Welcome

I am currently Associate Director for the DIRAC Institute at the University of Washington, Seattle, where I do research at the interface of Astronomy and Data Science. I am particularly interested in how we can use modern statistical tools and machine learning methods to learn about the universe, especially about black holes and neutron stars. Previously, I was a Moore-Sloan Data Science Fellow at New York University's Center for Data Science. Before that, I completed a PhD thesis on magnetar bursts with Anna Watts and Michiel van der Klis at the Anton Pannekoek Institute for Astronomy of the University of Amsterdam. Please feel free to look around my website and say hi!
I am also (very occasionally) writing a blog on things I find interesting. Currently it's mainly a log of my continued experiences in organizing hackathons, but I am hoping to branch out to other topics in the near future. I'd love to hear from you if you have any ideas, comments and suggestions on any of the posts.

(X-ray) Astronomy and Data Science

At the moment, I am particularly interested in the application of statistical methods and machine learning in astronomy, especially in time series data taken with X-ray and gamma-ray satellites. At these wavelengths, one can look at some of the most energetic and violent events in the universe: black holes accreting gas from an orbiting star, highly magnetized neutron stars undergo catastrophic outbursts of energy that shake the whole star, and massive stellar explosions that are the brightest events in the universe. There is one thing all these phenomena have in common: they are transient, that is, their brightness varies with time, sometimes by a factor of a hundred or a thousand. Studying in detail how they vary with time can help us understand the physical processes that produced the variability in the first place. My interest is in developing and applying methods for this purpose to help us get the most information out of the data we gather.

My other interest lies in how we can use new computational techniques to help us mitigate the effect of the telescopes and detectors we use on the inferences we gather about astronomical sources. Whenever we observe an astronomical object, the telescope and the detector leave imprints on the data we gather, often in the form of noise or distortions. Some of these sources of noise and distortion we can measure in the lab, or calibrate once the telescope starts taking data, but this isn't true for all types of noise or distortion. For those where we don't know exactly what the detector does to our data, we need to take the effects into account during data analysis, or the results we get from the data will be biased. I am interested in finding new ways to help us make our data analysis better in the presence of difficult sources of noise or distortion and I am currently working on new techniques for two effects that affect X-ray detectors: dead time and pile-up.

Finally, I also like to think about how we can help the astronomy community learn data science, and how we can use data science to help the community. With colleagues from UW Seattle, New York University and UC Berkeley, I co-organize AstroHackWeek, a five-day workshop that is a cross of a summer school and a hackathon. Typically, we organize 4-5 tutorials on data science-relevant topics from statistics, machine learning, open-source software development, data visualization etc., and leave the afternoons free for project work, brainstorming and collaboration building. With colleagues who organize Neuro Hack Week and GeoHackWeek, we recently wrote a paper about the concept of hack weeks and its place in academia. In the context of workshop organization, I also think about participant selection a lot, and am co-author of a software package called Entrofy that's aimed at making participant selection more equitable and transparent.

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Magnetar Research

For my PhD thesis, the main focus of my research rested on magnetars. These are neutron stars--the ultra-dense remnants of some types of stellar explosion (supernova)--that have exceptionally strong magnetic fields: about fourteen orders of magnitude stronger than that of the Earth! Neutron stars are one of the prime target for studying nuclear physics at densities and pressures that we cannot produce on Earth. Similarly, because their magnetic fields are far stronger than anything reproducible in a laboratory, we can use them to study unique quantum field effects only believed to be in effect in fields this strong.

In practice, I studied bursts and flares from magnetars. Once in a while, we see bright blips of hard X-ray light that only last for a fraction of a second. Over the years, we have gathered thousands of such blips (called recurrent bursts) from several of these magnetars. Very, very rarely, they also show extremely bright outbursts in X-rays called giant flares. These are so bright that they can swamp our X-ray telescopes with light, and the gamma-ray photons of one of them even caused a measurable depression in Earth's magnetic field! These giant flares are a treasure trove for studying neutron stars and dense matter physics, because during the course of a flare, we have seen the brightness vary in periodic patterns. These patterns are so telling that we believe they've been caused by star quakes: effectively, the entire solid crust (neutron stars have solid crystal crusts, unlike normal stars) twists and shakes, something we can measure in the light that we see. In the same way that geoscientists study the earth's interior by measuring the waves travelling through it during an earthquake, we hope to be able to study the interior of neutron stars by studying the waves during a star quake.

While we have measured these waves in giant flares, these flares are rare, so data is scarce. My main task during my PhD was to search for these waves in the much shorter recurrent bursts. This task is technically challenging, because the methods we have for finding them were not designed for that particular task. Here is a simple comparison: imagine standing at a still pond. When you throw in a stone, you will see the ripples the stone created in the surface. Now imagine standing at the bow of a ship during a storm, performing the same experiment. The sea will be churning, there will be large waves and peaks and troughs, and that will make seeing the ripples created by the stone much more difficult. Our methods were designed largely for situations analogous to the still pond. The magnetar bursts I am studying, however, are more like a stormy sea! Most of my PhD research was dedicated to making our methods work (or, in my case, use a new method!) in the latter case, which can not only be applied to magnetars, but to other bright bursts as well (for example gamma-ray bursts or solar flares). We did find waves in the shorter bursts in the end, which gives us more data points to constrain theoretical models. Besides, we are still working to make those methods better, and we have not finished the search yet, so there may be more to come in the future!

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Publications

1709.09666: On the Statistical Properties of Cospectra
D. Huppenkothen, M. Bachetti submitted to The Astrophysical Journal

1611.01332: Using machine learning to explore the long-term evolution of GRS 1915+105
D. Huppenkothen, L.M. Heil, D.W. Hogg, A. Mueller Monthly Notices of the Royal Astronomical Society, Volume 466, Issue 2, p.2364-2377

1610.08653: Detection of Very Low-frequency, Quasi-periodic Oscillations in the 2015 Outburst of V404 Cygni
D. Huppenkothen, G. Younes, A. Ingram, C. Kouveliotou, E. Göğüş, M. Bachetti, C. Sánchez-Fernández, J. Chenevez, S. Motta, M. van der Klis, J. Granot, N. Gehrels, E. Kuulkers, J.A. Tomsick, D.J. Walton The Astrophysical Journal, Volume 834, 17 pp. (2017)

1501.05251: Dissecting Magnetar Variability with Bayesian Hierarchical Models
D. Huppenkothen, B. Brewer, D.W. Hogg, I. Murray, M. Frean, C. Elenbaas, A.L. Watts, Y. Levin, A. van der Horst, C. Kouveliotou; The Astrophysical Journal, Volume 810, 21 pp. (2015)

1409.7642: Quasi-periodic Oscillations in Short Recurring Bursts of Magnetars SGR 1806–20 and SGR 1900+14 Observed with RXTE
D. Huppenkothen, L.M. Heil, A.L. Watts, E. Göğüş; The Astrophysical Journal, Volume 795, 11 pp. (2014)

1408.0734: Intermittency and Lifetime of the 625 Hz Quasi-periodic Oscillation in the 2004 Hyperflare from the Magnetar SGR 1806-20 as Evidence for Magnetic Coupling between the Crust and the Core
D. Huppenkothen, A.L. Watts, Y. Levin, The Astrophysical Journal, Volume 793 (2014)

1404.2756: Quasi-Periodic Oscillations in the Short Recurring Bursts of the Soft Gamma Repeater J1550-5418
D. Huppenkothen, C. D'Angelo, A.L. Watts, L. Heil, M. van der Klis, A.J. van der Horst, C. Kouveliotou, M.G. Baring, E. Göğüş, J. Granot, Y. Kaneko, L. Lin, A. von Kienlin, G. Younes, The Astrophysical Journal, Volume 787, (2014), arxiv 1404.2756

1212.1011: Quasi-Periodic Oscillations and Broadband Variability in Short Magnetar Bursts
D. Huppenkothen, A.L. Watts, M. van der Klis, C. Kouveliotou, E. Göğüş, J. Granot, S. Vaughan, M.H. Finger, The Astrophysical Journal 768 (2013), L87-L112

1707.02922:
Magnetar giant flare high-energy emission C. Elenbaas, D. Huppenkothen, C. Omand, A.L. Watts, E. Bissaldi, I. Caiazzo, J. Heyl, Monthly Notices of the Royal Astronomical Society, Volume 471, Issue 2, p.1856-1872

1702.04370:
X-Ray and Radio Observations of the Magnetar SGR J1935+2154 during Its 2014, 2015, and 2016 Outbursts G. Younes, C. Kouveliotou, A. Jaodand, M.G. Baring, A.J. van der Horst, A.K. Harding, J.W.T. Hessels, N. Gehrels, R. Gill, D. Huppenkothen, J. Granot, E. Göğüş, L. Lin The Astrophysical Journal, Volume 847, Issue 2, article id. 85, 15 pp. (2017).

1709.09700:
No time for dead time - Use the Fourier amplitude differences to normalize dead time-affected periodograms M. Bachetti, D. Huppenkothen, submitted to The Astrophysical Journal Letters

1611.10230:
Burst and Outburst Characteristics of Magnetar 4U 0142+61 E. Göğüş, L. Lin, O.J. Roberts, M. Chakraborty, Y. Kaneko, R. Gill, J. Granot, A.J. van der Horst, A.L. Watts, M.B. Baring, C. Kouveliotou, D. Huppenkothen, G. Younes The Astrophysical Journal, Volume 835, Issue 1, article id. 68, 8 pp. (2017)

1608.07133:
Magnetar-like X-Ray Bursts from a Rotation-powered Pulsar, PSR J1119-6127 E. Göğüş, L. Lin, Y. Kaneko, C. Kouveliotou, A.L. Watts, M. Chakraborty, M.A. Alpar, D. Huppenkothen, O.J. Roberts, G. Younes, A.J. van der Horst, The Astrophysical Journal Letters, Volume 829, Issue 2, article id. L25, 7 pp. (2016)

1606.02620:
False periodicities in quasar time-domain surveys S. Vaughan, P. Uttley, A.G. Markowitz, D. Huppenkothen, M.J. Middleton, W.N. Alston, J.D. Scargle, W.M. Farr, Monthly Notices of the Royal Astronomical Society, Volume 461, Issue 3, p.3145-3152

1607.08823:
eXTP: Enhanced X-ray Timing and Polarization mission Zhang, S. N.; Feroci, M.; Santangelo, A.; Dong, Y. W.; Feng, H.; Lu, F. J.; Nandra, K.; Wang, Z. S.; Zhang, S.; Bozzo, E.; Brandt, S.; De Rosa, A.; Gou, L. J.; Hernanz, M.; van der Klis, M.; Li, X. D.; Liu, Y.; Orleanski, P.; Pareschi, G.; Pohl, M.; Poutanen, J.; Qu, J. L.; Schanne, S.; Stella, L.; Uttley, P.; Watts, A.; Xu, R. X.; Yu, W. F.; in 't Zand, J. J. M.; Zane, S.; Alvarez, L.; Amati, L.; Baldini, L.; Bambi, C.; Basso, S.; Bhattacharyya S.;, Bellazzini, R.; Belloni, T.; Bellutti, P.; Bianchi, S.; Brez, A.; Bursa, M.; Burwitz, V.; Budtz-Jørgensen, C.; Caiazzo, I.; Campana, R.; Cao, X.; Casella, P.; Chen, C. Y.; Chen, L.; Chen, T.; Chen, Y.; Chen, Y.; Chen, Y. P.; Civitani, M.; Coti Zelati, F.; Cui, W.; Cui, W. W.; Dai, Z. G.; Del Monte, E.; de Martino, D.; Di Cosimo, S.; Diebold, S.; Dovciak, M.; Donnarumma, I.; Doroshenko, V.; Esposito, P.; Evangelista, Y.; Favre, Y.; Friedrich, P.; Fuschino, F.; Galvez, J. L.; Gao, Z. L.; Ge, M. Y.; Gevin, O.; Goetz, D.; Han, D. W.; Heyl, J.; Horak, J.; Hu, W.; Huang, F.; Huang, Q. S.; Hudec, R.; Huppenkothen, D.; Israel, G. L.; Ingram, A.; Karas, V.; Karelin, D.; Jenke, P. A.; Ji, L.; Korpela, S.; Kunneriath, D.; Labanti, C.; Li, G.; Li, X.; Li, Z. S.; Liang, E. W.; Limousin, O.; Lin, L.; Ling, Z. X.; Liu, H. B.; Liu, H. W.; Liu, Z.; Lu, B.; Lund, N.; Lai, D.; Luo, B.; Luo, T.; Ma, B.; Mahmoodifar, S.; Marisaldi, M.; Martindale, A.; Meidinger, N.; Men, Y.; Michalska, M.; Mignani, R.; Minuti, M.; Motta, S.; Muleri, F.; Neilsen, J.; Orlandini, M.; Pan, A. T.; Patruno, A.; Perinati, E.; Picciotto, A.; Piemonte, C.; Pinchera, M.; Rachevski A.; Rapisarda, M.; Rea, N.; Rossi, E. M. R.; Rubini, A.; Sala, G.; Shu, X. W.; Sgro, C.; Shen, Z. X.; Soffitta, P.; Song, L.; Spandre, G.; Stratta, G.; Strohmayer, T. E.; Sun, L.; Svoboda, J.; Tagliaferri, G.; Tenzer, G.; Hong, T.; Taverna, R.; Torok, G.; Turolla, R.; Vacchi, S.; Wang, J.; Walton, D.; Wang, K.; Wang, J. F.; Wang, R. J.; Wang, Y. F.; Weng, S. S.; Wilms, J.; Winter, B.; Wu, X.; Wu, X. F.; Xiong, S. L.; Xu, Y. P.; Xue, Y. Q.; Yan, Z.; Yang, S.; Yang, X.; Yang, Y. J.; Yuan, F.; Yuan, W. M.; Yuan, Y. F.; Zampa, G.; Zampa, N.; Zdziarski, A.; Zhang, C.; Zhang, C. L.; Zhang, L.; Zhang, X.; Zhang, Z.; Zhang, W. D.; Zheng, S. J.; Zhou, P.; Zhou X. L. Proceedings of the SPIE, Volume 9905, id. 99051Q 16 pp. (2016)

1604.06472:
The Wind Nebula around Magnetar Swift J1834.9-0846 G. Younes, C. Kouveliotou, O. Kargaltsev, R. Gill, J. Granot, A.L. Watts, J. Gelfand, M.G. Baring, A. Harding, G.G. Pavlov, A.J. van der Horst, D. Huppenkothen, E. Göğüş, L. Lin, O.J. Roberts, The Astrophysical Journal, Volume 824, Issue 2, article id. 138, 12 pp. (2016)

1503.04152:
The Five Year Fermi/GBM Magnetar Burst Catalog A.C. Collazzi, C. Kouveliotou, A.J. van der Horst, G.A. Younes, Y. Kaneko, E. Göğüş, L. Lin, J. Granot, M.H. Finger, V.L. Chaplin, D. Huppenkothen, A.L. Watts, A. von Kienlin, M.G. Baring, D. Gruber, P.N. Bhat, M.H. Gibby, N. Gehrels, J. McEnery, M. van der Klis, R.A.M.J. Wijers, The Astrophysical Journal Supplement Series, Volume 218, Issue 1, article id. 11, 30 pp. (2015)

1402.6015:
Time Resolved Spectroscopy of SGR J1550-5418 for the Fermi/GBM Bursts G. Younes, C. Kouveliotou, A.J. van der Horst, M.G. Baring, J. Granot, A.L. Watts, P.N. Bhat, A. Collazzi, C.R. D'Angelo, N. Gehrels, N. Gorgone, E. Göğüş, D. Gruber, S. Grunblatt, D. Huppenkothen, A. von Kienlin, Y. Kaneko, L. Lin, J. McEnery, M. van der Klis, T. van Putten, R.A.M.J. Wijers, The Astrophysical Journal, Volume 785 (2014), arxiv 1402.6015

1212.4144: The Outflow History of Two Herbig-Haro Jets in RCQ 36: HH1042 and HH1043
L.E. Ellerbroek, L. Podio, L. Kaper, H. Sana, D. Huppenkothen, A. de Koter, L. Monaco, Astronomy and Astrophyscs 551 (2013), A5

1206.4915: Detection of Spectral Evolution in Bursts Emitted During the 2008-2009 Active Episode of SGR J1550-5418
A. von Kienlin, D. Gruber, C. Kouveliotou, J. Granot, M.G. Baring, E. Göğüş, D. Huppenkothen, Y. Kaneko, L. Lin, A.L. Watts, N.P. Bhat, S. Guiriec, A.J. van der Horst, E. Bissaldi, J. Greiner, C.A. Meegan, W.S. Paciesas, R.D. Preece, A. Rau, The Astrophysical Journal 755 (2012), L150-L161

1011.0731: Using the X-ray Morphology of Young Supernova Remnants to Constrain Type, Ejecta Distribution and Chemical Mixing
L.A. Lopez, E. Ramirez-Ruiz, D. Huppenkothen, C. Badenes, D.A. Pooley, The Astrophysical Journal 732 (2011), L114-L132

0910.3208: Typing Supernova Remnants Using X-ray Line Emission Morphologies
L.A. Lopez, E. Ramirez-Ruiz, C. Badenes, D. Huppenkothen, T.E. Jeltema, D.A. Pooley, Astrophysical Journal Letters 706 (2009), L106-L109

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CV

You can find my CV here. My thesis is available from the University of Amsterdam here.

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Code

You can find all of my code on GitHub. ` The most noteworthy thing I've written to date is BayesPSD, which contains my method for finding quasi-periodic oscillations in bursty time series, and Magnetron, which is a collaboration with Brendon Brewer and a hierarchical model for decomposing magnetar bursts into simple shapes. Most of BayesPSD is currently being rewritten and to be included in our open-source, general-purpose X-ray timing package called stingray, which is more generally aimed at providing stable, well-tested and -documented implementations of common Fourier analysis and spectral timing methods commonly used in astronomy. Together with Brian McFee, I am also working on an automated tool for participant selection for conferences and workshops called entrofy.

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Not Work

In my spare time, I am most likely to be found playing tuning my harp(a Salvi Daphne 47EX). I play a lot of Irish folk music (a leftover from owning an Irish harp for a long time), and I like modern classical music a lot. When not practicing new pieces, I'll probably be out exploring my surroundings with my camera, with a strong focus on waterfalls and squirrels, depending on which I am more likely to encounter. You'll probably find the photos on this website updated periodically.

Say Hello.

You can send me an e-mail at dhuppenk[at]uw.edu, or find me on Twitter or GitHub.