John F. Beacom

The Ohio State University, Columbus, Ohio, United States

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Publications (172)567.04 Total impact

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    Shirley Weishi Li, John F. Beacom
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    ABSTRACT: Crucial questions about solar and supernova neutrinos remain unanswered. Super-Kamiokande has the exposure needed for progress, but detector backgrounds are a limiting factor. A leading component is the beta decays of isotopes produced by cosmic-ray muons and their secondaries, which initiate nuclear spallation reactions. Cuts of events after and surrounding muon tracks reduce this spallation decay background by $\simeq 90\%$ (at a cost of $\simeq 20\%$ deadtime), but its rate at 6 -- 18 MeV is still dominant. A better way to cut this background was suggested in a Super-Kamiokande paper [Bays {\it et al.}, Phys.~Rev.~D {\bf 85}, 052007 (2012)] on a search for the diffuse supernova neutrino background. They found that spallation decays above 16 MeV were preceded near the same location by a peak in the apparent Cherenkov light profile from the muon; a more aggressive cut was applied to a limited section of the muon track, leading to decreased background without increased deadtime. We put their empirical discovery on a firm theoretical foundation. We show that almost all spallation decay isotopes are produced by muon-induced showers, and that these showers are rare enough and energetic enough to be identifiable. This is the first such demonstration for any detector. We detail how the physics of showers explains the peak in the muon Cherenkov light profile and other Super-K observations. Our results provide a physical basis for practical improvements in background rejection that will benefit multiple studies. For solar neutrinos in particular, it should be possible to dramatically reduce backgrounds at energies as low as 6 MeV.
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    ABSTRACT: We examine the prospects for detecting supernova $\nu_e$ in JUNO, RENO-50, LENA, or other approved or proposed large liquid scintillator detectors. The main detection channels for supernova $\nu_e$ in a liquid scintillator are its elastic scattering with electrons and its charged-current interaction with the $^{12}$C nucleus. In existing scintillator detectors, the numbers of events from these interactions are too small to be very useful. However, at the 20-kton scale planned for the new detectors, these channels become powerful tools for probing the $\nu_e$ emission. We find that the $\nu_e$ spectrum can be well measured, to better than $\sim 40\%$ precision for the total energy and better than $\sim 25\%$ precision for the average energy. This is adequate to distinguish even close average energies, e.g., 11 MeV and 14 MeV, which will test the predictions of supernova models. In addition, it will help set constraints on neutrino mixing effects in supernovae by testing non-thermal spectra. Without such large liquid scintillator detectors (or Super-Kamiokande with added gadolinium, which has similar capabilities), supernova $\nu_e$ will be measured poorly, holding back progress on understanding supernovae, neutrinos, and possible new physics.
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    ABSTRACT: We present photometric and spectroscopic observations of ASASSN-13co, an unusually luminous Type II supernova and the first core-collapse supernova discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN). First detection of the supernova was on UT 2013 August 29 and the data presented span roughly 3.5 months after discovery. We use the recently developed model from Pejcha & Prieto (2014) to model the multi-band light curves of ASASSN-13co and derive the bolometric luminosity curve. We compare ASASSN-13co to other Type II supernovae to show that it was a unique event that was not only unusually bright for a Type II supernova but also exhibited an atypical light curve shape that does not cleanly match that of either a standard Type II-L or Type II-P supernova.
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    ABSTRACT: ASASSN-14ae is a candidate tidal disruption event (TDE) found at the center of SDSS J110840.11+340552.2 ($d\simeq200$ Mpc) by the All-Sky Automated Survey for Supernovae (ASAS-SN), a global array of 14-cm telescopes. The host galaxy is an early type spiral with no signs of an active galactic nucleus (AGN) and with little recent star formation. We present follow-up photometric and spectroscopic observations of the source, including optical data from ground-based telescopes and ultraviolet and optical data from Swift. From blackbody fits to the host-subtracted spectral energy distribution, we find that the transient had a peak luminosity of $L\simeq8\times10^{43}$ erg s$^{-1}$ and a total integrated energy of $E\simeq1.5\times10^{50}$ ergs over the $\sim3$ months of observations presented. The blackbody temperature of the transient remains roughly constant at $T\sim20,000$ K while the luminosity declines by nearly 1.5 orders of magnitude during this time, a drop that is most consistent with an exponential, $L\propto e^{-t/t_0}$ with $t_0\simeq32.5$ days. The source has broad Balmer lines in emission at all epochs, with the H$\alpha$ width evolving from $\sim17000$ km s$^{-1}$ near discovery to $\sim8000$ km s$^{-1}$ three months later. We also detect broad He II in our latest spectrum. We compare the color and spectral evolution to both supernovae (SNe) and normal AGN to show that ASASSN-14ae does not resemble either type of object and conclude that a TDE is the most likely explanation for our observations. At $z=0.0436$, ASASSN-14ae is the lowest-redshift TDE candidate discovered at optical/UV wavelengths to date, and based on its discovery in the first year of ASAS-SN operations, we estimate that ASAS-SN may discover $1-2$ of these events per year in the future.
    Monthly Notices of the Royal Astronomical Society 05/2014; 445(3). DOI:10.1093/mnras/stu1922 · 5.23 Impact Factor
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    Kenny C. Y. Ng, John F. Beacom
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    ABSTRACT: The first detection of high-energy astrophysical neutrinos by IceCube provides new opportunities for tests of neutrino properties. The long baseline through the Cosmic Neutrino Background (C$\nu$B) is particularly useful for directly testing secret neutrino interactions ($\nu$SI) that would cause neutrino-neutrino elastic scattering at a larger rate than the usual weak interactions. We show that IceCube can provide competitive sensitivity to $\nu$SI compared to other astrophysical and cosmological probes, which are complementary to laboratory tests. We study the spectral distortions caused by $\nu$SI with a large s-channel contribution, which can lead to a dip, bump, or cutoff on an initially smooth spectrum. Consequently, $\nu$SI may be an exotic solution for features seen in the IceCube energy spectrum. More conservatively, IceCube neutrino data can be used to set model-independent limits on $\nu$SI. Our phenomenological estimates provide guidance for more detailed calculations, comparisons to data, and model building.
    Physical Review D 04/2014; 90(6). DOI:10.1103/PhysRevD.90.065035 · 4.86 Impact Factor
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    ABSTRACT: Neutron tagging in Gadolinium-doped water may play a significant role in reducing backgrounds from atmospheric neutrinos in next generation proton-decay searches using megaton-scale Water Cherenkov detectors. Similar techniques might also be useful in the detection of supernova neutrinos. Accurate determination of neutron tagging efficiencies will require a detailed understanding of the number of neutrons produced by neutrino interactions in water as a function of momentum transferred. We propose the Atmospheric Neutrino Neutron Interaction Experiment (ANNIE), designed to measure the neutron yield of atmospheric neutrino interactions in gadolinium-doped water. An innovative aspect of the ANNIE design is the use of precision timing to localize interaction vertices in the small fiducial volume of the detector. We propose to achieve this by using early production of LAPPDs (Large Area Picosecond Photodetectors). This experiment will be a first application of these devices demonstrating their feasibility for Water Cherenkov neutrino detectors.
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    Shirley Weishi Li, John F. Beacom
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    ABSTRACT: When muons travel through matter, their energy losses lead to nuclear breakup ("spallation") processes. The delayed decays of unstable daughter nuclei produced by cosmic-ray muons are important backgrounds for low-energy astrophysical neutrino experiments, e.g., those seeking to detect solar neutrino or Diffuse Supernova Neutrino Background (DSNB) signals. Even though Super-Kamiokande has strong general cuts to reduce these spallation-induced backgrounds, the remaining rate before additional cuts for specific signals is much larger than the signal rates for kinetic energies of about 6 -- 18 MeV. Surprisingly, there is no published calculation of the production and properties of these backgrounds in water, though there are such studies for scintillator. Using the simulation code FLUKA and theoretical insights, we detail how muons lose energy in water, produce secondary particles, how and where these secondaries produce isotopes, and the properties of the backgrounds from their decays. We reproduce Super-Kamiokande measurements of the total background to within a factor of 2, which is good given that the isotope yields vary by orders of magnitude and that some details of the experiment are unknown to us at this level. Our results break aggregate data into component isotopes, reveal their separate production mechanisms, and preserve correlations between them. We outline how to implement more effective background rejection techniques using this information. Reducing backgrounds in solar and DSNB studies by even a factor of a few could help lead to important new discoveries.
    Physical Review C 02/2014; 89(4). DOI:10.1103/PhysRevC.89.045801 · 3.88 Impact Factor
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    ABSTRACT: We analyze a ΔV ~ –9 magnitude flare on the newly identified M8 dwarf SDSS J022116.84+194020.4 (hereafter SDSSJ0221) detected as part of the All-Sky Automated Survey for Supernovae. Using infrared and optical spectra, we confirm that SDSSJ0221 is a relatively nearby (d ~ 76 pc) M8 dwarf with strong quiescent Hα emission. Based on kinematics and the absence of features consistent with low-gravity (young) ultracool dwarfs, we place a lower limit of 200 Myr on the age of SDSSJ0221. When modeled with a simple, classical flare light curve, this flare is consistent with a total U-band flare energy EU ~ 1034 erg, confirming that the most dramatic flares are not limited to warmer, more massive stars. Scaled to include a rough estimate of the emission line contribution to the V band, we estimate a blackbody filling factor of ~10%-30% during the flare peak and ~0.5%-1.6% during the flare decay phase. These filling factors correspond to flare areas that are an order of magnitude larger than those measured for most mid-M dwarf flares. This publication is partially based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium.
    The Astrophysical Journal 02/2014; 781(2):L24-. DOI:10.1088/2041-8205/781/2/L24 · 6.28 Impact Factor
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    ABSTRACT: We discuss ASASSN-13db, an EXor accretion event on the young stellar object (YSO) SDSS J051011.01$-$032826.2 (hereafter SDSSJ0510) discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN). Using archival photometric data of SDSSJ0510 we construct a pre-outburst spectral energy distribution (SED) and find that it is consistent with a low-mass class II YSO near the Orion star forming region ($d \sim 420$ pc). We present follow-up photometric and spectroscopic observations of the source after the $\Delta V \sim-$3.7 mag outburst that began in September 2013. These data indicate an increase in temperature and luminosity consistent with an accretion rate of $\sim10^{-7}$ $\rm{M}_\odot$ yr$^{-1}$, three-to-five orders of magnitude greater than in quiescence. Spectroscopic observations show a forest of narrow emission lines dominated by neutral metallic lines from Fe I and some low-ionization lines. The properties of ASASSN-13db are similar to those of the EXor prototype EX~Lupi in late 2008 during its strongest observed outburst.
    The Astrophysical Journal Letters 01/2014; 785(2). DOI:10.1088/2041-8205/785/2/L35 · 5.60 Impact Factor
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    ABSTRACT: Even in the modern era, only human eyes scan the entire optical sky for the violent, variable, and transient events that shape our universe. The "All Sky Automated Survey for Supernovae" (ASAS-SN or "Assassin") is changing this by surveying the extragalactic sky roughly once a week, and within a year ASAS-SN will triple in size. We began running our real-time search for variable sources in late April 2013 with our first unit, "Brutus". Brutus presently consists of two telescopes on a common mount hosted by Las Cumbres Observatory Global Telescope Network in the Faulkes Telescope North enclosure on Mount Haleakala, Hawaii. Each telescope consists of a 14-cm Nikon telephoto lens and has a 4.47 by 4.47 degree field-of-view. On a typical clear night, it can survey 5000+ square degrees. The data are reduced in real-time, and we can search for transient candidates about an hour after the data are taken using an automated difference imaging pipeline. We are now meeting, and frequently exceeding, our current depth goal of 16 mag, corresponding to the apparent brightness at maximum light of core-collapse SNe within ~30 Mpc and SNe Ia out to ~100 Mpc. Brutus will shortly expand to have four cameras instead of two, and a second unit, "Cassius", with two cameras, should commence operations in early 2014 on Cerro Tololo, Chile. With these expansions, ASAS-SN will be able to observe the entire extragalactic sky every 2-3 nights. ASAS-SN has already discovered 10+ nearby SNe, 100+ outbursts from CVs and novae, 15+ M-dwarf and other stellar flares, and AGN outbursts which have resulted in 35+ ATel and CBET telegrams and 3 publications. In particular, ASAS-SN discovered one of the most extreme M-dwarf Flares ever detected (delta 9 mag). Furthermore, after triggering on an outburst in NGC 2617 we found that the AGN had changed from a Type 1.8 into a Type 1 Seyfert. After monitoring the transient with Swift and ground-based telescopes for 70 days, we clearly determined that the X-rays drove the variability with the UV-NIR emission showing delays in their response that increased with wavelength. ASAS-SN is an ongoing survey which, judging by its current success and future expansion, promises to be prolific for years to come.
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    Sheldon S. Campbell, John F. Beacom
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    ABSTRACT: Searches for dark matter annihilation signals in the diffuse gamma-ray background are promising. We present the first comprehensive study utilizing both flux and anisotropy, using the example of a spectral line signal. Besides improving sensitivity, a combined analysis will help separately determine the particle properties of dark matter and the cosmological aspects of its clumping into halo substructure. The significance of a signal in a shot-noise-dominated anisotropy analysis increases linearly with time $t$, as opposed to $\sqrt{t}$ for a flux analysis, so a flux hint might be confirmed with an anisotropy signal. A first combined line search with Fermi-LAT would provide powerful new sensitivity; one with the proposed GAMMA-400 would be dramatically better.
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    ABSTRACT: We obtained optical spectra of ASASSN-13dn (ATel #5665). The candidate was confirmed with the new KOSMOS instrument (Kitt Peak Ohio State Multi-Object Spectrograph), which is presently being commissioned at the KPNO 4-m Mayall telescope. Observations were obtained with both the blue and red VPH grisms (50 min each) for a combined wavelength range of 380nm to 965nm at R ~ 2000. The spectrum of ASASSN-13dn is characteristic of a Type II SN at the redshift of its host galaxy (z=0.023).
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    ABSTRACT: During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the recently expanded quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient source, possibly a supernova, in the outskirts of SDSS J125258.03+322444.3:
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    ABSTRACT: We obtained follow-up V-band images of ASASSN-13do (ATel #5694) on UT Dec. 27 with the LCOGT 1m telescope at McDonald Observatory. The source is undetected (V >~ 20 mag) and was most likely a false positive.
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    ABSTRACT: CBET 3758 available at Central Bureau for Astronomical Telegrams.
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    ABSTRACT: During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the recently expanded quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient source, likely a supernova, near the center of PGC 2816341:
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    ABSTRACT: During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the recently expanded quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient source, most likely a supernova:
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    Ranjan Laha, John F. Beacom
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    ABSTRACT: Detecting supernova $\nu_e$ is essential for testing supernova and neutrino physics, but the yields are small and the backgrounds from other channels large, e.g., $\sim 10^2$ and $\sim 10^4$ events, respectively, in Super-Kamiokande. We develop a new way to isolate supernova $\nu_e$, using gadolinium-loaded water Cherenkov detectors. The forward-peaked nature of $\nu_e + e^- \rightarrow \nu_e + e^-$ allows an angular cut that contains the majority of events. Even in a narrow cone, near-isotropic inverse beta events, $\bar{\nu}_e + p \rightarrow e^+ + n$, are a large background. With neutron detection by radiative capture on gadolinium, the background events can be individually identified with high efficiency. The remaining backgrounds are smaller and can be measured separately, so they can be statistically subtracted. Super-Kamiokande with gadolinium could measure the total and average energy of supernova $\nu_e$ with $\sim$ $20\%$ precision or better each ($90\%$ C.L.). Hyper-Kamiokande with gadolinium could improve this by a factor of $\sim$ 5. This precision will allow powerful tests of supernova neutrino emission, neutrino mixing, and exotic physics. Unless very large liquid argon or liquid scintillator detectors are built, this is the only way to guarantee precise measurements of supernova $\nu_e$.
    Physical Review D 11/2013; 89(6). DOI:10.1103/PhysRevD.89.063007 · 4.86 Impact Factor
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    ABSTRACT: We analyze a $\Delta$ V~9 magnitude flare on the newly identified M8 dwarf SDSS J022116.84+194020.4 (hereafter SDSSJ0221) detected as part of the All-Sky Automated Survey for Supernovae (ASAS-SN). This is the first photometric detection of a dramatic flare on an ultracool dwarf near enough to the Sun (d~76 pc) for follow-up spectroscopy. Using infrared and optical spectra, we confirm that SDSSJ0221 is an M8 dwarf with strong quiescent H$\alpha$ emission. Based on kinematics and the absence of features consistent with low-gravity (young) ultracool dwarfs, we place a lower limit of 200 Myr on the age of SDSSJ0221. When modeled with a simple, classical flare light-curve, this flare is consistent with a total U-band flare energy $E_U\sim10^{31}$ erg, confirming that dramatic flares are not limited to warmer, more massive stars. Scaled to include a rough estimate of the emission line contribution to the V band, we estimate a blackbody filling factor of 10% to 34% during the flare peak and 0.5% to 1.6% during the flare decay phase. These filling factors correspond to flare areas that are an order of magnitude larger than those measured for most mid-M dwarf flares.

Publication Stats

6k Citations
567.04 Total Impact Points

Institutions

  • 2004–2014
    • The Ohio State University
      • • Department of Physics
      • • Center for Cosmology and Astoparticle Physics
      • • Department of Astronomy
      Columbus, Ohio, United States
  • 2012
    • The University of Arizona
      • Department of Physics
      Tucson, Arizona, United States
  • 2006
    • University of California, Berkeley
      Berkeley, California, United States
  • 2001–2004
    • Fermi National Accelerator Laboratory (Fermilab)
      • Theoretical Physics Department
      Batavia, Illinois, United States
  • 2002
    • University of Chicago
      • Department of Astronomy and Astrophysics
      Chicago, Illinois, United States
  • 1998–2000
    • California Institute of Technology
      • Department of Physics
      Pasadena, California, United States
  • 1996–1998
    • University of Wisconsin, Madison
      • Department of Physics
      Mississippi, United States