A search for Keplerian periods in the brightness variations of T Tauri and Ae Herbig stars

Artemenko, S. A.; Grankin, K. N.; Петров, П. П.

doi:10.1134/s1063772910020095

Cited by 20 publications

(26 citation statements)

References 38 publications

(38 reference statements)

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“…It is interesting to note the close agreement between the estimated photometric period P 2 (∼24.78 days) of Artemenko et al (2010) and the Keplerian period obtained with our NIR spectroscopy (P∼24.84 days). Period P 2 , to the best of our knowledge, does not seem to be a rotational modulation produced by spots in the stellar surface.…”

Section: Resultssupporting

confidence: 82%

“…Curiously, the v sin i found by iteratively fitting the models is also close to the estimates used in Artemenko's publication. It can be seen that the rotational period is clearly not of the order of the period P 2 of 24.78 days encountered in the studies of Artemenko et al (2010) and Percy et al (2010). The apparent disparity between the two periods may seem to reinforce the idea that P 2 is of companion origin and not rotationally driven, but a possible relation between P 1 and 4xP 2 cannot be completely ruled out and should be investigated further in the future with a larger data set.…”

Section: Observational Methods and Data Reductionmentioning

confidence: 79%

“…The orbit was predicted to have semimajor axis of ∼0.18 AU, which is close to the inner disk radius R in =0.14 AU, measured by IR-interferometry (Eisner et al 2005;Andrews et al 2009). Artemenko et al (2010) further interpret the light variations of P 2 as the effect of scattering or extinction in the disturbed disk near the dust sublimation radius.…”

Section: Introductionmentioning

confidence: 82%

“…The mass of AS 205A, as derived from its stellar temperature and bolometric luminosity (Andrews et al 2009), and using the recently released pre-evolutionary tracks from Baraffe et al (2015), is expected to be close to solar (∼ 0.9 M⊙). According to Artemenko et al (2010), the period P 2 should correspond to the Keplerian location of an unknown close companion of AS 205A which perturbed the accretion disk with density waves. The orbit was predicted to have semimajor axis of ∼0.18 AU, which is close to the inner disk radius R in =0.14 AU, measured by IR-interferometry (Eisner et al 2005;Andrews et al 2009).…”

Section: Introductionmentioning

confidence: 99%

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Evidence of a substellar companion around a very young T Tauri star

Almeida

Gameiro

Петров

et al. 2017

A&A

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We present results from a Near Infrared multi-epoch spectroscopic campaign to detect a young low-mass companion to a T Tauri star. AS 205A is a late-type dwarf (≈K5) of ∼ 1 M⊙ that belongs to a triple system. Independent photometric surveys discovered that AS 205A has two distinct periods (P 1 =6.78 and P 2 =24.78 days) detected in the light curve that persist over several years. Period P 1 seems to be linked to the axial-rotation of the star and is caused by the presence of cool surface spots. Period P 2 is correlated with the modulation in AS 205A brightness (V) and red color (V-R), consistent with a gravitating object within the accretion disk.We here derive precise Near Infrared radial velocities to investigate the origin of period P 2 which is predicted to correspond to a cool source in a Keplerian orbit with a semi-major axis of ∼0.17 AU positioned close to the inner disk radius of 0.14 AU. The radial velocity variations of AS 205A were found to have a period of P ≈ 24.84 days and a semi-amplitude of 1.529 kms −1 . This result closely resembles the P 2 period in past photometric observations (P ≈ 24.78 days). The analysis of the cross-correlation function bisector has shown no correlation with the radial velocity modulations, strongly suggesting that the period is not controlled by stellar rotation. Additional activity indicators should however be explored in future surveys. Taking this into account we found that the presence of a substellar companion is the explanation that best fits the results. We derived an orbital solution for AS 205A and found evidence of a m 2 sini ≃19.25 M Jup object in an orbit with moderate eccentricity of e ≃ 0.34. If confirmed with future observations, preferably using a multiwavelength survey approach, this companion could provide interesting constraints on brown dwarf and planetary formation models.

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Section: Resultssupporting

confidence: 82%

Section: Observational Methods and Data Reductionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Evidence of a substellar companion around a very young T Tauri star

Almeida

Gameiro

Петров

et al. 2017

A&A

Self Cite

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“…Lorenzetti et al 2009). However, since that time it has stayed at this bright level but with dramatic and fairly irregular light variations (Artemenko et al 2010). Tentative photometric periods proposed by Richter et al (1992), Bouvier et al (1993Bouvier et al ( , 1995 differ by several days, and are different from a more recent determination by Percy et al (2010), who assign a period of 5.0 days.…”

Section: Introductionmentioning

confidence: 86%

Accretion-powered chromospheres in classical T Tauri stars

Петров

Gahm

Stempels

et al. 2011

A&A

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Context. Optical spectra of classical T Tauri stars (cTTS) are rich in emission lines of low-excitation species that are composed of narrow and broad components, which indicates the existence of two emitting regions with different kinematics, densities, and temperatures. The photospheric spectrum is often veiled by an excess continuous emission. This veiling is usually attributed to radiation from a heated region beneath the accretion shock. The broad emission lines of H i, He ii, Ca ii, Fe ii, and other species are thought to form in a larger volume of gas. Aims. The aim of this research is to clarify the nature of the veiling, and whether the narrow chromospheric lines of Fe i and other metals represent a standard chromosphere of a late-type star, or are induced by mass accretion. Methods. We carried out high-resolution spectroscopy of selected cTTS with a special focus on DR Tauri and followed variations of chromospheric features, such as narrow Fe i emission lines, and accretion signatures such as the veiling continuum and the He ii line emission. Results. We found that the amount of veiling in DR Tau varies from practically nothing to factors more than 10 times the stellar continuum intensity, and that the veiling is caused by both a non-photospheric continuum and chromospheric line emission filling in the photospheric absorption lines. The latter causes differential veiling because stronger lines are more veiled. We developed methods to separate the two sources of veiling. Several veiled T Tauri stars show a common effect: the radial velocities of photospheric and chromospheric lines vary in anti-phase. This is caused by an area with enhanced chromospheric emission, which is offset from the pole of rotation and is associated with the hot spot formed at the footprint of the magnetic funnel of mass accretion. Conclusions. The enhanced chromospheric emission in cTTS is linked not only to solar-like magnetic activity, but is powered to a greater extent by the accreting gas. We suggest that the area of enhanced chromospheric emission is induced by mass accretion, which modifies the local structure of stellar atmosphere in an area that is more extended than the hot accretion spot. The narrow emission lines from this extended area are responsible for the extra component in the veiling through line-filling of photospheric absorption lines.

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Variable stars in the young open cluster NGC 2244

Michalska¹

2013

Proc. IAU

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We present results of a U BV I C variability survey in the young open cluster NGC 2244. In total, we found 245 variable stars. Most of them, 211 stars, are variables with irregular variations. Furthermore, 23 periodic variables were found. We also detected four candidates for δ Scuti stars and 7 eclipsing binaries.Based on the mid-infrared Spitzer and WISE photometry and near infrared JHK S 2MASS photometry we classified 104 young stellar sources among our variables: 1 Class I object, 1 Class I/flat spectrum object, 4 flat spectrum objects, 91 Class II objects and 7 transition disk objects. This classification, together with r i Hα IPHAS photometry and JHK UKIDSS photometry, were used for identification of pre-main sequence stars among irregular and periodic variables. In this way, 97 CTTS candidates (96 irregular and one periodic variable), 68 WTTS candidates (54 irregular and 14 periodic variables) and 6 Herbig Ae/Be stars were found.For 223 variable stars we calculated membership probability based on proper motions from Gaia DR2 catalogue. Majority of them, 143 stars, are cluster members with probability greater than 70 percent. For only 36 variable stars the membership probability is smaller than 20 percent.

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A search for Keplerian periods in the brightness variations of T Tauri and Ae Herbig stars

Cited by 20 publications

References 38 publications

Evidence of a substellar companion around a very young T Tauri star

Evidence of a substellar companion around a very young T Tauri star

Accretion-powered chromospheres in classical T Tauri stars

Variable stars in the young open cluster NGC 2244

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