Showing papers by "Peter Nugent published in 2012"
University of California, Santa Barbara1, Las Cumbres Observatory Global Telescope Network2, University of California, Berkeley3, Lawrence Berkeley National Laboratory4, University of Oxford5, Weizmann Institute of Science6, Kavli Institute for Theoretical Physics7, University of California, Santa Cruz8, University of Texas at Austin9, Hebrew University of Jerusalem10, California Institute of Technology11, Carnegie Institution for Science12, University of California, San Diego13, Dartmouth College14, Institute for the Physics and Mathematics of the Universe15, Max Planck Society16, University of Toronto17, Massachusetts Institute of Technology18, Tel Aviv University19
TL;DR: A temporal series of high-resolution optical spectra of the SN Ia PTF 11kx reveals a complex circumstellar environment that provides an unprecedentedly detailed view of the progenitor system.
Abstract: There is a consensus that type Ia supernovae (SNe Ia) arise from the thermonuclear explosion of white dwarf stars that accrete matter from a binary companion. However, direct observation of SN Ia progenitors is lacking, and the precise nature of the binary companion remains uncertain. A temporal series of high-resolution optical spectra of the SN Ia PTF 11kx reveals a complex circumstellar environment that provides an unprecedentedly detailed view of the progenitor system. Multiple shells of circumstellar material are detected, and the SN ejecta are seen to interact with circumstellar material starting 59 days after the explosion. These features are best described by a symbiotic nova progenitor, similar to RS Ophiuchi.
376 citations
TL;DR: In this paper, the authors present a new non-detection limit of the nearby SN Ia 2011fe, obtained at a time that appears to be just 4-hr after the explosion, allowing them to directly constrain the initial primary radius (Rp ).
Abstract: While a white dwarf (WD) is, from a theoretical perspective, the most plausible primary star of a Type Ia supernova (SN Ia), many other candidates have not been formally ruled out. Shock energy deposited in the envelope of any exploding primary contributes to the early SN brightness and, since this radiation energy is degraded by expansion after the explosion, the diffusive luminosity depends on the initial primary radius. We present a new non-detection limit of the nearby SN Ia 2011fe, obtained at a time that appears to be just 4 hr after explosion, allowing us to directly constrain the initial primary radius (Rp ). Coupled with the non-detection of a quiescent X-ray counterpart and the inferred synthesized 56Ni mass, we show that Rp 0.02 R ☉ (a factor of five smaller than previously inferred), that the average density of the primary must be ρ p > 104 g cm–3, and that the effective temperature must be less than a few × 105 K. This rules out hydrogen-burning main-sequence stars and giants. Constructing the helium-burning and carbon-burning main sequences, we find that such objects are also excluded. By process of elimination, we find that only degeneracy-supported compact objects—WDs and neutron stars—are viable as the primary star of SN 2011fe. With few caveats, we also restrict the companion (secondary) star radius to R c 0.1 R ☉, excluding Roche-lobe overflowing red giant and main-sequence companions to high significance.
293 citations
01 Nov 2012
TL;DR: The LSST Dark Energy Science Collaboration (DESC) as discussed by the authors is an analytical framework for dark energy and related topics in fundamental physics with data from the Large Synoptic Survey Telescope (LSST).
Abstract: This white paper describes the LSST Dark Energy Science Collaboration (DESC), whose goal is the study of dark energy and related topics in fundamental physics with data from the Large Synoptic Survey Telescope (LSST). It provides an overview of dark energy science and describes the current and anticipated state of the field. It makes the case for the DESC by laying out a robust analytical framework for dark energy science that has been defined by its members and the comprehensive three-year work plan they have developed for implementing that framework. The analysis working groups cover five key probes of dark energy: weak lensing, large scale structure, galaxy clusters, Type Ia supernovae, and strong lensing. The computing working groups span cosmological simulations, galaxy catalogs, photon simulations and a systematic software and computational framework for LSST dark energy data analysis. The technical working groups make the connection between dark energy science and the LSST system. The working groups have close linkages, especially through the use of the photon simulations to study the impact of instrument design and survey strategy on analysis methodology and cosmological parameter estimation. The white paper describes several high priority tasks identified by each of the 16 working groups. Over the next three years these tasks will help prepare for LSST analysis, make synergistic connections with ongoing cosmological surveys and provide the dark energy community with state of the art analysis tools. Members of the community are invited to join the LSST DESC, according to the membership policies described in the white paper. Applications to sign up for associate membership may be made by submitting the Web form at http://www.slac.stanford.edu/exp/lsst/desc/signup.html with a short statement of the work they wish to pursue that is relevant to the LSST DESC.
245 citations
University of Würzburg1, Max Planck Society2, Heidelberg Institute for Theoretical Studies3, Australian National University4, Lawrence Berkeley National Laboratory5, Pierre-and-Marie-Curie University6, Yale University7, University of Bonn8, University of California, Berkeley9, University of Lyon10, Tsinghua University11, Lyon College12, Chinese Academy of Sciences13
TL;DR: In this article, a simulation of a delayed detonation in a Chandrasekhar-mass white dwarf and a violent merger of two white dwarfs (WDs) was used to constrain SN Ia explosion scenarios.
Abstract: The nearby supernova SN 2011fe can be observed in unprecedented detail. Therefore, it is an important test case for Type Ia supernova (SN Ia) models, which may bring us closer to understanding the physical nature of these objects. Here, we explore how available and expected future observations of SN 2011fe can be used to constrain SN Ia explosion scenarios. We base our discussion on three-dimensional simulations of a delayed detonation in a Chandrasekhar-mass white dwarf and of a violent merger of two white dwarfs (WDs)—realizations of explosion models appropriate for two of the most widely discussed progenitor channels that may give rise to SNe Ia. Although both models have their shortcomings in reproducing details of the early and near-maximum spectra of SN 2011fe obtained by the Nearby Supernova Factory (SNfactory), the overall match with the observations is reasonable. The level of agreement is slightly better for the merger, in particular around maximum, but a clear preference for one model over the other is still not justified. Observations at late epochs, however, hold promise for discriminating the explosion scenarios in a straightforward way, as a nucleosynthesis effect leads to differences in the 55Co production. SN 2011fe is close enough to be followed sufficiently long to study this effect.
244 citations
California Institute of Technology1, Carnegie Institution for Science2, Weizmann Institute of Science3, Lawrence Berkeley National Laboratory4, University of California, Berkeley5, University of Oxford6, University of California, Santa Barbara7, Kavli Institute for Theoretical Physics8, Harvard University9, National Radio Astronomy Observatory10, Las Cumbres Observatory Global Telescope Network11, University of Toronto12, San Diego State University13, Tel Aviv University14, University of Tokyo15
TL;DR: Perets et al. as discussed by the authors identified three peculiar transients with five distinguishing characteristics: peak luminosity in the gap between novae and supernovae (M_R ≈ - 15.5 to -16.5), rapid photometric evolution (t_(rise) ≈12-15 days), large photospheric velocities (≈6000 to 11,000 km s^(-1)), early spectroscopic evolution into nebular phase (1 to 3 months) and peculiar nebular spectra dominated by Calcium.
Abstract: From the first two seasons of the Palomar Transient Factory, we identify three peculiar transients (PTF09dav, PTF10iuv, PTF11bij) with five distinguishing characteristics: peak luminosity in the gap between novae and supernovae (M_R ≈ - 15.5 to -16.5), rapid photometric evolution (t_(rise) ≈12-15 days), large photospheric velocities (≈6000 to 11000 km s^(-1)), early spectroscopic evolution into nebular phase (≈1 to 3 months) and peculiar nebular spectra dominated by Calcium. We also culled the extensive decade-long Lick Observatory Supernova Search database and identified an additional member of this group, SN 2007ke. Our choice of photometric and spectroscopic properties was motivated by SN 2005E (Perets et al. 2010). To our surprise, as in the case of SN 2005E, all four members of this group are also clearly offset from the bulk of their host galaxy. Given the well-sampled early and late-time light curves, we derive ejecta masses in the range of 0.4--0.7 M_⊙. Spectroscopically, we find that there may be a diversity in the photospheric phase, but the commonality is in the unusual nebular spectra. Our extensive follow-up observations rule out standard thermonuclear and standard core-collapse explosions for this class of "Calcium-rich gap" transients. If the progenitor is a white dwarf, we are likely seeing a detonation of the white dwarf core and perhaps, even shock-front interaction with a previously ejected nova shell. In the less likely scenario of a massive star progenitor, a very non-standard channel specific to a low-metallicity environment needs to be invoked (e.g., ejecta fallback leading to black hole formation). Detection (or lack thereof) of a faint underlying host (dwarf galaxy, cluster) will provide a crucial and decisive diagnostic to choose between these alternatives.
231 citations
Argonne National Laboratory1, University of Chicago2, Lawrence Berkeley National Laboratory3, University of Illinois at Urbana–Champaign4, Fermilab5, University of the Western Cape6, University of Hertfordshire7, University of Sussex8, Federal University of Rio de Janeiro9, University of Pennsylvania10, University of Oxford11
TL;DR: In this article, the authors present an analysis of supernova light curves simulated for the upcoming DES supernova search using a code suite that generates and fits realistic light curves in order to obtain distance modulus/redshift pairs that are passed to a cosmology fitter.
Abstract: We present an analysis of supernova light curves simulated for the upcoming Dark Energy Survey (DES) supernova search. The simulations employ a code suite that generates and fits realistic light curves in order to obtain distance modulus/redshift pairs that are passed to a cosmology fitter. We investigated several different survey strategies including field selection, supernova selection biases, and photometric redshift measurements. Using the results of this study, we chose a 30 deg2 search area in the griz filter set. We forecast (1) that this survey will provide a homogeneous sample of up to 4000 Type Ia supernovae in the redshift range 0.05
206 citations
TL;DR: In this article, a simulation of a delayed detonation in a Chandrasekhar-mass white dwarf and a violent merger of two white dwarfs-realizations of explosion models appropriate for two of the most widely-discussed progenitor channels that may give rise to SNe Ia is presented.
Abstract: The nearby supernova SN 2011fe can be observed in unprecedented detail. Therefore, it is an important test case for Type Ia supernova (SN Ia) models, which may bring us closer to understanding the physical nature of these objects. Here, we explore how available and expected future observations of SN 2011fe can be used to constrain SN Ia explosion scenarios. We base our discussion on three-dimensional simulations of a delayed detonation in a Chandrasekhar-mass white dwarf and of a violent merger of two white dwarfs-realizations of explosion models appropriate for two of the most widely-discussed progenitor channels that may give rise to SNe Ia. Although both models have their shortcomings in reproducing details of the early and near-maximum spectra of SN 2011fe obtained by the Nearby Supernova Factory (SNfactory), the overall match with the observations is reasonable. The level of agreement is slightly better for the merger, in particular around maximum, but a clear preference for one model over the other is still not justified. Observations at late epochs, however, hold promise for discriminating the explosion scenarios in a straightforward way, as a nucleosynthesis effect leads to differences in the 55Co production. SN 2011fe is close enough to be followed sufficiently long to study this effect.
198 citations
TL;DR: In this paper, the authors present the inner workings of a framework, based on machine-learning algorithms, that captures expert training and ground-truth knowledge about the variable and transient sky to automate the process of discovery on image differences, and the generation of preliminary science-type classifications of discovered sources.
Abstract: The rate of image acquisition in modern synoptic imaging surveys has already begun to outpace the feasibility of keeping astronomers in the real-time discovery and classification loop. Here we present the inner workings of a framework, based on machine-learning algorithms, that captures expert training and ground-truth knowledge about the variable and transient sky to automate (1) the process of discovery on image differences, and (2) the generation of preliminary science-type classifications of discovered sources. Since follow-up resources for extracting novel science from fast-changing transients are precious, self-calibrating classification probabilities must be couched in terms of efficiencies for discovery and purity of the samples generated. We estimate the purity and efficiency in identifying real sources with a two-epoch image-difference discovery algorithm for the Palomar Transient Factory (PTF) survey. Once given a source discovery, using machine-learned classification trained on PTF data, we distinguish between transients and variable stars with a 3.8% overall error rate (with 1.7% errors for imaging within the Sloan Digital Sky Survey footprint). At >96% classification efficiency, the samples achieve 90% purity. Initial classifications are shown to rely primarily on context-based features, determined from the data itself and external archival databases. In the first year of autonomous operations of PTF, this discovery and classification framework led to several significant science results, from outbursting young stars to subluminous Type IIP supernovae to candidate tidal disruption events. We discuss future directions of this approach, including the possible roles of crowdsourcing and the scalability of machine learning to future surveys such as the Large Synoptic Survey Telescope (LSST).
182 citations
Dartmouth College1, Las Cumbres Observatory Global Telescope Network2, University of California, Santa Barbara3, University of Oklahoma4, Lawrence Berkeley National Laboratory5, Harvard University6, University of California, Berkeley7, Weizmann Institute of Science8, Liverpool John Moores University9, California Institute of Technology10, Carnegie Institution for Science11, University of Toronto12, University of Oxford13, Max Planck Society14, Massachusetts Institute of Technology15, Tel Aviv University16, Institute for the Physics and Mathematics of the Universe17, University of Bonn18, University of Lyon19
TL;DR: In this article, the authors studied the early evolution of a "normal" SN Ia, its compositional structure, and its elusive progenitor system using high signal-to-noise spectra.
Abstract: The nearby Type Ia supernova (SN Ia) SN 2011fe in M101 (cz = 241 km s^(–1)) provides a unique opportunity to study the early evolution of a "normal" SN Ia, its compositional structure, and its elusive progenitor system. We present 18 high signal-to-noise spectra of SN 2011fe during its first month beginning 1.2 days post-explosion and with an average cadence of 1.8 days. This gives a clear picture of how various line-forming species are distributed within the outer layers of the ejecta, including that of unburned material (C+O). We follow the evolution of C II absorption features until they diminish near maximum light, showing overlapping regions of burned and unburned material between ejection velocities of 10,000 and 16,000 km s^(–1). This supports the notion that incomplete burning, in addition to progenitor scenarios, is a relevant source of spectroscopic diversity among SNe Ia. The observed evolution of the highly Doppler-shifted O I λ7774 absorption features detected within 5 days post-explosion indicates the presence of O I with expansion velocities from 11,500 to 21,000 km s^(–1). The fact that some O I is present above C II suggests that SN 2011fe may have had an appreciable amount of unburned oxygen within the outer layers of the ejecta.
180 citations
TL;DR: The Palomar Transient Factory (PTF) provides multiple epoch imaging for a large fraction of the celestial sphere as discussed by the authors, which enables the calibration of fields that are outside the SDSS footprint.
Abstract: The Palomar Transient Factory (PTF) provides multiple epoch imaging for a large fraction of the celestial sphere. Here, we describe the photometric calibration of the PTF data products that allows the PTF magnitudes to be related to other magnitude systems. The calibration process utilizes Sloan Digital Sky Survey (SDSS) r ∼ 16 mag point-source objects as photometric standards. During photometric conditions, this allows us to solve for the extinction coefficients and color terms and to estimate the camera illumination correction. This also enables the calibration of fields that are outside the SDSS footprint. We test the precision and repeatability of the PTF photometric calibration. Given that PTF is observing in a single filter each night, we define a PTF calibrated magnitude system for the R band and g band. We show that, in this system, ≈59% (47%) of the photometrically calibrated PTF R-band (g-band) data achieve a photometric precision of 0.02–0.04 mag and have color terms and extinction coefficients that are close to their average values. Given the objects’ color, the PTF magnitude system can be converted to other systems. Moreover, a night-by-night comparison of the calibrated magnitudes of individual stars observed on multiple nights shows that they are consistent to a level of ≈0.02 mag. Most of the data that were taken under nonphotometric conditions can be calibrated relative to other epochs of the same sky footprint obtained during photometric conditions. We provide a concise guide describing how to use the PTF photometric-calibration data products, as well as the transformations between the PTF magnitude system and the SDSS and Johnson-Cousins systems.
179 citations
California Institute of Technology1, Pennsylvania State University2, Carnegie Institution for Science3, Weizmann Institute of Science4, University of Tokyo5, University of California, Berkeley6, ASTRON7, University of Wisconsin–Milwaukee8, Marshall Space Flight Center9, University of Oxford10, University of California, Santa Barbara11, Lawrence Berkeley National Laboratory12, Goddard Space Flight Center13, University of Toronto14, Ben-Gurion University of the Negev15
TL;DR: In this article, the authors present the analysis of radio and X-ray observations, yielding the tightest constraints yet placed on the pre-explosion mass-loss rate from the progenitor system of this supernova.
Abstract: On August 24 (UT) the Palomar Transient Factory (PTF) discovered PTF11kly (SN 2011fe), the youngest and most nearby type Ia supernova (SN Ia) in decades. We followed this event up in the radio (centimeter and millimeter bands) and X-ray bands, starting about a day after the estimated explosion time. We present our analysis of the radio and X-ray observations, yielding the tightest constraints yet placed on the pre-explosion mass-loss rate from the progenitor system of this supernova. We find a robust limit of M(raised dot) less than or equal to 10(exp -8) (w /100 kilometers per second ) solar mass yr(exp -1) from sensitive X-ray non-detections, as well as a similar limit from radio data, which depends, however, on assumptions about microphysical parameters. We discuss our results in the context of single-degenerate models for SNe Ia and find that our observations modestly disfavor symbiotic progenitor models involving a red giant donor, but cannot constrain systems accreting from main sequence or sub-giant stars, including the popular supersoft channel. In view of the proximity of PTF11kly and the sensitivity of our prompt observations we would have to wait for a long time (decade or longer) in order to more meaningfully probe the circumstellar matter of Ia supernovae.
University of Oxford1, California Institute of Technology2, Lawrence Berkeley National Laboratory3, University of California, Berkeley4, Las Cumbres Observatory Global Telescope Network5, University of California, Santa Barbara6, Weizmann Institute of Science7, Swinburne University of Technology8, Max Planck Society9, Liverpool John Moores University10, INAF11, Carnegie Learning12, Scuola Normale Superiore di Pisa13, Carnegie Institution for Science14, University of Toronto15, Tel Aviv University16
TL;DR: In this article, the authors present an analysis of the maximum light, near-ultraviolet (NUV; 2900 < λ < 5500 A) spectra of 32 low-redshift (0.001 < z < 0.08) Type Ia supernovae (SNe Ia), obtained with the Hubble Space Telescope (HST) using the Space Telescope Imaging Spectrograph.
Abstract: We present an analysis of the maximum light, near-ultraviolet (NUV; 2900 < λ < 5500 A) spectra of 32 low-redshift (0.001 < z < 0.08) Type Ia supernovae (SNe Ia), obtained with the Hubble Space Telescope (HST) using the Space Telescope Imaging Spectrograph. We combine this spectroscopic sample with high-quality gri light curves obtained with robotic telescopes to measure SN Ia photometric parameters, such as stretch (light-curve width), optical colour and brightness (Hubble residual). By comparing our new data to a comparable sample of SNe Ia at intermediate redshift (0.4 < z < 0.9), we detect modest spectral evolution (3σ), in the sense that our mean low-redshift NUV spectrum has a depressed flux compared to its intermediate-redshift counterpart. We also see a strongly increased dispersion about the mean with decreasing wavelength, confirming the results of earlier surveys. We show that these trends are consistent with changes in metallicity as predicted by contemporary SN Ia spectral models. We also examine the properties of various NUV spectral diagnostics in the individual SN spectra. We find a general correlation between SN stretch and the velocity (or position) of many NUV spectral features. In particular, we observe that higher stretch SNe have larger Ca ii H&K velocities, which also correlate with host galaxy stellar mass. This latter trend is probably driven by the well-established correlation between stretch and host galaxy stellar mass. We find no significant trends between UV spectral features and optical colour. Mean spectra constructed according to whether the SN has a positive or negative Hubble residual show very little difference at NUV wavelengths, indicating that the NUV evolution and variation we identify does not directly correlate with Hubble diagram residuals. Our work confirms and strengthens earlier conclusions regarding the complex behaviour of SNe Ia in the NUV spectral region, but suggests the correlations we find are more useful in constraining progenitor models rather than improving the use of SNe Ia as cosmological probes.
California Institute of Technology1, Pennsylvania State University2, Las Cumbres Observatory Global Telescope Network3, University of California, Berkeley4, Ames Research Center5, University of Washington6, University of Toronto7, Lawrence Berkeley National Laboratory8, Weizmann Institute of Science9, Tel Aviv University10, University of Tokyo11
TL;DR: In this article, the authors reported observations of a possible young transiting planet orbiting a previously known weak-lined T-Tauri star in the 7-10 Myr old Orion-OB1a/25-Ori region.
Abstract: We report observations of a possible young transiting planet orbiting a previously known weak-lined T-Tauri star in the 7–10 Myr old Orion-OB1a/25-Ori region. The candidate was found as part of the Palomar Transient Factory (PTF) Orion project. It has a photometric transit period of 0.448413 ± 0.000040 days, and appears in both 2009 and 2010 PTF data. Follow-up low-precision radial velocity (RV) observations and adaptive optics imaging suggest that the star is not an eclipsing binary, and that it is unlikely that a background source is blended with the target and mimicking the observed transit. RV observations with the Hobby–Eberly and Keck telescopes yield an RV that has the same period as the photometric event, but is offset in phase from the transit center by ≈ − 0.22 periods. The amplitude (half range) of the RV variations is 2.4 km s^(−1) and is comparable with the expected RV amplitude that stellar spots could induce. The RV curve is likely dominated by stellar spot modulation and provides an upper limit to the projected companion mass of M_psin i_(orb) ≾4.8 ± 1.2 M_(Jup); when combined with the orbital inclination, i_(orb), of the candidate planet from modeling of the transit light curve, we find an upper limit on the mass of the planetary candidate of M_p ≾5.5 ± 1.4 M_(Jup). This limit implies that the planet is orbiting close to, if not inside, its Roche limiting orbital radius, so that it may be undergoing active mass loss and evaporation.
University of California, Berkeley1, California Institute of Technology2, University of Tokyo3, Weizmann Institute of Science4, University of California, Santa Barbara5, Tel Aviv University6, Lawrence Berkeley National Laboratory7, National Radio Astronomy Observatory8, University of California, Davis9, University of Oxford10, Las Cumbres Observatory Global Telescope Network11, University of Toronto12
TL;DR: In this paper, the authors presented the discovery and characterization of PTF10iya, a short-lived (Δt≈ 10 d) transient source with an optical decay rate of ∼ 0.3 mag d−1.
Abstract: We present the discovery and characterization of PTF10iya, a short-lived (Δt≈ 10 d, with an optical decay rate of ∼0.3 mag d^(−1)), luminous (M_(g') ≈ -21) transient source found by the Palomar Transient Factory. The ultraviolet/optical spectral energy distribution is reasonably well fitted by a blackbody with T≈ (1–2) × 10^4 K and peak bolometric luminosity LBB≈ (1–5) × 10^(44) erg s^(−1) (depending on the details of the extinction correction). A comparable amount of energy is radiated in the X-ray band that appears to result from a distinct physical process. The location of PTF10iya is consistent with the nucleus of a star-forming galaxy (z= 0.224 05 ± 0.000 06) to within 350 mas (99.7 per cent confidence radius), or a projected distance of less than 1.2 kpc. At first glance, these properties appear reminiscent of the characteristic ‘big blue bump’ seen in the near-ultraviolet spectra of many active galactic nuclei (AGNs). However, emission-line diagnostics of the host galaxy, along with a historical light curve extending back to 2007, show no evidence for AGN-like activity. We therefore consider whether the tidal disruption of a star by an otherwise quiescent supermassive black hole may account for our observations. Though with limited temporal information, PTF10iya appears broadly consistent with the predictions for the early ‘super-Eddington’ phase of a solar-type star being disrupted by a ∼10^7 M_⊙ black hole. Regardless of the precise physical origin of the accreting material, the large luminosity and short duration suggest that otherwise quiescent galaxies can transition extremely rapidly to radiate near the Eddington limit; many such outbursts may have been missed by previous surveys lacking sufficient cadence.
TL;DR: The PTF photometric catalog 1.0 as mentioned in this paper contains calibrated R_PTF-filter magnitudes for ≈2.1 × 10^7 sources brighter than magnitude 19, over an area of ≈11,233 deg^2.
Abstract: We constructed a photometrically calibrated catalog of non-variable sources from the Palomar Transient Factory (PTF) observations. The first version of this catalog presented here, the PTF photometric catalog 1.0, contains calibrated R_PTF-filter magnitudes for ≈2.1 × 10^7 sources brighter than magnitude 19, over an area of ≈11,233 deg^2. The magnitudes are provided in the PTF photometric system, and the color of a source is required in order to convert these magnitudes into other magnitude systems. We estimate that the magnitudes in this catalog have a typical accuracy of about 0.02 mag with respect to magnitudes from the Sloan Digital Sky Survey. The median repeatability of our catalog’s magnitudes for stars between 15 and 16 mag, is about 0.01 mag and it is over 0.03 mag for 95% of the sources in this magnitude range. The main goal of this catalog is to provide reference magnitudes for photometric calibration of visible light observations. Subsequent versions of this catalog, which will be published incrementally online, will be extended to cover a larger sky area and will also include g_PTF-filter magnitudes, as well as variability and proper-motion information.
Australian National University1, Lawrence Berkeley National Laboratory2, Pierre-and-Marie-Curie University3, University of Washington4, Yale University5, University of Bonn6, University of California, Berkeley7, Lyon College8, Tsinghua University9, New York University10, Chinese Academy of Sciences11
TL;DR: In this paper, optical photometry and spectroscopy of five Type Ia supernovae discovered by the Nearby Supernova Factory selected to be spectroscopic analogs of the candidate super-Chandrasekhar-mass events SN-2003fg and SN-2007if.
Abstract: We present optical photometry and spectroscopy of five Type Ia supernovae discovered by the Nearby Supernova Factory selected to be spectroscopic analogs of the candidate super-Chandrasekhar-mass events SN 2003fg and SN 2007if. Their spectra are characterized by hot, highly ionized photospheres near maximum light, for which SN 1991T supplies the best phase coverage among available close spectral templates. Like SN 2007if, these supernovae are overluminous (–19.5 < MV < –20) and the velocity of the Si II λ6355 absorption minimum is consistent with being constant in time from phases as early as a week before, and up to two weeks after, B-band maximum light. We interpret the velocity plateaus as evidence for a reverse-shock shell in the ejecta formed by interaction at early times with a compact envelope of surrounding material, as might be expected for SNe resulting from the mergers of two white dwarfs. We use the bolometric light curves and line velocity evolution of these SNe to estimate important parameters of the progenitor systems, including 56Ni mass, total progenitor mass, and masses of shells and surrounding carbon/oxygen envelopes. We find that the reconstructed total progenitor mass distribution of the events (including SN 2007if) is bounded from below by the Chandrasekhar mass, with SN 2007if being the most massive. We discuss the relationship of these events to the emerging class of super-Chandrasekhar-mass SNe Ia, estimate the relative rates, compare the mass distribution to that expected for double-degenerate SN Ia progenitors from population synthesis, and consider implications for future cosmological Hubble diagrams.
University of Toronto1, University of Hawaii2, Las Cumbres Observatory Global Telescope Network3, California Institute of Technology4, University of California, Santa Barbara5, University of California, Berkeley6, Inter-University Centre for Astronomy and Astrophysics7, Carnegie Institution for Science8, Lawrence Berkeley National Laboratory9, Tel Aviv University10
TL;DR: In this article, the authors presented three new eclipsing white-dwarf/M-drab binary systems discovered during a search for transiting planets around early M-drabbfs.
Abstract: We present three new eclipsing white-dwarf/M-dwarf binary systems discovered during a search for transiting planets around M-dwarfs. Unlike most known eclipsing systems of this type, the optical and infrared emission is dominated by the M-dwarf components, and the systems have optical colors and discovery light curves consistent with being Jupiter-radius transiting planets around early M-dwarfs. We detail the PTF/M-dwarf transiting planet survey, part of the Palomar Transient Factory (PTF). We present a graphics processing unit (GPU)-based box-least-squares search for transits that runs approximately 8 × faster than similar algorithms implemented on general purpose systems. For the discovered systems, we decompose low-resolution spectra of the systems into white-dwarf and M-dwarf components, and use radial velocity measurements and cooling models to estimate masses and radii for the white dwarfs. The systems are compact, with periods between 0.35 and 0.45 days and semimajor axes of approximately 2 R_☉ (0.01 AU). The M-dwarfs have masses of approximately 0.35 M_☉, and the white dwarfs have hydrogen-rich atmospheres with temperatures of around 8000 K and have masses of approximately 0.5 M_☉. We use the Robo-AO laser guide star adaptive optics system to tentatively identify one of the objects as a triple system. We also use high-cadence photometry to put an upper limit on the white-dwarf radius of 0.025 R_☉ (95% confidence) in one of the systems. Accounting for our detection efficiency and geometric factors, we estimate that 0.08%^(+0.10%)_(-0.05%) (90% confidence) of M-dwarfs are in these short-period, post-common-envelope white-dwarf/M-dwarf binaries where the optical light is dominated by the M-dwarf. The lack of detections at shorter periods, despite near-100% detection efficiency for such systems, suggests that binaries including these relatively low-temperature white dwarfs are preferentially found at relatively large orbital radii. Similar eclipsing binary systems can have arbitrarily small eclipse depths in red bands and generate plausible small-planet-transit light curves. As such, these systems are a source of false positives for M-dwarf transiting planet searches. We present several ways to rapidly distinguish these binaries from transiting planet systems.
University of Melbourne1, Australian Astronomical Observatory2, Swinburne University of Technology3, Las Cumbres Observatory Global Telescope Network4, University of California, Santa Barbara5, INAF6, University of Oxford7, Lawrence Berkeley National Laboratory8, Weizmann Institute of Science9, University of California, Berkeley10, Carnegie Institution for Science11, Tel Aviv University12
TL;DR: In this paper, the authors present an analysis of the Hubble diagram for 12 normal Type Ia supernovae (SNe Ia) observed in the near-infrared (NIR) J and H bands.
Abstract: We present an analysis of the Hubble diagram for 12 normal Type Ia supernovae (SNe Ia) observed in the near-infrared (NIR) J and H bands. We select SNe exclusively from the redshift range 0.03 < z < 0.09 to reduce uncertainties coming from peculiar velocities while remaining in a cosmologically well-understood region. All of the SNe in our sample exhibit no spectral or B-band light-curve peculiarities and lie in the B-band stretch range of 0.8-1.15. Our results suggest that SNe Ia observed in the NIR are the best known standard candles. We fit previously determined NIR light-curve templates to new high-precision data to derive peak magnitudes and to determine the scatter about the Hubble line. Photometry of the 12 SNe is presented in the natural system. Using a standard cosmology of (H 0, Ω m, Ω Λ) = (70, 0.27, 0.73), we find a median J-band absolute magnitude of M J = -18.39 with a scatter of σ J = 0.116 and a median H-band absolute magnitude of M H = -18.36 with a scatter of σ H = 0.085. The scatter in the H band is the smallest yet measured. We search for correlations between residuals in the J- and H-band Hubble diagrams and SN properties, such as SN colour, B-band stretch and the projected distance from the centre of the host galaxy. The only significant correlation is between the J-band Hubble residual and the J - H pseudo-colour. We also examine how the scatter changes when fewer points in the NIR are used to constrain the light curve. With a single point in the H band taken anywhere from 10d before to 15d after B-band maximum light and a prior on the date of H-band maximum set from the date of B-band maximum, we find that we can measure distances to an accuracy of 6 per cent. The precision of SNe Ia in the NIR provides new opportunities for precision measurements of both the expansion history of the universe and peculiar velocities of nearby galaxies. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.
Texas A&M University1, University of California, Berkeley2, Tsinghua University3, University of Oklahoma4, Max Planck Society5, University of Hamburg6, Chinese Academy of Sciences7, Lawrence Berkeley National Laboratory8, University of Arizona9, European Southern Observatory10, University of Hawaii at Manoa11, DSM12, Princeton University13, University of Barcelona14, University of Toronto15, Harvard University16, Columbia University17, Sapienza University of Rome18, University of Würzburg19, Stockholm University20, Weizmann Institute of Science21, University of Notre Dame22, Florida State University23, University of Chile24, Goddard Space Flight Center25, University of Chicago26, Rutgers University27, Northern Arizona University28, Quest University29, University of Tennessee30, San Diego State University31, Massachusetts Institute of Technology32, Space Telescope Science Institute33, Tel Aviv University34, Imperial College London35, University of Tokyo36, Carnegie Institution for Science37, University of Victoria38, University of Texas at San Antonio39, Australian National University40, National Radio Astronomy Observatory41, Arizona State University42, Western Kentucky University43, California Institute of Technology44, United States Naval Research Laboratory45, University of Texas at Austin46, University of Pittsburgh47, University of California, Santa Cruz48, Kyushu University49
TL;DR: In this paper, ultraviolet spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope is presented.
Abstract: We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This data set provides unique spectral time series down to 2000 A. Significant diversity is seen in the near-maximum-light spectra (~2000-3500 A) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminosities measured in the uvw1/F250W filter are found to correlate with the B-band light-curve shape parameter Δm 15(B), but with much larger scatter relative to the correlation in the broadband B band (e.g., ~0.4 mag versus ~0.2 mag for those with 0.8 mag 3σ), being brighter than normal SNe Ia such as SN 2005cf by ~0.9 mag and ~2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.
TL;DR: In this paper, the authors present optical light curves of 29 novae in M31 during the 2009 and 2010 observing seasons of the Palomar Transient Factory (PTF).
Abstract: We present optical light curves of 29 novae in M31 during the 2009 and 2010 observing seasons of the Palomar Transient Factory (PTF). The dynamic and rapid cadences in PTF monitoring of M31, from one day to ten minutes, provide excellent temporal coverage of nova light curves, enabling us to record the photometric evolution of M31 novae in unprecedented detail. We also detect eight of these novae in the near-ultraviolet (UV) band with the Galaxy Evolution Explorer (GALEX) satellite. Novae M31N 2009-10b and M31N 2010-11a show prominent UV emission peaking a few days prior to their optical maxima, possibly implying aspherical outbursts. Additionally, our blueshifted spectrum of the recent outburst of PT And (M31N 2010-12a) indicates that it is a recurrent nova in M31 and not a dwarf nova in the Milky Way as was previously assumed. Finally, we systematically searched for novae in all confirmed globular clusters (GCs) of M31 and found only M31N 2010-10f associated with Bol 126. The specific nova rate in the M31 GC system is thus about one per year, which is not enhanced relative to the rate outside the GC system.
TL;DR: In this paper, the authors present photometry and spectroscopy of the peculiar Type II supernova (SN) SN 2010jp, also named PTF10aaxi, and propose that this line profile indicates a bipolar jet-driven explosion, with the central component produced by normal SN ejecta and CSM interaction at mid and low latitudes, while the high-velocity bumps and broad-line wings arise in a nonrelativistic bipolar jet.
Abstract: We present photometry and spectroscopy of the peculiar Type II supernova (SN) SN 2010jp, also named PTF10aaxi. The light curve exhibits a linear decline with a relatively low peak absolute magnitude of only −15.9 (unfiltered), and a low radioactive decay luminosity at late times, which suggests a low synthesized nickel mass of M (^(56) Ni) ≲ 0.003 M_⊙. Spectra of SN 2010jp display an unprecedented triple-peaked Hα line profile, showing (1) a narrow (full width at half-maximum ≳800 km s−1) central component that suggests shock interaction with dense circumstellar material (CSM); (2) high-velocity blue and red emission features centred at −12 600 and +15 400 km s^(−1), respectively; and (3) very broad wings extending from −22 000 to +25 000 km s−1. These features persist over multiple epochs during the ∼100 d after explosion. We propose that this line profile indicates a bipolar jet-driven explosion, with the central component produced by normal SN ejecta and CSM interaction at mid and low latitudes, while the high-velocity bumps and broad-line wings arise in a non-relativistic bipolar jet. Two variations of the jet interpretation seem plausible: (1) a fast jet mixes ^(56)Ni to high velocities in polar zones of the H-rich envelope; or (2) the reverse shock in the jet produces blue and red bumps in Balmer lines when a jet interacts with dense CSM. Jet-driven Type II SNe are predicted for collapsars resulting from a wide range of initial masses above 25 M_⊙, especially at subsolar metallicity. This seems consistent with the SN host environment, which is either an extremely low-luminosity dwarf galaxy or the very remote parts of an interacting pair of star-forming galaxies. It also seems consistent with the apparently low ^(56)Ni mass that may accompany black hole formation. We speculate that the jet survives to produce observable signatures because the star’s H envelope was very low mass, having been mostly stripped away by the previous eruptive mass-loss indicated by the Type IIn features in the spectrum.
Weizmann Institute of Science1, University of California, Berkeley2, Max Planck Society3, New York University4, California Institute of Technology5, Las Cumbres Observatory Global Telescope Network6, University of California, Santa Barbara7, San Diego State University8, Seoul National University9, Scuola Normale Superiore di Pisa10, University of Oxford11, Liverpool John Moores University12, Lawrence Berkeley National Laboratory13, Texas A&M University14, Palomar College15, Pennsylvania State University16, University of California, San Diego17, INAF18, Carnegie Institution for Science19, University of California, Los Angeles20, University of Tokyo21, University of Arizona22
TL;DR: In this paper, the discovery and extensive early-time observations of the Type Ic supernova PTF12gzk have been presented, and a dense spectral sequence is used to estimate the physical parameters of the exploding star and of the explosion.
Abstract: We present the discovery and extensive early-time observations of the Type Ic supernova (SN) PTF12gzk. Our light curves show a rise of 0.8 mag within 2.5 hr. Power-law fits (f(t)∝(t – t 0) n ) to these data constrain the explosion date to within one day. We cannot rule out a quadratic fireball model, but higher values of n are possible as well for larger areas in the fit parameter space. Our bolometric light curve and a dense spectral sequence are used to estimate the physical parameters of the exploding star and of the explosion. We show that the photometric evolution of PTF12gzk is slower than that of most SNe Ic. The high ejecta expansion velocities we measure (~30, 000 km s–1 derived from line minima four days after explosion) are similar to the observed velocities of broad-lined SNe Ic associated with gamma-ray bursts (GRBs) rather than to normal SN Ic velocities. Yet, this SN does not show the persistent broad lines that are typical of broad-lined SNe Ic. The host-galaxy characteristics are also consistent with GRB-SN hosts, and not with normal SN Ic hosts. By comparison with the spectroscopically similar SN 2004aw, we suggest that the observed properties of PTF12gzk indicate an initial progenitor mass of 25-35 M ☉ and a large ((5-10) × 1051 erg) kinetic energy, the later being close to the regime of GRB-SN properties.
TL;DR: The PTF photometric catalog 1.0 as discussed by the authors contains calibrated R_PTF-filter magnitudes for about 21 million sources brighter than magnitude 19, over an area of about 11233 deg^2.
Abstract: We construct a photometrically calibrated catalog of non-variable sources from the Palomar Transient Factory (PTF) observations. The first version of this catalog presented here, the PTF photometric catalog 1.0, contains calibrated R_PTF-filter magnitudes for about 21 million sources brighter than magnitude 19, over an area of about 11233 deg^2. The magnitudes are provided in the PTF photometric system, and the color of a source is required in order to convert these magnitudes into other magnitude systems. We estimate that the magnitudes in this catalog have typical accuracy of about 0.02 mag with respect to magnitudes from the Sloan Digital Sky Survey. The median repeatability of our catalog's magnitudes for stars between 15 and 16 mag, is about 0.01 mag, and it is better than 0.03 mag for 95% of the sources in this magnitude range. The main goal of this catalog is to provide reference magnitudes for photometric calibration of visible light observations. Subsequent versions of this catalog, which will be published incrementally online, will be extended to a larger sky area and will also include g_PTF-filter magnitudes, as well as variability and proper motion information.
California Institute of Technology1, Weizmann Institute of Science2, National Radio Astronomy Observatory3, Tel Aviv University4, Max Planck Society5, University of California, Berkeley6, Pennsylvania State University7, Hebrew University of Jerusalem8, University of Toronto9, Lawrence Berkeley National Laboratory10
TL;DR: In this article, the authors presented the discovery of PTF 10vgv, a Type Ic supernova (SN) detected by the Palomar Transient Factory, using the P48 telescope.
Abstract: We present the discovery of PTF 10vgv, a Type Ic supernova (SN) detected by the Palomar Transient Factory, using the Palomar 48 inch telescope (P48). R-band observations of the PTF 10vgv field with P48 probe the SN emission from its very early phases (about two weeks before R-band maximum) and set limits on its flux in the week prior to the discovery. Our sensitive upper limits and early detections constrain the post-shock-breakout luminosity of this event. Via comparison to numerical (analytical) models, we derive an upper-limit of R ≾ 4.5 R_☉ (R ≾ 1 R_☉) on the radius of the progenitor star, a direct indication in favor of a compact Wolf-Rayet star. Applying a similar analysis to the historical observations of SN 1994I yields R ≾ 1/4 R_☉ for the progenitor radius of this SN.
TL;DR: In this paper, the discovery and extensive early-time observations of the Type Ic supernova (SN) PTF12gzk were presented, where the authors used the bolometric light curve and a dense spectral sequence to estimate the physical parameters of the exploding star and of the explosion.
Abstract: We present the discovery and extensive early-time observations of the Type Ic supernova (SN) PTF12gzk. Our finely sampled light curves show a rise of 0.8mag within 2.5hr. Power-law fits [f(t)\sim(t-t_0)^n] to these data constrain the explosion date to within one day. We cannot rule out the expected quadratic fireball model, but higher values of n are possible as well for larger areas in the fit parameter space. Our bolometric light curve and a dense spectral sequence are used to estimate the physical parameters of the exploding star and of the explosion. We show that the photometric evolution of PTF12gzk is slower than that of most SNe Ic, and its high ejecta velocities (~30,000km/s four days after explosion) are closer to the observed velocities of broad-lined SNe Ic associated with gamma-ray bursts (GRBs) than to the observed velocities in normal Type Ic SNe. The high velocities are sustained through the SN early evolution, and are similar to those of GRB-SNe when the SN reach peak magnitude. By comparison with the spectroscopically similar SN 2004aw, we suggest that the observed properties of PTF12gzk indicate an initial progenitor mass of 25-35 solar mass and a large (5-10E51 erg) kinetic energy, close to the regime of GRB-SN properties. The host-galaxy characteristics are consistent with GRB-SN hosts, and not with normal SN Ic hosts as well, yet this SN does not show the broad lines over extended periods of time that are typical of broad-line Type Ic SNe.
TL;DR: In this paper, the authors used PTF observations of fields that were observed multiple times (≳10) per night, for several nights, to find asteroids, construct their light curves and measure their rotation periods.
Abstract: The Palomar Transient Factory (PTF) is a synoptic survey designed to explore the transient and variable sky in a wide variety of cadences. We use PTF observations of fields that were observed multiple times (≳10) per night, for several nights, to find asteroids, construct their light curves and measure their rotation periods. Here we describe the pipeline we use to achieve these goals and present the results from the first four (overlapping) PTF fields analysed as part of this programme. These fields, which cover an area of 21 deg^2, were observed on four nights with a cadence of ∼20 min. Our pipeline was able to detect 624 asteroids, of which 145 (≈20 per cent) were previously unknown. We present high-quality rotation periods for 88 main-belt asteroids and possible period or lower limit on the period for an additional 85 asteroids. For the remaining 451 asteroids, we present lower limits on their photometric amplitudes. Three of the asteroids have light curves that are characteristic of binary asteroids. We estimate that implementing our search for all existing high-cadence PTF data will provide rotation periods for about 10 000 asteroids mainly in the magnitude range ≈14 to ≈20.
TL;DR: BinaryFinder as discussed by the authors uses point-spread-functions (PSF) ellipticity measurements across wide-field survey images to search for close binaries by using precision measurements of PSF ellipticity across wide field images.
Abstract: The direct detection of binary systems in wide-field surveys is limited by the size of the stars' point-spread-functions (PSFs). A search for elongated objects can find closer companions, but is limited by the precision to which the PSF shape can be calibrated for individual stars. We have developed the BinaryFinder algorithm to search for close binaries by using precision measurements of PSF ellipticity across wide-field survey images. We show that the algorithm is capable of reliably detecting binary systems down to approximately 1/5 of the seeing limit, and can directly measure the systems' position angles, separations and contrast ratios. To verify the algorithm's performance we evaluated 100,000 objects in Palomar Transient Factory (PTF) wide-field-survey data for signs of binarity, and then used the Robo-AO robotic laser adaptive optics system to verify the parameters of 44 high-confidence targets. We show that BinaryFinder correctly predicts the presence of close companions with a <5% false-positive rate, measures the detected binaries' position angles within 2 degrees and separations within 25%, and weakly constrains their contrast ratios. When applied to the full PTF dataset, we estimate that BinaryFinder will discover and characterize ~450,000 physically-associated binary systems with separations <2 arcseconds and magnitudes brighter than R=18. New wide-field synoptic surveys with high sensitivity and sub-arcsecond angular resolution, such as LSST, will allow BinaryFinder to reliably detect millions of very faint binary systems with separations as small as 0.1 arcseconds.
Las Cumbres Observatory Global Telescope Network1, Dartmouth College2, University of California, Santa Barbara3, University of Oklahoma4, Lawrence Berkeley National Laboratory5, Harvard University6, University of California, Berkeley7, Weizmann Institute of Science8, Liverpool John Moores University9, California Institute of Technology10, Carnegie Institution for Science11, University of Toronto12, University of Oxford13, Max Planck Society14, Massachusetts Institute of Technology15, Tel Aviv University16, Institute for the Physics and Mathematics of the Universe17, University of Bonn18, University of Lyon19
TL;DR: In this article, the authors studied the early evolution of a "normal" Type Ia supernova, its compositional structure, and its elusive progenitor system using high signal-to-noise spectra.
Abstract: The nearby Type Ia supernova SN 2011fe in M101 (cz=241 km s^-1) provides a unique opportunity to study the early evolution of a "normal" Type Ia supernova, its compositional structure, and its elusive progenitor system. We present 18 high signal-to-noise spectra of SN 2011fe during its first month beginning 1.2 days post-explosion and with an average cadence of 1.8 days. This gives a clear picture of how various line-forming species are distributed within the outer layers of the ejecta, including that of unburned material (C+O). We follow the evolution of C II absorption features until they diminish near maximum light, showing overlapping regions of burned and unburned material between ejection velocities of 10,000 and 16,000 km s^-1. This supports the notion that incomplete burning, in addition to progenitor scenarios, is a relevant source of spectroscopic diversity among SNe Ia. The observed evolution of the highly Doppler-shifted O I 7774 absorption features detected within five days post-explosion indicate the presence of O I with expansion velocities from 11,500 to 21,000 km s^-1. The fact that some O I is present above C II suggests that SN 2011fe may have had an appreciable amount of unburned oxygen within the outer layers of the ejecta.
University of Melbourne1, Australian Astronomical Observatory2, Swinburne University of Technology3, Las Cumbres Observatory Global Telescope Network4, University of California, Santa Barbara5, University of Oxford6, INAF7, Lawrence Berkeley National Laboratory8, Weizmann Institute of Science9, University of California, Berkeley10, Carnegie Institution for Science11, Tel Aviv University12
TL;DR: In this paper, the authors present an analysis of the Hubble diagram for 12 Type Ia supernovae (SNe Ia) observed in the near-infrared J and H bands.
Abstract: We present an analysis of the Hubble diagram for 12 Type Ia supernovae (SNe Ia) observed in the near-infrared J and H bands. We select SNe exclusively from the redshift range 0.03 < z < 0.09 to reduce uncertainties coming from peculiar velocities while remaining in a cosmologically well-understood region. All of the SNe in our sample exhibit no spectral or B-band light-curve peculiarities and lie in the B-band stretch range of 0.8-1.15. Our results suggest that SNe Ia observed in the near-infrared (NIR) are the best known standard candles. We fit previously determined NIR light-curve templates to new high-precision data to derive peak magnitudes and to determine the scatter about the Hubble line. Photometry of the 12 SNe is presented in the natural system. Using a standard cosmology of (H_0, Omega_m, Lambda) = (70,0.27,0.73) we find a median J-band absolute magnitude of M_J = -18.39 with a scatter of 0.116 and a median H-band absolute magnitude of M_H = -18.36 with a scatter of 0.085. The scatter in the H band is the smallest yet measured. We search for correlations between residuals in the J- and H-band Hubble diagrams and SN properties, such as SN colour, B-band stretch and the projected distance from host-galaxy centre. The only significant correlation is between the J-band Hubble residual and the J-H pseudo-colour. We also examine how the scatter changes when fewer points in the near-infrared are used to constrain the light curve. With a single point in the H band taken anywhere from 10 days before to 15 days after B-band maximum light and a prior on the date of H-band maximum set from the date of B-band maximum, we find that we can measure distances to an accuracy of 6%. The precision of SNe Ia in the NIR provides new opportunities for precision measurements of both the expansion history of the universe and peculiar velocities of nearby galaxies.
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