YSOVAR: Mid-infrared Variability among YSOs in the Star Formation Region Serpens South

Wolk, S. J.; Günther, H. M.; Poppenhaeger, Katja; Winston, E.; Rebull, L. M.; Stauffer, J. R.; Gutermuth, Robert; Cody, Ann Marie; Hillenbrand, Lynne A.; Plavchan, Peter; Covey, Kevin R.; Song, Inseok

doi:10.3847/1538-3881/aaa6c4

Cited by 27 publications

(33 citation statements)

References 57 publications

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“…This results in large amplitude fluctuations of its total luminosity, a swelling of the stellar radius and a decrease of the flux released in the protostar's associated H II region. Under our assumptions, we calculate within the 10−th and 90−th percentile of the collection of bursts in our simulations of forming massive stars, the extend of their luminosity variations is ≈ 0.69, which is much larger than that observed for low-mass protostars (Wolk et al 2018). This constitutes a major difference between the high-and low-mass regimes of star formation, to be verified by means of future observations.…”

Section: Resultsmentioning

confidence: 74%

“…11b) gives ∆ [10,90] 1−mag = 0.69 mag. Particularly, one can compare the obtained burst variations with the value of 0.22 found for low-mass sources at 3.6 µm in the context of low-mass stellar objects in the Serpens South star formation region (Wolk et al 2018). According to our study, the average luminosity variation in massive star formation is larger than that in low-mass star formation, which constitutes a remarkable difference between these two regimes.…”

Section: The Scatter In Burst Magnitudes Is Wider In Massive Star Formentioning

confidence: 84%

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Parameter study for the burst mode of accretion in massive star formation

Meyer

Vorobyov

Elbakyan

et al. 2020

Monthly Notices of the Royal Astronomical Society

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It is now a widely held view that, in their formation and early evolution, stars build up mass in bursts. The burst mode of star formation scenario proposes that the stars grow in mass via episodic accretion of fragments migrating from their gravitationally-unstable circumstellar discs and it naturally explains the existence of observed pre-main-sequence bursts from high-mass protostars. We present a parameter study of hydrodynamical models of massive young stellar objects (MYSOs) that explores the initial masses of the collapsing clouds (Mc = 60–$200\, \rm M_{\odot }$) and ratio of rotational-to-gravitational energies (β = 0.005 − −0.33). An increase in Mc and/or β produces protostellar accretion discs that are more prone to develop gravitational instability and to experience bursts. We find that all MYSOs have bursts even if their pre-stellar core is such that β ≤ 0.01. Within our assumptions, the lack of stable discs is therefore a major difference between low- and high-mass star formation mechanisms. All our disc masses and disk-to-star mass ratios Md/M⋆ > 1 scale as a power-law with the stellar mass. Our results confirm that massive protostars accrete about 40-60% of their mass in the burst mode. The distribution of time periods between two consecutive bursts is bimodal: there is a short duration ($\sim 1-10~\rm yr$) peak corresponding to the short, faintest bursts and a long-duration peak (at $\sim 10^{3}-10^{4} \rm yr$) corresponding to the long, FU-Orionis-type bursts appearing in later disc evolution, i.e., around $30\, \rm kyr$ after disc formation. We discuss this bimodality in the context of the structure of massive protostellar jets as potential signatures of accretion burst history.

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Section: Resultsmentioning

confidence: 74%

Section: The Scatter In Burst Magnitudes Is Wider In Massive Star Formentioning

confidence: 84%

Parameter study for the burst mode of accretion in massive star formation

Meyer

Vorobyov

Elbakyan

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…There are three major differences between our class color and class SED YSO classification schemes. We include a separate flat spectrum class in order to match our SED based classification scheme with the Wolk et al (2018) YSOVar paper on Serpens South and our previous Serpens Main work (Winston et al 2007). We combine the class 0 and class 1s into class I due to the lack of far-IR or submm photometry to securely differentiate between them.…”

Section: X-ray Luminous Ysosmentioning

confidence: 99%

Chandra Detection of an Evolved Population of Young Stars in Serpens South

Winston

Wolk

Gutermuth

et al. 2018

Self Cite

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We present a Chandra study of the deeply embedded Serpens South starforming region, examining cluster structure and disk properties at the earliest stages. In total, 152 X-ray sources are detected. Combined with Spitzer and 2MASS photometry, 66 X-ray sources are reliably matched to an IR counterpart. We identify 21 class I, 6 flat spectrum, 16 class II, and 18 class III young stars; 5 were unclassified. Eighteen sources were variable in X-rays: 8 exhibiting flarelike emission, and one periodic source. The clusters X-ray luminosity distance was estimated: the best match was to the nearer distance of 260 pc for the front of the Aquila Rift complex. The N H vs. A K ratio is found to be ∼0.68x10 22 , similar to that measured in other young low mass regions, but lower than that measured in the ISM and high mass clusters (∼1.6-2x10 22 ). We find the spatial distribution closely follows that of the dense filament from which the stars have formed, with the class II population still strongly associated with the filament. There are four sub-clusters in the field, with three forming knots in the filament, and a fourth to the west, which may not be associated but may be contributing to the distributed class III population. A high percentage of diskless class IIIs ( upper limit 30% of classified X-ray sources) in such a young cluster could indicate that processing of disks is influenced by the cluster environment and is not solely time-scale dependent. the diskless class III stars (which do not exhibit excess emission in the IR) from field stars in combination with the IR photometry.In this paper we first discuss, in Sect. 2, the Chandra and Spitzer observations and the data reduction process. In Sect. 3 we will discuss the identification and evolutionary classification of the YSOs. A discusssion of the X-ray properties of the identified members, their spatial distribution, and the X-ray luminosity distance determination is presented in Sect. 4. Finally, a brief summary is presented in Sect. 5. Observations andData Reduction 2.1. Chandra ACIS-I Data The Serpens South cluster was observed by Chandra with the ACIS instrument on 7th June 2010, in a single epoch with a 97.49 ks/pix exposure time as part of OBSID 11013. The ACIS-I field was centered on the J2000 coordinates: 18 h 30 m 03 s , -02 o 01 ′ 58 ′′ , with a 17'×17' field of view. The observation was taken with ACIS-I in F AINT mode, and T E exposure mode with no grating, and included two of the ACIS-S chips adjacent to the ACIS-I array.The primary and secondary data were downloaded from the Chandra X-ray Center's archive and reprocessed with the CIAO v4.8 reproc tool to ensure that the latest CALDB 4.7.2 corrections were applied (Fruscione et al. 2006). The CIAO task f luximage was used to create an exposure map to correct for the photon energy dependent effective collecting area and the presence of chip gaps. Exposure maps were created to accurately represent the effective area across the imaging array. 1 The effective area is applied by CIAO to all further processing. ...

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“…Exploring PMS variability in different regions of the electromagnetic spectrum provides insights into the physical processes at work in these systems. Optical and infrared (IR) variability studies as the Young Stellar Object (YSO) Variability Spitzer Space Telescope program (YSOVAR Morales-Calderón et al 2011;Rebull et al 2014;Wolk et al 2018) and the Coordinated Synoptic Investigation of NGC 2264 (e.g., Cody et al 2014;Guarcello et al 2017Guarcello et al , 2019 have shown that most of the variability of a YSO is related to physical phenomena happening in the disk or due to the star-disk interaction. In disk-bearing PMS stars, the stardisk interaction and the accretion process causes variability due to the rotational modulation of hot spots at the stellar surface, which are produced at the base of the accretion column (e.g., Full Tables 1−5 and the light-curves of the stars analyzed in this study are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.…”

Section: Introductionmentioning

confidence: 99%

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

Roquette

Alencar

Bouvier³

et al. 2020

A&A

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We present the results of a J, H, and K photometric variability survey of the central 0.78 square degrees of the young OB association Cygnus OB2. We used data observed with the Wide-Field CAMera at the United Kingdom Infrared Telescope in 2007 (spanning 217 days) to investigate the light curves of 5083 low mass candidate members in the association and explore the occurrence and main characteristics of their near-infrared variability. We identified 2529 stars (∼50% of the sample) with significant variability with time-scales ranging from days to months. We classified the variable stars into the following three groups according to their light curve morphology: periodic variability (1697 stars), occultation variability (124 stars), and other types of variability (726 stars). We verified that the disk-bearing stars in our sample are significantly more variable in the near-infrared than diskless stars, with a steep increase in the disk-fraction among stars with higher variability amplitude. We investigated the trajectories described by variable stars in the color-space and measured slopes for 335 stars describing linear trajectories. Based on the trajectories in the color-space, we inferred that the sample analyzed is composed of a mix of young stars presenting variability due to hot and cold spots, extinction by circumstellar material, and changes in the disk emission in the near-infrared. We contemplated using the use of near-infrared variability to identify disk-bearing stars and verified that 53.4% of the known disk-bearing stars in our sample could have been identified as such based solely on their variability. We present 18 newly identified disk-bearing stars and 14 eclipsing binary candidates among CygOB2 lower-mass members.

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YSOVAR: Mid-infrared Variability among YSOs in the Star Formation Region Serpens South

Cited by 27 publications

References 57 publications

Parameter study for the burst mode of accretion in massive star formation

Parameter study for the burst mode of accretion in massive star formation

Chandra Detection of an Evolved Population of Young Stars in Serpens South

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

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