Photometric observations of the supernova 2009nr

We present the results of our UBVRI CCD photometry for the second brightest supernova of 2009, SN 2009nr, discovered during a sky survey with the telescopes of the MASTER robotic network. Its light and color curves and bolometric light curves have been constructed. The light-curve parameters and the maximum luminosity have been determined. SN 2009nr is shown to be similar in light-curve shape and maximum luminosity to SN 1991T, which is the prototype of the class of supernovae Ia with an enhanced luminosity. SN 2009nr exploded far from the center of the spiral galaxy UGC 8255 and most likely belongs to its old halo population. We hypothesize that this explosion is a consequence of the merger of white dwarfs

Peculiar velocities of supernovae Ia in clusters of galaxies

Наблюдения сверхновых Ia позволяют оценить значения космологических параметров при помощи диаграммы Хаббла. В первую очередь такие наблюдения дают значение постоянной Хаббла, которая является одним из основных космологических параметров. Повышение точности измерений данной величины представляет важную задачу для современной космологии, поэтому необходимо учитывать влияние пекулярных скоростей сверхновых на измерение красного смещения, используемое при построении диаграммы Хаббла. Мы изучаем вклад пекулярных скоростей, обусловленных движением родительских галактик в поле тяготения скопления галактик, для космологической выборки сверхновых Pantheon.Observations of supernovae Ia make it possible to estimate the values of cosmological parameters using the Hubble diagram. First of all, such observations give us a value of the Hubble constant, which is one of the most important cosmological parameters. Improving the accuracy of measurements of this parameter is a priority for modern cosmological analysis. Therefore, it is necessary to take into account the influence of the peculiar velocities of supernovae Ia on the measurement of the redshift, which is used in constructing the Hubble diagram. We study the contribution of peculiar velocities due to the motion of host galaxies in the gravitational field of galaxy clusters for a cosmological sample of supernovae Pantheon.Е. А. Б. благодарит Фонд развития теоретической физики и математики «БАЗИС» 20-2-1-34-1. Исследование выполнено при поддержке Междисциплинарной научно-образовательной школы Московского университета «Фундаментальные и прикладные исследования космоса»

Optical polarization observations with the MASTER robotic net

We present results of optical polarization observations performed with the MASTER robotic net for three types of objects: gamma-ray bursts, supernovae, and blazars. For the Swift gamma-ray bursts GRB100906A, GRB110422A, GRB121011A, polarization observations were obtained during very early stages of optical emission. For GRB100906A it was the first prompt optical polarization observation in the world. Photometry in polarizers is presented for Type Ia Supernova 2012bh during 20 days, starting on March 27, 2012. We find that the linear polarization of SN 2012bh at the early stage of the envelope expansion was less than 3%. Polarization measurements for the blazars OC 457, 3C 454.3, QSO B1215+303, 87GB 165943.2+395846 at single nights are presented. We infer the degree of the linear polarization and polarization angle. The blazars OC 457 and 3C 454.3 were observed during their periods of activity. The results show that MASTER is able to measure substantially polarized light; at the same time it is not suitable for determining weak polarization (less than 5%) of dim objects (fainter than 16$^m$). Polarimetric observations of the optical emission from gamma-ray bursts and supernovae are necessary to investigate the nature of these transient objects.Comment: 31 pages, 12 figures, 4 tables; Exposure times in Table 2 have been correcte

`Pure' Supernovae and Accelerated Expansion of the Universe

A special class of type Ia supernovae that is not subject to ordinary and additional intragalactic gray absorption and chemical evolution has been identified. Analysis of the Hubble diagrams constructed for these supernovae confirms the accelerated expansion of the Universe irrespective of the chemical evolution and possible gray absorption in galaxies.Comment: 2 figures, 1 tabl