Sciences and Exploration Directorate

Koji Mukai


Koji Mukai's Contact Card & Information.
Phone: 301.286.9447
Org Code: 662
Mail Code 662
Greenbelt, MD 20771

Brief Bio

I grew up in Japan, up through my undergraduate degree from University of Tokyo. I them moved to the UK andreceived my doctorate from University of Oxford with Prof. Phil Charles. After post-doctoral work in the UK (Mullard Space Science Laboratory) and in the US (University of California, Berkeley), I have been working at NASA's Goddard Space Flight Center since 1992.

Research Interests

Accreting White Dwarf Binaries

Astrophysics: X-ray Binaries & CVs

Multi-wavelength observations of cataclysmic variables and symbiotic stars, in their usual accretion-powered phase or during nova eruptions (powered by thermonuclear runaway), from radio, infrared, optical, ultraviolet, soft and hard X-rays, and MeV gamma-rays.

Current Projects


X-ray Astrophysics

Preparation for the Guest Observer program for the XRISM mission, led by ISAS/JAXA.


Member of the NuSTAR Guest Observer Facility.


Senior Research Scientist

University of Maryland, Baltimore County - NASA's Goddard Space Flight Center

March 2007 - Present

Research Scientist

Universities Space Research Association - NASA's Goddard Space Flight Center

January 1992 - March 2007

Associate Astrophysicist

University of California, Berkeley - Space Sciences Laboratory

November 1989 - December 1991

Post-Doctoral Research Assistant

University College, London - Mullard Space Science Laboratory

November 1986 - November 1989


1983 - Rigakushi (B.Sc.), University of Tokyo.

1986 - D.Phil. University of Oxford (Thesis:"Spectroscopic Studies of AM Her Type Systems")

Professional Societies

Royal Astronomical Society

1983 - Present

American Astronomical Society

1989 - Present

Professional Service

Served as independent referee for numerous papers submitted to profession journals (Science, The Astrophysical Journal, Astronomy & Astrophysics, the Monthly Notices of the Royal Astronomical Society, the Publications of the Astronomical Society of the Pacific, the Publications of the Astronomical Society of Japan, the Astronomical Journal, Astrophysics and Space Science, New Astronomy, Advances in Space Research, and Astronomische Nachrichten).

Participated as a lecturer/tutor in the COSPAR Capcity Building Workshop, “X-ray Astrophysics: an Advanced School for Latin American Astronomers: Data analysis of the XMM-Newton, Chandra, and Suzaku X-ray Missions,” San Juan, Argentina, 2011 July 25-August 5.

Has served on the scientific organizing committees of academic conferences (“Annapolis Workshop on Magnetic Cataclysmic Variables” in 1998, “Wild Stars in the Old West II” in 2009, “Accretion Processes in X-rays: from White Dwarfs to Quasars” in 2010, “Physics of Accreting Compact Binaries” in 2010, and "Chandra Science for the Next Decade" in 2016)

Served on numerous observing-time allocation and funding review panels for the NASA ROSAT, Rossi X-ray Timing Explorer, Chandra X-ray Observatory, K2 satellites and the Astrophysics Data Program, four panels for ESA (XMM-Newton) and four panels for the National Science Foundation.

Selected Publications


2020. "XMM-Newton observations of eleven intermediate polars and possible candidates." Astronomy & Astrophysics 639 A17 [10.1051/0004-6361/202038038] [Journal Article/Letter]

2020. "Optical spectroscopy and X-ray observations of the D-type symbiotic star EF Aql." Monthly Notices of the Royal Astronomical Society 495 (1): 1461-1467 [10.1093/mnras/staa1310] [Journal Article/Letter]

2019. "T CrB: Radio Observations during the 2016–2017 “Super-active” State." The Astrophysical Journal 884 (1): 8 [10.3847/1538-4357/ab3c62] [Journal Article/Letter]

2019. "Fast-cadence TESS Photometry and Doppler Tomography of the Asynchronous Polar CD Ind: A Revised Accretion Geometry from Newly Proposed Spin and Orbital Periods." The Astrophysical Journal 881 (2): 141 [10.3847/1538-4357/ab2a17] [Journal Article/Letter]

2019. "Developing the Physical Understanding of Intermediate Polars: An X-Ray Study of TV Col and V2731 Oph." The Astrophysical Journal 880 (2): 128 [10.3847/1538-4357/ab2b41] [Journal Article/Letter]

2019. "Dissecting a Disk-instability Outburst in a Symbiotic Star: NuSTAR and Swift Observations of T Coronae Borealis during the Rise to the “Superactive” State." The Astrophysical Journal 880 (2): 94 [10.3847/1538-4357/ab2884] [Journal Article/Letter]

2019. "NuSTAR Detection of X-Rays Concurrent with Gamma-Rays in the Nova V5855 Sgr." The Astrophysical Journal 872 (1): 86 [10.3847/1538-4357/aafb6d] [Journal Article/Letter]

2018. "The true nature of Swift J0746.3-1608: a possible Intermediate Polar showing accretion state changes." Monthly Notices of the Royal Astronomical Society 484 (1): 101-106 [10.1093/mnras/sty3499] [Journal Article/Letter]

2018. "Unconventional origin of supersoft X-ray emission from a white dwarf binary." Nature Astronomy 3 (2): 173-177 [10.1038/s41550-018-0639-1] [Journal Article/Letter]

2018. "Dramatic change in the boundary layer in the symbiotic recurrent nova T Coronae Borealis." Astronomy & Astrophysics 619 A61 [10.1051/0004-6361/201833747] [Journal Article/Letter]

2018. "V902 Monocerotis: A likely disc-accreting intermediate polar." Astronomy & Astrophysics 617 A52 [10.1051/0004-6361/201833472] [Journal Article/Letter]

2018. "SU Lyn: Diagnosing the Boundary Layer with UV and Hard X-Ray Data." The Astrophysical Journal 864 (1): 46 [10.3847/1538-4357/aad2d5] [Journal Article/Letter]

2018. "X-ray, UV, and optical observations of the accretion disk and boundary layer in the symbiotic star RT Crucis." Astronomy & Astrophysics 616 A53 [10.1051/0004-6361/201832592] [Journal Article/Letter]

2018. "Measuring the masses of intermediate polars with NuSTAR: V709 Cas, NY Lup, and V1223 Sgr." Monthly Notices of the Royal Astronomical Society 476 (1): 554-561 [10.1093/mnras/sty246] [Journal Article/Letter]

2018. "Constraining the Accretion Geometry of the Intermediate Polar EX Hya Using NuSTAR , Swift , and Chandra Observations." The Astrophysical Journal 852 (1): L8 [10.3847/2041-8213/aaa28f] [Journal Article/Letter]

2017. "Broad-band characteristics of seven new hard X-ray selected cataclysmic variables." Monthly Notices of the Royal Astronomical Society 470 (4): 4815-4837 [10.1093/mnras/stx1494] [Journal Article/Letter]

2017. "X-Ray Emissions from Accreting White Dwarfs: A Review." Publications of the Astronomical Society of the Pacific 129 (976): 062001 [10.1088/1538-3873/aa6736] [Journal Article/Letter]

2017. "Multimission observations of the old nova GK Per during the 2015 outburst." Monthly Notices of the Royal Astronomical Society 469 (1): 476-491 [10.1093/mnras/stx851] [Journal Article/Letter]

2016. "Shock-powered radio emission from V5589 Sagittarii (Nova Sgr 2012 #1)." Monthly Notices of the Royal Astronomical Society 460 (3): 2687-2697 [10.1093/mnras/stw1161] [Journal Article/Letter]

2016. "SU Lyncis, a hard X-ray bright M giant: clues point to a large hidden population of symbiotic stars." Monthly Notices of the Royal Astronomical Society: Letters 461 (1): L1-L5 [10.1093/mnrasl/slw087] [Journal Article/Letter]

2015. "Swiftdetection of the super-swift switch-on of the super-soft phase in nova V745 Sco (2014)." Monthly Notices of the Royal Astronomical Society 454 (3): 3108-3120 [10.1093/mnras/stv2144] [Journal Article/Letter]


2015. "THE DISTANCE TO NOVA V959 MON FROM VLA IMAGING." The Astrophysical Journal 805 (2): 136 [10.1088/0004-637x/805/2/136] [Journal Article/Letter]

2015. "Periodic eclipse variations in asynchronous polar V1432 Aql: evidence of a shifting threading region." Monthly Notices of the Royal Astronomical Society 449 (3): 3107-3120 [10.1093/mnras/stv462] [Journal Article/Letter]

2014. "Binary orbits as the driver of γ-ray emission and mass ejection in classical novae." Nature 514 (7522): 339-342 [10.1038/nature13773] [Journal Article/Letter]

2014. "Constraints on the space density of intermediate polars from the Swift-BAT survey." Monthly Notices of the Royal Astronomical Society 442 (3): 2580-2585 [10.1093/mnras/stu990] [Journal Article/Letter]

2014. "THE 2011 OUTBURST OF RECURRENT NOVA T Pyx: X-RAY OBSERVATIONS EXPOSE THE WHITE DWARF MASS AND EJECTION DYNAMICS." The Astrophysical Journal 788 (2): 130 [10.1088/0004-637x/788/2/130] [Journal Article/Letter]

2014. "THE 2011 OUTBURST OF RECURRENT NOVA T PYX: RADIO OBSERVATIONS REVEAL THE EJECTA MASS AND HINT AT COMPLEX MASS LOSS." The Astrophysical Journal 785 (1): 78 [10.1088/0004-637x/785/1/78] [Journal Article/Letter]

2013. "Symbiotic stars in X-rays." Astronomy & Astrophysics 559 A6 [10.1051/0004-6361/201220792] [Journal Article/Letter]

2012. "THE RADIO LIGHT CURVE OF THE GAMMA-RAY NOVA IN V407 CYG: THERMAL EMISSION FROM THE IONIZED SYMBIOTIC ENVELOPE, DEVOURED FROM WITHIN BY THE NOVA BLAST." The Astrophysical Journal 761 (2): 173 [10.1088/0004-637x/761/2/173] [Journal Article/Letter]

2012. "Characterization of new hard X-ray cataclysmic variables." Astronomy & Astrophysics 542 A22 [10.1051/0004-6361/201219233] [Journal Article/Letter]

2012. "X-RAY EMISSION FROM AN ASYMMETRIC BLAST WAVE AND A MASSIVE WHITE DWARF IN THE GAMMA-RAY EMITTING NOVA V407 Cyg." The Astrophysical Journal 748 (1): 43 [10.1088/0004-637x/748/1/43] [Journal Article/Letter]

2011. "The Fall and the Rise of X-Rays from Dwarf Novae in Outburst: RXTE Observations of VW Hydri and WW Ceti." Publications of the Astronomical Society of the Pacific 123 (907): 1054-1061 [10.1086/661949] [Journal Article/Letter]

2010. "Polarized QPOs from the INTEGRAL polar IGRJ14536-5522 (=Swift J14534-5524)." Monthly Notices of the Royal Astronomical Society 402 1161 [Full Text] [10.1111/j.1365-2966.2009.15944.x] [Journal Article/Letter]

2010. "The intriguing nature of the high-energy gamma ray source XSS J12270-4859." Astronomy and Astrophysics 515 25 [Full Text] [10.1051/0004-6361/200913802] [Journal Article/Letter]

2010. "Deriving an X-ray luminosity function of dwarf novae based on parallax measurements." Monthly Notices of the Royal Astronomical Society 408 2298 [Full Text] [10.1111/j.1365-2966.2010.17276.x] [Journal Article/Letter]

2009. "RXTE confirmation of the intermediate polar status of IGR J15094-6649." Astronomy and Astrophysics 498 L17 [Full Text] [10.1051/0004-6361/200911725] [Journal Article/Letter]

2009. "Broad-band properties of the hard X-ray cataclysmic variables IGR J00234+6141 and 1RXS J2133441+510725." Astronomy and Astrophysics 501 1047 [Full Text] [10.1051/0004-6361/200911816] [Journal Article/Letter]

2009. "Swift observations of GW Lib: a unique insight into a rare outburst." Monthly Notices of the Royal Astronomical Society 399 1576 [Full Text] [10.1111/j.1365-2966.2009.15378.x] [Journal Article/Letter]

2009. "Suzaku Observations of the Dwarf Nova V893 Scorpii: The Discovery of a Partial X-ray Eclipse." The Astrophysical Journal 707 652 [Full Text] [10.1088/0004-637X/707/1/652] [Journal Article/Letter]

2009. "Suzaku Observations of SS Cygni in Quiescence and Outburst." Publications of the Astronomical Society of Japan, Vol61, NoSP1, ppS77--S91 61 77 [Full Text] [Journal Article/Letter]

2009. "Swift Observations of Hard X-ray Emitting White Dwarfs in Symbiotic Stars." The Astrophysical Journal 701 1992 [Full Text] [10.1088/0004-637X/701/2/1992] [Journal Article/Letter]

2008. "A Comparison of the Variability of the Symbiotic X-Ray Binaries GX 1+4, 4U 1954+31, and 4U 1700+24 from Swift BAT and RXTE ASM Observations." The Astrophysical Journal 675 1424 [Full Text] [10.1086/526337] [Journal Article/Letter]

2008. "Two new intermediate polars with a soft X-ray component." Astronomy and Astrophysics 489 1243 [Full Text] [10.1051/0004-6361:200810402] [Journal Article/Letter]

2008. "RXTE determination of the intermediate polar status of XSS J00564+4548, IGR J17195-4100, and XSS J12270-4859." Astronomy and Astrophysics 487 271 [Full Text] [10.1051/0004-6361:200809942] [Journal Article/Letter]

2008. "The Intermediate Polar EI UMa: A Prepolar Cataclysmic Variable." The Astrophysical Journal 678 376 [Full Text] [10.1086/587043] [Journal Article/Letter]

2008. "Novae as a Class of Transient X-Ray Sources." The Astrophysical Journal 677 1248 [Full Text] [10.1086/529362] [Journal Article/Letter]

2008. "1RXS J1730215-055933: a cataclysmic variable with a fast-spinning magnetic white dwarf." Astronomy and Astrophysics 481 149 [Full Text] [10.1051/0004-6361:20078368] [Journal Article/Letter]

2007. "An Apparent Hard X-Ray Decline of CH Cygni." Publications of the Astronomical Society of Japan, Vol59, NoSP1, pp177-183 59 177 [Full Text] [Journal Article/Letter]

2007. "RXTE confirmation of the intermediate polar status of Swift J07325-1331." Astronomy and Astrophysics 475 L29 [Full Text] [10.1051/0004-6361:20078700] [Journal Article/Letter]

2007. "XMM-Newton Observations of the Cataclysmic Variable GW Librae." The Astronomical Journal 134 1503 [Full Text] [10.1086/521343] [Journal Article/Letter]

2007. "A precessing accretion disc in the intermediate polar XY Arietis?." Astronomy and Astrophysics 472 225 [Full Text] [10.1051/0004-6361:20077761] [Journal Article/Letter]

2006. "An X-ray-emitting blast wave from the recurrent nova RS Ophiuchi." Nature 442 276 [Full Text] [10.1038/nature04893] [Journal Article/Letter]

2006. "The X-ray properties of the magnetic cataclysmic variable UU Columbae." Astronomy and Astrophysics 454 287 [Full Text] [10.1051/0004-6361:20065078] [Journal Article/Letter]

2005. "X-ray confirmation of the intermediate polar HT Cam." Astronomy and Astrophysics 437 935 [Full Text] [10.1051/0004-6361:20052761] [Journal Article/Letter]

2005. "The X-Ray Properties of M101 ULX-1 = CXOKM101 J14033274+542102." The Astrophysical Journal 634 1085 [Full Text] [10.1086/497110] [Journal Article/Letter]

2005. "X-ray orbital modulations in intermediate polars." Astronomy and Astrophysics 439 213 [Full Text] [10.1051/0004-6361:20052887] [Journal Article/Letter]

2005. "X-Ray Observations of the Bright Old Nova V603 Aquilae." The Astrophysical Journal 622 602 [Full Text] [10.1086/427915] [Journal Article/Letter]

2004. "On the iron Kα complex in magnetic cataclysmic variables." Monthly Notices of the Royal Astronomical Society 352 1037 [Full Text] [10.1111/j.1365-2966.2004.07995.x] [Journal Article/Letter]

2004. "An XMM-Newton observation of the nova-like variable UX UMa: spatially and spectrally resolved two-component X-ray emission." Monthly Notices of the Royal Astronomical Society 348 L49 [Full Text] [10.1111/j.1365-2966.2004.07574.x] [Journal Article/Letter]

2004. "BeppoSAX observations of soft X-ray intermediate polars." Astronomy and Astrophysics, v415, p1009-1019 (2004) 415 1009 [Full Text] [10.1051/0004-6361:20034160] [Journal Article/Letter]

2003. "X-ray observations of 4 Draconis: symbiotic binary or cataclysmic triple?." Monthly Notices of the Royal Astronomical Society 346 855 [Full Text] [10.1111/j.1365-2966.2003.07149.x] [Journal Article/Letter]

2003. "X-Ray Variability of the Magnetic Cataclysmic Variable V1432 Aquilae and the Seyfert Galaxy NGC 6814." The Astrophysical Journal 597 479 [Full Text] [10.1086/378318] [Journal Article/Letter]

2003. "The Origin of Soft X-Rays in DQ Herculis." The Astrophysical Journal 594 428 [Full Text] [10.1086/376752] [Journal Article/Letter]

2003. "Two Types of X-Ray Spectra in Cataclysmic Variables." The Astrophysical Journal 586 L77 [Full Text] [10.1086/374583] [Journal Article/Letter]

2002. "The spin pulse of the intermediate polar V1062 Tauri." Astronomy and Astrophysics, v389, p904-907 (2002) 389 904 [Full Text] [10.1051/0004-6361:20020634] [Journal Article/Letter]

2002. "The X-Ray Spectra of VY Sculptoris Stars Are Not Blackbodies." The Astrophysical Journal 566 L33 [Full Text] [10.1086/339454] [Journal Article/Letter]

2002. "X-Ray/Optical Studies of Two Outbursts of the Intermediate Polar YY (DO) Draconis." The Astronomical Journal 123 413 [Full Text] [10.1086/324733] [Journal Article/Letter]

2002. "The Orbit and Position of the X-Ray Pulsar XTE J1855-026: an Eclipsing Supergiant System." The Astrophysical Journal 577 923 [Full Text] [10.1086/342244] [Journal Article/Letter]

2001. "The X-ray emission of the intermediate polar V 709 Cas." Astronomy and Astrophysics, v377, p499-511 (2001) 377 499 [Full Text] [10.1051/0004-6361:20011059] [Journal Article/Letter]

2001. "The Early X-Ray Emission from V382 Velorum (Nova Velorum 1999): An Internal Shock Model." The Astrophysical Journal 551 1024 [Full Text] [10.1086/320220] [Journal Article/Letter]

2000. "Outbursts of EX Hydrae: mass-transfer events or disc instabilities?." Monthly Notices of the Royal Astronomical Society 313 703 [Full Text] [10.1046/j.1365-8711.2000.03301.x] [Journal Article/Letter]

1992. "Ginga observations of the dipping low mass X-ray binaries XB1916-053 and EXO0748-676." ApJ 400 330. [Journal Article/Letter]