4807313
On the Progenitors of Two Type II-P Supernovae in the Virgo Cluster
Direct identification of the progenitors of supernovae (SNe) is rare because of the required spatial resolution and depth of the archival data prior to the SN explosions. Here we report on the identification of the progenitors of two nearby SNe in the Virgo Cluster: SN 2006my in NGC 4651 and SN 2006ov in M61. We obtained high-quality ground-based images of SN 2006my with the Canada-France-Hawaii Telescope, and are able to locate the site of the SN on pre-SN Hubble Space Telescope (HST) Wide Field Planetary Camera 2 images to a high precision (1 σ uncertainty of ±0.05"). We pinpoint the site of SN 2006ov to within 0.02" from HST Advanced Camera for Surveys images of the SN. We detected a red supergiant progenitor for each SN within the error circles, with an inferred zero-age main-sequence mass (M_(zams)) of 10^(+5)_(-3) and 15^(+5)_(-3) M_⊙ for the progenitors of SNe 2006my and 2006ov, respectively. The mass estimates for the progenitors of both SNe confirm a suggested trend that the most common Type II-plateau SNe originate from low-mass supergiants with M_(zams) ≈ 8-20 M_⊙.
60399635
The Carnegie Supernova Project: Analysis of the First Sample of Low-Redshift Type-Ia Supernovae
An analysis of the first set of low-redshift (z < 0.08) Type Ia supernovae (SNe Ia) monitored by the Carnegie Supernova Project between 2004 and 2006 is presented. The data consist of well-sampled, high-precision optical (ugriBV) and near-infrared (NIR; YJHKs ) light curves in a well-understood photometric system. Methods are described for deriving light-curve parameters, and for building template light curves which are used to fit SN Ia data in the ugriBVYJH bands. The intrinsic colors at maximum light are calibrated using a subsample of supernovae (SNe) assumed to have suffered little or no reddening, enabling color excesses to be estimated for the full sample. The optical-NIR color excesses allow the properties of the reddening law in the host galaxies to be studied. A low average value of the total-to-selective absorption coefficient, RV 1.7, is derived when using the entire sample of SNe. However, when the two highly reddened SNe (SN 2005A and SN 2006X) in the sample are excluded, a value RV 3.2 is obtained, similar to the standard value for the Galaxy. The red colors of these two events are well matched by a model where multiple scattering of photons by circumstellar dust steepens the effective extinction law. The absolute peak magnitudes of the SNe are studied in all bands using a two-parameter linear fit to the decline rates and the colors at maximum light, or alternatively, the color excesses. In both cases, similar results are obtained with dispersions in absolute magnitudes of 0.12-0.16?mag, depending on the specific filter-color combination. In contrast to the results obtained from the comparison of the color excesses, these fits of absolute magnitude give RV 1-2 when the dispersion is minimized, even when the two highly reddened SNe are excluded. This discrepancy suggests that, beyond the normal interstellar reddening produced in the host galaxies, there is an intrinsic dispersion in the colors of SNe Ia which is correlated with luminosity but independent of the decline rate. Finally, a Hubble diagram for the best-observed subsample of SNe is produced by combining the results of the fits of absolute magnitude versus decline rate and color excess for each filter. The resulting scatter of 0.12 mag appears to be limited by the peculiar velocities of the host galaxies as evidenced by the strong correlation between the distance-modulus residuals observed in the individual filters. The implication is that the actual precision of SNe Ia distances is 3%-4%.
46679854
Classifications of the Host Galaxies of Supernovae
Classifications on the DDO system are given for the host galaxies of 177 supernovae (SNe) that have been discovered since 1997 during the course of the Lick Observatory Supernova Search with the Katzman Automatic Imaging Telescope. Whereas SNe Ia occur in all galaxy types, it is found, at a high level of statistical confidence, that SNe Ib, Ic, and II are strongly concentrated in late‐type galaxies. However, attention is drawn to a possible exception provided by SN 2001I. This SN IIn occurred in the E2 galaxy UGC 2836, which was not expected to harbor a massive young supernova progenitor.
118898696
OPTICAL PHOTOMETRY OF THE TYPE II-P SUPERNOVA 2004dj IN NGC 2403
We present photometric data of the Type II-P supernova (SN) 2004dj in NGC 2403. The multicolor light curves cover the SN from ~60 to 200 days after explosion and are measured with a set of intermediate-band filters that have the advantage of tracing the strength variations of some spectral features. The light curves show a flat evolution in the middle of the plateau phase, then decline exponentially at the late times, with a rate of 0.10 ± 0.03 mag (10 days)-1 in most of the filters. In the nebular phase, the spectral energy distribution of SN 2004dj shows a steady increase in the flux near 6600 and 8500 A, which may correspond to the emission lines of Hα and the Ca II near-IR triplet, respectively. The photometric behavior suggests that SN 2004dj is a normal SN II-P. Compared with the light curves of another typical SN II-P, 1999em, we estimate the explosion date to be 2004 June 10 ± 21 UT (JD 2,453,167 ± 21) for SN 2004dj. We also estimate the ejected nickel mass during the explosion to be M(56Ni) = 0.023 ± 0.005 M⊙ from two different methods, which is typical for a SN II-P. We derive the explosion energy to be E ≈ 0.75 × 1051 ergs, the ejecta mass to be M ≈ 10.0 M⊙, and the initial radius to be R ≈ 282 R⊙ for the presupernova star of SN 2004dj, which are consistent with other typical SNe II-P.
119196087
OPTICAL OBSERVATIONS OF THE TYPE Ic SUPERNOVA 2007gr IN NGC 1058
We present extensive optical observations of the normal Type Ic supernova (SN) 2007gr, spanning from about one week before maximum light to more than one year thereafter. The optical light and color curves of SN 2007gr are very similar to those of the broad-lined Type Ic SN 2002ap, but the spectra show remarkable differences. The optical spectra of SN 2007gr are characterized by unusually narrow lines, prominent carbon lines, and slow evolution of the line velocity after maximum light. The earliest spectrum (taken at t = –8 days) shows a possible signature of helium (He I λ5876 at a velocity of ~19,000 km s–1). Moreover, the larger intensity ratio of the [O I] λ6300 and λ6364 lines inferred from the early nebular spectra implies a lower opacity of the ejecta shortly after the explosion. These results indicate that SN 2007gr perhaps underwent a less energetic explosion of a smaller-mass Wolf-Rayet star (~8-9 M ☉) in a binary system, as favored by an analysis of the progenitor environment through pre-explosion and post-explosion Hubble Space Telescope images. In the nebular spectra, asymmetric double-peaked profiles can be seen in the [O I] λ6300 and Mg I] λ4571 lines. We suggest that the two peaks are contributed by the blueshifted and rest-frame components. The similarity in velocity structure and the different evolution of the strength of the two components favor an aspherical explosion with the ejecta distributed in a torus or disk-like geometry, but inside the ejecta the O and Mg have different distributions.
28101827
THE PROGENITOR OF SUPERNOVA 2011 dh / PTF 11 eon IN MESSIER 51
We have identified a luminous star at the position of supernova (SN) 2011dh/PTF11eon, in pre-SN archival, multi-band images of the nearby, nearly face-on galaxy Messier 51 (M51) obtained by the Hubble Space Telescope with the Advanced Camera for Surveys. This identification has been confirmed, to the highest available astrometric precision, using a Keck-II adaptive-optics image. The available early-time spectra and photometry indicate that the SN is a stripped-envelope, core-collapse Type IIb, with a more compact progenitor (radius ∼ 1011 cm) than was the case for the well-studied SN IIb 1993J. We infer that the extinction to SN 2011dh and its progenitor arises from a low Galactic foreground contribution, and that the SN environment is of roughly solar metallicity. The detected object has absolute magnitude M0 V ≈ −7.7 and effective temperature ∼6000 K. The star’s radius, ∼1013 cm, is more extended than what has been inferred for the SN progenitor. We speculate that the detected star is either an unrelated star very near the position of the actual progenitor, or, more likely, the progenitor’s companion in a mass-transfer binary system. The position of the detected star in a Hertzsprung–Russell diagram is consistent with an initial mass of 17–19 M . The light of this star could easily conceal, even in the ultraviolet, the presence of a stripped, compact, very hot (∼105 K), nitrogen-rich Wolf–Rayet star progenitor.
119484634
R2 corrections for 5D black holes and rings
We study higher-order corrections to two BPS solutions of 5D supergravity, namely the supersymmetric black ring and the spinning black hole. Due to our current relatively limited understanding of F-type terms in 5D supergravity, the nature of these corrections is less clear than that of their 4D cousins. Effects of certain R2 terms found in Calabi-Yau compactification of M-theory are specifically considered. For the case of the black ring, for which the microscopic origin of the entropy is generally known, the corresponding higher order macroscopic correction to the entropy is found to match a microscopic correction, while for the spinning black hole the corrections are partially matched to those of a 4D D0−D2−D6 black hole.
119362823
Supernova 1954J (Variable 12) in NGC 2403 Unmasked
We have confirmed that the precursor star of the unusual supernova 1954J (also known as Variable 12) in NGC 2403 survived what appears to have been a superoutburst, similar to the 1843 Great Eruption of η Carinae in the Galaxy. The apparent survivor has changed little in brightness and color over the last 8 years, and a Keck spectrum reveals characteristics broadly similar to those of η Car. This is further suggested by our identification of the actual outburst-surviving star in high-resolution images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope. We reveal this "supernova impostor" as a highly luminous ( mag), very massive (Minitial 25 M⊙) eruptive star, now surrounded by a dusty (AV ≈ 4 mag) nebula, similar to η Car's famous Homunculus.
43304761
A low emittance lattice design for hls storage ring
Reducing beam emittance is the most effective measure to enhance brilliance of light source. HLS (Hefei light source) is a second generation synchrotron light source, whose emittance is relatively large. To improve the performance of HLS, a new low emittance lattice, whose circumference is similar to that of current storage ring but the focusing structure was different, was studied and presented in this paper. The new ring can be set upon current ground settlement of HLS, while all magnets would be reconstructed. The new designed lattice has two operation modes, the low emittance mode, whose purpose is to reduce beam emittance and to increase the number of straight section, and the low momentum compaction mode, whose purpose is to adjust bunch length for the production of coherent THz radiation. After optimization, beam emittance was reduced to several nmmiddotrad, and the dynamic aperture for on-momentum and off-momentum particle is large enough. It is conceivable that, with the new lattice, the brilliance of HLS should be increased two orders.
16379990
A high peculiarity rate for Type Ia SNe
We have compiled a sample of 90 SNe Ia from 1997 to 1999 (up to SN 1999da) and studied the peculiarity rate of SN 1991T, SN 1991bg and SN 1986G-like objects. A Monte Carlo code was written to study the observational biases involved in the evaluation of the intrinsic peculiarity rate of SNe Ia. We find that SNe Ia have a high peculiarity rate (>30%) and a flat luminosity function.
14536751
Some No-go Theorems for String Duals of Non-relativistic Lifshitz-like Theories
We study possibilities of string theory embeddings of the gravity duals for non-relativistic Lifshitz-like theories with anisotropic scale invariance. We search classical solutions in type IIA and eleven-dimensional supergravities which are expected to be dual to (2+1)-dimensional Lifshitz-like theories. Under reasonable ansatze, we prove that such gravity duals in the supergravities are not possible. We also discuss a possible physical reason behind this.