Molecules and dust are formed in and around the asymptotic giant branch (AGB) stars and supernovae (SNe), and are ejected into the interstellar medium (ISM) through the stellar wind. The dust and gas contain elements newly synthesised in stars, thus, dying stars play an important role on chemical enrichment of the ISM of galaxies. However, quantitative analysis of molecules and dust in these stars had been difficult beyond our Galaxy. The high sensitivity instruments on board the Spitzer Space Telescope have enabled us to study dust and molecules in these stars in nearby galaxies. Nearby galaxies have wide range of metallicities, thus the impact of the metallicity on dust and gas production can be studied. This study will be useful for chemical evolution of galaxies from low to high metallicities.
We report the Spitzer Infrared Spectrograph (IRS) observations of three evolved stars: IRAS 16456-3542, 18354-0638, and 23239+5754. The 9.9--37.2um Spitzer/IRS high resolution spectra of these three sources exhibit rich sets of enstatite-dominated crystalline silicate emission features. IRAS 16456-3542 is extremely rich in crystalline silicates, with >90% of its silicate mass in crystalline form, the highest to date ever reported for crystalline silicate sources.
Due to their brightness in infrared, asymptotic giant branch (AGB) stars are in important evolutionary stage to be understood at this wavelength. In particular, in next decades, when the infrared optimised telescopes, such as the JWST and the ELT are in operation, it will be essential to include the AGB phase more precisely into the population synthesis models. However, the AGB phase is still one of the remaining major problems in the stellar evolution. This is because the AGB stellar evolution is strongly affected by the mass-loss process from the stars. It is important to describe mass loss …
Massive evolved stars loss a large fraction of their mass via copious stellar wind or instant outbursts and during certain evolutionary phases they can be identified via the presence of their circumstellar nebulae. In this paper, we present the results of search for compact nebulae (reminiscent of circumstellar nebulae around evolved massive stars) using archival 24 $μ$m data obtained with the Multiband Imaging Photometer for Spitzer. We discovered 115 nebulae, most of which bear a striking resemblance to the circumstellar nebulae associated with Luminous Blue Variables (LBVs) and late WN-type…
We present the results of optical spectroscopic observations of 54 candidate evolved massive stars revealed through the detection of mid-infrared nebulae of various shapes surrounding them with the {\it Spitzer Space Telescope} and {\it Wide-field Infrared Survey Explorer}. These observations, carried out with the Southern African Large Telescope (SALT) in 2010-2015, led to the discovery of about two dozens emission-line stars, of which 15 stars we classify as candidate luminous blue variables (cLBVs). Spectroscopic and photometric monitoring revealed significant changes in the spectra and bri…
The survey for DUST In Nearby Galaxies with Spitzer (DUSTiNGS) has identified hundreds of candidate dust-producing Asymptotic Giant Branch (AGB) stars in several nearby metal-poor galaxies. We have obtained multi-epoch follow-up observations for these candidates with the Spitzer Space Telescope and measured their infrared (IR) lightcurves. This has allowed us to confirm their AGB nature and investigate pulsation behavior at very low metallicity. We have obtained high-confidence pulsation periods for 88 sources in seven galaxies. We have confirmed DUSTiNGS variable star candidates with a 20% su…
We present Spitzer IRAC $3.6-8$um and MIPS $24$um point-source catalogs for seven galaxies: NGC$6822$, M$33$, NGC$300$, NGC$2403$, M$81$, NGC$0247$, and NGC$7793$. The catalogs contain a total of $\sim300,000$ sources and were created by dual-band selection of sources with $>3σ$ detections at both $3.6$um and $4.5$um. The source lists become significantly incomplete near $m_{3.6}=m_{4.5}\simeq18$. We complement the $3.6$um and $4.5$um fluxes with $5.8$um, $8.0$um and $24$um fluxes or $3σ$ upper limits using a combination of PSF and aperture photometry. This catalog is a resource as an archive …
Dust production is explored around 14 metal-poor ([Fe/H] = -1.91 to -0.98) giant stars in the Galactic globular cluster omega Centauri using new Spitzer IRS spectra. This sample includes the cluster's post-AGB and carbon stars and is thus the first representative spectral study of dust production in a metal-poor ([Fe/H] < -1) population. Only the more metal rich stars V6 and V17 ([Fe/H] = -1.08, -1.06) exhibit silicate emission, while the five other stars with mid-infrared excess show only a featureless continuum which we argue is caused by metallic iron dust grains. We examine the metallicity…
A new link in the causal mapping between massive stars and potentially fatal explosive transients opened with the 2008 discovery of the dust-obscured progenitors of the luminous outbursts in NGC 6946 and NGC 300. Here we carry out a systematic mid-IR photometric search for massive, luminous, self-obscured stars in four nearby galaxies: M33, NGC 300, M81, and NGC 6946. For detection, we use only the 3.6 micron and 4.5 micron IRAC bands, as these can still be used for multi-epoch Spitzer surveys of nearby galaxies (=<10 Mpc). We combine familiar PSF and aperture-photometry with an innovative app…
Supernova fallback disks around neutron stars have been discussed to influence the evolution of the diverse neutron star populations. Slowly rotating neutron stars are most promising to find such disks. Searching for the cold and warm debris of old fallback disks, we carried out Herschel PACS (70 $μ$m, 160 $μ$m) and Spitzer IRAC (3.6 $μ$m, 4.5 $μ$m) observations of eight slowly rotating ($P\approx 3 - 11$ s) nearby ($<1$ kpc) isolated neutron stars. Herschel detected 160 $μ$m emission ($>5σ$) at locations consistent with the positions of the neutron stars RX J0806.4-4123 and RX J2143.0+0654. N…
The Spitzer Space Telescope has advanced debris disk science tremendously with a wealth of information on debris disks around nearby A, F, G, K and M stars at 24 and 70 microns with the MIPS photometer and at 8-34 microns with IRS. Here we present 160 micron observations of a small sub-set of these stars. At this wavelength, the stellar photospheric emission is negligible and any detected emission corresponds to cold dust in extended Kuiper belt analogs. However, the Spitzer 160 micron observations are limited in sensitivity by the large beam size which results in significant ''noise'' due to …
We present $Spitzer$ IRAC mid-infrared point source catalogs for mosaics covering the fields of the nearby ($\lesssim$4 Mpc) galaxies NGC 55, NGC 253, NGC 2366, NGC 4214, and NGC 5253. We detect a total of 20159 sources in these five fields. Point spread function photometry was performed on sources detected in both $Spitzer$ IRAC 3.6 $μ$m and 4.5 $μ$m bands at greater than 3$σ$ above background. These data were then supplemented by aperture photometry in the IRAC 5.8 $μ$m and 8.0 $μ$m bands conducted at the positions of the shorter wavelength sources. For sources with no detected object in the…
The late-stage evolution of the most massive stars such as η Carinae is controlled by the effects of mass loss, which may be dominated by poorly understood eruptive mass ejections. Understanding this population is challenging because no true analogs of η Car have been clearly identified in the Milky Way or other galaxies. We utilize Spitzer IRAC images of 7 nearby (=<4 Mpc) galaxies to search for such analogs. We find 34 candidates with a flat or rising mid-IR spectral energy distributions towards longer mid-infrared wavelengths that emit 10^5 L_sun in the IRAC bands (3.6 to 8.0 micron) and ar…
The survey for DUST in Nearby Galaxies with Spitzer (DUSTiNGS) identified several candidate Asymptotic Giant Branch (AGB) stars in nearby dwarf galaxies and showed that dust can form even in very metal-poor systems (Z ~ 0.008 $Z_\odot$). Here, we present a follow-up survey with WFC3/IR on the Hubble Space Telescope (HST), using filters that are capable of distinguishing carbon-rich (C-type) stars from oxygen-rich (M-type) stars: F127M, F139M, and F153M. We include six star-forming DUSTiNGS galaxies (NGC 147, IC 10, Pegasus dIrr, Sextans B, Sextans A, and Sag DIG), all more metal-poor than the …
We present new observations of the CB130 region, composed of three separate cores. Using the \textit{Spitzer Space Telescope} we detected a Class 0 and a Class II object in one of these, CB130-1. The observed photometric data from \textit{Spitzer} and ground-based telescopes are used to establish the physical parameters of the Class 0 object. SED fitting with a radiative transfer model shows that the luminosity of the Class 0 object is 0.14 $-$ 0.16 L$_{\odot}$, which is a low luminosity for a protostellar object. In order to constrain the chemical characteristics of the core having the low lu…
We report the lens mass and distance measurements of the nearby microlensing event TCP J05074264+2447555. We measure the microlens parallax vector $π_{\rm E}$ using Spitzer and ground-based light curves with constraints on the direction of lens-source relative proper motion derived from Very Large Telescope Interferometer (VLTI) GRAVITY observations. Combining this $π_{\rm E}$ determination with the angular Einstein radius $θ_{\rm E}$ measured by VLTI GRAVITY observations, we find that the lens is a star with mass $M_{\rm L} = 0.495 \pm 0.063~M_{\odot}$ at a distance $D_{\rm L} = 429 \pm 21~{\…
We report Spitzer Space Telescope IRAC 3.6, 4.5, 5.8 and 8 um and MIPS 24 and 70 um observations of the 32 Ori Group, a recently discovered nearby stellar association situated towards northern Orion. The proximity of the group (~93 pc) has enabled a sensitive search for circumstellar dust around group members, and its age (~20 Myr) corresponds roughly to an epoch thought to be important for terrestrial planet formation in our own solar system. We quantify infrared excess emission due to circumstellar dust among group members, utilizing available optical (e.g. Hipparcos, Tycho) and near-IR (2MA…
The Spitzer Space Telescope mapped the Perseus molecular cloud complex with IRAC and MIPS as part of the c2d Spitzer Legacy project. This paper combines the observations from both instruments giving an overview of low-mass star formation across Perseus from 3.6 to 70 micron. We provide an updated list of young stellar objects with new classifications and source fluxes from previous works, identifying 369 YSOs in Perseus with the Spitzer dataset. By synthesizing the IRAC and MIPS maps of Perseus and building on the work of previous papers in this series (Jorgensen et al. 2006, Rebull et al. 200…
Understanding the late-stage evolution of the most massive stars such as $η$ Carinae is challenging because no true analogs of $η$ Car have been clearly identified in the Milky Way or other galaxies. In Khan et. al. (2013), we utilized Spitzer IRAC images of $7$ nearby ($\lesssim4$ Mpc) galaxies to search for such analogs, and found $34$ candidates with flat or red mid-IR spectral energy distributions. Here, in Paper II, we present our characterization of these candidates using multi-wavelength data from the optical through the far-IR. Our search detected no true analogs of $η$ Car, which impl…
[ABRIDGED] We present the first resolved images of the debris disk around the nearby K dwarf HD 92945. Our F606W (V) and F814W (I) HST/ACS coronagraphic images reveal an inclined, axisymmetric disk consisting of an inner ring 2".0-3".0 (43-65 AU) from the star and an extended outer disk whose surface brightness declines slowly with increasing radius 3".0-5".1 (65-110 AU) from the star. A precipitous drop in the surface brightness beyond 110 AU suggests that the outer disk is truncated at that distance. The radial surface-density profile is peaked at both the inner ring and the outer edge of th…
We identify protostars in Spitzer surveys of nine star-forming molecular clouds within 1 kpc: Serpens, Perseus, Ophiuchus, Chamaeleon, Lupus, Taurus, Orion, Cep OB3, and Mon R2, which combined host over 700 protostar candidates. Our diverse cloud sample allows us to compare protostar luminosity functions in these varied environments. We combine photometry from 2MASS J, H, and Ks bands and Spitzer IRAC and MIPS 24 micron bands to create 1 - 24 micron spectral energy distributions (SEDs). Using protostars from the c2d survey with well-determined bolometric luminosities (Lbol), we derive a relati…
We map the full extent of a rich massive young cluster in the Cep OB3b association with the IRAC and MIPS instruments aboard the {\it Spitzer} Space Telescope and the ACIS instrument aboard the $\it{Chandra}$ X-Ray Observatory. At 700 pc, it is revealed to be the second nearest large ($>1000$ member), young ($< 5$ Myr) cluster known. In contrast to the nearest large cluster, the Orion Nebula Cluster, Cep OB3b is only lightly obscured and is mostly located in a large cavity carved out of the surrounding molecular cloud. Our infrared and X-ray datasets, as well as visible photometry from the lit…
The role of episodic mass loss in massive star evolution is one of the most important open questions of current stellar evolution theory. Episodic mass loss produces dust and therefore causes evolved massive stars to be very luminous in the mid-infrared and dim at optical wavelengths. We aim to increase the number of investigated luminous mid-IR sources to shed light on the late stages of these objects. To achieve this we employed mid-IR selection criteria to identity dusty evolved massive stars in two nearby galaxies. The method is based on mid-IR colors, using 3.6 μm and 4.5 μm photometry fr…
Long-slit spectroscopy with the Southern African Large Telescope (SALT) of central stars of mid-infrared nebulae detected with the Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE) led to the discovery of numerous candidate luminous blue variables (cLBVs) and other rare evolved massive stars. With the recent advent of the SALT fibre-fed high-resolution echelle spectrograph (HRS), a new perspective for the study of these interesting objects is appeared. Using the HRS we obtained spectra of a dozen newly identified massive stars. Some results on the recently identified cLBV …
We present high angular resolution SMA and Spitzer observations toward the Bok globule CB17. SMA 1.3mm dust continuum images reveal within CB17 two sources with an angular separation of about 21" (about 5250 AU at a distance of 250 pc). The northwestern continuum source, referred to as CB17 IRS, dominates the infrared emission in the Spitzer images, drives a bipolar outflow extending in the northwest-southeast direction, and is classified as a low luminosity Class0/I transition object (L_bol ~ 0.5 L_sun). The southeastern continuum source, referred to as CB17 MMS, has faint dust continuum emis…
We present the highest resolution single-dish submillimetre observations of the detached shell source U Antliae to date. The observations were obtained at $450~\micron$ and $850~\micron$ with SCUBA-2 instrument on the James Clerk Maxwell Telescope as part of the Nearby Evolved Stars Survey. The emission at $850~\micron$ peaks at $40\arcsec$ with hints of a second peak seen at $\sim 20\arcsec$. The emission can be traced out to a radius of $56\arcsec$ at a $3σ$ level. The outer peak observed at $850~\micron$ aligns well with the peak observed at Herschel/PACS wavelengths. With the help of spect…
Throughout the last decade sensitive infrared observations obtained by the Spitzer Space Telescope significantly increased the known population of YSOs associated with nearby molecular clouds. With such a census recent studies have characterized pre-main sequence stars (PMS) and determined parame- ters from different wavelengths. Given the restricted Spitzer coverage of some of these clouds, relative to their extended regions, these YSO populations may represent a limited view of star formation in these regions. We are taking advantage of mid-infrared observations from the NASA Wide Field Infr…
The Nearby Evolved Stars Survey (NESS) is a volume-complete sample of $\sim$850 Galactic evolved stars within 3\,kpc at (sub-)mm wavelengths, observed in the CO $J = $ (2$-$1) and (3$-$2) rotational lines, and the sub-mm continuum, using the James Clark Maxwell Telescope and Atacama Pathfinder Experiment. NESS consists of five tiers, based on distances and dust-production rate (DPR). We define a new metric for estimating the distances to evolved stars and compare its results to \emph{Gaia} EDR3. Replicating other studies, the most-evolved, highly enshrouded objects in the Galactic Plane domina…
Nearby star-forming regions are ideal laboratories to study high-energy emission of different stellar populations, from very massive stars to brown dwarfs. NGC 2023 is a reflection nebula situated on the south of the Flame Nebula (NGC 2024) and at the edge of the H ii region IC 434, which also contains the Horsehead Nebula (Barnard 33). NGC 2023, NGC 2024, Barnard 33 and the surroundings of the O-type supergiant star ζ Ori constitute the south part of the Orion B molecular complex. In this work, we present a comprehensive study of X-ray emitters in the region of NGC 2023 and its ?surroundings.…
We investigate the distribution of different classes of spectroscopically identified sources and theoretical models in the color-color diagrams (CCDs) combining the near-infrared (NIR) and mid-infrared (MIR) data to develop a method to classify Outer Galaxy sources detected with the Spitzer Space Telescope (hereafter Spitzer) SMOG survey in the IRAC 3.6 and 8.0 micrometer and MIPS 24 micrometer bands. We supplement the Spitzer data with the data from other satellite and ground-based surveys. The main goal of our study is to discover and characterize the population of intermediate- and low-mass…
We present observations of newly discovered 24 micron circumstellar structures detected with the Multiband Imaging Photometer for Spitzer (MIPS) around three evolved stars in the Cygnus-X star forming region. One of the objects, BD+43 3710, has a bipolar nebula, possibly due to an outflow or a torus of material. A second, HBHA 4202-22, a Wolf-Rayet candidate, shows a circular shell of 24 micron emission suggestive of either a limb-brightened shell or disk seen face-on. No diffuse emission was detected around either of these two objects in the Spitzer 3.6-8 micron Infrared Array Camera (IRAC) b…
Using photometric data of infrared surveys, young stellar object (YSO) status is verified for 141 objects selected in our previous papers in the Cassiopeia and Camelopardalis segment of the Milky Way bounded by Galactic coordinates (l, b) = (132--158 deg, p/m 12 deg). The area includes the known star-forming regions in the emission nebulae W3, W4 and W5 and the massive YSO AFGL 490. Spectral energy distribution (SED) curves between 700 nm and 160 microns, constructed from the GSC2, 2MASS, IRAS, MSX, Spitzer and AKARI data, are used to estimate the evolutionary stages of these stars. We confirm…
In this paper, we report the results of spectroscopic and photometric observations of the candidate evolved massive star MN48 disclosed via detection of a mid-infrared circular shell around it with the Spitzer Space Telescope. Follow-up optical spectroscopy of MN48 with the Southern African Large Telescope (SALT) carried out in 2011--2015 revealed significant changes in the spectrum of this star, which are typical of luminous blue variables (LBVs). The LBV status of MN48 was further supported by photometric monitoring which shows that in 2009--2011 this star has brightened by approx 0.9 and 1 …
We present IRAC/MIPS Spitzer Space Telescope observations of the solar type and the low mass stellar population of the young (~5 Myr) Lambda Orionis cluster. Combining optical and 2MASS photometry, we identify 436 stars as probable members of the cluster. Given the distance (450 pc) and the age of the cluster, our sample ranges in mass from 2 solar mass to objects below the substellar limit. With the addition of the Spitzer mid-infrared data, we have identified 49 stars bearing disks in the stellar cluster. Using spectral energy distribution (SED) slopes, we place objects in several classes: n…
NSF National Optical-Infrared Astronomy Research Laboratory（美国国家光学红外天文研究实验室）；Radcliffe Institute for Advanced Study at Harvard University（哈佛大学拉德克利夫高等研究院）；American Museum of Natural History（美国自然历史博物馆）；Planétarium de Montréal, Espace pour la Vie（蒙特利尔天文馆生命空间）；Université de Montréal（蒙特利尔大学）；United States Naval Observatory, Flagstaff Station（美国海军天文台弗拉格斯塔夫站）
We present 3D hydrodynamic models of the interaction between the outflows of evolved, pulsating, Asymptotic Giant Branch (AGB) stars and nearby ($< 3$ stellar radii) sub-stellar companions ($M_{\mathrm{comp}} \lesssim 40$ M$_J$). Our models show that due to resonances between the orbital period of the companion and the pulsation period of the AGB star, multiple spiral structures can form; the shocks driven by the pulsations are enhanced periodically in different regions as they encounter the denser material created by the sub-stellar companion's wake. We discuss the properties of these spiral …
We investigate the population of cool, evolved stars in the Local Group dwarf elliptical galaxy M32, using Infrared Array Camera observations from the Spitzer Space Telescope. We construct deep mid-infrared colour-magnitude diagrams for the resolved stellar populations within 3.5 arcmin of M32's centre, and identify those stars that exhibit infrared excess. Our data is dominated by a population of luminous, dust-producing stars on the asymptotic giant branch (AGB) and extend to approximately 3 mag below the AGB tip. We detect for the first time a sizeable population of `extreme' AGB stars, hig…
We present new low-resolution (R~800) optical spectra of 22 Galactic PNe with Spitzer spectra. These data are combined with recent optical spectroscopic data available in the literature to construct representative samples of compact (and presumably young) Galactic disc and bulge PNe with Spitzer spectra. Attending to the nature of the dust features seen in their Spitzer spectra, Galactic disc and bulge PNe are classified according to four major dust types (oxygen chemistry or OC, carbon chemistry or CC, double chemistry or DC, featureless or F) and subtypes (amorphous and crystalline, and alip…
We present a uniform mid-infrared imaging and photometric survey of 36 young, nearby, star-forming clusters and groups using {\it Spitzer} IRAC and MIPS. We have confidently identified and classified 2548 young stellar objects using recently established mid-infrared color-based methods. We have devised and applied a new algorithm for the isolation of local surface density enhancements from point source distributions, enabling us to extract the overdense cores of the observed star forming regions for further analysis. We have compiled several basic structural measurements of these cluster cores…
We present results from a spectroscopic Spitzer and Herschel mid-to-far-infrared study of the circumbinary disk orbiting the evolved (age ~12-23 Myr) close binary T Tauri system V4046 Sgr. Spitzer IRS spectra show emission lines of [Ne II], H_2 S(1), CO_2 and HCN, while Herschel PACS and SPIRE spectra reveal emission from [O I], OH, and tentative detections of H_2O and high-J transitions of CO. We measure [Ne III]/[Ne II] < 0.13, which is comparable to other X-ray/EUV luminous T Tauri stars that lack jets. We use the H_2 S(1) line luminosity to estimate the gas mass in the relatively warm surf…
We report observational techniques, results, and Monte Carlo population analyses from a Spitzer Infrared Array Camera imaging survey for substellar companions to 117 nearby M, L, and T dwarf systems (median distance of 10 pc, mass range of 0.6 to \sim0.05 M\odot). The two-epoch survey achieves typical detection sensitivities to substellar companions of [4.5 μm] \leq 17.2 mag for angular separations between about 7" and 165". Based on common proper motion analysis, we find no evidence for new substellar companions. Using Monte Carlo orbital simulations (assuming random inclination, random eccen…
Spitzer MIPS 24 um images were obtained for 36 Galactic planetary nebulae (PNe) whose central stars are hot white dwarfs (WDs) or pre-WDs with effective temperatures of ~100,000 K or higher. Diffuse 24 um emission is detected in 28 of these PNe. The eight non-detections are angularly large PNe with very low H-alpha surface brightnesses. We find three types of correspondence between the 24 um emission and H-alpha line emission of these PNe: six show 24 um emission more extended than H-alpha emission, nine have a similar extent at 24 um and H-alpha, and 13 show diffuse 24 um emission near the ce…
Beginning with the enigmatic (and now emblematic) TW Hya, the scutiny of individual stars and star-disk systems has both motivated and benefitted from the identification of nearby young moving groups (NYMGs). I briefly outline the emergence of this relatively new subfield of astronomy over the past two decades, and offer a few examples illustrating how the study of NYMGs and their members enables unique investigations of pre-main sequence stellar evolution, evolved protoplanetary disks, and young exoplanets.
We present JCMT SCUBA-2 $450μ$m and $850μ$m observations of 14 Asymptotic Giant Branch (AGB) stars (9 O--rich, 4 C-rich and 1 S--type) and one Red Supergiant (RSG) in the Solar Neighbourhood. We combine these observations with \emph{Herschel}/PACS observations at $70μ$m and $160μ$m and obtain azimuthally-averaged surface-brightness profiles and their PSF subtracted residuals. The extent of the SCUBA-2 850 $μ$m emission ranges from 0.01 to 0.16 pc with an average of $\sim40\%$ of the total flux being emitted from the extended component. By fitting a modified black-body to the four-point SED at …
We present a new analysis of the physical conditions in three Herbig-Haro complexes (HH 54, HH 212, and the L 1157 protostellar jet) using archival data from the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. As described in detail in Paper I, the emission observed using the 4.5-micron filter is enhanced in molecular shocks (T=1000-4000 K) at relatively high temperature or densities compared with that observed with the 8.0-micron filter. Using these data sets, we investigate different distributions of gas between high and low temperatures/densities. Our analysis reveals the prese…
Direct imaging surveys have discovered wide-orbit planetary-mass companions that challenge existing models of both star and planet formation, but their demographics remain poorly sampled. We have developed an automated binary companion point spread function (PSF) fitting pipeline to take advantage of Spitzer's infrared sensitivity to planetary-mass objects and circum(sub)stellar disks, measuring photometry across the four IRAC channels of 3.6 $μ$m, 4.5 $μ$m, 5.8 $μ$m, and 8.0 $μ$m. We present PSF-fitting photometry of archival Spitzer/IRAC images for 11 young, low-mass ($M\sim0.044$-0.88 $M_{\…
The formation scenarios for single low-mass (M < 0.45 Msol) white dwarfs include enhanced mass loss from a metal-rich progenitor star or a common envelope phase of a solar-like star with a close-in massive planet or a brown dwarf. Both scenarios suggest that low-mass white dwarfs may have planets. Here, we present a Spitzer IRAC search for substellar and planetary mass companions to 14 low-mass white dwarfs. One of our targets, HS 1653+7753, displays near- and mid-infrared flux excess. However, follow-up MMT observations show that this excess is due to a nearby resolved source, which is mostly…
[abridged] We present 52-93 micron spectra obtained with Spitzer in the MIPS-SED mode, of a representative sample of luminous compact far-IR sources in the LMC. These include carbon stars, OH/IR AGB stars, post-AGB objects and PNe, RCrB-type star HV2671, OH/IR red supergiants WOHG064 and IRAS05280-6910, B[e] stars IRAS04530-6916, R66 and R126, Wolf-Rayet star Brey3a, Luminous Blue Variable R71, supernova remnant N49, a large number of young stellar objects, compact HII regions and molecular cores, and a background galaxy (z~0.175). We use the spectra to constrain the presence and temperature o…
Multi-epoch infrared photometry from Spitzer is used to monitor circumstellar discs at white dwarfs, which are consistent with disrupted minor planets whose debris is accreted and chemically reflected by their host stars. Widespread infrared variability is found across the population of 37 stars with two or more epochs. Larger flux changes occur on longer time-scales, reaching several tens of per cent over baselines of a few years. The canonical model of a geometrically thin, optically thick disc is thus insufficient, as it cannot give rise to the observed behaviour. Optically thin dust best a…
The Nearby Evolved Stars Survey III: First data release of JCMT CO-line observations
Institute of Astronomy, KU Leuven（鲁汶大学天体物理研究所）；Institute of Astronomy and Astrophysics, Academia Sinica（中央研究院天文及天文物理研究所）；Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, College Lane Campus, University of Hertfordshire（赫特福德大学天体物理研究中心）；European Southern Observatory（欧洲南方天文台）；Space Science Institute（太空科学研究所）；Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México（墨西哥国立自治大学射电天文学与天体物理研究所）；East Asian Observatory (JCMT)（东亚天文台）；JBCA, Department Physics and Astronomy, University of Manchester（曼彻斯特大学物理学与天文学系JBCA）；School of Physical Sciences, The Open University（开放大学物理科学学院）
