Optical spectrum of the infrared source IRAS 20004+2955 (V1027 Cyg)

Based on high-dispersion echelle spectra taken with the 6-m Special Astrophysical Observatory telescope, we study the IR source IRAS 20004+2955 identified with the variable star V1027 Cyg. We have determined the star’s fundamental parameters (T _eff=5000 K, logg=1.0), metallicity ([Fe/H]=?0.2 dex), and atmospheric abundances of 16 elements. Its metallicity, carbon underabundance, and slight overabundance of the heavy elements Zr, Y, Ce, and Eu suggest that V1027 Cyg belongs to the Galactic disk population.     

Nonstationarity of hot post-AGB objects: Variations of the brightness and spectrum of IRAS 01005+7910, IRAS 22023+5249, and IRAS 22495+5134

UBV photometry for two hot protoplanetary nebula candidates, early B supergiants with emission lines in the spectrum, IRAS 01005+7910 and IRAS 22023+5249, as well as for IRAS 22495+5134, the central star of the young compact planetary nebula M 2–54, is presented for the first time. Fast irregular brightness variations of the stars with maximum amplitudes up to and color-brightness correlations have been found: the B - V colors tend to become redder with increasing brightness, while U - B more likely decrease with brightening. The color excesses E(B - V) have been determined. The equivalent widths and absolute intensities of emission lines have been derived from low-resolution spectroscopy. Spectral variability has been revealed in all objects. The parameters of the gaseous nebula have been calculated for M 2–54: N _e ～ 10⁴ cm^?3and T _e = 7700 ± 200 K. A joint analysis of the photometric and spectroscopic data suggests that stellar wind variations can be one of the causes of the stellar variability. The luminosities and distances of all three objects have been estimated.     

Photometric variability and spectrum of the post-AGB candidate IRAS 19200+3457

We present our photoelectric and spectroscopic observations of the early B supergiant with an IR excess IRAS 19200+3457, a poorly known post-AGB candidate. The star has been found to be photometrically variable. We observed rapid irregular brightness variations with amplitudes up to \(\Delta V = 0\mathop .\limits^m 4, \Delta B = 0\mathop .\limits^m 4\), and \(\Delta U = 0\mathop .\limits^m 5\). IRAS 19200+3457 and three other hot post-AGB stars—V886 Her, V1853 Cyg, and LSIV—12°111—exhibit a similar variability pattern. Our low-resolution spectroscopic observations in the period 2001–2003 show that the spectrum of IRAS 19200+3457 represents an early B star with hydrogen emission lines originating from a circumstellar gaseous envelope. The HeI λ5876 Å, λ6678 Å, λ7065 Å, and OI λ7774 Å lines are in absorption. The hydrogen and, probably, HeI lines proved to be variable. Our observations confirm the conclusion that IRAS 19200+3457 belongs to the class of intermediate-mass protoplanetary objects.     

Identification of infrared sources in the IRAS circulars

From IRAS (Infrared Astronomical Satellite) Circulars Nos. 4 to 15, 110 infrared sources have been identified. Out of these 110 identified sources 99 are galaxies, nine are nebulae, one is a dark object, and one is a non-stellar object. Thirty-five of these galaxies, have already been studied, mostly are spiral type. The characteristics of sixty-four remaining galaxies, for which the type is not known or uncertain, are studied by compairing their colours and luminosities with known galaxies. The galaxies observed by IRAS are mostly active galaxies.     

Interstellar and circumstellar medium in the direction to IR source IRAS 01005+7910

Using the high-resolution spectra obtained at the 6-meter telescope of the SAO RAS over 2002–2013, we studied the spectral features of the lines of interstellar medium. The radial velocities of the Na I 5890 Å, Na I 5896 Å, Ca II 3934 Å and Ca II 3968 Å absorption lines were analyzed. Seven diffuse interstellar bands 4964, 5780, 5797, 6196, 6203, 6379 Å were identified in the optical spectrum of IRAS01005+7910. Radial velocities V_r and equivalent widths W_λ of these DIBs were measured, for which the values of the interstellar reddening E_B?V and column density of neutral hydrogen log [N(H)] were calculated.     

Optical Classification of IRAS Post-AGB Candidates

We present the first results of a survey carried out on a sample of optically bright post-AGB candidates selected from the IRAS Point Source Catalogue, many of them previously unidentified in the literature. The selection criteria are based on their characteristic far infrared colours. Low resolution spectroscopy of more than 150 sources has been obtained during 6 years. Our preliminary analysis confirms that most of the candidates observed are true post-AGB stars, some of them still strongly reddened. Some young planetary nebulae, a few young stellar objects and active galactic nuclei are also present in the sample. The distribution of post-AGB stars with different spectral types in the IRAS two-colour diagram and its evolutionary implications are briefly discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Search for the near infrared counterparts to the IRAS sources

As part of a program to search for the near infrared counterparts to the far infrared sources discovered by the Infrared Astronomical Satellite (IRAS) we have scanned two areas including the IRAS error boxes for the sources IRAS 0453+444 and IRAS 1717-087 at 2.2 m down to the flux density limit of 1 Jy. Results on the IRAS sources and the detection of two new bright near infrared sources are reported and discussed.     

Dry polysaccharides and the infrared spectrum of OH 26.5+0.6

The spectrum of the infrared source OH 26.5+0.6 over the waveband 2–40 m is interpreted on the basis of a model involving emission and absorption of radiation by anhydrous cellulose grains.     

Optical variability of the radio source Z0524+03

The results of photometric observations of the optical component of the known variable radio source Z0524+03 are reported. The light variations amounted to 1.5 ^m during the period from January 21, 1998 to January 28, 2001 and occurred synchronously in the BVRI bands on time scales ranging from several years to 0.05 days. The spectral index of the object (S ～ ν ^α) varied from ?2.4 to ?1.3 from minimum to maximum light.Polarimetric observations made on January 22/23, 1999 showed that the linear polarization of the radiation of the object did not exceed 1% at the time of observation.Three local-standard candidates have been selected in the field of the object.     

About the nature of IRAS 19075+0921

We use infrared data to further investigate the nature of IRAS 19075+0921. Our results indicate that IRAS 19075+0921 is heavily obscured by its thick, circumstellar envelope and possibly composed of two infrared sources all with late spectral types so that it presents a dual chemistry nature.     

Further observations of IRAS 04302+2247

We present near-infrared broad-band and H₂ images of the quadrupolar source IRAS 04302+2247. High-resolution data at 3.8 μm show that the circumstellar envelope has a high degree of axisymmetry: the asymmetry at shorter wavelengths is almost certainly the result of extinction by dust in the cavity. Photometry of the flux peaks confirms that the source is variable but little change in appearance is observed between 1995 November and 1997 September. We report the first clear detection of the molecular outflow in H₂ at 2.1 μm, revealing discrete streams which are inclined to the axis of the cavity. The motion of knots in the outflow remains the most likely cause of the variability.     

The near-infrared variable source IRAS 04000+5052 is a small, compact star forming region

The near-infrared variable source, IRAS 04000+5052, was observed using the Italian 1.5 m TIRGO infrared telescope, located in the Gornergrat Observatory, Switzerland. High-resolution images were obtained in the JHK broad bands and H₂ S(1) 1-0, Br_γ narrow bands. Photometry and astrometry were also carried out. From the observations, it is found that IRAS source is not a single young object, but a small-sized, compact star-forming region with many young objects. Even in such a small and compact region, stars are not formed at the same time.     

Optical Identification of IRAS Point Sources. Galaxies. X

The tenth list of objects from the BIG (Byurakan-IRAS Galaxies) sample, containing 104 galaxies identified with 60 point sources from the IRAS PSC catalog, is introduced. The identifications have been made in the region +69°+73° and 09^h50^m15^h20^m with an area of 107 sq.deg. The identified objects include 13 Sy candidates, 5 compact star-formation galaxies, 11 interacting pairs (including 5 merger candidates) and 1 interacting triple system, 5 LSB galaxies, and 5 groups. 21 objects are also identified with radio sources. The optical coordinates, their deviations from the IR coordinates, V stellar magnitudes, morphological types, angular sizes of the central regions, and position angles have been determined. The identified galaxies are of Sa-Sc, SB, and Irr morphological types, the optical stellar magnitudes lie in the range 15^m.0-21^m.5, and the angular sizes of the central regions lie in the range 3-32. Finding charts from the DSS2 are included for these objects.     

Optical Identifications of IRAS Point Sources. Galaxies. VIII

A list of objects of the BIG (Byurakan-IRAS galaxies) sample is given: 89 galaxies identified with 55 point sources from the IRAS Point Source Catalog. The identifications were based on the Digital Sky Survey (DSS), the First Byurakan Survey, blue and red maps of the Palomar Observatory Sky Survey, and infrared fluxes at wavelengths of 12, 25, 60, and 100 mm in the region of +61° +65° and 05^h30^m 18^h 00^m with an area of 340 deg² (additional IR sources were identified). The optical coordinates of the identified galaxies, their departure from the IR coordinates, the V stellar magnitude, morphological type, angular size, and position angle were determined. The objects have optical magnitudes in the range of 12 ^m .5 - 21 ^m .5 and angular sizes in the range of 3 - 43. Finder charts for these objects from the DSS are given.     

Optical Identifications of IRAS Point Sources. Galaxies. VII

A seventh list of objects from the BIG (Byurakan-IRAS galaxies) sample is given: 95 galaxies identified with 63 point sources from the IRAS Point Source Catalog. The identifications were based on the Digital Sky Survey (DSS), the First Byurakan Survey, blue and red maps from the Palomar Observatory Sky Survey, and infrared fluxes at 12, 25, 60, and 100 m in the region of +65° 69° and 14^h00^m 18^h05^m with an area of 96 deg². For the identified galaxies the optical coordinates, their departures from the IR coordinates, the stellar V magnitudes, morphological types, angular sizes, and position angles were determined. The objects have optical magnitudes in the range of 13 ^m .8-21 ^m .5 and angular sizes in the range of 4-38. Finder charts from the DSS are given for these objects.     

The structure of the IRAS05168+3634 star-forming region

Astrophysics and Space Science - Radioactive components of the interstellar medium provide an entirely-different and new aspect to the studies of the interstellar medium. Injected from sources of...     

Optical Identification of IRAS Point Sources. Galaxies. IX

The ninth list of objects from the BIG (Byurakan-IRAS Galaxies) sample is presented; 87 galaxies are identified with 60 point sources from the IRAS PSC catalog in the region +69° +73° and 03^h50^m 09^h50^m with an area of 117 deg². Most of the identified galaxies are compact with bright bulges and faint peripheries. The identified objects include 7 Sy candidates, 8 interacting pairs (of which one is a merger candidate), and 6 LSB galaxies. The optical coordinates and their deviations from the IR coordinates, the V magnitudes, morphological types, angular dimensions, and position angles are given. The identified galaxies are of morphological types Sa-Sc and have optical stellar magnitudes in the range 15.5^m-21.5^m with angular sizes in the range 3-26. Finding charts from DSS2 are provided for these objects.