Possibilities of Narrow-Band Photometry, Especially for Main-Sequence Problems

1971 ◽  
pp. 171-173
Author(s):  
Bengt Strömgren
Keyword(s):  
Main Sequence ◽  
Narrow Band

scholarly journals New Herbig–Haro objects and outflows in the Mon R1 association

2020 ◽  
Vol 500 (2) ◽  
pp. 2440-2450
Author(s):  
T A Movsessian ◽  
T Yu Magakian ◽  
S N Dodonov
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Narrow Band ◽  
Schmidt Telescope ◽  
Stellar Objects ◽  
Hh Objects ◽  
The Mean ◽  
Infrared Data

ABSTRACT We present the results of a narrow-band Hα and [S ii] imaging survey of the Mon R1 association performed with the 1-m Schmidt telescope at Byurakan Observatory. Our observations covered a 1° field near the centre of the association. As a result of this study, 20 new Herbig–Haro knots were discovered, some of which form collimated outflows. Among the most extended ones are HH 1203 and HH 1196, which have a length of 1 pc or even more. During the search for the probable sources of HH objects, several new nebulous stars were found. A list of all nebulous stellar objects in the Mon R1 area under study is presented, with detailed descriptions of the most interesting ones. The near-infrared data from the GLIMPSE360 and WISE surveys revealed several more objects related to Mon R1, some of which had optical counterparts, as well as helped to identify at least three probable H2 collimated flows from the deeply embedded pre-main-sequence objects. The probable members of Mon R1 were selected by their distances; their bolometric luminosities and extinctions were estimated. Among the outflow sources, three embedded objects with luminosities greater than 10 L⊙ were found. The mean distance to the Mon R1 complex is estimated as 715 pc.

scholarly journals Narrow-band Hα imaging of nearby Wolf–Rayet galaxies

2019 ◽  
Vol 490 (3) ◽  
pp. 3448-3453
Author(s):  
A Paswan ◽  
Kanak Saha ◽  
A Omar
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Narrow Band ◽  
Far Infrared ◽  
Infrared Excess ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Far Ultraviolet ◽  
First Time

ABSTRACT We present narrow-band Hα imaging of nearby Wolf–Rayet (WR) galaxies known as a subset of starburst galaxies. The Hα images have been used to show morphology of star-forming regions in galaxies, which leads to speculate that the studied galaxies have most likely experienced merger or interaction with low luminous dwarf galaxies or H i clouds. We further derive the Hα-based star formation rates (SFRs) in galaxies using our Hα observations. These SFRs are well correlated with SFRs derived using other indicators at far-ultraviolet, far-infrared, and 1.4-GHz radio wavebands. It is noticed that the infrared excess (IRX) method gives the best SFR estimates, consistent with different models predication. These models also predict that the sample galaxies have probably gone through a continuous star formation at least for 1 Gyr over which the recent (<10 Myr) star formation has taken place in WR phase. This study presents main-sequence (MS) relation for nearby WR galaxies for the first time. This derived MS relation is found to be similar to previously known MS relation for normal nearby star-forming galaxies, suggesting that WR systems evolve in a similar fashion as normal star-forming galaxies evolve.

General remarks on narrow-band photometry

1966 ◽  
Vol 24 ◽  
pp. 129-131 ◽  
Author(s):  
B. Strömgren
Keyword(s):  
Classification Accuracy ◽  
Small Area ◽  
Main Sequence ◽  
Narrow Band ◽  
High Accuracy ◽  
Two Dimensional ◽  
Dimensional Classification ◽  
Hydrogen Lines ◽  
Classification Procedures ◽  
High Degree

During the last decade, a number of procedures for stellar classification on the basis of indices determined through narrow-band photometry have been developed. It appears that satisfactory two-dimensional classification can be carried out in this way for most regions of the Hertzsprung-Russell diagram, and in some regions a relatively high degree of classification accuracy has been achieved. Certain areas of the Hertzsprung-Russell diagram present difficulties, such as a relatively small area on the main sequence around A1 where the hydrogen lines and the Balmer discontinuity reach their maximum. However, it is already clear that the difficulties can be resolved through the addition of further classification indices. Difficulties connected with the effects of interstellar reddening have been overcome; in fact, some of the classification procedures that have been developed lead to high-accuracy determinations of color excesses.

scholarly journals Supernovae and the Ap Phenomenon

1980 ◽  
Vol 85 ◽  
pp. 251-251
Author(s):  
R. Rajamohan ◽  
Ashok K. Pati
Keyword(s):  
Supernova Remnant ◽  
Main Sequence ◽  
Narrow Band ◽  
Present Evidence ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Galactic Clusters ◽  
Chemically Peculiar Stars

We present evidence that relates the phenomenon of the chemically peculiar stars of the upper main sequence to supernovae explosions in young galactic clusters and associations. In the Upper Scorpius region of the Scorpio-Centaurus association we find that the radio shell discovered by Sancisi and Van Woerden (1970) from 21 cm observations and interpreted by them as an old supernova remnant has interacted with dense clouds. This remnant is seen clearly in the deep sky, narrow-band, H-alpha pictures of Sivan (1974). We find that the peculiar stars lie close to, or along the edges of, the interaction.

Statistical analysis of classification

1966 ◽  
Vol 24 ◽  
pp. 188-189
Author(s):  
T. J. Deeming
Keyword(s):  
Multivariate Analysis ◽  
Statistical Analysis ◽  
Classification Scheme ◽  
Analytical Procedure ◽  
Narrow Band ◽  
Scientific Research ◽  
Maximum Amount ◽  
Amount Of Information

If we make a set of measurements, such as narrow-band or multicolour photo-electric measurements, which are designed to improve a scheme of classification, and in particular if they are designed to extend the number of dimensions of classification, i.e. the number of classification parameters, then some important problems of analytical procedure arise. First, it is important not to reproduce the errors of the classification scheme which we are trying to improve. Second, when trying to extend the number of dimensions of classification we have little or nothing with which to test the validity of the new parameters.Problems similar to these have occurred in other areas of scientific research (notably psychology and education) and the branch of Statistics called Multivariate Analysis has been developed to deal with them. The techniques of this subject are largely unknown to astronomers, but, if carefully applied, they should at the very least ensure that the astronomer gets the maximum amount of information out of his data and does not waste his time looking for information which is not there. More optimistically, these techniques are potentially capable of indicating the number of classification parameters necessary and giving specific formulas for computing them, as well as pinpointing those particular measurements which are most crucial for determining the classification parameters.

Photo-electric Hβ and uvby photometry

1966 ◽  
Vol 24 ◽  
pp. 170-180
Author(s):  
D. L. Crawford
Keyword(s):  
Narrow Band ◽  
Line Strength ◽  
Interference Filter ◽  
B Stars ◽  
Relative Line ◽  
The Mean ◽  
F Stars ◽  
Two Parameters ◽  
Filter Photometry ◽  
The Continuum

Early in the 1950's Strömgren (1, 2, 3, 4, 5) introduced medium to narrow-band interference filter photometry at the McDonald Observatory. He used six interference filters to obtain two parameters of astrophysical interest. These parameters he calledlandc, for line and continuum hydrogen absorption. The first measured empirically the absorption line strength of Hβby means of a filter of half width 35Å centered on Hβand compared to the mean of two filters situated in the continuum near Hβ. The second index measured empirically the Balmer discontinuity by means of a filter situated below the Balmer discontinuity and two above it. He showed that these two indices could accurately predict the spectral type and luminosity of both B stars and A and F stars. He later derived (6) an indexmfrom the same filters. This index was a measure of the relative line blanketing near 4100Å compared to two filters above 4500Å. These three indices confirmed earlier work by many people, including Lindblad and Becker. References to this earlier work and to the systems discussed today can be found in Strömgren's article inBasic Astronomical Data(7).

Chromospheric activity as a function of age in main-sequence stars

1966 ◽  
Vol 24 ◽  
pp. 40-43
Author(s):  
O. C. Wilson ◽  
A. Skumanich
Keyword(s):  
Main Sequence ◽  
The Sun ◽  
Main Sequence Stars ◽  
Tentative Conclusion ◽  
Chromospheric Activity ◽  
General Field ◽  
Large Clusters

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

Southern Hemisphere Seti Survey: Five Years of Project Meta II

1997 ◽  
Vol 161 ◽  
pp. 611-621
Author(s):  
Guillermo A. Lemarchand ◽  
Fernando R. Colomb ◽  
E. Eduardo Hurrell ◽  
Juan Carlos Olalde
Keyword(s):  
Southern Hemisphere ◽  
Scattering Theory ◽  
Galactic Plane ◽  
Narrow Band ◽  
Neutral Hydrogen ◽  
Sky Survey ◽  
Inertial Frames ◽  
Interstellar Scattering ◽  
Extraterrestrial Origin ◽  
Spectral Channels

AbstractProject META II, a full sky survey for artificial narrow-band signals, has been conducted from one of the two 30-m radiotelescopes of the Instituto Argentino de Radioastronomía (IAR). The search was performed near the 1420 Mhz line of neutral hydrogen, using a 8.4 million channels Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earths rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 2 × 1013spectral channels analyzed, 29 extra-statistical narrow-band events were found, exceeding the average threshold of 1.7 × 10−23Wm−2. The strongest signals that survive culling for terrestrial interference lie in or near the galactic plane. A description of the project META II observing scheme and results is made as well as the possible interpretation of the results using the Cordes-Lazio-Sagan model based in interstellar scattering theory.

The Infancy of Solar-Type Stars and its Relevance for the Origin of Life

1997 ◽  
Vol 161 ◽  
pp. 267-282 ◽  
Author(s):  
Thierry Montmerle
Keyword(s):  
Main Sequence ◽  
Solar Nebula ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Necessary Condition ◽  
Sequence Evolution ◽  
T Tauri ◽  
Solar Type ◽  
Optical Domain ◽  
The Origin Of Life

AbstractFor life to develop, planets are a necessary condition. Likewise, for planets to form, stars must be surrounded by circumstellar disks, at least some time during their pre-main sequence evolution. Much progress has been made recently in the study of young solar-like stars. In the optical domain, these stars are known as «T Tauri stars». A significant number show IR excess, and other phenomena indirectly suggesting the presence of circumstellar disks. The current wisdom is that there is an evolutionary sequence from protostars to T Tauri stars. This sequence is characterized by the initial presence of disks, with lifetimes ~ 1-10 Myr after the intial collapse of a dense envelope having given birth to a star. While they are present, about 30% of the disks have masses larger than the minimum solar nebula. Their disappearance may correspond to the growth of dust grains, followed by planetesimal and planet formation, but this is not yet demonstrated.

On The Radii of Ap Stars

1976 ◽  
Vol 32 ◽  
pp. 49-55 ◽  
Author(s):  
F.A. Catalano ◽  
G. Strazzulla
Keyword(s):  
Observational Data ◽  
Line Width ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Ap Stars

SummaryFrom the analysis of the observational data of about 100 Ap stars, the radii have been computed under the assumption that Ap are main sequence stars. Radii range from 1.4 to 4.9 solar units. These values are all compatible with the Deutsch's period versus line-width relation.

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