Star formation region in Vela

A star formation region connected with SNO 41 is investigated. The observations of this region were carried out in the ¹²CO (1-0) line and in the 1.2-mm (with SIMBA) with the 15-m SEST mm telescope (Cerro La Silla, Chile). A blue shifted outflow is revealed from the ¹²CO(1-0) observations, while a bipolar outflow is apparent from the 1.2-mm SIMBA image. In CO it seems that a very faint dust envelope around SNO 41 probably exists, which is expanding with a velocity of ∼10.5 km/s. The distance to SNO 41 is estimated as ∼1500 pc. There are outflows also present in 2MASS images. A spiral jet has a condensation (resembling a HH object) at the end. Another jet has a discontinuity and a bow-shock-like structure on it. In 2MASS images there are also spots resembling HH objects. In this region there is also a rather luminous point source (IRAS 08546-4254), which has IR colors typical for an YSO connected with a water maser. The detection of a strong CS (2-1) line emission toward IRAS 08546-4254, with the same velocity as the CO line, shows the existence of a high density core of molecular gas associated to this source. A methanol maser is also associated with that IRAS source. The existence of CS line emission and a methanol maser (at 6.669 Ghz) is an indication of the presence of a very young massive star. It is not excluded that this IRAS source is the center of outflows mentioned above, because this source coincides with the center of the 1.2-mm SIMBA image and also with the place of origin of the jet with bow-shock-like structure. Published in Astrofizika, Vol. 50, No. 1, pp. 5–15 (February 2007).     

Southern YSO GRV10 and its environment

In this paper the southern cometary nebula GRV10 and its environment are investigated. The object is connected with a molecular cloud (its dimensions are ~4 pc). 12CO (1-0) observations toward GRV10 revealed the presence of two molecular outflows (a bipolar outflow), a red and a blue-shifted outflow, which coincide in position, indicating that they are moving along the line of sight in opposite directions. Near GRV10 a bright IR star, GRV10 IR, is discovered (near the southern edge of the nebula) and since its spectra and near IR colors favor it to be a Mira type star, a distance of ~4.4 kpc can be estimated. Star GRV10 IR appears connected with the IRAS point source IRAS 10406-6256. The grouping of stars (YSOs - young stellar objects) connected with GRV10 and embedded in a dark nebulosity is also discussed. This grouping is associated with the IRAS point source IRAS 10406-6253, which has FIR colors typical for embedded, not evolved, YSOs.     

Star-forming region BBW 36 in puppis

Recent studies of the star formation region BBW 36 and associated molecular clouds are presented. The ¹²CO (1-0) observations, carried out with the 15-m SEST (Swedish-ESO) telescope (Cerro La Silla, Chile), revealed the existence of cloud a, connected with BBW 36 and of cloud b, having elongation in SE-NW direction. A red-shifted molecular outflow with velocity ∼+5 km/s (with respect to cloud a), having a direction parallel to the line of sight, was also observed. VLA observations showed the presence of a source VLA 2 at 3.6 cm with an elongation in the N-S direction. It is suggested that the VLA 2 source coincides with a dust disc (surrounding the object BBW 36). The star 3, which is one of the YSOs in the star-forming region BBW 36 and is connected with a bright comma-like nebula, can be the source of the molecular outflow. The star 3 has very high IR colors and is associated with an IRAS point source IRAS 07280-1829, which has IR colors, typical for an IRAS point source, connected with a water maser. On the 2MASS K image of BBW 36 we can see the existence of a bright nebula; a group of stars is embedded in that nebula, and among these stars there are stars with dust discs (or envelopes). On the 2MASS K image several spiral jets are also present, some of them with a condensation at the end. Published in Astrofizika, Vol. 51, No. 3, pp. 469–477 (August 2008).     

Investigation of the conspicuous infrared star cluster and star-forming region “RCW 38 IR Cluster”

The infrared star cluster RCW 38 IR Cluster, which is also a massive star-forming region, is investigated. The results of observations with the SEST (Cerro La Silla, Chile) telescope on the 2.6-mm ¹²CO spectral line and with SIMBA on the 1.2-mm continuum are given. The ¹²CO observations revealed the existence of several molecular clouds, two of which (clouds 1 and 2) are connected with the object RCW 38 IR Cluster. Cloud 1 is a massive cloud, which has a depression in which the investigated object is embedded. It is not excluded that the depression was formed by the wind and/or emission from the young bright stars belonging to the star cluster. Rotation of cloud 2, around the axis having SE-NW direction, with an angular velocity ω = 4.6 · 10⁻¹⁴ s⁻¹ is also found. A red-shifted outflow with velocity ∼+5.6 km/s, in the SE direction and perpendicular to the elongation of cloud 2 has also been found. The investigated cluster is associated with an IR point source IRAS 08573-4718, which has IR colors typical for a non-evolved embedded (in the cloud) stellar object. The cluster is also connected with a water maser. The SIMBA image shows the existence of a central bright condensation, coinciding with the cluster itself, and two extensions. One of these extensions (the one with SW-NE direction) coincides, both in place and shape, with cloud 2, so that the possibility that this extension might also be rotating like cloud 2 is not excluded. In the vicinity of these extensions there are condensations resembling HH objects. Published in Astrofizika, Vol. 51, No. 1, pp. 29–40 (February 2008).     

Is IRAS 03134 + 5958 a Herbig-Haro object?

The source IRAS 03134 + 5958 identified by Iyengar & Verma (1984) on the Palomar Observatory Sky Survey (POSS) prints with a nonstellar optical object with [P – R]≃ 5.3 ± 1.5 is near the edge of Lynds dark cloud No. 1384 and is either embedded in or behind the cloud. The galactic latitude of this source (b ^II = 2‡.3), its positionvis-a-vis the Lynds dark cloud, its nonstellar appearance, high [P – R] colour and its far-infrared spectrum, all suggest the possibility of its being a Herbig-Haro (HH) object. To test this possibility we undertook measurements of its proper motion and variability (two of the characteristic properties of HH objects). These yield μ_a = (3.6 ± 2.3) arcsec/century and μ_δ= (−1.2 ± 2.0) arcsec/century for its proper motion. The source reveals large variation in brightness between 1950 and 1954. Optical line studies of the source are required to confirm its classification as an HH object.     

A Collimated Stellar Wind Emanating from a Massive Protostar

We report multi-wavelength observations towards IRAS 16547–4247, a luminous infrared source with a bolometric luminosity of 6.2 × 10⁴ L _⊙. Dust continuum observations at 1.2-mm indicate that this object is associated with a dust cloud with a size of about 0.4 pc in diameter and a mass of about 1.3 × 10³ M _⊙. Radio continuum observations show the presence of a triple radio source consisting of a compact central object and two outer lobes, separated by about 0.3 pc, symmetrically located from the central source. Molecular hydrogen line observations show a chain of knots that trace a collimated flow extending over 1.5 pc. We suggest that IRAS 16547–4247 corresponds to a dense massive core which hosts near its central region a high-mass star in an early stage of evolution. This massive YSO is undergoing the ejection of a collimated stellar wind which drives the H₂ flow. The radio emission from the lobes arises in shocks resulting from the interaction of the collimated wind with the surrounding medium. We conclude that the thermal jets found in the formation of low-mass stars are also produced in high-mass stars.     

The H2O maser toward IRAS 06308+0402

We present the monitoring results for the H₂O maser toward the infrared source IRAS 06308+0402 associated with a dense cold molecular cloud. The observations were carried out with the 22-m radio telescope at the Pushchino Radio Astronomy Observatory (Russia) during 1992–2003. The H₂O maser was discovered in May 1992 (Pashchenko 1992) during a survey of IRAS sources associated with dense cold clouds with bipolar molecular outflows. The H₂O spectrum contains many emission features, suggesting the fragmentation of the envelope around a young star. The star has a low peculiar velocity relative to the CO molecular cloud (～2.2 km s^?1). We found a cyclic variability of the total maser flux with a period from 1.8 to 3.1 yr.     

Pulsations and long-term photometric variability of three candidates for protoplanetary nebulae

We present new photometric data and analyze long-term UBV observations of three candidates for protoplanetary nebulae—F supergiants with infrared excesses at high Galactic latitudes—IRAS 18095+2704, IRAS 19386+0155, and IRAS 19500-1709. All these stars exhibit quasi-periodic low-amplitude variations caused by pulsations against the background of long-term brightness trends. For IRAS 18095+2704=V887 Her, we have found a pulsation period of 109 days and revealed a linear brightness trend—the star brightens at constant (within the limits of the measurement errors) yearly mean color indices. The light curve of IRAS 19386+0155=V1648 Aql in 2000–2008 is represented by a wave with a fundamental period of 102 days whose modulation with a close period of 98 days leads to variations with a variable amplitude. V1648 Aql also shows a systematic rise in V brightness along with a reddening. IRAS 19500–1709=V5112 Sgr exhibits irregular pulsations with periods of 39 and 47 days. The long-term variability component of V5112 Sgr may indicate that the star is binary.     

Understanding the spectral energy distributions of the galactic star forming regions IRAS 18314-0720, 18355-0532 and 18316-0602

Embedded Young Stellar Objects (YSO) in dense interstellar clouds are treated self-consistently to understand their spectral energy distributions (SED). Radiative transfer calculations in spherical geometry involving the dust as well as the gas component, have been carried out to explain observations covering a wide spectral range encompassing near-infrared to radio continuum wavelengths. Various geometric and physical details of the YSOs are determined from this modelling scheme. In order to assess the effectiveness of this self-consistent scheme, three young Galactic star forming regions associated with IRAS 18314-0720, 18355-0532 and 18316-0602 have been modelled as test cases. They cover a large range of luminosity (≈ 40). The modelling of their SEDs has led to information about various details of these sources, e.g. embedded energy source, cloud structure and size, density distribution, composition and abundance of dust grains etc. In all three cases, the best fit model corresponds to the uniform density distribution. Two types of dust have been considered, viz., Draine & Lee (DL) and the Mezger, Mathis & Panagia (MMP). Models with MMP type dust explain the dust continuum and radio continuum emission from IRAS 18314-0720 and 18355-0532 self-consistently. These models predict much lower intensities for the fine structure lines of ionized heavy elements, than those observed for IRAS 18314-0720 and 18355-0532. This discrepancy has been resolved by invoking clumpiness in the interstellar medium. For IRAS 18316-0602, the model with DL type dust grains is preferred.     

Star formation in L 1199

Lynds 1199 is an extended dark cloud of moderate opacity in the upper Cepheus region. The B3V type star HD206135 illuminating the reflection nebula DG 175 is associated with this cloud. In this paper the nature of the cloud and its associated young stellar objects is studied on the basis of¹³CO data obtained with the 4 m millimeter wave telescope of Nagoya University, photographic observations taken with the 60/90 cm Schmidt telescope of Konkoly Observatory, as well as IRAS data.     

Large-scale mapping of the IRAS 0042 + 5530 region in the 12CO (J = 1−0) and 13CO (J = 1−0) molecular lines

We present new radio observations of molecular lines in the region of high mass star formation, namely G122.0-7.1. A large-scale map of the emission observed in the ¹²CO (J = 1−0) and ¹³CO (J = 1−0) lines covers the area of 15′ × 9′, revealing two dense regions. The molecular bipolar outflows have been resolved in ASO1 region. It is associated with the known candidate YSO nearby IRAS 0042 + 5530. Also, a new dense region has been discovered in the North-Western part of the G122.0-7.1 at a distance of 5′ from IRAS 0042 + 5530. Its position is close to the peak of 4850 MHz emission. The text was submitted by the authors in English.     

Photometric study of the FUor star V 1735 Cyg (Elias 1-12)

Results from optical photometric observations of the PMS star V 1735 Cyg are reported. The star is located in the IC 5146 dark cloud complex—a region of active star formation. On the basis of observed outburst and spectral properties, V 1735 Cyg was classified as a FUor object. We present data from BVRI CCD photometric observations of the star, collected from March 2003 to January 2009. Plates from the Rozhen Schmidt telescope archive were scanned for a brightness estimation of the star. A sequence of sixteen comparison stars in the field of V 1735 Cyg was calibrated in BVRI bands. The data from photographic observations made from 1986 to 1992 show a strong light variability (ΔV=1_⋅^m2). In contrast, the recent photometric data obtained from 2003 to 2009 show only small amplitude variations (ΔI=0_⋅^m3). The analysis of existing photometric data shows a very slow decrease in star brightness—1_⋅^m8 (R) for a 44 year period. The possibilities for future photometric investigations of V 1735 Cyg using the photographical plate archives is discussed briefly.     

Note on a remarkable object close to the star LSS 3027

The star LSS 3027, embedded in a parabolic-shaped dark nebula, and several stars in its vicinity, were observed photometrically and spectroscopically to investigate whether they are candidates of very young Herbig Ae/Be stars. Only the star LSS 3027B is without doubt a very good candidate. Its H-emission is very strong, indicating an extended atmosphere around the star, and its near- and far-infrared spectral energy distributions exhibit a strong excess radiation, which most probably is caused by a thick dust shell in the close environment of the star. The ratio of total to selective extinction is found to be equal toR-5.1. It can be shown that it is embedded in the dark cloud mentioned above. From its properties we believe that the remarkable object LSS 3027B is a typical Hergig Be pre-Main-Sequence object.Based on data obtained at the ESO, La Silla, Chile and with the Infrared Astronomical Satellite (IRAS).     

First Byurakan Spectral Sky Survey. Stars of late spectral types. −11° ≤ δ ≤ −7° belt

A 10th list of late-type M and C stars found on plates of the First Byurakan Spectral Sky Survey in the − 11° ≤ δ ≤ − 7° belt with an area of about 1070 deg² is given. The list contains data on 169 red stars, 117 of which were found for the first time: 8 are new C stars, 3 are Cstar candidates, 104 are M stars, 1 is either an M or an S star, and 1 object on the survey plate cannot be classified. Of the 117 objects, 47 are unidentified IRAS sources. A statistical analysis of the objects that are and are not identified with IRAS sources shows that the identified stars are, with a high probability, brighter and have relatively more massive envelopes. Two stars were found to have fairly large brightness variability (with an amplitude of at least 6^m.O). Gasdust shells are assumed to exist around nine of the IRAS sources. The equatorial coordinates, spectral types, and stellar magnitudes, determined on Palomar E maps, are given for the selected objects. Translated from Astrofizika, Vol. 41. No. 4, pp. 545–559, October–December, 1998.     

A red giant with a strange star as its core. Principal similarities to and differences from Thorne-Zytkow objects

A model red giant with a mass of 5 M_⊙ a luminosity of 41,740 L_⊙, and a radius of 960 R_⊙ and with a strange quark star as its core is constructed, and it is compared with a Thorne-Zytkow object having similar integrated parameters. The difference in internal structure is manifested right at the dense core: matter above the core is held off only by γ rays from the strange star, and convection is maintained down to the strange star. The lifetime of a red giant containing a strange star turns out to be almost 500 times shorter than that of a Thorne-Zytkow object — on the order of 10⁵ years. Translated from Astrofizika, Vol. 41. No. 4, pp. 533–544, October–December, 1998.     

A Study of Star Formation in BRC18

Using the 13.7m radio telescope at Delingha, the millimeter-wave radio observatory of Purple Mountain Observatory, we made mapping observations in 12CO J = 1 - 0 line towards IRAS 05417+0907, located in the bright-rimmed cloud (BRC) BRC18. We used a 7 × 7 grid with 1' spacing, a finer and larger grid than the one used by Myers et al. Our results show that there is a bipolar outflow near IRAS 05417+0907. Combining with the observations at other wave bands, we find that the star formation process in this region is triggered by radiation-driven implosion. The significant difference between the masses of BRC18 and the cores and the relatively large ratio of associated source bolometric luminosity to the mass show that the star formation in BRC18 may be taking place in a sequence.     

Infrared companions to pre-main sequence stars

Summary We report 1.2, 1.6, 2.2 and 3.6 μm slit scan observations of the young low-luminosity stars Elias 22 (also known as GSS 31) in the Rho Ophiuchus dark cloud and Glass I in the Chamaeleon dark cloud. We discovered an infrared companion to Elias 22 at a projected separation of 2.0 arcsec (320 AU) and an optical/infrared companion to Glass I at a projected separation of 2.9 arcsec (410 AU). The companion of Elias 22 is a very cool optically almost invisible object (∼1000 K) less luminous than the primary, while the companion to Glass I is an optically visible late-type star with an infrared excess so large that it is actually bolometrically brighter than the primary. In both cases the infrared excess is likely to be due to hot circumstellar dust grains heated by a central young star (much more obscured in the case of Elias 22 than in the case of Glass I). We outline a new method to determine the mass ratio of such systems assuming that both components lie on an isochrone in the H-R diagram. If the companions are in a bound orbit, the estimated specific angular momentum exceeds or is of the order of 10²¹ cm² s⁻¹, only one order of magnitude larger than that of the Sun-Jupiter system. Based on observations collected at the European Southern Observatory at La Silla, Chile.     

Spectral and morphological studies of an “infrared” nebula in the region of Cyg OB7

Spectral and morphological studies of an infrared nebula in the neighborhood of Cyg OB7 discovered in 2007 are reported. It is shown that over the last several years the brightness and shape of the nebula have changed significantly. Spectral observations of the nebula made with the 2.6-m telescope at the Byurakan Observatory in 2004 and 2005 reveal the existence of a faint trace of continuum spectrum, indicating the existence of a star inside the dark cloud. Classification of these spectra shows that over one year the star’s spectral class changed from late G to early K. It is also shown that the absorption in the direction of the nebula is as high as 8^m–10^m. __________ Translated from Astrofizika, Vol. 50, No. 1, pp. 17–27 (February 2007).     

Searches for HH objects and emission stars in star formation regions. V. Two new cometary nebulae in Perseus

A small region surrounding the emission star LkHα 326 in the Perseus dark cloud is studied in the optical range. Two new cometary nebulae are described and their relationship to the Herbig-Haro objects in this region is examined. An HH-jet is discovered near the central star of one of these nebulae. Six emission stars, of which four are new, are detected by slitless spectroscopy. __________ Translated from Astrofizika, Vol. 51, No. 2, pp. 219–228 (May 2008).     

Star formation in the starburst cluster in NGC 3603

We have used new, deep, visible and near infrared observations of the compact starburst cluster in the giant HII region NGC 3603 and its surroundings with the WFC3 on HST and HAWK-I on the VLT to study in detail the physical properties of its intermediate mass (∼1–3 M_⊙) stellar population. We show that after correction for differential extinction and actively accreting stars, and the study of field star contamination, strong evidence remains for a continuous spread in the ages of pre-main sequence stars in the range ∼2 to ∼30 Myr within the temporal resolution available. Existing differences among presently available theoretical models account for the largest possible variation in shape of the measured age histograms within these limits. We also find that this isochronal age spread in the near infrared and visible Colour-Magnitude Diagrams cannot be reproduced by any other presently known source of astrophysical or instrumental scatter that could mimic the luminosity spread seen in our observations except, possibly, episodic accretion. The measured age spread and the stellar spatial distribution in the cluster are consistent with the hypothesis that star formation started at least 20–30 Myrs ago progressing slowly but continuously up to at least a few million years ago. All the stars in the considered mass range are distributed in a flattened oblate spheroidal pattern with the major axis oriented in an approximate South-East–North-West direction, and with the length of the equatorial axis decreasing with increasing age. This asymmetry is most likely due to the fact that star formation occurred along a filament of gas and dust in the natal molecular cloud oriented locally in this direction.