5 research outputs found
Spectroscopic observations of novae V1065 CEN and V1280 SCO using 45 cm cassegrain telescope at Arthur C Clarke Institute
The spectroscopic observations of two novae namely V1065 CEN and V1280 SCO
were made by 45 cm Cassegrain telescope in high resolution
(=22000) at H (6563 \r{A}) region. V1065 CEN is
He/N-type spectra which characterize a broad (Gaussian FWHM 49 \r{A}), saddle
shaped and asymmetric H emission line without prominent P-Cyg
absorption component. Completely different H profile of V1280 SCO shows
prominent P-Cyg absorption and narrow emission line (Gaussian FWHM 26 \r{A})
which can be classified as Fe II type nova. The expansion velocities of these
two systems measured from the minima of the P-Cyg profiles are close to 2300
km/s for V1065 CEN, and 716 km/s for V1280 SCO. Based on the photometric
analysis, the Nova V1065 CEN can be classified as fast (11t25)
nova. The derived absolute magnitudes at maximum for nova V1065 CEN to be
M = -7.580.18 and M= -7.750.25 correspond to a
distance 8.510.33 kpc. The parameters t=12 days and t=14
days of nova V1280 SCO determine that the nova is in between very fast and fast
nova. The mean absolute magnitude at maximum is calculated to be
M=-8.70.1 and the estimated distance to the nova V1280 SCO is
3.20.2 kpc
Measuring the Solar Radius from Space during the 2003 and 2006 Mercury Transits
The Michelson Doppler Imager (MDI) aboard the Solar and Heliospheric
Observatory observed the transits of Mercury on 2003 May 7 and 2006 November 8.
Contact times between Mercury and the solar limb have been used since the 17th
century to derive the Sun's size but this is the first time that high-quality
imagery from space, above the Earth's atmosphere, has been available. Unlike
other measurements this technique is largely independent of optical distortion.
The true solar radius is still a matter of debate in the literature as measured
differences of several tenths of an arcsecond (i.e., about 500 km) are
apparent. This is due mainly to systematic errors from different instruments
and observers since the claimed uncertainties for a single instrument are
typically an order of magnitude smaller. From the MDI transit data we find the
solar radius to be 960".12 +/- 0".09 (696,342 +/- 65 km). This value is
consistent between the transits and consistent between different MDI focus
settings after accounting for systematic effects.Comment: Accepted for publication in The Astrophysical Journal (2012 March 5
The Measurement of Solar Diameter and Limb Darkening Function with the Eclipse Observations
The Total Solar Irradiance varies over a solar cycle of 11 years and maybe
over cycles with longer period. Is the solar diameter variable over time too?
We introduce a new method to perform high resolution astrometry of the solar
diameter from the ground, through the observations of eclipses by reconsidering
the definition of the solar edge. A discussion of the solar diameter and its
variations must be linked to the Limb Darkening Function (LDF) using the
luminosity evolution of a Baily's Bead and the profile of the lunar limb
available from satellite data. This approach unifies the definition of solar
edge with LDF inflection point for eclipses and drift-scan or heliometric
methods. The method proposed is applied for the videos of the eclipse in 15
January 2010 recorded in Uganda and in India. The result shows light at least
0.85 arcsec beyond the inflection point, and this suggests to reconsider the
evaluations of the historical eclipses made with naked eye.Comment: 16 pages, 11 figures, accepted in Solar Physics. arXiv admin note:
text overlap with arXiv:astro-ph/0601109 by other author