scholarly journals Radio Stars of the SKA

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 119
Author(s):  
Bin Yu ◽  
Albert Zijlstra ◽  
Biwei Jiang
Keyword(s):  
Radio Emission ◽  
Milky Way ◽  
Galactic Plane ◽  
High Sensitivity ◽  
Hii Regions ◽  
Be Stars ◽  
M Dwarfs ◽  
Ob Stars ◽  
5 Ghz ◽  
Radio Stars

Radio emission from stars can be used, for example, to study ionized winds or stellar flares. The radio emission is faint and studies have been limited to few objects. The Square Kilometer Array (SKA) brings a survey ability to the topic of radio stars. In this paper we investigate what the SKA can detect, and what sensitivity will be required for deep surveys of the stellar Milky Way. We focus on the radio emission from OB stars, Be stars, flares from M dwarfs, and Ultra Compact HII regions. The stellar distribution in the Milky Way is simulated using the Besançon model, and various relations are used to predict their radio flux. We find that the full SKA will easily detect all UltraCompact HII regions. At the limit of 10 nJy at 5 GHz, the SKA can detect 1500 Be stars and 50 OB stars per square degree, out to several kpc. It can also detect flares from 4500 M dwarfs per square degree. At 100 nJy, the numbers become about 8 times smaller. SKA surveys of the Galactic plane should be designed for high sensitivity. Deep imaging should consider the significant number of faint flares in the field, even outside the plane of the Milky Way.

scholarly journals A circular polarization survey for radio stars with the Australian SKA Pathfinder

2021 ◽  
Vol 502 (4) ◽  
pp. 5438-5454
Author(s):  
Joshua Pritchard ◽  
Tara Murphy ◽  
Andrew Zic ◽  
Christene Lynch ◽  
George Heald ◽  
...  
Keyword(s):  
Radio Emission ◽  
Brightness Temperature ◽  
Circular Polarization ◽  
Flux Density ◽  
Wide Band ◽  
M Dwarfs ◽  
Square Kilometre Array ◽  
Population Statistics ◽  
Chemically Peculiar ◽  
Radio Stars

ABSTRACT We present results from a circular polarization survey for radio stars in the Rapid ASKAP Continuum Survey (RACS). RACS is a survey of the entire sky south of δ = +41○ being conducted with the Australian Square Kilometre Array Pathfinder telescope (ASKAP) over a 288 MHz wide band centred on 887.5 MHz. The data we analyse include Stokes I and V polarization products to an RMS sensitivity of 250 μJy PSF−1. We searched RACS for sources with fractional circular polarization above 6 per cent, and after excluding imaging artefacts, polarization leakage, and known pulsars we identified radio emission coincident with 33 known stars. These range from M-dwarfs through to magnetic, chemically peculiar A- and B-type stars. Some of these are well-known radio stars such as YZ CMi and CU Vir, but 23 have no previous radio detections. We report the flux density and derived brightness temperature of these detections and discuss the nature of the radio emission. We also discuss the implications of our results for the population statistics of radio stars in the context of future ASKAP and Square Kilometre Array surveys.

scholarly journals Ionization of the Galactic Center Arched Filaments

1989 ◽  
Vol 120 ◽  
pp. 132-133
Author(s):  
R. Rubin ◽  
M. Morris ◽  
E.F. Erickson ◽  
S. Colgan ◽  
J. Simpson
Keyword(s):  
Fine Structure ◽  
Radio Emission ◽  
Galactic Center ◽  
Galactic Plane ◽  
Line Emission ◽  
Far Infrared ◽  
Thin Filaments ◽  
Ob Stars ◽  
Structure Line ◽  
Photoionization Model

The remarkable filament system seen in radio observations in the vicinity of the galactic center includes two thin filaments which arch away from the galactic plane (E.G. Yusef-Zadem et al 1984). The brightest part of each of these thermal structures is located at GO.10+0.02 and GO.07+0.04. Morris and Yusef-Zadem (1989) reason that photoionization by OB stars is unlikely on geometrical and morphological grounds. They suggest a magnetohydrodynamic mechanism to account for the radio emission and ionization. Erickson et al. (1968) were able to explain most of their observations of the far infrared (FIR) fine structure line emission from these locations in terms of a photoionization model.

scholarly journals Radio Observations of Be Stars: (Review Paper)

1976 ◽  
Vol 70 ◽  
pp. 157-164 ◽  
Author(s):  
C. R. Purton
Keyword(s):  
Radio Emission ◽  
Radio Astronomy ◽  
Review Paper ◽  
Be Stars ◽  
Radio Observations ◽  
The Past ◽  
Be Star ◽  
Radio Stars

During the past few years the search for radio stars has been both intensive and extensive, and Be stars are among the various types of objects which have been examined. A large number of Be stars have not been detected, and to date no classical Be star has been found to emit detectable amounts of radio emission. However, following the tradition of radio astronomy to emphasise the abnormal or extreme cases, radio emission has been observed which is associated with a few peculiar Be stars.

scholarly journals Radio continuum emission in the northern Galactic plane: Sources and spectral indices from the THOR survey

2018 ◽  
Vol 619 ◽  
pp. A124 ◽  
Author(s):  
Y. Wang ◽  
S. Bihr ◽  
M. Rugel ◽  
H. Beuther ◽  
K. G. Johnston ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Milky Way ◽  
Galactic Plane ◽  
High Redshift ◽  
High Sensitivity ◽  
Large Percentage ◽  
Radio Continuum ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Spectral Indices

Context Radio continuum surveys of the Galactic plane can find and characterize H II regions, supernova remnants (SNRs), planetary nebulae (PNe), and extragalactic sources. A number of surveys at high angular resolution (≤25″) at different wavelengths exist to study the interstellar medium (ISM), but no comparable high-resolution and high-sensitivity survey exists at long radio wavelengths around 21 cm. Aims. Our goal is to investigate the 21 cm radio continuum emission in the northern Galactic plane at < 25″ resolution. Methods We observed a large percentage of the Galactic plane in the first quadrant of the Milky Way (l = 14.0−67.4° and |b| ≤ 1.25°) with the Karl G. Jansky Very Large Array (VLA) in the C-configuration covering six continuum spectral windows (SPW). These data provide a detailed view on the compact as well as extended radio emission of our Galaxy and thousands of extragalactic background sources. Results We used the BLOBCAT software and extracted 10 916 sources. After removing spurious source detections caused by the side lobes of the synthesized beam, we classified 10 387 sources as reliable detections. We smoothed the images to a common resolution of 25″ and extracted the peak flux density of each source in each SPW to determine the spectral indices α (assuming I(ν) ∝ να). By cross-matching with catalogs of H II regions, SNRs, PNe, and pulsars, we found radio counterparts for 840 H II regions, 52 SNRs, 164 PNe, and 38 pulsars. We found 79 continuum sources that are associated with X-ray sources. We identified 699 ultra-steep spectral sources (α < −1.3) that could be high-redshift galaxies. About 9000 of the sources we extracted are not classified specifically, but based on their spatial and spectral distribution, a large percentage of these are likely to be extragalactic background sources. More than 7750 sources do not have counterparts in the SIMBAD database and more than 3760 sources do not have counterparts in the NED database. Conclusions Studying the long wavelengths centimeter continuum emission and the associated spectral indices allows us to characaterize a large percentage of Galactic and extragalactic radio sources in the area of the northern inner Milky Way. This database will be extremely useful for future studies of a diverse set of astrophysical objects.

scholarly journals THE SINO-GERMAN λ6 CM POLARIZATION SURVEY OF THE GALACTIC PLANE: A SUMMARY

2013 ◽  
Vol 23 ◽  
pp. 82-91 ◽  
Author(s):  
J. L. HAN ◽  
W. REICH ◽  
X. H. SUN ◽  
X. Y. GAO ◽  
L. XIAO ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Interstellar Medium ◽  
Radio Telescope ◽  
Supernova Remnants ◽  
Galactic Plane ◽  
High Sensitivity ◽  
Hii Regions ◽  
Galactic Latitude ◽  
Galactic Longitude ◽  
Individual Objects

We have finished the λ6 cm polarization survey of the Galactic plane using the Urumqi 25 m radio telescope. It covers 10° ≤ l ≤ 230° in Galactic longitude and |b| ≤ 5° in Galactic latitude. The new polarization maps not only reveal new properties of the diffuse magnetized interstellar medium, but also are very useful for studying individual objects such as HII regions, which may act as Faraday screens with strong regular magnetic fields inside, and supernova remnants for their polarization properties and spectra. The high sensitivity of the survey enables us to discover two new SNRs G178.2–4.2 and G25.3–2.1 and a number of HII regions.

scholarly journals Two New Planetary Nebulae and an AGN in the Galactic Plane

1999 ◽  
Vol 16 (2) ◽  
pp. 134-138 ◽  
Author(s):  
S. H. Beer ◽  
A. E. Vaughan
Keyword(s):  
Radio Emission ◽  
Planetary Nebula ◽  
Galactic Plane ◽  
Angular Size ◽  
Planetary Nebulae ◽  
Optical Spectra ◽  
Radio Flux ◽  
Low Resolution ◽  
5 Ghz

AbstractA search for planetary nebulae was carried out using candidates selected by their infrared colours and 5 GHz radio emission. One new planetary nebula was identified on the basis of its small angular size, strong [O iii] emission and infrared colours. Another object, known as the possible planetary nebula Wray 16–28, is similarly identified as a planetary nebula. An undiscovered AGN was also found, and is classed as a Seyfert 2 galaxy on the basis of its strong O iii emission, linewidths of ∼500 km s−1, and 5 GHz radio flux. Low-resolution optical spectra are presented and distance estimates discussed.

scholarly journals Radio emission from young stellar objects in the Rho Ophiuchi cloud

1987 ◽  
Vol 122 ◽  
pp. 61-62
Author(s):  
Ph. André ◽  
T. Montmerle ◽  
E.D. Feigelson ◽  
P. Stine
Keyword(s):  
Radio Emission ◽  
Radio Continuum ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
X Ray ◽  
Rho Ophiuchi ◽  
5 Ghz ◽  
Radio Stars ◽  
Shed Light

Following an Einstein X-ray survey of the rho Oph molecular cloud, uncovering several dozen young stellar objects (YSO) (Montmerle et al. 1983), an extensive radio continuum VLA(C) survey was conducted in 1983 to look for counterparts to these sources at 1.4 and 5 GHz (André et al. 1986) To shed light on emission mechanisms, we performed follow-up VLA(A/B) observations of identified radio stars in March 1985 at 1.4, 5 and 15 GHz.

scholarly journals Faint optical spiral tracers

1979 ◽  
Vol 84 ◽  
pp. 99-99
Author(s):  
Juan C. Muzzio
Keyword(s):  
Emission Line ◽  
Milky Way ◽  
Be Stars ◽  
Schmidt Telescope ◽  
Ob Stars ◽  
The Past ◽  
Hα Emission ◽  
Photographic Emulsions

The use of modern photographic emulsions and techniques allows for the discovery of optical spiral tracers much fainter than was possible in the past. Our searches for such faint objects deal with the Puppis, Vela, Crux, Circinus, Norma and Ara regions of the Milky Way using Kodak plates (baked in dry nitrogen) obtained with the Curtis Schmidt-telescope at Cerro Tololo Inter-American Observatory. We have discovered OB stars as faint as 15 mag on IIIa-J plates obtained with the thin prism, and Hα emission-line objects (many of which are Be stars) as faint as 16 mag on 127-04 plates obtained with the 4° prism.

scholarly journals An infrared survey of the Southern Milky Way

1964 ◽  
Vol 20 ◽  
pp. 160-167 ◽  
Author(s):  
B. E. Westerlund
Keyword(s):  
Spectral Region ◽  
Milky Way ◽  
Galactic Plane ◽  
Galactic Structure ◽  
The Sun ◽  
Ob Stars ◽  
Objective Prism ◽  
Blue Spectral Region ◽  
Infrared Survey

The determination by optical means of the galactic structure at great distances from the Sun is becoming more and more important. Most optical investigations, using ordinary techniques — objective-prism survey in the blue spectral region + UBV photometry — do not reach very far out owing to the heavy obscuration in most directions in the galactic plane. Only a few very luminous OB stars and some rare supergiants have been identified in some selected regions at distances exceeding 4 kpc.

scholarly journals Evolution and appearance of Be stars in SMC clusters

2009 ◽  
Vol 5 (S266) ◽  
pp. 470-473
Author(s):  
C. Martayan ◽  
D. Baade ◽  
Y. Frémat ◽  
J. Zorec
Keyword(s):  
Main Sequence ◽  
Milky Way ◽  
Open Cluster ◽  
Central Star ◽  
Open Clusters ◽  
Be Stars ◽  
Ob Stars ◽  
Be Star ◽  
The Impact ◽  
Key Parameter

AbstractStar clusters are privileged laboratories for studying the evolution of massive stars (OB stars). One particularly interesting question concerns the phases during which the classical Be stars occur, which—unlike HAe/Be stars—are not pre-main-sequence objects, nor supergiants. Rather, they are extremely rapidly rotating B-type stars with a circumstellar decretion disk formed by episodic ejections of matter from the central star. To study the impact of mass, metallicity, and age on the Be phase, we observed Small Magellanic Cloud (SMC) open clusters with two different techniques: (i) with the ESO–WFI in slitless mode, which allowed us to find the brighter Be and other emission-line stars in 84 SMC open clusters, and (ii) with the VLT–FLAMES multifiber spectrograph to determine accurately the evolutionary phases of Be stars in the Be-star-rich SMC open cluster NGC 330. Based on a comparison to the Milky Way, a model of Be stellar evolution, appearance as a function of metallicity and mass, and spectral type is developed, involving the fractional critical rotation rate as a key parameter.

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