- ID:
- ivo://CDS.VizieR/J/A+AS/146/323
- Title:
- RASS young sources around R CrA
- Short Name:
- J/A+AS/146/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the ROSAT All-Sky Survey data in a 126 deg^2^ area in and around the CrA star forming region. With low-resolution spectroscopy of unidentified ROSAT sources we could find 19 new pre-main sequence stars, two of which are classical T Tauri stars, the others being weak-lined. The spectral types of these new T Tauri stars range from F7 to M6. The two new classical T Tauri stars are located towards two small cloud-lets outside of the main CrA cloud. They appear to be ~10 Myrs old, by comparing their location in the H-R diagram with isochrones for an assumed distance of 130 pc, the distance of the main CrA dark cloud. The new off-cloud weak-line T Tauri stars may have formed in similar cloudlets, which have dispersed recently. High-resolution spectra of our new T Tauri stars show that they have significantly more lithium absorption than zero-age main-sequence stars of the same spectral type, so that they are indeed young. From those spectra we also obtained rotational and radial velocities. For some stars we found the proper motion in published catalogs. The direction and velocity of the 3D space motion - south relative to the galactic plane - of the CrA T Tauri stars is consistent with the dark cloud being formed originally by a high-velocity cloud impact onto the galactic plane, which triggered the star formation in CrA. We also present VRIJHK photometry for most of the new T Tauri stars to derive their luminosities, ages, and masses.
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- ID:
- ivo://CDS.VizieR/J/ApJ/820/33
- Title:
- R-band light curves of type II supernovae
- Short Name:
- J/ApJ/820/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- During the first few days after explosion, Type II supernovae (SNe) are dominated by relatively simple physics. Theoretical predictions regarding early-time SN light curves in the ultraviolet (UV) and optical bands are thus quite robust. We present, for the first time, a sample of 57 R-band SN II light curves that are well-monitored during their rise, with >5 detections during the first 10 days after discovery, and a well-constrained time of explosion to within 1-3 days. We show that the energy per unit mass (E/M) can be deduced to roughly a factor of five by comparing early-time optical data to the 2011 model of Rabinak & Waxman, while the progenitor radius cannot be determined based on R-band data alone. We find that SN II explosion energies span a range of E/M=(0.2-20)x10^51^erg/(10M_{sun}), and have a mean energy per unit mass of <E/M>=0.85x10^51^erg/(10M_{sun}), corrected for Malmquist bias. Assuming a small spread in progenitor masses, this indicates a large intrinsic diversity in explosion energy. Moreover, E/M is positively correlated with the amount of ^56^Ni produced in the explosion, as predicted by some recent models of core-collapse SNe. We further present several empirical correlations. The peak magnitude is correlated with the decline rate ({Delta}m_15_), the decline rate is weakly correlated with the rise time, and the rise time is not significantly correlated with the peak magnitude. Faster declining SNe are more luminous and have longer rise times. This limits the possible power sources for such events.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/56
- Title:
- R-band linear polarization of Gaia stars
- Short Name:
- J/ApJ/872/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The availability of large data sets with stellar distance and polarization information will enable a tomographic reconstruction of the (plane-of-the-sky-projected) interstellar magnetic field in the near future. We demonstrate the feasibility of such a decomposition within a small region of the diffuse interstellar medium (ISM). We combine measurements of starlight (R-band) linear polarization obtained using the RoboPol polarimeter with stellar distances from the second Gaia data release. The stellar sample is brighter than 17mag in the R-band and reaches out to several kiloparsecs from the Sun. HI emission spectra reveal the existence of two distinct clouds along the line of sight. We decompose the line-of-sight-integrated stellar polarizations to obtain the mean polarization properties of the two clouds. The two clouds exhibit significant differences in terms of column density and polarization properties. Their mean plane-of-the-sky magnetic field orientation differs by 60{deg}. We show how our tomographic decomposition can be used to constrain our estimates of the polarizing efficiency of the clouds as well as the frequency dependence of the polarization angle of polarized dust emission. We also demonstrate a new method to constrain cloud distances based on this decomposition. Our results represent a preview of the wealth of information that can be obtained from a tomographic map of the ISM magnetic field.
- ID:
- ivo://CDS.VizieR/J/ApJ/811/117
- Title:
- R-band PTF observations of SNe IIb
- Short Name:
- J/ApJ/811/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The progenitor stars of several Type IIb supernovae (SNe) show indications of extended hydrogen envelopes. These envelopes might be the outcome of luminous energetic pre-explosion events, so-called precursor eruptions. We use the Palomar Transient Factory (PTF) pre-explosion observations of a sample of 27 nearby SNe IIb to look for such precursors during the final years prior to the SN explosion. No precursors are found when combining the observations in 15-day bins, and we calculate the absolute-magnitude-dependent upper limit on the precursor rate. At the 90% confidence level, SNe IIb have on average <0.86 precursors as bright as an absolute R-band magnitude of -14 in the final 3.5 years before the explosion and <0.56 events over the final year. In contrast, precursors among SNe IIn have a >~5 times higher rate. The kinetic energy required to unbind a low-mass stellar envelope is comparable to the radiated energy of a few-weeks-long precursor that would be detectable for the closest SNe in our sample. Therefore, mass ejections, if they are common in such SNe, are radiatively inefficient or have durations longer than months. Indeed, when using 60-day bins, a faint precursor candidate is detected prior to SN 2012cs (~2% false-alarm probability). We also report the detection of the progenitor of SN 2011dh that does not show detectable variability over the final two years before the explosion. The suggested progenitor of SN 2012P is still present, and hence is likely a compact star cluster or an unrelated object.
- ID:
- ivo://CDS.VizieR/J/MNRAS/351/1401
- Title:
- RcIcZ photometry of NGC 2547
- Short Name:
- J/MNRAS/351/1401
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of RcIcZ photometry over an area of 0.855 square degrees, centred on the young open cluster NGC 2547. The survey is substantially complete to limits of Rc=21.5, Ic=19.5, Z=19.5. We use the catalogue to define a sample of NGC 2547 candidates with model-dependent masses of about 0.05-1.0M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/376/561
- Title:
- Rc light curves of 7 variables in M37
- Short Name:
- J/A+A/376/561
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A CCD photometric study of the dense galactic open cluster M 37 is discussed. The majority of the analysed data have been obtained through an R_C_ filter in order to collect time-series measurements. The observations were carried out on seven nights between December 1999 and February 2000, and have led to the discovery of 7 new variable stars in the field. Three of them have been unambiguously identified as W UMa-type eclipsing binaries, while two more are monoperiodic pulsating stars, most probably high-amplitude {delta} Scuti-type variables. Two stars seem to be long-period eclipsing binaries without firm period determination. The individual light curve data are presented here.
- ID:
- ivo://CDS.VizieR/J/AN/333/242
- Title:
- Recent photometry of symbiotic stars
- Short Name:
- J/AN/333/242
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new multicolour (U,B,V,Rc,Ic) photometric observations of classical symbiotic stars, EG And, Z And, BF Cyg, CH Cyg, CI Cyg, V1329 Cyg, TX CVn, AG Dra, Draco C1, AG Peg and AX Per, carried out between 2007.1 and 2011.9. The aim of this paper is to present new data of our monitoring programme, to describe the main features of their light curves (LC) and to point problems for their future investigation. The data were obtained by the method of the classical photoelectric and CCD photometry.
- ID:
- ivo://CDS.VizieR/J/MNRAS/418/2054
- Title:
- Recession velocities for fossil galaxy groups
- Short Name:
- J/MNRAS/418/2054
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Defined as X-ray bright galaxy groups with large differences between the luminosities of their brightest and second brightest galaxies, "fossil groups" are believed to be some of the oldest galaxy systems in the Universe. They have therefore been the subject of much recent research. In this work we present a study of 10 fossil group candidates with an average of 33 spectroscopically confirmed members per group, making this the deepest study of its type to date. We also use these data to perform an analysis of the luminosity function of our sample of fossil groups.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A14
- Title:
- Reclassification of Cepheids in the Gaia DR2
- Short Name:
- J/A+A/625/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Classical Cepheids are the most important primary indicators for the extragalactic distance scale. Establishing the precise zero points of their Period-Luminosity and Period-Wesenheit (PL/PW) relations has profound consequences on the estimate of H_0_. Type II Cepheids are also important distance indicator and tracers of old stellar populations. The recent Data Release 2 (DR2) of the Gaia Spacecraft includes photometry and parallaxes for thousands of classical and type II cepheids. We aim at reviewing the classification of Gaia DR2 Cepheids and to derive precise PL/PW for Magellanic Cloud (MCs) and Galactic Cepheids. Information from the literature and the Gaia astrometry and photometry are adopted to assign DR2 Galactic Cepheids to the classes: Classical, Anomalous and Type II Cepheids. We re-classify the DR2 Galactic Cepheids and derive new precise PL/PW relations in the Gaia passbands for the MCs and Milky Way Cepheids. We investigated for the first time the dependence on metallicity of the PW relation for Classical Cepheids in the Gaia} bands, finding non-conclusive results. According to our analysis, the zero point of the Gaia DR2 parallaxes as estimated from Classical and Type II Cepheids seems to be likely underestimated by ~0.07mas, in full agreement with recent literature. The next Gaia data releases are expected to fix this zero point offset to eventually allow a determination of H_0_ to less than 1%.
- ID:
- ivo://CDS.VizieR/J/ApJ/721/L28
- Title:
- Red clump stars in Galactic Bulge from OGLE-III
- Short Name:
- J/ApJ/721/L28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The red clump (RC) is found to be split into two components along several sightlines toward the Galactic bulge. This split is detected with high significance toward the areas (-3.5<l<1,b<-5) and (l,b)=(0,+5.2), i.e., along the bulge minor axis and at least 5 deg off the plane. The fainter (hereafter "main") component is the one that more closely follows the distance-longitude relation of the bulge RC. The main component is ~0.5mag fainter than the secondary component and with an overall approximately equal population. For sightlines further from the plane, the difference in brightness increases, and more stars are found in the secondary component than in the main component. The two components have very nearly equal (V-I) color.
