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In the episodic accretion scenario, a large fraction of the protostellar mass accretes during repeated and large bursts of accretion. Since outbursts on protostars are typically identified at specific wavelengths, interpreting these outbursts requires converting this change in flux to a change in total luminosity. The Class I young stellar object EC 53 in the Serpens Main cloud has undergone repeated increases in brightness at 850 $\mu$m that are likely caused by bursts of accretion. In this study, we perform two- and three-dimensional continuum radiative transfer modeling to quantify the internal luminosity rise in EC 53 that corresponds to the factor of $\sim$1.5 enhancement in flux at 850 $\mu$m. We model the spectral energy distribution and radial intensity profile in both the quiescent and outburst phases. The internal luminosity in the outburst phase is $\sim 3.3$ times brighter than the luminosity in the quiescent phase. The radial intensity profile analysis demonstrates that the detected sub-mm flux variation of EC 53 comes from the heated envelope by the accretion burst. We also find that the role of external heating of the EC 53 envelope by the interstellar radiation field is insignificant., Comment: 16 pages, 14 figures, Accepted for publication in ApJ

We report a historic K s -band light curve spanning over three decades of the FUor PGIR20dci recently discovered by Hillenbrand et al. We find some minor variability of the object prior to the FUor outburst, an initial rather slow rise in brightness, followed in 2019 by a much steeper rise to the maximum.

While young stellar objects sometimes undergo bursts of accretion, these bursts usually occur sporadically, making them challenging to study observationally and to explain theoretically. We build a schematic description of cyclical bursts of the young stellar object EC 53 using near-IR and sub-mm monitoring obtained over six cycles, each lasting $\approx530$ days. EC 53 brightens over $0.12$ yr by $0.3$ mag at 850 $\mu$m, $2$ mag at 3.35 $\mu$m, and $1.5$ mag at near-IR wavelengths, to a maximum luminosity consistent with an accretion rate of $\sim8\times10^{-6}$ M$_\odot$ yr$^{-1}$. The emission then decays with an e-folding timescale of $\approx0.74$ yr until the accretion rate is $\sim1\times10^{-6}$ M$_\odot$ yr$^{-1}$. The next eruption then occurs, likely triggered by the buildup of $\sim5\times10^{-6}$ M$_\odot$ of mass in the inner disk, enough that it becomes unstable and drains onto the star. Just before outburst, when the disk is almost replenished, the near-IR colors become redder, indicating an increase in the geometrical height of the disk by this mass buildup. The reddening disappears soon after the initial burst, as much of the mass is drained from the disk. We quantify physical parameters related to the accretion process in EC 53 by assuming an $\alpha$-disk formulation, constrained by the observed disk properties and accretion rate. While we can only speculate about the possible trigger for these faithful eruptions, we hope that our quantified schematic will motivate theorists to test the hypothesized mechanisms that could cause the cyclical buildup and draining of mass in the inner disk., Comment: Accepted for publication in the Astrophysical Journal

We report photometry and spectroscopy of the outburst of the young stellar object Gaia19bey. We have established the outburst light curve with archival Gaia G, ATLAS Orange, ZTF r-band and Pan-STARRS rizy-filter photometry, showing an outburst of approximately 4 years duration, longer than typical EXors but shorter than FUors. Its pre-outburst SED shows a flat far-infrared spectrum, confirming the early evolutionary state of Gaia19bey and its similarity to other deeply embedded young stars experiencing outbursts. A lower limit to the peak outburst luminosity is approximately 182 L_sun at an assumed distance of 1.4 kpc, the minimum plausible distance. Infrared and optical spectroscopy near maximum light showed an emission line spectrum, including HI lines, strong red CaII emission, other metal emission lines, infrared CO bandhead emission, and a strong infrared continuum. Towards the end of the outburst, the emission lines have all but disappeared and the spectrum has changed into an almost pure continuum spectrum. This indicates a cessation of magnetospheric accretion activity. The near-infrared colors have become redder as Gaia19bey has faded, indicating a cooling of the continuum component. Near the end of the outburst, the only remaining strong emission lines are forbidden shock-excited emission lines. Adaptive optics integral field spectroscopy shows the H_2 1--0 S(1) emission with the morphology of an outflow cavity and the extended emission in the [FeII] line at 1644 nm with the morphology of an edge-on disk. However, we do not detect any large-scale jet from Gaia19bey., Comment: Accepted for publication in The Astronomical Journal

The United Kingdom Infrared Telescope (UKIRT) observatory has been transferred to the ownership of the University of Hawaii (UH) and is now being managed by UH. We have established partnerships with several organizations to utilize the UKIRT for science projects and to support its operation. Our main partners are the U.S. Naval Observatory (USNO), the East Asian Observatory (EAO), and the UKIRT microlensing team (JPL/IPAC/OSU/Vanderbilt). The USNO is working on deep northern hemisphere surveys in the H and K bands and the UKIRT microlensing team is running a monitoring campaign of the Galactic bulge. EAO, UH, and USNO have individual P.I. research programs. Most of the observations are using the Wide Field Camera (WFCAM), but the older suite of cassegrain instruments are still fully operational. Data processing and archiving continue to be done CASU and WSA in the UK. We are working on a concept to upgrade the WFCAM with new larger infrared detector arrays for substantially improved survey efficiency.

Massive stars are rarely seen to form in isolation. It has been proposed that association with companions or clusters in the formative stages is vital to their mass accumulation. In this paper we study IRAS~18144-1723, a massive young stellar object (YSO) which had been perceived in early studies as a single source. In the CO(3-2) line, we detect an outflow aligned well with the outflow seen in H$_2$ in this region. We show that there are at least two YSOs here, and that the outflow is most likely to be from a deeply embedded source detected in our infrared imaging. Using multi-wavelength observations, we study the outflow and the embedded source and derive their properties. We conclude that IRAS~18144 hosts an isolated cloud, in which at least two massive YSOs are being born. From our sub-mm observations, we derive the mass of the cloud and the core hosting the YSOs., Comment: 14 pages, 14 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society

Very few low-ionization broad absorption line (LoBAL) QSOs have been found at high redshifts to date. One high-redshift LoBAL QSO, J0122+1216, was recently discovered at the Lijiang 2.4-m Telescope with an initial redshift determination of 4.76. Aiming to investigate its physical properties, we carried out follow-up observations in the optical and near-IR spectroscopy. Near-IR spectra from UKIRT and P200 confirms that it is a LoBAL, with a new redshift determination of $4.82\pm0.01$ based on the \mgii~ emission-line. The new \mgii~ redshift determination reveals strong blueshifts and asymmetry of the high-ionization emission lines. We estimated a black hole mass of $\sim 2.3\times 10^9 M_\odot$ and Eddington ratio of $\sim 1.0$ according to the empirical \mgii-based single-epoch relation and bolometric correction factor. It is possible that strong outflows are the result of an extreme quasar environment driven by the high Eddington ratio. A lower limit on the outflowing kinetic power ($>0.9\% L_{Edd}$) was derived from both emission and absorption lines, indicating these outflows play a significant role in the feedback process to regulate the growth of its black hole as well as host galaxy evolution., 12 pages, 10 figures. Accepted for publication in The Astrophysical Journal

This paper defines the UK Infra-Red Telescope (UKIRT) Hemisphere Survey (UHS) and release of the remaining ~12,700 sq.deg of J-band survey data products. The UHS will provide continuous J and K-band coverage in the northern hemisphere from a declination of 0 deg to 60 deg by combining the existing Large Area Survey, Galactic Plane Survey and Galactic Clusters Survey conducted under the UKIRT Infra-red Deep Sky Survey (UKIDSS) programme with this new additional area not covered by UKIDSS. The released data includes J-band imaging and source catalogues over the new area, which, together with UKIDSS, completes the J-band UHS coverage over the full ~17,900 sq.deg area. 98 per cent of the data in this release have passed quality control criteria, the remaining 2 per cent being scheduled for re-observation. The median 5-sigma point source sensitivity of the released data is 19.6 mag (Vega). The median full width at half-maximum of the point spread function across the dataset is 0.75 arcsec. In this paper, we outline the survey management, data acquisition, processing and calibration, quality control and archiving as well as summarising the characteristics of the released data products. The data are initially available to a limited consortium with a world-wide release scheduled for August 2018., Comment: 14 pages, 9 figures, MNRAS in press. v2 includes some changes suggested by referee

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., Published in Research in Astronomy and Astrophysics, RAA 14 (2014) 1173-1192, 20 pages, 10 figures

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.

We present high-resolution infrared (2--18 micron) images of the archetypal periodic dust-making Wolf-Rayet binary system WR140 (HD 193793) taken between 2001 and 2005, and multi-colour (J -- [19.5]) photometry observed between 1989 and 2001. The images resolve the dust cloud formed by WR140 in 2001, allowing us to track its expansion and cooling, while the photometry allows tracking the average temperature and total mass of the dust. The combination of the two datasets constrains the optical properties of the dust. The most persistent dust features, two concentrations at the ends of a `bar' of emission to the south of the star, were observed to move with constant proper motions of 324+/-8 and 243+/-7 mas/y. Longer wavelength (4.68-micron and 12.5-micron) images shows dust emission from the corresponding features from the previous (1993) periastron passage and dust-formation episode. A third persistent dust concentration to the east of the binary (the `arm') was found to have a proper motion ~ 320 mas/y. Extrapolation of the motions of the concentrations back to the binary suggests that the eastern `arm' began expansion 4--5 months earlier than those in the southern `bar', consistent with the projected rotation of the binary axis and wind-collision region (WCR) on the sky. Comparison of model dust images and the observations constrain the intervals when the WCR was producing sufficiently compressed wind for dust nucleation in the WCR, and suggests that the distribution of this material was not uniform about the axis of the WCR, but more abundant in the following edge in the orbital plane., 21 pages, 10 figures, accepted for MNRAS. A version with higher resolution figures is available at ftp://ftp.roe.ac.uk/pub/pmw/wr140dust.ps.gz

The UKIRT Infrared Deep Sky Survey (UKIDSS) is a set of five large near-infrared surveys, covering a complementary range of areas, depths, and Galactic latitudes. The UKIDSS Second Data Release (DR2) includes the First Data Release (DR1), with minor improvements, plus new data for the LAS, GPS, GCS, and DXS, from observations made over 2006 May through July (when the UDS was unobservable). DR2 was staged in two parts. The first part excluded the GPS, and took place on 2007 March 1. The GPS was released on 2007 April 12. DR2 includes 282 sq. degs of multicolour data to (Vega) K=18, complete in the full YJHK set for the LAS, 57 sq. degs in the ZYJHK set for the GCS, and 236 sq. degs in the JHK set for the GPS. DR2 includes nearly 7 sq. degs of deep JK data (DXS, UDS) to an average depth K=21. In addition the release includes a comparable quantity of data where coverage of the filter set for any survey is incomplete. We document changes that have occurred since DR1 to the pipeline, calibration, and archive procedures. The two most noteworthy changes are presentation of the data in a single database (compared to two previously), and provision of additional error flags for detected sources, flagging potentially spurious artifacts, corrupted data and suspected cross-talk sources. We summarise the contents of each of the surveys in terms of filters, areas, and depths.

An eruptive nova-like event took place in 1994 in the stellar-merger candidate V4332 Sgr. Following the eruption, dust consisting of refractory silicate rich dust grains containing a significant component of AlO bonding was formed sometime between 1998 and 2003. Observations using Spitzer between 2005 and 2009 show significant changes in the 10 micron silicate stretch feature. There is a deepening of the 10 micron silicate stretch as well as the development of a feature between about 13 and 20 microns consistent with a blend of the MgO and FeO stretching features and the O-Si-O bending mode of increasingly ordered silicate dust. Near-infrared observations show the presence of AlO and water vapor in the outflow in 2003, 2004 and 2005: the AlO has significantly decreased in spectra obtained in 2014 while the water vapor remains largely unchanged. An attempt is made to correlate these observations and understand the significance of these changes using DUSTY modeling. The observations appear consistent with the kinetically-controlled, condensation of highly under-oxidized SiO/AlO/Fe/Mg dust grains in the outflow followed by the continuous evolution of the initial condensate due to thermal annealing and oxidation of the dust via reaction with ambient O, OH and H2O in the expanding, cooling shell. Periodic monitoring of this dust shell over the mid-infrared spectral range could yield useful information on the evolution of under-oxidized silicate condensates exposed to hot water vapor in more conventional circumstellar environments., To appear in ApJ

JHK photometry in the Mauna Kea Observatory (MKO) near-IR system is presented for 115 stars. Of these, 79 are UKIRT standards and 42 are LCO standards. The average brightness is 11.5 mag, with a range of 10 to 15. The average number of nights each star was observed is 4, and the average of the internal error of the final results is 0.011 mag. These JHK data agree with those reported by other groups to 0.02 mag. The measurements are used to derive transformations between the MKO JHK photometric system and the UKIRT, LCO and 2MASS systems. The 2MASS-MKO data scatter by 0.05 mag for redder stars: 2MASS-J includes H2O features in dwarfs and MKO-K includes CO features in giants. Transformations derived for stars whose spectra contain only weak features cannot give accurate transformations for objects with strong absorption features within a filter bandpasses. We find evidence of systematic effects at the 0.02 mag level in the photometry of stars with J

Echelle spectroscopy of H2, [FeII] and Br-gamma line emission from a very young planetary nebula, IRAS 21282+5050, and from four proto-planetary nebulae, IRAS 19343+2926 (M 1-92), IRAS 17150-3224 (AFGL 6815), IRAS 17423-1755 (Hen 3-1475), and IRAS 17441-2411 is presented. H2 line emission is detected in discrete shock fronts in the lobes of each nebula, regardless of source spectral type. In IRAS 17150-3224 we also uncover possible signs of rotation, as would be expected if the H2 features were excited in a magneto-centrifugal disk wind. [FeII] emission was detected in only one source, M 1-92. The H2 and [FeII] observations of M 1-92, and the complex H2 profiles in IRAS 21282+5050, are explained using the shock models of Smith and collaborators. J-type bow models are adequate in each case, i.e. a strongly-magnetised wind is not required. Finally, Br-gamma is detected in each of the five targets; in absorption in the G-type PPN though in emission in the O and B-type sources. Br-gamma emission is detected predominantly toward the near-IR continuum peak in each PPN. Low peak velocities, though very broad profile widths, are measured in each target. The emission must therefore derive from ionised regions in a fast wind very close to the central star, or, in the late-type sources, from absorption in an equatorial torus., Comment: 17 pages, 13 figures

We present here the first light curves of the peculiar Algol binary system R Canis Majoris obtained in the near-infrared photometric bands J and K. The light curves are fitted for a semidetached model with the Wilson-Devinney light-curve synthesis program. The parameters of the system are derived. Published light curves in the optical photometric bands (U, Un, B, Bn, V, Vn, Hβw, and Hβn of Guinan, V light curve of Sato, and Hαw and Hαn light curves of Edalati, Khalesse, & Riazi) are reanalyzed and the results are compared. The temperature of the secondary component T2 derived from the light-curve analysis shows an increase toward the near-IR wavelengths, achieving maximum in the K band. The secondary minima are deeper by 0.03 and 0.07 mag and the primary minima are shallower by 0.02 and 0.03 mag in the J and K bands, respectively, than what is expected in these bands from the secondary temperature and primary radius derived from the V band. In the case of the Hα and Hβ light curves, the narrowband light curves yielded higher T2 than the broadband light curves. The values of T2 derived from these bands are found to be higher than those derived from the light curves observed in the neighboring wavelengths. We consider the possibility of the difference in the strength of photospheric absorption of Hα and Hβ lines in the primary and the secondary as a reason for the high values of T2 derived from these light curves. Five epochs of primary minima and four epochs of secondary minima are obtained in the present study. The increased depth of the secondary minima in the near-IR bands compared with the optical bands enabled us to determine the moments of secondary minima with nearly the same accuracy as those of primary minima. All the secondary minima appear at phase 0.5, and the durations are equal for the primary and the secondary eclipses. The epochs of primary minima follow the nearly sinusoidal O-C curve that has been observed for this star in previous studies. The values of O-C for the secondary minima were in the same range as those of the primary minima observed by us. We conclude that the system is in a circular orbit. Our observed epochs of primary minima support the presence of a third component in the system, as proposed by Radhakrishnan, Sarma, & Abhyankar. The effect of the presence of a third, noneclipsing, light source would be to suppress the observed depths of both the eclipses, whereas in this system we find that the secondary eclipse depth is being enhanced and the primary eclipse depth is being suppressed compared with expectations. So we have not fitted for a third light in our light-curve analysis, leaving the nature of the third body, if present, undetermined from our present light-curve analysis. The J-band light curve of R CMa fitted well with a bolometric albedo of the secondary star A2 = 0.5, as expected for a star with a convective atmosphere. But the K-band light curve showed a value of A2 = 0.84. A2 is also found to be higher in the broadband light curves than in the narrowband light curves at all the optical wavelengths (except in the U and Un bands, in which the secondary minima are very shallow). This result can provide clues about the cause of the high A2 observed in many Algol-type binary light curves. A2 is also found to vary for light curves at the same wavelengths but taken at different epochs, which helps us to conclude that the high value of A2 seen in many light curves need not be of photospheric origin.

Light curves of the Algol-type binary system, RZ Cassiopeiae, in the near-IR wavelengths J and K are obtained for the first time. The light curves are analyzed using the Wilson-Devinney model. UBV light curves of RZ Cas obtained by Chambliss are also reanalyzed using the same program. In the J and K bands, the bolometric albedo of the secondary of RZ Cas exhibited values above 0.7, whereas the theoretically expected value for such a star is 0.5. Also, the values of the secondary temperature derived from the J and K light curves are found to be less than that derived from our analysis of the optical light curves as well as from the previous studies in the optical photometric bands. We have attempted to model these effects with a dark spot on the secondary of RZ Cas. The J-band light curve gave a better fit with a cool dark spot on the secondary. Another possible reason for the above mentioned effects is a gas stream from the lobe-filling secondary to the primary star. The magnitudes and colors of the individual components are derived from the observed light curves and the light contributions from the stars derived from the light curve analysis. The primary is found to be an A3 V star as observed by previous investigators. The secondary is classified as K0?K4 IV from the derived colors. Seven epochs of primary minima and 3 epochs of secondary minima are obtained from the observations. Because of the increased depths of the secondary eclipse in the infrared bands, the moments of minima are calculated with nearly the same accuracy as that of the primary minima. All the secondary minima are found to occur at phase 0.5. None of the observed primary minima are flat as found by many observers before at optical wavelengths. The colors of the system at the minima obtained by us confirm that the system is partially eclipsing.

Aims: We aim to understand the star formation associated with the luminous young stellar object (YSO) IRAS 18345-0641 and to address the complications arising from unresolved multiplicity in interpreting the observations of massive star-forming regions. Methods: New infrared imaging data at sub-arcsec spatial resolution are obtained for IRAS 18345-0641. The new data are used along with mid- and far-IR imaging data, and CO (J=3-2) spectral line maps downloaded from archives to identify the YSO and study the properties of the outflow. Available radiative-transfer models are used to analyze the spectral energy distribution (SED) of the YSO. Results: Previous tentative detection of an outflow in the H_2 (1-0) S1 line (2.122 micron) is confirmed through new and deeper observations. The outflow appears to be associated with a YSO discovered at infrared wavelengths. At high angular resolution, we see that the YSO is probably a binary. The CO (3--2) lines also reveal a well defined outflow. Nevertheless, the direction of the outflow deduced from the H_2 image does not agree with that mapped in CO. In addition, the age of the YSO obtained from the SED analysis is far lower than the dynamical time of the outflow. We conclude that this is probably caused by the contributions from a companion. High-angular-resolution observations at mid-IR through mm wavelengths are required to properly understand the complex picture of the star formation happening in this system, and generally in massive star forming regions, which are located at large distances from us., 11 pages, 11 figures, accepted for publication in Astronomy and Astrophysics

Changes in the P Cygni profile of the 1.083-μm He I line in the spectrum of the colliding-wind Wolf-Rayet system WR140 as it passes through periastron passage allow us to map the region where the fast winds of the WC7 and O5 stars collide.

The luminous Young Stellar Object (YSO) IRAS 07422-2001 is studied in the infrared. We discover star forming activity in embedded clusters located in a cloud detected at mid-IR wavelengths in emission. Multiple outflows are discovered from these clusters in the H_2 ro-vibrational line at 2.122 micron. We detect at least six outflows from the cluster associated with the IRAS source and another outflow from a source located in a cluster detected ~2.7 arcmin NE of the IRAS source. Additional star formation is taking place in two other cluster candidates within the cloud. Three of the YSOs in the cluster associated with the IRAS source are detected at 11.2 micron at an angular resolution of ~0.8 arcsec. We have a tentative detection of a circumstellar disk in this cluster, seen as an extinction lane in the J and H-band images. The spectral energy distributions (SEDs) of the dominant YSOs in the cluster associated with the IRAS source and in the NE cluster are studied using radiative transfer models and the properties of the YSOs are estimated. The YSO associated with the IRAS source is probably in a very early Class I stage of formation. The source identified as the dominant YSO in the NE cluster appears to be older than the dominant YSO in the cluster associated with the IRAS source, but its observed flux seems to be contaminated by extra emission, which suggests the presence of a young source contributing to the SED at far-IR wavelengths. The star formation observed in the field of IRAS 07422-2001 supports the idea of hierarchical formation of massive star clusters and the growth of massive young stellar objects near the centres of multiple sub-clusters in a star forming clump through competitive accretion., 12 pages, 10 figures, accepted for publication in Astronomy and Astrophysics

We describe a search for the A-X infrared bands of AlO with a view to better understand the characteristics of this radical. These bands are infrequently encountered in astronomical sources but surprisingly were very prominent in the spectra of two well-known, nova-like variables (V838 Mon and V4332 Sgr) thereby motivating us to explore the physical conditions necessary for their excitation. In this study, we present the detection of A-X bands in the spectra of 13 out of 17 stars, selected on the basis of their J-K colors as potential candidates for detection of these bands. The majority of the AlO detections are in AGB stars viz. 9 OH/IR stars, 2 Mira variables and 2 bright infrared sources. Our study shows that the A-X bands are fairly prevalent in sources with low temperature and O-rich environments. Interesting variation in strength of the AlO bands in one of the sources (IRAS 18530+0817) is reported and the cause for this is examined. Possible applications of the present study are discussed in terms of the role of AlO in alumina dust formation, the scope for estimating the radioactive $^{26}$Al content in AGB stars from the A-X bands, and providing possible targets for further mm/radio studies of AlO which has recently been discovered at millimeter wavelengths., Comment: To appear in Astrophysical Journal (Letters), 14 pages, 2 figures

Imaging observations of IRAS 17527-2439 are obtained in the near-IR JHK photometric bands and in a narrow-band filter centred at the wavelength of the H_2 1-0 S(1) line. The continuum-subtracted H_2 image is used to identify outflows. The data obtained in this study are used in conjunction with Spitzer, AKARI, and IRAS data. A parsec-scale bipolar outflow is discovered in our H_2 line image, which is supported by the detection in the archival Spitzer images. The H_2 image exhibits signs of precession of the main jet and shows tentative evidence for a second outflow. These suggest the possibility of a companion to the outflow source. There is a strong component of continuum emission in the direction of the outflow, which supports the idea that the outflow cavity provides a path for radiation to escape, thereby reducing the radiation pressure on the accreted matter. The bulk of the emission observed close to the outflow in the WFCAM and Spitzer bands is rotated counter clockwise with respect to the outflow traced in H_2, which may be due to precession. The YSO driving the outflow is identified in the Spitzer images. The spectral energy distribution (SED) of the YSO is studied using available radiative transfer models. A model fit to the SED of the central source tells us that the YSO has a mass of 12.23 M_sun and that it is in an early stage of evolution., 6 Pages, 5 figures, accepted for publication by Astronomy and Astrophysics

We present wide-field near-IR images of Orion A. K and H2 1-0S(1) images of a contiguous 8 sqr degree region are compared to photometry from Spitzer and dust-continuum maps obtained with MAMBO and SCUBA. We also measure proper motions for H2 features in 33 outflows. We increase the number of known H2 outflows in Orion A to 116. A total of 111 H2 flows were observed with Spitzer; outflow sources are identified for at least 72 of them. The MAMBO 1200 micron maps cover 97 H2 flows; 57 of them are associated with Spitzer sources and dust cores or extended emission. The H2 jets are widely distributed and randomly orientated; the jets do not appear to be orthogonal to large-scale filaments or even to the small-scale cores. Moreover, H2 jet lengths and opening angles are not obviously correlated with indicators of outflow source age - source spectral index or (sub)millimetre core flux. We demonstrate that H2 jet sources are predominantly protostellar with flat or positive spectral indices, rather than disk-excess (or T Tauri) stars. Most protostars in molecular cores drive H2 outflows. However, not all molecular cores are associated with protostars or H2 jets. On statistical grounds, the H2 jet phase may be marginally shorter than the protostellar phase, though must be considerably shorter than the prestellar phase. In terms of their spectral index, H2 jet sources are indistinguishable from protostars. The few true protostars without H2 jets are almost certainly more evolved than their H2-jet-driving counterparts. We also find that protostars that power molecular outflows are no more (nor no less) clustered than protostars that do not. The H2 emission regions in outflows from young stars clearly weaken and fade very quickly, before the source evolves from protostar to pre-main-sequence star., Comment: Avccepted by A&A. Appendix figures (and high-res. version of paper) available from http://www.jach.hawaii.edu/~cdavis/

V4643 Sagittarii or Nova Sagittarii 2001 was discovered in outburst at 7.7 mag. on 2001 February 24. Here, we present near-infrared results of this fast classical nova obtained in the early decline phase in 2001 March followed by optical observations about one month later. Subsequently we also present near-infrared spectra taken later in the nova's evolution, about four months after the outburst, when V4643 Sgr had entered the coronal phase. The spectra in the early decline phase are dominated by emission lines of the HI Brackett series and also the Paschen beta and gamma lines. We study the cause of the excitation of the the OI line at 1.128 micron and discuss the variation in its strength with time after outburst. We discuss the role of optical depth effects on the observed strengths of the hydrogen Brackett and Paschen lines and discuss possible reasons for the puzzling behavior of the Br gamma line strength and whether it is correlated with the OI 1.128 micron line behavior. An optical spectrum is presented which shows that HeII lines are the most prominent features - after HI - to be seen in early 2001 April. We present and also discuss spectra taken in 2001 June and August which prominently show coronal lines of [Si VI] and [Si VII] at 1.9641 micron and 2.4807 micron respectively., Comment: Accepted in MNRAS

Near infrared spectroscopy and photometry of the Wolf-Rayet Star WR 143 (HD 195177) were obtained in the $JHK$ photometric bands. High resolution spectra observed in the J and H bands exhibit narrow 1.083-micron He I line and the H I Pa Beta and the Brackett series lines in emission superposed on the broad emission line spectrum of the Wolf-Rayet star, giving strong indications of the presence of a companion. From the narrow emission lines observed, the companion is identified to be an early-type Be star. The photometric magnitudes exhibit variations in the JHK bands which are probably due to the variability of the companion star. The flux density distribution is too steep for a Wolf-Rayet atmosphere. This is identified to be mainly due to the increasing contribution from the early-type companion star towards shorter wavelengths., Accepted for publication in MNRAS - 7 Pages, 5 figures

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., 10 pages, 3 figures (to appear in ApJ(Letters), 2004)

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., Accepted for publication in MNRAS - 13 Pages, 10 figures

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 2004

We present L'and M' photometry, obtained at UKIRT using the Mauna Kea Observatories Near-IR filter set, for 46 and 31 standard stars, respectively. The L' standards include 25 from the UKIRT in-house "Bright Standards" with magnitudes deriving from Elias et al. (1982) and observations at the IRTF in the early 1980s, and 21 fainter stars. The M' magnitudes derive from the results of Sinton & Tittemore (1984). We estimate the average external error to be 0.015 mag for the bright L' standards and 0.025 mag for the fainter L' standards, and 0.026 mag for the M' standards. The new results provide a network of homogeneously observed standards, and establish reference stars for the MKO system, in these bands. They also extend the available standards to magnitudes which should be faint enough to be accessible for observations with modern detectors on large and very large telescopes., Accepted for publication in MNRAS; 18 pages incl. 2 Figures and 5 Tables

Many late WC type Wolf-Rayet (WR) stars are known to form dust in their winds. While, in the case of episodic dust makers, it is now clear that dust formation takes place due to a colliding wind phenomenon, we still do not know for sure if binarity is the main reason for dust formation in persistent dust makers. This work is to understand, if persistent dust formation is also due to colliding winds in close binary systems. A systematic search for colliding winds is taken up via high resolution spectroscopy of the He i λ1.083μm emission line. Preliminary indications of binarity in many persistent dust makers are seen.

The near-IR spectrum of the periodic dust making WCpd+O4-5 binary WR 140 was monitored to cover the 2001 periastron passage and maximum colliding-wind activity. The He i λ1.083μm emission-line profile showed the appearence of a subpeak on epochs close to periastron passage. The evolution of the subpeak was consistent with the motion of the stars and the colliding wind region. The appearance and evolution of the emission subpeak suggests that the theoretical 1/r dependence of X-ray flux does not hold, so that there is no need to change the values of eccentricity and epoch of periastron passage derived from the RV orbit. JHK spectra show variations of the continuum and and dilution of the emission lines, in agreement with the production and cooling of dust.