The 2018 eruption and long term evolution of the new high-mass Herbig Ae/Be object Gaia-18azl = VES 263

Munari, U.; Joshi,; Banerjee, D. P. K.; Čotar, Klemen; Shugarov, S. Yu.; Jurdana-Šepić, Rajka; Belligoli, R.; Bergamini, A; Graziani, M.; Righetti, G. L.; Vagnozzi, A.; Valisa, P.

doi:10.1093/mnras/stz2078

Cited by 7 publications

(20 citation statements)

References 54 publications

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“…Most of the literature A V values presented in Table 3 are estimated using this method, which can be unreliable for -in particular -highly variable objects. Besides the photometric variability, outbursting sources are known to change their spectral type during an outburst (e.g., Hillenbrand et al 2018Hillenbrand et al , 2019bMunari et al 2019), varying sometimes from typical KM spec- tra during quiescence to FG during outburst. Furthermore, in some cases (FU Ori, PTF 14jg and Gaia 17bpi, Herbig et al 2003;Hillenbrand et al 2018Hillenbrand et al , 2019b estimates of the spectral type can vary with wavelength, from F or G in the bluer regions of the spectra to K and even M in the redder regions.…”

Section: Comparison Of Dibs Extinction Results To Previous Extinction...mentioning

confidence: 99%

Measuring Optical Extinction Towards Young Stellar Objects Using Diffuse Interstellar Bands

Carvalho¹,

Hillenbrand²

2022

Preprint

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Line-of-sight extinction estimates to well-studied young T Tauri and Herbig Ae/Be stars are based on many different measurements and analysis methods. This has resulted in wide scatter among the published A V values for the same star. In this work, we discuss the challenges in measuring extinction to actively accreting and especially outbursting young stellar objects (YSOs), and explore a method not previously applied to young stars, utilizing diffuse interstellar bands (DIBs). In early-type stars, narrow correlations exist between DIB equivalent widths and the column density of interstellar material, and therefore the line-of-sight extinction.Here, we measure equivalent widths of the 5780 Å and 6614 Å DIB features in a sample of actively accreting YSOs, and apply established DIB-reddening calibrations to derive reddening, and subsequently extinction. We also compare the DIBs-inferred optical line-of-sight extinction values with previous extinction estimates for our sample stars.

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Section: Comparison Of Dibs Extinction Results To Previous Extinction...mentioning

confidence: 99%

Measuring Optical Extinction Towards Young Stellar Objects Using Diffuse Interstellar Bands

Carvalho¹,

Hillenbrand²

2022

Preprint

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“…The lightcurves of both objects are obtained from data extending over at least 10 consecutive orbital cycles. Adapted from Munari et al (2019). its Roche lobe, causing an ellipsoidal deformation of the surface, that along an orbital period presents to observers twice the larger projected area (the two maxima in the lightcurve) and twice the smaller one (the two minima).…”

Section: Orbital-like Periodicitiesmentioning

confidence: 99%

“…The RG+WD symbiotic stars are broadly divided into two major groups (see the recent review by Munari et al 2019 for details): those accreting-only (acc-SySt) whose optical spectra are dominated by the RG with no or weak emission lines, and the burning-type (burn-SySt) displaying a strong nebular continuum and a rich emission line spectrum: they originate from the wind of the RG, which is largely ionized by the very hot and luminous WD undergoing surface nuclear burning of accreted material.…”

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confidence: 99%

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The GALAH Survey and Symbiotic Stars. I. Discovery and follow-up of 33 candidate accreting-only systems

Munari,

Traven,

Masetti

et al. 2021

Preprint

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We have identified a first group of 33 new candidates for symbiotic stars (SySt) of the accretingonly variety among the 600 255 stars so far observed by the GALAH high-resolution spectroscopic survey of the Southern Hemisphere, more than doubling the number of those previously known. GALAH aims to high latitudes and this offers the possibility to sound the Galaxy for new SySt away from the usual Plane and Bulge hunting regions. In this paper we focus on SySt of the M spectral type, showing an H emission with a peak in excess of 0.5 above the adjacent continuum level, and not affected by coherent radial pulsations. These constraints will be relaxed in future studies. The 33 new candidate SySt were subjected to a vast array of follow-up confirmatory observations (X-ray/UV observations with the Swift satellite, search for optical flickering, presence of a near-UV upturn in ground-based photometric and spectroscopic data, radial velocity changes suggestive of orbital motion, variability of the emission line profiles). According to Gaia DR3 parallaxes, the new SySt are located at the tip of the Giant Branch, sharing the same distribution in M(K ) of the well established SySt. The accretion luminosities of the new SySt are in the range 1−10 L ⊙ , corresponding to mass-accretion rates of 0.1-1 10 −9 M ⊙ yr −1 for WDs of 1 M ⊙ . The M giant of one of the new SySt presents a large Lithium over-abundance.

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“…Because of possible overlaps between different stellar types, detailed photometric (especially in the infrared region where warm circumstellar dust disc can be identified) and spectroscopic observations are needed for an accurate physical explanation of the observed features. An examples of such work is presented in Munari et al (2019), who performed detailed a multi-band photometric study of an emission-line star, originally discovered on objective prism plates. The detailed photometric time-series study described in that work, together with observations of the star's infrared excess, led to the star VES 263 being identified as a massive pre-mainsequence star and not a semi-regular AGB cool giant as classified previously.…”

Section: Introductionmentioning

confidence: 99%

The GALAH survey: Characterization of emission-line stars with spectral modelling using autoencoders

Čotar,

Zwitter,

Traven

et al. 2020

Preprint

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We present a neural network autoencoder structure that is able to extract essential latent spectral features from observed spectra and then reconstruct a spectrum from those features. Because of the training with a set of unpeculiar spectra, the network is able to reproduce a spectrum of high signal-to-noise ratio that does not show any spectral peculiarities even if they are present in an observed spectrum. Spectra generated in this manner were used to identify various emission features among spectra acquired by multiple surveys using the HERMES spectrograph at the Anglo-Australian telescope. Emission features were identified by a direct comparison of the observed and generated spectra. Using the described comparison procedure, we discovered 10, 364 candidate spectra with a varying degree of Hα/Hβ emission component produced by different physical mechanisms. A fraction of those spectra belongs to the repeated observation that shows temporal variability in their emission profile. Among emission spectra, we find objects that feature contributions of a nearby rarefied gas (identified through the emission of [NII] and [SII] lines) that was identified in 4004 spectra, which were not all identified as having Hα emission. Positions of identified emission-line objects coincide with multiple known regions that harbour young stars. Similarly, detected nebular emission spectra coincide with visually-prominent nebular clouds observable in the red all-sky photographic composites.

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The 2018 eruption and long term evolution of the new high-mass Herbig Ae/Be object Gaia-18azl = VES 263

Cited by 7 publications

References 54 publications

Measuring Optical Extinction Towards Young Stellar Objects Using Diffuse Interstellar Bands

Measuring Optical Extinction Towards Young Stellar Objects Using Diffuse Interstellar Bands

The GALAH Survey and Symbiotic Stars. I. Discovery and follow-up of 33 candidate accreting-only systems

The GALAH survey: Characterization of emission-line stars with spectral modelling using autoencoders

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