Blue Stellar Objects Research Articles

DSS1/DSS2 astrometry for 1101 First Byurakan Survey blue stellar objects: Accurate positions and other results

Accurate measurements of the positions of 1101 First Byurakan Survey (FBS) blue stellar objects (the Second part of the FBS) 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 �� ,a nd 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, and to find objects showing strong variability, i.e. high-probability candidate cataclysmic variables.

MULTIWAVELENGTH SEARCH FOR AND STUDIES OF ACTIVE GALAXIES: AN INTERNATIONAL COLLABORATION BETWEEN THE BYURAKAN OBSERVATORY AND OBSERVATOIRE DE HAUTE-PROVENCE

An international collaboration on the multiwavelength search for and studies of active galaxies between the Byurakan Astrophysical Observatory (Armenia) and Observatoire de Haute-Provence (France) has been ongoing since 1997. The blue stellar objects of the first Byurakan survey have been studied in order to reveal and build a sample of new bright quasistellar objects and to determine their surface density. On the basis of optical identifications of 1577 IRAS point sources, a new (Byurakan-IRAS galaxy) sample of IRAS galaxies has been constructed and studied. 90 bright Seyfert 1 galaxies have been observed with a high resolution to make a fine analysis of their emission line profiles and to study their emission line regions. A new programme of investigation of Roentgen Satellite (ROSAT) sources identified by the Hamburg quasar survey has been conducted to search for new narrow-line Seyfert 1 galaxies. Databases and observations in the optical, infrared, radio and X-ray ranges are being used.

First Byurakan Spectral Sky Survey. Blue Stellar Objects. XII. The Region -3° ≤ δ ≤ +1°

The twelfth list of blue stellar objects in the second part of the First Byurakan Spectral Sky Survey (FBS) is presented. This list contains 143 objects in the region -3° ≤ δ ≤ +1° at high latitudes with an area of approximately 992 square degrees (62 fields). The objects have magnitudes V of 11.8-18.1 and B-V colors ranging from -0.82 to +0.81. Of the 143 objects, 51 have been discovered for the first time. Equatorial coordinates, V magnitudes, color indices, and preliminary classifications of the objects are given. DSS identification charts are given for the newly discovered objects.

Confirmation of SBS 1150+599A as an Extremely Metal-poor Planetary Nebula

SBS 1150+599A is a blue stellar object at high Galactic latitude discovered in the Second Byurakan Survey. New high-resolution images of SBS 1150+599A are presented, demonstrating that it is very likely to be an old planetary nebula in the galactic halo, as suggested recently by Tovmassian et al. An Hα image taken with the WIYN 3.5 m telescope and its tip-tilt module reveals the diameter of the nebula to be 92, comparable to that estimated from spectra by Tovmassian et al. Lower limits to the central star temperature were derived using the Zanstra hydrogen and helium methods to determine that the star's effective temperature must be higher that 68,000 K and that the nebula is optically thin. New spectra from the Multiple Mirror Telescope and Fred L. Whipple Observatory telescope are presented, revealing the presence of strong [Ne V] λ3425 lines, indicating that the central star temperature must be higher than 100,000 K. With the revised diameter, new central star temperature, and an improved central star luminosity, we can constrain photoionization models for the nebula significantly better than before. Because the emission-line data set is sparse, the models are still not conclusive. Nevertheless, we confirm that this nebula is an extremely metal-poor planetary nebula, having a value for O/H that is less than 1/100 solar, possibly as low as 1/500 solar.

QSOs in the Field of the Seyfert 1 Galaxy NGC 5548

ABSTRACTNew spectrophotometric observations are presented for three blue stellar objects pinpointed as candidate optical identifications of ROSAT X‐ray point sources in the field around the Seyfert 1 galaxy NGC 5548. They are shown to be medium‐redshift QSOs. In combination with cataloged data on QSOs in several square degrees around NGC 5548, the areal density of QSOs immediately around the galaxy may exceed the average values determined from various surveys. This result, together with the configuration, suggests that these QSOs may be physically associated with NGC 5548.

The Blue Stellar Objects of the First Byurakan Survey

AbstractThe Second part of the FBS is devoted to the discovery and study of blue stellar objects. It was carried out in an area of 4009 deg2 and identified 1103 objects: hot subdwarfs and white dwarfs, cataclysmic variables, QSOs and Seyfert galaxies, etc. The discovery of new bright QSOs led to a re-evaluation of their surface density (0.012 deg−2). Several interesting cataclysmic variables have been discovered as well.

Digitization of the FBS: Its Future Use and Expected Results

Abstract The First Byurakan Survey (FBS) is the largest spectral survey in the Northern sky. Its plates contain low-dispersion spectra for some 20,000,000 objects. The FBS spectra allow selection of objects by their color, broad emission or absorption lines, or SED; to discover, classify and investigate them. The FBS was conducted originally to search for UVX galaxies (1500 Markarian galaxies were discovered). Selection of blue stellar objects, red stars, and identification of IRAS sources have also been done by means of the FBS spectra. All these projects have been carried out by visual inspection of the plates. Digitization will give new possibilities to search for many new objects: new bright QSOs (m<18m), new Markarian (UVX) galaxies, BCDGs, optical counterparts of IR, radio, X-ray and other sources, late-type stars, planetary nebulae, emission-line stars, and white dwarfs; and to study star clusters and clusters of galaxies. The digitized FBS will be available via the Internet and on CDs. Software and an appropriate interface for working with the data will be provided.

Search for New Interesting Objects in the Second Part of the FBS

We present the results of a study of the FBS blue stellar objects with the goal of discovering new interesting objects. Forty-seven FBS objects have been observed with the Byurakan Observatory 2.6m telescope in 1987-1991 and scanned with the MAMA scanning machine at Observatoire de Paris in 1997-1999. 5 QSOs/Sy1s, 4 emission-line stars, five white dwarfs, and a number of continuous spectra objects (possible BL Lacs and DC white dwarfs) have been revealed.

Blue stellar objects of the first byurakan survey

Abstract The second part of the First Byurakan Survey is devoted to the search and investigation of blue stellar objects, hot subdwarfs, white dwarfs, HBB stars, cataclysmic variables, quasars, compact Seyfert galaxies. 1103 object were selected on a surface of 4009 square degrees at high Galactic latitudes, 716 of which are new. Many of these objects are being investigated with spectral and polarimetric methods, and photometric estimates of objects are being made. An analysis of the sample of blue stellar objects is made and subsamples of different types of objects within this sample are separated for further study.

New Evidence for Non-Cosmological Redshift

Recently Arp (1997) has published a list of x-ray emitting blue stellar objects (BSO) around 24 Seyfert galaxies. Herewith we present our optical identification of 5 BSOs in the field NGC3516 obtained on April 4-5, 1997 using the 2.16m telescope at Xinlong Station, Beijing Astronomical Observatory. One of the objects Q1107+7232 with z=2.10 (θ = 4.34′, θ is the angular distance from the center of NGC3516) is already listed in the Hewitt-Burbidge Catalog (1993). We find the other four objects are all quasars: Q1108+7226 with z=0.328 (θ = 11.23′); Q1106+7244, z=0.690 (θ = 10.23′); Q1105+7242, z=0.930, (θ = 10.990; QH05+7238, z=1.399 (θ = 7.42′) Q1107+7232, z=2.10 (θ = 4.34′)

Association of X-ray Quasars with Active Galaxies

Analysis of ROSAT observations demonstrate that X-ray sources are associated with bright Seyfert galaxies up to distances of about 40 arc min. These X-ray sources are predominantly identified with blue stellar objects (BSO's) some of which are already catalogued as quasars.The X-ray sources tend to pair and align across the nucleus of the active Seyfert. Enough redshifts are now available to indicate the similarities of the redshifts in the quasar pairs and to enable computation of ejection velocities of about 0.1c.

On the nature of the FBS blue stellar objects and the completeness of the Bright Quasar Survey

The second part of the First Byurakan Survey is aimed at detecting all bright (B<16.5) UV-excess starlike objects in a large area of the sky. By comparison with other major surveys such as the ROSAT All Sky Survey, the ROSAT WGACAT catalogue of point sources, the IRAS survey, the 6cm Green Bank, the 1.4GHz NRAO VLA and the 92cm Westerbork Northern sky surveys and with the catalogue of mean UBV data on stars, we estimate the number of AGNs present in the FBS survey and its completeness. We have made spectroscopic observations of nine of the most promising FBS candidates. We have found six new QSOs bringing the total number of known QSOs in this survey to 42. By comparison with the Bright Quasar Survey, we found that the completeness of this last survey is of the order of 70% rather than 30-50% as suggested by several authors.

Quasars around the Seyfert Galaxy NGC 3516

We report redshift measurements of five X-ray-emitting blue stellar objects located less than 12' from the X-ray Seyfert galaxy NGC 3516. We find these quasars to be distributed along the minor axis of the galaxy and to show a very good correlation between their redshift and their angular distance from NGC 3516. Moreover, the redshifts of these five quasars are 0.33, 0.69, 0.93, 1.40, and 2.10, which are very near the peaks of the redshift periodicity distribution (i.e., z = 0.3, 0.6, 0.96, 1.41, and 1.96). All these observed properties strikingly confirm, around this single example of a Seyfert, the composite picture derived from previous physical associations of quasars with low-redshift active galaxies.

The EC14026 Stars - Pulsating Hot Subdwarfs

The Edinburgh-Cape Blue Object Survey (Stobie et al. 1997a) is a southern hemisphere survey to discover hot, blue stellar objects brighter than B=18 at galactic latitudes more than 30° from the galactic plane. The main categories of object detected are hot subdwarfs, white dwarfs, blue horizontal branch stars, apparently normal B stars, cataclysmic variables and (stellar-like) active galactic nuclei. Over 50% of the EC Survey comprises hot subdwarfs.

Spectra of Two X-Ray–Emitting Quasi-Stellar Objects Apparently Ejected from the Seyfert Galaxy NGC 2639

This Letter presents the results of optical spectrophotometry of two blue stellar objects identified at the centers of two strong, compact X-ray sources located nearly symmetrically on either side of the LINER/Seyfert 2 galaxy NGC 2639 in the direction of its minor axis. The spectra presented here show that both are QSOs with remarkably similar spectra; the redshifts are, for NGC 2639 No. 8, z = 0.3048 ± 0.0012, and for NGC 2639 No. 3, z = 0.3232 ± 0.0004 (the former confirms an earlier identification and redshift measurement by Arp). Their location with respect to NGC 2639, the similarity of their optical spectra and redshifts, and their strong compact X-ray emission suggest that they are associated with NGC 2639, in line with the results of an analysis on ROSAT archival data in which an apparently statistically significant excess of strong compact X-ray sources has been found in the fields of X-ray-emitting Seyfert galaxies.

The Edinburgh-Cape Blue Object Survey -- I. Description of the survey

The Edinburgh-Cape Blue Object Survey is a major survey to discover blue stellar objects brighter than B ~ 18 in the southern sky. It is planned to cover an area of sky of 10 000 deg2 with ∣b∣ > 30° and δ < 0°. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy are being obtained with the SAAO telescopes to classify objects brighter than B = 16.5. This paper describes the survey, the techniques used to extract the blue stellar objects, the photometric methods and accuracy, the spectroscopic classification, and the limits and completeness of the survey.

First Byurakan Spectral Sky Survey. Blue stellar objects. XI. Region +80 ≤ δ ≤ +90°

The eleventh list of blue stellar objects in the second part of the First Byurakan Spectral Sky Survey (FBS) is presented. The list consists of 64 objects located in the region +80 ≤ δ ≤ +90° and 2h 08m ≤ a ≤ 20h 15m. The objects haveV magnitudes in the range 12.3–17.4 andB−V color indices in the range -0.55-+0.55. Of the 98 objects, 56 are newly discovered. Tentative classifications are given for 28 objects, of which there is one planetary nebula, 6 possible quasars, 15 possible white dwarfs, and 6 possible cataclysmic variables. Two of the latter are possibly novae having erupted at the epoch of exposure of the FBS plates in this region.

X-Ray Observations of Galaxy-Quasar Associations

Five examples of close associations of quasars with bright, low redshift galaxies have been observed in X-ray wavelengths with ROSAT. In three cases where the galaxies are detected strongly, the nuclei of the galaxies have X-ray extensions in the direction of the adjacent quasars.In all cases the active galaxies and quasars are located at the origin of apparent lines or pairs of X-ray sources, some involving filamentary X-ray connections to fainter quasars or candidate blue stellar objects. Brighter X-ray sources in these fields are found to be in excess of average survey values. The filaments and connections have measured fluxes of 1 ≲FX≲60 × 10−13erg cm−2s−1and they tend to radiate more strongly in the harder end of the 0.1-2.4 keV energy band.The most surprising result is the evidence that X-ray sources of optically diverse character are linked together in lines and extended filaments. Because of the rapid decay time of the high energy X-ray radiation, it is implied that we are observing some ongoing process possibly related to matter creation or emergence.

The first byurakan Spectral Sky Survey. Blue stellar objects. X. The zone+73°≤σ≤+80°

We present the tenth list of blue stellar objects of the second part of the First Byurakan Spectral Sky Survey (FBS). The list contains 100 objects in the region+73°≤σ≤+80° and3 h 30 m ≤α≤18 h 30 m encompassing an area of 355 square degrees. The objects have stellar V magnitude within the limits 12.0–18.5 and B-V colors between−0.77 and+0.37. Of these 100 objects, 80 were discovered for the first time. We give the equatorial coordinates, stellar V magnitude, color index CI, and preliminary classification of the objects on the basis of low-disperion prismatic spectra. For 29 objects we give approximate types, among which 4 are candidates for quasars, 2 for Seyfert galaxies, 1 for superassociation galaxy IC 381, 18 for white dwarfs, and 4 for cataclysmic variables.

The Edinburgh-Cape Blue Object Survey

AbstractThe Edinburgh-Cape Blue Object Survey is a major survey to discover blue stellar objects brighter than B ∼ 18 in the southern sky. It covers an area of sky of 10,000 square degrees with |b| &gt; 30° and δ &lt; 0°. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy are being obtained with the SAAO telescopes to classify objects brighter than B = 16.5. This paper describes the survey, the techniques used to extract the blue stellar objects, the photometric accuracy, and the completeness of the survey.