- ID:
- ivo://CDS.VizieR/J/A+A/590/A116
- Title:
- Nainital-Cape Survey. IV.
- Short Name:
- J/A+A/590/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Nainital-Cape Survey is a dedicated ongoing Survey programme to search for and study pulsational variability in chemically peculiar (CP) stars to understand their internal structure and evolution. The main aims of this Survey are to find new pulsating Ap and Am stars in the northern and southern hemisphere and to perform asteroseismic studies of these new pulsators. The Survey is conducted using high-speed photometry. The candidate stars were selected on the basis of having Stromgren photometric indices similar to those of known pulsating CP stars. Over the last decade a total of 337 candidate pulsating CP stars were observed for the Nainital-Cape Survey, making it one of the longest ground-based surveys for pulsation in CP stars in terms of time span and sample size. The previous papers of this series presented seven new pulsating variables and 229 null results. In this paper we present the light curves, frequency spectra and various astrophysical parameters of the 108 additional CP stars observed since the last reported results. We also tabulated the basic physical parameters of the known roAp stars. As a part of establishing the detection limits in the Nainital-Cape Survey, we investigated the scintillation noise level at the two observing sites used in this Survey, Sutherland and Nainital, by comparing the combined frequency spectra stars observed from each location. Our analysis shows that both the sites permit the detection of variations of the order of 0.6-milli-magnitude (mmag) in the frequency range 1-4mHz, Sutherland is on average marginally better.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/520/A57
- Title:
- New FeII energy levels from stellar spectra
- Short Name:
- J/A+A/520/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectra of B-type and early A-type stars show numerous unidentified lines in the whole optical range, especially in the 5100-5400{AA} interval. Because FeII transitions to high energy levels should be observed in this region, we used semiempirical predicted wavelengths and gf-values of FeII to identify unknown lines. Semiempirical line data for FeII computed by Kurucz are used to synthesize the spectrum of the slow-rotating, Fe - overabundant CP star HR6000.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A10
- Title:
- New MnII energy levels
- Short Name:
- J/A+A/580/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The NIST database lists several MnI lines that were observed in the laboratory but not classified. They cannot be used in spectrum synthesis because their atomic line data are unknown. These lines are concentrated in the 2380-2700{AA} interval. We aimed to assign energy levels and loggf values to these lines. Semi-empirical line data for MnII computed by Kurucz were used to synthesize the ultraviolet spectrum of the slow-rotating, HgMn star HD 175640. The spectrum was compared with the high-resolution spectrum observed with the HST-STIS equipment. A UVES spectrum covering the 3050-10000{AA} region was also examined.
- ID:
- ivo://CDS.VizieR/J/AJ/152/104
- Title:
- New photometrically variable magnetic CP stars
- Short Name:
- J/AJ/152/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The magnetic Ap or CP2 stars are natural atomic and magnetic laboratories. Strictly periodic changes are observed in the spectra and brightness of these stars, which allow the derivation of rotational periods. Related to this group of objects are the He-weak (CP4) and He-rich stars, some of which also undergo brightness changes due to rotational modulation. Increasing the sample size of known rotational periods among CP2/4 stars is important and will contribute to our understanding of these objects and their evolution in time. We have compiled an extensive target list of CP2/4 stars from the General Catalog of Ap, HgMn, and Am stars, including several early-type (spectral types B/A) variables of undetermined type from the International Variable Star Index. We investigated our sample stars using publicly available observations from the ASAS-3 archive. Our previous efforts in this respect led to the discovery of 323 variable stars. Using a refined analysis approach, we were able to identify another 360 stars exhibiting photometric variability in ASAS-3 data. Summary data, folded light curves and, if available, information from the literature are presented for our final sample, which is composed of 334 bona-fide {alpha}^2^ Canum Venaticorum (ACV) variables, 23 ACV candidates, and 3 eclipsing binary systems. Interesting and unusual objects are discussed in detail. In particular, we call attention to HD66051 (V414 Pup), which is an eclipsing binary system showing obvious rotational modulation of the light curve due to the presence of an ACV variable in the system.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A14
- Title:
- New R Coronae Borealis stars
- Short Name:
- J/A+A/635/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue contains 2356 entries. It was created to list targets of interest that have similar near- and mid-infrared characteristics than R Coronae Borealis (RCB) stars which are hydrogen-deficient carbon-rich supergiant stars known to possess warm circumstellar shells. It is therefore a catalogue enriched in such objects and further spectroscopic follow-ups are needed to reveal the true nature of each target. The catalogue was produced from a series of selection criteria on the infrared colours and brightness of sources published in the WISE All-Sky data release, and also listed in the 2MASS catalogue. These sources spread over the entire sky. The selection criteria are described in section 2 of the paper.
- ID:
- ivo://CDS.VizieR/J/A+AS/133/1
- Title:
- New variable chemically peculiar stars
- Short Name:
- J/A+AS/133/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since variability of chemically peculiar (CP) stars plays an important role for the astrophysical explanation of their outstanding behaviour, we have identified new variable CP stars listed in Renson's catalogue using the extensive Hipparcos Variability Annex. From the 293 objects found, 33 were excluded because they are not CP stars and/or have no period listed, half of the remaining stars are newly identified and half had been already included in the catalogue of variable CP stars by Catalano & Renson (1997, Cat. <J/A+AS/121/57>). Most of the newly identified variability is due to an apparent magnetic field coupled with stellar rotation (oblique rotator model). The constraints of this model are fulfilled for all but three CP2 stars. Variations of bona fide Am-Fm stars are exclusively explained by eclipses of binary systems. Furthermore eight candidates of the gamma Doradus group (pulsating Am-Fm stars) were detected. Table 1 (table1.dat) presents the newly identified chemically peculiar stars.
- ID:
- ivo://CDS.VizieR/J/A+A/373/987
- Title:
- Non-LTE Ga abundance in HgMn stars
- Short Name:
- J/A+A/373/987
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present, for the first time, the Non-LTE gallium equivalent widths for the most prominent gallium transitions as identified in real spectra and in (hot) mercury-manganese star. The common feature of the departure coefficients is to decrease near the stellar surface, the collision rates are dominant in many cases and the Non-LTE equivalent widths are generally smaller. In particular, the abundance difference as derived from UV and visual lines is reduced. The photoionization cross sections were computed by means of standard R-matrix formalism.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/74.55
- Title:
- Ori OB1 CP stars magnetic fields. III.
- Short Name:
- J/other/AstBu/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper presents results of magnetic field measurements of 10 chemically peculiar stars of subgroup (a) in the Orion OB1 association: HD33917, HD34859, HD35008, HD35039, HD35177, HD35575, HD35730, HD36549, HD38912, and HD294046. Observations were carried out with the circular polarization analyzer at the Main Stellar Spectrograph at the 6-m SAO RAS telescope.Magnetic fields were detected in four stars, six stars have magnetic fields below the detection threshold.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/76.163
- Title:
- Ori OB1 CP stars magnetic fields. V.
- Short Name:
- J/other/AstBu/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper presents the results of magnetic field measurements of 27 chemically peculiar stars in subgroups (c) and (d) of the Orion OB1 association. In total, more than 140 circularly polarized spectra were obtained and measured in the period from 2013 to 2020. An analysis of the results showed that 13 out of 24 CP stars in subgroup (c) have a magnetic field. At the same time, no field of a significant strength was found in any of the three CP stars in subgroup (d). We found that the occurrence of magnetic stars in subgroup (c), whose average age is approximately 5Myr, lies in the middle between the occurrence of magnetic stars in subgroups (a) with an age of 10 Myr and (b), whose age is about 2Myr. Our results indicate a sharp decrease in the occurrence of magnetic CP stars and a simultaneous decrease in their magnetic field with age. The data obtained with the example of the Orion OB1 association generally support the theory of the fossil origin of the magnetic field of chemically peculiar stars; however, the process of the field formation itself can have a number of features manifesting observationally.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/76.39
- Title:
- Ori OB1 CP stars magnetic fields. V.
- Short Name:
- J/other/AstBu/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper presents magnetic field measurements for 15 chemically peculiar (CP) stars of subgroup 1b in the Orion OB1 association. We have found that the proportion of stars with strong magnetic fields among these 15 CP stars is almost twice as large as in subgroup 1a. Along with this, the age of subgroup 1b is estimated as 2Myr, and the age of subgroup 1a is in the order of 10Myr. The average root-mean-square magnetic field <Be> (all) for stars in subgroup 1b is 2.3 times higher than that for stars in subgroup 1a. The conclusions obtained fall within the concept of the fossil origin of large-scale magnetic fields in B and A stars, but the rate of field weakening with age appears anomalously high. We present our results as an important observational test for calibrating the theory of stellar magnetic field formation and evolution.
