THE ArAS III ANNUAL MEETING
30-31 August 2004, Byurakan, Armenia
The Third Annual Meeting of the Armenian Astronomical Society was held on August 30-31, 2004, in the Byurakan Astrophysical Observatory Conference Hall, where a number of outstanding meetings had been organized, including 4 IAU Symposia and 1 IAU Colloquium. It was organized jointly by the Armenian Astronomical Society and the Byurakan Astrophysical Observatory. The organizing committee consisted of H.Harutyunian, T.Magakian, A.Mickaelian, T.Movsessian, and E.Nikoghossian.
Some 50 astronomers participated in the Meeting, including scientists from the USA (J.Mather), Germany (F.Aharonian, T.Arshakian, V.Hambaryan), Spain (V.Tamazian), Jordan (R.Kandalyan), Yerevan State University (A.Sadoyan, K.Shahabasian), Yerevan Physics Institute (V.Gurzadyan), Institute of History of NAS RA (K.Tokhatyan, G.Vardanyan), and some 35 scientists from the Byurakan Observatory, as well as a number of students.
The meeting was opened with a welcome address by Haik Harutyunian, ArAS Co-President, followed by a report by Areg Mickaelian, another ArAS Co-President, who presented the ArAS activities during 2002-2004.
ArAS has at present 57 members, including 42 from Armenia and 15 from 6 other countries. The necessity for payments of the membership fees was stated to make possible any ArAS activities. ArAS is recognized by and have established good relations with the international scientific unions and societies, including the IAU (H.Harutyunian is the official liaison of the IAU Committee #46 in Armenia), EAS (ArAS is an affiliated society), EAAS (A.Mickaelian is a member of the EAAS Council and International Bureau, and T.Magakian is a members of the EAAS Scientific-technical Committee), International Olympic Committee for Astronomy (IOC) (ArAS is the official representative of IOC in Armenia, A.Oskanian is a member of the IOC Council), etc. Recently, relations with the NGO “European Integration” have been established. One of the main ArAS activities is the electronic publication of the Newsletter (editor: T.Magakian). Thus all ArAS members should participate actively in contributing in it with scientific, information and popular articles. The ArAS webpage maintains general information about the Armenian astronomy and ArAS, membership form and list of the members, ArAS Newsletters, the list of all Armenian astronomers, Byurakan Observatory and other Armenian institutes related to astronomy, useful links, etc. ArAS annual meetings have been and are important for activating of science in Byurakan, discussion of scientific topics and the ArAS affairs. ArAS has established an annual prize for young astronomers, which will be awarded for the first time at the end of this year. The ArAS Co-President Y.Terzian sponsors this initiative for this year. ArAS members have been active in educational affairs as well, including the organization of the Armenian astronomy Olympiads for school pupils, and casting of a popular astronomical TV program (L.Sargsyan). The publication of the “Dictionary of the Armenian astronomy” has been postpones because of the lack of information from many Armenian astronomers. It was asked to everybody to send asap their needed data for a quick publication of this important edition. A special gratitude was expressed to the sponsors of ArAS, Dan Weedman and David Nelson, due to whose contributions ArAS activities were possible. There are still a lot of things to do. ArAS still has no office and equipment, and all activities are being done by the Council members at their offices. It was stated that JENAM-2007 will be the main task for the ArAS for the next years, as well as establishment of the ArAS annual prize for outstanding astronomers and publication of the “Dictionary of the Armenian astronomy”.
22 scientific talks by 21 speakers were given, covering various aspects of astronomy. In addition to the talks on modern astronomical results, it is worth mentioning talks on archaeoastronomy in Armenia given by E. Parsamian and K. Tokhatyan. The abstracts of the talks are attached at the end of this page. The participants had possibility to discuss various topics also during the coffee breaks, lunches and the banquet, which took place after the Meeting. A discussion on the planned German-Armenian collaboration in astronomy was organized, taking the opportunity of the presence of three scientists from Germany, and with participation of a few Byurakan scientists already having contacts with German astronomers.
The Meeting was sponsored by Mr. David Nelson (USA), Executive Director of the Jinishian foundation.
Monday, August 30, 2004
E.S. PARSAMIAN
Byurakan Astrophysical Observatory (BAO), Armenia
The Armenian highland is one of the ancient cradles of civilization. Many investigators of the history of astronomy, having no facts to hand, came to conclusions that the ancient inhabitants of Armenia not only knew, but also took part in the formation of ancient of astronomy. The above statements had to be confirmed.
The most important discovery, which enriched our knowledge of ancient astronomy in Armenia, was the complex of platforms for astronomical observations on the Small Hill of Metzamor, which may be called an ancient "observatory". Investigations on that Hill show that the ancient inhabitants of the Armenian Highlands have left us not only pictures of celestial bodies, but a very ancient complex of platforms for observing of sky.
On the bank of the river Metzamor, some 30 km west of Yerevan, a great metal-producing center was found back to the third millennium B.C. Here on the Small Hill of Metzamor in 1966 the platforms for astronomical observations were discovered.
It was shown that in the years between 2800-2600 B. C. Sirius could have been observed at Solstice in the morning, in the rays of the rising Sun, this being so-called helical rising of Sirius. It is obvious from the data that Sirius, the brightest star in the hemisphere could have been the object of worship by the inhabitants of Metzamor. It is possible that, like the ancient Egyptians, the inhabitant of Metzamor related the first appearance of Sirius with the opening of the year.
Among the ancient monuments in Armenia there is a megalithic monuments, probably, being connected with astronomy. 250 km South-East of Yerevan there is the structure Zorats Kar is more then two meters high form stone rings resembling ancient stone monuments - henges in Great Britain and Brittany.
The diameter of the main stone ring of Zorats Kar is more than 30m and it is notable that on some stones found in the eastern part there are well polished round holes, which could have been used for the observation of the Sun in the days of equinox and solstice. Main ring is connected with megaliths in S-E direction by gate of two megaliths the distance between which more than between other stones. The middle line of gate has direction East-West.
John MATHER
Space Telescope Science Institute (STScI), Baltimor, USA
A review on the project of the James Webb Space Telescope (JWST, formerly New Generation Space Telescope, NGST) was given.
D.M. Sedrakian, A.A. SADOYAN, K.M. Shahabasyan, M.V. Hayrapetyan
Yerevan State University (YSU), Armenia
We will go through present stage of Gravitational Wave observatories and summarize main results of collaboration between Montana State University Billings and Yerevan State University on Gravitational Wave Sources. Rotating white dwarfs undergoing quasi-radial oscillations can emit gravitational radiation in a frequency range from 0.1-0.3 Hz. Assuming that the energy source for the gravitational radiation comes from the oblateness of the white dwarf induced by the rotation, the strain amplitude is found to be 10-25 for a white dwarf at ~50pc. We had calculated thermal energy loses through magneto-hydrodynamic mechanism during self similar oscillations to compare with energies emitted in GW band. We examine also possibility of gravitational radiation from white dwarfs undergoing self-similar oscillations which are fed by the energy of the differential rotation of the white dwarf. We consider two cases of angular momentum distribution. Assuming the energy of the self-similar oscillations causing gravitational wave emission is about 10% of the energy dissipated in the differentially rotating white dwarf, the strain amplitudes are again found to be less than 10-25 for a white dwarf at ~ 50pc. Nearby oscillating white dwarfs may provide a clear enough signal to investigate white dwarf interiors through gravitational wave astroseismology. Undamped quasi-radial oscillations rotating neutron stars and the gravitation radiation generated by them are discussed. Two possible sources of energy for maintaining these oscillations are mentioned: the energy of deformation of the decelerating neutron star (spin down) and the energy released during a jump in the star’s angular velocity (glitch). Expressions are derived for the intensity of the gravitational radiation and the amplitude of a plane gravitational wave for an earthbound observer. Estimates of these quantities are obtained for the Vela and Crab pulsars, for which the secular variation in the angular velocity is most often accompanied by irregular variations. It is shown that gravitational waves from these pulsars could be detected by the new generation of detectors.
T.A. MOVSESSIAN1, T.Yu. Magakian1, A.V. Moiseev2, M. Smith3
1- Byurakan Astrophysical Observatory (BAO), Armenia
2 – Special Astrophysical Observatory (SAO), Russia
3 – Astronomical Observatory Armagh, N. Ireland, UK
We present new imagery and Fabry-Perot scanning interferometry of Herbig-Haro jets and associated cometary reflection nebulae. Observations are carried out on 2.6m (Armenia) and 6m (Russia) telescopes. Morphology of reflection nebulae shows, that the outflow can form dusty helical structures on the walls of the cone. On other hand the helical structure was discovered in emission jet in HL/XZ Tau region by scanning Fabry-Perot interferometry. In fact we observe high velocity narrow jet with weaved low velocity helical emission structure. In two cases of HL/XZ Tau and HH83 jets acceleration of the jets was discovered. New scenario of two - high and low velocity component outflow system is suggested. Instabilities in boundaries of high velocity and low velocity flows as well as low velocity flow and ambient cloud can form helical wave structures, which we observe as reflection and emission features.
A.L. GYULBUDAGHIAN
Byurakan Astrophysical Observatory (BAO), Armenia
The results of radio observations on SEST telescope (Cerro La Silla, Chile) are given. The outflows were registered from the objects GRV8, GRV16, b14, b13b. From the object GRV8 (bipolar cometary nebula), two lobes were registered, both red-shifted (with velocity +2km/s in respect of ambient cloud). From the object GRV16 (a cone-like nebula) a blue-shifted outflow was observed with –4km/s in respect to ambient cloud. For the object b14 (star-forming region) bipolar outflow with two HH-like objects was observed, and for b13b (star-forming region) a quadruple outflow.
N. Mauron1, M. Azzopardi2, K.S. GIGOYAN3, T.R. Kendall4
1 – University of Montpellier II, France
2 – Observatoire de Marseille, France
3 - Byurakan Astrophysical Observatory (BAO), Armenia
4 –Observatoire de Grenoble, France
We present the first results of a new survey for finding cool N –type carbon( C ) stars in the halo of the Galaxy. Candidates were selected in the 2MASS Second Incremental Release database with JHK, colors typical red AGB C stars and K < 13, and subsequently checked through medium resolution slit spectroscopy. We discovered 27 new C stars plus one known previously and two similar objects in the Fornax and Sculptor dwarf galaxies. We determine and discuss the properties of our sample, including optical and near-infrared colors, radial velocities, as well as H(Alpha) emission and variability that are frequent, all these characteristics being compatible with an AGB C - type classification. Surprisingly, of the 30 studied objects, 8 were found to have small but measurable proper motions in the USNO-B1.0 catalogue, ranging over 8 < PM < 21 mas/yr and opening the possibility that some objects could perhaps be dwarf carbon stars. Yet, a detailed analysis based on comparison with the sample of known carbon dwarfs leads us to consider these PM as incompatible with the broader picture suggested by the other data taken as a whole. So, we adopt the view that all objects are of AGB type, i. e. luminous and distant. Because the stream of Sagittarius dwarf galaxy is known to be the dominant source of luminous C stars in the halo, we chose to determine distances for our sample by scaling them of the 26 known AGB C stars of the Sgr galaxy itself, which are found to be, in the K band, near 0.5 mag less luminous than the average LMC C stars for a given J - K color. The obtained distances of our halo stars range from 8 to 80 kpc from the Sun. Then, examination of position and radial velocities shows that about half belong to the Sgr stream. Our findings suggest that numerous AGB C stars remain to be discovered in the halo. Long term K - band monitoring would be of great value to ascertain distance estimates through the period-luminosity relation, because a large fraction of our sample is probably made of Mira variables.
V.V. HAMBARYAN
Astrophysical Institute Potsdam (AIP), Germany
I will present results of ongoing systematic search, identification and study of variable X-ray sources of galactic and extragalactic origin, using available large amount of archived data, based on ROSAT, Chandra and XMM-Newton observations. I will discuss methodical aspects of the problem based on a Bayesian approach of variability and periodicity search. It will also address current problems in understanding physical conditions and astrophysics underlying the mechanisms responsible for the observed variability of stars and active galactic nuclei. In particular, I will focus on fundamental physical questions concerning the coronae of normal stars, heating mechanism of them, the role of flares and microflares of heating. How does it depend on parameters such as mass, convection, rotation and age?
ACCURATE POSITIONS AND OTHER RESULTS
A.M. MICKAELIAN
Byurakan Astrophysical Observatory (BAO), Armenia
Accurate measurements of the positions of 1101 First Byurakan Survey (FBS) blue stellar objects have been carried out on the DSS1 and DSS2 (red and blue images). To establish the accuracy of the DSS1 and DSS2, measurements have been made for 153 AGN for which absolute VLBI coordinates have been published. The rms errors are: 0.45" for DSS1, 0.33" for DSS2 red, and 0.59" for DSS2 blue in each coordinate, the corresponding total positional errors being 0.64", 0.46", and 0.83", respectively. The highest accuracy (0.42") is obtained by weighted averaging of the DSS1 and DSS2 red positions. It is shown that by using all three DSS images accidental errors can be significantly reduced. The comparison of DSS2 and DSS1 images made it possible to reveal positional differences and proper motions for 78 objects (for 62 of these for the first time), including new high-probability candidate white dwarfs, to find objects showing strong variability (high-probability candidate cataclysmic variables), and objects having images showing slight extension in DSS2 red and IR (candidate QSOs and AGN).
A.M. Mickaelian1, L.A. SARGSYAN1, L.K. Erastova1, K.S. Gigoyan1, S.K. Balayan1,
L.R. Hovhannisyan1, R. Nesci2, S. Gaudenzi2, E. Massaro2, C. Rossi2, S. Sclavi2, D. Trevese2,
D. Weedman3, J. Houck3, D. Barry3, B. Brandl3, H. Hagen4
1 – Byurakan Astrophysical Observatory (BAO), Armenia
2 – Universita di Roma “La Sapienza”, Italy
3 – Cornell University, Ithaca, NY, USA
4 – Hamburger Sternwarte (HS), Germany
The First Byurakan Survey (FBS) is the largest spectral survey in the Northern sky covering 17,000 sq. deg at high galactic latitudes. 1500 Markarian galaxies, thousands of blue stellar objects and late-type stars have been discovered and optical identifications of 1600 IRAS sources have been made using this observational material. Some 20,000,000 spectra are present in FBS giving a key to understanding of the nature of these objects. The project of digitization of FBS is active since 2002 in frame of an international collaboration between the Byurakan Observatory (Armenia), Cornell University (USA) and Universita di Roma "La Sapienza" (Italy) and has brought to creation of a unique database: the Digitized First Byurakan Survey (DFBS). Beside the scanning and archiving, plate solution, extraction software, wavelength and flux calibration, templates for different types of objects, a numerical classification scheme, a catalog of spectra, user interface and DFBS web page are being made. At present all FBS plates have been scanned and reduction software is being created and applied. The DFBS database will be open at the end of 2004. An automatic selection of different types of interesting objects will be possible and searches for new bright QSOs, faint Markarian galaxies, white dwarfs, cataclysmic variables, carbon stars, as well as optical identifications of radio, IR and X-ray sources will be undertaken.
A.M. Mickaelian1, L.R. HOVHANNISYAN1,
D. Engels2, H. Hagen2, D. Reimers2, W. Voges3, F.-J. Zickgraf2
1 – Byurakan Astrophysical Observatory (BAO), Armenia
2 – Hamburger Sternwarte (HS), Germany
3 – Max-Planck Institut fuer Extraterrestrische Physik (MPE), Munchen, Germany
The Hamburg/ROSAT-FSC Catalogue (HRFC) of optical identifications of X-ray sources is presented. The HRFC includes all 2791 sources from the ROSAT-FSC with |b|>30, DEC>0, and ROSAT countrate CR>0.04. For the optical identifications, we have used the Hamburg Quasar Survey (HQS) digitized spectroscopic plates, DSS1 and DSS2 (blue, red, and IR) images, MAPS photometric data, USNO-B2.0 (for proper motions), NVSS/FIRST radio and IRAS/2MASS infrared catalogs, and other available data from the existing catalogs. From the DSS images we have obtained positional, brightness, color, extension, variability, PM information, and have given the morphological classification, have measured the optical-to-X-ray distance. SIMBAD and NED data for known (bright) objects have been taken. Cross-correlations have been made with the AGN, WD and CV catalogs (322/8/7 associations, respectively). Using a refined and improved technology compared to the HRC (Zickgraf et al. 2003), we managed to identify 97% of sources (2696 sources), compared to 82% in HRC. 2696 sources are identified with 3187 objects, including 2263 with a single object; other 144 have identification with double or multiple object; thus we are left with only 289 ambiguous identifications. In addition we have found 79 by-product objects near the X-ray positions, mainly new faint QSOs. QSOs and AGN represent the largest group of X-ray counterparts (52.3%), bright stars (including late type stars, but excluding WDs and CVs) are counterparts for 34.1% of sources, and the bright galaxies and groups of galaxies comprise only 5.3% and 4.1%, respectively. We have found a number of interacting/merging galaxies being counterparts for X-ray sources (2.8%), as well as 1.2% WDs and 0.1% CVs. One of the striking results of this program is the presence of a large number of binary QSO candidates among the sample of QSOs. The HRFC may be used for selection and studies of complete samples of various classes of X-ray emitters.
Tuesday, August 31, 2004
H.S. Chavushian, H.V. Pikichian, A.V. OSKANIAN, G.H. Broutian
Byurakan Astrophysical Observatory (BAO), Armenia
As we know, in the case of spherical symmetry it is possible to restore by the method of Zeipel [1] the density of the three-dimensional distribution of stars by means of the distribution of two-dimensional (surface) density of stars in "reach" clusters. In the case of poor sample of stars (as, for example, in open clusters) it is more effective to use the one-dimensional distribution function suggested by Plummer [2] which is the projection of observed two-dimensional distribution of stars on an arbitrary axis passing through the center of the cluster. Making use of the fact that the direction of the projection axis is arbitrary M. Mnatsakanian [3] succeeded to improve the process of construction of one-dimensional projection of star distribution by means of analytic averaging of all the values of azimuths of direction of projection axis. It became possible to investigate more poor samples such as the partial density of flare stars in Pleiades. It was shown [4] that there is region of absence of flare stars – a “hole” in the centre of the cluster. Afterwards it came out that the existence of this “hole” was conditioned by existence of bright stars and diffuse matter in the centre of the cluster that results in observational selection of discovering of stellar flares. The “hole” was filled gradually with the growth of the quantity of flare stars at the expense of newly discovered flare stars [5]. An investigation based on a more complete observational material [6] showed the existence of a region of flare star “deficit” in the function of two-dimensional distribution in the middle region of radius of the cluster 2.8£r£3.5 pc.
The accuracy of the function built by us by M.Mnatsakanian method during the process of restoration of three-dimensional density of Pleiades flare stars was not sufficient (non-physical solution) in the region of above mentioned deficit. So it became necessary to work up a new – finer method [7] of construction of one-dimensional projection of star distribution. It makes possible to us more completely the initial information – the integral function of flare star distribution. The new equation of Abel’s class obtained and solved by us allows restoring the one-dimensional projection of distribution density with enough smoothness. Afterwards by means of this projection it was built the real profile of three-dimensional distribution in flare star deficit region and were quantitatively estimated the parameters of this profile [7] (the equivalent width of this region – 0.56 pc, and the deficit measure – 47%).
The comparison of the two-dimensional density function restored from the three-dimensional distribution by means of modeling by inverse calculation method with the same function obtained from the observations shows that the realized restoration of three-dimensional distribution is correct in 1.2£r£7.0 pc region, while in the central part of the cluster 0<r<1.2 pc the problem needs new special investigation.
The problem of restoration of flare star three-dimensional distribution we examined also for sliding separate 90° sectors. It was shown that the property of flare star deficit is characteristic not only for the entire cluster, but for each 90° sector built by continuous sliding. Thus, the discovered region of flare star deficit is not a consequence of a local irregular fluctuation revealed spontaneously in flare star distribution, but just like the whole cluster it also has a spherical-symmetric distribution around the cluster center in 2.8£r£3.5 pc area.
Thus, this investigation mentions that the discussed property of flare star deficit in Pleiades is real and needs physical explanation.
References
1. H. von Zeipel, Ann. Paris Obs. Mem., v. 25, p. F1-F101, 1908.
2. H.C. Plummer, M.N.R.A.S., 71, 460, 1911.
3. M.A. Mnatsakanian, Rep. AS Arm., 49, 33, 1969.
4. L.V. Mirzoyan, M.A. Mnatsakanian, IBVS, 528, 1, 1971.
5. L.V. Mirzoyan, M.A. Mnatsakanian, G.B. Ohanian, in: "Flare Stars, Fuors, and Herbig-Haro Objects", ed. L.V. Mirzoyan, AS Arm. SSR, Yerevan, 1980, p. 113.
6. H.S. Chavushian, A.V. Oskanian, G.H. Broutian, Astrofizika, 42, 537, 1999.
7. H.S. Chavushian, H.V. Pikichian, A.V. Oskanian, G.H. Broutian, Astrofizika, 47, 369, 2004.
F. AHARONIAN
Max-Planck-Institut fur Kernphysik (MPK), Heidelberg, Germany
I will discuss the basic motivations, achievements and status of ground based gamma-ray astronomy, and highlight the recent exciting results related to different areas of modern astrophysics and cosmology.
V.G. GURZADYAN
Yerevan Physics Institute (YerPhI), Armenia
A review of our knowledge on the Cosmic Microwave Background (CMB) was given. The importance of the CMB structure for understanding the geometry of the Universe, percentage of the visible and dark matter, and its present large scale structure was stressed. Results from COBE, BOOMERanG and WMAP experiments were discussed. The WMAP satellite confirms the results obtained by COBE and BOOMERanG.
H.A. HARUTYUNIAN
Byurakan Astrophysical Observatory (BAO), Armenia
A hypothesis is considered that the spectra of young extragalactic objects possess an intrinsic redshift decreasing in the course of their evolution is considered. A number of observational facts are presented to show that the quasars are mostly situated at non-cosmological distances and therefore the observed redshifts in their spectra could not be caused due to the cosmological expansion but most probably have local origin. The possibility of revealing the features of intrinsic redshifts in spectra of postquasar objects is suggested accepting the majority of quasars to be local objects ejected from nuclei of galaxies. We argue for the affected by intrinsic redshifts luminosity function of local galaxy population made poorer in the faint end. This approach is used to consider the problem of excess of faint blue galaxies.
COMPACT STAR-FORMING REGIONS
T.Yu. MAGAKIAN, T.A. Movsessian, E.H. Nikogossian, E.R. Hovhannessian
Byurakan Astrophysical Observatory (BAO), Armenia
The work on the project started in 1998 is described. It includes cataloguization of nebulous objects in the dark clouds, searches of new HH objects and flows, and their detailed studies, as well as the discovery and photometry of new H-alpha emission stars in compact stellar groups. These observations are performed mainly on 2.6m telescope in Byurakan. As the samples the results for such fields as L1340, GM1-61, GM2-30, RNO127, RNO129 and others are shown.
R.R. ANDREASYAN
Byurakan Astrophysical Observatory (BAO), Armenia
The main observational characteristics have now been determined for most of 1300 pulsars: puls period P, its time variations P`, average radiation flux density at different frequencies (S400, S1400), dispersion measure DM, rotation measure RM, pulse equivalent width W, and many others. The enormous number of pulsar data of different kinds that have been collected provide extensive opportunities for their statistical use. Pulsars deserve to be considered as probes of the interstellar medium, since their distances, determined from their dispersion measures, are assumed to be more or less reliable for a large sample of these objects. The main uncertainties in the procedure of determination of pulsar’s distances are related to the inadequate knowledge of the electron density distribution in the Galaxy. All distances of pulsars are determined now using the model of Taylor & Cordes (1993) for the Galactic electron density distribution.
We present here a new method, which can be used for the study of electron density distribution in the Galaxy, without using of any model for it. From the equation DM(R)=R∫ne(R)dR for dispersion measure, we have ne(R)=d(DM)/d(R), where ne(R) is the electron density in the point with distance R from the Sun. In fact, if we have the dependence between DM and R in the plane of Galaxy for every direction, we can obtain electron density in every point of the Galactic plane. For the relation of DM – R we shall take the averaged relation between observed values of DM pulsars and values of independent distances Ri, obtained by the independent from the DM method. The method for obtaining of Ri will be discussed below. As an averaging procedure we use the method, when the coordinates (l;R) (where - l is the galactic longitude, R – the distance from the Sun) of the center of averaging region, for example, with the constant number of pulsars, is changed smoothly in the plane of Galaxy. Then, using the above mentioned formulae, we determine the distribution of electron density in the plane of Galaxy, solving in fact the inverse problem, without using of any model for electron density distribution. We have already prepared a computing program for the proposed procedure. As a good test of the program we use the comparison of obtained distribution with the spiral arm model of Georgelin & Georgelin, (1976), or Taylor & Cordes, (1993). At first we used distances, obtained from the DM data and the Taylor & Cordes (1993) model of electron density distribution in the Galaxy. If our program is working well, using these distances we must receive again the Taylor & Cordes model for the galactic distribution of electron density. The calculations show good conformity of received in this way electron density distribution with the Taylor and Cordes (1993) model, what we see from the picture. In this program we can change the averaging area, the averaging step, the sample of used pulsars, choosing them by their physical or other parameters. So, if we have the homogeneous independent from DM distances of pulsars, spread over the Galactic plane, we can find the electron density distribution in the plane of Galaxy, using this program.
Now we describe the method for obtaining of independent distances Ri of pulsars. It Is generally accepted that pulsars radiate due to the loss of rotational energy of neutron stars. Well known parameters derived from the observed data are timing age
T=P/2P`, (1)
and “spin-down luminosity”
E` = -4π2IP`P-3, (2)
where P and P` are period and its time variation, I = 1045 gcm2 – is the moment of inertia of pulsars.
We studied the relation of radio luminosity L of pulsars from the age T and from the “spin-down luminosity” E`. For this study we used observational data for radio luminosity at 400 and 1400 MHz. We found a good linear correlation between Log(L) and Log(E`). The correlation becomes better, if we use only the pulsars with age 106 < T < 108 year.
Log(L) = 0.452 + 0.209(Log(E`) –28) (3)
For pulsars with T< 106 year and T>108 year there is no such correlation. There is also a linear relation between Log(L) and Log(T), where Log(L) decreases with the increase of Log(T).
Log(L) = 2.78 - 0.22Log(T) (4)
If we have these relations for some groups of pulsars, we can use these relations to find the new (theoretical) radio luminosity LT for all pulsars with known parameters E` and T. This new radio luminosity can be used for the determination of pulsars distances Ri using their observed flux densities S
RI = (LT/S)1/2. (5)
These distances Ri will be independent from the dispersion measures DM of pulsars and can be used for the study of electron density distribution of Galaxy. We did the preliminary study of this problem, using the mentioned relations. The result of this study is on the fig.
It must be said that the relations between Log(L) - Log(E`) and Log(L) - Log(T) in fact are relations between Log(L) and observed values of period P and its time variation P` (see the formulas (1) and (2)) . Such relations have been studied in Stollman (1987), Vivekanand & Narayan (1981) Andreasyan & Arshakian (2001), where was considered the relation of type
L = γPαP`δ (6)
Taking its logarithm, we obtain a linear equation in α, β and log(γ).
After the finding of three parameters α, β and log(γ) by the least squares method, in Andreasyan & Arshakian (2001) this relation was used for the determination of independent distances of pulsars. It is obvious, that this relation will give better results than above mentioned relations (formulas (3) and (4)), where we find and use only two parameters of linear relation between Log(L) - Log(E`), or Log(L) - Log(T).
We now study this relation (6) using incomparably larger sample of pulsars, than in previous works. The results of this study for various samples of pulsars are given in Table1. Using the values of α, β and log(γ) from the Table 1, and observed data of P and P`, we can find the LT from the relation (6), and Ri from the relation (5). We use these Ri for the study of electron density distribution by the above-mentioned method and have the preliminary result.
References
Andreasyan R., and Arshakian T., 2001. The Radio Luminosity of pulsars and the distribution of interstellar electron density. Astrophys. and Space Sci., 278, 175.
Georgelin Y.M. and Georgelin Y.P., Astron. Astrophys., 49, 57, (1976).
Stollman G.M. Astron. Astrophys., 172, 152 (1987).
Taylor, J.H. and Cordes, J.M., 1993. Pulsar Distances and the Galactic distribution of free electrons. Ap.J. 411, 674.
Vivekanand M. and Narayan, R., J. Astron. Astrophys., 102, 315 (1981).
III. PMS-STARS IN NGC7129
T.Yu. Magakian, T.A. Movsessian, E.H. NIKOGOSSIAN
Byurakan Astrophysical Observatory (BAO), Armenia
By the slitless method (H-alpha filter + grizm) 22 emission stars are discovered in the central and northeast part of star cluster NGC 7129. The 16 of them are new ones. This sample is completed up to mv< 20.0. The emissions stars are non-uniformly distributed on a field of the cluster and concentrated in the center part. It was using V, R and I magnitudes of more than hundred stars of the cluster we had been determined average extinction Аv = 1.7±0.27 in research area by the method of the least squares. On the photometric parameters (VRIJHK) the majority of emission stars with a high probability can be related to T Tau objects.
A.M.MICKAELIAN1, M.P.Véron-Cetty2, P.Véron2
1 – Byurakan Astrophysical Observatory (BAO), Armenia
2 – Observatoie de Haute-Provence (OHP), France
The Catalogue of quasars and active nuclei by Véron-Cetty & Véron (11th Edition, 2003), contains 64,866 AGN listed in three tables as QSOs, BLL, and AGN. The Catalogue contains all AGN with published redshifts. However, the data given are not homogeneous and the Catalogue could not be used for any statistical investigation. Having a homogeneous set of magnitudes would be especially important for calculating absolute magnitudes, constructing luminosity functions and cosmological analysis. The Minnesota Automated Plate Scanner (MAPS) catalogue (Cabanela et al. 2003), recently released, gives 0.2" rms positional and 0.2m rms photometric (magnitudes and colors) homogeneous data for all objects present in the POSS plates with |b|>20. We decided to cross-correlate the AGN catalogue with MAPS to make it homogeneous and statistically useful. The results are presented, including some preliminary analysis of different sets of AGNs.
T.G. ARSHAKIAN, E. Ros, J.A. Zensus, M.L. Lister
Max-Planck-Institut fur Radioastronomie (MPIfR), Bonn, Germany
We study the cosmological evolution of flat-spectrum quasars from the complete 2 cm (15 GHz) Very Long Baseline Array (VLBA) survey. The sample is complete to flux-density limits of 1.5 Jy for positive declinations and 2 Jy for declinations between 0 and -20 degrees, and comprises 133 active galactic nuclei. A significant positive and negative evolutions are found for low-redshift (z<0.5) and high-redshift (z>1.7) quasars implying that jet activity phenomena were more populous at redshifts between z~0.5 and z~1.7. It is shown that low- and high-luminosity quasars display different evolutionary behavior which is supporting the luminosity dependent evolution of flat-spectrum compact quasars.
Rafik KANDALYAN1,2
1 – Byurakan Astrophysical Observatory (BAO), Armenia
2 – Institute of Astronomy and Space Sciences, Al Al-Bayt University, Jordan
The X-ray, radio continuum and FIR properties of the OH megamaser galaxies are discussed. Most of the radio sources in megamaser galaxies have comparable flat radio spectra between 1.49 and 8.44 GHz, and high brightness temperature. In OH megamaser galaxies the radio continuum is predominantly non-thermal, powered either by compact starburst or AGN. The thermal radio emission can be neglected in these galaxies. The observed flat radio spectra, high brightness temperatures imply the presence of an AGN in these galaxies. On the basis of a sample of megamaser galaxies it is found that X-ray emission is tightly related to the OH line width. The OH line width is related to both radio continuum and FIR emission; however the last correlation is tiny and less significant. The OH line width, radio continuum and the X-ray are related to the central mass of megamaser galaxies. There is a weak correlation between the X-ray and radio continuum in megamaser galaxies, which may due to multiple up-scattered synchrotron photons and nuclear jet activity. These results suggest that in OH megamaser galaxies an active nucleus may dominate, although some megamasers may be powered by compact starburst.
S.G. ISKUDARIAN
Byurakan Astrophysical Observatory (BAO), Armenia
M 87 is the active nucleus of Our Supergalaxy. M 87 with its immediate environment is the nearest "void". M87 is connected with the closed loop-like superstring, with has been ejected from M 87. M 87 itself with its wide environment is a huge monopole with its field of forces. This many-colored behavior of M 87 is result of periodic acting of the general regularity, which acts in the micro and macro worlds of the Universe, ensured by this way the unity of the Universe. It is the origin, formation, ejection of the first type stellar population from the entrails of the second one (in protogalactic stage, of course). In micro world it is b (beta) decay.
ASTRONOMICAL METHOD FOR ABSOLUTE DATING OF ROCK CARVINGS OF CONSTELLATIONS
Karen TOKHATYAN
Institute of History of the Armenian National Academy of Sciences, Yerevan, Armenia
Rock Art of Armenia was mentioned for the first time by Movses Khorenatsi who has preserved an ancient witness of Rock Art in a marvellous form - the dream of Mesrop Mashtots. Khorenatsi’s second witness on rock carving in connection with the hero Torq, the demiurge of sculpture. More direct is Anania Shirakatsi’s information: “The receptors of ancestors were more sensitive than ours, due to which they could notice not only the movement of the Sun but also inscibe, i.e. carve, and recognize the movements of all the other luminaries and stars”. This may be considered as an earliest bibliographical evidence of antiquity and trustworthiness, reliability of the rock carvings with astronomical content. Some rock‑carvings of astronomical significance had an applied function: measuring time, marking the time and the geographical location. There are 30 and 31‑day solar calendars, 7, 14 and 28 or 29‑day lunar calendars, 12-month calendars, 354/365 day annual calendars.
Some rock carvings in Armenia represent constellations. They are discovered at the Vardenis Mountain Pass, at 2,410m a.s.l., near an ancient caravan road with cyclopean fortresses. The stars are represented by dots and circles, corresponding to their brightness. It is common knowledge from astronomy that all the stars have their proper movements. The movements are too slow and the derivations too small in order to be noticed by man during a lifetime, but perceptible enough to shift noticeably during millennia. Method is based on comparing the engraved configuration of a certain constellation with its present view, and the assumption that the image was executed with enough precision, i.e. was similar to the shape of that constellation at the moment of engraving. Reconstructing the shape and position of the constellation in the past and comparing them with the view in the rock carving, we can receive precise time it was carved, i.e. the absolute age.
