I am a PhD candidate (due mid 2016) in the Department of Astronomy and Astrophysics at the University of California Santa Cruz. In general, I am interested in theoretical and computational astrophysics, with an emphasis on massive stars and supernovae. My primary advisor is Stan Woosley, and my thesis committee members are Alex Heger, Gary Glatzmeier and Mark Krumholz. I am a member of the SciDac team.
Beside research work I am passionate about blockchain technology, science outreach and wrestling. I am a native of Mongolia.


office: Natural Sciences II, #185
e-mail: sukhbold [at] ucolick [dot] org
OpenPGP: publick key, fingerprint:CE71 BB9A FD02 0F79 F6A7 0D20 E8E3 F7B8 1404 D180

Current Research

Following is a summary of projects that I am working on right now. For the full list of past work please see my CV and Pulications.


Collaborators: Thomas Ertl, Stan Woosley, Justin Brown, Thomas Janka
Status: submitted to The Astrophysical Journal

Fig. 12 of SEWBJ (2015). The explosion outcomes are shown for five different 'engines' calibrated to SN1987A. Engines are listed in increasing strength.

In Sukhbold & Woosley (2014), we have explored in detail the systematics of presupernova core structure as a function of initial mass, using a number of fine-meshed surveys. The variation of the core compactness with mass is found to be robustly non-monotonic and is heavily dependent on the complex interplay of shell burning episodes during the advanced stages of evolution. In this work, we are studying the explosion outcomes of 200 progenitor models between 9-120Msun through a novel approach. Instead of placing the piston in an arbitrary location and dial-in the final kinetic energy at infinity, we first create series of calibrated (to SN1987A and SN1054 observations) ''engines'' from the combination of one-zone analytic core-cooling model and approximate neutrino-transport. Then we place these engines inside each progenitor, and follow the evolution until the remnant and ejecta are clearly separated (neutrino-radiation hydrodynamics is calculated with Prometheus-HOTB as described in Ertl et al. 2015). Once we give up the luxury of exploding any star in any way we want, now the outcomes are based on the neutrino-driven mechanism and therefore heavily dependent on the progenitor structure - i.e. each successful explosion for each engine has a different energy, remnant mass and nucleosynthesis. As predicted in prior work on progenitors, most stars explode below 20Msun with significant modulation, and above there is a sea of black hole formation with a distinct island of explosion near 27Msun. We map the explosion results back into KEPLER to post-process the resulting nucleosynthesis (excluding r-process but including Type-Ia contribution) with a large network, and follow the light curves through flux-limited diffusion.


Collaborators: Stan Woosley, Ke-Jung Chen
Status: paper on multi-D study is close to submission, the 1D study is in preparation.

Two dimensional CASTRO results for a magnetar powered supernova explosion of a bare CO core. The density profile is shown at t=0, 800, 1600 and 2400 seconds since preSN.

Here we explore in one and two dimensions, the properties of luminous supernovae whose light curves might be powered by embedded magnetars. Using the 1D implicit hydrodynamic code KEPLER we have calculated a large library of models based on both bare CO cores and full hydrogenic progenitors. A simple dipole formula is used for energy deposition in stars that, in most cases, have already been artificially exploded by a parametric piston. Good agreement with observations can be found in numerous cases, but a troubling feature for some of the models is the non-homologous expansion of the supernova when the magnetar energy is comparable to the supernova energy. A sample of such cases are explored in two dimensions using the compressible hydrodynamic code CASTRO, and we demonstrate the density spikes seen in one dimension result in the development of Rayleigh-Taylor and nonlinear deceleration instabilities, which drastically influence the morphology and mixing in the ejecta.


Collaborators: Casey Meakin, Zeyana Musthafa, Hassen Yesuf
Status: in preparation

Figure 1 of Meakin et al. (2011) - overshoot parameter estimates from detached Eclipsing Binaries (diamonds) and asteroseismological data (triangles). The values adopted by Girardi et al. (2000) and Pietrinferni et al. (2004) for populations synthesis are labeled G2000 and P2004. The mass uncertainties for the eclipsing binary data is negligible on the log(M) scale used. It is one big mess!

Our distant goal in this project is to tackle the problem of mixing at the boundaries in 1D calculations. Traditionally such situations are handled with the "step" or exponential overshooting prescriptions within the Mixing Length Theory (MLT) formalism. Since these phenomenological appoaches have little physical basis, the associated free-parameters are hardly constrained by the observations. In this work, we are applying the high precision data from detached eclipsing binary systems coupled with Bayesian statistics to constrain and compare various mixing models in 1D calculations.


Sukhbold, T., Ertl, T., Woosley, S., Brown, J., Janka, H.-T. (2015)

Note that the work is undergoing peer-review. The presupernova progenitor models, explosion results, yield tables and light curves are available through following anonymous FTP server. Please feel free to request if you need anything more specific.

Access the server by following command:
ftp nabu.ucolick.org

the username and password are both anonymous. Download files using get and when you're done do quit or just close the session. Let me know if you experience any trouble. Currently this dataset is available through this dropbox link, MPA server, and after peer-review it will also be available on the ApJ server.

The largest files are the progenitor models and others are just set of small tables. Please see the README file for a practical description of the data:
If you end up using our data, please consider letting us know about your project!

Sukhbold & Woosley (2014)

The model sets listed below are available upon request:

Table 1 of the paper.
Here note that the S-series models are already included in SEWBJ (2015) data release through the ftp server.


As part of the magnetar powered SNe project I am writing a 3D monte-carlo radiation transport code for gamma-ray transport (in julia) and GUI lightcurve fitting routine (in python). These will be available here as soon as the paper gets published.

When I am not doing research

Science outreach

On the way to distribute educational telescopes in Govi-Altai province of Mongolia.
Beside my professional research work I deeply enjoy doing science outreach activities. Unfortunately being an astrophysics graduate student is already very demanding, and I don't usually have much time for this. Between 2012-2013 I was one of the telescope czars at the department and organized number of public star parties. In 2014 I joined the inmate education program headed by Mark Krumholz, and taught math to inmates of the Santa Cruz County Jail. In 2015, I finalized my project that brought telescopes to schools in rural parts of Mongolia. Click here to see the university news coverage.


Relic from the 26-gpu cluster. Now a small piece of it became the ftp-server.
I've discovered bitcoin in mid 2012, and fell in a deep love since then. For some time I used to do heavy amount of mining, until I couldn't bare the heat and electricity bills. At one point, I was mining with 26 GPUs. In 2013-14 I have tried to start a bitcoin club at UCSC, and even tried to install bitcoin ATM machine on campus; unfortunately the reception was less than welcome. Nowadays when I get time, I play around with biometric sensors on the Arduino platform, in hope of incorporating them into a hardware wallet.
I have little doubt that in my lifetime we will witness blockchain-like decentralized technologies taking over all aspects of our lives - not just in finance and economy, but in politics and probably in science as well.

Mongol Wrestling

Wrestling is a huge part of Mongol culture, and like most Mongol men I love wrestling. It doesn't have any weight class, and also no limits on space and itme. Mongols living in U.S. organize annual competitions and I tend to compete every other year, but without much notable success ;-P . Here is a picture from 2010 competition held in Chicago.

Click here for some pro level action.

My Name

Lot of people ask me the meaning of my name. In Mongolia people go by a single name - the part "Tuguldur" is mine, and I took my mother's name "Sukhbold" as my last (it used to be a bit awkward to have my papers referenced by my mother's name) "Tuguldur" is an old Mongol name and it loosely means perfect/elegant.
The oldest person (that I know of) who had this name is Nikola Tegulder ( who later changed it to Ahmed Tegulder). He was great-grandson of Chinggis Khan and the ruler of Ilkhanate, small part of Mongol Empire in 13th century (current day Iran and Iraq). He reigned only for 2 years and was executed by his nephew for spreading islam. According to the Wiki article:
Tekuder (in orange dress) meeting his finance minister.
Wikimedia Commons
Tekuder sent a friendly letter to the Mamluk sultan and wished for peace. His conversion to Islam and good ties with the Mamluks were not viewed well by Mongol nobles. When Arghun received no reply, he declared war against Tekuder. Tekuder requested help from the Mamluk Sultan but the Mamluks did not fully co-operate with Tekuder. Having a small and inferior army, Tekuder was defeated by Arghun's larger army, and he was eventually executed on August 10, 1284.
But I am sure he was a cool guy.