Helium emission in the spectrum of K Canis Majoris

Bahng, J. D. R.; Hendry, E. M.

doi:10.1086/129735

Cited by 7 publications

(4 citation statements)

References 5 publications

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“…We may argue that Be stars vary strongly in time and thus line profiles shapes are time dependent. For instance actual Hα line profiles show a strong emission with a single peak whereas Bahng & Hendry (1975) saw a double-peaked Hα emission line, with the same double-peak separation of 160 km −1 we obtained for Paβ, with a shell core on their high-dispersion spectra. Nevertheless, these line variations are certainly related to the formation and disappearance of the circumstellar disk around the star as shown by Rivinius et al (2001) and Meilland et al (2006b).…”

Section: Is the Rotation Law Within The Disk Keplerian ?supporting

confidence: 81%

An asymmetry detected in the disk of κ Canis Majoris with AMBER/VLTI

Meilland

Millour

Stee

et al. 2006

A&A

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Aims. We study the geometry and kinematics of the circumstellar environment of the Be star κ CMa in the Brγ emission line and its nearby continuum. Methods. We use the AMBER/VLTI instrument operating in the K band, which provides a spatial resolution of about 6 mas with a spectral resolution of 1500, to study the kinematics within the disk and to infer its rotation law. To obtain more kinematical constraints we also use a high spectral resolution Paβ line profile obtain in December 2005 at the Observatorio do Pico do Dios, Brazil and we compile V/R line profile variations and spectral energy distribution data points from the literature. Results. Using differential visibilities and differential phases across the Brγ line we detect an asymmetry in the disk. Moreover, we found that κ CMa seems difficult to fit within the classical scenario for Be stars, illustrated recently by α Arae observations, i.e. a fast rotating B star close to its breakup velocity surrounded by a Keplerian circumstellar disk with an enhanced polar wind. We discuss the possibility that κ CMa is a critical rotator with a Keplerian rotating disk and examine whether if the detected asymmetry can be interpreted within the "one-armed" viscous disk framework.

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Section: Is the Rotation Law Within The Disk Keplerian ?supporting

confidence: 81%

An asymmetry detected in the disk of κ Canis Majoris with AMBER/VLTI

Meilland

Millour

Stee

et al. 2006

A&A

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“…Study of He emission lines is another less explored area in CBe star research. Bahng & Hendry (1975) found He lines 5876 and 6678 Å in emission in the spectra of the star 𝜅 CMa (B1.5 IVe) while lines in the blue region such as 4026 and 4471 Å were observed in absorption. They claimed He emission lines to be originating in the circumstellar envelope around 2 stellar radii from the central star.…”

Section: He Emission Linesmentioning

confidence: 92%

Optical spectroscopy of Galactic field classical Be stars

Banerjee

Mathew

Paul

et al. 2020

Monthly Notices of the Royal Astronomical Society

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In this study, we analyze the emission lines of different species present in 118 Galactic field classical Be stars in the wavelength range of 3800 - 9000 Å. We re-estimated the extinction parameter (AV) for our sample stars using the newly available data from Gaia DR2 and suggest that it is important to consider AV while measuring the Balmer decrement (i.e. D34 and D54) values in classical Be stars. Subsequently, we estimated the Balmer decrement values for 105 program stars and found that ≈ 20% of them show D34 ≥ 2.7, implying that their circumstellar disc are generally optically thick in nature. One program star, HD 60855 shows Hα in absorption- indicative of disc-less phase. From our analysis, we found that in classical Be stars, Hα emission equivalent width values are mostly lower than 40 Å, which agrees with that present in literature. Moreover, we noticed that a threshold value of ∼ 10 Å of Hα emission equivalent width is necessary for Fe ii emission to become visible. We also observed that emission line equivalent widths of Hα, P14, Fe ii 5169 and O i 8446 Å for our program stars tend to be more intense in earlier spectral types, peaking mostly near B1-B2. Furthermore, we explored various formation regions of Ca ii emission lines around the circumstellar disc of classical Be stars. We suggest the possibility that Ca ii triplet emission can originate either in the circumbinary disc or from the cooler outer regions of the disc, which might not be isothermal in nature.

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“…It is known that He I emission lines are found rarely in Be stars (Banerjee et al 2021) and are produced in hightemperature regions with T ∼15,000 K (Kwan & Fischer 2011). Bahng & Hendry (1975) proposed that these lines may either be a temporary phenomenon or non-LTE effects are responsible for their selective excitation. Since we find that He I lines are showing intensity changes over a short period of time, it may be a temporary phenomenon, as proposed by Bahng & Hendry (1975).…”

Section: Variability In He I Emission Linesmentioning

confidence: 99%

“…Bahng & Hendry (1975) proposed that these lines may either be a temporary phenomenon or non-LTE effects are responsible for their selective excitation. Since we find that He I lines are showing intensity changes over a short period of time, it may be a temporary phenomenon, as proposed by Bahng & Hendry (1975). Apparao & Tarafdar (1994) proposed that in Be stars, He I emission lines can be produced by the influence of a compact binary companion that is accreting matter from the disk of the primary (here the Be star) star.…”

Section: Variability In He I Emission Linesmentioning

confidence: 99%

Decoding the X-Ray Flare from MAXI J0709–159 Using Optical Spectroscopy and Multiepoch Photometry

Bhattacharyya¹,

Mathew²,

Ezhikode³

et al. 2022

ApJL

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We present a follow-up study on the recent detection of two X-ray flaring events by MAXI/Gas Slit Camera observations in soft and hard X-rays from MAXI J0709–159 in the direction of HD 54786 (LY CMa), on 2022 January 25. The X-ray luminosity during the flare was around 1037 erg s−1 (MAXI), which got reduced to 1032 erg s−1 (NuSTAR) after the flare. We took low-resolution spectra of HD 54786 from the 2.01 m Himalayan Chandra Telescope and the 2.34 m Vainu Bappu Telescope (VBT) facilities in India, on 2022 February 1 and 2. In addition to Hα emission, we found emission lines of He i in the optical spectrum of this star. By comparing our spectrum of the object with those from the literature we found that He i lines show variability. Using photometric studies we estimate that the star has an effective temperature of 20,000 K. Although HD 54786 is reported as a supergiant in previous studies, our analysis favors it to be evolving off the main sequence in the color–magnitude diagram. We could not detect any infrared excess, ruling out the possibility of IR emission from a dusty circumstellar disk. Our present study suggests that HD 54786 is a Be/X-ray binary system with a compact object companion, possibly a neutron star.

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Helium emission in the spectrum of K Canis Majoris

Cited by 7 publications

References 5 publications

An asymmetry detected in the disk of κ Canis Majoris with AMBER/VLTI

An asymmetry detected in the disk of κ Canis Majoris with AMBER/VLTI

Optical spectroscopy of Galactic field classical Be stars

Decoding the X-Ray Flare from MAXI J0709–159 Using Optical Spectroscopy and Multiepoch Photometry

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