Slit Spectrograph Research Articles

Monitoring AGNs with Hβ Asymmetry. IV. First Reverberation Mapping Results of 14 Active Galactic Nuclei

We report first-time reverberation-mapping results for 14 active galactic nuclei (AGNs) from the ongoing Monitoring AGNs with Hβ Asymmetry campaign (MAHA). These results utilize optical spectra obtained with the Long Slit Spectrograph on the Wyoming Infrared 2.3 m Telescope between 2017 November and 2023 May. MAHA combines long-duration monitoring with high cadence. We report results from multiple observing seasons for nine of the 14 objects. These results include Hβ time lags, supermassive black hole masses, and velocity-resolved time lags. The velocity-resolved lags allow us to investigate the kinematics of the broad-line region.

DMD Based Multi-Object Spectrograph for INdian Spectroscopic and Imaging Space Telescope: INSIST

INdian Spectroscopic and Imaging Space Telescope (INSIST) is the next-generation UV-Optical space mission proposed by the Indian Astronomical community motivated by the great success of India’s first multi-wavelength Astronomical satellite (ASTROSAT) where Ultra Violet Imaging Telescope (UVIT) was one of the main payload launched in 2015 by Indian Space Research Organisation. INSIST is primarily designed for photometry observation in three bands (g-[400[Formula: see text]nm–550[Formula: see text]nm], u-[300[Formula: see text]nm–400[Formula: see text]nm] and UV-[150[Formula: see text]nm–300[Formula: see text]nm]) simultaneously over 0.25 sq.degree field of view. INSIST is equipped with a low resolution [[Formula: see text]] spectrograph for multi-Object slitless spectroscopy over the imaging field of view and also has a medium resolution [[Formula: see text]] spectrograph for multi-object slit spectroscopy in UV-band over ∼6 sq.arcmin sky. MEMS-based Digital Micromirror Device [DMD] is used to form configurable slits for the selection of objects at the focal plane of the telescope for multi-object slit spectrograph. Multi-Object spectrograph with DMD as a re-configurable slit for INSIST is designed and the performance of the spectrograph is presented.

Keck Planet Imager and Characterizer Emission Spectroscopy of WASP-33b

We present Keck Planet Imager and Characterizer (KPIC) high-resolution (R ∼35,000) K-band thermal emission spectroscopy of the ultrahot Jupiter WASP-33b. The use of KPIC’s single-mode fibers greatly improves both blaze and line-spread stabilities relative to slit spectrographs, enhancing the cross-correlation detection strength. We retrieve the dayside emission spectrum with a nested-sampling pipeline, which fits for orbital parameters, the atmospheric pressure–temperature profile, and the molecular abundances. We strongly detect the thermally inverted dayside and measure mass-mixing ratios for CO (), H2O (), and OH (), suggesting near-complete dayside photodissociation of H2O. The retrieved abundances suggest a carbon- and possibly metal-enriched atmosphere, with a gas-phase C/O ratio of , consistent with the accretion of high-metallicity gas near the CO2 snow line and post-disk migration or with accretion between the soot and H2O snow lines. We also find tentative evidence for 12CO/13CO ∼ 50, consistent with values expected in protoplanetary disks, as well as tentative evidence for a metal-enriched atmosphere (2–15 × solar). These observations demonstrate KPIC’s ability to characterize close-in planets and the utility of KPIC’s improved instrumental stability for cross-correlation techniques.

Spectroscopic searches for evolutionary orbital period changes in WR + OB binaries: the case of CQ Cep and CX Cep

ABSTRACT We present the results of spectroscopic observations of two eclipsing WR + OB-type systems – CQ Cep and CX Cep – performed in 2020–2023 with a low-resolution slit spectrograph TDS (λλ = 3660–7410 Å, R = 1300–2500) on 2.5-m telescope of the SAI MSU Caucasian Mountain Observatory. For CQ Cep, the radial velocity curves of a WN6 star are constructed, the problem of visibility of spectroscopic traces of an OB star is discussed, and the components’ mass ratio q ∼ 0.6 is estimated. For CX Cep, the radial velocity curves are constructed for both the WN5 and O5 components enabling their masses and circular orbit elements to be refined. The comparison of the radial velocity curves of these systems obtained in different epochs allowed us to derive the orbital period change rate $\dot{P}$ by the spectroscopic method, which is found to be in good agreement with estimates obtained by comparing the moments of primary eclipse minima: $\dot{P} = -0.0151\pm 0.0013$ s yr−1 for CQ Cep and $\dot{P} = 0.054\pm 0.009$ s yr−1 for CX Cep. The prospects of applicability of the spectroscopic dynamical method for studying the orbital evolution of Galactic WR + OB binaries and related objects are considered. We also discuss the effect of finite sizes of stars with stellar wind mass-loss in close binary systems on their orbital evolution.

First Flight of the EUV Snapshot Imaging Spectrograph (ESIS)

The Extreme-ultraviolet Snapshot Imaging Spectrograph (ESIS) launched on a sounding rocket from White Sands Missile Range on 2019 September 30. ESIS is a computed tomography imaging spectrograph (CTIS) designed to map emission line profiles across a wide field of view, revealing the structure and dynamics of small-scale transient events that are prevalent at transition region temperatures. In this paper, we review the ESIS instrument, mission, and data captured. We demonstrate how this unique data set can be interpreted qualitatively and further present some initial quantitative inversions of the data. Using a multiplicative algebraic reconstruction technique, we combine information from all four ESIS channels into a single spatial–spectral cube at every exposure. We analyze two small explosive events in the O v 629.7 Å spectral line with jets near ±100 km s−1 that evolve on 10 s timescales and vary significantly over small spatial scales. Intriguingly, each of these events turns out to be a bimodal (red+blue) jet with outflows that are asymmetric and unsynchronized. We also present a qualitative analysis of a small jetlike eruption captured by ESIS and draw comparisons to previously observed mini-filament eruptions. In 5 minutes of observing time, ESIS captured the spatial and temporal evolution of tens of these small events across the ∼11.′5 field of view, as well as several larger extended eruptions, demonstrating the advantage of CTIS instruments over traditional slit spectrographs in capturing the spatial and spectral information of dynamic solar features across large fields of view.

Doppler-velocity Drifts Detected in a Solar Prominence

We analyzed multiline observations of a quiescent prominence from the slit spectrograph located at the Ondřejov Observatory. Dopplergrams and integrated intensity maps of the whole prominence were obtained from observations in six spectral lines: Ca ii H, Hϵ, Hβ, He i D3, Hα, and Ca ii IR. By combining integrated intensity maps with non-LTE radiative-transfer modeling, we carefully identified areas in an optically thin regime. The comparison of the Doppler-velocity maps and scatterplots from different lines shows the existence of differences in the velocity of ions and neutrals called velocity drift. The drift is of a local nature, present mostly at prominence edges in the area with a large velocity gradient, as can be tentatively expected based on multifluid MHD models. We could not explore the time evolution of the drift, since our data set consists of a single scan only. Our paper brings another contribution to a rather controversial problem of the detection of multifluid effects in solar prominences.

The Solar Line Emission Dopplerometer project

Observations of the dynamics of solar coronal structures are necessary to investigate space weather phenomena and global heating of the corona. The profiles of high temperature lines emitted by the hot plasma are usually integrated by narrow band filters or recorded by classical spectroscopy. We present in this paper details of a new transportable instrument (under construction) for imaging spectroscopy: the Solar Line Emission Dopplerometer (SLED). It uses the Multi-channel Subtractive Double Pass (MSDP) technique, which combines the advantages of both filters and narrow slit spectrographs, i.e. high temporal, spatial and spectral resolutions. The SLED will measure at high cadence (1 Hz) the line-of-sight velocities (Doppler shifts) of hot coronal loops, in the forbidden lines of FeX 637. nm and FeXIV 530.3 nm. It will follow the dynamics of fast evolving events of solar activity such as flares or Coronal Mass Ejections (CMEs), and also study coronal heating by short period waves. Observations will be performed with the coronagraph at the Lomnicky Stit Observatory (LSO, in Slovakia) or during total eclipses. The SLED will also observe the dynamics of solar prominences in Halpha 656.3 nm or HeD3 587.6 nm lines when mounted on the Bialkow coronagraph (near Wroclaw, Poland). It is fully compatible with polarimetric measurements by various techniques.

The SLED project and the dynamics of coronal flux ropes

Investigations of the dynamics of the hot coronal plasma are crucial for understanding various space weather phenomena and making in-depth analyzes of the global heating of the solar corona. We present here numerical simulations of observations of siphon flows along loops (simple semi-circular flux ropes) to demonstrate the capabilities of the Solar Line Emission Dopplerometer (SLED), a new instrument under construction for imaging spectroscopy. It is based on the Multi-channel Subtractive Double Pass (MSDP) technique, which combines the advantages of filters and slit spectrographs. SLED will observe coronal structures in the forbidden lines of FeX 6374 Å and FeXIV 5303 Å, and will measure Doppler shifts up to 150 km s−1 at high precision (50 m s−1) and cadence (1 Hz). It is optimized for studies of the dynamics of fast evolving events such as flares or Coronal Mass Ejections (CMEs), as well as for the detection of high-frequency waves. Observations will be performed with the coronagraph at Lomnický Štít Observatory (LSO), and will also occur during total solar eclipses as SLED is a portable instrument.

A correction method for the telluric absorptions and application to Lijiang Observatory

Observing a telluric standard star for correcting the telluric absorption lines of spectrum will take a significant amount of precious telescope time, especially in the long-term spectral monitoring project. Beyond that, it is difficult to select a suitable telluric standard star near in both time and airmass to the scientific object. In this paper, we present a method of correcting the telluric absorption lines by combining the advantages of long slit spectroscopy. By rotating the slit, we observed the scientific object and a nearby comparison star in one exposure, so that the spectra of both objects should have the same telluric transmission spectrum. The telluric transmission spectrum was constructed by dividing the observed spectrum of the comparison star by its stellar template, and was used to correct the telluric absorption lines of the scientific object. Using the long slit spectrograph of the Lijiang 2.4-meter telescope, we designed a long-term spectroscopic observation strategy, and finished a four-year spectroscopic monitoring for a pair of objects (an active galactic nucleus and a non-varying comparison star). We applied this method to correct the telluric absorption lines of the long-term monitored spectra by the Lijiang 2.4-meter telescope, and investigated the variation of the telluric absorptions at Lijiang Observatory. We found that the telluric absorption transparency is mainly modulated by the seasonal variability of the relative humidity, airmass and seeing. Using the scatter of the [OIII] λ5007 fluxes emitted from the narrow-line region of active galactic nuclei as an indicator, we found that the correction accuracy of the telluric absorption lines is 1%.

On-sky measurements of atmospheric dispersion – I. Method validation

ABSTRACT Observations with ground-based telescopes are affected by differential atmospheric dispersion due to the wavelength-dependent index of refraction of the atmosphere. The usage of an atmospheric dispersion corrector (ADC) is fundamental to compensate this effect. Atmospheric dispersion correction residuals above the level of ∼100 milliarcseconds (mas) will affect astronomical observations, in particular radial velocity and flux losses. The design of an ADC is based on atmospheric models. To the best of our knowledge, those models have never been tested on-sky. In this paper, we present a new method to measure the atmospheric dispersion on-sky in the optical range. We require an accuracy better than 50 mas that is equal to the difference between atmospheric models. The method is based on the use of cross-dispersion spectrographs to determine the position of the centroid of the spatial profile at each wavelength of each spectral order. The method is validated using cross-dispersed spectroscopic data acquired with the slit spectrograph UVES. We measure an instrumental dispersion of $\rm 47 ~ mas$ in the blue arm, and 15 and 23 mas in the two ranges of the red arm. We also measure a 4 per cent deviation in the pixel scale from the value cited in UVES manual. The accuracy of the method is ∼17 mas in the range of 315–665 nm. At this level, we can compare and characterize different atmospheric dispersion models for better future ADC designs.

An optical transmission spectrum of the ultra-hot Jupiter WASP-33 b

There has been increasing progress toward detailed characterization of exoplanetary atmospheres, in both observations and theoretical methods. Improvements in observational facilities and data reduction and analysis techniques are enabling increasingly higher quality spectra, especially from ground-based facilities. The high data quality also necessitates concomitant improvements in models required to interpret such data. In particular, the detection of trace species such as metal oxides has been challenging. Extremely irradiated exoplanets (~3000 K) are expected to show oxides with strong absorption signals in the optical. However, there are only a few hot Jupiters where such signatures have been reported. Here we aim to characterize the atmosphere of the ultra-hot Jupiter WASP-33 b using two primary transits taken 18 orbits apart. Our atmospheric retrieval, performed on the combined data sets, provides initial constraints on the atmospheric composition of WASP-33 b. We report a possible indication of aluminum oxide (AlO) at 3.3-σ significance. The data were obtained with the long slit OSIRIS spectrograph mounted at the 10-m Gran Telescopio Canarias. We cleaned the brightness variations from the light curves produced by stellar pulsations, and we determined the wavelength-dependent variability of the planetary radius caused by the atmospheric absorption of stellar light. A simultaneous fit to the two transit light curves allowed us to refine the transit parameters, and the common wavelength coverage between the two transits served to contrast our results. Future observations with HST as well as other large ground-based facilities will be able to further constrain the atmospheric chemical composition of the planet.

Developments of a multi-wavelength spectro-polarimeter on the Domeless Solar Telescope at Hida Observatory

Abstract To obtain full Stokes spectra in multi-wavelength windows simultaneously, we developed a new spectro-polarimeter on the Domeless Solar Telescope at Hida Observatory. The new polarimeter consists of a 60 cm aperture vacuum telescope on an altazimuth mounting, an image rotator, a high-dispersion spectrograph, and a polarization modulator and an analyzer composed of a continuously rotating waveplate with a retardation that is nearly constant at around 127° in 500–1100 nm. There are also a polarizing beam splitter located close behind the focus of the telescope, fast and large format CMOS cameras, and an infrared camera. A slit spectrograph allows us to obtain spectra in as many wavelength windows as the number of cameras. We characterized the instrumental polarization of the entire system and established a polarization calibration procedure. The cross-talks among the Stokes Q, U, and V have been evaluated to be about 0.06%–1.2%, depending on the degree of the intrinsic polarizations. In a typical observing setup, a sensitivity of 0.03% can be achieved in 20–60 seconds for 500–1100 nm. The new polarimeter is expected to provide a powerful tool for diagnosing the 3D magnetic field and other vector physical quantities in the solar atmosphere.

Effect of geomagnetic storms on the daytime low-latitude thermospheric wave dynamics

The equatorial- and low-latitude thermospheric dynamics is affected by both equatorial electrodynamics and neutral wave dynamics, the relative variation of which is dependent on the prevalent background conditions, which in turn has a seasonal dependence. Depending on the ambient thermospheric conditions, varying effects of the geomagnetic disturbances on the equatorial- and low-latitude thermosphere are observed. To investigate the effect of these disturbances on the equatorial- and low-latitude neutral wave dynamics, daytime airglow emission intensities at OI 557.7 nm, OI 630.0 nm, and OI 777.4 nm are used. These emissions from over a large field-of-view (FOV∼1000) have been obtained using a high resolution slit spectrograph, MISE (Multiwavelength Imaging Spectrograph using Echelle grating), from a low-latitude location, Hyderabad (17.50N, 78.40E; 8.90N MLAT), in India. Variations of the dayglow emission intensities are investigated during three geomagnetic disturbance events that occurred in different seasons. It is seen that the neutral dayglow emission intensities at all the three wavelengths showed different type of variations with the disturbance storm time (Dst) index in different seasons. Even though the dayglow emission intensities over low-latitude regions are sensitive to the variation in the equatorial electric fields, during periods of geomagnetic disturbances, especially in solstices, these are dependent on thermospheric O/N2 values. This shows the dominance of neutral dynamics over electrodynamics in the low-latitude upper atmosphere during geomagnetic disturbances. Further, spectral analyses have been carried out to obtain the zonal scale sizes in the gravity wave regime and their diurnal distributions are compared for geomagnetic quiet and disturbed days. Broadly, the zonal scales seem to be breaking into various scale sizes on days of geomagnetic disturbances when compared to those on quiet days. This contrast in the diurnal distribution of the zonal scale sizes brings to light, for the first time, the varying nature of the neutral wave coupling in the daytime thermosphere during periods of geomagnetic disturbances.

High-resolution Observations of H α $\alpha$ Spectra with a Subtractive Double Pass

High-resolution imaging spectroscopy in solar physics has relied on Fabry-Perot Interferometers (FPIs) in recent years. FPI systems, however, get technically challenging and expensive for telescopes larger than the 1-m class. A conventional slit spectrograph with a diffraction-limited performance over a large field of view (FOV) can be built at much lower cost and effort. It can be converted to an imaging spectro(polari)meter using the concept of a subtractive double pass (SDP). We demonstrate that an SDP system can reach a similar performance as FPI-based systems with a high spatial and moderate spectral resolution across a FOV of 100"x100" with a spectral coverage of 1 nm. We use Halpha spectra taken with a SDP system at the Dunn Solar Telescope and complementary full-disc data to infer the properties of small-scale superpenumbral filaments. We find that the majority of all filaments end in patches of opposite-polarity fields. The internal fine-structure in the line-core intensity of Halpha at spatial scales of about 0.5" exceeds that in other parameters such as the line width, indicating small-scale opacity effects in a larger-scale structure with common properties. We conclude that SDP systems are a valid alternative to FPI systems when high spatial resolution and a large FOV are required. They also can reach a cadence that is comparable to that of FPI systems, while providing a much larger spectral range.

ASTRONIRCAM—the infrared camera-spectrograph for the 2.5-m telescope of SAI Caucasian observatory

ASTRONIRCAM is a cryogenic-cooled slit spectrograph for the spectral range 1-2.5 mkm installed at the Nasmyth focus of the 2.5-meter telescope of the Caucasian observatory of Sternberg Astronomical Institute of Lomonosov Moscow State University. The instrument is equipped with the HAWAII-2RG 2048x2048 HgCdTe array. Grisms are used as dispersive elements. In the photometric mode ASTRONIRCAM allows for extended astronomical object imaging in the field of view of 4.6x4.6 arc minutes with the 0.269 arcsec/pixel scale in standard photometric bands J, H, K and Ks as well as in narrow-band filters CH_4, [Fe II], H_2 v=1-0 S(1), Br_gamma and CO. In the spectroscopic mode, ASTRONIRCAM takes spectra of extended or point-like sources with spectral resolution R=lambda/Delta lambda <= 1200. The general design, optical system, detector electronics and readout, amplification and digitization scheme are considered. The conversion factor GAIN measurement results are described as well as its dependence on the accumulated signal (non-linearity). The full transmission of the atmosphere-to-detector train ranges from 40 to 50\% in the wide-band photometry mode. The ASTRONIRCAM sensitivity at the 2.5-m telescope is characterized by the limiting J=20, K=19 star magnitudes measured with the 10% precision and 15 minutes integration at the 1 arcsec atmospheric seeing conditions. The references to first results published on the base of ASTRONIRCAM observations are given.

Small‐scale longitudinal variations in the daytime equatorial thermospheric wave dynamics as inferred from oxygen dayglow emissions

AbstractThe equatorial upper atmospheric dynamic processes show both latitudinal and longitudinal variabilities. While the variability in latitudes can exist over small distances (approximately hundreds of kilometers), the longitudinal behavior has been shown to be existing mainly over large spatial separations (approximately thousands of kilometers). In the present work we have used variations in thermospheric optical dayglow emissions at OI 557.7, 630.0, and 777.4 nm, as tracers of neutral dynamics. These emissions are obtained simultaneously from a high‐resolution slit spectrograph, Multi wavelength Imaging Spectrograph using Echelle grating, from a low‐latitude location, Hyderabad (17.5°N, 78.4°E; 8.9°N magnetic latitude) in India, to investigate the longitudinal differences in the upper atmospheric processes over short separations. Spectral analyses of gravity waves carried out on the dayglow emission intensity variations for different independent viewing directions on some days show dissimilar periodicities suggesting the existence of longitudinal differences. Gravity wave scale sizes and the propagation characteristics on these days are different from those in which longitudinal differences are not seen. Further, the zenith diurnal emission intensity patterns are different on the days with and without the observed longitudinal variability. This work shows for the first time that longitudinal differences in upper atmospheric processes can exist at even as small as 3° longitude separations. Such longitudinal differences seen in the neutral dayglow emission intensities are attributed to the zonal variation in the daytime equatorial electrodynamics.

A New Population of Galactic Bulge Planetary Nebulae

January 2016 – title page.%%%%The Academic Senate of Macquarie University granted this degree in 2015, but the date 2016 appears on the title page, the verso of the title page and the spine.%%%%%%%%%%%%1. Planetary nebulas - history and overview – 2. The planetary nebula luminosity function – 3. New bulge PNs – 4. Duplicate objects – 5. Other observations – 6. New bulge PNLF – 7. Results and discussion – A. Spectral features – B. Galactic bulge mosaic II survey fields – C. Galactic bulge PNs – D. Publications – References.%%%%A new population of Galactic bulge planetary nebulas is presented. Nebula candidates were discovered by systematically reviewing archival [OIII] on/off band survey imaging of the central -5⁰ ≤ l ≤ 5⁰, -5⁰ ≤ b ≤ 5⁰ region around the Galactic centre. An image segmentation and interleaving scheme was developed to facilitate this review. The resultant candidates (> 200) were then double checked against complementary archival Hα sky survey data to screen for obvious planetary nebula (PN) mimics or spurious image artefacts.%%%%Confirmatory spectroscopy of the PN candidates was pursued with thin slit, fibre multiobject and wide field spectrographs. Custom software was built to streamline interfacing with third-party spectroscopic management tools and a parallel greedy set cover algorithm implemented for efficient field selection in constrained multi-object observations.%%%%The combined imaging and spectroscopic evidence yielded true (4), probable (31) and possible (83) PNs toward the bulge. Secondary discoveries such as new PN mimics and late type stars were by-products of the confirmatory spectroscopy. Instances of literature PN duplication encountered during the investigation were noticed and documented.%%%%Spectral analysis of new PNs, including those obtained with a new optimised sky subtraction technique devised and demonstrated here, provided diagnostic data allowing radial velocity and Balmer decrement determination. Using a combined diameter and radial velocity criterion, bona fide bulge PNs were distinguished from new foreground PNs. Where Balmer decrements were available for new bulge PNs, differential aperture photometry was used to provide a modest data increment to Galactic bulge planetary nebula luminosity function (PNLF).%%%%The PNLF was revised with data from some new bulge PNs, but more significantly, by a series of corrections to the data derived from previously known bulge PNs (~225), such as improved filter transmission effects, statistically justified binning and application of a uniform bulge-relevant extinction law. The result was the most rigorous bulge PNLF to date. An improvement on the legacy PNLF, the revised PNLF exhibited a form inconsistent with typical extragalactic examples, an expected result of the unusual extinction correction method used to address bulge-specific observational limitations. Issues restricting the accuracy of the bulge PNLF were identified. Until those restrictions are ameliorated, the utility of the PNLF in aiding physical understanding…

First Results from the KMOS Lens-Amplified Spectroscopic Survey (KLASS): Kinematics of Lensed Galaxies at Cosmic Noon

Abstract We present the first results of the K-band Multi-Object Spectrometer (KMOS) Lens-Amplified Spectroscopic Survey, a new ESO Very Large Telescope large program, doing multi-object integral field spectroscopy of galaxies gravitationally lensed behind seven galaxy clusters selected from the Hubble Space Telescope (HST) Grism Lens-Amplified Survey from Space. Using the power of the cluster magnification, we are able to reveal the kinematic structure of 25 galaxies at , in four cluster fields, with stellar masses . This sample includes five sources at with lower stellar masses than in any previous kinematic integral field unit (IFU) surveys. Our sample displays a diversity in kinematic structure over this mass and redshift range. The majority of our kinematically resolved sample is rotationally supported, but with a lower ratio of rotational velocity to velocity dispersion than in the local universe, indicating the fraction of dynamically hot disks changes with cosmic time. We find that no galaxies with stellar mass in our sample display regular ordered rotation. Using the enhanced spatial resolution from lensing, we resolve a lower number of dispersion-dominated systems compared to field surveys, competitive with findings from surveys using adaptive optics. We find that the KMOS IFUs recover emission line flux from HST grism-selected objects more faithfully than slit spectrographs. With artificial slits, we estimate that slit spectrographs miss, on average, 60% of the total flux of emission lines, which decreases rapidly if the emission line is spatially offset from the continuum.

ON THE FINE STRUCTURE SPLITTING OF THE 3p43d 4D5/2 AND 3p43d 4D7/2 LEVELS OF Fe x

ABSTRACT We study UV spectra obtained with the SO82-B slit spectrograph on board SKYLAB to estimate the fine structure (FS) splitting of the Cl-like and levels of Fe x. The splitting is of interest because the Zeeman effect mixes these levels, producing a “magnetically induced transition” (MIT) from to for modest magnetic field strengths characteristic of the active solar corona. We estimate the splitting using the Ritz combination formula applied to two lines in the UV region of the spectrum close to 1603.2 Å, which decay from the level to these two lower levels. The MIT and accompanying spin-forbidden transition lie near 257 Å. By careful inspection of a deep exposure obtained with the S082B instrument, we derive a splitting of cm−1. The upper limit arises because of a degeneracy between the effects of non-thermal line broadening and FS splitting for small values of the latter parameter. Although the data were recorded on photographic film, we solved for optimal values of line width and splitting of 8.3 ± 0.9 and 3.6 ± 2.7 cm−1.

A Hyperspectral Survey of New York City Lighting Technology.

Using side-facing observations of the New York City (NYC) skyline, we identify lighting technologies via spectral signatures measured with Visible and Near Infrared (VNIR) hyperspectral imaging. The instrument is a scanning, single slit spectrograph with 872 spectral channels from 0.4–1.0 m. With a single scan, we are able to clearly match the detected spectral signatures of 13 templates of known lighting types. However, many of the observed lighting spectra do not match those that have been measured in the laboratory. We identify unknown spectra by segmenting our observations and using Template-Activated Partition (TAP) clustering with a variety of underlying unsupervised clustering methods to generate the first empirically-determined spectral catalog of roughly 40 urban lighting types. We show that, given our vantage point, we are able to determine lighting technology use for both interior and exterior lighting. Finally, we find that the total brightness of our scene shows strong peaks at the 570 nm -, 595 nm - and 818 nm - lines that are common in high pressure sodium lamps, which dominate our observations.