8468111
SN 1997bs in M66: Another Extragalactic η Carinae Analog?1
ABSTRACT We report on SN 1997bs in NGC 3627 (M66), the first supernova discovered by the Lick Observatory Supernova Search using the 0.75 m Katzman Automatic Imaging Telescope (KAIT). Based on its early‐time optical spectrum, SN 1997bs was classified as Type IIn. However, from the BVRI light curves obtained by KAIT early in the supernova’s evolution, and F555W and F814W light curves obtained from Hubble Space Telescope archival WFPC2 images at late times, we question the identification of SN 1997bs as a bona fide supernova. We believe that it is more likely a superoutburst of a very massive luminous blue variable star, analogous to η Carinae, and similar to SN 1961V in NGC 1058 (Filippenko et al. 1995 AJ, 110, 2261) and SN 1954J (“Variable 12”) in NGC 2403 (Humphreys & Davidson 1994 PASP, 106, 1025). The progenitor may have survived the outburst, since the SN is seen in early 1998 at \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs}...
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.
495485
Supernova 2008bk and its red supergiant progenitor
We have obtained limited photometric and spectroscopic data for supernova (SN) 2008bk in NGC 7793, primarily at ≳ 150 days after explosion. We find that it is a Type II-Plateau (II-P) SN that most closely resembles the low-luminosity SN 1999br in NGC 4900. Given the overall similarity between the observed light curves and colors of SNe 2008bk and 1999br, we infer that the total visual extinction to SN 2008bk (A_V = 0.065 mag) must be almost entirely due to the Galactic foreground, similar to what has been assumed for SN 1999br. We confirm the identification of the putative red supergiant (RSG) progenitor star of the SN in high-quality g'r'i' images we had obtained in 2007 at the Gemini-South 8 m telescope. Little ambiguity exists in this progenitor identification, qualifying it as the best example to date, next to the identification of the star Sk –69°202 as the progenitor of SN 1987A. From a combination of photometry of the Gemini images with that of archival, pre-SN, Very Large Telescope JHK_s images, we derive an accurate observed spectral energy distribution (SED) for the progenitor. We find from nebular strong-intensity emission-line indices for several H II regions near the SN that the metallicity in the environment is likely subsolar (Z ≈ 0.6 Z_☉). The observed SED of the star agrees quite well with synthetic SEDs obtained from model RSG atmospheres with effective temperature T_(eff) = 3600 ± 50 K. We find, therefore, that the star had a bolometric luminosity with respect to the Sun of log (L_(bol)/L_☉) = 4.57 ± 0.06 and radius R* = 496 ± 34 R_☉ at ~6 months prior to explosion. Comparing the progenitor's properties with theoretical massive-star evolutionary models, we conclude that the RSG progenitor had an initial mass in the range of 8-8.5 M_☉. This mass is consistent with, albeit at the low end of, the inferred range of initial masses for SN II-P progenitors. It is also consistent with the estimated upper limit on the initial mass of the progenitor of SN 1999br, and it agrees with the low initial masses found for the RSG progenitors of other low-luminosity SNe II-P.
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.
30616044
A Massive Progenitor of the Luminous Type IIn Supernova 2010jl
The bright, nearby, recently discovered supernova (SN) 2010jl is a luminous Type IIn SN. Here, we report archival Hubble Space Telescope (HST) observations of its host galaxy UGC 5189A taken roughly 10 yr prior to explosion, as well as early-time optical spectra of the SN. The HST images reveal a luminous, blue point source at the position of the SN, with an absolute magnitude of –12.0 in the F300W filter. If it is not just a chance alignment, the source at the SN position could be (1) a massive young (<6 Myr) star cluster in which the SN resided, (2) a quiescent, luminous blue star with an apparent temperature around 14,000 K, (3) a star caught during a bright outburst akin to those of luminous blue variables, or (4) a combination of option (1) and option (2) or (3). Although we cannot confidently choose between these possibilities with the present data, any of them imply that the progenitor of SN 2010jl had an initial mass above 30 M_☉. This reinforces mounting evidence that many SNe IIn result from very massive stars, that massive stars can produce visible SNe without collapsing quietly to black holes, and that massive stars can sometimes retain their H envelopes until shortly before explosion. Standard stellar evolution models fail to account for these observed properties.
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.
119292700
Matter fields near quantum critical point in (2+1)-dimensional U(1) gauge theory
We study chiral phase transition and confinement of matter fields in (2+1)-dimensional U(1) gauge theory of massless Dirac fermions and scalar bosons. The vanishing scalar boson mass, r = 0, defines a quantum critical point between the Higgs phase and the Coulomb phase. We consider only the critical point r = 0 and the Coulomb phase with r > 0. The Dirac fermion acquires a dynamical mass when its flavor is less than certain critical value N c f , which depends quantitatively on the flavor Nb and the scalar boson mass r. When Nf < N c f , the matter fields carrying internal gauge charge are all confined if r 6 0 but are deconfined at the quantum critical point r = 0. The system has distinct low-energy elementary excitations at the critical point r = 0 and in the Coulomb phase with r 6 0. We calculate the specific heat and susceptibility of the system at r = 0 and r 6 0, which can help to detect the quantum critical point and to judge whether dynamical fermion mass generation takes place.
119183379
Fourteen months of observations of the possible super-Chandrasekhar mass Type Ia Supernova 2009dc
In this paper, we present and analyse optical photometry and spectra of the extremely luminous and slowly evolving Type Ia supernova (SN Ia) 2009dc, and offer evidence that it is a super-Chandrasekhar mass (SC) SN Ia and thus has a SC white dwarf (WD) progenitor. Optical spectra of SN 2007if, a similar object, are also shown. SN 2009dc had one of the most slowly evolving light curves ever observed for a SN Ia, with a rise time of ~23 d and Δm 15 (B) = 0.72 mag. We calculate a lower limit to the peak bolometric luminosity of ~2.4 x 10 43 erg s -1 , though the actual value is likely almost 40 per cent larger. Optical spectra of SN 2009dc and SN 2007if obtained near maximum brightness exhibit strong C II features (indicative of a significant amount of unburned material), and the post-maximum spectra are dominated by iron-group elements (IGEs). All of our spectra of SN 2009dc and SN 2007if also show low expansion velocities. However, we see no strong evidence in SN 2009dc for a velocity 'plateau' near maximum light like the one seen in SN 2007if. The high luminosity and low expansion velocities of SN 2009dc lead us to derive a possible WD progenitor mass of more than 2 M ⊙ and a 56 Ni mass of about 1.4-1.7 M ⊙ . We propose that the host galaxy of SN 2009dc underwent a gravitational interaction with a neighbouring galaxy in the relatively recent past. This may have led to a sudden burst of star formation which could have produced the SC WD progenitor of SN 2009dc and likely turned the neighbouring galaxy into a 'post-starburst galaxy'. No published model seems to match the extreme values observed in SN 2009dc, but simulations do show that such massive progenitors can exist (likely as a result of the merger of two WDs) and can possibly explode as SC SNe Ia.
119520173
RAMPING CONTROL OF HLS STORAGE RING
HLS (Hefei Light Source) is a second generation synchrotron radiation source. After injection into the storage ring at an energy of 200MeV, the electrons will be ramped to 800MeV. During ramping, the magnetic fields of the bend, quadrapole and sextapole magnets are ramped up synchronously to keep the working point of the storage ring unchanged. This process is carefully controlled by the HLS control system, which is built using EPICS. Several measures are taken to insure the synchronization and linearity of the ramping.
9048620
On string theory duals of Lifshitz-like fixed points
We present type IIB supergravity solutions which are expected to be dual to certain Lifshitz-like fixed points with anisotropic scale invariance. They are expected to describe a class of D3-D7 systems and their finite temperature generalizations are straightforward. We show that there exist solutions that interpolate between these anisotropic solutions in the IR and the standard AdS5 solutions in the UV. This predicts anisotropic RG flows from familiar isotropic fixed points to anisotropic ones. In our case, these RG flows are triggered by a non-zero theta-angle in Yang-Mills theories that linearly depends on one of the spatial coordinates. We study the perturbations around these backgrounds and discuss the possibility of instability. We also holographically compute their thermal entropies, viscosities, and entanglement entropies.
14441114
OPTICAL AND NEAR-INFRARED OBSERVATIONS OF THE HIGHLY REDDENED, RAPIDLY EXPANDING TYPE Ia SUPERNOVA SN 2006X IN M100
We present extensive optical (UBVRI), near-infrared (JK) light curves and optical spectroscopy of the Type Ia supernova SN 2006X in the nearby galaxy NGC 4321 (M100). Our observations suggest that either SN 2006X has an intrinsically peculiar color evolution or it is highly reddened [E(B − V)host = 1.42 ± 0.04 mag ] with RV = 1.48 ± 0.06, much lower than the canonical value of 3.1 for the average Galactic dust. SN 2006X also has one of the highest expansion velocities ever published for an SN Ia. Compared with the other SNe Ia we analyzed, SN 2006X has a broader light curve in the U band, a more prominent bump/shoulder feature in the V and R bands, a more pronounced secondary maximum in the I and NIR bands, and a remarkably smaller late-time decline rate in the B band. The B − V color evolution shows an obvious deviation from the Lira-Phillips relation at 1-3 months after maximum brightness. At early times, optical spectra of SN 2006X displayed strong, high-velocity features of both intermediate-mass elements (Si, Ca, and S) and iron peak elements, while at late times they showed a relatively blue continuum, consistent with the blue U − B and B − V colors at similar epochs. A light echo and/or the interaction of the SN ejecta and its circumstellar material may provide a plausible explanation for its late-time photometric and spectroscopic behavior. Using the Cepheid distance of M100, we derive a Hubble constant of 72.8 ± 8.2 km s−1 Mpc−1 (statistical) from the normalized dereddened luminosity of SN 2006X. We briefly discuss whether abnormal dust is a universal signature for all SNe Ia and whether the most rapidly expanding objects form a subclass with distinct photometric and spectroscopic properties.