Multi-epoch infrared photometry of the star forming region G173.58+2.45

We present a multi-epoch infrared photometric study of the intermediate-mass star forming region G173.58+2.45. Photometric observations are obtained using the near-infrared $JHKL'M'$ filters and narrow-band filters centered at the wavelengths of H$_2$ (1-0) S(1) (2.122 $\mu$m) and [FeII] (1.644 $\mu$m) lines. The H$_2$ image shows molecular emission from shocked gas, implying the presence of multiple star formation and associated outflow activity. We see evidence for several collimated outflows. The most extended jet is at least 0.25 pc in length and has a collimation factor of $\sim$ 10, which may be associated with a binary system within the central cluster, resolved for the first time here. This outflow is found to be episodic; probably occurring or getting enhanced during the periastron passage of the binary. We also find that the variable star in the vicinity of the outflow source, which was known as a FU Ori type star, is probably not a FU Ori object. However, it does drive a spectacular outflow and the variability is likely to be related to accretion, when large clouds of gas and dust spiral in towards the central source. Many other convincing accretion-outflow systems and YSO candidates are discovered in the field.Comment: 15 pages, 9 figures, accepted for publication in MNRA

L & M band infrared studies of V4332 Sagittarii - detection of the water-ice absorption band at 3.05 microns and the CO fundamental band in emission

L and M band observations of the nova-like variable V4332 Sgr are presented. Two significant results are obtained viz. the unusual detection of water ice at 3.05 microns and the fundamental band of 12CO at 4.67 microns in emission. The ice feature is a first detection in a nova-like variable while the CO emission is rarely seen in novae. These results, when considered together with other existing data, imply that V4332 Sgr could be a young object surrounded by a circumstellar disc containing gas, dust and ice. The reason for a nova-like outburst to occur in such a system is unclear. But since planets are believed to form in such disks, it appears plausible that the enigmatic outburst of V4332 Sgr could be due to a planetary infall. We also give a more reliable estimate for an epoch of dust formation around V4332 Sgr which appears to have taken place rather late in 1999 - nearly five years after its outburst.Comment: 10 pages, 3 figures (to appear in ApJ(Letters), 2004

Remarkable changes in the near-infrared spectrum of the nova-like variable V4332 Sgr

We report on recent near-IR observations of V4332 Sgr - the nova-like variable that erupted in 1994. Its rapid, post-outburst evolution to a cool M type giant/supergiant, soon after its outburst, had showed that it was an unusual object differing from other eruptive variables like classical/symbiotic novae or born-again AGB stars. The present study of V4332 Sgr was motivated by the keen interest in the recent eruption of V838 Mon - which along with V4332 Sgr - is believed to belong to a new class of objects (we propose they may be called "quasi-novae"). Our observations show new developments in the evolution of V4332 Sgr. The most striking feature is the detection of several molecular bands of AlO - a rarely seen molecule in astronomical spectra - in the JHK spectra. Many of these bands are being detected for the first time. The only other detection of some of these AlO bands are in V838 Mon, thereby showing further spectral similarities between the two objects. JHK photometry shows the development of a new dust shell around V4332 Sgr with a temperature of ~ 900K. This dust shell does not appear to be associated with ejecta of the 1994 outburst but is due to a second mass-loss episode which is not expected in a classical nova outburst. The cold molecular environment, suggested by the AlO emission, is also not expected in novae ejecta. We model the AlO bands and also discuss the possible formation mechanism of the AlO.Comment: To appear in Ap.J(L), 3 figure

Optical/IR studies of Be stars in NGC 6834 with emphasis on two specific stars

We present optical and infrared photometric and spectroscopic studies of two Be stars in the 70--80-Myr-old open cluster NGC 6834. NGC 6834(1) has been reported as a binary from speckle interferometric studies whereas NGC 6834(2) may possibly be a gamma Cas-like variable. Infrared photometry and spectroscopy from the United Kingdom Infrared Telescope (UKIRT), and optical data from various facilities are combined with archival data to understand the nature of these candidates. High signal-to-noise near-IR spectra obtained from UKIRT have enabled us to study the optical depth effects in the hydrogen emission lines of these stars. We have explored the spectral classification scheme based on the intensity of emission lines in the $H$ and $K$ bands and contrasted it with the conventional classification based on the intensity of hydrogen and helium absorption lines. This work also presents hitherto unavailable UBV CCD photometry of NGC 6834, from which the evolutionary state of the Be stars is identified.Comment: Published in Research in Astronomy and Astrophysics, RAA 14 (2014) 1173-1192, 20 pages, 10 figure

UKIRT Widefield Infrared Survey for Fe+

The United Kingdom Infrared Telescope (UKIRT)Widefield Infrared Survey for Fe+ (UWIFE) is a 180 deg2 imaging survey of the first Galactic quadrant (7° < l < 62° |b| <1°.5) that uses a narrow-band filter centred on the [Fe II] 1.644-μm emission line. The [Fe II] 1.644-μm emission is a good tracer of dense, shock-excited gas, and the survey will probe violent environments around stars: star-forming regions, evolved stars, and supernova remnants, among others. The UWIFE survey is designed to complement the existing UKIRTW idefield Infrared Survey for H2 (UWISH2). The survey will also complement existing broad-band surveys. The observed images have a nominal 5Ï? detection limit of 18.7 mag for point sources, with a median seeing of 0.83 arcsec. For extended sources, we estimate a surface brightness limit of 8.1 Ã? 10-20 W m-2 arcsec-2. In this paper, we present an overview and some preliminary results of this survey. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

A search for radioactive 26Al in the nova-like variable V4332 Sagittarii

We have searched for the important radioactive isotope 26Al in the nova-like source V4332 Sgr. Recent results from gamma ray astronomy show that there is pervasive emission of the 1.809 MeV gamma ray photon, arising from the decay of 26Al to 26Mg, from all over the galactic plane. Though the sites from where this emission originates are not clearly established, novae are believed to be an important contributing source. In this context, V4332 Sgr presented a rare opportunity to observationally investigate whether novae or novae-like sources synthesize 26Al and to what extent. Strong AlO bands in the near-IR have been reported in this object recently. As molecular bands of different isotopic compositions are readily resolved spectroscopically (e.g. 12CO and 13CO), it was thought that the components of AlO associated with 26Al and stable 27Al could be detected as separate bands. Our spectra indicate that there is no strong presence of 26Al in V4332 Sgr. A reliable upper limit of 0.10 for the 26Al/27Al ratio is determined which constitutes the first observational constraint for this ratio in a potential 26Al producing source. While V4332 Sgr is not a typical nova, its outburst amplitude and light-curve behaviour bear close similarity to that of novae. Hence, although the results from V4332 Sgr cannot be directly extended to novae in general, the limit on the observed 26Al/27Al ratio could be a useful input in constraining rather uncertain nucleosynthesis models for the production of 26Al in novae/novae-like sources. By comparing the observed 26Al/27Al ratio in V4332 Sgr with that expected in classical novae it appears unlikely that the progenitor of V4332 Sgr is an Oxygen-Neon-Magnesium white dwarf.Comment: 9 pages, 2 figures, to appear in Ap.J(L) July 200

A near IR imaging survey of intermediate and high-mass young stellar outflow candidates

We have carried out a near-infrared imaging survey of luminous young stellar outflow candidates using the United Kingdom Infrared Telescope. Observations were obtained in the broad band K (2.2 mu) and through narrow band filters at the wavelengths of H_2 v=1--0 S(1) (2.1218 mu) and Br gamma (2.166 mu) lines. Fifty regions were imaged with a field of view of 2.2 X 2.2 arcmin^2. Several young embedded clusters are unveiled in our near-infrared images. 76% of the objects exhibit H_2 emission and 50% or more of the objects exhibit aligned H_2 emission features suggesting collimated outflows, many of which are new detections. These observations suggest that disk accretion is probably the leading mechanism in the formation of stars, at least up to late O spectral types. The young stellar objects responsible for many of these outflows are positively identified in our images based on their locations with respect to the outflow lobes, 2MASS colours and association with MSX, IRAS, millimetre and radio sources. The close association of molecular outflows detected in CO with the H_2 emission features produced by shock excitation by jets from the young stellar objects suggests that the outflows from these objects are jet-driven. Towards strong radio emitting sources, H_2 jets were either not detected or were weak when detected, implying that most of the accretion happens in the pre-UCHII phase; accretion and outflows are probably weak when the YSO has advanced to its UCHII stage.Comment: 64 pages, 53 figures, Accepted for publication in the MNRA

Near IR Spectroscopic monitoring of WR 140 during the 2001 periastron passage

We present new spectra of WR 140 (HD 193793) in the JHK bands with some covering the 1.083-micron He I emission line at higher resolution, observed between 2000 October and 2003 May to cover its 2001 periastron passage. The WC7 + O4-5 spectroscopic binary WR 140 is the prototype of colliding-wind, episodic dust-making Wolf-Rayet systems which also show strong variations in radio and X-ray emission. The JHK spectra showed changes in continuum and in the equivalent widths of the WC emission lines, consistent with formation of dust starting between 2001 January 3 and March 26 (orbital phases 0.989 and 0.017) and its subsequent fading and cooling. The 1.083-micron He I line has a P-Cygni profile which showed variations in both absorption and emission components as WR 140 went through periastron passage. The variation of the absorption component yielded tight constraints on the geometry of the wind-collision region, giving theta = 50 +/- 8 degrees for the opening semi-angle of the interaction `cone', indicating a wind-momentum ratio of the O to the WR star=0.1, about three times larger than previously believed. As the system approached periastron, the emission component showed the appearance of a significant sub-peak, movement of which across the profile was seen to be consistent with its formation in wind material flowing along the contact discontinuity between the two stellar winds and the changing orientation of the colliding wind region. The flux carried in the sub-peak exceeded the X-ray fluxes measured at previous periastron passages. This additional source of radiative cooling of the shock-heated gas probably causes it to depart from being adiabatic around periastron passage, thereby accounting for the departure of the X-ray flux from its previously expected $1/d$-dependency.Comment: Accepted for publication in MNRAS - 13 Pages, 10 figure