163 research outputs found
The 2-Year Checkup on 10 SNe IIn Discovered by Spitzer to Exhibit Late-Time (is greater than 100 Day) IR Emission
Two years ago, a warm Spitzer survey of sixty-eight SNe IIn identified between the years 1998-2008 discovered 10 events with unreported late-time infrared (IR) excesses, in some cases more than 5 years post-explosion. These data nearly double the database of existing mid-IR observations of SNe IIn and offer important clues regarding the SN circumstellar
An outburst from a massive star 40 days before a supernova explosion
Various lines of evidence suggest that very massive stars experience extreme
mass-loss episodes shortly before they explode as a supernova. Interestingly,
several models predict such pre-explosion outbursts. Establishing a causal
connection between these mass-loss episodes and the final supernova explosion
will provide a novel way to study pre-supernova massive-star evolution. Here we
report on observations of a remarkable mass-loss event detected 40 days prior
to the explosion of the Type IIn supernova SN 2010mc (PTF 10tel). Our
photometric and spectroscopic data suggest that this event is a result of an
energetic outburst, radiating at least 6x10^47 erg of energy, and releasing
about 0.01 Solar mass at typical velocities of 2000 km/s. We show that the
temporal proximity of the mass-loss outburst and the supernova explosion
implies a causal connection between them. Moreover, we find that the outburst
luminosity and velocity are consistent with the predictions of the wave-driven
pulsation model and disfavor alternative suggestions.Comment: Nature 494, 65, including supplementary informatio
Supernovae in the Subaru Deep Field: the rate and delay-time distribution of Type Ia supernovae out to redshift 2
The Type Ia supernova (SN Ia) rate, when compared to the cosmic star formation history (SFH), can be used to derive the delay-time distribution (DTD; the hypothetical SN Ia rate versus time following a brief burst of star formation) of SNe Ia, which can distinguish among progenitor models. We present the results of a supernova (SN) survey in the Subaru Deep Field (SDF). Over a period of 3 years, we have observed the SDF on four independent epochs with Suprime-Cam on the Subaru 8.2-m telescope, with two nights of exposure per epoch, in the R, i′and z′ bands. We have discovered 150 SNe out to redshift z≈ 2. Using 11 photometric bands from the observer-frame far-ultraviolet to the near-infrared, we derive photometric redshifts for the SN host galaxies (for 24 we also have spectroscopic redshifts). This information is combined with the SN photometry to determine the type and redshift distribution of the SN sample. Our final sample includes 28 SNe Ia in the range 1.0 1, most of the events found in this range are likely SNe Ia. Our SN Ia rate measurements are consistent with those derived from the Hubble Space Telescope (HST) Great Observatories Origins Deep Survey (GOODS) sample, but the overall uncertainty of our 1.5 2
Interaction Between The Broad-lined Type Ic Supernova 2012ap and Carriers of Diffuse Interstellar Bands
The diffuse interstellar bands (DIBs) are absorption features observed in
optical and near-infrared spectra that are thought to be associated with
carbon-rich polyatomic molecules in interstellar gas. However, because the
central wavelengths of these bands do not correspond with electronic
transitions of any known atomic or molecular species, their nature has remained
uncertain since their discovery almost a century ago. Here we report on
unusually strong DIBs in optical spectra of the broad-lined Type Ic supernova
SN 2012ap that exhibit changes in equivalent width over short (~30 days)
timescales. The 4428 and 6283 Angstrom DIB features get weaker with time,
whereas the 5780 Angstrom feature shows a marginal increase. These nonuniform
changes suggest that the supernova is interacting with a nearby source of the
DIBs and that the DIB carriers possess high ionization potentials, such as
small cations or charged fullerenes. We conclude that moderate-resolution
spectra of supernovae with DIB absorptions obtained within weeks of outburst
could reveal unique information about the mass-loss environment of their
progenitor systems and provide new constraints on the properties of DIB
carriers.Comment: 6 pages, 3 figures, accepted for publication in ApJ
SN Refsdal: Classification as a Luminous and Blue SN 1987A-like Type II Supernova
We have acquired Hubble Space Telescope (HST) and Very Large Telescope
near-infrared spectra and images of supernova (SN) Refsdal after its discovery
as an Einstein cross in Fall 2014. The HST light curve of SN Refsdal matches
the distinctive, slowly rising light curves of SN 1987A-like supernovae (SNe),
and we find strong evidence for a broad H-alpha P-Cygni profile in the HST
grism spectrum at the redshift (z = 1.49) of the spiral host galaxy. SNe IIn,
powered by circumstellar interaction, could provide a good match to the light
curve of SN Refsdal, but the spectrum of a SN IIn would not show broad and
strong H-alpha absorption. From the grism spectrum, we measure an H-alpha
expansion velocity consistent with those of SN 1987A-like SNe at a similar
phase. The luminosity, evolution, and Gaussian profile of the H-alpha emission
of the WFC3 and X-shooter spectra, separated by ~2.5 months in the rest frame,
provide additional evidence that supports the SN 1987A-like classification. In
comparison with other examples of SN 1987A-like SNe, SN Refsdal has a blue B-V
color and a high luminosity for the assumed range of potential magnifications.
If SN Refsdal can be modeled as a scaled version of SN 1987A, we estimate it
would have an ejecta mass of 20+-5 solar masses. The evolution of the light
curve at late times will provide additional evidence about the potential
existence of any substantial circumstellar material (CSM). Using MOSFIRE and
X-shooter spectra, we estimate a subsolar host-galaxy metallicity (8.3+-0.1 dex
and <8.4 dex, respectively) near the explosion site.Comment: Submitted to ApJ; 26 page
High-Velocity Line Forming Regions in the Type Ia Supernova 2009ig
We report measurements and analysis of high-velocity (> 20,000 km/s) and
photospheric absorption features in a series of spectra of the Type Ia
supernova (SN) 2009ig obtained between -14d and +13d with respect to the time
of maximum B-band luminosity. We identify lines of Si II, Si III, S II, Ca II
and Fe II that produce both high-velocity (HVF) and photospheric-velocity (PVF)
absorption features. SN 2009ig is unusual for the large number of lines with
detectable HVF in the spectra, but the light-curve parameters correspond to a
slightly overluminous but unexceptional SN Ia (M_B = -19.46 mag and Delta_m15
(B) = 0.90 mag). Similarly, the Si II lambda_6355 velocity at the time of B-max
is greater than "normal" for a SN Ia, but it is not extreme (v_Si = 13,400
km/s). The -14d and -13d spectra clearly resolve HVF from Si II lambda_6355 as
separate absorptions from a detached line forming region. At these very early
phases, detached HVF are prevalent in all lines. From -12d to -6d, HVF and PVF
are detected simultaneously, and the two line forming regions maintain a
constant separation of about 8,000 km/s. After -6d all absorption features are
PVF. The observations of SN 2009ig provide a complete picture of the transition
from HVF to PVF. Most SN Ia show evidence for HVF from multiple lines in
spectra obtained before -10d, and we compare the spectra of SN 2009ig to
observations of other SN. We show that each of the unusual line profiles for Si
II lambda_6355 found in early-time spectra of SN Ia correlate to a specific
phase in a common development sequence from HVF to PVF.Comment: 19 pages, 11figures, 4 tables, submitted to Ap
A High-Resolution Spectroscopic Search for the Remaining Donor for Tycho's Supernova
In this paper, we report on our analysis using Hubble Space Telescope
astrometry and Keck-I HIRES spectroscopy of the central six stars of Tycho's
supernova remnant (SN 1572). With these data, we measured the proper motions,
radial velocities, rotational velocities, and chemical abundances of these
objects. Regarding the chemical abundances, we do not confirm the unusu- ally
high [Ni/Fe] ratio previously reported for Tycho-G. Rather, we find that for
all metrics in all stars, none exhibit the characteristics expected from
traditional SN Ia single-degenerate-scenario calculations. The only possible
exception is Tycho-B, a rare, metal-poor A-type star; however, we are unable to
find a suitable scenario for it. Thus, we suggest that SN 1572 cannot be
explained by the standard single-degenerate model.Comment: 34 pages, 11 Figures, revised and resubmitted to Ap
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