You have stumbled onto Jay Farihi's homepage

You have stumbled onto Jay Farihi's homepage...

Incriminating information:

I am a Professor in the Astrophysics group at University College London, and a former (2012) Ernest Rutherford Fellow. Prior to UCL, I was a Senior Fellow at the Institute of Astronomy in Cambridge, and held postdoctoral positions at the University of Leicester and Gemini Observatory North. My doctoral research was carried out at the University of California, Los Angeles.

My main research activity is digging up evidence of terrestrial planetary systems at stellar corpses known as white dwarfs. One might not expect to find the surviving planetary systems around dead stars, but the universe is full of surprises. In fact, it is likely we will learn more about extrasolar terrestrial planets using white dwarfs than via any other method. This is because cool white dwarfs have pure hydrogen and helium atmospheres, and those stars with rocky planetary systems can become polluted by small yet detectable amounts of heavy elements, such as metals. We can use this metal pollution to measure the composition of the rocky planetary material, and even identify water.

I use the Hubble and the Spitzer Space Telescopes to analyze the rocky debris around white dwarfs; the current picture is that they externally polluted with heavy elements from tidally destroyed asteroids. The parent bodies descend from large and differentiated objects, and these may be leftover planetary building blocks or fragments of major planets. The compositions measured to date are similar to the material found in the inner Solar System (i.e. like Earth!). Currently, we estimate that at least 20-30% of all white dwarfs harbor terrestrial planetary system remnants. Relevant publications and press releases can be found below.

The early years:

As a graduate student, I worked with Eric Becklin & Ben Zuckerman searching for low mass stellar and substellar companions to nearby white dwarfs. The bulk of my thesis is published in an ApJ Supplement Series paper. If you want all the gory details (they are both plentiful and colorful), you can find my thesis here:

http://whitedwarf.org/theses/farihi.pdf

The central result of my thesis: a spectral type histogram of low mass companions to white dwarfs. The drop off in companion frequency is clearly above the minimum mass for hydrogen burning, which corresponds to an early L dwarf spectral type / temperature at typical white dwarf ages of one to a few Gyr. Our sensitivity is off the chart. As with solar-type main sequence stars, intermediate mass stars (the progenitors of white dwarfs) with brown dwarf companions are rare.

Passions, obsessions, the endless pursuit of knowledge:

The assembly and fate of planetary systems

Origin and evolution of low mass objects

The local cool white dwarf population

Digging in the stellar graveyard

I am fortunate to have several space-based research programs, as well as talented students in our group. Many of our results are posted below, with more on the way...

Opinions backed by evidence:

105) Measuring White Dwarf Variability from Sparsely Sampled Gaia DR3 Multi-Epoch Photometry: astro-ph | ApJ

104) White Dwarf Pollution: One Star or Two?: astro-ph | MNRAS

103) Missing Metals in DQ Stars: a Compelling Clue to their Origin: astro-ph | MNRAS

102) Discovery of Magnetically Guided Metal Accretion onto a Polluted White Dwarf: astro-ph | ApJL | press

101) The Morphology of Asteroidal Dust Around White Dwarf Stars: Optical and Near-infrared Pulsations in G29-38: astro-ph | ApJ

100) A Nearby Polluted White Dwarf with a 6.2 h Spin Period: astro-ph | MNRAS

99) The First White Dwarf Debris Disk Observed by JWST: astro-ph | MNRAS

98) WD 0141-675: A Case Study on How to Follow-up Astrometric Planet Candidates around White Dwarfs: astro-ph | MNRAS

97) Planetesimals at DZ Stars I: Chondritic Compositions and a Massive Accretion Event: astro-ph | MNRAS

96) An HST COS Ultraviolet Spectroscopic Survey of 311 DA White Dwarfs. I. Fundamental Parameters and Comparative Studies: astro-ph | MNRAS

95) Discovery of Dipolar Chromospheres in Two White Dwarfs: astro-ph | MNRAS

94) Measurement of Stellar and Substellar Winds Using White Dwarf Hosts: astro-ph | MNRAS

93) Two Substellar Survivor Candidates; One Found and One Missing: astro-ph | MNRAS

92) Gaia White Dwarfs within 40 pc - III. Spectroscopic Observations of New Candidates in the Southern Hemisphere: astro-ph | MNRAS

91) The Gliese 86 Binary System: A Warm Jupiter Formed in a Disk Truncated at 2 AU: astro-ph | AJ

90) Relentless and Complex Transits from a Planetesimal Debris Disk: astro-ph | MNRAS | press | BBC

89) Collisions in a Gas-Rich White Dwarf Planetary Debris Disc: astro-ph | MNRAS

88) Carbon-Enhanced Stars with Short Orbital and Spin Periods: astro-ph | MNRAS

87) A Test of the Planet-Star Unipolar Inductor for Magnetic White Dwarfs: astro-ph | MNRAS

86) Horizontal Spreading of Planetary Debris Accreted by White Dwarfs: astro-ph | MNRAS

85) White Dwarfs with Planetary Remnants in the Era of Gaia I. Six Emission Line Systems: astro-ph | MNRAS

84) GD 424, a Helium Atmosphere White Dwarf with a Large Amount of Trace Hydrogen in the Process of Digesting a Rocky Planetesimal: astro-ph | MNRAS

83) White Dwarf Pollution by Hydrated Planetary Remnants: Hydrogen and Metals in WD J204713.76–125908.9: astro-ph | MNRAS

82) Gaia White Dwarfs within 40 pc. I. Spectroscopic Observations of New Candidates: astro-ph | MNRAS

81) The Dust Never Settles: Collisional Production of Gas and Dust in Evolved Planetary Systems: astro-ph | MNRAS

80) A Word to the WISE: Confusion Is Unavoidable for WISE-Selected Infrared Excesses: astro-ph | ApJ

79) Interpretation and Diversity of Exoplanetary Material Orbiting White Dwarfs: astro-ph | MNRAS

78) A Chandra Study: Are Dwarf Carbon Stars Spun Up and Rejuvenated by Mass Transfer?: astro-ph | ApJ

77) The Unbiased Frequency of Planetary Signatures around Single and Binary White Dwarfs using Spitzer and Hubble: astro-ph | MNRAS

76) A Planetesimal Orbiting within the Debris Disc around a White Dwarf Star: astro-ph | Science

75) Most White Dwarfs with Detectable Dust Discs Show Infrared Variability: astro-ph | MNRAS

74) Evidence for Bimodal Orbital Separations of White Dwarf - Red Dwarf Binary Stars: astro-ph | MNRAS

73) Multi-Wavelength Observations of the EUV Variable Metal-Rich White Dwarf GD 394: astro-ph | MNRAS

72) Broadening of Ly-alpha by Neutral Helium in DBA White Dwarfs: astro-ph | MNRAS

71) Dust Production and Depletion in Evolved Planetary Systems: astro-ph | MNRAS

70) Fast Spectrophotometry of WD 1145+017: astro-ph | MNRAS

69) Infrared Variability of Two Dusty White Dwarfs: astro-ph | ApJ

68) Dwarf Carbon Stars Are Likely Metal-Poor Binaries and Unlikely Hosts to Carbon Planets: astro-ph | MNRAS

67) Evidence for Halo Kinematics among Cool Carbon-Rich Dwarfs: astro-ph | MNRAS

66) Evidence for Eccentric, Precessing Gaseous Debris in the Circumstellar Absorption toward WD 1145+017: astro-ph | ApJL

65) The First Post-Kepler Brightness Dips of KIC 8462852: astro-ph | ApJL

64) Periodic Optical Variability and Debris Accretion in White Dwarfs: a Test for a Causal Connection: astro-ph | MNRAS

63) Magnetism, X-rays, and Accretion Rates in WD 1145+017 and other Polluted White Dwarf Systems: astro-ph | MNRAS

62) Magnetospherically-Trapped Dust and a Possible Model for the Unusual Transits at WD 1145+017: astro-ph | MNRAS

61) Spectroscopic Evolution of Disintegrating Planetesimals: Minutes to Months Variability in the Circumstellar Gas Associated with WD 1145+017: astro-ph | ApJ

60) Trace Hydrogen in Helium Atmosphere White Dwarfs as a Possible Signature of Water Accretion: astro-ph | MNRAS

59) Infrared Observations of White Dwarfs and the Implications for the Accretion of Dusty Planetary Material: astro-ph | MNRAS

58) A Circumbinary Debris Disk in a Polluted White Dwarf System: astro-ph | Nature Astronomy | press

57) Solar Abundances of Rock Forming Elements, Extreme Oxygen and Hydrogen in a Young Polluted White Dwarf: astro-ph | MNRAS

56) Carbon to Oxygen Ratios in Extrasolar Planetesimals: astro-ph | MNRAS

55) Circumstellar Debris and Pollution at White Dwarf Stars: astro-ph | NewAR | press

54) High-Speed Photometry of the Disintegrating Planetesimals at WD 1145+017: Evidence for Rapid Dynamical Evolution: astro-ph | ApJ

53) Likely Detection of Water-Rich Asteroid Debris in a Metal-Polluted White Dwarf: astro-ph | MNRAS

52) The Frequency and Infrared Brightness of Circumstellar Discs at White Dwarfs: astro-ph | MNRAS

51) Signs of a Faint Disc Population at Polluted White Dwarfs: astro-ph | MNRAS

50) ALMA and Herschel Observations of the Prototype Dusty and Polluted White Dwarf G29-38: astro-ph | MNRAS

49) Heavy Metals in a Light White Dwarf: Abundances of the Metal-Rich, Extremely Low-Mass GALEX J1717+6757: astro-ph | MNRAS

48) The Puzzling Source IGR J17361-4441 in NGC 6388: A Possible Planetary Tidal Disruption Event: astro-ph | MNRAS

47) The Frequency of Planetary Debris at Young White Dwarfs: astro-ph | A&A

46) Stochastic Accretion of Planetesimals onto White Dwarfs. Constraints on the Mass Distribution of Accreted Material from Atmospheric Pollution: astro-ph | MNRAS

44) Evidence of Rocky Planetesimals Orbiting Two Hyades Stars: astro-ph | MNRAS | press | BBC

43) Orbital and Evolutionary Constraints on the Planet Hosting Binary GJ 86 from the Hubble Space Telescope: astro-ph | MNRAS

42) The WIRED Survey III: An Infrared Excess around the Eclipsing Post-Common Envelope Binary SDSS J030308.35+005443.7: astro-ph | ApJ

41) Precision Astrometry of the Exoplanet Host Candidate GD 66: astro-ph | MNRAS

40) The Chemical Diversity of Exoterrestrial Planetary Debris Around White Dwarfs: astro-ph | MNRAS | press

39) Scars of Intense Accretion Episodes at Metal-Rich White Dwarfs: astro-ph | MNRAS

38) Gaseous Material Orbiting the Polluted White Dwarf HE 1349-2305: astro-ph | ApJ

37) The Origin of Circumstellar Features in the Spectra of Hot DA White Dwarfs: astro-ph | MNRAS

36) Constraints on the Lifetimes of Disks Resulting from Tidally Destroyed Rocky Planetary Bodies: astro-ph | ApJ

35) A Trio of Metal-Rich Dust and Gas Disks Found Orbiting Candidate White Dwarfs with K-Band Excess: astro-ph | MNRAS

34) An Extremely Luminous Panchromatic Outburst from the Nucleus of a Distant Galaxy: astro-ph | Science | BBC

33) Evolutionary Constraints on the Planet-Hosting Subgiant epsilon Reticulum from its White Dwarf Companion: astro-ph | MNRAS

32) Accretion of a Terrestrial-Like Minor Planet by a White Dwarf: astro-ph | ApJ

31) The Magnetic and Metallic Degenerate G77-50: astro-ph | MNRAS

30) Possible Signs of Water and Differentiation in a Rocky Exoplanetary Body: astro-ph | ApJL

29) White Dwarf - Red Dwarf Systems Resolved with the Hubble Space Telescope. II. Full Snapshot Survey Results: astro-ph | ApJS

28) A Detailed Model Atmosphere Analysis of Cool White Dwarfs in the Sloan Digital Sky Survey: astro-ph | ApJS

27) Strengthening the Case for Asteroidal Accretion: Evidence for Subtle and Diverse Disks at White Dwarfs: astro-ph | ApJ

26) Does GD 356 Have a Terrestrial Planetary Companion?: astro-ph | MNRAS

25) Rocky Planetesimals as the Origin of Metals in DZ Stars: astro-ph | MNRAS | press

24) IRTF Observations of White Dwarfs with Possible Near-Infrared Excess: astro-ph | MNRAS

23) Deep Imaging Survey of Young, Nearby Austral Stars. VLT / NACO Near-infrared Lyot-Coronographic Observations: astro-ph | A&A

22) A Glimpse of the End of the Dark Ages: The Gamma-Ray Burst of 23 April 2009 at Redshift 8.3: astro-ph | Nature | BBC

21) X-Ray and Infrared Observations of Two Externally-Polluted White Dwarfs: astro-ph | ApJ | press

20) PHL 5038: A Spatially Resolved White Dwarf - Brown Dwarf Binary: astro-ph | A&A

19) Infrared Signatures of Disrupted Minor Planets at White Dwarfs: astro-ph | ApJ | press | BBC

18) Six White Dwarfs with Circumstellar Silicates: astro-ph | AJ | press

17) Spitzer IRAC Observations of White Dwarfs. II. Massive Planetary and Cold Brown Dwarf Companions to Young and Old Degenerates: astro-ph | ApJ

16) Near-Infrared Constraints on the Presence of Warm Dust at Metal-Rich Helium Atmosphere White Dwarfs: astro-ph | AJ

15) Spitzer IRAC Observations of White Dwarfs. I. Warm Dust at Metal-Rich Degenerates: astro-ph | ApJ

14) A Near-Infrared Spectroscopic Study of the Accreting Magnetic White Dwarf SDSS J121209.31+013627.7 and Its Substellar Companion: astro-ph | ApJ | press

13) Externally Polluted White Dwarfs with Dust Disks: astro-ph | ApJ

12) Infrared Emission from the Dusty Disk Orbiting GD 362, an Externally Polluted White Dwarf: astro-ph | AJ | press

11) The Nature of the Close Magnetic White Dwarf - Probable Brown Dwarf Binary SDSSJ121209.31+013627.7: astro-ph | MNRAS

10) HST NICMOS Imaging of the Planetary-mass Companion to the Young Brown Dwarf 2MASSW J1207334-393254: astro-ph | ApJ | press

9) White Dwarf - Red Dwarf Systems Resolved with the Hubble Space Telescope. I. First Results: astro-ph | ApJ

8) Low-Luminosity Companions to White Dwarfs (thesis work): astro-ph | ApJS

7) Mid-Infrared Observations of the White Dwarf - Brown Dwarf Binary GD 1400: astro-ph | AJ

6) A Dusty Disk around GD 362, a White Dwarf with a Uniquely High Photospheric Metal Abundance: astro-ph | ApJL | press

5) SSSPM J1549-3544 Is Not a White Dwarf: astro-ph | ApJL

4) Cool versus Ultracool White Dwarfs: astro-ph | AJ

3) A Possible Brown Dwarf Companion to the White Dwarf GD 1400: astro-ph | AJ

2) Discovery of an Ultracool White Dwarf Companion: astro-ph | ApJ

1) Mid-Infrared Observations of van Maanen 2: No Substellar Companion: astro-ph | ApJL

Exchange of ideas:

Jay Farihi

Professor

Physics and Astronomy

University College London

London WC1E 6BT

United Kingdom

Phone: +44 203 549 5812

j dot farihi at ucl dot ac dot uk