26 research outputs found
Optical Properties of (162173) 1999 JU3: In Preparation for the JAXA Hayabusa 2 Sample Return Mission
We investigated the magnitude-phase relation of (162173) 1999 JU3, a target
asteroid for the JAXA Hayabusa 2 sample return mission. We initially employed
the international Astronomical Union's H-G formalism but found that it fits
less well using a single set of parameters. To improve the inadequate fit, we
employed two photometric functions, the Shevchenko and Hapke functions. With
the Shevchenko function, we found that the magnitude-phase relation exhibits
linear behavior in a wide phase angle range (alpha = 5-75 deg) and shows weak
nonlinear opposition brightening at alpha< 5 deg, providing a more reliable
absolute magnitude of Hv = 19.25 +- 0.03. The phase slope (0.039 +- 0.001
mag/deg) and opposition effect amplitude (parameterized by the ratio of
intensity at alpha=0.3 deg to that at alpha=5 deg, I(0.3)/I(5)=1.31+-0.05) are
consistent with those of typical C-type asteroids. We also attempted to
determine the parameters for the Hapke model, which are applicable for
constructing the surface reflectance map with the Hayabusa 2 onboard cameras.
Although we could not constrain the full set of Hapke parameters, we obtained
possible values, w=0.041, g=-0.38, B0=1.43, and h=0.050, assuming a surface
roughness parameter theta=20 deg. By combining our photometric study with a
thermal model of the asteroid (Mueller et al. in preparation), we obtained a
geometric albedo of pv = 0.047 +- 0.003, phase integral q = 0.32 +- 0.03, and
Bond albedo AB = 0.014 +- 0.002, which are commensurate with the values for
common C-type asteroids.Comment: 27 pages, 4 figure, accepted for publication in the Astrophysical
Journa
H-alpha Spectral diversity of type II supernovae
We present a spectroscopic analysis of the H-alpha profiles of hydrogen-rich
type II supernovae. A total of 52 type II supernovae having well sampled
optical light curves and spectral sequences were analyzed. Concentrating on the
H-alpha P-Cygni profile we measure its velocity from the FWHM of emission and
the ratio of absorption to emission (a/e) at a common epoch at the start of the
recombination phase, and search for correlations between these spectral
parameters and photometric properties of the V-band light curves. Testing the
strength of various correlations we find that a/e appears to be the dominant
spectral parameter in terms of describing the diversity in our measured
supernova properties. It is found that supernovae with smaller a/e have higher
H-alpha velocities, more rapidly declining light curves from maximum, during
the plateau and radioactive tail phase, are brighter at maximum light and have
shorter optically thick phase durations. We discuss possible explanations of
these results in terms of physical properties of type II supernovae,
speculating that the most likely parameters which influence the morphologies of
H-alpha profiles are the mass and density profile of the hydrogen envelope,
together with additional emission components due to circumstellar interaction.Comment: Accepted for publication in ApJ letters. 9 pages, 3 figures, 2 table
Do the photometric colors of Type II-P Supernovae allow accurate determination of host galaxy extinction?
We present infrared photometry of SN 1999em, plus optical photometry,
infrared photometry, and optical spectroscopy of SN 2003hn. Both objects were
Type II-P supernovae. The V-[RIJHK] color curves of these supernovae evolved in
a very similar fashion until the end of plateau phase. This allows us to
determine how much more extinction the light of SN 2003hn suffered compared to
SN 1999em. Since we have an estimate of the total extinction suffered by SN
1999em from model fits of ground-based and space-based spectra as well as
photometry of SN 1999em, we can estimate the total extinction and absolute
magnitudes of SN 2003hn with reasonable accuracy. Since the host galaxy of SN
2003hn also produced the Type Ia SN 2001el, we can directly compare the
absolute magnitudes of these two SNe of different types.Comment: 24 pages, 6 figure
UBVRIz Light Curves of 51 Type II Supernovae
We present a compilation of UBV RIz light curves of 51 type II supernovae
discovered during the course of four different surveys during 1986 to 2003: the
Cerro Tololo Supernova Survey, the Calan/Tololo Supernova Program (C&T), the
Supernova Optical and Infrared Survey (SOIRS), and the Carnegie Type II
Supernova Survey (CATS). The photometry is based on template-subtracted images
to eliminate any potential host galaxy light contamination, and calibrated from
foreground stars. This work presents these photometric data, studies the color
evolution using different bands, and explores the relation between the
magnitude at maximum brightness and the brightness decline parameter (s) from
maximum light through the end of the recombination phase. This parameter is
found to be shallower for redder bands and appears to have the best correlation
in the B band. In addition, it also correlates with the plateau duration, being
thus shorter (longer) for larger (smaller) s values.Comment: 110 pages, 9 Figures, 6 Tables, accepted in A
The fast declining Type Ia supernova 2003gs, and evidence for a significant dispersion in near-infrared absolute magnitudes of fast decliners at maximum light
We obtained optical photometry of SN 2003gs on 49 nights, from 2 to 494 days
after T(B_max). We also obtained near-IR photometry on 21 nights. SN 2003gs was
the first fast declining Type Ia SN that has been well observed since SN
1999by. While it was subluminous in optical bands compared to more slowly
declining Type Ia SNe, it was not subluminous at maximum light in the near-IR
bands. There appears to be a bimodal distribution in the near-IR absolute
magnitudes of Type Ia SNe at maximum light. Those that peak in the near-IR
after T(B_max) are subluminous in the all bands. Those that peak in the near-IR
prior to T(B_max), such as SN 2003gs, have effectively the same near-IR
absolute magnitudes at maximum light regardless of the decline rate Delta
m_15(B).
Near-IR spectral evidence suggests that opacities in the outer layers of SN
2003gs are reduced much earlier than for normal Type Ia SNe. That may allow
gamma rays that power the luminosity to escape more rapidly and accelerate the
decline rate. This conclusion is consistent with the photometric behavior of SN
2003gs in the IR, which indicates a faster than normal decline from
approximately normal peak brightness.Comment: 41 pages, 13 figures, to be published in the December, 2009, issue of
the Astronomical Journa
SN 2003bg: The First Type IIb Hypernova
Optical and near-infrared photometry and optical spectroscopy are reported
for SN 2003bg, starting a few days after explosion and extending for a period
of more than 300 days. Our early-time spectra reveal the presence of broad,
high-velocity Balmer lines. The nebular-phase spectra, on the other hand, show
a remarkable resemblance to those of Type Ib/c supernovae, without clear
evidence for hydrogen. Near maximum brightness SN 2003bg displayed a bolometric
luminosity comparable to that of other Type I hypernovae unrelated to gamma-ray
bursts, implying a rather normal amount of 56Ni production (0.1-0.2 Msun)
compared with other such objects. The bolometric light curve of SN 2003bg, on
the other hand, is remarkably broad, thus suggesting a relatively large
progenitor mass at the moment of explosion. These observations, together with
the large value of the kinetic energy of expansion established in the
accompanying paper (Mazzali et al. 2009), suggest that SN 2003bg can be
regarded as a Type IIb hypernova.Comment: 41 pages, 12 figures, accepted by The Astrophysical Journa
SPLUS J142445.34-254247.1: An R-Process Enhanced, Actinide-Boost, Extremely Metal-Poor star observed with GHOST
We report on the chemo-dynamical analysis of SPLUS J142445.34-254247.1, an
extremely metal-poor halo star enhanced in elements formed by the rapid
neutron-capture process. This star was first selected as a metal-poor candidate
from its narrow-band S-PLUS photometry and followed up spectroscopically in
medium-resolution with Gemini South/GMOS, which confirmed its low-metallicity
status. High-resolution spectroscopy was gathered with GHOST at Gemini South,
allowing for the determination of chemical abundances for 36 elements, from
carbon to thorium. At [Fe/H]=-3.39, SPLUS J1424-2542 is one of the lowest
metallicity stars with measured Th and has the highest logeps(Th/Eu) observed
to date, making it part of the "actinide-boost" category of r-process enhanced
stars. The analysis presented here suggests that the gas cloud from which SPLUS
J1424-2542 was formed must have been enriched by at least two progenitor
populations. The light-element (Z<=30) abundance pattern is consistent with the
yields from a supernova explosion of metal-free stars with 11.3-13.4 Msun, and
the heavy-element (Z>=38) abundance pattern can be reproduced by the yields
from a neutron star merger (1.66Msun and 1.27Msun) event. A kinematical
analysis also reveals that SPLUS J1424-2542 is a low-mass, old halo star with a
likely in-situ origin, not associated with any known early merger events in the
Milky Way.Comment: 26 pages, 11 figures, accepted for publication on Ap
CHARACTERIZING THE V -BAND LIGHT-CURVES OF HYDROGEN-RICH TYPE II SUPERNOVAE
We present an analysis of the diversity of V-band light-curves of
hydrogen-rich type II supernovae. Analyzing a sample of 116 supernovae, several
magnitude measurements are defined, together with decline rates at different
epochs, and time durations of different phases. It is found that magnitudes
measured at maximum light correlate more strongly with decline rates than those
measured at other epochs: brighter supernovae at maximum generally have faster
declining light-curves at all epochs. We find a relation between the decline
rate during the 'plateau' phase and peak magnitudes, which has a dispersion of
0.56 magnitudes, offering the prospect of using type II supernovae as purely
photometric distance indicators. Our analysis suggests that the type II
population spans a continuum from low-luminosity events which have flat
light-curves during the 'plateau' stage, through to the brightest events which
decline much faster. A large range in optically thick phase durations is
observed, implying a range in progenitor envelope masses at the epoch of
explosion. During the radioactive tails, we find many supernovae with faster
declining light-curves than expected from full trapping of radioactive
emission, implying low mass ejecta. It is suggested that the main driver of
light-curve diversity is the extent of hydrogen envelopes retained before
explosion. Finally, a new classification scheme is introduced where
hydrogen-rich events are typed as simply 'SNII' with an s2 value giving the
decline rate during the 'plateau' phase, indicating its morphological type.Comment: Accepted for publication in ApJ. Revised edition corrects errors in
affiliation number
Two campaigns to compare three turbulence profiling techniques at Las Campanas Observatory
In preparation to characterize the Giant Magellan Telescope site and guide the development of its adaptive optics system, two campaigns to systematically compare the turbulence profiles obtained independently with three different instruments were conducted at Las Campanas Observatory in September, 2007 and January 2008. Slope detection and ranging (SLODAR) was used on the 2.5-m duPont telescope. SLODAR measures the C2n profile as a function of altitude through observations of double stars. The separation of the observed double star sets the maximum altitude and height resolution. Ground layer (altitudes < 1 km) and free atmosphere turbulence profiles are compared with those obtained with a lunar scintillometer (LuSci) and a multi-aperture scintillation sensor (MASS), respectively. In addition, the total atmospheric seeing was measured by both SLODAR and a differential image motion monitor (DIMM)