arXiv subjects

E. H. Nikoghosyan

Publications and source records attributed to E. H. Nikoghosyan.

8 recordsLinked to original sources

arXiv2021

Structure of IRAS 05168+3634 star-forming region

This study aims to determine the main physical parameters (N(H2) hydrogen column density and Td dust temperature) of the Interstellar medium, and their distribution in the extended star-forming region, which includes IRAS 05156+3643, 05162+3639, 05168+3634, 05177+3636, and 05184+3635 sources. We also provide a comparative analysis of the properties of the Interstellar medium and young stellar objects. Analysis of the results revealed that Interstellar medium forms relativity dense condensations around IRAS sources, which are interconnected by a filament structure. In general, in sub-regions Td varies from 11 to 24 K, and N(H2) - from 1.0 to 4.0 x 10^23 cm^(-2). The masses of the ISM vary from 1.7 x 10^4 to 2.1 x 10^5 Msol. All BGPSv2 objects identified in this star-forming region are located at the N(H2) maximum. The direction of the outflows, which were found in two sub-regions, IRAS 05168+3634 and 05184+3635, correlates well with the isodenses direction. The sub-regions with the highest N(H2) and Interstellar medium mass have the largest percentage of young stellar objects with Class I evolutionary stage. The wide spread of the evolutionary ages of stars in all sub-regions (from 10^5 to 10^7 years) suggests that the process of star formation in the considered region is sequential. In those sub-regions where the mass of the initial, parent molecular cloud is larger, this process is likely to proceed more actively. On the Gaia EDR3 database, it can be assumed that all sub-regions are embedded in the single molecular cloud and belong to the same star-forming region, which is located at a distance of about 1.9 kpc.

astro-ph.GA↗

arXiv2018

Ecology of Near-Earth Space

The technical achievements of our civilization are accompanied by certain negative consequences affect the near-Earth space. The problem of clogging of near-Earth space by "space debris" as purely theoretical arose essentially as soon as the first artificial satellite in 1957 was launched. Since then, the rate of exploitation of outer space has increased very rapidly. As a result, the problem of clogging of near-Earth space ceased to be only theoretical and transformed into practical. Presently, anthropogenic factors of the development of near-Earth space are divided into several categories: mechanical, chemical, radioactive and electromagnetic pollution.

physics.space-ph↗

arXiv2016

New eruptive variable in the massive star-forming region associated with IRAS 18507+0121 source

Aims. We report the discovery of a strong outburst of the embedded young stellar object (YSO), namely UKIDSS-J185318.36+012454.5, located in the star-forming region associated with IRAS 18507+0121 source and GAL 034.4+00.23 HII region. Methods. Using the archival photometric data and images we determined the amplitude and the epoch of the outburst, as well as the evolution stage and the basic parameters of the object. Results. According to the near and mid-infrared colors and spectral energy distribution, we classify the object as an intermediate-mass young stellar object (YSO) with Class 0/I evolution stage. The outburst occurred in the period of 2004-2006. The amplitude of brightness is as least Ks = 5.0 mag. The summation of the photometric and spectral data does not allow to classify UKIDSS-J185318.36+012454.5 as FUor or EXor. We can consider it as an eruptive variable with mixed characteristics or MNor type object.

astro-ph.SR↗

arXiv2016

Search for Compact Stellar Groups in the Vicinity of IRAS Sources

The results of a search for compact clusters in the vicinity of 19 IRAS sources based on data from the GPS UKIDSS and Spitzer GLIMPSE surveys are presented. Overall, clusters have been identified in 15 regions. Clusters are identified for the first time in 4 regions (IRAS 18151-1208, IRAS 18316-0602, 18517+0437, 19110+1045). In 5 regions (IRAS 05168+3634, 05358+3543, IRAS 18507+0121, IRAS 20188+3928, IRAS 20198+3716) the compact groups we have identified are substructures within more extended clusters. The radii of the identified groups and the surface star density are widely scattered with ranges of 0.3-2.7 pc and 4-1360 stars/pc^2, respectively. In 11 of the clusters, the IRAS sources are associated with a pair or even a group of YSOs. The groups identified in the near IR include representatives of a later evolutionary class II among the stellar objects associated with the IRAS sources.

astro-ph.SR↗

arXiv2015

The search of the stellar clusters in vicinity of YSOs with high and middle masses

The results of the searching on the bases of GPS UKIDSS survey's data of dense compact stellar clusters in the vicinity of 20 YSOs with high and middle masses are presented. Totally we have revealed clusters in 13 areas. Around 5 objects (IRAS 18151-1208, IRAS 18316-0602, IRAS 19110+1045, IRAS 19213+1723, IRAS 20056+3350) they are newly detected. The radii and stellar density have significant gradient: from 0.2 to 2.7 pc and from 3 to 1000 stars/arcmin^2 respectively.

astro-ph.SR↗

arXiv2015

Statistical Analysis of stars with Ha emission in IC 348 Cluster

In this work the results of the statistical analysis of the 215 stars with Ha emission in the IC 348 cluster are presented. The sample is completed to R<20.0.The optical radius is about 11 arcmin. The percentage of emission stars increase from bright to fainter objects and to the range of 13.0<R-AR<19.0 reaches 80%. The ratio between WTTau and CCTau objects is 64% and 36%. The 70% of X-ray sources are WTTau stars. The age of WTTau and CTTau objects are about 2*106 years. The age of the non emission stars with a mass less solar is about 2*106 years also, but non emission more massive objects are "older", the age of them is about 7*106 years. The most massive stars with a low level of activity is concentrated in a small dense central core of the cluster with a radius about 1 arcmin, and apparently, they are generated during an earlier wave of star formation in the cluster.

astro-ph.SR↗

arXiv2015

The search and study of PMS stars with Ha emission

One of the most prominent features of young objects in the optical range is the presence of emission lines, in particular Ha at 6563A. Therefore, Ha emission is the most common spectroscopic means for identifying young stars. We present the search's results of PMS stellar objects in the several star forming regions carried out on 2.6 m telescope in Byurakan observatory. We have used the method of slit-less spectroscopy employing a grism in combination with a narrow-band Ha interference filter to detect the objects with Ha emission.

astro-ph.SR↗

arXiv2015

The Multiple Systems in The Young Stellar Cluster IRAS 05137+3919

Four binary objects and one triplet have been revealed in the young stellar cluster located in the vicinity of IRAS 05137+3919 source on a distance 4.4 kpc with the use of statistic analysis. They are including the pair of AeBe stars. The percentage of the multiple systems in the cluster is mf = 5 and cp = 10.The mass of the multiple systems' components are located in the range from 1 to 8 Msol and log P (rotation period in years) - from 4.4 to 4.7. The median value of the mass ratio of the components is q = 0.86. The percentage of the multiple systems and their parameters in this cluster is resembling with the data obtained in the other star forming regions (ONC, Perseus, U Sco A), in which the value of mf and cp parameters are comparable with the results obtained for field's stellar population.

astro-ph.SR↗