On the Mass Accretion Rate and Infrared Excess in Herbig Ae/Be Stars

Mathew, Blesson; Manoj, P.; Ujjwal, K.; Kartha, Sreeja S.; Viswanath, Gayathri; Narang, Mayank; Paul, K. T.

doi:10.3847/1538-3881/ab0ca1

Cited by 61 publications

(56 citation statements)

References 63 publications

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“…4 When drafting this manuscript, a paper by Arun et al (2019) was published reporting on the accretion rates using Gaia data of a somewhat smaller sample than here. Notable differences are that we use homogeneously determined stellar parameters for a large fraction of the sample and the fact that their sample is not selected for parallax quality and therefore includes faulty Gaia parallax measurements affecting the derived distances.…”

Section: Discussionmentioning

confidence: 99%

The accretion rates and mechanisms of Herbig Ae/Be stars

Wichittanakom

Oudmaijer

Fairlamb

et al. 2020

Monthly Notices of the Royal Astronomical Society

126

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This work presents a spectroscopic study of 163 Herbig Ae/Be stars. Amongst these, we present new data for 30 objects. Stellar parameters such as temperature, reddening, mass, luminosity and age are homogeneously determined. Mass accretion rates are determined from Hα emission line measurements. Our data is complemented with the X-Shooter sample from previous studies and we update results using Gaia DR2 parallaxes giving a total of 78 objects with homogeneously determined stellar parameters and mass accretion rates. In addition, mass accretion rates of an additional 85 HAeBes are determined. We confirm previous findings that the mass accretion rate increases as a function of stellar mass, and the existence of a different slope for lower and higher mass stars respectively. The mass where the slope changes is determined to be 3.98 +1.37 −0.94 M . We discuss this break in the context of different modes of disk accretion for low-and high mass stars. Because of their similarities with T Tauri stars, we identify the accretion mechanism for the late-type Herbig stars with the Magnetospheric Accretion. The possibilities for the earlier-type stars are still open, we suggest the Boundary Layer accretion model may be a viable alternative. Finally, we investigated the mass accretion -age relationship. Even using the superior Gaia based data, it proved hard to select a large enough sub-sample to remove the mass dependency in this relationship. Yet, it would appear that the mass accretion does decline with age as expected from basic theoretical considerations.

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Section: Discussionmentioning

confidence: 99%

The accretion rates and mechanisms of Herbig Ae/Be stars

Wichittanakom

Oudmaijer

Fairlamb

et al. 2020

Monthly Notices of the Royal Astronomical Society

126

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“…In addition, there is observational evidence that points towards differences between the discs of low-and highmass PMS sources. This can be seen in the amount of infrared excess, which is much lower for high-mass sources (Ribas et al 2015;Vioque et al 2018;Arun et al 2019) or in morphology; for instance, spirals have only been found in early spectral type stars (Garufi et al 2018). Similarly, there is a clear observational bias in these results, as so far mostly long-lived, massive discs around low-mass stars have been observed.…”

Section: Introductionmentioning

confidence: 99%

Catalogue of new Herbig Ae/Be and classical Be stars

Vioque

Oudmaijer

Schreiner³

et al. 2020

A&A

115

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Context. The intermediate-mass pre-main sequence Herbig Ae/Be stars are key to understanding the differences in formation mechanisms between low- and high-mass stars. The study of the general properties of these objects is hampered by the lack of a well-defined, homogeneous sample, and because few and mostly serendipitously discovered sources are known. Aims. Our goal is to identify new Herbig Ae/Be candidates to create a homogeneous and well defined catalogue of these objects. Methods. We have applied machine learning techniques to 4 150 983 sources with data from Gaia DR2, 2MASS, WISE, and IPHAS or VPHAS+. Several observables were chosen to identify new Herbig Ae/Be candidates based on our current knowledge of this class, which is characterised by infrared excesses, photometric variabilities, and Hα emission lines. Classical techniques are not efficient for identifying new Herbig Ae/Be stars mainly because of their similarity with classical Be stars, with which they share many characteristics. By focusing on disentangling these two types of objects, our algorithm has also identified new classical Be stars. Results. We have obtained a large catalogue of 8470 new pre-main sequence candidates and another catalogue of 693 new classical Be candidates with a completeness of 78.8 ± 1.4% and 85.5 ± 1.2%, respectively. Of the catalogue of pre-main sequence candidates, at least 1361 sources are potentially new Herbig Ae/Be candidates according to their position in the Hertzsprung-Russell diagram. In this study we present the methodology used, evaluate the quality of the catalogues, and perform an analysis of their flaws and biases. For this assessment, we make use of observables that have not been accounted for by the algorithm and hence are selection-independent, such as coordinates and parallax based distances. The catalogue of new Herbig Ae/Be stars that we present here increases the number of known objects of the class by an order of magnitude.

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“…This uncertainty could in principle be reduced by averaging the results obtained from different emission lines [41]. The most recent L acc -L line empirical expressions for HAeBes including dozens of emission lines can be found in Fairlamb et al (2017) [64], and accretion rates inferred from this method (in particular, from the correlation with L Hα ) can also be found in the literature for hundreds of HAeBes [66,68].…”

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confidence: 99%

On the Mass Accretion Rates of Herbig Ae/Be Stars. Magnetospheric Accretion or Boundary Layer?

Mendigutía

2020

Galaxies

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Understanding how young stars gain their masses through disk-to-star accretion is of paramount importance in astrophysics. It affects our knowledge about the early stellar evolution, the disk lifetime and dissipation processes, the way the planets form on the smallest scales, or the connection to macroscopic parameters characterizing star-forming regions on the largest ones, among others. In turn, mass accretion rate estimates depend on the accretion paradigm assumed. For low-mass T Tauri stars with strong magnetic fields there is consensus that magnetospheric accretion (MA) is the driving mechanism, but the transfer of mass in massive young stellar objects with weak or negligible magnetic fields probably occurs directly from the disk to the star through a hot boundary layer (BL). The intermediate-mass Herbig Ae/Be (HAeBe) stars bridge the gap between both previous regimes and are still optically visible during the pre-main sequence phase, thus constituting a unique opportunity to test a possible change of accretion mode from MA to BL. This review deals with our estimates of accretion rates in HAeBes, critically discussing the different accretion paradigms. It shows that although mounting evidence supports that MA may extend to late-type HAes but not to early-type HBes, there is not yet a consensus on the validity of this scenario versus the BL one. Based on MA and BL shock modeling, it is argued that the ultraviolet regime could significantly contribute in the future to discriminating between these competing accretion scenarios.

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On the Mass Accretion Rate and Infrared Excess in Herbig Ae/Be Stars

Cited by 61 publications

References 63 publications

The accretion rates and mechanisms of Herbig Ae/Be stars

The accretion rates and mechanisms of Herbig Ae/Be stars

Catalogue of new Herbig Ae/Be and classical Be stars

On the Mass Accretion Rates of Herbig Ae/Be Stars. Magnetospheric Accretion or Boundary Layer?

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