We present optical and near-infrared (NIR, $YJH$-band) observations of 42 Type Ia supernovae (SNe Ia) discovered by the untargeted intermediate Palomar Transient Factory (iPTF) survey. This new data-set covers a broad range of redshifts and host gala
xy stellar masses, compared to previous SN Ia efforts in the NIR. We construct a sample, using also literature data at optical and NIR wavelengths, to examine claimed correlations between the host stellar masses and the Hubble diagram residuals. The SN magnitudes are corrected for host galaxy extinction using either a global total-to-selective extinction ratio, $R_V$=2.0 for all SNe, or a best-fit $R_V$ for each SN individually. Unlike previous studies which were based on a narrower range in host stellar mass, we do not find evidence for a mass-step, between the color- and stretch-corrected peak $J$ and $H$ magnitudes for galaxies below and above $log(M_{*}/M_{odot}) = 10$. However, the mass-step remains significant ($3sigma$) at optical wavelengths ($g,r,i$) when using a global $R_V$, but vanishes when each SN is corrected using their individual best-fit $R_V$. Our study confirms the benefits of the NIR SN Ia distance estimates, as these are largely exempted from the empirical corrections dominating the systematic uncertainties in the optical.
In the second of two papers on the peculiar interacting transient AT 2016jbu, we present the bolometric lightcurve, identification and analysis of the progenitor candidate, as well as preliminary modelling to help elucidate the nature of this event.
We identify the progenitor candidate for AT 2016jbu in quiescence, and find it to be consistent with a $sim$20 M$_{odot}$ yellow hypergiant surrounded by a dusty circumstellar shell. We see evidence for significant photometric variability in the progenitor, as well as strong H$alpha$ emission consistent with pre-existing circumstellar material. The age of the resolved stellar population surrounding AT 2016jbu, as well as integral-field unit spectra of the region support a progenitor age of >16 Myr, again consistent with a progenitor mass of $sim$20 M$_{odot}$. Through a joint analysis of the velocity evolution of AT 2016jbu, and the photospheric radius inferred from the bolometric lightcurve, we find that the transient is consistent with two successive outbursts or explosions. The first outburst ejected a shell of material with velocity 650 km $s^{-1}$, while the second more energetic event ejected material at 4500 km $s^{-1}$. Whether the latter is the core-collapse of the progenitor remains uncertain, as the required ejecta mass is relatively low (few tenths of M$_{odot}$). We also place a restrictive upper limit on the ejected $^{56}$Ni mass of <0.016 M$_{odot}$. Using the BPASS code, we explore a wide range of possible progenitor systems, and find that the majority of these are in binaries, some of which are undergoing mass transfer or common envelope evolution immediately prior to explosion. Finally, we use the SNEC code to demonstrate that the low-energy explosion of some of these systems together with sufficient CSM can reproduce the overall morphology of the lightcurve of AT 2016jbu.
We present comprehensive, multi-wavelength observations of AT 2016jbu, an interacting transient. High cadence photometric coverage reveals that AT 2016jbu underwent significant photometric variability followed by two luminous events, the latter of wh
ich reached an absolute magnitude of M$_Vsim$-18.5 mag. This is similar to the transient SN 2009ip whose nature is still debated. Spectra are dominated by narrow emission lines and show a blue continuum during the peak of the second event. AT 2016jbu shows signatures of a complex, non-homogeneous circumstellar material (CSM). We see slowly evolving asymmetric hydrogen line profiles, with velocities of 500 km $s^{-1}$ seen in narrow emission features from a slow moving CSM, and up to 10,000 km $s^{-1}$ seen in broad absorption from some high velocity material. Similar velocities are seen in other SN 2009ip-like transients. Late-time spectra ($sim$+1 year) show a lack of forbidden emission lines expected from a core-collapse supernova during the nebular phase and are dominated by strong emission from H, He I and Ca II. Strong asymmetric emission features, a bumpy lightcurve, and continually evolving spectra suggest late time CSM interaction is inhibiting the emergence of any nebular features. We compare the evolution of H$alpha$ among SN 2009ip-like transients and find possible evidence for orientation angle effects. The light-curve evolution of AT 2016jbu suggests similar, but not identical, circumstellar environments to other SN 2009ip-like transients. In Paper II we continue the discussion of AT 2016jbu and SN 2009ip-like transients and using the data presented here, we focus on the local environment, the progenitor, and on modelling the transient itself.
We report the results from spectroscopic observations of the multiple images of the strongly lensed Type Ia supernova (SN Ia), iPTF16geu, obtained with ground based telescopes and the Hubble Space Telescope (HST). From a single epoch of slitless spec
troscopy with HST, we can resolve spectra of individual lensed supernova images for the first time. This allows us to perform an independent measurement of the time-delay between the two brightest images, $Delta t = 1.4 pm 5.0$ days, which is consistent with the time-delay measured from the light-curves. We also present measurements of narrow emission and absorption lines characterizing the interstellar medium in the host galaxy at z=0.4087, as well as in the foreground lensing galaxy at z=0.2163. We detect strong Na ID absorption in the host galaxy, indicating that iPTF16geu belongs to a subclass of SNe Ia displaying anomalously large Na ID column densities in comparison to the amount of dust extinction derived from their light curves. For the deflecting galaxy, we refine the measurement of the velocity dispersion, $sigma = 129 pm 4$ km/s, which significantly constrains the lens model. Since the time-delay between the SN images is negligible, we can use unresolved ground based spectroscopy, boosted by a factor ~70 from lensing magnification, to study the properties of a high-z SN Ia with unprecedented signal-to-noise ratio. The spectral properties of the supernova, such as pseudo-Equivalent widths of several absorption features and velocities of the Si II-line indicate that iPTF16geu, besides being lensed, is a normal SN Ia, indistinguishable from well-studied ones in the local universe, providing support for the use of SNe Ia in precision cosmology. We do not detect any significant deviations of the SN spectral energy distribution from microlensing of the SN photosphere by stars and compact objects in the lensing galaxy.
We report lensing magnifications, extinction, and time-delay estimates for the first resolved, multiply-imaged Type Ia supernova iPTF16geu, at $z = 0.409$, using $Hubble,Space,Telescope$ ($HST$) observations in combination with supporting ground-base
d data. Multi-band photometry of the resolved images provides unique information about the differential dimming due to dust in the lensing galaxy. Using $HST$ and Keck AO reference images taken after the SN faded, we obtain a total lensing magnification for iPTF16geu of $mu = 67.8^{+2.6}_{-2.9}$, accounting for extinction in the host and lensing galaxy. As expected from the symmetry of the system, we measure very short time-delays for the three fainter images with respect to the brightest one: -0.23 $pm$ 0.99, -1.43 $pm$ 0.74 and 1.36 $pm$ 1.07 days. Interestingly, we find large differences between the magnifications of the four supernova images, even after accounting for uncertainties in the extinction corrections: $Delta m_1 = -3.88^{+0.07}_{-0.06}$, $Delta m_2 = -2.99^{+0.09}_{-0.08}$, $Delta m_3 = -2.19^{+0.14}_{-0.15}$ and $Delta m_4 = -2.40^{+0.14}_{-0.12}$ mag, discrepant with model predictions suggesting similar image brightnesses. A possible explanation for the large differences is gravitational lensing by substructures, micro- or millilensing, in addition to the large scale lens causing the image separations. We find that the inferred magnification is insensitive to the assumptions about the dust properties in the host and lens galaxy.
The functions of the Low-Level Radio Frequency (LLRF) system at European Spallation Source (ESS) are implemented on different Field-Programmable Gate Array (FPGA) boards in a Micro Telecommunications Computing Architecture (MTCA) crate. Besides the a
lgorithm, code that provides access to the peripherals connected to the FPGA is necessary. In order to provide a common platform for the FPGA developments at ESS - the ESS FPGA Framework has been designed. The framework facilitates the integration of different algorithms on different FPGA boards. Three functions are provided by the framework: (1) Communication interfaces to peripherals, e.g. Analog-to-Digital Converters (ADCs) and on-board memory, (2) Upstream communication with the control system over Peripheral Component Interconnect Express (PCIe), and (3) Configuration of the on-board peripherals. To keep the framework easily extensible by Intellectual Property (IP) blocks and to enable seamless integration with the Xilinx design tools, the Advanced eXtensible Interface version 4 (AXI4) bus is the chosen communication interconnect. Furthermore, scripts automatize the building of the FPGA configuration, software components and the documentation. The LLRF control algorithms have been successfully integrated into the framework.
SN 2014J in M82 is the closest Type Ia supernova (SN Ia) in decades. The proximity allows for detailed studies of supernova physics and provides insights into the circumstellar and interstellar environment. In this work we analyze Spitzer mid-IR data
of SN 2014J in the 3.6 and 4.5 {mu}m wavelength range, together with several other nearby and well-studied SNe Ia. We compile the first composite mid-IR light-curve templates from our sample of SNe~Ia, spanning the range from before peak brightness well into the nebular phase. Our observations indicate that SNe Ia form a very homogeneous class of objects at these wavelengths. Using the low-reddening supernovae for comparison, we constrain possible thermal emission from circumstellar dust around the highly reddened SN 2014J. We also study SNe 2006X and 2007le, where the presence of matter in the circumstellar environment has been suggested. No significant mid-IR excess is detected, allowing us to place upper limits on the amount of pre-existing dust in the circumstellar environment. For SN 2014J, $M_{dust} < 10^{-5}$ M$_{odot}$ within $r_{dust} sim 10^{17}$ cm, which is insufficient to account for the observed extinction. Similar limits are obtained for SNe 2006X and 2007le.
The wavelength-dependence of the extinction of Type Ia SN2014J in the nearby galaxy M82 has been measured using UV to near-IR photometry obtained with the Hubble Space Telescope, the Nordic Optical Telescope, and the Mount Abu Infrared Telescope. Thi
s is the first time that the reddening of a SN Ia is characterized over the full wavelength range of $0.2$-$2$ microns. A total-to-selective extinction, $R_Vgeq3.1$, is ruled out with high significance. The best fit at maximum using a Galactic type extinction law yields $R_V = 1.4pm0.1$. The observed reddening of SN2014J is also compatible with a power-law extinction, $A_{lambda}/A_V = left( {lambda}/ {lambda_V} right)^{p}$ as expected from multiple scattering of light, with $p=-2.1pm0.1$. After correction for differences in reddening, SN2014J appears to be very similar to SN2011fe over the 14 broad-band filter light curves used in our study.
We report measurements of macroscopic resonant tunneling between the two lowest energy states of a pair of magnetically coupled rf-SQUID flux qubits. This technique provides a direct means of observing two-qubit dynamics and a probe of the environmen
t coupled to the pair of qubits. Measurements of the tunneling rate as a function of qubit flux bias show a Gaussian line shape that is well matched to theoretical predictions. Moreover, the peak widths indicate that each qubit is coupled to a local environment whose fluctuations are uncorrelated with that of the other qubit.
A novel rf-SQUID flux qubit that is robust against fabrication variations in Josephson junction critical currents and device inductance has been implemented. Measurements of the persistent current and of the tunneling energy between the two lowest ly
ing states, both in the coherent and incoherent regime, are presented. These experimental results are shown to be in agreement with predictions of a quantum mechanical Hamiltonian whose parameters were independently calibrated, thus justifying the identification of this device as a flux qubit. In addition, measurements of the flux and critical current noise spectral densities are presented that indicate that these devices with Nb wiring are comparable to the best Al wiring rf-SQUIDs reported in the literature thusfar, with a $1/f$ flux noise spectral density at $1 $Hz of $1.3^{+0.7}_{-0.5} muPhi_0/sqrt{text{Hz}}$. An explicit formula for converting the observed flux noise spectral density into a free induction decay time for a flux qubit biased to its optimal point and operated in the energy eigenbasis is presented.
