New surveys of UBV photometry and absolute proper motions at intermediate latitude

A photometric and proper motion survey has been obtained in 2 directions at intermediate latitude: ($l=167.5^\circ$, $b=47.4^\circ$; $\alpha_{2000}=9^h41^m26^s$,$\delta_{2000}=+49^\circ53'27''$) and ($l=278^\circ$, $b=47^\circ$; $\alpha_{2000}=11^h42^m56^s$, $\delta_{2000}=-12^\circ31'42''$). The survey covers 7.13 and 20.84 square degrees, respectively. The limiting magnitude is about 18.5 in V for both directions. We have derived the density laws for stars (M$_{V}$ $\ge$ 3.5) as a function of distance from the galactic plane. The density laws for stars follow a sum of two exponentials with scale heights of 240 pc (thin disk) and 790 pc (thick disk), respectively. The local density of thick disk is found to be 6.1$\pm$3 % relative to the thin disk. The kinematical distribution of stars has been probed to distances up to 3.5 kpc above the galactic plane. New estimates of the parameters of velocity ellipsoid have been derived for the thick disk of the Galaxy. A comparison of our data sets with the Besan\c con model star count predictions has been performed, giving a good agreement in the magnitude range V = 13 to 18.Comment: 13 pages, 8 PS figures, To appear in A&

On the shell star pleione (BU Tauri)

BU Tauri (Pleione) an interesting star in the Pleiades cluster, has been observed spectrophotometrically. The energy distribution curves of the star have been discussed vis a vis model atmospheres for normal stars in the appropriate range of temperature and effective gravity. The changes in the energy distribution curve noticed during our observations and previous observations taken from the literature have been pointed out. On the basis of the measured Há emission equivalent width, a rough estimate of the dimensions of the extended envelope of the star has been made

The ionizing sources of luminous compact HII regions in the RCW106 and RCW122 clouds

Given the rarity of young O star candidates, compact HII regions embedded in dense molecular cores continue to serve as potential sites to peer into the details of high-mass star formation. To uncover the ionizing sources of the most luminous and compact HII regions embedded in the RCW106 and RCW122 giant molecular clouds, known to be relatively nearby (2-4 kpc) and isolated, thus providing an opportunity to examine spatial scales of a few hundred to a thousand AU in size. High spatial resolution (0.3"), mid-infrared spectra (R=350), including the fine structure lines [ArIII] and [NeII], were obtained for four luminous compact HII regions, embedded inside the dense cores within the RCW106 and RCW122 molecular cloud complexes. At this resolution, these targets reveal point-like sources surrounded by nebulosity of different morphologies, uncovering details at spatial dimensions of <1000AU. The point-like sources display [ArIII] and [NeII] lines - the ratios of which are used to estimate the temperature of the embedded sources. The derived temperatures are indicative of mid-late O type objects for all the sources with [ArIII] emission. Previously known characteristics of these targets from the literature, including evidence of disk or accretion suggest that the identified sources may grow more to become early-type O stars by the end of the star formation process

Spectrophotometry observations of HR 8107

HR 8107, a reported new Be star, has been observed spectrophotometrically. The energy distribution curve of the star has been compared with those of other stars of similar spectral and luminosity types and model atmospheres. On the basis of comparison with model atmospheres an effective temperature has been assigned to the star

Study of the filamentary infrared dark cloud G192.76+00.10 in the S254-S258 OB complex

We present results of a high resolution study of the filamentary infrared dark cloud G192.76+00.10 in the S254-S258 OB complex in several molecular species tracing different physical conditions. These include three isotopologues of carbon monoxide (CO), ammonia (NH$_3$), carbon monosulfide (CS). The aim of this work is to study the general structure and kinematics of the filamentary cloud, its fragmentation and physical parameters. The gas temperature is derived from the NH$_3$ $(J,K) = (1,1), (2,2)$ and $^{12}$CO(2--1) lines and the $^{13}$CO(1--0), $^{13}$CO(2--1) emission is used to investigate the overall gas distribution and kinematics. Several dense clumps are identified from the CS(2--1) data. Values of the gas temperature lie in the ranges $10-35$ K, column density $N(\mathrm{H}_2)$ reaches the value 5.1 10$^{22}$ cm$^{-2}$. The width of the filament is of order 1 pc. The masses of the dense clumps range from $\sim 30$ M$_\odot$ to $\sim 160$ M$_\odot$. They appear to be gravitationally unstable. The molecular emission shows a gas dynamical coherence along the filament. The velocity pattern may indicate longitudinal collapse.Comment: 10 pages, 9 figures, accepted for publication in Research in Astronomy and Astrophysic

A Multicolor Survey of Absolute Proper Motions : Galactic Structure and Kinematics in the Direction of Galactic Center at Intermediate Latitude

We have derived a new photographic photometry and proper motions for 20000 stars with completeness to V = 18 in the direction of galactic center at the intermediate latitude (l = 3 deg,b = 47 deg; alpha(1950)=15h 18m, delta(1950) = +02deg 16') for a 15.5 sq deg field. The combination of four glass copies of the Palomar Observatory Sky Survey (i.e. POSS 1402 E&O and POSS 1429 E&O) has been used as a first epoch for proper motion determination. The random error of the proper motions is approximately 0.''3/cen to V=17. The photometric accuracy ranges between 0.07 to 0.10 in the V, B and U bands. We stress the importance of the magnitude and color effects in astrometric surveys of field stars. Using color-magnitude diagrams of a few cluster member stars, a new distance of 6.9+-0.5 kpc is derived for M5 and 20.3+-0.8 kpc for Pal 5 globular clusters. This is in good agreement with other determinations. We have analyzed the components of U+W and V galactic space motions resulting from the accurate proper motions survey. No dependence with z distance is found in the asymmetric drift of the thick disk population. New estimates of the parameters of the velocity ellipsoid have been derived for the thin disk, thick disk and halo populations of the Galaxy.Comment: PS file, 15 pages, 13 figures (available on request), paper accepted for publication in Astron. & Astrophy

Young Stellar Population of the Bright-Rimmed Clouds BRC 5, BRC 7 and BRC 39

Bright-rimmed clouds (BRCs), illuminated and shaped by nearby OB stars, are potential sites of recent/ongoing star formation. Here we present an optical and infrared photometric study of three BRCs: BRC 5, BRC 7 and BRC 39 to obtain a census of the young stellar population, thereby inferring the star formation scenario, in these regions. In each BRC, the Class I sources are found to be located mostly near the bright rim or inside the cloud, whereas the Class II sources are preferentially outside, with younger sources closer to the rim. This provides strong support to sequential star formation triggered by radiation driven implosion due to the UV radiation. Moreover, each BRC contains a small group of young stars being revealed at its head, as the next-generation stars. In particular, the young stars at the heads of BRC 5 and BRC 7 are found to be intermediate/high mass stars, which, under proper conditions, may themselves trigger further star birth, thereby propagating star formation out to long distances.Comment: 30 pages, 7 Figures, 6 Tables, accepted for publication in Monthly Notices of the Royal Astronomical Societ