RESUMO
In this paper we describe the Kottamia Faint Imaging Spectro-Polarimeter (KFISP) that has been recently developed and designed to be mounted at the Cassegrain focus of the 1.88 m telescope at Kottamia Astronomical Observatory (KAO), Egypt. The optical design of KFISP is developed such that it can be used in various modes of operation. These are: direct imaging, spectroscopic, polarimetric imaging, and spectro-polarimetric. The KFISP is an all-refractive design to meet the polarimetric requirements and includes a focal reducer with a corrector section, collimator section, parallel beam section (containing various imaging components), and camera section. The corrector section gives an unvignetted Field-of-View of 8' × 8' and the collimator section has a focal length of 305 mm and matches the focal ratio of the input beam. The parallel beam section is 200 mm long and near the middle of it there is an image of the telescope pupil. The camera section includes 5 elements and has a focal length of 154.51 mm which gives an instrument effective final focal ratio of f/6.14 (acting as a telescope focal reducer of 1:2 ratio). The KFISP contains an internal calibration system which hosts the calibration light injection system, an integrating sphere equipped with the required calibration light sources. The opto-mechanical parts of KFISP contain a double-layered carbon fiber strut structure and comprises its subsystems of slit and guider assemblies, filter wheel drawer, grism wheel drawer, polarimetric components cubical box, and CCD camera which is integrated with camera optics. The CCD camera has 2048 × 2048 pixels with 13.5-micron square pixel size. The camera is cooled by liquid Nitrogen and is fixed to the KFISP through the integrated camera lens. The KFISP has been fully commissioned, mounted and is being tested in all modes of operation. In this paper we introduce the ambitious scientific goals, the optical setups of KFISP, its opto-mechanical implementation and the performance analysis of the instrument. In addition, we describe the camera system, its performance, and its software control. Finally, we present a sample of the first light observations obtained from the instrument.
RESUMO
Superluminous supernovae radiate up to 100 times more energy than normal supernovae. The origin of this energy and the nature of the stellar progenitors of these transients are poorly understood. We identify neutral iron lines in the spectrum of one such supernova, SN 2006gy, and show that they require a large mass of iron (â³0.3 solar masses) expanding at 1500 kilometers per second. By modeling a standard type Ia supernova hitting a shell of circumstellar material, we produce a light curve and late-time iron-dominated spectrum that match the observations of SN 2006gy. In such a scenario, common envelope evolution of a progenitor binary system can synchronize envelope ejection and supernova explosion and may explain these bright transients.
RESUMO
Type Ic supernovae, the explosions after the core collapse of massive stars that have previously lost their hydrogen and helium envelopes, are particularly interesting because of their link with long-duration gamma ray bursts. Although indications exist that these explosions are aspherical, direct evidence has been missing. Late-time observations of supernova SN 2003jd, a luminous type Ic supernova, provide such evidence. Recent Subaru and Keck spectra reveal double-peaked profiles in the nebular lines of neutral oxygen and magnesium. These profiles are different from those of known type Ic supernovae, with or without a gamma ray burst, and they can be understood if SN 2003jd was an aspherical axisymmetric explosion viewed from near the equatorial plane. If SN 2003jd was associated with a gamma ray burst, we missed the burst because it was pointing away from us.