What’s Behind the Elephant’s Trunk? Identifying Young Stellar Objects on the Outskirts of IC 1396*

Abstract Empirically, the estimated lifetime of a typical protoplanetary disk is <5–10 Myr. However, the disk lifetimes required to produce a variety of observed exoplanetary systems may exceed this timescale. Some hypothesize that this inconsistency is due to estimating disk fractions at the cores of clusters, where radiation fields external to a star–disk system can photoevaporate the disk. To test this, we have observed a field on the western outskirts of the IC 1396 star-forming region with XMM-Newton to identify new Class III YSO cluster members. Our X-ray sample is complete for YSOs down to 1.8 M ⊙. We use a subset of these X-ray sources that have near- and mid-infrared counterparts to determine the disk fraction for this field. We find that the fraction of X-ray-detected cluster members that host disks in the field we observe is 17 − 7 + 10 % (1σ), comparable with the 29 − 3 + 4 % found in an adjacent field centered on the cometary globule IC 1396A. We reevaluate YSO identifications in the IC 1396A field using Gaia parallaxes compared to previous color-cut-only identifications, finding that incorporating independent distance measurements provides key additional constraints. Given the existence of at least one massive star producing an external radiation field in the cluster core, the lack of a statistically significant difference in disk fraction in each observed field suggests that disk lifetimes remain consistent as a function of distance from the cluster core.

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A Systematic Study of X-Ray Flares from Low-Mass Young Stellar Objects in the $\rho$ Ophiuchi Star-Forming Region with Chandra

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/55.3.653 ◽

2003 ◽

Vol 55 (3) ◽

pp. 653-681 ◽

Cited By ~ 49

Author(s):

Kensuke Imanishi ◽

Hiroshi Nakajima ◽

Masahiro Tsujimoto ◽

Katsuji Koyama ◽

Yohko Tsuboi

Keyword(s):

Systematic Study ◽

Young Stellar Objects ◽

Stellar Objects ◽

X Ray ◽

Star Forming ◽

Low Mass ◽

Rho Ophiuchi

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VLA cm-wave survey of young stellar objects in the Oph A cluster: constraining extreme UV- and X-ray-driven disk photoevaporation

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935340 ◽

2019 ◽

Vol 631 ◽

pp. A58 ◽

Cited By ~ 1

Author(s):

A. Coutens ◽

H. B. Liu ◽

I. Jiménez-Serra ◽

T. L. Bourke ◽

J. Forbrich ◽

...

Keyword(s):

Dust Emission ◽

Class Ii ◽

Field Of View ◽

Young Stellar Objects ◽

Continuum Emission ◽

Class Iii ◽

Stellar Objects ◽

Very Large Array ◽

X Ray ◽

Extreme Uv

Observations of young stellar objects (YSOs) in centimeter bands can probe the continuum emission from growing dust grains, ionized winds, and magnetospheric activity that are intimately connected to the evolution of protoplanetary disks and the formation of planets. We carried out sensitive continuum observations toward the Ophiuchus A star-forming region, using the Karl G. Jansky Very Large Array (VLA) at 10 GHz over a field-of-view of 6′ and with a spatial resolution of θmaj ×θmin ~ 0.′′4 × 0.′′2. We achieved a 5 μJy beam−1 rms noise level at the center of our mosaic field of view. Among the 18 sources we detected, 16 were YSOs (three Class 0, five Class I, six Class II, and two Class III) and two were extragalactic candidates. We find that thermal dust emission generally contributed less than 30% of the emission at 10 GHz. The radio emission is dominated by other types of emission, such as gyro-synchrotron radiation from active magnetospheres, free–free emission from thermal jets, free–free emission from the outflowing photoevaporated disk material, and synchrotron emission from accelerated cosmic-rays in jet or protostellar surface shocks. These different types of emission could not be clearly disentangled. Our non-detections for Class II/III disks suggest that extreme UV-driven photoevaporation is insufficient to explain disk dispersal, assuming that the contribution of UV photoevaporating stellar winds to radio flux does not evolve over time. The sensitivity of our data cannot exclude photoevaporation due to the role of X-ray photons as an efficient mechanism for disk dispersal. Deeper surveys using the Square Kilometre Array (SKA) will have the capacity to provide significant constraints to disk photoevaporation.

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Warm ionized ISM in the bulge of Andromeda galaxy

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310009373 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 296-296

Author(s):

Marat Gilfanov ◽

Akos Bogdan

Keyword(s):

Galactic Disk ◽

Broad Band ◽

Young Stellar Objects ◽

Stellar Objects ◽

Spiral Arms ◽

X Ray ◽

Star Forming ◽

Star Forming Regions ◽

Broad Band Emission ◽

Band Emission

AbstractWe demonstrate that unresolved X-ray emission from the bulge of M31 is composed of at least three different components: (i) Broad-band emission from a large number of faint sources – mainly accreting white dwarfs and active binaries, associated with the old stellar population, similar to the Galactic Ridge X-ray emission of the Milky Way. (ii) Soft emission from ionized gas with temperature of about ~ 300 eV and mass of ~ 4 × 106 M⊙. The gas distribution is significantly elongated along the minor axis of the galaxy suggesting that it may be outflowing in the direction perpendicular to the galactic disk. The shadows cast on the gas by spiral arms and the 10-kpc star-forming ring confirm large off-plane extent of the gas. (iii) Hard unresolved emission from spiral arms, most likely associated with protostars and young stellar objects located in the star-forming regions.

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The IGRINS YSO Survey II: Veiling Spectra of Pre-main-sequence Stars in Taurus-Auriga

The Astrophysical Journal ◽

10.3847/1538-4357/ac1dae ◽

2021 ◽

Vol 922 (1) ◽

pp. 27

Author(s):

Benjamin Kidder ◽

Gregory Mace ◽

Ricardo López-Valdivia ◽

Kimberly Sokal ◽

Victoria E. Catlett ◽

...

Keyword(s):

Near Infrared ◽

Thermal Emission ◽

Young Stellar Objects ◽

Continuum Emission ◽

Class Iii ◽

Infrared Excess ◽

Stellar Objects ◽

Star Forming ◽

Infrared Spectrometer ◽

Low Mass

Abstract We present measurements of the H- and K-band veiling for 141 young stellar objects (YSOs) in the Taurus-Auriga star-forming region using high-resolution spectra from the Immersion Grating Near-Infrared Spectrometer. In addition to providing measurements of r H and r K , we produce low-resolution spectra of the excess emission across the H and K bands. We fit temperatures to the excess spectra of 46 members of our sample and measure near-infrared excess temperatures ranging from 1200–2200 K, with an average of 1575 ± 225 K. We compare the luminosity of the excess continuum emission in Class II and Class III YSOs and find that a number of Class III sources display a significant amount of excess flux in the near-infrared. We conclude that the mid-infrared SED slope, and therefore young stellar object classification, is a poor predictor of the amount of near-infrared veiling. If the veiling arises in thermal emission from dust, its presence implies a significant amount of remaining inner-disk (<1 au) material in these Class III sources. We also discuss the possibility that the veiling effects could result from massive photospheric spots, unresolved binary companions, or accretion emission. Six low-mass members of our sample contain a prominent feature in their H-band excess spectra that is consistent with veiling from cool photospheric spots.

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The results of the search and study of young stellar objects with H emission in the Byurakan Observatory

Communications of the Byurakan Astrophysical Observatory ◽

10.52526/25792776-2018.2.1-80 ◽

2018 ◽

Vol 2 (1) ◽

pp. 80-90

Author(s):

E. H. Nikoghosyan ◽

Keyword(s):

Statistical Analysis ◽

Young Stars ◽

Emission Lines ◽

Young Stellar Objects ◽

Optical Range ◽

Stellar Objects ◽

X Ray ◽

Star Forming ◽

Star Forming Regions

One of the main observational properties of young stellar objects in the optical range is the presence of emission lines, in particular H (6563 Å). Therefore, detection of H emission is the most common spectroscopic means for identification of young stars. The paper presents the results of searching and studying of young stellar objects in several star forming regions carried out on the 2.6 m telescope in Byurakan observatory. The quantitative relationships between objects with different stage of activity are considered. In addition, a statistical analysis of H activity and other manifestations of PMS activity (X-ray, IR excess), as well as an evolutionary age of the H emitters in several star-forming regions is provided.

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Hα emission-line stars in molecular clouds

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731578 ◽

2019 ◽

Vol 630 ◽

pp. A90 ◽

Cited By ~ 2

Author(s):

Bertil Pettersson ◽

Bo Reipurth

Keyword(s):

Molecular Clouds ◽

Young Stellar Objects ◽

Be Stars ◽

Stellar Objects ◽

Strong Concentration ◽

Ob Stars ◽

Star Forming ◽

Hα Emission ◽

Objective Prism ◽

Emission Stars

A deep objective-prism survey for Hα emission stars towards the Canis Major star-forming clouds was performed. A total of 398 Hα emitters were detected, 353 of which are new detections. There is a strong concentration of these Hα emitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are young stellar objects recently born in the clouds. An additional population of Hα emitters is scattered all across the region, and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the Hα emitters are detected by WISE, of which 75% was detected with usable photometry. When plotted in a WISE colour–colour diagram it appears that the majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all the detections. We searched the Gaia-DR2 catalogue and from 334 Hα emission stars with useful parallaxes, we selected a subset of 98 stars that have parallax errors of less than 20% and nominal distances in the interval 1050 to 1350 pc that surrounds a strong peak at 1185 pc in the distance distribution. Similarly, Gaia distances were obtained for 51 OB-stars located towards Canis Major and selected with the same parallax errors as the Hα stars. We find a median distance for the OB stars of 1182 pc, in excellent correspondence with the distance from the Hα stars. Two known runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.

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Variability of young stellar objects in the star-forming region Pelican Nebula

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935418 ◽

2019 ◽

Vol 627 ◽

pp. A135 ◽

Cited By ~ 3

Author(s):

A. Bhardwaj ◽

N. Panwar ◽

G. J. Herczeg ◽

W. P. Chen ◽

H. P. Singh

Keyword(s):

Main Sequence ◽

T Tauri Stars ◽

Young Stellar Objects ◽

Spectral Energy ◽

Physical Parameters ◽

Main Sequence Stars ◽

Stellar Objects ◽

Star Forming ◽

T Tauri ◽

Optical Wavelengths

Context. Pre-main-sequence variability characteristics can be used to probe the physical processes leading to the formation and initial evolution of both stars and planets. Aims. The photometric variability of pre-main-sequence stars is studied at optical wavelengths to explore star–disk interactions, accretion, spots, and other physical mechanisms associated with young stellar objects. Methods. We observed a field of 16′ × 16′ in the star-forming region Pelican Nebula (IC 5070) at BVRI wavelengths for 90 nights spread over one year in 2012−2013. More than 250 epochs in the VRI bands are used to identify and classify variables up to V ∼ 21 mag. Their physical association with the cluster IC 5070 is established based on the parallaxes and proper motions from the Gaia second data release (DR2). Multiwavelength photometric data are used to estimate physical parameters based on the isochrone fitting and spectral energy distributions. Results. We present a catalog of optical time-series photometry with periods, mean magnitudes, and classifications for 95 variable stars including 67 pre-main-sequence variables towards star-forming region IC 5070. The pre-main-sequence variables are further classified as candidate classical T Tauri and weak-line T Tauri stars based on their light curve variations and the locations on the color-color and color-magnitude diagrams using optical and infrared data together with Gaia DR2 astrometry. Classical T Tauri stars display variability amplitudes up to three times the maximum fluctuation in disk-free weak-line T Tauri stars, which show strong periodic variations. Short-term variability is missed in our photometry within single nights. Several classical T Tauri stars display long-lasting (≥10 days) single or multiple fading and brightening events of up to two magnitudes at optical wavelengths. The typical mass and age of the pre-main-sequence variables from the isochrone fitting and spectral energy distributions are estimated to be ≤1 M⊙ and ∼2 Myr, respectively. We do not find any correlation between the optical amplitudes or periods with the physical parameters (mass and age) of pre-main-sequence stars. Conclusions. The low-mass pre-main-sequence stars in the Pelican Nebula region display distinct variability and color trends and nearly 30% of the variables exhibit strong periodic signatures attributed to cold spot modulations. In the case of accretion bursts and extinction events, the average amplitudes are larger than one magnitude at optical wavelengths. These optical magnitude fluctuations are stable on a timescale of one year.

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X-ray properties of He ii λ 1640 emitting galaxies in VANDELS

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1805 ◽

2020 ◽

Vol 496 (3) ◽

pp. 3796-3807

Author(s):

A Saxena ◽

L Pentericci ◽

D Schaerer ◽

R Schneider ◽

R Amorin ◽

...

Keyword(s):

Formation Rate ◽

Galactic Nuclei ◽

X Ray ◽

Star Forming ◽

Set Constraints ◽

Significant Difference ◽

Low Metallicity ◽

Matched Samples ◽

X Ray Binaries

ABSTRACT We explore X-ray emission from a sample of 18 He ii λ1640 emitting star-forming galaxies at z ∼ 2.3–3.6 from the VANDELS survey in the Chandra Deep Field South, to set constraints on the role of X-ray sources in powering the He ii emission. We find that 4 He ii emitters have tentative detections with S/N ∼ 2 and have X-ray luminosities, LX = 1.5−4.9 × 1041 erg s−1. The stacked luminosity of all 18 He ii emitters is 2.6 × 1041 erg s−1, and that of a subset of 13 narrow He ii emitters (FHWM(He ii) < 1000 km s−1) is 3.1 × 1041 erg s−1. We also measure stacked LX for non-He ii emitters through bootstrapping of matched samples, and find LX = 2.5 × 1041 erg s−1, which is not significantly different from LX measured for He ii emitters. The LX per star formation rate for He ii emitters (log (LX/SFR) ∼ 40.0) and non-emitters (log (LX/SFR) ∼ 39.9) are also comparable and in line with the redshift evolution and metallicity dependence predicted by models. Due to the non-significant difference between the X-ray emission from galaxies with and without He ii, we conclude that X-ray binaries or weak or obscured active galactic nuclei are unlikely to be the dominant producers of He ii ionizing photons in VANDELS star-forming galaxies at z ∼ 3. Given the comparable physical properties of both He ii emitters and non-emitters reported previously, alternative He ii ionizing mechanisms such as localized low-metallicity stellar populations, Pop-III stars, etc. may need to be explored.

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