Context. PSR B1259−63/LS2883 is a binary system where a 48 ms pulsar orbits a massive Be star with a highly eccentric orbit (e = 0.87) with a period of 3.4 years. The system exhibits variable, ...non-thermal radiation visible from radio to very high energies (VHE) around periastron passage. This radiation is thought to come from particles accelerated in the shock region between the pulsar wind (PW) and stellar outflows. Aims. The consistency of the HESS data with the inverse Compton (IC) scenario is studied in the context of dominant orbital-phase-dependent adiabatic losses, and the dependence of the observed TeV flux with the separation distance analysed. Methods. Model calculations based on IC scattering of shock accelerated PW electrons and UV photons are performed. Different non-radiative cooling profiles are suggested for the primary particle population to account for the variable TeV flux. Results. The TeV fluxes obtained with HESS in the years 2004 and 2007 only seem to depend on the binary separation. The results hint at a peculiar non-radiative cooling profile around periastron dominating the VHE emission in PSR B1259−63. The location of the stellar disc derived from this non-radiative cooling profile is in good agreement with what is inferred from radio observations.
We present 32 epochs of optical (3300−9700 Å) spectrophotometric observations of the nearby quintessential “normal” type Ia supernova (SN Ia) SN 2011fe in the galaxy M101, extending from −15 to +97 d ...with respect to B-band maximum, obtained by the Nearby Supernova Factory collaboration. SN 2011fe is the closest (μ = 29.04) and brightest (Bmax = 9.94 mag) SN Ia observed since the advent of modern large scale programs for the intensive periodic followup of supernovae. Both synthetic light curve measurements and spectral feature analysis attest to the normality of SN 2011fe. There is very little evidence for reddening in its host galaxy. The homogeneous calibration, intensive time sampling, and high signal-to-noise ratio of the data set make it unique. Thus it is ideal for studying the physics of SN Ia explosions in detail, and for furthering the use of SNe Ia as standardizable candles for cosmology. Several such applications are shown, from the creation of a bolometric light curve and measurement of the 56Ni mass, to the simulation ofdetection thresholds for unburned carbon, direct comparisons with other SNe Ia, and existing spectral templates.
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Near-infrared chemical imaging (NIR-CI) with high-speed cameras based on the push-broom acquisition principle is a rapidly-evolving and can be used for a variety of purposes, from ...classification (and sorting) of products to mapping spatial distribution of materials. The present study examined if NIR-CI is suitable for tablet manufacturing. To that end, the tablets were introduced into the CI system via a flat belt conveyor. A formulation, which consisted of 4wt.%–6wt.% caffeine, 5wt.% crospovidone as a disintegrant, 88wt.%–90wt.% lactose as a filler and 1wt.% magnesium stearate as a lubricator, was tableted at compression forces ranging from 5kN to 30kN. The intra- and inter-tablet homogeneity of caffeine and the tablet’s hardness were analyzed via NIR‐CI. For the homogeneity evaluation, two methods were applied: standard deviation (SD) and distributional homogeneity index (DHI). The results showed that the SD of caffeine in a single tablet increased with an increase in the caffeine content. This was attributed to natural variations in a binary mixture of caffeine and excipients. Overall, the chosen NIR-CI setup has strong potential to be transferred to the production scale to monitor all tablets in a production stream.
We examine the relationship between Type Ia supernova (SN Ia) Hubble residuals and the properties of their host galaxies using a sample of 115 SNe Ia from the Nearby Supernova Factory. We use host ...galaxy stellar masses and specific star formation rates fitted from photometry for all hosts, as well as gas-phase metallicities for a subset of 69 star-forming (non-active galactic nucleus) hosts, to show that the SN Ia Hubble residuals correlate with each of these host properties. With these data we find new evidence for a correlation between SN Ia intrinsic color and host metallicity. When we combine our data with those of other published SN Ia surveys, we find the difference between mean SN Ia brightnesses in low- and high-mass hosts is 0.077 + or - 0.014 mag. When viewed in narrow (0.2 dex) bins of host stellar mass, the data reveal apparent plateaus of Hubble residuals at high and low host masses with a rapid transition over a short mass range (9.8 < or =, slant log(Mlow */M sub(middot in circle)) < or =, slant 10.4). Although metallicity has been a favored interpretation for the origin of the Hubble residual trend with host mass, we illustrate how dust in star-forming galaxies and mean SN Ia progenitor age both evolve along the galaxy mass sequence, thereby presenting equally viable explanations for some or all of the observed SN Ia host bias.
Context. Our Local Group of galaxies appears to be moving relative to the cosmic microwave background with the source of the peculiar motion still uncertain. While in the past this has been studied ...mostly using galaxies as distance indicators, the weight of Type Ia supernovae (SNe Ia) has increased recently with the continuously improving statistics of available low-redshift supernovae. Aims. We measured the bulk flow in the nearby universe (0.015 < z < 0.1) using 117 SNe Ia observed by the Nearby Supernova Factory, as well as the Union2 compilation of SN Ia data already in the literature. Methods. The bulk flow velocity was determined from SN data binned in redshift shells by including a coherent motion (dipole) in a cosmological fit. Additionally, a method of spatially smoothing the Hubble residuals was used to verify the results of the dipole fit. To constrain the location and mass of a potential mass concentration (e.g., the Shapley supercluster) responsible for the peculiar motion, we fit a Hubble law modified by adding an additional mass concentration. Results. The analysis shows a bulk flow that is consistent with the direction of the CMB dipole up to z ~ 0.06, thereby doubling the volume over which conventional distance measures are sensitive to a bulk flow. We see no significant turnover behind the center of the Shapley supercluster. A simple attractor model in the proximity of the Shapley supercluster is only marginally consistent with our data, suggesting the need for another, more distant source. In the redshift shell 0.06 < z < 0.1, we constrain the bulk flow velocity to ≤240 km s-1 (68% confidence level) for the direction of the CMB dipole, in contradiction to recent claims of the existence of a large-amplitude dark flow.
We present a new atmospheric extinction curve for Mauna Kea spanning 3200–9700 Å. It is the most comprehensive to date, being based on some 4285 standard star spectra obtained on 478 nights spread ...over a period of 7 years obtained by the Nearby SuperNova Factory using the SuperNova Integral Field Spectrograph. This mean curve and its dispersion can be used as an aid in calibrating spectroscopic or imaging data from Mauna Kea, and in estimating the calibration uncertainty associated with the use of a mean extinction curve. Our method for decomposing the extinction curve into physical components, and the ability to determine the chromatic portion of the extinction even on cloudy nights, is described and verified over the wide range of conditions sampled by our large dataset. We demonstrate good agreement with atmospheric science data obtain at nearby Mauna Loa Observatory, and with previously published measurements of the extinction above Mauna Kea.
Type Ia Supernova Carbon Footprints Thomas, R. C; Aldering, G; Antilogus, P ...
The Astrophysical journal,
12/2011, Letnik:
743, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We present convincing evidence of unburned carbon at photospheric velocities in new observations of five Type Ia supernovae (SNe Ia) obtained by the Nearby Supernova Factory. These SNe are identified ...by examining 346 spectra from 124 SNe obtained before +2.5 days relative to maximum. Detections are based on the presence of relatively strong C II lambda 6580 absorption 'notches' in multiple spectra of each SN, aided by automated fitting with the SYNAPPS code. Four of the five SNe in question are otherwise spectroscopically unremarkable, with ions and ejection velocities typical of SNe Ia, but spectra of the fifth exhibit high-velocity (v > 2,000 km s super(-1)) Si II and Ca II features. On the other hand, the light curve properties are preferentially grouped, strongly suggesting a connection between carbon-positivity and broadband light curve/color behavior: three of the five have relatively narrow light curves but also blue colors and a fourth may be a dust-reddened member of this family. Accounting for signal to noise and phase, we estimate that 22 super(+)10 sub(-)6% of SNe Ia exhibit spectroscopic C II signatures as late as -5 days with respect to maximum. We place these new objects in the context of previously recognized carbon-positive SNe Ia and consider reasonable scenarios seeking to explain a physical connection between light curve properties and the presence of photospheric carbon. We also examine the detailed evolution of the detected carbon signatures and the surrounding wavelength regions to shed light on the distribution of carbon in the ejecta. Our ability to reconstruct the C II lambda 6580 feature in detail under the assumption of purely spherical symmetry casts doubt on a 'carbon blobs' hypothesis, but does not rule out all asymmetric models. A low volume filling factor for carbon, combined with line-of-sight effects, seems unlikely to explain the scarcity of detected carbon in SNe Ia by itself.
We present Keck LRIS spectroscopy and g-band photometry of the metal-poor, low-luminosity host galaxy of the super-Chandrasekhar-mass Type Ia supernova SN 2007if. Deep imaging of the host reveals its ...apparent magnitude to be mg = 23.15 ? 0.06, which at the spectroscopically measured redshift of z helio = 0.07450 ? 0.00015 corresponds to an absolute magnitude of Mg = --14.45 ? 0.06. Galaxy g -- r color constrains the mass-to-light ratio, giving a host stellar mass estimate of log(M */M ) = 7.32 ? 0.17. Balmer absorption in the stellar continuum, along with the strength of the 4000 A break, constrains the age of the dominant starburst in the galaxy to be t burst = 123+165 --77 Myr, corresponding to a main-sequence turnoff mass of M/M = 4.6+2.6 --1.4. Using the R 23 method of calculating metallicity from the fluxes of strong emission lines, we determine the host oxygen abundance to be 12 + log(O/H)KK04 = 8.01 ? 0.09, significantly lower than any previously reported spectroscopically measured Type Ia supernova host galaxy metallicity. Our data show that SN 2007if is very likely to have originated from a young, metal-poor progenitor.
Context. PSRB125963/LS2883 is a binary system where a 48 ms pulsar orbits a massive Be star with a highly eccentric orbit (e = 0.87) with a period of 3.4 years. The system exhibits variable, ...non-thermal radiation visible from radio to very high energies (VHE) around periastron passage. This radiation is thought to come from particles accelerated in the shock region between the pulsar wind (PW) and stellar outflows. Aims. The consistency of the HESS data with the inverse Compton (IC) scenario is studied in the context of dominant orbital-phase-dependent adiabatic losses, and the dependence of the observed TeV flux with the separation distance analysed. Methods. Model calculations based on IC scattering of shock accelerated PW electrons and UV photons are performed. Different non-radiative cooling profiles are suggested for the primary particle population to account for the variable TeV flux. Results. The TeV fluxes obtained with HESS in the years 2004 and 2007 only seem to depend on the binary separation. The results hint at a peculiar non-radiative cooling profile around periastron dominating the VHE emission in PSRB125963. The location of the stellar disc derived from this non-radiative cooling profile is in good agreement with what is inferred from radio observations.
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