plons 0.0.2

PLOtting tool for Nice Simulations

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README PHANTOM PIPELINE 

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This is the README for the first python pipeline ever to reduce data of hydrodynamical simulations by use of the SPH code PHANTOM (Price, D. J., Wurster, J., Tricco, T. S., et al. 2018, PASA, 35, e031). PHANTOM returns different types of useful data files: 'wind_xxxxx'-files and '.ev'-files. The former can only be read in its raw form by the SPH visualisation tool SPLASH (Price, D. J. 2007, PASA, 24, 159; https://users.monash.edu.au/~dprice/splash/). By using SPLASH, the files can be converted to .ascii to use for reduction. The .ev-files can be use straight away, but can also be visualised using SPLASH.

PHANTOM

PHANTOM returns (full) dump files every certain timestep during the evolution of the model. These are the wind_xxxxx-files and contain the relevant data (position, velocity, mass, density, energy, temperature) of the SPH particles in the model. The last x rows of the output are the x sink particles in the model. More detailed information of the sink particles (position, velocity, mass, accreted mass, spin, angular momentum) in function of evolution time of the model, can be retrieved in the .ev files.

Pipeline - General

This pipeline is suited for binary and single AGB wind models.

By giving the directory where the models are located as input, the last full dump in .ascii and the .ev files of the sink particle(s) are reduced in order to gain relevant information about the model: (1) 2D slice plots of the density, speed and temperature are produced (face-on/orbital plane & edge-on plane). (2) 1D radial plots of the density, speed and temperature are produced (along the x-, y- and z-axes). (3) The terminal velocity in the model is calculated. (4) Four morphological parameters are determined, giving a more quantitative insight in the degree of aspherity. (5) The cummulative mass fraction and mean density are calculated in function of polar coordinate theta. This gives an indication about the degree of equatorial density enhancement (EDE). (6) Information about the orbital evolution of the binary system and accreted mass onto the companion.

Pipeline - More detailed information

This pipeline loads the wind.in and wind.setup files first. This is the general setup information of the model (configuration of the system, information of the thermodynamics, evolution time, wind outflow setup,...). Next the last full dump is loaded, and using this data, some other useful quantities are calculated (gas pressure/temperature, speed, sperical coordinates, sound speed of the gas,...). Lastly, the data of the sink particle(s) is loaded. From this file, also the period and orbital velocity of the sink particles in calculated, if the system is a binary, in function of time. The last entry in the sink data, corresponds to the full dump loaded. Therefore the position/velocity/mass/... of this last entry are also saved in the full dump data for easy usage.

NOTE: If you have paused and restarted your simulation, multiple .ev files will be constructed per sink particle. The code anticipates to this problem, but you have to say so in the code yourself: Uncomment the part starting at line 50 in the LoadSink.py script and put in the correct model.

(1)

The 2D slices in the plots are infinitely thin and calculated by using the smoothing kernel from PHANTOM. The density, speed and temperature are calculated by this method on a grid of 300*300 pixels, using the data of the 20 nearest neighbours (SPH particles) of those grid points. These plots give a visual representation of the morphology present in the AGB wind of the simulation.

(2)

In 1D, the data along the x-, y- and z-axes is constructed in the same way as explained in (1), but for a 1D grid. This results in plots of the radial structure, which is an important addition to the 2D slice plots.

(3)

The terminal velocity is in the case of the PHANTOM SPH code not an input parameter, so it needs to be calculated. Due to the morphology in the outflow of the AGB star, at a certain radius a wide range of speeds will be obtained. Therefore calculating only one value for the terminal velocity is not possible. Instead, three values are obtained, a minimum, mean and maximum terminal velocity. The method used here is binning of the speed in function of the radius of the SHP particle to the AGB star. Bins of 1AU are constructed and per bin, the minimum, mean and maximum speed is calculated. Using speed of the outer 20% of the data, three values for the terminal velocity are obtained.

NOTE: For some models (most often with slow initial wind velocity, low mass loss rate and/or low-mass companion), the interaction of the companion has not reached the outer boundary of the model. Therefore, this method will not lead to a correct terminal velocity value and thus the unphysical part of the data will be cut off. Visually, the speed profile in function of radius shows a strong, unphysical linear increase, starting with a clear twist.

(4)

In order to get some quantitative indication about the morphology of the models, two morphology parameters are currently in use: - eta = v/v_orb (see Saladino, M. I., Pols, O. R., van der Helm, E., Pelupessy, I., & Portegies Zwart, S. 2018, A&A, 618, A50; El Mellah, I., Bolte, J., Decin, L., Homan, W., & Keppens, R. 2020, arXiv e-prints, arXiv:2001.04482) - Qp = p_comp/p_wind = (M_comp v_orb) / (M_wind v_wind) (see Decin, L., Montarges, M., Richards, A. M. S., et al. 2020, Science, 369, 1497) - epsilon = e_kin/e_grav = (v_wind^2 a)/(24 G^3 M_comp^2 M_AGB)^(1/3) - Rcapt/a = (2 G M_comp)/(v_wind^2) * 1/a Depending on the value of these parameters, the model is expected to show radial/EDE/complex morphology.

Rhill = a(1-e)(M_comp/ 3M_AGB)^(1/3) Therefore, Rhill/Rcapt = epsilon, if for both radii the same v_wind is used.

VERY IMPORTANT NOTE: The parameter 'v_wind' is not unambiguously defined. Even more, if only a binary models is used, this parameter is most likely not to be contrained properly. For the different morphological parameters, multiple values for v_wind are used. For eta, different velocities/speed v are used: - terminal velocity - speed of the wind at the location of the companion For Qp and epsilon, two different values are used as v_wind: - the mean velocity of the wind at the location is used as calculated from the binning - the average of the min and max velocity at the location of the companion is used For Rcapt/a the initial wind velocity is used to get a rough indication.

Better options for v_wind would be to use the velocity of the corresponding single model as follows: - speed of the wind at the location of the companion - speed resulting from the vector sum of the speed of the wind at the location of the companion and the orbital velocity of the AGB star. These can be calculated using the output of this pipeline.

(5)

The cummulative mass fraction (CMF) is calculated in function of the polar angle theta (theta = 0.5pi is the orbital plane, theta = 0 the north pole), again by using the method of binning. Only the northern hemisphere is used, because of symmetry. Because of asymmetry along the x-axis, the positive (right) and negative (left) part according to x are also calculated seperately. Certainly for eccentric models this can differ. To calculate the CMF, only the selfsimilar part of the outflow it used, therefore a factor (called factor) is given. The inner factor * semi-major axis AU is left out in this calculation.

From this CMF, the angle is calculated where 25, 50 and 75% of the mass of the wind is present, called theta25/50/75 respectively. From this, the parameter delta is calculated, defined as (theta25-theta50)/(theta50-theta75). When this parameter is normalised to the value for the corresponding single model, it gives a measure for the degree of EDE.

Also the mean density is calculated using a similar approach as the CMF, using the method of binning. This mean density can easily be normalised to compare the morphology in different models.

(6)

In order to get information about the orbital evolution, the sink files are used (.ev), which gives relevant quantities of the sink particles in function of time. This file returns plots of the orbit, evolution of orbital separation, orbital velocity and accreted mass of the companion.