Abstract
RZ Piscium (RZ Psc) is well known in the variable star field because of its numerous irregular optical dips in the past 5 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 sized 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 that might be triggered by the low-mass companion RZ Psc B if the planets formed well beyond the snowlines.
Aims. We aim to 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. Methods. ...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 were used in the study. The physical conditions and the geometry of the ionized structure of the nova ejecta was modelled for a few epochs using the photo-ionization code, CLOUDY in 1D and pyCloudy in 3D. Results. 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 that are broader and structured, which later become narrower and sharper in the late post-outburst phase. The average ejected mass is estimated to be 7.03 × 10−6 M⊙. The ionized structure of the ejecta is found to be a bipolar conical structure with equatorial rings, with a low inclination angle of 14.75 ° ±0.65°.
High-cadence ultraviolet, optical, and near-infrared photometric and low-resolution spectroscopic observations of the peculiar Type II supernova (SN) 2018hna are presented. The early-phase multiband ...light curves (LCs) exhibit the adiabatic cooling envelope emission following the shock breakout up to ∼ 14 days from the explosion. SN 2018hna has a rise time of ∼ 88 days in the V band, similar to SN 1987A. A 56Ni mass of ∼0.087 0.004 M is inferred for SN 2018hna from its bolometric LC. Hydrodynamical modeling of the cooling phase suggests a progenitor with a radius ∼50 R , a mass of ∼14-20 M , and an explosion energy of ∼1.7-2.9 × 1051 erg. The smaller inferred radius of the progenitor than a standard red supergiant is indicative of a blue supergiant progenitor of SN 2018hna. A subsolar metallicity (∼0.3 Z ) is inferred for the host galaxy UGC 07534, concurrent with the low-metallicity environments of 1987A-like events.
In polarimetric observations of astronomical sources, instrumental polarization and crosstalk from the telescope optics affect the measurements. They arise due to the reflections from the mirror ...surfaces of the telescope. An analytical model was developed to estimate these values for the Thirty Meter Telescope. The model determines an instrumental polarization of 1.2% and crosstalk of 40% at a wavelength of 0.6 μm. The analyses indicated that the Nasmyth (tertiary) mirror of the telescope, (used to fold and steer the light to the various instrument ports) is the primary source of the high values of instrumental polarization and crosstalk. We present here, a possible optical layout to cancel out the effects introduced by the Nasmyth mirror. Different configurations are studied to reduce/cancel the effect of the IP and crosstalk before the light from the Nasmyth mirror, reaches the instrument. While the optical components introduced after the tertiary mirror reduce the telescope instrumental polarization and cross talk, it leads to a reduction in the intensity due to additional reflections.
Context.
Next-generation large segmented mirror telescopes are expected to perform direct imaging and characterization of Earth-like rocky planets, which requires contrast limits of 10
−7
to 10
−8
at ...wavelengths from
I
to
J
band. One critical aspect affecting the raw on-sky contrast are polarization aberrations (i.e., polarization-dependent phase and amplitude patterns in the pupil) arising from the reflection from the telescope’s mirror surfaces and instrument optics. These polarization aberrations induce false signals for polarimetry that can be calibrated to a certain degree, but they can also fundamentally limit the achievable contrast of coronagraphic systems.
Aims.
We simulate the polarization aberrations and estimate their effect on the achievable contrast for three next-generation ground-based large segmented mirror telescopes.
Methods.
We performed ray-tracing in Zemax
®
and computed the polarization aberrations and Jones pupil maps using the polarization ray-tracing algorithm. The impact of these aberrations on the contrast is estimated by propagating the Jones pupil maps through a set of idealized coronagraphs using hcipy, a physical optics-based simulation framework.
Results.
The optical modeling of the giant segmented mirror telescopes (GSMTs) shows that polarization aberrations create significant leakage through a coronagraphic system. The dominant aberration is retardance defocus, which originates from the steep angles on the primary and secondary mirrors. The retardance defocus limits the contrast to 10
−5
to 10
−4
at 1
λ
/
D
at visible wavelengths, and 10
−5
to 10
−6
at infrared wavelengths. The simulations also show that the coating plays a major role in determining the strength of the aberrations.
Conclusions.
Polarization aberrations will need to be considered during the design of high-contrast imaging instruments for the next generation of extremely large telescopes. This can be achieved either through compensation optics, robust coronagraphs, specialized coatings, calibration, and data analysis approaches, or by incorporating polarimetry with high-contrast imaging to measure these effects.
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