Andy Howell

Staff Scientist / UCSB Adjunct Faculty


  • The Rapid Reddening and Featureless Optical Spectra of the Optical Counterpart of GW170817, AT 2017gfo, during the First Four Days
    The Astrophysical Journal Letters, Volume 848, Number 2
  • Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger
    Nature, 2017, 1476-4687
  • Optical Follow-up of Gravitational-wave Events with Las Cumbres Observatory
    The Astrophysical Journal, 2017 848 2
  • A gravitational-wave standard siren measurement of the Hubble constant
    eprint arXiv:1710.05835
  • Multi-messenger Observations of a Binary Neutron Star Merger
    The Astrophysical Journal, 2017 848 2
  • Hydrogen-rich supernovae beyond the neutrino-driven core-collapse paradigm
    eprint arXiv:1709.10475
  • SN 2016coi/ASASSN-16fp: An example of residual helium in a type Ic supernova?
    eprint arXiv:1709.03593
  • Nebular-Phase Spectra of Nearby Type Ia Supernovae
    Monthly Notices of the Royal Astronomical Society, 2017 472 3
  • Early Observations of the Type Ia Supernova iPTF 16abc: Evidence for Strong Ejecta Mixing or Interaction with Diffuse Material
    eprint arXiv:1708.07124
  • Light curves of hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory
    eprint arXiv:1708.01623
  • LSQ14efd: observations of the cooling of a shock break-out event in a type Ic Supernova
    Monthly Notices of the Royal Astronomical Society, 2017 471 2
  • Optical and IR observations of SN 2013L, a Type IIn Supernova surrounded by asymmetric CSM
    Monthly Notices of the Royal Astronomical Society, 2017 471 4
  • An individual star at redshift 1.5 extremely magnified by a galaxy-cluster lens
    eprint arXiv:1706.10279
  • Early Blue Excess from the Type Ia Supernova 2017cbv and Implications for its Progenitor
    The Astrophysical Journal, 2017 845 2
  • The Dependence of Type Ia Supernova Luminosities on Their Local Environment
    eprint arXiv:1706.07697
  • Clues to the Nature of SN 2009ip II: The Continuing Photometric and Spectroscopic Evolution to 1000 Days
    Monthly Notices of the Royal Astronomical Society, 2017 469 2
  • Hydrogen-poor Superluminous Supernovae with Late-time Hα Emission: Three Events From the Intermediate Palomar Transient Factory
    The Astrophysical Journal, 2017 848 1
  • Multiwavelength follow-up of a rare IceCube neutrino multiplet
    eprint arXiv:1702.06131
  • Growing evidence that SNe Iax are not a one-parameter family: the case of PS1-12bwh
    Astronomy & Astrophysics, Volume 601, id.A62, 12 pp.
  • Confined Dense Circumstellar Material Surrounding a Regular Type II Supernova: The Unique Flash-Spectroscopy Event - SN 2013fs
    Nature Physics, 2017 13 5
  • A Type II Supernova Hubble diagram from the CSP-I, SDSS-II, and SNLS surveys
    eprint arXiv:1612.05636
  • Two New Calcium-Rich Gap Transients in Group and Cluster Environments
    The Astrophysical Journal, 2017 836 1
  • Discovery and Follow-up Observations of the Young Type Ia Supernova 2016coj
    The Astrophysical Journal, 2017 841 1
  • Constraints on the Progenitor of SN 2016gkg From Its Shock-Cooling Light Curve
    The Astrophysical Journal, 2017 837 1
  • The progenitor and early evolution of the Type IIb SN 2016gkg
    eprint arXiv:1611.00419
  • On the early-time excess emission in hydrogen-poor superluminous supernovae
    The Astrophysical Journal, 2017 835 1
  • Early observations of the nearby type Ia supernova SN 2015F
    Monthly Notices of the Royal Astronomical Society, 2017 464 4
  • The Superluminous Transient ASASSN-15lh as a Tidal Disruption Event from a Kerr Black Hole
    Nature Astronomy 1, Article number: 0002 (2016)
  • Optical and Ultraviolet Observations of the Very Young Type IIP SN 2014cx in NGC 337
    The Astrophysical Journal, Volume 832, Number 2
  • Superluminous supernova 2015bn in the nebular phase: evidence for the engine-powered explosion of a stripped massive star
    eprint arXiv:1608.02995
  • Type Ibn Supernovae Show Photometric Homogeneity and Evidence for Two Spectral Subclasses
    The Astrophysical Journal, 2017 836 2
  • 450 Days of Type II SN 2013ej in Optical and Near-Infrared
    eprint arXiv:1605.06117
  • The multi-faceted Type II-L supernova 2014G from pre-maximum to nebular phase
    eprint arXiv:1605.06116
  • The volumetric rate of superluminous supernovae at z ˜ 1
    Monthly Notices of the Royal Astronomical Society, 2017 464 3
  • On the nature of Hydrogen-rich Superluminous Supernovae
    eprint arXiv:1604.01226
  • Interacting supernovae and supernova impostors. LSQ13zm: an outburst heralds the death of a massive star
    eprint arXiv:1604.00013
  • The Diversity of Type II Supernova vs. The Similarity in Their Progenitors
    eprint arXiv:1603.08953
  • Optical and near infrared observations of SN 2014ck: an outlier among the Type Iax supernovae
    eprint arXiv:1603.07084
  • SN 2015bn: a detailed multi-wavelength view of a nearby superluminous supernova
    eprint arXiv:1603.04748
  • Comparative analysis of SN 2012dn optical spectra: days -14 to +114
    Monthly Notices of the Royal Astronomical Society, Volume 457, Issue 4, p.3702-3723
  • DES14X3taz: A Type I Superluminous Supernova Showing a Luminous, Rapidly Cooling Initial Pre-peak Bump
    The Astrophysical Journal Letters, Volume 818, Issue 1, article id. L8, 7 pp. (2016).
  • Flash Spectroscopy: Emission Lines from the Ionized Circumstellar Material around <10-Day-Old Type II Supernovae
    eprint arXiv:1512.00846
  • Type II supernova energetics and comparison of light curves to shock-cooling models
    eprint arXiv:1512.00733
  • Rapidly Rising Transients in the Supernova - Superluminous Supernova Gap
    eprint arXiv:1511.00704
  • On type IIn/Ia-CSM supernovae as exemplified by SN 2012ca
    eprint arXiv:1510.01109
  • Supernova 2013fc in a circumnuclear ring of a luminous infrared galaxy: the big brother of SN 1998S
    eprint arXiv:1509.05389
  • SN 2011fu: a type IIb supernova with a luminous double-peaked light curve
    Monthly Notices of the Royal Astronomical Society, Volume 454, Issue 1, p.95-114
  • Spectral models for early time SN 2011fe observations
    Monthly Notices of the Royal Astronomical Society, Volume 454, Issue 3, p.2549-2556
  • SN~2012cg: Evidence for Interaction Between a Normal Type Ia Supernova and a Non-Degenerate Binary Companion
    eprint arXiv:1507.07261
  • Measuring nickel masses in Type Ia supernovae using cobalt emission in nebular phase spectra
    eprint arXiv:1507.02501
  • Science with KRAKENS
    eprint arXiv:1506.03458
  • The Detection of a Type IIn Supernova in Optical Follow-up Observations of IceCube Neutrino Events
    The Astrophysical Journal, Volume 811, Issue 1, article id. 52, 17 pp. (2015).
  • A strong ultraviolet pulse from a newborn type Ia supernova
    Nature, Volume 521, Issue 7552, pp. 328-331 (2015).
  • The rise-time of Type II supernovae
    Monthly Notices of the Royal Astronomical Society, Volume 451, Issue 2, p.2212-2229
  • Diversity in extinction laws of Type Ia supernovae measured between 0.2 and 2 µm
    eprint arXiv:1504.02101
  • SN 2013ab: a normal Type IIP supernova in NGC 5669
  • Massive stars exploding in a He-rich circumstellar medium - VI. Observations of two distant Type Ibn supernova candidates discovered by La Silla-QUEST
    Monthly Notices of the Royal Astronomical Society, Volume 449, Issue 2, p.1954-1966
  • Supernova 2013by: A Type IIL Supernova with a IIP-like light curve drop
  • Time-Varying Potassium in High-Resolution Spectra of the Type Ia Supernova 2014j
  • The Rising Light Curves of Type Ia Supernovae
  • OGLE-2013-SN-079: a lonely supernova consistent with a helium shell detonation
  • Type Ia Supernova Spectral Features in the Context of Their Host Galaxy Properties
  • Exploring the spectral diversity of low-redshift Type Ia supernovae using the Palomar Transient Factory
  • SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant
  • Slow-speed Supernovae from the Palomar Transient Factory: Two Channels
  • Early Observations and Analysis of the Type Ia SN 2014J in M82
  • A Continuum of H- to He-Rich Tidal Disruption Candidates With a Preference for E+A Galaxies
  • Super-luminous supernovae from PESSTO
  • The Type IIP Supernova 2012aw in M95: hydrodynamical modelling of the photospheric phase from accurate spectrophotometric monitoring
  • The rise and fall of the Type Ib supernova iPTF13bvn - Not a massive Wolf-Rayet star
  • Clues To The Nature of SN 2009ip from Photometric and Spectroscopic Evolution to Late Times
  • The Rise of SN 2014J in the Nearby Galaxy M82
  • Low luminosity Type II supernovae - II. Pointing towards moderate mass precursors
  • The host galaxies of Type Ia supernovae discovered by the Palomar Transient Factory
  • The Very Young Type Ia Supernova 2013dy: Discovery, and Strong Carbon Absorption in Early-time Spectra
  • Slowly fading super-luminous supernovae that are not pair-instability explosions
  • The superluminous supernova PS1-11ap: bridging the gap between low and high redshift
  • The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617
  • Two Superluminous Supernovae from the Early Universe Discovered by the Supernova Legacy Survey
  • The first month of evolution of the slow-rising Type IIP SN 2013ej in M74$^*$
  • A statistical analysis of circumstellar material in Type Ia supernovae
  • Discovery, Progenitor & Early Evolution of a Stripped Envelope Supernova iPTF13bvn
  • Dark energy with gravitational lens time delays
  • Las Cumbres Observatory Global Telescope Network
  • Hubble Space Telescope spectra of the Type Ia supernova SN 2011fe: a tail of low-density, high-velocity material with Z \lt Z$_&sun;$
  • Optical and near-infrared observations of SN 2011dh - The first 100 days
  • Super Luminous Ic Supernovae: catching a magnetar by the tail
  • Type Ia Supernovae Strongly Interacting with Their Circumstellar Medium
  • Late-time Spectral Observations of the Strongly Interacting Type Ia Supernova PTF11kx
  • An outburst from a massive star 40days before a supernova explosion
  • The UV/optical spectra of the Type Ia supernova SN 2010jn: a bright supernova with outer layers rich in iron-group elements
  • PTF 11kx: A Type Ia Supernova with a Symbiotic Nova Progenitor
  • Hubble Space Telescope studies of low-redshift Type Ia supernovae: evolution with redshift and ultraviolet spectral trends
  • Analysis of the Early-time Optical Spectra of SN 2011fe in M101
  • An Efficient Approach to Obtaining Large Numbers of Distant Supernova Host Galaxy Redshifts
  • Near-infrared observations of Type Ia supernovae: the best known standard candle for cosmology
  • Light echoes reveal an unexpectedly cool $\eta$Carinae during its nineteenth-century Great Eruption
  • A ground-based measurement of the relativistic beaming effect in a detached double WD binary
  • The Global Supernova Project
    American Astronomical Society Meeting Abstracts, 2017 230
  • The Supernova Key Project
    American Astronomical Society Meeting Abstracts, 2017 229
  • On Type IIn/Ia-CSM supernovae as exemplified by SN 2012ca*
    Monthly Notices of the Royal Astronomical Society, Volume 459, Issue 3, p.2721-2740
  • Science operations for LCOGT: a global telescope network
  • The LCOGT Supernova Key Project
    NOAO Proposal ID #2014B-0286
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