The Protoplanetary Disks in the Nearby Massive Star-Forming Region Cygnus Ob2

Context. In the last decades, the early pre main sequence stellar rotational evolution picture has been constrained by studies targetting different regions at a variety of ages with respect to young star formation. Observational studies suggest a dependence of rotation with mass, and for some mass ranges a connection between rotation and the presence of a circumstellar disk. Not still fully explored, though, is the role of environmental conditions on the rotational regulation.Aims. We investigate the rotational properties of candidate members of the young massive association Cygnus OB2. By evaluating their rotational properties, we address questions regarding the effect of environment properties on PMS rotational evolution.Methods. We studied JHK-band variability in 5083 candidate members (24% of them are diskbearing stars). The selection of variable stars was done using Stetson variability index, and period search was performed using Lomb-Scargle periodogram for periods between 0.83-45 days. Period detections were verified by using False Alarme Probability levels, the Saunders statistics, string/rope length method, and visual verification of folded light curves.Results. We identified 1224 periodic variable stars (24% of the candidate member sample, 8% of the disk-bearing sample, and 28% of the non-disked sample). Monte Carlo simulations were performed in order to evaluate completeness and contamination of the periodic sample, out of which 894 measured periods were considered reliable. Our study was considered reasonably complete for periods between 2 and 30 days. Conclusions. The general scenario for the rotational evolution of young stars seen in other regions is confirmed by Cygnus OB2 period distributions, with disked stars rotating on average slower than non-disked stars. A mass-rotation dependence was also verified, but as in NGC 6530, very low mass stars (M ≤ 0.4M ) are rotating on average slower than higher mass stars (0.4 M < M ≤ 1.4M ). We observed an excess of slow rotators among the lower mass population. The disk and mass-rotation connection was also analysed by taking into account the incident UV radiation arising from O stars in the association. Results compatible with the disk-locking scenario were verified for stars with low UV incidence, but no statistical significant relation between rotation and disk presence was verified for stars with high UV incidence suggesting that massive stars can have an important role on regulating the rotation of nearby low mass stars.Key words. infrared: stars -stars: variables: T Tauri -stars: low-mass -stars: formation -stars: pre main sequence -stars: rotation Use \titlerunning to supply a shorter title and/or \authorrunning to supply a shorter list of authors.

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“…J, H, and K s filters, 43485 sources. According to Guarcello et al (2013), it was used because it has a higher limit of saturation than UKIDSS.…”

Section: Data From Literaturementioning

confidence: 99%

“…IRAC 3.6,4.5,5.8,8.0 µm, and MIPS 24 µm (149381 sources) bands with sources detected down to 0.5 M (Guarcello et al 2013). …”

Section: Data From Literaturementioning

confidence: 99%

Near-infrared time-series photometry in the field of Cygnus OB2 association

Roquette

Bouvier

Alencar

et al. 2017

A&A

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“…Of these sources, 6, 9, 13, 31, and 33 have been identified as binary systems. Guarcello et al (2013) present several colourcolour and colour-magnitude diagrams as part of their multiwavelength analysis to distinguish disc stars and classify YSOs. They present a [3.6]-[5.8] versus [4.5]-[8.0] diagram (see their Fig. 2) distinguishing discs, photosphere stars, and galaxies.…”

Section: Infrared Counterpartsmentioning

confidence: 99%

COBRaS: The e-MERLIN 21 cm Legacy survey of Cygnus OB2

Morford

Fenech

Prinja

et al. 2020

A&A

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Context. The role of massive stars is central to an understanding of galactic ecology. It is important to establish the details of how massive stars provide radiative, chemical, and mechanical feedback in galaxies. Central to these issues is an understanding of the evolution of massive stars, and the critical role of mass loss via strongly structured winds and stellar binarity. Ultimately, and acting collectively, massive stellar clusters shape the structure and energetics of galaxies. Aims. We aim to conduct high-resolution, deep field mapping at 21 cm of the core of the massive Cygnus OB2 association and to characterise the properties of the massive stars and colliding winds at this waveband. Methods. We used seven stations of the e-MERLIN radio facility, with its upgraded bandwidth and enhanced sensitivity to conduct a 21 cm census of Cygnus OB2. Based on 42 hours of observations, seven overlapping pointings were employed over multiple epochs during 2014 resulting in 1σ sensitivities down to ∼ 21 µJy and a resolution of ∼ 180 mas. Results. A total of 61 sources are detected at 21 cm over a ∼ 0.48 • × 0.48 • region centred on the heart of the Cyg OB2 association. Of these 61 sources, 33 are detected for the first time. We detect a number of previously identified sources including four massive stellar binary systems, two YSOs, and several known X-ray and radio sources. We also detect the LBV candidate (possible binary system) and blue hypergiant (BHG) star of Cyg OB2 #12. Conclusions. The 21 cm observations secured in the COBRaS Legacy project provide data to constrain conditions in the outer wind regions of massive stars; determine the non-thermal properties of massive interacting binaries; examine evidence for transient sources, including those associated with young stellar objects; and provide unidentified sources that merit follow-up observations. The 21 cm data are of lasting value and will serve in combination with other key surveys of Cyg OB2, including Chandra and Spitzer.

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“…We also selected 10 candidate stars with transition disks (all detected in X-rays) as those showing excesses only at 8.0 µm and 24 µm. The infrared excesses in each infrared band is calculated using the Q VIJA color indices similar to those defined in Guarcello et al (2009Guarcello et al ( , 2013. These color indices compare the V −I and J−A colors, with A being K or one of the Spitzer bands.…”

Section: Targets Selectionmentioning

confidence: 99%

“…Testi et al 2014), and environmental feedback (e.g. Guarcello et al 2016), with timescales which roughly range from few thousands to about 10 7 years (Haisch et al 2001;Hernández et al 2007;Mamajek 2009). …”

Section: Introductionmentioning

confidence: 99%

CSI 2264: Simultaneous optical and X-ray variability in pre-main sequence stars

Guarcello¹,

Flaccomio²,

Micela³

et al. 2017

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Context. Pre-main sequence stars are variable sources. The main mechanisms responsible for their variability are variable extinction, unsteady accretion, and rotational modulation of both hot and dark photospheric spots and X-ray active regions. In stars with disks, this variability is related to the morphology of the inner circumstellar region (≤ 0.1 AU) and that of the photosphere and corona, all impossible to be spatially resolved with present day techniques. This has been the main motivation for the Coordinated Synoptic Investigation of NGC 2264, a set of simultaneous observations of NGC 2264 with 15 different telescopes. Aims. In this paper, we focus on the stars with disks. We analyze the X-ray spectral properties extracted during optical bursts and dips in order to unveil the nature of these phenomena. Stars without disks are studied in a companion paper. Methods. We analyze simultaneous CoRoT and Chandra/ACIS-I observations to search for coherent optical and X-ray flux variability in stars with disks. Then, stars are analyzed in two different samples. In stars with variable extinction, we look for a simultaneous increase of optical extinction and X-ray absorption during the optical dips; in stars with accretion bursts, we search for soft X-ray emission and increasing X-ray absorption during the bursts. Results. We find evidence for coherent optical and X-ray flux variability among the stars with variable extinction. In 9/24 stars with optical dips, we observe a simultaneous increase of X-ray absorption and optical extinction. In seven dips, it is possible to calculate the N H /A V ratio in order to infer the composition of the obscuring material. In 5/20 stars with optical accretion bursts, we observe increasing soft X-ray emission during the bursts that we associate to the emission of accreting gas. It is not surprising that these properties are not observed in all the stars with dips and bursts, since favorable geometric configurations are required. Conclusions. The observed variable absorption during the dips is mainly due to dust-free material in accretion streams. In stars with accretion bursts, we observe on average a larger soft X-ray spectral component not observed in non accreting stars.

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The Protoplanetary Disks in the Nearby Massive Star-Forming Region Cygnus Ob2

Cited by 38 publications

References 93 publications

Near-infrared time-series photometry in the field of Cygnus OB2 association

Near-infrared time-series photometry in the field of Cygnus OB2 association

COBRaS: The e-MERLIN 21 cm Legacy survey of Cygnus OB2

CSI 2264: Simultaneous optical and X-ray variability in pre-main sequence stars

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