Supernova (SN) 2002ap in M74 was observed in the U BV RIJHK bands for the first 40 days following its discovery (2002 January 29) until it disappeared because of solar conjunction, and then in June after it reappeared. The magnitudes and dates of peak brightness in each band were determined. While the rate of increase of the brightness before the peak is almost independent of wavelength, the subsequent rate of decrease becomes smaller with wavelength from the U to the R band, and is constant at wavelengths beyond I. The photometric evolution is faster than in the well-known "hypernovae" SNe 1998bw and 1997ef, indicating that SN 2002ap ejected less mass. The bolometric light curve of SN 2002ap for the full period of observations was constructed. The absolute magnitude is found to be much fainter than that of SN 1998bw, but is similar to that of SN 1997ef, which lies at the faint end of the hypernova population. The bolometric light curve at the early epochs was best reproduced with the explosion of a C+O star that ejects 2.5 M ⊙ with kinetic energy E K = 4 × 10 51 ergs. A comparison of the predicted brightness of SN 2002ap with that observed after solar conjunction may imply that γ-ray deposition at the later epochs was more efficient than in the model. This may be due to an asymmetric explosion.Subject headings: supernovae: general-supernovae: individual (SN 2002ap)-supernovae: photometry
The James Webb Space Telescope (JWST) was conceived and built to answer one of the most fundamental questions that humans can address empirically: "How did the Universe make its first stars?". This can be attempted in classical stare mode and by still photography -with all the pitfalls of crowding and multiband redshifts of objects of which a spectrum was never obtained. Our First Lights At REionization (FLARE) project transforms the quest for the epoch of reionization from the static to the time domain. It targets the complementary question: "What happened to those first stars?". It will be answered by observations of the most luminous events: supernovae and accretion on to black holes formed by direct collapse from the primordial gas clouds. These transients provide direct constraints on star-formation rates and the truly initial initial mass function, and they may identify possible stellar seeds of supermassive black holes. Furthermore, our knowledge of the physics of these events at ultra-low metallicity will be much expanded. JWST's unique capabilities will detect these most luminous and earliest cosmic messengers easily in fairly shallow observations. However, these events are very rare at the dawn of cosmic structure formation and so require large area coverage. Time domain astronomy can be advanced to an unprecedented depth by means of a shallow field of JWST reaching 27 mag (AB) in 2 µm and 4.4 µm over a field as large as 0.1 square degree visited multiple times each year. Such a survey may set strong constraints or detect massive Population III supernovae at redshifts beyond 10, pinpointing the redshift of the first stars, or at least their death. Based on our current knowledge of superluminous supernovae, such a survey will find one or more superluminous supernovae at redshifts above 6 in five years and possibly several direct collapse black holes.In addition, the large scale structure that is the trademark of the epoch of reion--3ization will be detected. Although JWST is not designed as a wide field survey telescope, we show that such a wide field survey is possible with JWST and is critical in addressing several of its key scientific goals.
We give a differential-geometric construction of Calabi-Yau fourfolds by the 'doubling' method, which was introduced in [5] to construct Calabi-Yau threefolds. We also give examples of Calabi-Yau fourfolds from toric Fano fourfolds. Ingredients in our construction are admissible pairs, which were first dealt with by Kovalev in [11]. Here in this paper an admissible pair (X, D) consists of a compact Kähler manifold X and a smooth anticanonical divisor D on X. If two admissible pairs (X 1 , D 1 ) and (X 2 , D 2 ) with dim C X i = 4 satisfy the gluing condition, we can glue X 1 \ D 1 and X 2 \ D 2 together to obtain a compact Riemannian 8-manifold (M, g) whose holonomy group Hol(g) is contained in Spin (7). Furthermore, if the A-genus of M equals 2, then M is a Calabi-Yau fourfold, i.e., a compact Ricci-flat Kähler fourfold with holonomy SU(4). In particular, if (X 1 , D 1 ) and (X 2 , D 2 ) are identical to an admissible pair (X, D), then the gluing condition holds automatically, so that we obtain a compact Riemannian 8-manifold M with holonomy contained in Spin (7). Moreover, we show that if the admissible pair is obtained from any of the toric Fano fourfolds, then the resulting manifold M is a Calabi-Yau fourfold by computing A(M ) = 2.1 2 MAMORU DOI AND NAOTO YOTSUTANI Thus D 1 and D 2 are at least diffeomorphic and so are the cylindrical ends of X 1 \ D 1 and X 2 \ D 2 which we glue together. Meanwhile in the four-dimensional case, the topological type of the Calabi-Yau divisor D for an admissible pair (X, D) varies with X. However, if (X 1 , D 1 ) and (X 2 , D 2 ) are identical to an admissible pair (X, D), then the gluing condition holds automatically. Therefore we can always construct a compact simply-connected Riemannian 8-manifold (M, g) with Hol(g) ⊆ Spin (7) by doubling an admissible pair (X, D) with dim C X = 4.Beginning with a Fano n-fold V , Kovalev obtained an admissible pair (X, D) as follows. It is known that there exists a smooth anticanonical divisor D on V , which is a K3 surface when n = 3 and Calabi-Yau (n − 1)-fold when n 4. Let S be a complex (n − 2)-dimensional submanifold of D such that S represents the self-intersection class D · D in V . Then he showed that if X is the blow-up of V along S, the proper transform of D in X (which is isomorphic to D and denoted by D again) is an anticanonical divisor on X with the holomorphic normal bundle N D/X trivial, so that (X, D) is the desired admissible pair. In [5], we used Fano threefolds V in order to obtain admissible pairs (X, D) with dim C X = 3 in our doubling construction of Calabi-Yau threefolds. According to Mori-Mukai's classification of Fano threefolds, we gave 59 topologically distinct Calabi-Yau threefolds.In the four-dimensional case, two problems arise in constructing Calabi-Yau manifolds by the doubling. The first is that we have no complete classification of Fano fourfolds. The second is that it is not easy to compute the A-genus A(M ) of the 'doubled' manifold M if we use an arbitrary Fano fourfold. Instead of considering all Fano...
ANIR (Atacama Near InfraRed camera) is a near infrared camera for the University of Tokyo Atacama 1m telescope, installed at the summit of Co. Chajnantor (5,640 m altitude) in northern Chile. The high altitude and extremely low water vapor (PWV = 0.5 mm) of the site enable us to perform observation of hydrogen Paα emission line at 1.8751 µm. Since its first light observation in June 2009, we have been carrying out a Paα narrow-band imaging survey of nearby luminous infrared galaxies (LIRGs), and have obtained Paα for 38 nearby LIRGs listed in AKARI/FIS-PSC at the velocity of recession between 2,800 km/s and 8,100 km/s. LIRGs are affected by a large amount of dust extinction (A V ∼ 3 mag), produced by their active star formation activities. Because Paα is the strongest hydrogen recombination line in the infrared wavelength ranges, it is a good and direct tracer of dust-enshrouded star forming regions, and enables us to probe the star formation activities in LIRGs. We find that LIRGs have two star-forming modes. The origin of the two modes probably come from differences between merging stage and/or star-forming process.
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