131 research outputs found
Early time optical spectroscopy of supernova SN 1998S
We present medium-resolution optical spectra of the type II supernova SN 1998S obtained during the pre-maximum, maximum and early decline phases. The early decline spectra show complex Balmer line profiles: a narrow P-Cygni emission feature superimposed on a broad emission. The narrow emission has a redshift similar to that of the host galaxy, indicating its origin from a pre-supernova circumstellar material. The Hα luminosity of the broad component implies a shell mass of ~ 0.1 M☉ for the supernova ejecta, while the luminosity of the narrow component implies a mass loss rate of 10-4M☉ yr-1 for the precursor. The photospheric temperature of the supernova shell decreased from a value of 18400±2900 K on day 17 to a value of 7500±1200 K on day 44. The observations indicate SN 1998S belongs to type IIn supernovae where the supernova ejecta dynamically interact with a pre-supernova circumstellar material
Availability and Usage of Information Sources and Services at Select Media Libraries in Delhi Region: A Study
Information is a basic need of today’s fast changing world important for one’s day to day life. People need information to efficiently carry out work in their respective fields. Media professionals working in Media organisations needs current, authoritative and factual information to construct news and programmes. Such information is made available by Media libraries in the shortest time frame to meet the targets of the Media Professionals. The information is collected from the printed as well from the electronic resources available in the Media libraries.
In view of the remarkable contribution made by the media libraries, the present research has been conceive with the broad objective of studying the adequacy and availability of information sources and how optimally the same has been used by the users. The study is confined to two Media Libraries such as The Indian Institute of Mass Communication Media Library and Anwar Jamal Kidwai Mass communication Research Centre Media Library in the NCT of Delhi have been taken for research investigation. The study adopted the survey method and data was gathered through close ended questionnaire and through in-depth personal interviews with the Media Professionals and media library staff. Two separate sets of questionnaire were used to elicit the desired information.
The Research investigation highlighted survey findings in term of availability of sources in two media libraries. Apart from media professionals and media librarians, the library use pattern, e-resources use pattern, library visit pattern and the problems encounter by media professionals in accessing the information sources etc. were highlighted. At the end, the researcher made some suggestions and important recommendations for the overall improvement in providing quality services to the users
Supernovae study: Context of the 4-m ILMT facility
The upcoming 4-m International Liquid Mirror Telescope (ILMT) facility will
perform deep imaging (in single scan 22 mag.) of a narrow strip of
sky each clear night in the Time Delayed Integration mode. A cadence of one day
observation will provide unique opportunities to discover different types of
supernovae (SNe) along with many other types of variable sources. We present
the approach to discover SNe with the ILMT and discuss the follow-up strategy
in the context of other existing observational facilities. The advantages of
the ILMT observations over the traditional glass mirror telescopes are also
discussed.Comment: 8 pages, 3 figures, to appear in proceedings of the First
Belgo-Indian Network for Astronomy & Astrophysics (BINA) Worksho
Optical observations of the bright long duration peculiar GRB 021004 afterglow
The CCD magnitudes in Johnson and Cousins and photometric
passbands are determined for the bright long duration GRB 021004 afterglow from
2002 October 4 to 16 starting 3 hours after the ray burst.
Light curves of the afterglow emission in ,, and passbands are
obtained by combining these measurements with other published data. The
earliest optical emission appears to originate in a revese shock. Flux decay of
the afterglow shows a very uncommon variation relative to other well-observed
GRBs. Rapid light variations, especially during early times (
days) is superposed on an underlying broken power law decay typical of a jetted
afterglow. The flux decay constants at early and late times derived from least
square fits to the light curve are and respectively,
with a jet break at around 7 day. Comparison with a standard fireball model
indicates a total extinction of mag in the direction of the
burst. Our low-resolution spectra corrected for this extinction provide a
spectral slope . This value and the flux decay constants
agree well with the electron energy index used in the model. The
derived jet opening angle of about implies a total emitted
gamma-ray energy erg at a cosmological distance
of about 20 Gpc. Multiwavelength observations indicate association of this GRB
with a star forming region, supporting the case for collapsar origin of long
duration GRBs.Comment: 19 pages, 3 figures, BASI, 31, 1
The zenithal 4-m International Liquid Mirror Telescope: a unique facility for supernova studies
The 4-m International Liquid Mirror Telescope (ILMT) will soon become
operational at the newly developed Devasthal observatory near Nainital
(Uttarakhand, India). Coupled with a 4k 4k pixels CCD detector and TDI
optical corrector, it will reach approximately 22.8, 22.3 and 21.4 magnitude in
the , and spectral bands, respectively in a single scan. The
limiting magnitudes can be further improved by co-adding the consecutive night
images in particular filters. The uniqueness to observe the same sky region by
looking towards the zenith direction every night, makes the ILMT a unique
instrument to detect new supernovae (SNe) by applying the image subtraction
technique. High cadence (24 hours) observations will help to construct
dense sampling multi-band SNe light curves. We discuss the importance of the
ILMT facility in the context of SNe studies. Considering the various plausible
cosmological parameters and observational constraints, we perform detailed
calculations of the expected SNe rate that can be detected with the ILMT in
different spectral bands.Comment: 11 pages, 6 figures, 3 tables, accepted for publication in MNRA
SN 2002ap, the hypernova of class Ic
The supernova SN 2002ap was discovered in the outer regions of the nearby
spiral M74 on January 29.4 UT. Early photometric and spectroscopic observations
indicate the supernova belongs to the class of Ic hypernova. Late time (After
JD 2452500) light curve decay slopes are similar to that of the hypernovae SN
1997ef and SN 1998bw. We present here the photometric light curves and
colour evolutions of SN 2002ap to investigate the late time nature of the light
curve.Comment: 2 pages,1 figure, Poster contribution, Submitted to proceedings of
Astronomical Society of India (ASI) meeting, 200
Optical afterglow of the not so dark GRB 021211
We determine Johnson and Cousins photometric CCD magnitudes for
the afterglow of GRB 021211 during the first night after the GRB trigger. The
afterglow was very faint and would have been probably missed if no prompt
observation had been conducted. A fraction of the so-called ``dark'' GRBs may
thus be just ``optically dim'' and require very deep imaging to be detected.
The early-time optical light curve reported by other observers shows prompt
emission with properties similar to that of GRB 990123. Following this, the
afterglow emission from min to days after the burst is
characterized by an overall power-law decay with a slope in the
passband. We derive the value of spectral index in the optical to near-IR
region to be 0.60.2 during 0.13 to 0.8 day after the burst. The flux decay
constant and the spectral slope indicate that optical observations within a day
after the burst lies between cooling frequency and synchrotron maximum
frequency.Comment: 4 pages, 2 figures, A&A Letters, 408, L2
A flattening in the Optical Light Curve of SN 2002ap
We present the broad band optical photometry of the Type Ic
supernova SN 2002ap obtained during 2002 February 06 -- March 23 in the early
decline phases and also later on 2002 15 August. Combining these data with the
published ones, the general light curve development is studied. The time and
luminosity of the peak brightness and the peak width are estimated. There is a
flattening in the optical light curve about 30 days after the maximum. The
flux decline rates before flattening are 0.1270.005, 0.0820.001,
0.0740.001, 0.0620.001 and 0.0400.001 mag day in ,
, , and passbands respectively, while the corresponding
values after flattening are about 0.02 mag day in all the passbands. The
maximum brightness of SN 2002ap mag, is comparable to that of
the type Ic 1997ef, but fainter than that of the type Ic hypernova SN 1998bw.
The peak luminosity indicates an ejection of 0.06 M
Ni mass.
We also present low-resolution optical spectra obtained during the early
phases.
The SiII absorption minimum indicates that the photospheric velocity
decreased from
21,360 km s to 10,740 km s during a period of 6
days.Comment: 7 pages, 5 figures, Submitted to MNRA
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