scholarly journals Discovery of 2716 hot emission-line stars from LAMOST DR5

2021 ◽  
Vol 21 (11) ◽  
pp. 288
Author(s):  
Baskaran Shridharan ◽  
Blesson Mathew ◽  
Sabu Nidhi ◽  
Ravikumar Anusha ◽  
Roy Arun ◽  
...  
Keyword(s):  
Emission Line ◽  
Near Infrared ◽  
Community Study ◽  
Be Stars ◽  
Mid Infrared ◽  
Data Release ◽  
Homogeneous Set ◽  
Stellar Parameter ◽  
Infrared Wavelengths

Abstract We present a catalog of 3339 hot emission-line stars (ELSs) identified from 451 695 O, B and A type spectra, provided by LAMOST Data Release 5 (DR5). We developed an automated Python routine that identified 5437 spectra having a peak between 6561 and 6568 Å. False detections and bad spectra were removed, leaving 4138 good emission-line spectra of 3339 unique ELSs. We re-estimated the spectral types of 3307 spectra as the LAMOST Stellar Parameter Pipeline (LASP) did not provide accurate spectral types for these emission-line spectra. As Herbig Ae/Be stars exhibit higher excess in near-infrared and mid-infrared wavelengths than classical Ae/Be stars, we relied on 2MASS and WISE photometry to distinguish them. Finally, we report 1089 classical Be, 233 classical Ae and 56 Herbig Ae/Be stars identified from LAMOST DR5. In addition, 928 B[em]/A[em] stars and 240 CAe/CBe potential candidates are identified. From our sample of 3339 hot ELSs, 2716 ELSs identified in this work do not have any record in the SIMBAD database and they can be considered as new detections. Identification of such a large homogeneous set of emission-line spectra will help the community study the emission phenomenon in detail without worrying about the inherent biases when compiling from various sources.

scholarly journals Near-infrared excess and emission characteristics of classical Be stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 404-405
Author(s):  
Chien-De Lee ◽  
Wen-Ping Chen ◽  
Daisuke Kinoshita
Keyword(s):  
Emission Line ◽  
Near Infrared ◽  
Thermal Emission ◽  
Temporal Correlation ◽  
Circumstellar Dust ◽  
Emission Characteristics ◽  
Spectral Features ◽  
Be Stars ◽  
Infrared Excess ◽  
Fast Rotating

AbstractClassical Be (CBe) stars are fast-rotating emission-line stars associated with infrared excess often attributed to plasma free-free emission. A few with exceptionally large near-infrared excess, namely with (J–H) and (H–Ks) both greater than 0.6 mag, however, must be accounted for by thermal emission from circumstellar dust. From 2007 to 2009, spectra of more than 100 CBe stars have been collected. We present some of these spectra and discuss how temporal correlation (or lack of) among spectral features would provide possible diagnosis of the origin of the CBe phenomena.

scholarly journals A NEW METHOD FOR ACTIVELY TUNING FBG'S TO PARTICULAR INFRARED WAVELENGTHS FOR OH EMISSION LINES SUPPRESSION

2019 ◽  
Vol 55 (2) ◽  
pp. 351-361 ◽  
Author(s):  
R. Benítez-Álvarez ◽  
F. Martínez-Piñón ◽  
V. G. Orlov
Keyword(s):  
Experimental Study ◽  
Emission Line ◽  
Conceptual Design ◽  
Near Infrared ◽  
Fiber Optic ◽  
Emission Lines ◽  
New Method ◽  
Bragg Wavelength ◽  
Linear Deformation ◽  
Infrared Wavelengths

This paper presents the conceptual design for a new method for the suppression of OH emission lines at near-infrared (NIR) wavelengths by actively adjusting the aperiodic fiber optic Bragg gratings tension. First, we prepared an experimental study in which we simulated an OH emission line using a semiconductor laser at 1548.43 nm and a commercial FBG, with a Bragg wavelength of 1547.76 nm. We demonstrated that the grating Bragg wavelength can be adjusted by controlling the linear deformation of the fiber with a force in the range of 0 to 53.88 gf (0.528 N) that provides a sensitivity of 0.014 nm g −1 . Second, we proposed the design of a system connected to the telescope instrumentation, with the different stages that would allow monitoring the suppression of emission lines.

scholarly journals The Sloan Digital Sky Survey Quasar Catalog: Fourteenth data release

2018 ◽  
Vol 613 ◽  
pp. A51 ◽  
Author(s):  
Isabelle Pâris ◽  
Patrick Petitjean ◽  
Éric Aubourg ◽  
Adam D. Myers ◽  
Alina Streblyanska ◽  
...  
Keyword(s):  
Emission Line ◽  
Near Infrared ◽  
Wavelength Region ◽  
Principal Component ◽  
Sloan Digital Sky Survey ◽  
Large Area ◽  
Robust Identification ◽  
Broad Absorption Line ◽  
Sky Survey ◽  
Data Release

We present the data release 14 Quasar catalog (DR14Q) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV). This catalog includes all SDSS-IV/eBOSS objects that were spectroscopically targeted as quasar candidates and that are confirmed as quasars via a new automated procedure combined with a partial visual inspection of spectra, have luminosities Mi [z = 2] < −20.5 (in a Λ CDM cosmology with H0 = 70 km s−1 Mpc−1, Ω M =0.3, and Ω Λ = 0.7), and either display at least one emission line with a full width at half maximum larger than 500 km s−1 or, if not, have interesting/complex absorption features. The catalog also includes previously spectroscopically-confirmed quasars from SDSS-I, II, and III. The catalog contains 526 356 quasars (144 046 are new discoveries since the beginning of SDSS-IV) detected over 9376 deg2 (2044 deg2 having new spectroscopic data available) with robust identification and redshift measured by a combination of principal component eigenspectra. The catalog is estimated to have about 0.5% contamination. Redshifts are provided for the Mg II emission line. The catalog identifies 21 877 broad absorption line quasars and lists their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra, covering the wavelength region 3610–10 140 Å at a spectral resolution in the range 1300 < R < 2500, can be retrieved from the SDSS Science Archiver Server.

scholarly journals On the variation of Fourier parameters for Galactic and LMC Cepheids at optical, near-infrared and mid-infrared wavelengths

2015 ◽  
Vol 447 (4) ◽  
pp. 3342-3360 ◽  
Author(s):  
Anupam Bhardwaj ◽  
Shashi M. Kanbur ◽  
Harinder P. Singh ◽  
Lucas M. Macri ◽  
Chow-Choong Ngeow
Keyword(s):  
Near Infrared ◽  
Mid Infrared ◽  
Infrared Wavelengths

scholarly journals The inner gaseous accretion disk around a Herbig Be star revealed by near- and mid-infrared spectro-interferometry

2007 ◽  
Vol 3 (S243) ◽  
pp. 337-344
Author(s):  
S. Kraus ◽  
Th. Preibisch ◽  
K. Ohnaka
Keyword(s):  
Accretion Disk ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Continuum Emission ◽  
Spectral Energy ◽  
Be Stars ◽  
Radial Temperature ◽  
Mid Infrared ◽  
Be Star ◽  
Dust Disks

AbstractHerbig Ae/Be stars are pre-main-sequence stars of intermediate mass, which are still accreting material from their environment, probably via a disk composed of gas and dust. Here we present a recent study of the geometry of the inner (AU-scale) circumstellar region around the Herbig Be star MWC 147 using long-baseline interferometry. By combining for the first time near- and mid-infrared spectro-interferometry on a Herbig star, our VLTI/AMBER and VLTI/MIDI data constrain not only the geometry of the brightness distribution, but also the radial temperature distribution in the disk. The emission from MWC 147 is clearly resolved and has a characteristic physical size of ∼1.3 AU and ∼9 AU at 2.2 μm and 11 μm respectively. This increase in apparent size towards longer wavelengths is much steeper than predicted by analytic disk models assuming power-law radial temperature distributions. For a detailed modeling of the interferometric data and the spectral energy distribution of MWC 147, we employ 2-D frequency-dependent radiation transfer simulations. This analysis shows that passive irradiated Keplerian dust disks can easily fit the SED, but predict much lower visibilities than observed, so these models can clearly be ruled out. Models of a Keplerian disk with emission from an optically thick inner gaseous accretion disk (inside the dust sublimation zone), however, yield a good fit of the SED and simultaneously reproduce the observed near- and mid-infrared visibilities. We conclude that the near-infrared continuum emission from MWC 147 is dominated by accretion luminosity emerging from an optically thick inner gaseous disk, while the mid-infrared emission also contains strong contributions from the passive irradiated dust disk.

scholarly journals Dust formation of Be stars with large infrared excess

2010 ◽  
Vol 6 (S272) ◽  
pp. 366-371
Author(s):  
Chien-De Lee ◽  
Wen-Ping Chen
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Thermal Emission ◽  
Far Infrared ◽  
Dust Particles ◽  
Be Stars ◽  
Ionized Gas ◽  
Infrared Excess ◽  
Star Forming ◽  
Infrared Wavelengths

AbstractClassical Be stars, in addition to their emission-line spectra, are associated with infrared excess which is attributable to free-free emission from ionized gas. However, a few with exceptionally large near-infrared excess, namely with J–H, and H–Ks both greater than 0.6 mag—and excess emission extending to mid- and far-infrared wavelengths—must be accounted for by thermal emission from circumstellar dust. Evolved Be stars on the verge of turning off the main sequence may condense dust in their expanding cooling envelopes. The dust particles should be very small in size, hence reprocess starlight efficiently. This is in contrast to Herbig Ae/Be stars for which the copious infrared excess arises from relatively large grains as part of the surplus star-forming materials.

scholarly journals Near Infrared Spectroscopic Observations of Early-type Be Stars

2000 ◽  
Vol 175 ◽  
pp. 468-471 ◽  
Author(s):  
N. M. Ashok ◽  
D. P. K. Banerjee
Keyword(s):  
Emission Line ◽  
Infrared Spectra ◽  
Near Infrared ◽  
Be Stars ◽  
Early Type ◽  
Line Flux ◽  
Near Infrared Spectra ◽  
Medium Resolution ◽  
Significant Strength ◽  
Lower Temperature

AbstractThe medium resolution (R=1000) near infrared spectra of 30 early type Be stars obtained during the period October 1998-April 1999 are presented. The Paschen β and Brackett γ lines are seen in emission in majority of these stars. The higher order Brackett series lines from m=10 to 19 are detected in emission with significant strength compared to the Brackett γ emission line flux indicating the effect of optical depth. The Fe II line at 1.6873μm is detected in a small number of stars indicating existence of higher density and lower temperature emission zone.

scholarly journals Optical Emission-Line Spectra of Be Stars (Review Paper)

1987 ◽  
Vol 92 ◽  
pp. 149-171 ◽  
Author(s):  
Joachim Dachs
Keyword(s):  
Emission Line ◽  
Near Infrared ◽  
Optical Emission ◽  
Rotating Disk ◽  
Circumstellar Envelope ◽  
Be Stars ◽  
Disk Model ◽  
Cycle Times ◽  
Star Models ◽  
Long Time

AbstractRecent observational work on spectra obtained at optical and near-infrared wavelengths is reviewed for “ordinary” (non-supergiant non-peculiar) Be and Be-shell stars, with particular emphasis on comparison between high-resolution spectral measurements and current Be star models. Emission-line profiles are interpreted in terms of geometry, dimensions and dynamics of a dense (N ≃ 1011 cm-3), cool (T ≃ 104 k) line-emitting region in the circumstellar envelope, separated from the thin, hot expanding stellar wind region. Present observations support a rotating-disk model for the cool, line-emitting region. Indications pointing towards structuring of cool circumstellar envelope regions are reported. Significant spectral variations are detected both on short (less than one day) and long time scales (months to years). Typical cycle times for large-amplitude V/R variations and intervals between shell episodes depend on spectral type, increasing with decreasing effective temperature of the central stars and ranging from a few years for early-Be type stars to a few decades for late Be stars.

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