Near infra-red and optical spectroscopy of Delta Scorpii

Banerjee, D. P. K.; Janardhan, P.; Ashok, N. M.

doi:10.1051/0004-6361:20011508

Cited by 13 publications

(13 citation statements)

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“…The calibrated visibility amplitude, differential phase and flux data are shown in and Brγ (2.1657µm) gaseous line emission. We note that He I and Brγ emission were also observed in K-band spectra made shortly after after the last periastron brightening (Banerjee et al 2001). (2) The visibilities at the wavelengths of these lines are lower than that at wavelengths of continuum-only emission (by ∼ 10%), indicating that the line emission region is larger than the continuum emission region (actually, by a large factor, as will be seen in the next section).…”

Section: Keck Interferometermentioning

confidence: 74%

SPECTRO-INTERFEROMETRY OF THE Be STAR δ Sco: NEAR-INFRARED CONTINUUM AND GAS EMISSION REGION SIZES IN 2007

Millan-Gabet

Monnier

Touhami

et al. 2010

ApJ

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We present near-infrared H and K-band spectro-interferometric observations of the gaseous disk around the primary Be star in the δ Sco binary system, obtained in 2007 (between periastron passages in 2000 and 2011). Observations using the CHARA/MIRC instrument at H-band resolve an elongated disk with a Gaussian FWHM 1.18 × 0.91 mas. Using the Keck Interferometer, the source of the K-band continuum emission is only marginally spatially resolved, and consequently we estimate a relatively uncertain K-band continuum disk FWHM of 0.7 ± 0.3 mas. Line emission on the other hand, He I λ2.0583 µm and Brγ λ2.1657 µm, is clearly detected, with ∼ 10% lower visibilities than those of the continuum. When taking into account the continuum/line flux ratio this translates into much larger sizes for the line emission regions: 2.2 ± 0.4 mas and 1.9 ± 0.3 mas for He I and Brγ respectively. Our KI data also reveal a relatively flat spectral differential phase response, ruling out significant off-center emission.We expect these new measurements will help constrain dynamical models being actively developed in order to explain the disk formation process in the δ Sco system and Be stars in general.a Consistent with the companion location relative to the FOV for each instrument, in the above flux ratios the H-band total flux (F T ) includes the secondary star, but the K-band total flux does not. b D = 14R .c Only needed to determine the continuum disk size, not the line sizes.

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Section: Keck Interferometermentioning

confidence: 74%

SPECTRO-INTERFEROMETRY OF THE Be STAR δ Sco: NEAR-INFRARED CONTINUUM AND GAS EMISSION REGION SIZES IN 2007

Millan-Gabet

Monnier

Touhami

et al. 2010

ApJ

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“…Indeed, free-free spectra improved significantly the quality of the fits. The temperature associated with the free-free spectra ranged between 7500 to 10 000 K. This corresponded to temperatures associated with regions that are ionized by hot central sources, such as HII regions, planetary nebulae and Be star disks in which the gas temperature is usually close to 10 000K (see Banerjee et al 2001). Similar quality fits are obtained when changing from a low-temperature source SED to a higher one if one increases the optical depth, such that the source temperature cannot be measured reliably; -No grain size distributions with values of q above 3 were able to provide good fits to the SEDs 5 .…”

Section: Simulating a Single Shellmentioning

confidence: 92%

VLTI monitoring of the dust formation event of the Nova V1280 Scorpii

Chesneau¹,

Banerjee

Millour

et al. 2008

A&A

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Context. We present the first high spatial-resolution monitoring of the dust-forming nova V1280 Sco, performed with the Very Large Telescope Interferometer (VLTI). Aims. These observations promise to improve the distance determination of such events and constrain the mechanisms leading to very efficient dust formation under the harsh physical conditions encountered in novae ejecta. Methods. Spectra and visibilities were regularly acquired between the onset of dust formation, 23 days after discovery (or 11 days after maximum), and day 145, using the beam-combiner instruments AMBER (near-IR) and MIDI (mid-IR). These interferometric observations were complemented by near-infrared data from the 1.2 m Mt. Abu Infrared Observatory, India. The observations are initially interpreted in terms of simple uniform models; however more complex models, probably involving a second shell, are required to explain data acquired following t = 110 d after outburst. This behavior is in accordance with the light curve of V1280 Sco, which exhibits a secondary peak at about t = 106 d, followed by a new, steep decline, suggesting a new dust-forming event. Spherical dust shell models generated with the DUSTY code are used to investigate the parameters of the main dust shell. Results. Using uniform disk models, these observations allow us to determine an apparent linear expansion rate for the dust shell of 0.35 ± 0.03 mas day −1 and the approximate ejection time of the matter in which dust formed of t ejec = 10.5 ± 7 d, i.e. close to the maximum brightness. This information, combined with the expansion velocity of 500 ± 100 km s −1 , implies a distance estimate of 1.6 ± 0.4 kpc. The sparse uv coverage does not enable deviations from spherical symmetry to be clearly discerned. The dust envelope parameters were determined. The dust mass generated was typically 2-8 × 10 −9 M day −1 , with a probable peak in production at about 20 days after the detection of dust and another peak shortly after t = 110 d, when the amount of dust in the shell was estimated as 2.2 × 10 −7 M . Considering that the dust-forming event lasted at least 200-250 d, the mass of the ejected material is likely to have exceeded 10 −4 M . The conditions for the formation of multiple shells of dust are also discussed.

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“…In the above, λ is the wavelength of emission in μm, z is the charge, g is the Gaunt factor, T s is the disc temperature, n e and n i are the electron and ion densities respectively, and c 2 = 1.438 cm K (Banerjee, Janardhan & Ashok 2001). In the case of a circumstellar disc, the volume of the emission region ( v ) is reasonably estimated as , where R s and H s are the disc radius and thickness, respectively.…”

Section: Resultsmentioning

confidence: 99%

Infrared studies of the Be star X Per

Mathew

Banerjee

Naik

et al. 2012

Monthly Notices of the Royal Astronomical Society

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Photometric and spectroscopic results are presented for the Be star X Per/HD 24534 from nearinfrared (near-IR) monitoring in 2010-2011. The star is one of a sample of selected Be/X-ray binaries being monitored by us in the near-IR to study correlations between their X-ray and near-IR behaviour. Comparison of the star's present near-IR magnitudes with earlier records shows the star to be currently in a prominently bright state with mean J, H, K magnitudes of 5.49, 5.33 and 5.06, respectively. The JHK spectra are dominated by emission lines of He I and Paschen and Brackett lines of H I. Lines of O I 1.1287 and 1.3165 μm are also present and their relative strength indicates, since O I 1.1287 is the stronger among the two lines, that Lyman β fluorescence plays an important role in their excitation. Recombination analysis of the H I lines is done, which shows that the Paschen and Brackett line strengths deviate considerably from case B predictions. These deviations are attributed to the lines being optically thick, and this supposition is verified by calculating the line centre optical depths predicted by recombination theory. Similar calculations indicate that the Pfund and Humphrey series lines should also be expected to be optically thick, which is found to be consistent with observations reported in other studies. The spectral energy distribution of the star is constructed and shown to have an IR excess. Based on the magnitude of the IR excess, which is modelled using a free-free contribution from the disc, the electron density in the disc is estimated and shown to be within the range of values expected in Be star discs.

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Near infra-red and optical spectroscopy of Delta Scorpii

Cited by 13 publications

References 14 publications

SPECTRO-INTERFEROMETRY OF THE Be STAR δ Sco: NEAR-INFRARED CONTINUUM AND GAS EMISSION REGION SIZES IN 2007

SPECTRO-INTERFEROMETRY OF THE Be STAR δ Sco: NEAR-INFRARED CONTINUUM AND GAS EMISSION REGION SIZES IN 2007

VLTI monitoring of the dust formation event of the Nova V1280 Scorpii

Infrared studies of the Be star X Per

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