Search

Eclipsing Binaries (EBs) with one of the companions as very low mass stars (VLMS or M dwarfs) are testbeds to substantiate stellar models and evolutionary theories. Here, we present four EB candidates with F type primaries, namely, SAO 106989, HD 24465, EPIC 211682657 and HD 205403, identified from different photometry missions, SuperWasp, KELT, Kepler 2 (K2) and STEREO. Using the high-resolution spectrograph, PARAS, at the 1.2 m telescope at Mount Abu, Rajasthan, India, we hereby report the detection of four VLMS as companions to the four EBs. We performed spectroscopic analysis and found the companion masses to be $0.256\pm0.005$, $0.233\pm0.002$, $0.599\pm0.017$, and $0.406\pm0.005 M_{\odot}$ for SAO 106989, HD 24465, EPIC 211682657 and HD 205403 respectively. We determined orbital periods of $4.39790\pm0.00001$, $7.19635\pm0.00002$, $3.142023\pm0.000003$ and $2.444949\pm0.000001$~d and eccentricities of $0.248\pm0.005$, $0.208\pm0.002$, $0.0097\pm0.0008$ and $0.002\pm0.002$ for EBs SAO 106989, HD 24465, EPIC 211682657 and HD 205403 respectively. The radius derived by modeling the photometry data are $0.326\pm0.012~R_{\odot}$ for SAO 106989, $0.244\pm0.001 R_{\odot}$ for HD 24465, $0.566\pm0.005 R_{\odot}$ for EPIC 211682657, and $0.444\pm0.014 R_{\odot}$ for HD 205403. The radii of HD 24465B and EPIC 211682657B have been measured by precise KEPLER photometry and are consistent with theory within error bars. However, the radii of SAO 106989B and HD 205403B, measured by KELT and STEREO photometry, are $17-20\%$ higher than those predicted by theory. A brief comparison of the results of the current work is made with the M dwarfs already studied in literature., Comment: 27 pages, 7 figures, Accepted for publication in AJ

We report here strong evidence for a sub-Saturn around EPIC~211945201 and confirm its planetary nature. EPIC~211945201b was found to be a planetary candidate from {\it K2} photometry in Campaigns 5 \& 16, transiting a bright star ($V_{\rm mag}=10.15$, G0 spectral type) in a 19.492 day orbit. However, the photometric data combined with false positive probability calculations using VESPA was not sufficient to confirm the planetary scenario. Here we present high-resolution spectroscopic follow-up of the target using the PARAS spectrograph (19 radial velocity observations) over a time-baseline of 420 days. We conclusively rule out the possibility of an eclipsing binary system and confirm the 2-$\sigma$ detection of a sub-Saturn planet. The confirmed planet has a radius of 6.12$\pm0.1$$~R_{\oplus}$, and a mass of $27_{-12.6}^{+14}$~$M_{\oplus}$. We also place an upper limit on the mass (within the 3-$\sigma$ confidence interval) at 42~$M_{\oplus}$ above the nominal value. This results in the Saturn-like density of $0.65_{-0.30}^{+0.34}$ g~cm$^{-3}$. Based on the mass and radius, we provide a preliminary model-dependent estimate that the heavy element content is 60-70 \% of the total mass. This detection is important as it adds to a sparse catalog of confirmed exoplanets with masses between 10-70 $M_{\oplus}$ and radii between 4-8 $R_{\oplus}$, whose masses and radii are measured to a precision of 50\% or better (only 23 including this work)., Comment: Accepted for publication in The Astronomical Journal, 17 pages, 8 figures

We present here $Spitzer$ mid-infrared (IR) spectra and modeling of the spectral energy distribution (SED) of a selection of post-Asymptotic Giant Branch (PAGB) stars. The mid-IR spectra of majority of these sources showed spectral features such as polycyclic aromatic hydrocarbons (PAHs) and silicates in emission. Our results from SED modeling showed interesting trends of dependency between the photospheric and circumstellar parameters. A trend of dependency is also noticed between the ratios of equivalent widths (EWs) of various vibrational modes of PAHs and the photospheric temperature T$_{*}$ and model-derived stellar parameters for the sample stars. The PAGB mass loss rates derived from the SED models are found to be higher than those for the AGB stars. In a few objects, low and high excitation fine structure emission lines were identified, indicating their advanced stage of evolution. Further, IR vibration modes of fullerene (C$_{60}$) were detected for the first time in the PAGB star IRAS 21546+4721., Comment: 45 Pages, 24 figures, Accepted in MNRAS

The light emitted from the stellar photosphere serves as a unique signature for the nature of stars. The behaviour of these stellar lines depend upon the surface temperature, mass, evolutionary status and chemical composition of the star. With the advent of high-resolution spectrographs coupled with medium to large aperture telescopes around the globe, there is plenty of high-resolution and high signal-to-noise ratio data available to the astronomy community. Apart from radial velocity (RV) studies, such data offer us the unique opportunity to study chemical composition and atmospheric properties of the star. The procedure used to derive these parameters must be automated and well adaptable to data available from any high-resolution spectrograph. We hereby present an IDL code, PARAS SPEC, which was primary designed to handle high-resolution spectroscopy data from PARAS spectrograph coupled with the 1.2~m telescope at Mt. Abu, India. This code is designed to adapt with data from other spectrographs as well. The code PARAS SPEC estimates the stellar atmospheric parameters from the analysis of stellar spectra based on two primary methods, synthetic spectral fitting and equivalent width method. Synthetic spectral fitting method involves fitting of the observed spectrum with different synthetic spectra for a set of stellar parameters. The second method is based on equivalent widths (EWs) that are used to derive abundances for a set of Fe~I and Fe~II lines from the observed spectra. The detailed methodology used to design this code and comparison of the results from literature values are presented in this paper., Comment: 20 pages, To be submitted in MNRAS, Comments are welcome

PARAS is a fiber-fed stabilized high-resolution cross-dispersed echelle spectrograph, located on the 1.2 m telescope in Mt. Abu India. Designed for exoplanet detection, PARAS is capable of single-shot spectral coverage of 3800 - 9600 A, and currently achieving radial velocity (RV) precisions approaching ~1 m/s over several months using simultaneous ThAr calibration. As such, it is one of the few dedicated stabilized fiber-fed spectrographs on small (1-2 m) telescopes that are able to fill an important niche in RV follow-up and stellar characterization. The success of ground-based RV surveys is motivating the push into extreme precisions, with goals of ~10 cm/s in the optical and <1 m/s in the near-infrared (NIR). Lessons from existing instruments like PARAS are invaluable in informing hardware design, providing pipeline prototypes, and guiding scientific surveys. Here we present our current precision estimates of PARAS based on observations of bright RV standard stars, and describe the evolution of the data reduction and RV analysis pipeline as instrument characterization progresses and we gather longer baselines of data. Secondly, we discuss how our experience with PARAS is a critical component in the development of future cutting edge instruments like (1) the Habitable Zone Planet Finder (HPF), a NIR spectrograph optimized to look for planets around M dwarfs, scheduled to be commissioned on the Hobby Eberly Telescope in 2017, and (2) the NEID optical spectrograph, designed in response to the NN-EXPLORE call for an extreme precision Doppler spectrometer (EPDS) for the WIYN telescope. In anticipation of instruments like TESS and GAIA, the ground-based RV support system is being reinforced. We emphasize that instruments like PARAS will play an intrinsic role in providing both complementary follow-up and battlefront experience for these next generation of precision velocimeters., Comment: 9 pages, 6 figures, published in Proc. of SPIE Astronomical Telescopes + Instrumentation 2016

We report the detection of a very low mass star (VLMS) companion to the primary star 1SWASPJ234318.41+295556.5A (J2343+29A), using radial velocity (RV) measurements from the PARAS (PRL Advanced Radial-velocity Abu-sky Search) high resolution echelle spectrograph. The periodicity of the single-lined eclipsing binary (SB1) system, as determined from 20 sets of RV observations from PARAS and 6 supporting sets of observations from SOPHIE data, is found to be 16.953 d as against the 4.24 d period reported from SuperWasp photometry. It is likely that inadequate phase coverage of the transit with SuperWasp photometry led to the incorrect determination of the period for this system. We derive the spectral properties of the primary star from the observed stellar spectra: Teff = 5125 +/- 67 K, [Fe/H] = 0.1 +/- 0.14 and log g = 4.6 +/- 0.14, indicating a K1V primary. Applying the Torres relation to the derived stellar parameters, we estimate a primary mass 0.864 +/- 0.097 M_sun and a radius of 0.854 +/- 0.050 R_sun. We combine RV data with SuperWASP photometry to estimate the mass of the secondary, M_B = 0.098 +/- 0.007 M_sun, and its radius, R_B = 0.127 +/- 0.007 R_sun, with an accuracy of around 7%. Although the observed radius is found to be consistent with the Baraffe's theoretical models, the uncertainties on the mass and radius of the secondary reported here are model dependent and should be used with discretion. Here, we establish this system as a potential benchmark for the study of VLMS objects, worthy of both photometric follow-up and the investment of time on high-resolution spectrographs paired with large-aperture telescopes., Comment: Accepted for publication in MNRAS, 26 pages

We have carried out an extensive multi-wavelength study to investigate the star formation process in the S235 complex. The S235 complex has a sphere-like shell appearance at wavelengths longer than 2 $\mu$m and harbors an O9.5V type star approximately at its center. Near-infrared extinction map traces eight subregions (having A$_{V}$ $>$ 8 mag), and five of them appear to be distributed in an almost regularly spaced manner along the sphere-like shell surrounding the ionized emission. This picture is also supported by the integrated $^{12}$CO and $^{13}$CO intensity maps and by Bolocam 1.1 mm continuum emission. The position-velocity analysis of CO reveals an almost semi-ring like structure, suggesting an expanding H\,{\sc ii} region. We find that the Bolocam clump masses increase as we move away from the location of the ionizing star. This correlation is seen only for those clumps which are distributed near the edges of the shell. Photometric analysis reveals 435 young stellar objects (YSOs), 59\% of which are found in clusters. Six subregions (including five located near the edges of the shell) are very well correlated with the dust clumps, CO gas, and YSOs. The average values of Mach numbers derived using NH$_{3}$ data for three (East~1, East~2, and Central~E) out of these six subregions are 2.9, 2.3, and 2.9, indicating these subregions are supersonic. The molecular outflows are detected in these three subregions, further confirming the on-going star formation activity. Together, all these results are interpreted as observational evidence of positive feedback of a massive star., Comment: 28 pages, 15 figures, 3 tables, Accepted for publication in The Astrophysical Journal

We present an analysis of multi-wavelength observations from various datasets and Galactic plane surveys to study the star formation process in the W42 complex. A bipolar appearance of W42 complex is evident due to the ionizing feedback from the O5-O6 type star in a medium that is highly inhomogeneous. The VLT/NACO adaptive-optics K and L' images (resolutions ~0".2-0".1) resolved this ionizing source into multiple point-like sources below ~5000 AU scale. The position angle ~15 deg of W42 molecular cloud is consistent with the H-band starlight mean polarization angle which in turn is close to the Galactic magnetic field, suggesting the influence of Galactic field on the evolution of the W42 molecular cloud. Herschel sub-millimeter data analysis reveals three clumps located along the waist axis of the bipolar nebula, with the peak column densities of ~3-5 x10^{22} cm^{-2} corresponding to visual extinctions of AV ~32-53.5 mag. The Herschel temperature map traces a temperature gradient in W42, revealing regions of 20 K, 25 K, and 30-36 K. Herschel maps reveal embedded filaments (length ~1-3 pc) which appear to be radially pointed to the denser clump associated with the O5-O6 star, forming a hub-filament system. 512 candidate young stellar objects (YSOs) are identified in the complex, ~40% of which are present in clusters distributed mainly within the molecular cloud including the Herschel filaments. Our datasets suggest that the YSO clusters including the massive stars are located at the junction of the filaments, similar to those seen in Rosette Molecular Cloud., Comment: 27 pages, 16 figures, 1 table, Accepted for publication in The Astrophysical Journal

HD 213597 is an eclipsing binary system which was detected by the STEREO spacecraft and was speculated to host a low-mass stellar companion. We used high-resolution spectroscopy with the 10-m Hobby-Eberly Telescope and the 1.2-m telescope in Mt Abu for radial velocity (RV) measurements of this source. We performed aperture photometry for this star on the STEREO archival data and thereby confirm the transit signature. We also did follow-up ground-based photometry with a 10-inch telescope from Mt Abu. The spectroscopic RV semi-amplitude of the primary (33.39 km s^-1) indicates that the secondary is an M dwarf making the system a short period F+M eclipsing binary. These RVs along with the inclination derived from our combined photometric analysis (i=84.9 degree), enable us to estimate the mass of the secondary as M_B ~ 0.286 M_sun and radius as R_B ~ 0.344 R_sun using an estimated mass M_A ~ 1.3 M_sun and radius R_B ~ 1.97 R_sun of the primary. Our spectral analysis returned the following parameters: T_eff = 6625 +/-121 K, [Fe/H] = -0.095 +\-0.08 and log(g) = 3.72 +/-0.22 for the primary. When log(g) is constrained to a value of 3.96, we derive T_eff = 6753 +/-52 K and [Fe/H] = -0.025+\-0.05., Comment: 22 pages, 3 figures, Accepted for publication in MNRAS

We present spectrograph design details and initial radial velocity results from the PRL optical fiber-fed high-resolution cross-dispersed echelle spectrograph (PARAS), which has recently been commissioned at the Mt Abu 1.2 m telescope, in India. Data obtained as part of the post-commissioning tests with PARAS show velocity precision better than 2m/s over a period of several months on bright RV standard stars. For observations of sigma-Dra we report 1.7m/s precision for a period of seven months and 2.1m/s for HD 9407 over a period of 2 months. PARAS is capable of a single-shot spectral coverage of 3800A - 9500A at a resolution of about 67,000. The RV results were obtained between 3800A and 6900A using simultaneous wavelength calibration with a Thorium-Argon (ThAr) hollow cathode lamp. The spectrograph is maintained under stable conditions of temperature with a precision of 0.01 - 0.02C (rms) at 25.55C, and enclosed in a vacuum vessel at pressure of 0.1 +/-0.03 mbar. The blaze peak efficiency of the spectrograph between 5000A and 6500A, including the detector, is 30%; and about 25% with the fiber transmission. The total efficiency, including spectrograph, fiber transmission, focal ratio degradation (FRD), and telescope (with 81% reflectivity) is about 7% in the same wavelength region on a clear night with good seeing conditions., Comment: 33 pages, 15 figures, accepted for publication in PASP

We present results of Mt Abu JHK photometric and HI Brackett $\gamma$ line monitoring of the eruptive YSO V1647 Orionis (McNeil's Object) during the on-going outburst phase in 2008-2012. We discuss JHK colour patterns and extinction during the outburst and compare these with the previous outburst phase in 2004-05 and the intervening quiescent period of about 2 years. Commencing from early 2012, the object shows a slow fading out in all the bands. We report brightness variations in the nearby Herbig-Haro object HH22 possibly associated with those in V1647 Ori. We also present modelling of the spectral energy distributions of V1647 Ori during its recent outburst and quiescent phases. The physical parameters of the protostar and its circumstellar environment obtained from the modelling indicate marked differences in the two phases., Comment: 13 pages, 7 figures, Accepted for publication in Research in Astronomy and Astrophysics (RAA)

Mid-infrared (MIR) shells or bubbles around expanding H II regions have received much attention due to their ability to initiate a new generation of star formation. We present multi-wavelength observations around two bubbles associated with a southern massive star-forming (MSF) region G8.14+0.23, to investigate the triggered star formation signature on the edges of the bubbles by the expansion of the H II region. We have found observational signatures of the collected molecular and cold dust material along the bubbles and the 12CO(J=3-2) velocity map reveals that the molecular gas in the bubbles is physically associated around the G8.14+0.23 region. We have detected 244 young stellar objects (YSOs) in the region and about 37% of these YSOs occur in clusters. Interestingly, these YSO clusters are associated with the collected material on the edges of the bubbles. We have found good agreement between the dynamical age of the H II region and the kinematical time scale of bubbles (from the 12CO(J=3-2) line data) with the fragmentation time of the accumulated molecular materials to explain possible "collect-and-collapse" process around the G8.14+0.23 region. However, one can not entirely rule out the possibility of triggered star formation by compression of the pre-existing dense clumps by the shock wave. We have also found two massive embedded YSOs (about 10 and 22 Msolar) which are associated with the dense fragmented clump at the interface of the bubbles. We conclude that the expansion of the H II region is also leading to the formation of these two young massive embedded YSOs in the G8.14+0.23 region., Comment: 11 pages, 12 figures, 2 tables. Accepted for publication in The Astrophysical Journal

V1647 Ori is a young eruptive variable star, illuminating a reflection nebula (McNeil's Nebula). It underwent an outburst in 2003 before fading back to its pre-outburst brightness in 2006. In 2008, V1647 Ori underwent a new outburst. The observed properties of the 2003-2006 event are different in several respects from both the EXor and FUor type outbursts, and suggest that this star might represent a new class of eruptive young stars, younger and more deeply embedded than EXors, and exhibiting variations on shorter time scales than FUors. In outburst, the star lights up the otherwise invisible McNeil's nebular - a conical cloud likely accumulated from previous outbursts. We present follow-up photometric as well as optical and near-IR spectroscopy of the nebula obtainted during the 2008-2009 outburst. We will also present results from contemporaneous X-ray observations. These multi-wavelength observations of V1647 Ori, obtained at this key early stage of the outburst, provide a snapshot of the "lighting up" of the nebula, probe its evolution through the event, and enable comparison with the 2003-2006 outburst., Comment: 8 pages, 6 figures. Proceedings of the 16th Workshop on Cool Stars, Stellar Systems, and the Sun (PASP conference series, in press)

We present the {\it Spitzer}-IRAC images of the S235 star forming complex that includes the East~1 & 2, Central and S235 A & B regions. In addition, we present the near-infrared images of the S235 A & B regions. The IRAC photometry reveals on-going star formation, with 86 Class 0/I and 144 Class II YSOs in the entire S235 complex. Nearly 73% of these YSOs are present in clusters with a maximum surface density of 120 YSOs/pc$^{2}$ (in the vicinity of S235A & B regions). A few YSOs, possibly in an arc-like formation, are identified towards the south of S235A region, which may be speculated as an evidence for magnetically super-critical collapse. One of the sources in the arc-like formation, namely S235AB-MIR, seems to be a young, massive star that is still accreting matter. SED modeling of some of the newly identified YSOs confirms the classification made on the basis of IRAC colours. The IRAC ratio map of Ch2/Ch4 traces clearly the Br$\alpha$ emission associated with the HII region of S235A within the horse-shoe envelope. Outside the horse-shoe structure, the ratio map indicates shock-excited H$_{2}$ emission. Br$\alpha$ emission is also seen around S235B (from the ratio map). The ratio map of Ch2/Ch4 reveals that the source "e2s3" in the East~2 region may be associated with shock-excited H$_2$ emission outflow or jet. The SED modeling of this new source indicates that it is a very young massive star that is not yet able to drive an HII region., Comment: 19 pages; 13 figures; 8 tables. Accepted in MNRAS, Feb 2011

Spitzer IRAC images (3.6, 4.5, 5.8 and 8.0$\mu$m) and photometry of the star forming region M8 are presented. IRAC photometry reveals ongoing star formation in the M8 complex, with 64 Class 0/I and 168 Class II sources identified in several locations in the vicinity of sub-mm gas cores/clumps. Nearly 60% of these YSOs occur in about 7 small clusters. The spatial surface density of the clustered YSOs is determined to be about 10-20 YSOs/pc$^{2}$. Fresh star formation by the process of "collect and collapse" might have been triggered by the expanding HII regions and winds from massive stars. IRAC ratio images are generated and studied in order to identify possible diagnostic emission regions in M8. The image of 4.5$\mu$m/8.0$\mu$m reveals Br$\alpha$ counterpart of the optical Hourglass HII region, while the ratio 8.0$\mu$m/4.5$\mu$m indicates PAH emission in a cavity-like structure to the east of the Hourglass. The ratio maps of 3.6$\mu$m/4.5$\mu$m, 5.8$\mu$m/4.5$\mu$m and 8.0$\mu$m/4.5$\mu$m seem to identify PAH emission regions in the sharp ridges and filamentary structures seen East to West and NE to SW in M8 complex., Comment: 16 pages, 2 tables, 6 figures; Accepted for publication in MNRAS, May 2010

We present {\it Spitzer} IRAC mid-infrared photometry on the massive star forming region AFGL 437 (IRAS 03035+5819). From the IRAC colour-colour diagram, we identify several new embedded YSOs within 64 arcsec of the central compact cluster. Using the IRAC ratio images, we investigate the molecular outflows associated with the highly embedded young stellar object WK34 in the central cluster. We attribute the lobes seen (extended to $\sim$ 0.16 pc in the north) in the ratio map to shocked molecular hydrogen emission. IRAC images reveal a large diffuse nebulosity associated with the central cluster and extending up to $\sim$ 8.0 pc from south-west to north-east direction with its brightness gradually increasing from 3.6 to 8.0 $\mu$m. A dense box-car-shaped nebula (more than 2.0 pc in size) situated to the south-west of the cluster shows molecular hydrogen emission that may have been caused by shock waves from the compact cluster sources. It seems that these sources are also responsible for the infrared-bright nebulosity. Using a 2D radiative transfer model, we derive from the spectral energy distributions, the mass, age and luminosity of all the YSOs identified within the central cluster. The SED modelling shows that the driving engine of the outflows, WK34, appears to be massive but very young and deeply embedded. The weighted mean values of the masses and ages of the 21 YSOs derived from the model are in the range 1-10 \msun and 10$^{4.1 - 6.4}$ yr respectively; while their luminosities are in the range of 10$^{0.47-3.48}$ L$_{\odot}$., Comment: 11 pages, 6 figures, 2 tables; Accepted in MNRAS Main Journal, 2009; The article is proof-corrected version; also some numerical (sizes in arcsec/pc) corrections have been incorporated. The essential content and conlusions remain unchanged

IRAS 21413+5442 and IRAS 21407+5441 are two massive star forming regions of high luminosity, likely associated with each other. Near-infrared photometry on these two IRAS sources was performed at UKIRT using the UFTI under excellent seeing conditions yielding an angular resolution of $\sim$ 0.5 arcsec. Our results reveal details of stellar content to a completeness limit (90%) of J = 18.5, H = 18.0, and K = 17.5 mag in the two regions. In IRAS 21413+5442, we identify a late O type star, having large (H-K) color, to be near the centre of the CO jets observed by earlier authors. The UKIRT images reveal in IRAS 21407+5441, a faint but clear compact HII region around a central high - intermediate mass star cluster. We have detected a number of sources with large (H-K) color which are not detected in J band. We also present the GMRT radio continuum map at 1.28 GHz covering the entire region surrounding the two star forming clouds. The radio continuum fluxes are used to estimate the properties of HII regions which seem to support our near-IR photometric results. Based on our radio continuum map and the archival MSX 8.2 $\mu$m image, we show that the two IRAS sources likely belong to the same parent molecular cloud and conjecture that a high mass star of large IR colors, present in between the two sources, might have triggered star formation in this region. However one can not rule out the alternative possibility that Star A could be a nearby foreground star., Comment: 12 pages, 7 figures, accepted for publication in MNRAS

We present here near-infrared spectroscopy in the H and K bands of a selection of nearly 80 stars that belong to various AGB types, namely S type, M type and SR type. This sample also includes 16 Post-AGB (PAGB) stars. From these spectra, we seek correlations between the equivalent widths of some important spectral signatures and the infrared colors that are indicative of mass loss. Repeated spectroscopic observations were made on some PAGB stars to look for spectral variations. We also analyse archival SPITZER mid-infrared spectra on a few PAGB stars to identify spectral features due to PAH molecules providing confirmation of the advanced stage of their evolution. Further, we model the SEDs of the stars (compiled from archival data) and compare circumstellar dust parameters and mass loss rates in different types. Our near-infrared spectra show that in the case of M and S type stars, the equivalent widths of the CO(3-0) band are moderately correlated with infrared colors, suggesting a possible relationship with mass loss processes. A few PAGB stars revealed short term variability in their spectra, indicating episodic mass loss: the cooler stars showed in CO first overtone bands and the hotter ones showed in HI Brackett lines. Our spectra on IRAS 19399+2312 suggest that it is a transition object. From the SPITZER spectra, there seems to be a dependence between the spectral type of the PAGB stars and the strength of the PAH features. Modelling of SEDs showed among the M and PAGB stars that the higher the mass loss rates, the higher the [K-12] colour in our sample., Comment: 14 pages; accepted in MNRAS, 2008

We present a detailed study of the post-outburst phase of McNeil's nebula (V1647 Ori) using optical B,V,R,I and NIR J,H,K photometric and low resolution optical spectroscopic observations. The observations were carried out with the HFOSC, NIRCAM, TIRCAM and NICMOS cameras on the 2m HCT and 1.2m PRL telescopes during the period 2004 Feb-2005 Dec. The optical/NIR observations show a general decline in brightness of the exciting source of McNeil's nebula (V1647 Ori). Our recent optical images show that V1647 Ori has faded by more than 3 mags since Feb 2004. The optical/NIR photometric data also show a significant variation in the mags (Delta V = 0.78 mag, Delta R = 0.44 mag, Delta I = 0.21 mag, Delta J = 0.24 mag and Delta H = 0.20 mag) of V1647 Ori within a period of one month, which is possibly undergoing a phase similar to eruptive variables, like EXors or FUors. The optical spectra show a few features such as strong Halpha emission with blue-shifted absorption and the CaII IR triplet (8498A, 8542A and 8662A) in emission. As compared to the period just after outburst, there is a decrease in the depth and extent of the blue-shifted absorption component, indicating a weakening in the powerful stellar wind. The presence of the CaII IR triplet in emission confirms that V1647 Ori is a PMS star. The long-term, post-outburst photometric observations of V1647 Ori suggest an EXor, rather than an FUor event. An optical/IR comparison of the region surrounding McNeil's nebula shows that the optical nebula is more widely and predominantly extended to the north, whereas the IR nebula is relatively confined (dia ~ 60 arcsec), but definitely extended, to the south, too., Comment: 25 pages (4 figures in JPEG format), Accepted for the publication in MNRAS. Preprint is also available at: http://www.tifr.res.in/~ojha/McNeil.html

We conducted a multi-wavelength campaign in September-October, 2002, to observe SS 433. We used 45 meter sized 30 dishes of Giant Meter Radio Telescope (GMRT) for radio observation, 1.2 meter Physical Research Laboratory Infra-red telescope at Mt Abu for IR, 1 meter Telescope at the State Observatory, Nainital for Optical photometry, 2.3 meter optical telescope at the Vainu Bappu observatory for spectrum and Rossi X-ray Timing Explorer (RXTE) Target of Opportunity (TOO) observation for X-ray observations. We find sharp variations in intensity in time-scales of a few minutes in X-rays, IR and radio wavelengths. Differential photometry at the IR observation clearly indicated significant intrinsic variations in short time scales of minutes throughout the campaign. Combining results of these wavelengths, we find a signature of delay of about two days between IR and Radio. The X-ray spectrum yielded double Fe line profiles which corresponded to red and blue components of the relativistic jet. We also present the broadband spectrum averaged over the campaign duration., Comment: 17 pages 10 figures MNRAS (submitted)

We report the photometric evidence of bullet like features in SS433 in X-rays, Infra-red and Radio bands through a multi-wavelength campaign., Comment: 4 pages, 2 figures To be published in the Proceedings of 10th Marcel Grossman Meeting, Ed. R. Ruffini et al. (World Scientific: Singapore)

SS433 is well-known for its precessing twin jets having optical bullets inferred through {\it spectroscopic} observation of $H_\alpha$ lines. Recently, Chakrabarti et al. (2002) described processes which may be operating in accretion disk of SS433 to produce these bullets. In a recent multi-wavelength campaign, we find sharp rise in intensity in time-scales of few minutes in X-rays, IR and radio waves through {\it photometric} studies. We interpret them to be possible evidence of ejection of bullet-like features from accretion disks., Comment: 9 latex pages with five figures

We report detection of a Young Stellar Object with an evidence for an outflow in the form of knots in the molecular hydrogen emission line (2.121 micron) towards the massive star forming region IRAS 06061+2151. Near-infrared images reveal IRAS 06061+2151 to be a cluster of at least five sources, four of which seem to be early B type young stellar objects, in a region of 12 arcsec surrounded by a nebulosity. The presence of the knots that are probably similar to the HH objects in the optical wavelengths, suggests emerging jets from one of the cluster members. These jets appear to excite a pair of knot-like objects (Knot-NW and Knot-SE) and extend over a projected size of 0.5pc. The driving source for the jets is traced back to a member of the cluster whose position in the H-Ks/J-H color-color diagram indicates that it is a Class 1 type pre-mainsequence star. We also obtained K band spectra of the brightest source in the cluster and of the nearby nebular matter. The spectra show molecular hydrogen emission lines but do not show Brackett gamma line at 2.167 micron. These spectra suggest that the excitation of the molecular hydrogen lines is probably due to a mild shock., Comment: Only the paper format style is changed in the revised version due to error in ps/pdf file generation, the paper content is not changed; submitted to A&A

Near-infrared photometry and narrow/broad-band imaging of the massive and luminous young stellar object IRAS 05361+3539 are presented. Imaging observations were made at Mt. Abu while the photometric data were taken from the 2MASS. From the color-color and color-magnitude diagrams, we identified several sources of faint Class II type and about six Class I type in the parent molecular cloud complex. The IRAS 05361+3539 itself was seen to be a Class I object and our images in Br$\gamma$ and H$_{2}$ lines show jets/outflows from this object. The jet/outflow matches with the axis of CO outflow detected earlier. The near-infrared and the IRAS far-infrared flux distribution suggests a possible accretion disk with dust temperatures between 80 to 800K and extent of several tens to hundreds of AU. A possible FU Orionis type of source was detected in the cluster., Comment: 7 pages (in A&A main journal format), 5 figures, accepted for publication in the A&A main journal

We report the detection of the H2 v=1-0 S(1) line at 2.122um, from RNO91 in the L43 dark cloud, which is known to be a T Tauri star surrounded by a 1700AU disk structure (containing ices) and a weak outflow. The non-detection of the H2 v=2-1 S(1) line at 2.247um suggests shock excitation rather than fluorescence. The emission is extended spatially up to 9arcsec in the north-south direction. The line intensity peak (FWHM 3arcsec) corresponds to the star RNO91 which is embedded in a cocoon of gas and dust. The observed H2 emission from this cocoon may be attributed to embedded Herbig-Haro like knots. The H2 line flux in the central 2"X3"is estimated to be 7X10^{-14} ergs/sec/cm^{2}, which indicates a mass flow rate of 4X10^{-8} M_{sun}/yr. Furthermore, narrow band image taken through H2 1-0 S(1) filter is presented, which reveal a tilted disk and bipolar outflow structure that agrees with earlier observations and models. We show that this disk/outflow system is a unique case., Comment: 4 pages, 3 figures, use A&A style files

This report describes a joint X ray/ultraviolet/ground based study of the abnormal Be star lambda Eri which has previously shown evidence of X ray flaring from Rosat observations in 1991. The 1991 flare event caught the astronomical hot star community by surprise because x ray flares have not been observed from other single B-type stars, before or since. Both optical (H-alpha) and UV/Voyager observations provide evidence for transient heating events near the surface of lambda Eri.