adsabs/AstroCLIMB huggingface dataset:
Paper: High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts
Authors: Andrew Ridden-Harper, Ernst de Mooij, Ray Jayawardhana, Neale Gibson, Raine Karjalainen, Marie Karjalainen
Figure caption: Same as Figure 8 except with the addition of the θ and C parameters.
Paper: High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts
Authors: Andrew Ridden-Harper, Ernst de Mooij, Ray Jayawardhana, Neale Gibson, Raine Karjalainen, Marie Karjalainen
Figure caption: Same as Figure 9 except with the addition of the θ and C parameters.
Paper: High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts
Authors: Andrew Ridden-Harper, Ernst de Mooij, Ray Jayawardhana, Neale Gibson, Raine Karjalainen, Marie Karjalainen
Figure caption: The conditional (2D) and marginalized (1D) likelihood distributions for Fe I using the Goyal et al. (2020) pressure–temperature profile and grid for Night 2.
Paper: High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts
Authors: Andrew Ridden-Harper, Ernst de Mooij, Ray Jayawardhana, Neale Gibson, Raine Karjalainen, Marie Karjalainen
Figure caption: Same as Figure 13 except for being for all nights combined.
Paper: High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts
Authors: Andrew Ridden-Harper, Ernst de Mooij, Ray Jayawardhana, Neale Gibson, Raine Karjalainen, Marie Karjalainen
Figure caption: Same as Figure 13 except for being for Night 3.
Paper: Exploring the Magnetic Field Geometry in NGC 891 with SOFIA/HAWC+
Authors: Jin-Ah Kim, Terry Jay Jones, C. Darren Dowell
Figure caption: Position angle, debiased fractional polarization, debiased polarized intensity, and total intensity as a function of the distance from the center along the major axis. Each data point corresponds to a polarization line shown in the right panel of Figure 1, with a pixel size of 20.″4. Red is the midplane, and green and blue indicate the eastside and westside off 20.″4 about the galactic plane, respectively. Error bars in position angles are the distribution containing 68.2% of 100,000 Monte Carlo simulations. The errors for fractional polarization and debiased polarized intensity are calculated with error propagation from intensity uncertainty in Stokes I, Q, and U. The NIR polarization null point is marked as a gray shadow. The position angle is the angle deviated from the galactic plane, and the positive value means the counterclockwise orientation from the galactic plane. The total intensity is normalized by the intensity of the center in each plane of 2307, 458, and 567 MJy sr−1 in the midplane, eastside, and westside about the galactic plane, respectively.
Paper: Exploring the Magnetic Field Geometry in NGC 891 with SOFIA/HAWC+
Authors: Jin-Ah Kim, Terry Jay Jones, C. Darren Dowell
Figure caption: Left: total intensity map, with a pixel size of 6.″8, overlayed with polarization lines. Different pixel sizes for the polarization lines are indicated by red (6.″8), yellow (13.″6), and cyan (27.″2) colors. The polarization lines have I/I err greater than 30. Solid lines indicate data with p debiased/p err > 3, and dotted lines indicate 3 > p debiased/p err > 2.5. The line length is proportional to the debiased fractional polarization. Middle: polarization lines overlaying the debiased polarized intensity map with a pixel size of 20.″4. All polarization lines are shown regardless of S/N, but observed PI/PIerr has to be larger than 1 to be debiased. The line length is proportional to the debiased polarized intensity. Right: position angle map computed within a pixel size of 20.″4. All polarization lines are represented regardless of S/N, and their lengths are plotted as a constant. Sectors of a circle in dark and bright pink show the extent encompassing 68.2% and 90% of samples based on Monte Carlo simulations. In all panels, contours are 100, 500, 1000, 1500, 2000, and 2500 MJy sr−1 in the total intensity map with a pixel size of 6.″8. The yellow boxed area delineates the vertical structure discussed in the text.
Paper: Exploring the Magnetic Field Geometry in NGC 891 with SOFIA/HAWC+
Authors: Jin-Ah Kim, Terry Jay Jones, C. Darren Dowell
Figure caption: The color map is the HAWC+ observation at 154 μm that the radio (white) and FIR (red) polarization lines are plotted over. The radio data is based on a polarization map with a 1.″5 grid with a beam size of 12″. The pixels with Stokes Q and U below 3σ are not provided for the radio data. Radio polarization lines nearest to the HAWC+ observation grid have been plotted and used. FIR data, which are in the red boxes and have the corresponding radio data, are only plotted and used here. The length of polarization lines is constant regardless of fractional polarization. Polar plots show the normalized distributions of position angles about the galactic plane, ΔP.A., within four regions indicated as red boxes over the color map. The selected area is 20.″4 × (34.0 − 47.6)″. The black and red histograms are the normalized distributions of the position angles from radio and 154 μm observations. The expected distribution of our FIR observations (see the detail in the text) is plotted as the red shade. The black and red vertical lines indicate the circular mean value on the interval (−π/2, π/2), which is ﹩\mathrm{atan}2({\rm{\Sigma }}\,\sin 2\theta ,{\rm{\Sigma }}\,\cos 2\theta )/2﹩, of radio and FIR data, respectively.
Paper: Exploring the Magnetic Field Geometry in NGC 891 with SOFIA/HAWC+
Authors: Jin-Ah Kim, Terry Jay Jones, C. Darren Dowell
Figure caption: Fractional polarization of a spiral model galaxy (green) and a barred spiral model galaxy (black) with an edge-on view. No turbulent magnetic fields exist in the left panel. The ratio of turbulent to ordered magnetic fields, B  t /B 0, is added as 1.0 in the right panel. The transparent colored regions surrounding the model median values represent a dispersion width of 60% in 500 simulations. Note that observational errors are included in the model results, hence the greater dispersion at larger distances from the center where the galaxy is fainter, even in the case of no turbulence. The red line shows the observed fractional polarization in the galactic midplane without any S/N cuts, and not debiased.
Paper: Exploring the Magnetic Field Geometry in NGC 891 with SOFIA/HAWC+
Authors: Jin-Ah Kim, Terry Jay Jones, C. Darren Dowell
Figure caption: Left: same as the barred galaxy in the right panel of Figure 4, but with various threshold numbers (﹩{{ \mathcal N }}_{\mathrm{th}}﹩) for turbulence cells. Different colors show different ﹩{{ \mathcal N }}_{\mathrm{th}}﹩. The numbers of turbulence cells along an LOS through the center are 32, 15, and 10, respectively from the smallest to the largest ﹩{{ \mathcal N }}_{\mathrm{th}}﹩. The shaded regions indicate the model dispersion in fractional polarization. Right: change of fractional polarization while passing through turbulence cells. Hydrogen column density, N(H I+H2), of each cell is 2.0 × 1021 cm−2. Solid lines represent the fractional polarization due to the combination of dichroic extinction and emission, calculated with the equations of transfer in Davidson et al. (2014), but dashed lines ignore the term for dichroic extinction in the equations. The gray shade shows the spread of 60% of 500 simulations. The vertical line is at an optical depth of 0.039, which occurs at the center of our modeled galaxy.
Paper: Exploring the Magnetic Field Geometry in NGC 891 with SOFIA/HAWC+
Authors: Jin-Ah Kim, Terry Jay Jones, C. Darren Dowell
Figure caption: Fractional polarization from the models in comparison with observations. These results are from a synthetic barred spiral galaxy. Different panels vary B  t /B 0, the presence of vertical fields, and p max. A threshold value for turbulence cells, ﹩{{ \mathcal N }}_{\mathrm{th}}﹩, for the modeling is used as 1063, but 5 × 1062 for the model with B  t /B 0 of 1.5. The black lines and gray shades represent the median value and the distribution of 60% in 500 simulations.
Paper: Exploring the Magnetic Field Geometry in NGC 891 with SOFIA/HAWC+
Authors: Jin-Ah Kim, Terry Jay Jones, C. Darren Dowell
Figure caption: Visualizations of the ordered magnetic field geometry (left) and turbulence cells for turbulent magnetic fields in the galactic midplane (right). A spiral (barred spiral) galaxy is in the upper (bottom) panel. The size of a map is 11.75 kpc. The gas density distribution without beam convolution is shown as a gray map in a log scale on the left. Contours on the right represent hydrogen column density, N(H I+H2), of 1.25, 2.5, 5.0, and 10.0 × 1021 cm−2. The turbulence cells shown here are when ﹩{{ \mathcal N }}_{\mathrm{th}}﹩ is 1064, the largest number among our trials (minimum number of turbulent cells), and is used for clarity. The observer is located at the bottom of the images. The right (left) side is the northeast (southwest) of NGC 891 projected on the plane of the sky.
Paper: Exploring the Magnetic Field Geometry in NGC 891 with SOFIA/HAWC+
Authors: Jin-Ah Kim, Terry Jay Jones, C. Darren Dowell
Figure caption: Left: HAWC+ total intensity observation at 154 μm. Middle: our model with a bar structure on an edge-on view. The red contours are 100, 500, and 1000 MJy sr−1 in both HAWC+ observation and the model. The gray dashed contours in the middle are the same as the contours in the HAWC+ observation. Right: number density distribution of position angles within the north, the center, and the south areas. Each region is marked as cyan boxes in the middle. The position angle is measured from the galactic plane, and the counterclockwise direction is a positive value. Solid lines are the position angles of pixels within each region from the HAWC+ observation. Dashed lines are the density distribution derived from 500 synthetic images. The model results are from the model with B  t /B 0 = 1.5, which shown in the top panel in Figure 5.
Paper: Spectroscopic Orbits of Subsystems in Multiple Stars. X (Summary)
Authors: Andrei Tokovinin
Figure caption: Histogram of inner periods in hierarchical systems of solar-type stars within 67 pc (full line) and of the subset of 90 inner periods resulting from the CHIRON program (dashed line). The dotted line is a log-normal period distribution of field solar-type binaries from Raghavan et al. (2010) with arbitrary normalization.
Paper: Spectroscopic Orbits of Subsystems in Multiple Stars. X (Summary)
Authors: Andrei Tokovinin
Figure caption: Comparison between six CHIRON and Gaia spectroscopic orbits. All plots show RVs of the primary (solid green line and squares) and secondary (dashed blue line and triangles) components measured by CHIRON vs. orbital phase. The Gaia orbits are depicted by dashed green lines. The CHIRON and Gaia periods are indicated under each plot.
Paper: Exploring the Magnetic Field Geometry in NGC 891 with SOFIA/HAWC+
Authors: Jin-Ah Kim, Terry Jay Jones, C. Darren Dowell
Figure caption: Color maps show the HAWC+ observation at 154 μm and the edge-on view of modeled galaxies. The pixel size and the beam FWHM are 6.″8 and 13.″6 for both the observation and the models. The red contours indicate 100, 500, and 1000 MJy s−1. The total intensity profile along the midplane of the galaxy is plotted in the right panel.
Paper: Spectroscopic Orbits of Subsystems in Multiple Stars. X (Summary)
Authors: Andrei Tokovinin
Figure caption: Periods and eccentricities of 743 inner subsystems with solar-type components found in the MSC. Squares correspond to the ground-based orbits, blue crosses are orbits from Gaia NSS.
Paper: Detection of Rubidium and Samarium in the Atmosphere of the Ultrahot Jupiter MASCARA-4b
Authors: Zewen Jiang, Wei Wang, Gang Zhao, Meng Zhai, Yaqing Shi, Yujuan Liu, Jingkun Zhao, Yuqin Chen
Figure caption: First panels: the 2D CCF maps of Mg, Ca, Cr and Fe with CLV+RM effects uncorrected using pRT opacity. The white dotted lines mark the beginning and ending positions of the transit and the inclined white lines indicate the expected trace of signal from the planet. Second panels: same as the first panels but with CLV+RM effects corrected. Third panels: the K p–ΔV sys maps in the range of 50 ∼ 300 km s−1. In each panel, the planet signal is expected to appear around the intersection of the two white dotted lines, while the red crosses mark the position with maximum S/N. Fourth panels: the S/N plots at the expected K p position in blue and at the Max-S/N corresponding K p.
Paper: Detection of Rubidium and Samarium in the Atmosphere of the Ultrahot Jupiter MASCARA-4b
Authors: Zewen Jiang, Wei Wang, Gang Zhao, Meng Zhai, Yaqing Shi, Yujuan Liu, Jingkun Zhao, Yuqin Chen
Figure caption: The combined CCF map at different orbital phase before (top panel) and after (bottom panel) the correction of stellar pulsation, respectively. The map is combined with a step size of 0.002 in orbital phase. In each panel, the white dotted lines mark the four contacts during the transit, the inclined white lines indicate the expected trace of signal from the planet, and the bright yellow stripe shows the RM +CLV signal. The out-of-transit steaks in the top panel arise from stellar pulsation.
Paper: Detection of Rubidium and Samarium in the Atmosphere of the Ultrahot Jupiter MASCARA-4b
Authors: Zewen Jiang, Wei Wang, Gang Zhao, Meng Zhai, Yaqing Shi, Yujuan Liu, Jingkun Zhao, Yuqin Chen
Figure caption: Same as Figure 4, but using DACE opacity to obtain CCFs map for Mg, Ca, Cr, and Fe.
Paper: Detection of Rubidium and Samarium in the Atmosphere of the Ultrahot Jupiter MASCARA-4b
Authors: Zewen Jiang, Wei Wang, Gang Zhao, Meng Zhai, Yaqing Shi, Yujuan Liu, Jingkun Zhao, Yuqin Chen
Figure caption: An example of telluric correction using Molecfit in the observed spectrum of MASCARA-4 b taken in T1 for Na D1 and D2 (top) and Hα (bottom). The observed spectra are shown in blue, while the spectra after telluric correction are shown in orange. The dashed green vertical lines represent the static positions of the atomic lines in vacuum.
Paper: Detection of Rubidium and Samarium in the Atmosphere of the Ultrahot Jupiter MASCARA-4b
Authors: Zewen Jiang, Wei Wang, Gang Zhao, Meng Zhai, Yaqing Shi, Yujuan Liu, Jingkun Zhao, Yuqin Chen
Figure caption: Same as Figure 4, but for CaH, FeH, VO, and TiO.
Paper: Detection of Rubidium and Samarium in the Atmosphere of the Ultrahot Jupiter MASCARA-4b
Authors: Zewen Jiang, Wei Wang, Gang Zhao, Meng Zhai, Yaqing Shi, Yujuan Liu, Jingkun Zhao, Yuqin Chen
Figure caption: The RM+CLV model for Fe generated by cross-correlation between residual spectra created by synthetic spectrum using SME and the template spectra calculated by DACE, which is used to eliminate the influence of the variation of stellar line profile during transit.
Paper: Detection of Rubidium and Samarium in the Atmosphere of the Ultrahot Jupiter MASCARA-4b
Authors: Zewen Jiang, Wei Wang, Gang Zhao, Meng Zhai, Yaqing Shi, Yujuan Liu, Jingkun Zhao, Yuqin Chen
Figure caption: Same as Figure 6, but for Rb, Sm, Ti+, Ba+, and Sc+.
Paper: Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
Authors: Hunter Brooks, J. Davy Kirkpatrick, Aaron M. Meisner, Christopher R. Gelino, Daniella C. Bardalez Gagliuffi, Federico Marocco, Adam C. Schneider, Jacqueline K. Faherty, S. L. Casewell, Yadukrishna Raghu, Marc J. Kuchner
Figure caption: Observation windows of both the Spitzer and WISE data sets used in this paper. The Spitzer program number (black numbers) and the time span that it surveyed are shown by the rainbow lines if the time period is only a handful of nights (Table 3 in Kirkpatrick et al. 2021). The WISE timescale is shown by the top two lines that include “WISE/NEOWISE” and “NEOWISE Reactivation” (Mainzer et al. 2014). Finally, the light gray dashed vertical line marks the transition from the Spitzer cryogenic mission to the warm mission. For exmaple, 53000 MJD is 2003 December 27 and 59500 MJD is 2021 October 13.
Paper: Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
Authors: Hunter Brooks, J. Davy Kirkpatrick, Aaron M. Meisner, Christopher R. Gelino, Daniella C. Bardalez Gagliuffi, Federico Marocco, Adam C. Schneider, Jacqueline K. Faherty, S. L. Casewell, Yadukrishna Raghu, Marc J. Kuchner
Figure caption: Subplot (a) displays a histogram of the number of AORs (N spitzer) for each object in our sample of 361 brown dwarfs, displayed in gray. The distribution is multimodal, though most objects have between six and 16 AORs. The red distribution of subplot (a) is a histogram of the number of unTimely detections found for each object (N WISE). Subplot (b) is a histogram of the total number of points for each object, where N total = N spitzer + N WISE.
Paper: Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
Authors: Hunter Brooks, J. Davy Kirkpatrick, Aaron M. Meisner, Christopher R. Gelino, Daniella C. Bardalez Gagliuffi, Federico Marocco, Adam C. Schneider, Jacqueline K. Faherty, S. L. Casewell, Yadukrishna Raghu, Marc J. Kuchner
Figure caption: The spectral type distribution of the 361 objects from Kirkpatrick et al. (2021). Optical spectral types (SpecO) are used for L dwarfs and infrared types (SpecIR) are used for T and Y dwarfs. For objects without confirmed spectral types, we take the types estimated using available photometry (SpecAd).
Paper: Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
Authors: Hunter Brooks, J. Davy Kirkpatrick, Aaron M. Meisner, Christopher R. Gelino, Daniella C. Bardalez Gagliuffi, Federico Marocco, Adam C. Schneider, Jacqueline K. Faherty, S. L. Casewell, Yadukrishna Raghu, Marc J. Kuchner
Figure caption: A histogram of the total number of Spitzer PRF (blue), Spitzer aperture (orange), and WISE PSF (green) average magnitudes for each 0.5 mag wide bin.
Paper: Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
Authors: Hunter Brooks, J. Davy Kirkpatrick, Aaron M. Meisner, Christopher R. Gelino, Daniella C. Bardalez Gagliuffi, Federico Marocco, Adam C. Schneider, Jacqueline K. Faherty, S. L. Casewell, Yadukrishna Raghu, Marc J. Kuchner
Figure caption: Images at different angular resolutions for the same object, WISE J022623.98−021142.8 (Kirkpatrick et al. 2011): Keck/NIRC2 J (top panel; Gelino 2012), Spitzer/IRAC ch2 (middle panel; Kirkpatrick et al. 2021), and WISE/unWISE W2 (bottom panel; Lang 2014). The panels are 20″ × 30″, with up being north and left being east. The primary is labeled with a blue “A,” while the secondary is a red “B.” See Section 6.1 for details.
Paper: Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
Authors: Hunter Brooks, J. Davy Kirkpatrick, Aaron M. Meisner, Christopher R. Gelino, Daniella C. Bardalez Gagliuffi, Federico Marocco, Adam C. Schneider, Jacqueline K. Faherty, S. L. Casewell, Yadukrishna Raghu, Marc J. Kuchner
Figure caption: Comparison of the spectral type (Figure 3(a)) to the averaged χ 2 (for the ch2PRF fit) for each object. The solid blue line is the median for each spectral type, while the dashed light blue lines are the 25th and 75th percentiles for each spectral type. Note the large outliers on this plot, most of which were identified as possible binary candidates (further discussed in Section 6.1). Lastly, one object, 2MASS J22551861−5713056 (Kendall et al. 2007), which has a ﹩\bar{{\chi }^{2}}﹩ value of ∼68, is not shown on this plot. This is a known brown dwarf binary (Reid et al. 2008).
Paper: Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
Authors: Hunter Brooks, J. Davy Kirkpatrick, Aaron M. Meisner, Christopher R. Gelino, Daniella C. Bardalez Gagliuffi, Federico Marocco, Adam C. Schneider, Jacqueline K. Faherty, S. L. Casewell, Yadukrishna Raghu, Marc J. Kuchner
Figure caption: Photometric precision as a function of magnitude. The x-axis shows ch2aperture, ch2PRF, and W2PSF photometry in 0.5 mag bins, while the y-axis is the median uncertainties between all photometry points (σ) for each bin. Points 1 and 2 are known variables 2MASS J21392676+0220226 and 2MASS J22282889−4310262 (Yang et al. 2016), respectively. The drop in WISE σ at 16–16.5 mag is a result of four out of six objects in this bin having lower than average standard deviations.
Paper: Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
Authors: Hunter Brooks, J. Davy Kirkpatrick, Aaron M. Meisner, Christopher R. Gelino, Daniella C. Bardalez Gagliuffi, Federico Marocco, Adam C. Schneider, Jacqueline K. Faherty, S. L. Casewell, Yadukrishna Raghu, Marc J. Kuchner
Figure caption: Comparison of spectral type vs. the difference between the Spitzer ch2PRF median and the unTimely W2PSF median. The large outliers are a result of the Spitzer code trying to passively deblend the point source (further discussed in Section 6.1). Otherwise, we see a general trend in which the Spitzer ch2 and unTimely W2 photometry match extremely well, consistent with Figure 15 from Kirkpatrick et al. (2021).
Paper: Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
Authors: Hunter Brooks, J. Davy Kirkpatrick, Aaron M. Meisner, Christopher R. Gelino, Daniella C. Bardalez Gagliuffi, Federico Marocco, Adam C. Schneider, Jacqueline K. Faherty, S. L. Casewell, Yadukrishna Raghu, Marc J. Kuchner
Figure caption: The distribution of angular separation for the 361 objects in our sample, assuming a binary with 3 au physical separation (black) or 10 au physical separation (red). The 3 au distribution peaks at 0.″2 and the one at 10 au peaks at 0.″5.
Paper: Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
Authors: Hunter Brooks, J. Davy Kirkpatrick, Aaron M. Meisner, Christopher R. Gelino, Daniella C. Bardalez Gagliuffi, Federico Marocco, Adam C. Schneider, Jacqueline K. Faherty, S. L. Casewell, Yadukrishna Raghu, Marc J. Kuchner
Figure caption: A histogram of the number of points for each MJD interval for both Spitzer and WISE. Each bin is 82 days each.
Paper: The Infrared Colors of 51 Eridani b: Micrometeoroid Dust or Chemical Disequilibrium?
Authors: Alexander Madurowicz, Sagnick Mukherjee, Natasha Batalha, Bruce Macintosh, Mark Marley, Theodora Karalidi
Figure caption: Influence of micrometeoroid dust model parameters on the resulting SED. This particular simulation uses grid temperature T grid = 1000 K, surface gravity g = 316 m s−1, vertical eddy diffusion coefficient K  zz  = 1010 cm2 s−1, sedimentation efficiency f sed = 3, and cloud hole fraction f hole = 0, while the dust power-law index α and coefficient N 0 vary depending on the line color in the legend. In the top panel, α is varied, showing how steep power laws have the majority of optical power in submicron-sized particles that scatter light at shorter wavelengths, while the flat power laws are dominated by submillimeter-sized grains that scatter strongly at all relevant wavelengths. In the bottom panel, the effect of increasing N 0 at fixed α is demonstrated. More infalling dust generally implies greater scattering, although the parameters chosen here represent potentially unphysical and extreme values that are necessary to increase the significance of the effect and make the resulting change in the spectra visible by eye.