53 research outputs found
Grouping Normal Type Ia Supernovae by UV to Optical Color Differences
Observations of many SNe Ia with the UVOT instrument on the Swift satellite
has revealed that there exists order to the differences in the UV-OPT colors of
normal SNe. We examine UV-OPT color curves for 25 SNe Ia, dividing them into 4
groups, finding that ~1/3 of these SNe Ia have bluer UV-OPT colors than the
larger group, with these "NUV-blue" SNe Ia 0.4 mag bluer than the "NUV-red" SNe
Ia in u-v. Another group of events feature colors similar to NUV-red SNe Ia in
the u-v to uvw1-v colors, but similar to the NUV-blue SNe Ia in the uvm2-v
color. We name these events "MUV-blue". The last group initially has colors
similar to NUV-red SNe Ia, but with color curves that feature more modest
changes than the larger NUV-red group. These "irregular" events are comprised
of all the NUV-red events with the broadest optical peaks, which leads us to
consider this minor group a subset of the NUV-red group. When so separated and
the accounting is made for the rapid time evolution of the UV-OPT colors, we
find that the scatter in two NUV-OPT colors, u-v & uvw1-v, is at the level of
the scatter in b-v. This finding is promising for extending the cosmological
utilization of SNe Ia into the NUV. We generate spectrophotometry of SNe Ia
that have been observed with HST and argue that there is a fundamental spectral
difference in the 2900-3500A wavelength range, a range suggested to be
dominated by absorption from iron-peak elements. The NUV-blue SNe Ia feature
less NUV absorption than the NUV-red SNe Ia. We show that all the NUV-blue SNe
Ia in this sample have also featured evidence of unburned carbon in optical
spectra, whereas only one NUV-red SN Ia features that absorption line. Every
NUV-blue event also exhibits a low gradient of the SiII 6355A absorption
feature, but many NUV-red events also exhibit a low gradient, perhaps
suggestive that NUV-blue events are a subset of the larger LVG group.Comment: Accepted to the Astrophysical Journal Updated version: Sept 16, 201
Toward porting Astrophysics Visual Analytics Services to the European Open Science Cloud
The European Open Science Cloud (EOSC) aims to create a federated environment
for hosting and processing research data to support science in all disciplines
without geographical boundaries, such that data, software, methods and
publications can be shared as part of an Open Science community of practice.
This work presents the ongoing activities related to the implementation of
visual analytics services, integrated into EOSC, towards addressing the diverse
astrophysics user communities needs. These services rely on visualisation to
manage the data life cycle process under FAIR principles, integrating data
processing for imaging and multidimensional map creation and mosaicing, and
applying machine learning techniques for detection of structures in large scale
multidimensional maps
Auroral radio emission from low-mass stars
It is now a well-established fact that also very low mass stars harbor planetary systems. These stars represent the large majority of our nearby stars but, despite their proximity, their low optical luminosity makes it difficult to apply the usual methods for exoplanet search. An effective probe for the environment of these stars is the auroral radio emission. This kind of emission is well understood for those stars whose magnetic field can be approximated as a dipole. In these cases the radio emission has a peculiar signature in time and in polarization. The presence of a planet nearby the star triggers or perturbs this emission leading to a predictable modulation. We present the case study of the ultra-cool dwarf TVLM 513-46546, for which we take advantage of VLA observations at 4.9 and 8.4 GHz. We reproduce the cyclic circularly-polarized pulses of the star using a 3D model of the auroral radio emission from the stellar magnetosphere. To take into account the possible deviation from the dipolar symmetry, the model simulates a magnetosphere shaped like an offset-dipole. To reproduce the timing and pattern of the observed pulses we explored the space of parameters controlling the auroral beaming pattern and the magnetosphere geometry. Our model explains the observed anomalies of the radio emission at 8.4 GHz as a possible interaction of the star with an external body, like in the case of the interaction between Jupiter and Io
Supernova 2010ev: A reddened high velocity gradient type Ia supernova
Aims. We present and study the spectroscopic and photometric evolution of the
type Ia supernova (SN Ia) 2010ev. Methods. We obtain and analyze multi-band
optical light curves and optical-near-infrared spectroscopy at low and medium
resolution spanning from -7 days to +300 days from the B-band maximum. Results.
A photometric analysis shows that SN 2010ev is a SN Ia of normal brightness
with a light curve shape of and a stretch s =
suffering significant reddening. From photometric and
spectroscopic analysis, we deduce a color excess of
and a reddening law of . Spectroscopically, SN 2010ev
belongs to the broad-line SN Ia group, showing stronger than average Si II
{\lambda}6355 absorption features. We also find that SN 2010ev is a
high-velocity gradient SN, with a value of km s d.
The photometric and spectral comparison with other supernovae shows that SN
2010ev has similar colors and velocities to SN 2002bo and SN 2002dj. The
analysis of the nebular spectra indicates that the [Fe II] {\lambda}7155 and
[Ni II] {\lambda}7378 lines are redshifted, as expected for a high velocity
gradient supernova. All these common intrinsic and extrinsic properties of the
high velocity gradient (HVG) group are different from the low velocity gradient
(LVG) normal SN Ia population and suggest significant variety in SN Ia
explosions.Comment: 16 pages, 13 figures, 7 tables. Accepted to A&
Signatures of an eruptive phase before the explosion of the peculiar core-collapse SN 2013gc
We present photometric and spectroscopic analysis of the peculiar
core-collapse SN 2013gc, spanning seven years of observations. The light curve
shows an early maximum followed by a fast decline and a phase of almost
constant luminosity. At +200 days from maximum, a brightening of 1 mag is
observed in all bands, followed by a steep linear luminosity decline after +300
d. In archival images taken between 1.5 and 2.5 years before the explosion, a
weak source is visible at the supernova location, with mag20. The
early supernova spectra show Balmer lines, with a narrow (560 km
s) P-Cygni absorption superimposed on a broad (3400 km s)
component, typical of type IIn events. Through a comparison of colour curves,
absolute light curves and spectra of SN 2013gc with a sample of supernovae IIn,
we conclude that SN 2013gc is a member of the so-called type IId subgroup. The
complex profile of the H line suggests a composite circumstellar medium
geometry, with a combination of lower velocity, spherically symmetric gas and a
more rapidly expanding bilobed feature. This circumstellar medium distribution
has been likely formed through major mass-loss events, that we directly
observed from 3 years before the explosion. The modest luminosity
( near maximum) of SN 2013gc at all phases, the very small amount
of ejected Ni (of the order of M), the major
pre-supernova stellar activity and the lack of prominent [O I] lines in
late-time spectra support a fall-back core-collapse scenario for the massive
progenitor of SN~2013gc.Comment: 20 pages, 11 figures, 8 tables, accepted by MNRA
Spectra and Light Curves of Failed Supernovae
Astronomers have proposed a number of mechanisms to produce supernova
explosions. Although many of these mechanisms are now not considered primary
engines behind supernovae, they do produce transients that will be observed by
upcoming ground-based surveys and NASA satellites. Here we present the first
radiation-hydrodynamics calculations of the spectra and light curves from three
of these "failed" supernovae: supernovae with considerable fallback, accretion
induced collapse of white dwarfs, and energetic helium flashes (also known as
type .Ia supernovae).Comment: 33 pages, 14 figure
High Density Circumstellar Interaction in the Luminous Type IIn SN 2010jl: The first 1100 days
HST and ground based observations of the Type IIn SN 2010jl are analyzed,
including photometry, spectroscopy in the ultraviolet, optical and NIR bands,
26-1128 days after first detection. At maximum the bolometric luminosity was
erg/s and even at 850 days exceeds erg/s. A NIR
excess, dominating after 400 days, probably originates in dust in the
circumstellar medium (CSM). The total radiated energy is
ergs, excluding the dust component. The spectral lines can be separated into
one broad component due to electron scattering, and one narrow with expansion
velocity km/s from the CSM. The broad component is initially
symmetric around zero velocity but becomes blueshifted after days,
while remaining symmetric about a shifted centroid velocity. Dust absorption in
the ejecta is unlikely to explain the line shifts, and we attribute the shift
instead to acceleration by the SN radiation. From the optical lines and the
X-ray and dust properties, there is strong evidence for large scale asymmetries
in the CSM. The ultraviolet lines indicate CNO processing in the progenitor,
while the optical shows a number of narrow coronal lines excited by the X-rays.
The bolometric light curve is consistent with a radiative shock in an
CSM with a mass loss rate of M_sun/yr. The total mass lost is
M_sun. These properties are consistent with the SN expanding into a CSM
characteristic of an LBV progenitor with a bipolar geometry. The apparent
absence of nuclear processing is attributed to a CSM still opaque to electron
scattering.Comment: ApJ in press. Updated and changed after referees comment
SN 2008in—Bridging the Gap between Normal and Faint Supernovae of Type IIP
We present optical photometric and low-resolution spectroscopic observations of the Type II plateau supernova (SN) 2008in, which occurred in the outskirts of the nearly face-on spiral galaxy M61. Photometric data in the X-ray, ultraviolet, and near-infrared bands have been used to characterize this event. The SN field was imaged with the ROTSE-IIIb optical telescope about seven days before the explosion. This allowed us to constrain the epoch of the shock breakout to JD = 2454825.6. The duration of the plateau phase, as derived from the photometric monitoring, was ~98 days. The spectra of SN 2008in show a striking resemblance to those of the archetypal low-luminosity IIP SNe 1997D and 1999br. A comparison of ejecta kinematics of SN 2008in with the hydrodynamical simulations of Type IIP SNe by Dessart et al. indicates that it is a less energetic event (~5 × 10^(50) erg). However, the light curve indicates that the production of radioactive ^(56)Ni is significantly higher than that in the low-luminosity SNe. Adopting an interstellar absorption along the SN direction of AV ~ 0.3 mag and a distance of 13.2 Mpc, we estimated a synthesized ^(56)Ni mass of ~0.015 M_☉. Employing semi-analytical formulae derived by Litvinova and Nadezhin, we derived a pre-SN radius of ~126 R_☉, an explosion energy of ~5.4 × 10^(50) erg, and a total ejected mass of ~16.7 M_☉. The latter indicates that the zero-age main-sequence mass of the progenitor did not exceed 20 M_☉. Considering the above properties of SN 2008in and its occurrence in a region of sub-solar metallicity ([O/H] ~ 8.44 dex), it is unlikely that fall-back of the ejecta onto a newly formed black hole occurred in SN 2008in. We therefore favor a low-energy explosion scenario of a relatively compact, moderate-mass progenitor star that generates a neutron star
The Absolute Magnitudes of Type Ia Supernovae in the Ultraviolet
We examine the absolute magnitudes and light-curve shapes of 14
nearby(redshift z = 0.004--0.027) Type Ia supernovae (SNe~Ia) observed in the
ultraviolet (UV) with the Swift Ultraviolet/Optical Telescope. Colors and
absolute magnitudes are calculated using both a standard Milky Way (MW)
extinction law and one for the Large Magellanic Cloud that has been modified by
circumstellar scattering. We find very different behavior in the near-UV
filters (uvw1_rc covering ~2600-3300 A after removing optical light, and u
~3000--4000 A) compared to a mid-UV filter (uvm2 ~2000-2400 A). The uvw1_rc-b
colors show a scatter of ~0.3 mag while uvm2-b scatters by nearly 0.9 mag.
Similarly, while the scatter in colors between neighboring filters is small in
the optical and somewhat larger in the near-UV, the large scatter in the
uvm2-uvw1 colors implies significantly larger spectral variability below 2600
A. We find that in the near-UV the absolute magnitudes at peak brightness of
normal SNe Ia in our sample are correlated with the optical decay rate with a
scatter of 0.4 mag, comparable to that found for the optical in our sample.
However, in the mid-UV the scatter is larger, ~1 mag, possibly indicating
differences in metallicity. We find no strong correlation between either the UV
light-curve shapes or the UV colors and the UV absolute magnitudes. With larger
samples, the UV luminosity might be useful as an additional constraint to help
determine distance, extinction, and metallicity in order to improve the utility
of SNe Ia as standardized candles.Comment: 59 pages, accepted for publication in Ap
Supernova 2010ev: A reddened high velocity gradient type Ia supernova
Aims. We present and study the spectroscopic and photometric evolution of the type Ia supernova (SN Ia) 2010ev
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