785 research outputs found
Optical observations of the fast declining type Ib supernova iPTF13bvn
We present optical UBVRI photometry and medium resolution spectroscopy of the
type Ib supernova iPTF13bvn, spanning a phase of d to d
with respect to -band maximum. The post maximum decline rates indicate a
fast decline with . Correcting for a galactic
extinction and host galaxy extinction of
, the absolute -band magnitude peaks at
M. The bolometric light curve indicates that M of Ni was synthesized in the explosion. The earliest
spectrum (d) shows the presence of He~{\sc i} 5876 \AA\ feature at a
velocity of 15000 km s, which falls rapidly by the time the SN
approaches the epoch of B-band maximum. The photospheric velocity near maximum
light, as indicated by the Fe~{\sc ii} 5169~\AA\ feature, is km
s. The estimate for the Ni mass, together with the estimates for
the ejected mass () and kinetic energy of the explosion
() indicate that iPTF13bvn is a low luminosity type Ib supernova,
with a lower than average ejected mass and kinetic energy. Our results suggest
that the progenitor of iPTF13bvn is inconsistent with a single Wolf-Rayet star.Comment: Accepted for publication in MNRAS, 11 pages, 12 figure
One year of monitoring of the Type IIb supernova SN 2011dh
Optical photometry and low resolution spectroscopy of the type IIb
supernova SN 2011dh in M51 are presented, covering the first year after the
explosion. The light curve and spectral evolution are discussed. The early
phase light curve evolution of SN 2011dh is very similar to SN 1993J and SN
2008ax. In the late phase, however, SN 2011dh declines faster than SN 1993J.
The late phase decline in the -band is steeper than in the and
bands, indicating the possibility of dust formation. With a peak -band
absolute magnitude of mag, SN 2011dh is a marginally
faint type IIb event. The reddening corrected colour curves of SN 2011dh are
found to be redder than other well studied type IIb supernovae. The bolometric
light curve indicates 0.09 M of Ni is synthesized during
the explosion. The HeI lines were detected in the spectra during the rise to
maximum. The nebular spectra of SN 2011dh show a box shaped emission in the red
wing of the [OI] 6300-6363 \AA\ feature, that is attributed to H
emission from a shock excited circumstellar material. The analysis of nebular
spectra indicates that M of oxygen was ejected during the
explosion. Further, the [CaII]/[OI] line ratio in the nebular phase is
0.7, indicating a progenitor with a main sequence mass of 10-15 M.Comment: Accepted for publication in MNRA
Supernova SN 2012dn: A spectroscopic clone of SN 2006gz
We present optical and UV analysis of the luminous type Ia supernova SN
2012dn covering the period 11 to +109 days with respect to the band
maximum, that occurred on JD 2456132.89 0.19, with an apparent magnitude
of = 14.38 0.02. The absolute magnitudes at maximum in
and bands are and
, respectively. SN 2012dn is marginally
luminous compared to normal type Ia supernovae. The peak bolometric luminosity
of erg s suggests that
M of Ni was synthesized in the explosion. The
decline rate mag is lower than
that of normal type Ia supernovae, and similar to the luminous SN 1991T.
However, the photometric and spectroscopic behaviour of SN 2012dn is different
from that of SN 1991T. Early phase light curves in and bands are very
broad. The band peak has a plateau-like appearance similar to the
super-Chandra SN 2009dc. Pre-maximum spectra show clear evidence of C\,{\sc ii}
6580 \AA\, line, indicating the presence of unburned materials. The velocity
evolution of C\,{\ sc ii} line is peculiar. Except for the very early phase
(13 d), the C\,{\sc ii} line velocity is lower than the velocity
estimated using the Si\,{\sc ii} line. During the pre-maximum and close to
maximum phase, to reproduce observed shape of the spectra, the synthetic
spectrum code {\sc syn++} needs significantly higher blackbody temperature than
those required for normal type Ia events. The photospheric velocity evolution
and other spectral properties are similar to those of the carbon-rich SN
2006gz.Comment: Accepted for publication in MNRAS, 19 pages, 20 figure
Religious Philosophy of Guru Nanak: Literary Speculation
India has been a land of diverse culture and traditions. When we say culture it includes many things like language, social customs, food habits, religion and so on. Of this religion seems to be the most influential factor in the life of an individual. It is something which lends meaning and purpose to our life. It is that which binds human beings to the Divine. And this bond can be established through the practise of Bhakti. The concept of Bhakti is an old one. It emphasises devotion to the personal God. Bhakti movement is an important development in the cultural history of India which originated in the south. The saints of Bhakti movement preached personal devotion to God as a means of attaining Salvation. They made use of local language to spread the ideology of Bhakti. Guru Nanak is one of the most influential saints of the Bhakti movement. In his teaching he incorporated ideas both from Hinduism as well as Islam. He revealed the truth of monotheism, importance of the recitation of God’s name with utmost devotion, need of a Guru for salvation. He tried to bridge the gap between the two communities of Islam and Hinduism and eradicate social problems by focusing on the truth of monotheism and the concept of equality
Further evidence for intra-night optical variability of radio-quiet quasars
Although well established for BL Lac objects and radio-loud quasars, the
occurrence of intra-night optical variability (INOV) in radio-quiet quasars is
still debated, primarily since only a handful of INOV events with good
statistical significance, albeit small amplitude, have been reported so far.
This has motivated us to continue intra-night optical monitoring of bona-fide
radio-quiet quasars (RQQs). Here we present the results for a sample of 11 RQQs
monitored by us on 19 nights. On 5 of these nights a given RQQ was monitored
simultaneously from two well separated observatories. In all, two clear cases
and two probable case of INOV were detected. From these data, we estimate an
INOV duty cycle of 8% for RQQs which would increase to 19% if the
`probable variable' cases are also included. Such comparatively small INOV duty
cycles for RQQs, together with the small INOV amplitudes (1%), are in
accord with the previously deduced characteristics of this phenomenon.Comment: 15 Pages, 4 Tables, 24 Figures; Accepted in BAS
ASASSN-14dq: A fast-declining type II-P Supernova in a low-luminosity host galaxy
Optical broadband (UBVRI) photometric and low-resolution spectroscopic
observations of the type II-P supernova (SN) ASASSN-14dq are presented.
ASASSN-14dq exploded in a low-luminosity/metallicity host galaxy UGC 11860, the
signatures of which are present as weak iron lines in the photospheric phase
spectra. The SN has a plateau duration of 90 d, with a plateau decline
rate of 1.38 in V-band which is higher than most type
II-P SNe. ASASSN-14dq is a luminous type II-P SN with a peak -band absolute
magnitude of -17.70.2 mag. The light curve of ASASSN-14dq indicates it
to be a fast-declining type II-P SN, making it a transitional event between the
type II-P and II-L SNe. The empirical relation between the steepness parameter
and mass for type II SNe was rebuilt with the help of
well-sampled light curves from the literature. A mass of
0.029 M was estimated for ASASSN-14dq, which is slightly
lower than the expected mass for a luminous type II-P SN. Using
analytical light curve modelling, a progenitor radius of cm, an ejecta mass of and a total
energy of ergs was estimated for this event. The
photospheric velocity evolution of ASASSN-14dq resembles a type II-P SN, but
the Balmer features (H and H) show relatively slow velocity
evolution. The high-velocity H feature in the plateau phase, the
asymmetric H emission line profile in the nebular phase and the
inferred outburst parameters indicate an interaction of the SN ejecta with the
circumstellar material (CSM).Comment: 28 pages, 29 figures, Accepted in MNRA
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