19 research outputs found
Optical spectroscopic and polarization properties of 2011 outburst of the recurrent nova T Pyxidis
We study the spectroscopic and ionized structural evolution of T Pyx during
its 2011 outburst, and also study the variation in degree of polarization
during its early phase. Optical spectroscopic data of this system obtained from
day 1.28--2415.62 since discovery, and optical, broadband imaging polarimetric
observations obtained from day 1.36--29.33 during the early phases of the
outburst are used in the study. The physical conditions and the geometry of the
ionized structure of the nova ejecta has been modelled for a few epochs using
the photo-ionization code, CLOUDY in 1D and pyCloudy in 3D. The spectral
evolution of the nova ejecta during its 2011 outburst is similar to that of the
previous outbursts. The variation in the line profiles is seen very clearly in
the early stages due to good coverage during this period. The line profiles
vary from P-Cygni (narrower, deeper and sharper) to emission profiles which are
broader and structured, which later become narrower and sharper in the late
post-outburst phase. The average ejected mass is estimated to be . The ionized structure of the ejecta is found to
be a bipolar conical structure with equatorial rings, with a low inclination
angle of .Comment: 14 pages, 12 figures, accepted in A&
Analysis of polarization introduced due to the telescope optics of the Thirty Meter Telescope
An analytical model has been developed to estimate the polarization effects, such as instrumental polarization (IP), crosstalk (CT), and depolarization, due to the optics of the Thirty Meter Telescope. These are estimated for the unvignetted field-of-view and the wavelengths of interest. The model estimates an IP of 1.26% and a CT of 44% at the Nasmyth focus of the telescope at the wavelength of 0.6 μm at field angle zero with the telescope pointing to zenith. Mueller matrices have been estimated for the primary, secondary, and Nasmyth mirrors. It is found that some of the Mueller matrix elements of the primary and secondary mirrors show a fourfold azimuthal antisymmetry, which indicates that the polarization at the Cassegrain focus is negligible. At the inclined Nasmyth mirror, there is no azimuthal antisymmetry in the matrix elements, and this results in nonzero values for IP and CT, which would negatively impact the polarization measurements at the telescope focus. The averaged Mueller matrix is estimated at the Nasmyth focus at different instrument ports and various zenith angles of the telescope. The variation in the Mueller matrix elements for different coatings is also estimated. The impact of this polarization effect on the science case requirements has been discussed. This analysis will help in achieving precise requirements for future instruments with polarimetric capability
Estimation of polarization aberrations and its effect on the point spread function of the Thirty Meter Telescope
The Thirty Meter Telescope (TMT) is a future generation telescope proposed to be located in Mauna Kea, Hawaii or in La Palma in the Canary Islands. The telescope will have a segmented primary and an inclined tertiary mirror. The segmentation of the primary mirror and the inclination in the tertiary mirror can introduce significant polarization aberrations. Typically, the polarization aberrations, introduced due to the mirror coating and the high incident angles cause small modifications to the Point Spread Function (PSF). Here, we perform the polarization ray tracing for TMT using the optical design software Zemax for different input polarizations for a point source (on-axis). We calculate the diattenuation and retardance aberration maps for all the three mirrors of TMT. The coating induced astigmatism obtained from the retardance of the primary and secondary mirror is found to be of the order of 0.048 radians, whereas, the polarization induced tilt by the retardance of the tertiary mirror is in the order of 0.29 radians. The Jones pupil maps are estimated at two of the instrument ports, Wide Field Optical Spectrograph (WFOS) and Narrow Field Infrared Adaptive Optics System (NFIRAOS).The Amplitude Response Matrix (ARM) estimated at the WFOS port show the presence of ghost PSF's. The magnitude of the ghost PSF components is of the order of 2.5 x 10^(-5) at 1μm at WFOS port. The ARM and the Point Spread Matrix (PSM) are estimated at the focus of the NFIRAOS instrument. The Stokes PSF is shown for horizontal and vertical polarization as inputs. The Huygen's point spread function obtained from Zemax shows the variations in FWHM for unpolarized and polarized inputs. These estimations would help in the design aspects of a high contrast imaging instrument for the TMT in the future
NMF-based GPU accelerated coronagraphy pipeline
We present a generalized Non-negative factorization (NMF)-based data
reduction pipeline for circumstellar disk and exoplanet detection. By using an
adaptable pre-processing routine that applies algorithmic masks and corrections
to improper data, we are able to easily offload the computationally-intensive
NMF algorithm to a graphics processing unit (GPU), significantly increasing
computational efficiency. NMF has been shown to better preserve disk structural
features compared to other post-processing approaches and has demonstrated
improvements in the analysis of archival data. The adaptive pre-processing
routine of this pipeline, which automatically aligns and applies image
corrections to the raw data, is shown to significantly improve chromatic halo
suppression. Utilizing HST-STIS and JWST-MIRI coronagraphic datasets, we
demonstrate a factor of five increase in real-time computational efficiency by
using GPUs to perform NMF compared to using CPUs. Additionally, we demonstrate
the usefulness of higher numbers of NMF components with SNR and contrast
improvements, which necessitates the use of a more computationally efficient
approach for data reduction
Polarimetric modeling and assessment of science cases for Giant Magellan Telescope-Polarimeter (GMT-Pol)
Polarization observations through the next-generation large telescopes will
be invaluable for exploring the magnetic fields and composition of jets in AGN,
multi-messenger transients follow-up, and understanding interstellar dust and
magnetic fields. The 25m Giant Magellan Telescope (GMT) is one of the
next-generation large telescopes and is expected to have its first light in
2029. The telescope consists of a primary mirror and an adaptive secondary
mirror comprising seven circular segments. The telescope supports instruments
at both Nasmyth as well as Gregorian focus. However, none of the first or
second-generation instruments on GMT has the polarimetric capability. This
paper presents a detailed polarimetric modeling of the GMT for both Gregorian
and folded ports for astronomical B-K filter bands and a field of view of 5 arc
minutes. At 500nm, The instrumental polarization is 0.1% and 3% for the
Gregorian and folded port, respectively. The linear to circular crosstalk is
0.1% and 30% for the Gregorian and folded ports, respectively. The Gregorian
focus gives the GMT a significant competitive advantage over TMT and ELT for
sensitive polarimetry, as these telescopes support instruments only on the
Nasmyth platform. We also discuss a list of polarimetric science cases and
assess science case requirements vs. the modeling results. Finally, we discuss
the possible routes for polarimetry with GMT and show the preliminary optical
design of the GMT polarimeter.Comment: 13 pages, 5 figures,SPIE Optics + Photonics 2023 conference
proceeding, Paper no 12690-2
Analysis of polarization introduced due to the telescope optics of the Thirty Meter Telescope
An analytical model has been developed to estimate the polarization effects, such as instrumental polarization (IP), crosstalk (CT), and depolarization, due to the optics of the Thirty Meter Telescope. These are estimated for the unvignetted field-of-view and the wavelengths of interest. The model estimates an IP of 1.26% and a CT of 44% at the Nasmyth focus of the telescope at the wavelength of 0.6 μm at field angle zero with the telescope pointing to zenith. Mueller matrices have been estimated for the primary, secondary, and Nasmyth mirrors. It is found that some of the Mueller matrix elements of the primary and secondary mirrors show a fourfold azimuthal antisymmetry, which indicates that the polarization at the Cassegrain focus is negligible. At the inclined Nasmyth mirror, there is no azimuthal antisymmetry in the matrix elements, and this results in nonzero values for IP and CT, which would negatively impact the polarization measurements at the telescope focus. The averaged Mueller matrix is estimated at the Nasmyth focus at different instrument ports and various zenith angles of the telescope. The variation in the Mueller matrix elements for different coatings is also estimated. The impact of this polarization effect on the science case requirements has been discussed. This analysis will help in achieving precise requirements for future instruments with polarimetric capability
Estimation of polarization aberrations and their effect on the coronagraphic performance for future space telescopes
A major goal of proposed future space observatories, such as the Habitable
World Observatory, is to directly image and characterize Earth-like planets
around Sun-like stars to search for habitability signatures requiring the
starlight suppression (contrast) of 1e-10. One of the significant aspects
affecting this contrast is the polarization aberrations generated from the
reflection from mirror surfaces. The polarization aberrations are the
phase-dependent amplitude and phase patterns originating from the Fresnel
reflections of the mirror surfaces. These aberrations depend on the angle of
incidence and coating parameters of the surface. This paper simulates the
polarization aberrations for an on-axis and off-axis TMA telescope of a 6.5 m
monolithic primary mirror. We analyze the polarization aberrations and their
effect on the coronagraphic performance for eight different recipes of mirror
coatings for Astronomical filter bands g-I: three single-layer metal coatings
and five recipes of protective coatings. First, the Jones pupils are estimated
for each coating and filter band using the polarization ray tracing in Zemax.
Then, we propagate these Jones pupils through a Vector Vortex Coronagraph and
Perfect Coronagraphs using hcipy, a physical optics-based simulation framework.
The analysis shows that the two main polarization aberrations generated from
the four mirrors are the retardance-defocus and retardance-tilt. The
simulations also show that the coating plays a significant role in determining
the strength of the aberrations. The bare/oxi-aluminum and Al+18nm LiF coating
outperforms all the other coatings by one order of magnitude.Comment: 13 pages, 11 figures, SPIE Optics+Photonics 2023 proceeding, Paper
no: 12680-2
Analytical Modelling of Thirty Meter Telescope Optics Polarization
The polarization introduced due to Thirty Meter Telescope (TMT) optics is calculated using an analytical model. Mueller matrices are also generated for each optical element using Zemax, based on which the instrumental polarization due to the entire system at the focal plane is estimated and compared with the analytical model. This study is significant in the estimation of the telescope sensitivity and also has great implications for future instruments
Poke: An open-source ray-based physical optics platform
Integrated optical models allow for accurate prediction of the as-built
performance of an optical instrument. Optical models are typically composed of
a separate ray trace and diffraction model to capture both the geometrical and
physical regimes of light. These models are typically separated across both
open-source and commercial software that don't interface with each other
directly. To bridge the gap between ray trace models and diffraction models, we
have built an open-source optical analysis platform in Python called Poke that
uses commercial ray tracing APIs and open-source physical optics engines to
simultaneously model scalar wavefront error, diffraction, and polarization.
Poke operates by storing ray data from a commercial ray tracing engine into a
Python object, from which physical optics calculations can be made. We present
an introduction to using Poke, and highlight the capabilities of two new
propagation physics modules that add to the utility of existing scalar
diffraction models. Gaussian Beamlet Decomposition is a ray-based approach to
diffraction modeling that allows us to integrate physical optics models with
ray trace models to directly capture the influence of ray aberrations in
diffraction simulations. Polarization Ray Tracing is a ray-based method of
vector field propagation that can diagnose the polarization aberrations in
optical systems. Poke has been recently used to study the next generation of
astronomical observatories, including the ground-based Extremely Large
Telescopes and a 6 meter space telescope early concept for NASA's Habitable
Worlds Observatory.Comment: 11 Pages, 9 Figures, Published in Proceedings of SPIE Optical
Modeling and Performance Predictions XIII Paper 12664-
RZ Piscium Hosts a Compact and Highly Perturbed Debris Disk
RZ Piscium (RZ Psc) is well-known in the variable star field because of its
numerous, irregular optical dips in the past five decades, but the nature of
the system is heavily debated in the literature. We present multiyear infrared
monitoring data from Spitzer and WISE to track the activities of the inner
debris production, revealing stochastic infrared variability as short as weekly
timescales that is consistent with destroying a 90-km-size asteroid every year.
ALMA 1.3 mm data combined with spectral energy distribution modeling show that
the disk is compact (0.1--13 au radially) and lacks cold gas. The disk is
found to be highly inclined and has a significant vertical scale height. These
observations confirm that RZ Psc hosts a close to edge-on, highly perturbed
debris disk possibly due to migration of recently formed giant planets which
might be triggered by the low-mass companion RZ Psc B if the planets formed
well beyond the snowlines.Comment: 16 pages, 5 figures, accepted for publication in Ap