arXiv subjects

S. Drew Chojnowski

Publications and source records attributed to S. Drew Chojnowski.

At least 37 records · Page 2Linked to original sources

arXiv2018

HD 63021: An Ae Star with X-ray Flux

Balmer and Fe II (42) multiplet emission were discovered in a spectrum of HD 63021 on 10 April (UTC), 2018. Subsequent observations revealed variability in both photospheric absorption lines and Balmer line emission. In addition, it is an X-ray source, with a luminosity that is consistent with either a very strong stellar wind, or else the presence of a compact binary companion. Spectroscopic and photometric followup are planned to determine the nature of this source.

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arXiv2018

Outbursts and Disk Variability in Be Stars

In order to study the growth and evolution of circumstellar disks around classical Be stars, we analyze optical time-series photometry from the KELT survey with simultaneous infrared and visible spectroscopy from the APOGEE survey and BeSS database for a sample of 160 Galactic classical Be stars. The systems studied here show variability including transitions from a diskless to a disk-possessing state (and vice versa), and persistent disks that vary in strength, being replenished at either regularly or irregularly occurring intervals. We detect disk-building events (outbursts) in the light curves of 28\% of our sample. Outbursts are more commonly observed in early- (57\%), compared to mid- (27\%) and late-type (8\%) systems. A given system may show anywhere between 0 -- 40 individual outbursts in its light curve, with amplitudes ranging up to $\sim$0.5 mag and event durations between $\sim$2 -- 1000 days. We study how both the photometry and spectroscopy change together during active episodes of disk growth or dissipation, revealing details about the evolution of the circumstellar environment. We demonstrate that photometric activity is linked to changes in the inner disk, and show that, at least in some cases, the disk growth process is asymmetrical. Observational evidence of Be star disks both growing and clearing from the inside out is presented. The duration of disk buildup and dissipation phases are measured for 70 outbursts, and we find that the average outburst takes about twice as long to dissipate as it does to build up in optical photometry. Our analysis hints that dissipation of the inner disk occurs relatively slowly for late-type Be stars.

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arXiv2017

IN-SYNC. V. Stellar kinematics and dynamics in the Orion A Molecular Cloud

The kinematics and dynamics of young stellar populations enable us to test theories of star formation. With this aim, we continue our analysis of the SDSS-III/APOGEE IN-SYNC survey, a high resolution near infrared spectroscopic survey of young clusters. We focus on the Orion A star-forming region, for which IN-SYNC obtained spectra of $\sim2700$ stars. In Paper IV we used these data to study the young stellar population. Here we study the kinematic properties through radial velocities ($v_r$). The young stellar population remains kinematically associated with the molecular gas, following a $\sim10\:{\rm{km\:s}}^{-1}$ gradient along filament. However, near the center of the region, the $v_r$ distribution is slightly blueshifted and asymmetric; we suggest that this population, which is older, is slightly in foreground. We find evidence for kinematic subclustering, detecting statistically significant groupings of co-located stars with coherent motions. These are mostly in the lower-density regions of the cloud, while the ONC radial velocities are smoothly distributed, consistent with it being an older, more dynamically evolved cluster. The velocity dispersion $σ_v$ varies along the filament. The ONC appears virialized, or just slightly supervirial, consistent with an old dynamical age. Here there is also some evidence for on-going expansion, from a $v_r$--extinction correlation. In the southern filament, $σ_v$ is $\sim2$--$3$ times larger than virial in the L1641N region, where we infer a superposition along the line of sight of stellar sub-populations, detached from the gas. On the contrary, $σ_v$ decreases towards L1641S, where the population is again in agreement with a virial state.

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arXiv2017

IN-SYNC VI. Identification and Radial Velocity Extraction for 100+ Double-Lined Spectroscopic Binaries in the APOGEE/IN-SYNC Fields

We present radial velocity measurements for 70 high confidence, and 34 potential binary systems in fields containing the Perseus Molecular Cloud, Pleiades, NGC 2264, and the Orion A star forming region. 18 of these systems have been previously identified as binaries in the literature. Candidate double-lined spectroscopic binaries (SB2s) are identified by analyzing the cross-correlation functions (CCFs) computed during the reduction of each APOGEE spectrum. We identify sources whose CCFs are well fit as the sum of two Lorentzians as likely binaries, and provide an initial characterization of the system based on the radial velocities indicated by that dual fit. For systems observed over several epochs, we present mass ratios and systemic velocities; for two systems with observations on eight or more epochs, and which meet our criteria for robust orbital coverage, we derive initial orbital parameters. The distribution of mass ratios for multi-epoch sources in our sample peaks at q=1, but with a significant tail toward lower q values. Tables reporting radial velocities, systemic velocities, and mass ratios are provided online. We discuss future improvements to the radial velocity extraction method we employ, as well as limitations imposed by the number of epochs currently available in the APOGEE database. The Appendix contains brief notes from the literature on each system in the sample, and more extensive notes for select sources of interest.

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arXiv2016

Fading AGN Candidates: AGN Histories and Outflow Signatures

We consider energy budgets and radiative history of 8 fading AGN, identified from mismatch between the ionizion of very extended (>10 kpc) ionized clouds and the luminosity of the nucleus viewed directly. All show significant fading on ~50,000-year timescales. We explore the use of minimum ionizing luminosity Q derived from photoionization balance in the brightest pixels in H-alpha at each projected radius. Tests using PG QSOs, and one target with detailed photoionization modeling, suggest that we can derive useful histories of individual AGN; the minimum ionizing luminosity is always an underestimate and subject to fine structure in the ionized material. These tests suggest that the underestimation from the upper envelope of Q values is roughly constant for a given object. These AGN show rapid drops and standstills; the common feature is a rapid drop in the last 20,000 years before our view of the nucleus. E-folding timescales are mostly thousands of years, with a few episodes as short as 400. In the limit of largely obscured AGN, we find additional evidence for fading, comparing lower limits from recombination balance and the maximum luminosities derived from from infrared fluxes. We compare these long-term light curves to simulations of AGN accretion; the strongest variations on these timespans are seen in models with strong and local feedback. Gemini integral-field optical spectroscopy shows a very limited role for outflows in these structures. While rings and loops of emission are common, their kinematic structure shows some to be in regular rotation. UGC 7342 exhibits local signatures of outflows <300 km/s, largely associated with very diffuse emission. Only in the Teacup AGN do we see outflow signatures of order 1000 km/s. Clouds around these fading AGN consist largely of tidal debris being externally illuminated but not displaced by AGN outflows. (Abridged)

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arXiv2016

Chemical tagging with APOGEE: Discovery of a large population of N-rich stars in the inner Galaxy

Formation of globular clusters (GCs), the Galactic bulge, or galaxy bulges in general, are important unsolved problems in Galactic astronomy. Homogeneous infrared observations of large samples of stars belonging to GCs and the Galactic bulge field are one of the best ways to study these problems. We report the discovery by APOGEE of a population of field stars in the inner Galaxy with abundances of N, C, and Al that are typically found in GC stars. The newly discovered stars have high [N/Fe], which is correlated with [Al/Fe] and anti-correlated with [C/Fe]. They are homogeneously distributed across, and kinematically indistinguishable from, other field stars in the same volume. Their metallicity distribution is seemingly unimodal, peaking at [Fe/H]~-1, thus being in disagreement with that of the Galactic GC system. Our results can be understood in terms of different scenarios. N-rich stars could be former members of dissolved GCs, in which case the mass in destroyed GCs exceeds that of the surviving GC system by a factor of ~8. In that scenario, the total mass contained in so-called "first-generation" stars cannot be larger than that in "second-generation" stars by more than a factor of ~9 and was certainly smaller. Conversely, our results may imply the absence of a mandatory genetic link between "second generation" stars and GCs. Last, but not least, N-rich stars could be the oldest stars in the Galaxy, the by-products of chemical enrichment by the first stellar generations formed in the heart of the Galaxy.

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arXiv2016

Companions to APOGEE Stars I: A Milky Way-Spanning Catalog of Stellar and Substellar Companion Candidates and their Diverse Hosts

In its three years of operation, the Sloan Digital Sky Survey (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE-1) observed $>$14,000 stars with enough epochs over a sufficient temporal baseline for the fitting of Keplerian orbits. We present the custom orbit-fitting pipeline used to create this catalog, which includes novel quality metrics that account for the phase and velocity coverage of a fitted Keplerian orbit. With a typical RV precision of $\sim100-200$ m s$^{-1}$, APOGEE can probe systems with small separation companions down to a few Jupiter masses. Here we present initial results from a catalog of 382 of the most compelling stellar and substellar companion candidates detected by APOGEE, which orbit a variety of host stars in diverse Galactic environments. Of these, 376 have no previously known small separation companion. The distribution of companion candidates in this catalog shows evidence for an extremely truncated brown dwarf (BD) desert with a paucity of BD companions only for systems with $a < 0.1-0.2$ AU, with no indication of a desert at larger orbital separation. We propose a few potential explanations of this result, some which invoke this catalog's many small separation companion candidates found orbiting evolved stars. Furthermore, 16 BD and planet candidates have been identified around metal-poor ([Fe/H] $< -0.5$) stars in this catalog, which may challenge the core accretion model for companions $>10 M_{Jup}$. Finally, we find all types of companions are ubiquitous throughout the Galactic disk with candidate planetary-mass and BD companions to distances of $\sim6$ and $\sim16$ kpc, respectively.

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arXiv2015

IN-SYNC IV - The Young Stellar Population in the Orion A Molecular Cloud

We present the results of the SDSS APOGEE INfrared Spectroscopy of Young Nebulous Clusters program (IN-SYNC) survey of the Orion A molecular cloud. This survey obtained high resolution near infrared (NIR) spectroscopy of about 2700 young pre-main sequence stars throughout the region, acquired across five distinct fields spanning 6deg field of view (FOV). With these spectra, we have measured accurate stellar parameters (T_eff, log g, v sin i) and extinctions, and placed the sources in the Hertzsprung-Russel Diagram (HRD). We have also extracted radial velocities for the kinematic characterization of the population. We compare our measurements with literature results for a sub-sample of targets in order to assess the performances and accuracy of the survey. Source extinction shows evidence for dust grains that are larger than those in the diffuse interstellar medium (ISM): we estimate an average R_V=5.5 in the region. Importantly, we find a clear correlation between HRD inferred ages and spectroscopic surface-gravity inferred ages. This clearly indicates a real spread of stellar radii at fixed temperature, and together with additional correlations with extinction and with disk presence, strongly suggests a real spread of ages large than a few Myr. Focussing on the young population around NGC1980 iota Ori, which has previously been suggested to be a separate, foreground, older cluster, we confirm its older (5Myr) age and low A_V, but considering that its radial velocity distribution is indistinguishable from the Orion A's population, we suggest that NGC1980 is part of Orion A's star formation activity. Based on their stellar parameters and kinematic properties, we identify 383 new candidate members of Orion A, most of which are diskless sources in areas of the region poorly studied by previous works.

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arXiv2015

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three year observing campaign on the Sloan 2.5-m Telescope, APOGEE has collected a half million high resolution (R~22,500), high S/N (>100), infrared (1.51-1.70 microns) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design---hardware, field placement, target selection, operations---and gives an overview of these aspects as well as the data reduction, analysis and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12, all of the APOGEE data products are now publicly available.

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arXiv2015

An Infrared Diffuse Circumstellar Band? The Unusual 1.5272 Micron DIB In the Red Square Nebula

The molecular carriers of the ubiquitous absorption features called the diffuse interstellar bands (DIBs) have eluded identification for many decades, in part because of the enormous parameter space spanned by the candidates and the limited set of empirical constraints afforded by observations in the diffuse interstellar medium. Detection of these features in circumstellar regions, where the environmental properties are more easily measured, is thus a promising approach to understanding the chemical nature of the carriers themselves. Here, using high resolution spectra from the APOGEE survey, we present an analysis of the unusually asymmetric 1.5272 micron DIB feature along the sightline to the Red Square Nebula and demonstrate the likely circumstellar origin of about half of the DIB absorption in this line of sight. This interpretation is supported both by the velocities of the feature components and by the ratio of foreground to total reddening along the line of sight. The Red Square Nebula sightline offers the unique opportunity to study the behavior of DIB carriers in a constrained environment and thus to shed new light on the carriers themselves.

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arXiv2015

IN-SYNC III: The dynamical state of IC 348 - A super-virial velocity dispersion and a puzzling sign of convergence

Most field stars will have encountered the highest stellar density and hence the largest number of interactions in their birth environment. Yet the stellar dynamics during this crucial phase are poorly understood. Here we analyze the radial velocities measured for 152 out of 380 observed stars in the 2-6 Myr old star cluster IC 348 as part of the SDSS-III APOGEE. The radial velocity distribution of these stars is fitted with one or two Gaussians, convolved with the measurement uncertainties including binary orbital motions. Including a second Gaussian improves the fit; the high-velocity outliers that are best fit by this second component may either (1) be contaminants from the nearby Perseus OB2 association, (2) be a halo of ejected or dispersing stars from IC 348, or (3) reflect that IC 348 has not relaxed to a Gaussian velocity distribution. We measure a velocity dispersion for IC 348 of $0.72 \pm 0.07$ km s$^{-1}$ (or $0.64 \pm 0.08$ km s$^{-1}$ if two Gaussians are fitted), which implies a supervirial state, unless the gas contributes more to the gravitational potential than expected. No evidence is found for a dependence of this velocity dispersion on distance from the cluster center or stellar mass. We also find that stars with lower extinction (in the front of the cloud) tend to be redshifted compared with stars with somewhat higher extinction (towards the back of the cloud). This data suggests that the stars in IC 348 are converging along the line of sight. We show that this correlation between radial velocity and extinction is unlikely to be spuriously caused by the small cluster rotation of $0.024 \pm 0.013$ km s$^{-1}$ arcmin$^{-1}$ or by correlations between the radial velocities of neighboring stars. This signature, if confirmed, will be the first detection of line-of-sight convergence in a star cluster(...)

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arXiv2015

The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III

The third generation of the Sloan Digital Sky Survey (SDSS-III) took data from 2008 to 2014 using the original SDSS wide-field imager, the original and an upgraded multi-object fiber-fed optical spectrograph, a new near-infrared high-resolution spectrograph, and a novel optical interferometer. All the data from SDSS-III are now made public. In particular, this paper describes Data Release 11 (DR11) including all data acquired through 2013 July, and Data Release 12 (DR12) adding data acquired through 2014 July (including all data included in previous data releases), marking the end of SDSS-III observing. Relative to our previous public release (DR10), DR12 adds one million new spectra of galaxies and quasars from the Baryon Oscillation Spectroscopic Survey (BOSS) over an additional 3000 sq. deg of sky, more than triples the number of H-band spectra of stars as part of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE), and includes repeated accurate radial velocity measurements of 5500 stars from the Multi-Object APO Radial Velocity Exoplanet Large-area Survey (MARVELS). The APOGEE outputs now include measured abundances of 15 different elements for each star. In total, SDSS-III added 2350 sq. deg of ugriz imaging; 155,520 spectra of 138,099 stars as part of the Sloan Exploration of Galactic Understanding and Evolution 2 (SEGUE-2) survey; 2,497,484 BOSS spectra of 1,372,737 galaxies, 294,512 quasars, and 247,216 stars over 9376 sq. deg; 618,080 APOGEE spectra of 156,593 stars; and 197,040 MARVELS spectra of 5,513 stars. Since its first light in 1998, SDSS has imaged over 1/3 of the Celestial sphere in five bands and obtained over five million astronomical spectra.

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arXiv2015

HST Imaging of Fading AGN Candidates I: Host-Galaxy Properties and Origin of the Extended Gas

We present narrow- and medium-band HST imaging, with additional supporting ground-based data, for 8 galaxies identified as hosting fading AGN. These have AGN-ionized gas projected >10 kpc from the nucleus, and significant shortfall of ionizing radiation between the distant gas and the AGN, indicating fading AGN on ~50,000-year timescales. Every system shows evidence of ongoing or past interactions; a similar sample of obscured AGN with extended ionized clouds shares this incidence of disturbances. Several systems show multiple dust lanes in different orientations, broadly fit by differentially precessing disks of accreted material ~1.5 Gyr after initial arrival. The gas has lower metallicity than the nuclei; three systems have abundances uniformly well below solar, consistent with an origin in tidally disrupted low-luminosity galaxies, while some systems have more nearly solar abundances (accompanied by such signatures as multiple Doppler components), which may suggest redistribution of gas by outflows within the host galaxies themselves. These aspects are consistent with a tidal origin for the extended gas in most systems, although the ionized gas and stellar tidal features do not always match closely. In contrast to clouds near radio-loud AGN, these are dominated by rotation, in some cases in warped disks. Outflows are important only in localized regions near some of the AGN. In UGC 7342 and UGC 11185, luminous star clusters are seen within projected ionization cones, potentially triggered by outflows. As in the discovery example Hanny's Voorwerp/IC 2497, some clouds lack a strong correlation between H-alpha surface brightness and ionization parameter, indicating unresolved fine structure. Together with thin coherent filaments spanning several kpc, persistence of these structures over their orbital lifetimes may require a role for magnetic confinement. (Abridged)

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arXiv2014

IN-SYNC II: Virial Stars from Sub-Virial Cores -- The Velocity Dispersion of Embedded Pre-Main-Sequence Stars in NGC 1333

The initial velocity dispersion of newborn stars is a major unconstrained aspect of star formation theory. Using near-infrared spectra obtained with the APOGEE spectrograph, we show that the velocity dispersion of young (1-2 Myr) stars in NGC 1333 is 0.92+/-0.12 km/s after correcting for measurement uncertainties and the effect of binaries. This velocity dispersion is consistent with the virial velocity of the region and the diffuse gas velocity dispersion, but significantly larger than the velocity dispersion of the dense, star-forming cores, which have a sub-virial velocity dispersion of 0.5 km/s. Since the NGC 1333 cluster is dynamically young and deeply embedded, this measurement provides a strong constraint on the initial velocity dispersion of newly-formed stars. We propose that the difference in velocity dispersion between stars and dense cores may be due to the influence of a 70 micro-Gauss magnetic field acting on the dense cores, or be the signature of a cluster with initial sub-structure undergoing global collapse.

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arXiv2014

High-resolution, H band Spectroscopy of Be Stars with SDSS-III/APOGEE: I. New Be Stars, Line Identifications, and Line Profiles

APOGEE has amassed the largest ever collection of multi-epoch, high-resolution (R~22,500), H-band spectra for B-type emission line (Be) stars. The 128/238 APOGEE Be stars for which emission had never previously been reported serve to increase the total number of known Be stars by ~6%. We focus on identification of the H-band lines and analysis of the emission peak velocity separations (v_p) and emission peak intensity ratios (V/R) of the usually double-peaked H I and non-hydrogen emission lines. H I Br11 emission is found to preferentially form in the circumstellar disks at an average distance of ~2.2 stellar radii. Increasing v_p toward the weaker Br12--Br20 lines suggests these lines are formed interior to Br11. By contrast, the observed IR Fe II emission lines present evidence of having significantly larger formation radii; distinctive phase lags between IR Fe II and H I Brackett emission lines further supports that these species arise from different radii in Be disks. Several emission lines have been identified for the first time including ~16895, a prominent feature in the spectra for almost a fifth of the sample and, as inferred from relatively large v_p compared to the Br11-Br20, a tracer of the inner regions of Be disks. Unlike the typical metallic lines observed for Be stars in the optical, the H-band metallic lines, such as Fe II 16878, never exhibit any evidence of shell absorption, even when the H I lines are clearly shell-dominated. The first known example of a quasi-triple-peaked Br11 line profile is reported for HD 253659, one of several stars exhibiting intra- and/or extra-species V/R and radial velocity variation within individual spectra. Br11 profiles are presented for all discussed stars, as are full APOGEE spectra for a portion of the sample.

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arXiv2014

IN-SYNC I: Homogeneous Stellar Parameters from High Resolution APOGEE Spectra for Thousands of Pre-main Sequence Star

Over two years 8,859 high-resolution H-band spectra of 3,493 young (1 - 10 Myr) stars were gathered by the multi-object spectrograph of the APOGEE project as part of the IN-SYNC ancillary program of that SDSS-III survey. Here we present the forward modeling approach used to derive effective temperatures, surface gravities, radial velocities, rotational velocities, and H-band veiling from these near-infrared spectra. We discuss in detail the statistical and systematic uncertainties in these stellar parameters. In addition we present accurate extinctions by measuring the E(J-H) of these young stars with respect to the single-star photometric locus in the Pleiades. Finally we identify an intrinsic stellar radius spread of about 25% for late-type stars in IC 348 using three (nearly) independent measures of stellar radius, namely the extinction-corrected J-band magnitude, the surface gravity and the $R \sin i$ from the rotational velocities and literature rotation periods. We exclude that this spread is caused by uncertainties in the stellar parameters by showing that the three estimators of stellar radius are correlated, so that brighter stars tend to have lower surface gravities and larger $R \sin i$ than fainter stars at the same effective temperature. Tables providing the spectral and photometric parameters for the Pleiades and IC 348 have been provided online.

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arXiv2014

The APOGEE red-clump catalog: Precise distances, velocities, and high-resolution elemental abundances over a large area of the Milky Way's disk

The Sloan Digital Sky Survey III's Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a high-resolution near-infrared spectroscopic survey covering all of the major components of the Galaxy, including the dust-obscured regions of the inner Milky Way disk and bulge. Here we present a sample of 10,341 likely red-clump stars (RC) from the first two years of APOGEE operations, selected based on their position in color-metallicity-surface-gravity-effective-temperature space using a new method calibrated using stellar-evolution models and high-quality asteroseismology data. The narrowness of the RC locus in color-metallicity-luminosity space allows us to assign distances to the stars with an accuracy of 5 to 10%. The sample extends to typical distances of about 3 kpc from the Sun, with some stars out to 8 kpc, and spans a volume of approximately 100 kpc^3 over 5 kpc <~ R <~ 14 kpc, |Z| <~ 2 kpc, and -15 deg <~ Galactocentric azimuth <~ 30 deg. The APOGEE red-clump (APOGEE-RC) catalog contains photometry from 2MASS, reddening estimates, distances, line-of-sight velocities, stellar parameters and elemental abundances determined from the high-resolution APOGEE spectra, and matches to major proper motion catalogs. We determine the survey selection function for this data set and discuss how the RC selection samples the underlying stellar populations. We use this sample to limit any azimuthal variations in the median metallicity within the ~45 degree-wide azimuthal region covered by the current sample to be <= 0.02 dex, which is more than an order of magnitude smaller than the radial metallicity gradient. This result constrains coherent non-axisymmetric flows within a few kpc from the Sun.

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arXiv2014

Discovery of Two Rare Rigidly-Rotating Magnetosphere Stars in the APOGEE Survey

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) - one of the Sloan Digital Sky Survey III programs -- is using near-infrared spectra of $\sim 100,000$ red giant branch star candidates to study the structure of the Milky Way. In the course of the survey, APOGEE also acquires spectra of hot field stars to serve as telluric calibrators for the primary science targets. We report the serendipitous discovery of two rare, fast-rotating B stars of the $σ$ Ori E type among those blue field stars observed during the first year of APOGEE operations. Both of the discovered stars display the spectroscopic signatures of the rigidly rotating magnetospheres (RRM) common to this class of highly-magnetized ($B \sim 10$ kiloGauss) stars, increasing the number of known RRM stars by $\sim 10 \%$. One (HD 345439) is a main-sequence B star with unusually strong He absorption (similar to $σ$ Ori E), while the other (HD 23478) fits a "He-normal" B3IV classification. We combine the APOGEE discovery spectra with other optical and near-infrared spectra of these two stars, and of $σ$ Ori E itself, to show how near-infrared spectroscopy can be a uniquely powerful tool for discovering more of these rare objects, which may show little/no RRM signatures in their optical spectra. We discuss the potential for further discovery of $σ$ Ori E type stars, as well as the implications of our discoveries for the population of these objects and insights into their origin and evolution.

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