938 research outputs found
The bumpy light curve of supernova iPTF13z
A Type IIn supernova (SN) is dominated by the interaction of SN ejecta with
the circumstellar medium (CSM). Some SNe IIn (e.g., SN 2006jd) have episodes of
re-brightening ("bumps") in their light curves. We present iPTF13z, a SN IIn
discovered by the intermediate Palomar Transient Factory (iPTF) and
characterised by several bumps in its light curve. We analyse this peculiar
behaviour trying to infer the properties of the CSM and of the SN explosion, as
well as the nature of its progenitor star. We obtained multi-band optical
photometry for over 1000 days after discovery with the P48 and P60 telescopes
at Palomar Observatory. We obtained low-resolution optical spectra in the same
period. We did an archival search for progenitor outbursts. We analyse our
photometry and spectra, and compare iPTF13z to other SNe IIn. A simple
analytical model is used to estimate properties of the CSM. iPTF13z was a SN
IIn showing a light curve with five bumps during its decline phase. The bumps
had amplitudes between 0.4 and 0.9 mag and durations between 20 and 120 days.
The most prominent bumps appeared in all our different optical bands. The
spectra showed typical SN IIn characteristics, with emission lines of H
(with broad component FWHM ~ and narrow
component FWHM ~) and He I, but also with Fe II, Ca II,
Na I D and H P-Cygni profiles (with velocities of ~ ). A pre-explosion outburst was identified lasting days,
with mag around 210 days before discovery. Large, variable
progenitor mass-loss rates (~> 0.01 ) and CSM densities
(~> 10 g cm) are derived. We suggest that the light curve bumps
of iPTF13z arose from SN ejecta interacting with denser regions in the CSM,
possibly produced by the eruptions of a luminous blue variable star.Comment: Version 2: Update to match published paper. 21 pages, 14 figures,
abstract abridged to comply with arXiv length limit. In version 1 of the
paper on arXiv, Table 3 had some erroneous entries. Table 3 is now corrected
and available via VizieR. Version 1 comment: Accepted for publication in
Astronomy & Astrophysics (24 pages, 14 figures, abstract abridged by 20 % not
to exceed the arXiv length limit
CoWBP capping barrier layer for sub 90 nm Cu interconnects
Abstract Electroless cobalt films have been obtained by deposition using a plating bath containing two reducing agents: dimethylamineborane (DMAB) and sodium hypophosphite. This formulation allows spontaneous activation on copper followed by auto catalytic electroless plating. CoWBP and CoBP films are proposed as diffusion barriers and encapsulation layers, for copper lines and via contacts for ULSI interconnect applications. The crystalline structure, chemical composition and oxidation states of the elements were studied, as well as the electrical resistivity, topography and morphology of the films. The film composition was characterized as a function of the solution composition; the barrier properties of the films were tested and an oxidation resistance study was conducted. The films were characterized and the results show that they can be applied as capping layers for ULSI copper metallization
SN 2009ip: Constraints on the Progenitor Mass-loss Rate
Some supernovae (SNe) show evidence for mass-loss events taking place prior to their explosions. Measuring their pre-outburst mass-loss rates provides essential information regarding the mechanisms that are responsible for these events. Here we present XMM-Newton and Swift X-ray observations taken after the latest, and presumably the final, outburst of SN 2009ip. We use these observations as well as new near-infrared and visible-light spectra and published radio and visible-light observations to put six independent order-of-magnitude constraints on the mass-loss rate of the SN progenitor prior to the explosion. Our methods utilize the X-ray luminosity, the bound-free absorption, the Hα luminosity, the SN rise time, free-free absorption, and the bolometric luminosity of the outburst detected prior to the explosion. Assuming spherical mass loss with a wind-density profile, we estimate that the effective mass-loss rate from the progenitor was between 10^(–3) and 10^(–2) M_☉ yr^(–1), over a few years prior to the explosion, with a velocity of ~10^3 km s^(–1). This mass-loss rate corresponds to a total circumstellar matter (CSM) mass of ~0.04 M_☉, within 6 × 10^(15) cm of the SN. We note that the mass-loss rate estimate based on the Hα luminosity is higher by an order of magnitude. This can be explained if the narrow-line Hα component is generated at radii larger than the shock radius, or if the CSM has an aspherical geometry. We discuss simple geometries which are consistent with our results
On the Nature of the Apparent Ring Galaxy SDSS J075234.33+292049.8
(abridged) An object classified as a galaxy in on-line data bases and
revealed on sky survey images as a distant ring galaxy is a rare case of polar
ring galaxy where the ring is only slightly inclined to the equatorial plane of
the central body. SDSS imaging indicates that the diameter of the ring is about
36 kpc. The SDSS data was combined with long-slit spectroscopic observations
and with Fabry-Perot Interferometer H-beta mapping obtained at the Russian
Academy of Sciences 6-m telescope. We derived the complex morphologies of this
presumed ring galaxy from a combination of SDSS images and from the kinematical
behaviour of the central body and of the ring, and determined the stellar
population compositions of the two components from SDSS colours, spectroscopy,
and evolutionary stellar synthesis models. The ring metallicity is slightly
under-abundant. The total luminosity and the total mass of the system are not
extreme, but the rather high M/L~20 indicates the presence of large amounts of
dark matter. Two alternative explanations of this object are proposed (1) a
ring formed by two semi-circular and tight spiral arms at the end of a central
bar with a warp or precession of the ring material. The object could,
therefore, be explained as an extreme SBa(R) galaxy, or (2) a Polar Ring Galaxy
where the inner object is an S0 and the ring is significantly more luminous
than the central object. The compound object would then be similar to the NGC
4650A galaxy, being a rare object with a polar component only modestly inclined
to the equatorial plane of the central body. Arguments for (and against) both
explanations are given and discussed, with the second alternative being more
acceptable.Comment: 16 pages, 11 figures, MNRAS in pres
A multi-wavelength investigation of the radio-loud supernova PTF11qcj and its circumstellar environment
We present the discovery, classification, and extensive panchromatic (from
radio to X-ray) follow-up observations of PTF11qcj, a supernova discovered by
the Palomar Transient Factory. PTF11qcj is located at a distance of dL ~ 124
Mpc. Our observations with the Karl G. Jansky Very Large Array show that this
event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to
that of the famous gamma-ray-burst-associated supernova 1998bw (L_{5GHz} ~
10^{29} erg/s/Hz). PTF11qcj is also detected in X-rays with the Chandra
observatory, and in the infrared band with Spitzer. Our multi-wavelength
analysis probes the supernova interaction with circumstellar material. The
radio observations suggest a progenitor mass-loss rate of ~10^{-4} Msun/yr x
(v_w/1000 km/s), and a velocity of ~(0.3-0.5)c for the fastest moving ejecta
(at ~10d after explosion). However, these estimates are derived assuming the
simplest model of supernova ejecta interacting with a smooth circumstellar
material characterized by radial power-law density profile, and do not account
for possible inhomogeneities in the medium and asphericity of the explosion.
The radio light curve shows deviations from such a simple model, as well as a
re-brightening at late times. The X-ray flux from PTF11qcj is compatible with
the high-frequency extrapolation of the radio synchrotron emission (within the
large uncertainties). An IR light echo from pre-existing dust is in agreement
with our infrared data. Our analysis of pre-explosion data from the Palomar
Transient Factory suggests that a precursor eruption of absolute magnitude M_r
~ -13 mag may have occurred ~ 2.5 yr prior to the supernova explosion. Based on
our panchromatic follow-up campaign, we conclude that PTF11qcj fits the
expectations from the explosion of a Wolf-Rayet star. Precursor eruptions may
be a feature characterizing the final pre-explosion evolution of such stars.Comment: 43 pages, 15 figures; this version matches the one published in ApJ
(includes minor changes that address the Referee's comments.
Interaction-powered supernovae: Rise-time vs. peak-luminosity correlation and the shock-breakout velocity
Interaction of supernova (SN) ejecta with the optically thick circumstellar
medium (CSM) of a progenitor star can result in a bright, long-lived shock
breakout event. Candidates for such SNe include Type IIn and superluminous SNe.
If some of these SNe are powered by interaction, then there should be a
relation between their peak luminosity, bolometric light-curve rise time, and
shock-breakout velocity. Given that the shock velocity during shock breakout is
not measured, we expect a correlation, with a significant spread, between the
rise time and the peak luminosity of these SNe. Here, we present a sample of 15
SNe IIn for which we have good constraints on their rise time and peak
luminosity from observations obtained using the Palomar Transient Factory. We
report on a possible correlation between the R-band rise time and peak
luminosity of these SNe, with a false-alarm probability of 3%. Assuming that
these SNe are powered by interaction, combining these observables and theory
allows us to deduce lower limits on the shock-breakout velocity. The lower
limits on the shock velocity we find are consistent with what is expected for
SNe (i.e., ~10^4 km/s). This supports the suggestion that the early-time light
curves of SNe IIn are caused by shock breakout in a dense CSM. We note that
such a correlation can arise from other physical mechanisms. Performing such a
test on other classes of SNe (e.g., superluminous SNe) can be used to rule out
the interaction model for a class of events.Comment: Accepted to ApJ, 6 page
Constraints on Planetary Companions in the Magnification A=256 Microlensing Event: OGLE-2003-BLG-423
We develop a new method of modeling microlensing events based on a Monte
Carlo simulation that incorporates both a Galactic model and the constraints
imposed by the observed characteristics of the event. The method provides an
unbiased way to analyze the event especially when parameters are poorly
constrained by the observed lightcurve. We apply this method to search for
planetary companions of the lens in OGLE-2003-BLG-423, whose maximum
magnification A_max=256+-43 (or A_max=400+-115 from the lightcurve data alone)
is the highest among single-lens events ever recorded. The method permits us,
for the first time, to place constraints directly in the
planet-mass/projected-physical-separation plane rather than in the
mass-ratio/Einstein-radius plane as was done previously. For example,
Jupiter-mass companions of main-sequence stars at 2.5 AU are excluded with 80%
efficiency.Comment: 10 pages, 7 figures, accepted for publication in The Astrophysical
Journa
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