- ID:
- ivo://CDS.VizieR/J/MNRAS/469/4341
- Title:
- Seven recent novae BVI light curves
- Short Name:
- J/MNRAS/469/4341
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The BVI light curves of seven recent novae (i.e. V1534 Sco, V1535 Sco, V2949 Oph, V3661 Oph, MASTER OT J010603.18-744715.8, TCP J18102829-2729590 and ASASSN-16ma) have been extensively mapped with daily robotic observations from Atacama (Chile): five belong to the Galactic bulge, one to the Small Magellanic Cloud and another is a Galactic disc object. The two programme novae detected in {gamma}-rays by Fermi-LAT (i.e. TCP J18102829-2729590 and ASASSN-16ma) are bulge objects with unevolved companions. They distinguish themselves by showing a double-component optical light curve. The first component to develop is the fireball from freely expanding, ballistic-launched ejecta, with a time of passage through maximum that is strongly dependent on wavelength (~1d delay between the B and I bands). The second component, emerging simultaneously with the nova detection in {gamma}-rays, evolves at a slower pace, its optical brightness being proportional to the {gamma}-ray flux, and its passage through maximum not dependent on wavelength. The fact that {gamma}-rays are detected at a flux level that differs by four times from novae at the distance of the bulge seems to suggest that {gamma}-ray emission is not a widespread property of normal novae. We discuss the advantages offered by high-quality photometric observations collected with only one telescope (as opposed to data provided by a number of different instruments). We also observe the effects of the wavelength dependence of fireball expansion, the recombination in the flashed wind of a giant companion, the subtle presence of hiccups and plateaus, and the super-soft X-ray emission and its switch-off. Four programme novae (V2949 Oph, V3661 Oph, TCP J18102829-2729590 and ASASSN-16ma) have normal dwarf companions: V1534 Sco contains an M3 III giant, V1535 Sco a K-type giant and MASTER OT J010603.18-744715.8 a subgiant. We also comment briefly on the maximum absolute magnitude relation with decline time (MMRD).
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/344/943
- Title:
- Sh 138 BVRIJHK photometry
- Short Name:
- J/A+A/344/943
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric and spectroscopic study of the compact HII region Sh 138 and its associated stellar cluster. The positions and BVRIJHK magnitudes are obtained for more than 400 stars over a field of about 4' square centred on the HII region. Sh 138 is excited by a cluster of young massive stars. At the cluster's very centre are at least four O-B2 stars separated by less than 4". The brightest of these, both in the visible and the near infrared, exhibits a spectrum similar to those of the more massive Herbig Ae/Be stars. This star, our No. 183, is overluminous by a factor of 2.5 in the visible and four in the near IR with respect to the O9.5V star required to account for the ionization level of the HII region. However star 183's position in the J-H versus H-K diagram does not indicate a near-IR excess. We suggest that this star is a young massive object belonging to a binary or multiple system. The stellar cluster associated with Sh 138 is very reminiscent of the Orion Trapezium cluster: it is centrally peaked around several massive stars, and is dense - more than 550stars/pc^2^ at its centre. The visual extinction in the cluster varies between 5mag and more than 35mag; large variations are observed over very small scales (for example, more than 20mag over less than 4" among the central massive stars).
- ID:
- ivo://CDS.VizieR/J/AJ/111/902
- Title:
- Short-period Cepheids
- Short Name:
- J/AJ/111/902
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBVRI data on 36 short-period (P<5days) Cepheids is given. The observing techniques and reduction procedures are described. A consistent set of finding charts, a set of standard stars for each Cepheid, and improved coordinates are also presented.
- ID:
- ivo://CDS.VizieR/J/AJ/158/68
- Title:
- Short-period variables in young open cluster Stock 8
- Short Name:
- J/AJ/158/68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present time-series photometry in the field of Stock 8 and identified 130 short-period variable stars. Twenty-eight main-sequence and 23 pre-main-sequence variables are found to be part of cluster Stock 8. The main-sequence variables are classified as slow pulsators of the B-type, {beta} Cep, and {delta} Scuti stars. Fourteen main-sequence stars could be new class variables as discussed by Mowlavi et al. (2013, J/A+A/554/A108) and Lata et al. (2011MNRAS.418.1346L; 2012MNRAS.427.1449L; 2014, J/MNRAS/442/273; 2016MNRAS.456.2505L). The age and mass of pre-main-sequence variables are found to be ~<5 Myr and in the mass range of 0.5-2.8 M_{sun}_, respectively. These pre-main-sequence stars could be T-Tauri variables. We have found 5 and 2 of 23 pre-main-sequence variables as classical T-Tauri stars and Herbig Ae/Be stars, respectively, whereas 16 pre-main-sequence stars are classified as weak-line T-Tauri stars.
- ID:
- ivo://CDS.VizieR/J/A+A/467/73
- Title:
- 3{sigma} hard sample of XMDS survey
- Short Name:
- J/A+A/467/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our goal is to probe the populations of obscured and unobscured AGN investigating their optical-IR and X-ray properties as a function of X-ray flux, luminosity and redshift within a hard X-ray selected sample with wide multiwavelength coverage. We selected a sample of 136 X-ray sources detected at a significance of >=3{sigma} in the 2-10keV band (F_2-10_>~10^-14^erg/cm^2^/s) in a ~1deg^2^ area in the XMM Medium Deep Survey (XMDS, Cat. <J/A+A/439/413>). The XMDS area is covered with optical photometry from the VVDS and CFHTLS surveys and infrared Spitzer data from the SWIRE survey. Based on the X-ray luminosity and X-ray to optical ratio, 132 sources are likely AGN, of which 122 have unambiguous optical - IR identification. The observed optical and IR spectral energy distributions of all identified sources are fitted with AGN/galaxy templates in order to classify them and compute photometric redshifts. X-ray spectral analysis is performed individually for sources with a sufficient number of counts and using a stacking technique for subsamples of sources at different flux levels. Hardness ratios are used to estimate X-ray absorption in individual weak sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/36
- Title:
- {sigma} Orionis cluster stellar population
- Short Name:
- J/ApJ/794/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic survey of the stellar population of the {sigma} Orionis cluster. We have obtained spectral types for 340 stars. Spectroscopic data for spectral typing come from several spectrographs with similar spectroscopic coverage and resolution. More than half of the stars in our sample are members confirmed by the presence of lithium in absorption, strong H{alpha} in emission or weak gravity-sensitive features. In addition, we have obtained high-resolution (R~34000) spectra in the H{alpha} region for 169 stars in the region. Radial velocities were calculated from this data set. The radial velocity distribution for members of the cluster is in agreement with previous work. Analysis of the profile of the H{alpha} line and infrared observations reveals two binary systems or fast rotators that mimic the H{alpha} width expected in stars with accretion disks. On the other hand, there are stars with optically thick disks and narrow H{alpha} profiles not expected in stars with accretion disks. This contribution constitutes the largest homogeneous spectroscopic data set of the {sigma} Orionis cluster to date.
- ID:
- ivo://CDS.VizieR/J/MNRAS/466/1963
- Title:
- Silicate crystallinities of O-rich evolved stars
- Short Name:
- J/MNRAS/466/1963
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For decades ever since the early detection in the 1990s of the emission spectral features of crystalline silicates in oxygen-rich evolved stars, there is a long-standing debate on whether the crystallinity of the silicate dust correlates with the stellar mass-loss rate. To investigate the relation between the silicate crystallinities and the mass-loss rates of evolved stars, we carry out a detailed analysis of 28 nearby oxygen-rich stars. We derive the mass-loss rates of these sources by modelling their spectral energy distributions from the optical to the far-infrared. Unlike previous studies in which the silicate crystallinity was often measured in terms of the crystalline-to-amorphous silicate mass ratio, we characterize the silicate crystallinities of these sources with the flux ratios of the emission features of crystalline silicates to that of amorphous silicates. This does not require the knowledge of the silicate dust temperatures, which are the major source of uncertainties in estimating the crystalline-to-amorphous silicate mass ratio. With a Pearson correlation coefficient of ~-0.24, we find that the silicate crystallinities and the mass-loss rates of these sources are not correlated. This supports the earlier findings that the dust shells of low mass-loss rate stars can contain a significant fraction of crystalline silicates without showing the characteristic features in their emission spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A75
- Title:
- Six luminous red novae photometry
- Short Name:
- J/A+A/630/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present extensive datasets for a class of intermediate-luminosity optical transients known as "luminous red novae" (LRNe). They show doublepeaked light curves, with an initial rapid luminosity rise to a blue peak (at -13 to -15mag), which is followed by a longer-duration red peak that sometimes is attenuated, resembling a plateau. The progenitors of three of them (NGC4490-2011OT1, M101-2015OT1, and SNhunt248), likely relatively massive blue to yellow stars, were also observed in a pre-eruptive stage when their luminosity was slowly increasing. Early spectra obtained during the first peak show a blue continuum with superposed prominent narrow Balmer lines, with P Cygni profiles. Lines of FeII are also clearly observed, mostly in emission. During the second peak, the spectral continuum becomes much redder, H{alpha} is barely detected, and a forest of narrow metal lines is observed in absorption. Very late-time spectra (~6 months after blue peak) show an extremely red spectral continuum, peaking in the infrared (IR) domain. H{alpha} is detected in pure emission at such late phases, along with broad absorption bands due to molecular overtones (such as TiO, VO). We discuss a few alternative scenarios for LRNe. Although major instabilities of single massive stars cannot be definitely ruled out, we favour a common envelope ejection in a close binary system, with possibly a final coalescence of the two stars. The similarity between LRNe and the outburst observed a few months before the explosion of the Type IIn SN 2011ht is also discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/777/97
- Title:
- SL2S galaxy-scale lens sample. III.
- Short Name:
- J/ApJ/777/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Hubble Space Telescope (HST) imaging data and Canada-France-Hawaii Telescope (CFHT) near-infrared ground-based images for the final sample of 56 candidate galaxy-scale lenses uncovered in the CFHT Legacy Survey as part of the Strong Lensing in the Legacy Survey (SL2S) project. The new images are used to perform lens modeling, measure surface photometry, and estimate stellar masses of the deflector early-type galaxies (ETGs). Lens modeling is performed on the HST images (or CFHT when HST is not available) by fitting the spatially extended light distribution of the lensed features assuming a singular isothermal ellipsoid mass profile and by reconstructing the intrinsic source light distribution on a pixelized grid. Based on the analysis of systematic uncertainties and comparison with inference based on different methods, we estimate that our Einstein radii are accurate to ~3%. HST imaging provides a much higher success rate in confirming gravitational lenses and measuring their Einstein radii than CFHT imaging does. Lens modeling with ground-based images, however, when successful, yields Einstein radius measurements that are competitive with space-based images. Information from the lens models is used together with spectroscopic information from companion Paper IV (2013ApJ...777...98S) to classify the systems, resulting in a final sample of 39 confirmed (grade A) lenses and 17 promising candidates (grade B,C).
- ID:
- ivo://CDS.VizieR/J/A+A/564/A31
- Title:
- SMC blob N26 multiband photometry
- Short Name:
- J/A+A/564/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-excitation compact HII regions of the Magellanic Clouds are sites of recent massive star formation in low metallicity environments. Detailed study of these regions and their environments using high-spatial resolution observations is necessary to better understand massive star formation, which is still an unsolved problem. We aim at a detailed study of the Small Magellanic Cloud compact HII region N26, which is only ~4" in diameter. This study is based on high spatial resolution imaging (~0.1"-0.3") in JHKs and L' bands, using the VLT equipped with the NAOS adaptive optics system. A larger region (~50pcx76pc) was also imaged at medium spatial resolution, using the ESO 2.2m telescope in optical wavelengths. We also used the JHKs archival data from the IRSF survey and the Spitzer Space Telescope SAGE-SMC survey.
