The Use of Infrared Spectra for the Determination of Absolute Magnitudes.

Keenan, Philip C.; Hynek, J. A.

doi:10.1086/144717

Cited by 27 publications

(29 citation statements)

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“…The classification of red luminous stars in the far red region was discussed by Keenan & Hynek (1945), Sharpless (1956) and Solf (1978) for photographic spectrograms. More recently, Paper I explored several criteria presented in works discussing digital spectra (e.g., Ginestet et al 1994;Carquillat et al 1997;Díaz et al 1989;Zhou 1991).…”

Section: Spectral Classificationmentioning

confidence: 99%

“…The best calibrated indicators are the equivalent widths (EW) of the two strongest lines in the Ca ii triplet and the Ti i dominated blend at 8468 Å (Díaz et al 1989;Ginestet et al 1994;Paper I), which are useful in the G0-M4 and G5-M3 range, respectively. Other lines sensitive to luminosity are listed by Keenan & Hynek (1945). They include the Fe i 8327 Å line and the blend (mainly Fe i) at 8514 Å.…”

Section: Luminosity Calibrationmentioning

confidence: 99%

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Red supergiants around the obscured open cluster Stephenson 2

Negueruela

Marco

González-Fernández

et al. 2012

A&A

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Context. Several clusters of red supergiants have been discovered in a small region of the Milky Way close to the base of the ScutumCrux Arm and the tip of the Long Bar. Population synthesis models indicate that they must be very massive to harbour so many supergiants. Amongst these clusters, Stephenson 2, with a core grouping of 26 red supergiants, is a strong candidate to be the most massive young cluster in the Galaxy. Aims. Stephenson 2 is located close to a region where a strong over-density of red supergiants had been found. We explore the actual cluster size and its possible connection to this over-density. Methods. Taking advantage of Virtual Observatory tools, we have performed a cross-match between the DENIS, USNO-B1 and 2MASS catalogues to identify candidate obscured luminous red stars around Stephenson 2, and in a control nearby region. More than 600 infrared bright stars fulfill our colour criteria, with the vast majority having a counterpart in the I band and >400 being sufficiently bright in I to allow observation with a 4-m class telescope. We observed a subsample of ∼250 stars, using the multi-object, wide-field, fibre spectrograph AF2 on the WHT telescope in La Palma, obtaining intermediate-resolution spectroscopy in the 7500-9000 Å range. We derived spectral types and luminosity classes for all these objects and measured their radial velocities. Results. Our targets turned out to be G and K supergiants, late (≥M4) M giants, and M-type bright giants (luminosity class II) and supergiants. We found ∼35 red supergiants with radial velocities similar to Stephenson 2 members, spread over the two areas surveyed. In addition, we found ∼40 red supergiants with radial velocities incompatible in principle with a physical association. Conclusions. Our results show that Stephenson 2 is not an isolated cluster, but part of a huge structure likely containing hundreds of red supergiants, with radial velocities compatible with the terminal velocity at this Galactic longitude (and a distance ∼6 kpc). In addition, we found evidence of several populations of massive stars at different distances along this line of sight.

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Section: Spectral Classificationmentioning

confidence: 99%

Section: Luminosity Calibrationmentioning

confidence: 99%

Red supergiants around the obscured open cluster Stephenson 2

Negueruela

Marco

González-Fernández

et al. 2012

A&A

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“…Comparison to UVES spectra showed close matches with both HR 7971 (K3 II/III) and HR 611, which has ben classified as M0.8 III from narrow-band TiO/CN photometry (Wing 1978). The infrared Ca ii triplet (8498, 8542, 8662 Å) and the Fe i calibration lines at 8327, 8468, 8514, and 8689 Å noted in Keenan & Hynek (1945) were used to determine log g of 1.5 in a temperature range of 3900-4000 K. Deficiencies in iron (see Table 12) and the α elements were of particular note ( Table 7.…”

Section: A1mentioning

confidence: 99%

Comparative modelling of the spectra of cool giants

Lebzelter¹,

Heiter²,

Abia³

et al. 2012

A&A

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Context. Our ability to extract information from the spectra of stars depends on reliable models of stellar atmospheres and appropriate techniques for spectral synthesis. Various model codes and strategies for the analysis of stellar spectra are available today. Aims. We aim to compare the results of deriving stellar parameters using different atmosphere models and different analysis strategies. The focus is set on high-resolution spectroscopy of cool giant stars. Methods. Spectra representing four cool giant stars were made available to various groups and individuals working in the area of spectral synthesis, asking them to derive stellar parameters from the data provided. The results were discussed at a workshop in Vienna in 2010. Most of the major codes currently used in the astronomical community for analyses of stellar spectra were included in this experiment.Results. We present the results from the different groups, as well as an additional experiment comparing the synthetic spectra produced by various codes for a given set of stellar parameters. Similarities and differences of the results are discussed. Conclusions.Several valid approaches to analyze a given spectrum of a star result in quite a wide range of solutions. The main causes for the differences in parameters derived by different groups seem to lie in the physical input data and in the details of the analysis method. This clearly shows how far from a definitive abundance analysis we still are.Key words. stars: atmospheres -stars: late-type -stars: abundances -stars: fundamental parameters Based on observations obtained at the Bernard Lyot Telescope (TBL, Pic du Midi, France) of the Midi-Pyrénées Observatory, which is operated by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France.Tables 6-11 are only available in electronic form at http://www.aanda.orgThe spectra of stars 1 to 4 used in the experiment presented here are only availalbe at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via

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“…It is well established that the strengths of these bands correlate tightly with spectral type (e.g. Keenan & Hynek 1945;Sharpless 1956;Ramsey 1981;Kenyon & Fernández-Castro 1987;Schild et al 1992). Kenyon & Fernández-Castro (1987) and Schulte-Ladbeck (1988) succesfully classified symbiotic spectra using these bands.…”

Section: Spectral Classificationmentioning

confidence: 99%

Spectral classification of the cool giants in symbiotic systems

Mürset

Schmid²

1999

Astron. Astrophys. Suppl. Ser.

188

192

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Abstract. We derive the spectral types of the cool giants in about 100 symbiotic systems. Our classification is mainly based on near IR spectra in order to avoid the contamination of the spectrum by the nebula and the hot component in the visual region. The accuracy of our spectral types is approximately one spectral subclass, similar to previous near IR classification work, and much better than visual spectral type estimates.Strong, intrinsic spectral type variations (> 2 spectral subtypes) are only seen in systems containing pulsating mira variables.We present a catalogue of spectral types for cool giants in symbiotic systems which also includes determinations taken from the literature. The catalogue gives spectral types for the cool giants in about 170 systems which is nearly the full set of confirmed symbiotics.Based on our classifications we discuss the distribution of spectral types of the cool giants in galactic symbiotic binaries. We find that the spectral types cluster strongly between M3 and M6, with a peak at M5. The distribution of systems with a mira variable component peaks even later, at spectral types M6 and M7. This is a strong bias towards late spectral types when compared to red giants in the solar neighbourhood. Also the frequency of mira variables is much larger among symbiotic giants. This predominance of very late M-giants in symbiotic systems seems to indicate that large mass loss is a key ingredient for triggering symbiotic activity on a white dwarf companion.Further we find for symbiotic systems a strong correlation between the spectral type of the cool giant and the orbital period. In particular we find a tight relation for the minimum orbital period for symbiotic systems with Based on observations obtained with the 1.52 m and 3.6 m telescopes of the European Southern Observatory (ESO), the 1.93 m telescope of the Observatoire de Haute-Provence (OHP), the 2.3 m telescope of the Australian National University (ANU) at Siding Spring, and the William Herschel Telescope (WHT) at La Palma. This research has made use of the AFOEV database, operated at CDS, France. red giants of a given spectral type. This limiting line in the spectral type -orbital period diagram seems to be equivalent with the relation R ≤ 1 /2, where R is the radius of the red giant and 1 the distance from the center of the giant to the inner Lagrangian point L 1 . This correlation possibly discloses that symbiotic stars are -with probably only one exception in our sample -well detached binary systems.

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The Use of Infrared Spectra for the Determination of Absolute Magnitudes.

Cited by 27 publications

References 0 publications

Red supergiants around the obscured open cluster Stephenson 2

Red supergiants around the obscured open cluster Stephenson 2

Comparative modelling of the spectra of cool giants

Spectral classification of the cool giants in symbiotic systems

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