- ID:
- ivo://CDS.VizieR/J/A+A/640/A128
- Title:
- Cygnus OB2 association NIR light curves
- Short Name:
- J/A+A/640/A128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a J, H, and K photometric variability survey of the central 0.78 square degrees of the young OB association Cygnus OB2. We used data observed with the Wide-Field CAMera at the United Kingdom Infrared Telescope in 2007 (spanning 217 days) to investigate the light curves of 5083 low mass candidate members in the association and explore the occurrence and main characteristics of their near-infrared variability. We identified 2529 stars (~50% of the sample) with significant variability with time-scales ranging from days to months. We classified the variable stars into the following three groups according to their light curve morphology: periodic variability (1697 stars), occultation variability (124 stars), and other types of variability (726 stars). We verified that the disk-bearing stars in our sample are significantly more variable in the near-infrared than diskless stars, with a steep increase in the disk-fraction among stars with higher variability amplitude. We investigated the trajectories described by variable stars in the color-space and measured slopes for 335 stars describing linear trajectories. Based on the trajectories in the color-space, we inferred that the sample analyzed is composed of a mix of young stars presenting variability due to hot and cold spots, extinction by circumstellar material, and changes in the disk emission in the near-infrared. We contemplated using the use of near- infrared variability to identify disk-bearing stars and verified that 53.4% of the known disk-bearing stars in our sample could have been identified as such based solely on their variability. We present 18 newly identified disk- bearing stars and 14 eclipsing binary candidates among CygOB2 lower-mass members.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/612/A26
- Title:
- Deep HI observations of Leo T with WSRT
- Short Name:
- J/A+A/612/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Leo T is the lowest mass gas-rich galaxy currently known and studies of its gas content help us understand how such marginal galaxies survive and form stars. We present deep neutral hydrogen (HI) observations from the Westerbork Synthesis Radio Telescope in order to understand its HI distribution and potential for star formation. We find a larger HI line flux than the previously accepted value, resulting in a 50% larger HI mass of 4.1x10^5^M_{sun}_. The additional HI flux is from low surface brightness emission that was previously missed; with careful masking this emission can be recovered even in shallower data.We perform a Gaussian spectral decomposition to find a cool neutral medium component (CNM) with a mass of 3.7x10^4^M_{sun}_, or almost 10% of the total HI mass. Leo T has no HI emission extending from the main HI body, but there is evidence of interaction with the Milky Way circumgalactic medium in both a potential truncation of the HI body and the offset of the peak HI distribution from the optical center. The CNM component of Leo T is large when compared to other dwarf galaxies, even though Leo T is not currently forming stars and has a lower star formation efficiency than other gas-rich dwarf galaxies. However, the HI column density associated with the CNM component in Leo T is low. One possible explanation is the large CNM component is not related to star formation potential but rather a recent, transient phenomenon related to the interaction of Leo T with the Milky Way circumgalactic medium.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A91
- Title:
- Deep VI imaging in outer regions of M33
- Short Name:
- J/A+A/533/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Subaru/Suprime-Cam deep V and I imaging of seven fields in the outer regions of M33. Our aim is to search for stellar structures corresponding to extended HI clouds found in a recent 21-cm survey of the galaxy. Three fields probe a large HI complex to the southeastern (SE) side of the galaxy. An additional three fields cover the northwestern (NW) side of the galaxy along the HI warp. A final target field was chosen further north, at a projected distance of approximately 25kpc, to study part of the large stellar plume recently discovered around M33. We analyse the stellar population at R>10kpc by means of V, I colour magnitude diagrams reaching the red clump. We constrain the age and metallicity of the different stellar populations, search for density enhancements that correspond to the HI features, and investigate the radial surface distribution of the stars. We find evolved stellar populations in all fields out to 120' (~30kpc), while a diffuse population of young stars (~200Myr) is detected out to a galactocentric radius of 15kpc. The mean metallicity in the southern fields remains approximately constant at [M/H]=-0.7 beyond the edge of the optical disc, from 40' out to 80'. Along the northern fields probing the outer HI disc, we also find a metallicity of [M/H]=-0.7 between 35' and 70' from the centre, which decreases to [M/H]=-1.0 at larger angular radii out to 120'. In the northernmost field, outside the disc extent, the stellar population of the large stellar plume possibly related to a M33-M31 interaction is on average more metal-poor ([M/H]=-1.3) and older (>6Gyr). An exponential disc with a large scale-length (~7kpc) fits well the average distribution of stars detected in both the SE and NW regions from a galactocentric distance of 11kpc out to 30kpc. The stellar disc extends beyond the HI disc. The stellar distribution at large radii is disturbed and, although there is no clear correlation between the stellar substructures and the location of the HI clouds, this gives evidence of tidal interaction or accretion events.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A30
- Title:
- Detection of fast HI outflow in Mrk231
- Short Name:
- J/A+A/593/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the detection, performed with the Westerbork Synthesis Radio Telescope (WSRT) and the Karl Jansky Very Large Array (VLA), of a fast HI 21-cm outflow in the ultra-luminous infrared galaxy Mrk 231. The outflow is observed as shallow HI absorption blueshifted ~1300 km/s with respect to the systemic velocity and located against the inner kpc of the radio source. The outflowing gas has an estimated column density between 5 and 15x10^18^Tspin.cm^-2^. We derive the Tspin to lie in the range 400-2000 K and the corresponding HI densities are n_HI_~10-100cm^-3^. We also obtained deeper continuum images than previously available. They confirm the complex structure of the radio continuum originating both from the AGN and star formation. At the resolution obtained with the VLA (~1-arcsec) we do not see a kpc-scale jet. Instead, we detect a plateau of emission, likely due to star formation, surrounding the bright nuclear region. We also detect a poorly collimated bridge which may represent the channel feeding the southern lobe. The unprecedented depth of the low-resolution WSRT image reveals radio emission extending 50-arcsec (43kpc) to the south and 20arcsec (17kpc) to the north.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/2653
- Title:
- 8620 DIB equivalent width and extinction
- Short Name:
- J/MNRAS/463/2653
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young stellar cluster Westerlund 1 (Wd 1: l=339.6, b=-0.4) is one of the most massive in the local Universe, but accurate parameters are pending on better determination of its extinction and distance. Based on our photometry and data collected from other sources, we have derived a reddening law for the cluster line-of-sight representative of the Galactic plane (-5{deg}<b<+5{deg}) in the window 0.4-4.8um. The power-law exponent alpha=2.13+/-0.08 is much steeper than those published a decade ago (1.6-1.8) and our index RV=2.50+/-0.04 also differs from them, but in very good agreement with recent works based on deep surveys in the inner Galaxy. As a consequence, the total extinction AKs=0.74+/-0.08 (AV=11.40+/-2.40) is substantially smaller than previous results (0.91-1.13), part of which (AKs=0.63 or AV=9.66) is from the interstellar medium. The extinction in front of the cluster spans a range of AV~8.7 with a gradient increasing from SW to NE across the cluster face, following the same general trend of warm dust distribution. The map of the J-Ks colour index also shows a trend of reddening in this direction. We measured the equivalent width of the diffuse interstellar band at 8620 A (the 'GAIA DIB') for Wd 1 cluster members and derived the relation AKs=0.612EW-0.191EW^2^. This extends the Munari et al. relation, valid for E(B-V)<1, to the non-linear regime (AV>4).
- ID:
- ivo://CDS.VizieR/J/A+A/601/A76
- Title:
- DIRECT lightcurves of 21 luminous YSGs in M33
- Short Name:
- J/A+A/601/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of massive stars surviving the red supergiant (RSG) stage remains unexplored due to the rarity of such objects. The yellow hypergiants (YHGs) appear to be the warm counterparts of post-RSG classes located near the Humphreys-Davidson upper luminosity limit, which are characterized by atmospheric instability and high mass-loss rates. We aim to increase the number of YHGs in M33 and thus to contribute to a better understanding of the pre-supernova evolution of massive stars. Optical spectroscopy of five dust-enshrouded YSGs selected from mid-IR criteria was obtained with the goal of detecting evidence of extensive atmospheres. We also analyzed BVIc photometry for 21 of the most luminous YSGs in M33 to identify changes in the spectral type. To explore the properties of circumstellar dust, we performed SED-fitting of multi-band photometry of the 21 YSGs. We find three luminous YSGs in our sample to be YHG candidates, as they are surrounded by hot dust and are enshrouded within extended, cold dusty envelopes. Our spectroscopy of star 2 shows emission of more than one H{alpha} component, as well as emission of CaII, implying an extended atmospheric structure. In addition, the long-term monitoring of the star reveals a dimming in the visual light curve of amplitude larger than 0.5mag that caused an apparent drop in the temperature that exceeded 500K. We suggest the observed variability to be analogous to that of the Galactic YHG {rho} Cas. Five less luminous YSGs are suggested as post-RSG candidates showing evidence of hot or/and cool dust emission. We demonstrate that mid-IR photometry, combined with optical spectroscopy and time-series photometry, provide a robust method for identifying candidate YHGs. Future discovery of YHGs in Local Group galaxies is critical for the study of the late evolution of intermediate-mass massive stars.
- ID:
- ivo://CDS.VizieR/J/A+A/464/641
- Title:
- Double stars CCD photometry and astrometry. III
- Short Name:
- J/A+A/464/641
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent CCD observations were performed in the period 1998-2004 for a large sample of visual double and multiple stars selected from the Hipparcos Catalogue (Cat. <I/239>) and/or from the Gliese Catalogue of Nearby Stars (Cat. <V/70>). Accurate astrometric and photometric data allowing us to characterise the individual components are provided. These data are compared to Hipparcos data or to data from an older epoch to assess the nature of the observed systems. We simultaneously apply a Moffat-Lorentz profile with a similar shape to all detected components and adjust the profile parameters from which we obtain the relative astrometric position (epoch, position angle, angular separation) as well as differential multi-colour photometry (filters (B)VRI).
- ID:
- ivo://CDS.VizieR/J/A+A/463/503
- Title:
- Early-type dwarf galaxies in Fornax cluster
- Short Name:
- J/A+A/463/503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse the photometric properties of the early-type Fornax cluster dwarf galaxy population, based on a wide field imaging study of the central cluster area in V and I. We used the instrument/telescope combination IMACS/Magellan at Las Campanas Observatory. We create a fiducial sample of Fornax cluster dwarf ellipticals (dEs) in the following three steps: (1) To verify cluster membership, we measured I-band surface brightness fluctuation (SBF) distances to candidate dEs; (2) We re-assessed morphological classifications for candidate dEs too faint for SBF detection; and (3) We searched for new candidate dEs in the size-luminosity regime close to the resolution limit of previous surveys. (1) We confirm cluster membership for 28 candidate dEs in the range -16.6<M_V_<-10.1mag by means of SBF distances. We find no SBF background galaxy. (2) Of 51 further candidate dEs in the range -13.2<M_V_<-8.6mag, 2/3 are confirmed as probable cluster members by morphological re-assessment, while 1/3 are re-classified as probable background objects. (3) We find 12 new dE candidates in the range -12.3<M_V_<-8.8mag. The surface brightness-magnitude relation defined by the resulting fiducial dE sample shows that Fornax dEs are about 40% larger than Local Group dEs. The Fornax dE sample furthermore defines a colour-magnitude relation that appears slightly shallower than that of Local Group dEs. The early-type dwarf galaxy luminosity function in Fornax has a faint end slope alpha=-1.1+/- 0.1.
- ID:
- ivo://CDS.VizieR/J/MNRAS/292/499
- Title:
- EFAR photometric data
- Short Name:
- J/MNRAS/292/499
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present R-band CCD photometry for 776 galaxies observed in the EFAR (Elliptical FAR away) project. The photometry is compared with photoelectric data, showing that a common zero-point good to better than 1% and a precision of 0.03mag per zero-point have been achieved. We give the circularly averaged surface brightness profiles and the photometric parameters of the 762 program galaxies, D(n) diameters (at 20.5mag/arcsec^2^), half-luminosity radii Re, total magnitudes m_T_, and average effective surface brightnesses <SBe>. More than 80% of the profiles have a global S/N ratio larger than 300. The extrapolation needed to derive total magnitudes is less than 10% for 80% of the fits. More than 80% of the galaxies have mean effective surface brightness larger than the observed sky brightness. In 90% of the profiles the estimate of the contamination of the sky by the galaxy light is less than 1%. We derive total magnitudes and half-luminosity radii to better than 0.15mag and 25%, respectively, for 90% of our sample. In contrast, external comparisons show that data in the literature can be strongly affected by systematic errors due to large extrapolations, small radial range, sky subtraction errors, seeing effects, and the use of a simple R^1/4^ fit. The resulting errors can easily amount to more than 0.5mag in the total magnitudes and 50% in the half-luminosity radii.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A43
- Title:
- EPOCH Project. EROS-2 LMC periodic variables
- Short Name:
- J/A+A/566/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The EPOCH (EROS-2 periodic variable star classification using machine learning) project aims to detect periodic variable stars in the EROS-2 light curve database. In order to classify these variables, we first build a training set by compiling known variables in the Large Magellanic Could area from the OGLE and MACHO surveys. We crossmatch these variables with the EROS-2 sources and extract 22 variability features from 28,392 light curves of the corresponding EROS-2 sources. We then use Random Forests to classify the EROS-2 sources in the training set. We design the model to separate not only Delta Scuti stars, RR Lyraes, Cepheids, eclipsing binaries and long-period variables, the "superclasses", but also their subclasses, such as RRab, RRc, RRd and RRe for RR Lyraes, and similarly for the other variable types. We apply the trained model to the entire EROS-2 LMC database containing about 29 million sources and find 117,234 periodic variable candidates. Out of these 117,234 periodic variables, 55,285 have not been discovered by either OGLE or MACHO variability studies. This set comprises 1906 Delta Scuti stars, 6,607 RR Lyraes, 638 Cepheids, 178 Type II Cepheids, 34,562 eclipsing binaries and 11,394 long-period variables.
