II Infrared Triplet Research Articles

The Near-infrared Ca ii Triplet as a Stellar Activity Indicator: A Library and Comparative Study

We have established and released a new stellar index library of the Ca ii triplet, which serves as an indicator for characterizing the chromospheric activity of stars. The library is based on data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Low-Resolution Spectroscopic Survey (LRS) Data Release 9. To better reflect the chromospheric activity of stars, we have defined new indices R and R +. The library includes measurements of R and R + for each Ca ii infrared triplet (IRT) from 699,348 spectra of 562,863 F, G, and K-type solar-like stars with a signal-to-noise ratio higher than 100, as well as the stellar atmospheric parameters and basic information inherited from the LAMOST LRS catalog. We compared the differences between the three individual indices of the Ca ii triplet and also conducted a comparative analysis of Rλ8542+ to the Ca ii H and K S and RHK+ index databases. We observe the fraction of less active stars decreases with T eff and the fraction of more active stars first decreases with decreasing temperature and turns to increase with decreasing temperature at 5800 K. We also find that a significant fraction of stars that show a high activity index in both Ca ii H and K and IRT are binaries with low activity; some of them could be discriminated in the Ca ii H and K S index and Rλ8542+ space. This new stellar library serves as a valuable resource for studying chromospheric activity in stars and can be used to improve our comprehension of stellar magnetic activity and other astrophysical phenomena.

Characterizing the Near-infrared Spectra of Flares from TRAPPIST-1 during JWST Transit Spectroscopy Observations

We present the first analysis of JWST near-infrared spectroscopy of stellar flares from TRAPPIST-1 during transits of rocky exoplanets. Four flares were observed from 0.6–2.8 μm with the Near Infrared Imager and Slitless Spectrograph and 0.6–3.5 μm with the Near Infrared Spectrograph during transits of TRAPPIST-1b, f, and g. We discover Pα and Brβ line emission and characterize flare continuum at wavelengths from 1–3.5 μm for the first time. Observed lines include Hα, Pα–Pϵ, Brβ, He i λ0.7062 μm, two Ca ii infrared triplet (IRT) lines, and the He i IRT. We observe a reversed Paschen decrement from Pα–Pγ alongside changes in the light-curve shapes of these lines. The continuum of all four flares is well described by blackbody emission with an effective temperature below 5300 K, lower than the temperatures typically observed at optical wavelengths. The 0.6–1 μm spectra were convolved with the Transiting Exoplanet Survey Satellite (TESS) response, enabling us to measure the flare rate of TRAPPIST-1 in the TESS bandpass. We find flares of 1030 erg, large enough to impact transit spectra occur at a rate of flare day−1, ∼10× higher than previous predictions from K2. We measure the amount of flare contamination at 2 μm for the TRAPPIST-1b and f transits to be 500 ± 450 and 2100 ± 400 ppm, respectively. We find up to 80% of flare contamination can be removed, with mitigation most effective from 1.0–2.4 μm. These results suggest transits affected by flares may still be useful for atmospheric characterization efforts.

Gaia Data Release 3

Context. The Gaia Radial Velocity Spectrometer (RVS) provides the unique opportunity of a spectroscopic analysis of millions of stars at medium resolution (λ/Δλ ∼ 11 500) in the near-infrared (845−872 nm). This wavelength range includes the Ca II infrared triplet (IRT) at 850.03, 854.44, and 866.45 nm, which is a good indicator of magnetic activity in the chromosphere of late–type stars. Aims. Here we present the method devised for inferring the Gaia stellar activity index from the analysis of the Ca II IRT in the RVS spectrum, together with its scientific validation. Methods. The Gaia stellar activity index is derived from the Ca II IRT excess equivalent width with respect to a reference spectrum, taking the projected rotational velocity (vsini) into account. We performed scientific validation of the Gaia stellar activity index by deriving a R′IRT index, which is largely independent of the photospheric parameters, and considering the correlation with the R′HK index for a sample of stars. A sample of well-studied pre-main-sequence (PMS) stars is considered to identify the regime in which the Gaia stellar activity index may be affected by mass accretion. The position of these stars in the colour–magnitude diagram and the correlation with the amplitude of the photometric rotational modulation is also scrutinised. Results.Gaia DR3 contains a stellar activity index derived from the Ca II IRT for some 2 × 106 stars in the Galaxy. This represents a ‘gold mine’ for studies on stellar magnetic activity and mass accretion in the solar vicinity. Three regimes of the chromospheric stellar activity are identified, confirming suggestions made by previous authors based on much smaller R′HK datasets. The highest stellar activity regime is associated with PMS stars and RS CVn systems, in which activity is enhanced by tidal interaction. Some evidence of a bimodal distribution in main sequence (MS) stars with Teff ≳ 5000 K is also found, which defines the two other regimes, without a clear gap in between. Stars with 3500 K ≲ Teff ≲ 5000 K are found to be either very active PMS stars or active MS stars with a unimodal distribution in chromospheric activity. A dramatic change in the activity distribution is found for Teff ≲ 3500 K, with a dominance of low activity stars close to the transition between partially- and fully convective stars and a rise in activity down into the fully convective regime.

A multi-wavelength view of the multiple activity cycles of ϵ Eridani

ϵ Eridani is a highly active young K2 star with an activity cycle of about 3 yr established using Ca II H& K line index measurements (SMWO). This relatively short cycle has been demonstrated to be consistent with X-ray and magnetic flux measurements. Recent work suggested a change in the cyclic behaviour. Here, we report new X-ray flux and SMWO measurements and also include SMWO measurements from the historical Mount Wilson program. This results in an observational time baseline of over 50 yr for the SMWO data and of over 7 yr in X-rays. Moreover, we include Ca II infrared triplet (IRT) index measurements (SCa IRT) from 2013 to 2022 in our study. With the extended X-ray data set, we can now detect the short cycle for the first time using a periodogram analysis. Near-simultaneous SMWO data and X-ray fluxes, which are offset by 20 days at most, are moderately strongly correlated when only the lowest activity state (concerning short-term variability) is considered in both diagnostics. In the SMWO data, we find strong evidence for a much longer cycle of about 34 yr and an 11-yr cycle instead of the formerly proposed 12-yr cycle in addition to the known 3-yr cycle. The superposition of the three periods naturally explains the recent drop in SMWO measurements. The two shorter cycles are also detected in the SCa IRT data, although the activity cycles exhibit lower amplitudes in the SCa IRT than in the SMWO data. Finally, the rotation period of ϵ Eri can be found more frequently in the SMWO as well as in the SCa IRT data for times near the minimum of the long cycle. This may be explained by a scenario in which the filling factor for magnetically active regions near cycle maximum is too high to allow for notable short-term variations.

Investigation of stellar magnetic activity using variational autoencoder based on low-resolution spectroscopic survey

ABSTRACT We apply the variational autoencoder (VAE) to the LAMOST-K2 low-resolution spectra to detect the magnetic activity of the stars in the K2 field. After the training on the spectra of the selected inactive stars, the VAE model can efficiently generate the synthetic reference templates needed by the spectral subtraction procedure, without knowing any stellar parameters. Then, we detect the peculiar spectral features, such as chromospheric emissions, strong nebular emissions, and lithium absorptions, in our sample. We measure the emissions of the chromospheric activity indicators, Hα and Ca ii infrared triplet (IRT) lines, to quantify the stellar magnetic activity. The excess emissions of Hα and Ca ii IRT lines of the active stars are correlated well to the rotational periods and the amplitudes of light curves derived from the K2 photometry. We degrade the LAMOST spectra to simulate the slitless spectra of the China Space Station Telescope (CSST) and apply the VAE to the simulated data. For cool active stars, we reveal a good agreement between the equivalent widths of Hα line derived from the spectra with two resolutions. The result indicates the ability of identifying the magnetically active stars in the future CSST survey, which will deliver an unprecedented large data base of low-resolution spectra as well as simultaneous multiband photometry of stars.

Probing the atmosphere of WASP-69 b with low- and high-resolution transmission spectroscopy

Consideration of both low- and high-resolution transmission spectroscopy is key for obtaining a comprehensive picture of exoplanet atmospheres. In studies of transmission spectra, the continuum information is well established with low-resolution spectra, while the shapes of individual lines are best constrained with high-resolution observations. In this work, we aim to merge high- with low-resolution transmission spectroscopy to place tighter constraints on physical parameters of the atmospheres. We present the analysis of three primary transits of WASP-69 b in the visible (VIS) channel of the CARMENES instrument and perform a combined low- and high-resolution analysis using additional data from HARPS-N, OSIRIS/GTC, and WFC3/HST already available in the literature. We investigate the Na I D1 and D2 doublet, Hα, the Ca II infra-red triplet (IRT), and K I λ7699 Å lines, and we monitor the stellar photometric variability by performing long-term photometric observations with the STELLA telescope. During the first CARMENES observing night, we detected the planet Na I D2 and D1 lines at ~7 and ~3σ significance levels, respectively. We measured a D2/D1 intensity ratio of 2.5 ± 0.7, which is in agreement with previous HARPS-N observations. Our modelling of WFC3 and OSIRIS data suggests strong Rayleigh scattering, solar to super-solar water abundance, and a highly muted Na feature in the atmosphere of this planet, in agreement with previous investigations of this target. We use the continuum information retrieved from the low-resolution spectroscopy as a prior to break the degeneracy between the Na abundance, reference pressure, and thermosphere temperature for the high-resolution spectroscopic analysis. We fit the Na I D1 and D2 lines individually and find that the posterior distributions of the model parameters agree with each other within 1σ. Our results suggest that local thermodynamic equilibrium processes can explain the observed D2 /D1 ratio because the presence of haze opacity mutes the absorption features.

H-alpha and Ca ii Infrared Triplet Variations During a Transit of the 23 Myr Planet V1298 Tau c

Abstract Young transiting exoplanets (<100 Myr) provide crucial insight into atmospheric evolution via photoevaporation. However, transmission spectroscopy measurements to determine atmospheric composition and mass loss are challenging due to the activity and prominent stellar disk inhomogeneities present on young stars. We observed a full transit of V1298 Tau c, a 23 Myr, 5.59 R ⊕ planet orbiting a young K0-K1.5 solar analog with GRACES on Gemini North. We were able to measure the Doppler tomographic signal of V1298 Tau c using the Ca ii infrared triplet (IRT) and find a projected obliquity of λ = 5° ± 15°. The tomographic signal is only seen in the chromospherically driven core of the Ca ii IRT, which may be the result of star-planet interactions. Additionally, we find that excess absorption of the Hα line decreases smoothly during the transit. While this could be a tentative detection of hot gas escaping the planet, we find this variation is consistent with similar timescale observations of other young stars that lack transiting planets over similar timescales. We show this variation can also be explained by the presence of starspots with surrounding facular regions. More observations both in and out of the transits of V1298 Tau c are required to determine the nature of the Ca ii IRT and Hα line variations.

CARMENES detection of the Ca II infrared triplet and possible evidence of He I in the atmosphere of WASP-76b

Ultra-hot Jupiters are highly irradiated gas giants with equilibrium temperatures typically higher than 2000 K. Atmospheric studies of these planets have shown that their transmission spectra are rich in metal lines, with some of these metals being ionised due to the extreme temperatures. Here, we use two transit observations of WASP-76b obtained with the CARMENES spectrograph to study the atmosphere of this planet using high-resolution transmission spectroscopy. Taking advantage of the two channels and the coverage of the red and near-infrared wavelength ranges by CARMENES, we focus our analysis on the study of the Ca II infrared triplet (IRT) at 8500 Å and the He I triplet at 10 830 Å. We present the discovery of the Ca II IRT at 7σ in the atmosphere of WASP-76b using the cross-correlation technique, which is consistent with previous detections of the Ca II H&K lines in the same planet, and with the atmospheric studies of other ultra-hot Jupiters reported to date. The low mass density of the planet, and our calculations of the XUV (X-ray and EUV) irradiation received by the exoplanet, show that this planet is a potential candidate to have a He I evaporating envelope and, therefore, we performed further investigations focussed on this aspect. The transmission spectrum around the He I triplet shows a broad and red-shifted absorption signal in both transit observations. However, due to the strong telluric contamination around the He I lines and the relatively low signal-to-noise ratio of the observations, we are not able to unambiguously conclude if the absorption is due to the presence of helium in the atmosphere of WASP-76b, and we consider the result to be only an upper limit. Finally, we revisit the transmission spectrum around other lines such as Na I, Li I, Hα, and K I. The upper limits reported here for these lines are consistent with previous studies.

Measurements of the Ca ii infrared triplet emission lines of pre-main-sequence stars

Abstract We investigated the chromospheric activity of 60 pre-main-sequence (PMS) stars in four molecular clouds and five moving groups. It is considered that strong chromospheric activity is driven by the dynamo processes generated by stellar rotation. In contrast, several researchers have pointed out that the chromospheres of PMS stars are activated by mass accretion from their protoplanetary disks. In this study, the Ca ii infrared triplet (IRT) emission lines were investigated utilizing medium- and high-resolution spectroscopy. The observations were conducted with Nayuta/MALLS and Subaru/HDS. Additionally, archive data obtained by Keck/HIRES, VLT/UVES, and VLT/X-Shooter were used. The small ratios of the equivalent widths indicate that Ca ii IRT emission lines arise primarily in dense chromospheric regions. Seven PMS stars show broad emission lines. Among them, four PMS stars have more than one order of magnitude brighter emission line fluxes compared to the low-mass stars in young open clusters. The four PMS stars have a high mass accretion rate, which indicates that the broad and strong emission results from a large mass accretion. However, most PMS stars exhibit narrow emission lines. No significant correlation was found between the accretion rate and flux of the emission line. The ratios of the surface flux of the Ca ii IRT lines to the stellar bolometric luminosity, $R^{\prime }_{\rm IRT}$, of the PMS stars with narrow emission lines are as large as the largest $R^{\prime }_{\rm IRT}$ of the low-mass stars in the young open clusters. This result indicates that most PMS stars, even in the classical T Tauri star stage, have chromospheric activity similar to zero-age main-sequence stars.

The CARMENES search for exoplanets around M dwarfs

We use spectra from CARMENES, the Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs, to search for periods in chromospheric indices in 16 M0–M2 dwarfs. We measure spectral indices in the Hα, the Ca II infrared triplet (IRT), and the Na I D lines to study which of these indices are best-suited to finding rotation periods in these stars. Moreover, we test a number of different period-search algorithms, namely the string length method, the phase dispersion minimisation, the generalized Lomb–Scargle periodogram, and the Gaussian process regression with quasi-periodic kernel. We find periods in four stars using Hα and in five stars using the Ca II IRT, two of which have not been found before. Our results show that both Hα and the Ca II IRT lines are well suited for period searches, with the Ca II IRT index performing slightly better than Hα. Unfortunately, the Na I D lines are strongly affected by telluric airglow, and we could not find any rotation period using this index. Further, different definitions of the line indices have no major impact on the results. Comparing the different search methods, the string length method and the phase dispersion minimisation perform worst, while Gaussian process models produce the smallest numbers of false positives and non-detections.

The atmosphere of WASP-17b: Optical high-resolution transmission spectroscopy

High-resolution transmission spectroscopy is a method for understanding the chemical and physical properties of upper exoplanetary atmospheres. Due to large absorption cross-sections, resonance lines of atomic sodium D-lines (at 5889.95 and 5895.92 Å) produce large transmission signals. Our aim is to unveil the physical properties of WASP-17b through an accurate measurement of the sodium absorption in the transmission spectrum. We analyze 37 high-resolution spectra observed during a single transit of WASP-17b with the MIKE instrument on the 6.5 m Magellan Telescopes. We exclude stellar flaring activity during the observations by analyzing the temporal variations of Hα and Ca II infrared triplet (IRT) lines. We then obtain the excess absorption light curves in wavelength bands of 0.75, 1, 1.5, and 3 Å around the center of each sodium line (i.e., the light curve approach). We model the effects of differential limb-darkening, and the changing planetary radial velocity on the light curves. We also analyze the sodium absorption directly in the transmission spectrum, which is obtained by dividing in-transit by out-of-transit spectra (i.e., the division approach). We then compare our measurements with a radiative transfer atmospheric model. Our analysis results in a tentative detection of exoplanetary sodium: we measure the width and amplitude of the exoplanetary sodium feature to be σNa = (0.128 ± 0.078) Å and ANa = (1.7 ± 0.9)% in the excess light curve approach and σNa = (0.850 ± 0.034) Å and ANa = (1.3 ± 0.6)% in the division approach. By comparing our measurements with a simple atmospheric model, we retrieve an atmospheric temperature of 15501550 −200+700 K and radius (at 0.1 bar) of 1.81 ± 0.02 RJup for WASP-17b.

Stellar rotation periods determined from simultaneously measured Ca II H&K and Ca II IRT lines

Aims. Previous studies have shown that, for late-type stars, activity indicators derived from the Ca ii infrared-triplet (IRT) lines are correlated with the indicators derived from the Ca ii HK we find good agreement for stars with already existing literature values. In a few cases the computed periodograms show a complicated structure with multiple peaks, meaning that formally different periods are derived in different indices. We show that in one case, this is due to data sampling effects and argue that denser cadence sampling is necessary to provide credible evidence for differential rotation. However, our TIGRE data for HD 101501 shows good evidence for the presence of differential rotation.

Chromospheric activity on the late-type star V1355 Ori using Lijiang 1.8-m and 2.4-m telescopes

We obtained new high-resolution spectra using the Lijiang 1.8-m and 2.4-m telescopes to investigate the chromospheric activities of V1355 Ori as indicated in the behaviors of Ca ii H&K, Hδ, Hγ, Hβ, Na i D1, D2, Hα and Ca ii infrared triplet (IRT) lines. The observed spectra show obvious emissions above the continuum in Ca ii H&K lines, absorptions in the Hδ, Hγ, Hβ and Na i D1, D2 lines, variable behavior (filled-in absorption, partial emission with a core absorption component or emission above the continuum) in the Hα line, and weak self-reversal emissions in the strong filled-in absorptions of the Ca ii IRT lines. We used a spectral subtraction technique to analyze our data. The results show no excess emission in the Hδ and Hγ lines, very weak excess emissions in the Na i D1, D2 lines, excess emission in the Hβ line, clear excess emission in the Hα line, and excess emissions in the Ca ii IRT lines. The value of the ratio of EW8542/EW8498 is in the range 0.9 to 1.7, which implies that chromospheric activity might have been caused by plage events. The value of the ratio EHα/EHβ is above 3, indicating that the Balmer lines would arise from prominence-like material. We also found time variations in light curves associated with equivalent widths of chromospheric activity lines in the Na i D1, D2, Ca ii IRT and Hα lines in particular. These phenomena can be explained by plage events, which are consistent with the behavior of chromospheric activity indicators.

The gaseous debris disk of the white dwarf SDSS J1228+1040

Gaseous and dust debris disks around white dwarfs (WDs) are formed from tidally disrupted planetary bodies. This offers an opportunity to determine the composition of exoplanetary material by measuring element abundances in the accreting WD's atmosphere. A more direct way to do this is through spectral analysis of the disks themselves. Currently, the number of chemical elements detected through disk emission-lines is smaller than that of species detected through lines in the WD atmospheres. We assess the far-ultraviolet (FUV) spectrum of one well-studied object (SDSS J122859.93+104032.9) to search for disk signatures at wavelengths <1050 angstrom, where the broad absorption lines of the Lyman series effectively block the WD photospheric flux. We performed FUV observations (950-1240 angstrom) with the Hubble Space Telescope/Cosmic Origins Spectrograph and used archival optical spectra. We compared them with non-local thermodynamic equilibrium model spectra. In addition, we investigate the Ca II infrared triplet (IRT) line profiles to constrain disk geometry and composition. No disk emission-lines were detected in the FUV spectrum, indicating that the disk effective temperature is about 5000K. The long-time variability of the Ca II IRT was reproduced with a precessing disk model of bulk Earth-like composition, having a surface mass density of 0.3g/cm2 and an extension from 55 to 90 WD radii. The disk has a spiral shape that precesses with a period of approximately 37 years, confirming previous results.

Chromospheric activity and rotational modulation of the RS Canum Venaticorum binary V711 Tauri during 1998–2004

We present long-term high-resolution spectroscopic observations of the very active RS Canum Venaticorum-type star V711 Tau, obtained during several observing runs from 1998 to 2004, and study its chromospheric activity. Using the spectral subtraction technique, several optical chromospheric activity indicators [including the He I D-3, Na I D-1, D-2, H alpha and Ca II infrared triplet (IRT) lines] formed at different atmospheric heights are analysed. Strong chromospheric emission supports earlier results that indicate that V711 Tau is a very active system. Two large optical flares were detected during our observations. The results suggest that the main part of chromospheric emission is attributed to the primary star of the system. The secondary also presents weak emission but is less active. The ratios of EW8542/EW8498 indicate that Ca II IRT emission arises predominantly from plage-like regions. We have found rotational modulation of chromospheric activity in the H alpha and Ca II IRT lines, which suggests the presence of the chromospheric active longitudes over the surface of V711 Tau. Two active longitudes separated by about 180 degrees were observed to dominate the activity, and the so-called flip-flop phenomenon was seen during our observations. Moreover, the chromospheric activity level shows a long-term variation that gradually increases from a deep minimum near the year 2002. A close spatial connection of photospheric spots and chromospheric active regions in both short and long timescales was found for V711 Tau.

CHROMOSPHERIC ACTIVITY AND ROTATIONAL MODULATION ON THE YOUNG, SINGLE K2 DWARF LQ Hya

High-resolution echelle spectra of LQ Hya, obtained during several observing runs from 2006 to 2012, have been analyzed to study its chromospheric activity. Using the spectral subtraction technique, we derived information about chromospheric activity of LQ Hya from several optical chromospheric activity indicators (including the H-beta, He I D-3, Na I D-1, D-2, H alpha, and Ca II infrared triplet (IRT) lines). No optical flares were found during our observations. The equivalent widths (EWs) of the excess emissions in the chromospheric activity lines have been measured. The ratios of EW8542/EW8498 are generally small, which indicates that the Ca II IRT emission arises from plage-like regions, while the EH alpha/EH beta values suggest that the emission of the Balmer lines is due to both plage and prominence structures for the observations in 2012. We find that clear rotational modulation of chromospheric emission exists, which suggests the presence and change of chromospheric active regions over the surface of LQ Hya. Moreover, the active regions were associated with the photospheric spots in spatial structure.

High-velocity features in the spectra of the Type Ia supernova SN 1999ee: a property of the explosion or evidence of circumstellar interaction?

The near-maximum spectra of the Type Ia supernova SN 1999ee are reviewed. Two narrow absorption features corresponding to the strongest component of the Ca II infrared (IR) triplet appear in the spectra from 7 d before to 2 d after the B-band maximum, at a high velocity (∼22 000 km s -1 ). Before these features emerge, the Ca II IR triplet has an anomalously high velocity, indicating that the narrow features were still blended with the main, photospheric component. High-velocity Can absorption has been observed in other Type Ia supernovae, but usually detached from the photospheric component. Furthermore, the Si II 6355-A line is observed at a comparably high velocity (∼20 000 km s -1 ) 9 and 7 d before the B maximum, but then it suddenly shifts to much lower velocities. Synthetic spectra are used to reproduce the data under various scenarios. An abundance enhancement requires an outer region dominated by Si and Ca, the origin of which is not easy to explain in terms of nuclear burning. A density enhancement leads to a good reproduction of the spectral evolution if a mass of ∼0.10 M○. is added at velocities between 16 000 and 28 000 km s -1 , and it may result from a perturbation, possibly angular, of the explosion. An improved match to the Can IR triplet at the earliest epoch can be obtained if the outermost part of this modified density profile is assumed to be dominated by H (∼0.004 M○. above 24000 km s -1 ). Line broadening is then the result of increased electron scattering. This H may be the result of interaction between the ejecta and circumstellar material.

Spectroscopy of Mira Variables at Different Phases.

view Abstract Citations (12) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopy of Mira Variables at Different Phases. Castelaz, Michael W. ; Luttermoser, Donald G. Abstract Spectroscopic measurements of Mira variable stars, as a function of phase, probe the stellar atmospheres and underlying pulsation mechanisms. Modeling the atmospheres is difficult due to the hydrodynamic nature of the gas as deduced from the large light variations and velocity measurements of various spectral lines. Many questions still need to be resolved concerning the atmospheres of these stars. Are the depths of formation of the molecular species such as TiO, VO, and ZrO produced in an extended region above the layers where Balmer line emission occurs or below this shocked region? What is the explanation for the Balmer-line increment, where the strongest Balmer line at phase zero is Hδ and not Hα? Furthermore, why is the Hɛ line virtually absent in the spectra of Miras when the other Balmer lines are strong? A new program of low resolution (1.08 Å/pixel) spectroscopy from about 6000Å to 8750Å is presented in this paper. The spectra are taken in a region which includes Hα, TiO, VO, ZrO, and the Ca II infrared (IR) triplet. Spectra of nine Mira variables are presented. Seven Mira variable stars (o Cet [Mira], U Ori, R Leo, V CVn, R CVn, V Boo, and χ Cyg) were observed at more than one phase. Two other Mira variables (R Tri and R Gem) were observed at a single phase, but both show strong Hα emission. In this paper, we investigate the final question listed above by noting variations in the Ca II IR triplet in relationship with Hα variations as a function of phase. These preliminary observations suggest that Hɛ's observational characteristics result from an interaction of Hɛ photons with the Ca II H line. Publication: The Astronomical Journal Pub Date: October 1997 DOI: 10.1086/118589 Bibcode: 1997AJ....114.1584C Keywords: STARS: ATMOSPHERES; STARS: VARIABLES: OTHER full text sources ADS | data products SIMBAD (9)