity. There is no H{sub 2} emission in the core, whereas the core is prominent in the He I and Br{sub γ} recombination lines. The H{sub 2} emission is concentrated in equatorial arcs of emission surrounding the core and expanding at ∼30 km s{sup –1}. These arcs are compared with Hubble Space Telescope images and shown to represent nested loops belonging to the inner sections of a much larger bipolar structure that replicates the inner one. The He I and Br{sub γ} emission from the core clearly show a cylindrical central cavity that seems to represent the inner walls of an equatorial density enhancement or torus. The torus is 0.''2 wide (≡200 AU radius at a distance of 2000 pc) and expanding at ≤30 km s{sup –1}. The eastern wall of the inner torus is consistently more intense than the western wall, which could indicate the presence of an off-center star, such as is observed in the similar hourglass PN, MyCn 18. A bipolar outflow is also detected in Br{sub γ} emerging within 0.''1 from the core at ∼ ± 40 km s{sup –1}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

HUBBLE SPACE TELESCOPE SNAPSHOT SEARCH FOR PLANETARY NEBULAE IN GLOBULAR CLUSTERS OF THE LOCAL GROUP

Single stars in ancient globular clusters (GCs) are believed incapable of producing planetary nebulae (PNs), because their post-asymptotic-giant-branch evolutionary timescales are slower than the dissipation timescales for PNs. Nevertheless, four PNs are known in Galactic GCs. Their existence likely requires more exotic evolutionary channels, including stellar mergers and common-envelope binary interactions. I carried out a snapshot imaging search with the Hubble Space Telescope (HST) for PNs in bright Local Group GCs outside the Milky Way. I used a filter covering the 5007 Å nebular emission line of [O iii], and another one in the nearby continuum, to image 66 GCs. Inclusion of archival HST frames brought the total number of extragalactic GCs imaged at 5007 Å to 75, whose total luminosity slightly exceeds that of the entire Galactic GC system. I found no convincing PNs in these clusters, aside from one PN in a young M31 cluster misclassified as a GC, and two PNs at such large angular separations from an M31 GC that membership is doubtful. In a ground-based spectroscopic survey of 274 old GCs in M31, Jacoby et al. found three candidate PNs. My HST images of one of them suggest that the [O iii] emission actually arises from ambient interstellar medium rather than a PN; for the other two candidates, there are broadband archival UV HST images that show bright, blue point sources that are probably the PNs. In a literature search, I also identified five further PN candidates lying near old GCs in M31, for which follow-up observations are necessary to confirm their membership. The rates of incidence of PNs are similar, and small but nonzero, throughout the GCs of the Local Group.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

PLANETARY NEBULAE DETECTED IN THE SPITZER SPACE TELESCOPE GLIMPSE 3D LEGACY SURVEY

We used the data from the Spitzer Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) to investigate the mid-infrared (MIR) properties of planetary nebulae (PNs) and PN candidates. In previous studies of GLIMPSE I and II data, we have shown that these MIR data are very useful in distinguishing PNs from other emission-line objects. In the present paper, we focus on the PNs in the field of the GLIMPSE 3D survey, which has a more extensive latitude coverage. We found a total of 90 Macquarie-AAO-Strasbourg (MASH) and MASH II PNs and 101 known PNs to have visible MIR counterparts in the GLIMPSE 3D survey area. The images and photometry of these PNs are presented. Combining the derived IRAC photometry at 3.6, 4.5, 5.8, and 8.0 {mu}m with the existing photometric measurements from other infrared catalogs, we are able to construct spectral energy distributions (SEDs) of these PNs. Among the most notable objects in this survey is the PN M1-41, whose GLIMPSE 3D image reveals a large bipolar structure of more than 3 arcmin in extent.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

FORMATION OF BIPOLAR PLANETARY NEBULAE BY INTERMEDIATE-LUMINOSITY OPTICAL TRANSIENTS

We present surprising similarities between some bipolar planetary nebulae (PNe) and eruptive objects with peak luminosity between novae and supernovae. The latter group is termed ILOT for intermediate-luminosity optical transients (other terms are intermediate-luminosity red transients and red novae). In particular, we compare the PN, NGC 6302 and the pre-PNe OH231.8+4.2, M1-92, and IRAS 22036+5306 with the ILOT NGC 300 OT2008-1. These similarities lead us to propose that the lobes of some (but not all) PNe and pre-PNe were formed in an ILOT event (or several close sub-events). We suggest that in both types of objects the several months long outbursts are powered by mass accretion onto a main-sequence (MS) companion from an asymptotic giant branch (AGB, or extreme-AGB) star. Jets launched by an accretion disk around the MS companion shape the bipolar lobes. Some of the predictions that result from our comparison is that the ejecta of some ILOTs will have morphologies similar to those of bipolar PNe, and that the central stars of the PNe that were shaped by ILOTs should have an MS binary companion with an eccentric orbit of several years long period.

79 ASTRONOMY AND ASTROPHYSICS↗