- ID:
- ivo://CDS.VizieR/J/PASP/122/347
- Title:
- Chinese Small Telescope ARray (CSTAR)
- Short Name:
- J/PASP/122/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In 2008 January the twenty-fourth Chinese expedition team successfully deployed the Chinese Small Telescope ARray (CSTAR) to Dome A, the highest point on the Antarctic plateau. CSTAR consists of four 14.5cm optical telescopes, each with a different filter (g,r,i, and open) and has a 4.5{deg}x4.5{deg} field of view (FOV). It operates robotically as part of the Plateau Observatory, PLATO, with each telescope taking an image every ~30s throughout the year whenever it is dark. During 2008, CSTAR 1 performed almost flawlessly, acquiring more than 0.3 million -band images for a total integration time of 1728hr during 158 days of observations. For each image taken under good sky conditions, more than 10,000 sources down to magnitude could be detected. We performed aperture photometry on all the sources in the field to create the catalog described herein. Since CSTAR has a fixed pointing centered on the south celestial pole (Dec=-90{deg}), all the sources within the FOV of CSTAR were monitored continuously for several months. The photometric catalog can be used for studying any variability in these sources, and for the discovery of transient sources such as supernovae, gamma-ray bursts, and minor planets.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/433/543
- Title:
- Choirs, HI galaxy groups
- Short Name:
- J/MNRAS/433/543
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- H{alpha} observations centred on galaxies selected from the Hi Parkes All-Sky Survey (HiPASS) typically show one and sometimes two star-forming galaxies within the ~15arcmin beam of the Parkes 64m HI detections. In our Survey for Ionization in Neutral Gas Galaxies (SINGG) we found 15 cases of HiPASS sources containing four or more emission line galaxies (ELGs). We name these fields Choir groups. In the most extreme case, we found a field with at least nine ELGs. In this paper, we present a catalogue of Choir group members in the context of the wider SINGG sample. The dwarf galaxies in the Choir groups would not be individually detectable in HiPASS at the observed distances if they were isolated, but are detected in SINGG narrow-band imaging due to their membership of groups with sufficiently large total HI mass. The ELGs in these groups are similar to the wider SINGG sample in terms of size, H{alpha} equivalent width and surface brightness. Eight of these groups have two large spiral galaxies with several dwarf galaxies and may be thought of as morphological analogues of the Local Group. However, on average our groups are not significantly Hi deficient, suggesting that they are at an early stage of assembly, and more like the M81 group. The Choir groups are very compact at typically only 190kpc in projected distance between the two brightest members. They are very similar to SINGG fields in terms of star formation efficiency (SFE; the ratio of star formation rate to HI mass), showing an increasing trend in SFE with stellar mass.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A110
- Title:
- Chromospheric activity of nearby Sun-like stars
- Short Name:
- J/A+A/641/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chromospheric emission in the cores of the CaII H & K lines of late-type dwarfs is a well known indicator of magnetic activity that decreases with increasing stellar age. I use this indicator to investigate the formation history of nearby G- and early K-type stars with origins at galactocentric distances similar to that of the region where the Sun was born. A parent sample of single main-sequence stars with near-solar metallicity and known magnetic activity levels is built from catalogues of stellar atmospheric parameters and chromospheric activity indices. A kinematical approach uses Gaia astrometric data to differentiate thin disc stars from thick disc stars. Measured distributions of R'_HK_ chromospheric activity indices are compared with Monte Carlo simulations based on an empirical model of chromospheric activity evolution. The thin disc includes a significant fraction of Sun-like stars with intermediate activity levels while most early K- and G-type stars from the thick disc are inactive. The chromospheric activity distribution among nearby Sun-like dwarfs from the thin disc can be explained by a combination of an old (>6-7Gyr) star formation event (or events) and a more recent (<3Gyr) burst of star formation. Such an event is not required to account for the R'_HK_ index distributions of nearby thick disc stars. The distribution of magnetic activity among local G- and early K-type stars with a near-solar metallicity bears the imprint of an important star formation event that occurred ~1.9 to 2.6Gyr ago in the thin disc of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/AJ/159/292
- Title:
- Chromospheric activity of SZ Piscium
- Short Name:
- J/AJ/159/292
- Date:
- 08 Dec 2021
- Publisher:
- CDS
- Description:
- To continue our study on chromospheric activity and detection for possible prominence events of the very active RS Canum Venaticorum star SZ Piscium (SZ Psc), long-term high-resolution spectroscopic observations were obtained during several observing runs from 2014 to 2018. Based on the spectral subtraction technique, the chromospheric emission of the CaII IRT ({lambda}8662, {lambda}8542, and {lambda}8498), H_{alpha}_, NaI D_1_, D_2_ doublet, H_{beta}_, and CaII H & K lines is mainly associated with the K1 IV primary star of the SZ Psc system, in good agreement with the previous studies, and the F8 V secondary star also shows some chromospheric emission, implying its active chromosphere. Moreover, an optical flare characterized by the HeI D3 line emission together with stronger emission in the other indicators was detected. Furthermore, two chromospheric active longitudes around the two quadratures of the system were identified for most of the time, and the chromospheric activity shows significant changes during a few orbital cycles. The chromospheric activity level seems to show a long-term variation during our observations. There were some excess absorption features in the subtracted H{alpha} line and the other activity indicators, which would be caused by prominence-like materials associated with the K1 IV primary star of the system. Prominence materials could absorb the chromospheric emission and continuum from the K1 IV primary star and even the F8 V secondary one.
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/2139
- Title:
- CI Cyg BVRcIc light curves
- Short Name:
- J/MNRAS/399/2139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we discuss the early phases of the ongoing outburst that CI Cyg, a prototype symbiotic star, is currently undergoing after 30-year quiescence. We have tightly monitored CI Cyg in B V R_C_ I_C_ bands, starting a whole year before the onset of the outburst, and in addition we obtained numerous Echelle high- and low-resolution absolutely flux-calibrated spectra. The outburst started while the accreting white dwarf (WD) was being eclipsed by the Roche lobe filling M giant companion, and it was discovered during the egress phase on the second half of 2008 August. The system reached peak V-band brightness in early 2008 October and has been characterized by amplitudes {delta}B=1.9, {delta}V=1.5, {delta}R_C_=0.9, {delta}I_C_=0.4mag. At maximum V-band brightness, the outbursting WD had expanded to closely resemble an F3 II/Ib star, with MV=-3.5, Teff~6900K and R=28R_{sun}_. The high-ionization emission lines ([NeV], [FeVII], HeII) disappeared and only lower ionization lines were visible. Balmer and He I emission lines declined in equivalent width but increased in absolute flux. The output radiated by the hot component during the outburst corresponds to nuclear burning proceeding at a 2x10^-8^M_{sun}_/yr rate.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A163
- Title:
- CIG 96 deep optical and HI images
- Short Name:
- J/A+A/619/A163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Asymmetries in atomic hydrogen (HI) in galaxies are often caused by the interaction with close companions, making isolated galaxies an ideal framework to study secular evolution. The AMIGA project has demonstrated that isolated galaxies show the lowest level of asymmetry in their HI integrated profiles compared to even field galaxies, yet some present significant asymmetries. CIG 96 (NGC 864) is a representative case reaching a 16% level. Our aim is to investigate the HI asymmetries of the spiral galaxy CIG 96 and what processes have triggered the star-forming regions observed in the XUV pseudo-ring. We performed deep optical observations at CAHA1.23m, CAHA2.2m and VST (OmegaCAM wide-field camera) telescopes. We reach surface brightness (SB) limits of {mu}_CAHA2.2m_=27.5mag/arcsec^2^ (Cousins R) and {mu}_VST_=28.7mag/arcsec^2^ (SDSS r) that show the XUV pseudo-ring of the galaxy in detail. Additionally, a wavelet filtering of the HI data cube from our deep observations with VLA/EVLA telescope allowed us to reach a column density of N_HI_=8.9x10^18^cm^-2^ (5{sigma}) (28"x28" beam), lower than in any isolated galaxy. We confirm that the HI of CIG 96 extends farther than 4xr_25_ in all directions. Furthermore, we detect for the first time two gaseous structures (~10^6^M_{sun}_) in the outskirts. The SDSS g-r colour index image from CAHA1.23m shows extremely blue colours in certain regions of the pseudo-ring where N_HI_>8.5x10^20^cm^-2^, whereas the rest show red colours. Galactic cirrus contaminate the field, setting an unavoidable detection limit at 28.5mag/arcsec^2^ (SDSS r). At the current SB and NHI levels, we detect no stellar link within 1{deg}x1{deg} or gaseous link within 40'x40' between CIG 96 and any companion. The isolation criteria rule out interactions with other similar-sized galaxies for at least 2.7Gyr. Using existing stellar evolution models, the age of the pseudo-ring is estimated at 1Gyr or older. Undetected previously accreted companions and cold gas accretion remain as the main hypothesis to explain the optical pseudo-ring and HI features of CIG 96.
- ID:
- ivo://CDS.VizieR/J/ApJ/898/85
- Title:
- CII emission-line stars in LMC with MagE spectra
- Short Name:
- J/ApJ/898/85
- Date:
- 21 Mar 2022 08:48:14
- Publisher:
- CDS
- Description:
- We present a narrowband imaging survey of the Large Magellanic Cloud (LMC), designed to isolate the CII{lambda}{lambda}7231,7236 emission lines in objects as faint as m_{lambda}7400_~18. The work is motivated by the recent serendipitous discovery in the LMC of the first confirmed extragalactic [WC11] star, whose spectrum is dominated by CII emission, and the realization that the number of such objects is currently largely unconstrained. The survey, which imaged ~50deg^2^ using on-band and off-band filters, will significantly increase the total census of these rare stars. In addition, each new LMC [WC] star has a known luminosity, a quantity quite uncertain in the Galactic sample. Multiple known CII emitters were easily recovered, validating the survey design. We find 38 new CII emission candidates; spectroscopy of the complete sample will be needed to ascertain their nature. In a preliminary spectroscopic reconnaissance, we observed three candidates, finding CII emission in each. One is a new [WC11]. Another shows both the narrow CII emission lines characteristic of a [WC11], but also broad emission of CIV, OV, and HeII characteristic of a much hotter [WC4] star; we speculate that this is a binary [WC]. The third object shows weak CII emission, but the spectrum is dominated by a dense thicket of strong absorption lines, including numerous OII transitions. We conclude it is likely an unusual hot, hydrogen-poor post-AGB star, possibly in transition from [WC] to white dwarf. Even lacking a complete spectroscopic program, we can infer that late [WC] stars do not dominate the central stars of LMC planetary nebulae, and that the detected CII emitters are largely of an old population.
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/3173
- Title:
- Circumnuclear star-forming regions
- Short Name:
- J/MNRAS/451/3173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometry in U, B, V, R and I continuum bands and in H{alpha} and H{beta} emission lines for a sample of 336 circumnuclear star-forming regions located in early-type spiral galaxies with different levels of activity in their nuclei. They are nearby galaxies, with distances less than 100Mpc, 60 per cent of which are considered as interacting objects. This survey of 20 nuclear rings aims to provide insight into their star formation properties as age, stellar population and star formation rate. Extinction-corrected H{alpha} luminosities range from 1.3x10^38^ to 4x10^41^erg/s, with most of the regions showing values between 39.5<=logL_H{alpha}_<=40, which implies masses for the ionizing clusters higher than 2x10^5^M_{sun}_. H{alpha} and H{beta} images have allowed us to obtain an accurate measure of extinction. We have found an average value of A_V_=1.85 mag. (U-B) colour follows a two maximum distribution around (U-B)=~-0.7, and -0.3; (R-I) also presents a bimodal behaviour, with maximum values of 0.6 and 0.9. Reddest (U-B) and (R-I) regions appear in non-interacting galaxies. Reddest (R-I) regions lie in strongly barred galaxies. For a significant number of HII regions, the observed colours and equivalent widths are not well reproduced by single burst evolutionary theoretical models.
- ID:
- ivo://CDS.VizieR/J/AJ/119/3026
- Title:
- Circumstellar disk candidates in Orion
- Short Name:
- J/AJ/119/3026
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an optical study of four 45'x45' fields centered ~0.5{deg} east, west, north, and south of the Orion Nebula Cluster center. We have measured V and I_C_ photometry for ~5000 stars, and U photometry for ~1600 of these. We have obtained spectral classifications for ~300 of the stars with UVI_C_ photometry plus an additional ~200 stars located outside the area of our photometric survey. Dereddened photometry allows us to investigate the evidence for circumstellar accretion disks from excess emission at ultraviolet wavelengths, as well as the mass and age distributions of our sample. We find ~230 active accretion disk candidates and estimate the accretion disk fraction at >~40%. We use the magnitude of the ultraviolet excess to infer disk accretion rates. The mass accretion rate (dM/dt) decreases slowly with age over the limited age range spanned by our data, 1-3Myr, and increases slowly with mass over the limited mass range 0.2-1.2 M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AJ/135/966
- Title:
- Circumstellar disk evolution in NGC 2068/71
- Short Name:
- J/AJ/135/966
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the disk and accretion properties of young stars in the NGC 2068 and NGC 2071 clusters. Using low-resolution optical spectra, we define a membership sample and determine an age for the region of ~2Myr. Using high-resolution spectra of the H{alpha} line we study the accretion activity of these likely members and also examine the disk properties of the likely members using IRAC and MIPS mid-infrared photometry. A substantial fraction (79%) of the 67 members have an infrared excess while all of the stars with significant infrared excess show evidence for active accretion. We find three populations of evolved disks (IRAC weak, MIPS weak, and transition disks) all of which show decreased accretion activity in addition to the evidence for evolution in the dust disk.
