1. TDEmass – Mass inference method for tidal disruption events.
– Git repository: https://github.com/taehoryu/TDEmass

Model Description
i. Model – slow circularization
TDEmass is a tool for interpretation of Tidal Disruption Event (TDE) observations. In TDEs, a supermassive black hole at the center of a galaxy tears apart an ordinary star; the debris is placed on highly eccentric orbits and, in ways that remain controversial, ultimately produces a very bright flare. The spectrum of the optical/UV light in this flare is generally well described by a black body with temperature ~ few 10,000 K.
Using this tool, one can infer the mass of the black hole () and the mass of the star () involved in a TDE by solving two nonlinear algebraic equations derived in Ryu+2020 (https://ui.adsabs.harvard.edu/abs/2020arXiv200713765R/abstract) (Equations 9 and 10). These equations arise from a physical model for the optical/UV luminosity in which the energy for this light is generated by dissipation in shocks near the debris’ orbital apocenter. They may be written in the following form:
(1)
(2)
where refers to the observed peak UV/optical luminosity (in units of erg/s) and are the observed temperature at peak luminosity (in units of K). are are in units of and , respectively. c_{1} and are two unspecified parameters (see Section 2) below ).
is the ratio of the width of the debris’ specific energy distribution to its conventional estimate where is the stellar radius and is the order of magnitude estimate for the tidal radius, i.e., (Ryu+2020, Arxiv 2001:03501). is nonlinear, but analytic function of and . Its nonlinearity is what requires numerical solutions of these equations.
ii. Two unspecified parameters and
Our model includes two unspecified parameters, and . is the distance from the black hole at which a significant amount of energy is dissipated by shocks. Here, is the apocenter distance for the orbit of the most tightly bound debris. is the solid angle. So corresponds to the surface area of the emitting region. Note that is equivalent to what is called the “black body radius”. For fixed and , larger leads to smaller and , but the dependence is weak. However, and are sensitive to . For fixed and , with = (1.22) and with = 0.81.5.
The quantities and are coefficients poorlydetermined by current theory; we recommend setting and (default values in the code).

Code description
The code solves the equations using the following algorithm:
– Create a table of and values on a logarithmic grid in and within ranges specified by mbh_range and mstar_range. There are 500 within each mass range.
– Locate and within this table and define the uncertainty in and by the uncertainty in and .
These uncertainties are called dLobs, dLobs+, dTobs, and dTobs+.
– Find the central values of and within the ranges determined by the uncertainty in and (see find_centroid_range() in module.py for the definition of the central value)
– With the first guess, find new values of and by using the two basic equations. Iterate to convergence. The initial values of and are chosen to be the central values of and . The routine embodying this step is solver1_LT().
– If the previous step fails to converge, use the 2dimensional NewtonRaphson method to solve the equations.
The initial values of and are the central values of and . This routine is called solver2_LT().
The units in the code are:
– Luminosity(Lorb, Lobs_1, Lobs_2) = erg/s
– Temperature (Tobs, Tobs_1, Tobs_2) = K
– Black hole mass (mbh) = ( : solar mass)
– Stellar mass (mstar) =

Download and run
To download, clone the git repository using HTTP access :
https://github.com/taehoryu/TDE_mass_inference.git
To run, you first enter the directory “TDE_mass_inference”. In the directory, the code is run as
Python3 main.py
The code has three source dependencies : scipy, numpy and matplotlib

Inputs and outputs
Refer to the detailed description here (Section 3 and 4)

Issues/requests
Email address for issues/requests : udraeo@gmail.com