- ID:
- ivo://CDS.VizieR/J/AJ/152/62
- Title:
- Revised LGGS UBVRI photometry of M31 and M33 stars
- Short Name:
- J/AJ/152/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe our spectroscopic follow-up to the Local Group Galaxy Survey (LGGS) photometry of M31 and M33. We have obtained new spectroscopy of 1895 stars, allowing us to classify 1496 of them for the first time. Our study has identified many foreground stars, and established membership for hundreds of early- and mid-type supergiants. We have also found nine new candidate luminous blue variables and a previously unrecognized Wolf-Rayet star. We republish the LGGS M31 and M33 catalogs with improved coordinates, and including spectroscopy from the literature and our new results. The spectroscopy in this paper is responsible for the vast majority of the stellar classifications in these two nearby spiral neighbors. The most luminous (and hence massive) of the stars in our sample are early-type B supergiants, as expected; the more massive O stars are more rare and fainter visually, and thus mostly remain unobserved so far. The majority of the unevolved stars in our sample are in the 20-40M_{Sun}_ range.
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- ID:
- ivo://CDS.VizieR/J/ApJ/518/859
- Title:
- Revision of MK luminosity classes
- Short Name:
- J/ApJ/518/859
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hipparcos parallaxes of cool giants are utilized in two ways in this paper. First, a plot of reduced parallaxes of stars brighter than 6.5, as a function of spectral type, for the first time separates members of the clump from stars in the main giant ridge. A slight modification of the MK luminosity standards has been made so that luminosity class IIIb defines members of the clump, and nearly all of the class III stars fall within the main giant ridge. Second, a new calibration of MK luminosity classes III and IIIb in terms of visual absolute magnitudes has been made.
- ID:
- ivo://CDS.VizieR/J/MNRAS/508/2370
- Title:
- Revisiting the Cygnus OB associations
- Short Name:
- J/MNRAS/508/2370
- Date:
- 24 Jan 2022 09:16:32
- Publisher:
- CDS
- Description:
- OB associations play an important role in Galactic evolution, though their origins and dynamics remain poorly studied, with only a small number of systems analysed in detail. In this paper we revisit the existence and membership of the Cygnus OB associations. We find that of the historical OB associations only Cyg OB2 and OB3 stand out as real groups. We search for new OB stars using a combination of photometry, astrometry, evolutionary models and an SED fitting process, identifying 4680 probable OB stars with a reliability of >90%. From this sample we search for OB associations using a new and flexible clustering technique, identifying 6 new OB associations. Two of these are similar to the associations Cyg OB2 and OB3, though the others bear no relationship to any existing systems. We characterize the properties of the new associations, including their velocity dispersions and total stellar masses, all of which are consistent with typical values for OB associations. We search for evidence of expansion and find that all are expanding, albeit anistropically, with stronger and more significant expansion in the direction of Galactic longitude. We also identify two large-scale (160pc and 25km/s) kinematic expansion patterns across the Cygnus region, each including three of our new associations, and attribute this to the effects of feedback from a previous generation of stars. This work highlights the need to revisit the existence and membership of the historical OB associations, if they are to be used to study their properties and dynamics.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A48
- Title:
- rho Cas differential BVRI photometry
- Short Name:
- J/A+A/631/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to explore the variable photometric and stellar properties of four yellow hypergiants (YHGs), HR 8752, HR 5171A, rho Cas, and HD 179821, and their pulsations of hundreds of days, and long-term variations (LTVs) of years. We also aim to explore light and colour curves for characteristics betraying evolutionary loops and eruptive episodes and to investigate trends of quasi-periods and the possible need for distance revisions. We tackled multi-colour and visual photometric data sets, looked for photometric indications betraying eruptions or enhanced mass-loss episodes, calculated stellar properties mainly using a previously published temperature calibration, and investigated the nature of LTVs and their influence on quasi-periods and stellar properties. Based on driven one-zone stellar oscillation models, the pulsations can be characterised as 'weakly chaotic'. The BV photometry revealed a high-opacity layer in the atmospheres. When the temperature rises the mass loss increases as well, consequently, as the density of the high-opacity layer. As a result, the absorption in B and V grow. The absorption in B, presumably of the order of one to a few 0.1mag, is always higher than in V. This difference renders redder and variable (B-V) colour indexes, but the absorption law is unknown. This property of YHGs is unpredictable and explains why spectroscopic temperatures (reddening independent) are always higher than photometric ones, but the difference decreases with the temperature. A new (weak) eruption of rho Cas has been identified. We propose shorter distances for rho Cas and HR 5171A than the accepted ones. Therefore, a correction to decrease the blue luminescence of HR 5171A by polycyclic aromatic hydrocarbon (PAH) molecules is necessary, and HR 5171A would no longer be a member of the cluster Gum48d. HR 5171A is only subject to one source of light variation, not by two as the literature suggests. Eruptive episodes (lasting one to two years), of YHGs prefer relatively cool circumstances when a red evolutionary loop (RL) has shifted the star to the red on the HR diagram. After the eruption, a blue loop evolution (BL) is triggered lasting one to a few decades. We claim that in addition to HR 8752, also the other three YHGs have shown similar cycles over the last 70 years. This supports the suspicion that HD 179821 might be a YHG (with a possible eruptive episode between 1925 and 1960). The range in temperature of these cyclic Teff variations is 3000K-4000K. LTVs mainly consist of such BL and RL evolutions, which are responsible for a decrease and increase, respectively, of the quasi-periods. The reddening episode of HR 5171A between 1960 and 1974 was most likely due to a red loop evolution, and the reddening after the 1975 eruption was likely due to a shell ejection, taking place simultaneously with a blue loop evolution.
- ID:
- ivo://CDS.VizieR/J/AJ/160/148
- Title:
- RI-band LC of microlensing event OGLE-2018-BLG-1269Lb
- Short Name:
- J/AJ/160/148
- Date:
- 08 Dec 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a planet in the microlensing event OGLE-2018-BLG-1269 with a planet-host mass ratio q~6x10^-4^, i.e., 0.6 times smaller than the Jupiter/Sun mass ratio. Combined with the Gaia parallax and proper motion, a strong one-dimensional constraint on the microlens parallax vector allows us to significantly reduce the uncertainties of lens physical parameters. A Bayesian analysis that ignores any information about light from the host yields that the planet is a cold giant (M_2_=0.69_-0.22_^+0.44^M_J_) orbiting a Sun-like star (M_1_=1.13_-0.35_^+0.72^M_{sun}_) at a distance of D_L_=2.56_-0.62_^+0.92^kpc. The projected planet-host separation is a_{perp}_=4.61_-1.17_^+1.70^au. Using Gaia astrometry, we show that the blended light lies <~12mas from the host and therefore must be either the host star or a stellar companion to the host. An isochrone analysis favors the former possibility at >99.6%. The host is therefore a subgiant. For host metallicities in the range of 0.0<=[Fe/H]<=+0.3, the host and planet masses are then in the range of 1.16<=M_1_/M_{sun}_<=1.38 and 0.74<=M_2_/M_J_<=0.89, respectively. Low host metallicities are excluded. The brightness and proximity of the lens make the event a strong candidate for spectroscopic follow-up both to test the microlensing solution and to further characterize the system.
- ID:
- ivo://CDS.VizieR/J/A+A/402/113
- Title:
- (RI)c photometry of variables in M31
- Short Name:
- J/A+A/402/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Cousins R and I band photometry of variable stars in a ~13'x13' region in the disk of M31 galaxy, obtained during 141 nights. Of the 26 Cepheid variables present in the region, two are newly discovered, 11 are classified as Cepheids for the first time and 13 are confirmed as Cepheids. The extensive photometry of these Cepheids enabled us to determine precise phase and amplitude of pulsation which ranges from 0.11 to 0.48mag in R band. The period of variability ranges from ~7.5 to 56 days. The period-luminosity diagram is used to derive a distance modulus of 24.49+/-0.11mag for M31 galaxy. We also report variability in 333 other stars, of them, 115 stars appear to be long period variables, 2 suspected eclipsing binaries and remaining 216 are irregular variables.
- ID:
- ivo://CDS.VizieR/J/A+A/398/239
- Title:
- RI differential photometry of CU Cnc
- Short Name:
- J/A+A/398/239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric observations in the R and I bands of the detached M-type double-lined eclipsing binary CU Cnc have been acquired and analysed. The photometric elements obtained from the analysis of the light curves have been combined with an existing spectroscopic solution to yield high-precision (errors<2%) absolute dimensions: M_A_=0.4333+/-0.0017M_{sun}_, M_B_=0.3980+/-0.0014M_{sun}_, R_A_=0.4317+/-0.0052R_{sun}_, and R_B_=0.3908+/-0.0094R_{sun}_. The mean effective temperature of the system has been estimated to be Teff=3140+/-150K by comparing multi-band photometry with synthetic colors computed from model atmospheres. Additionally, we have been able to obtain an estimate for the age (~320Myr) and chemical composition ([Fe/H]~0.0) of the binary system through its membership of the Castor moving group.
- ID:
- ivo://CDS.VizieR/J/A+A/429/1007
- Title:
- RIJHK photometry of VLM objects near eps Ori
- Short Name:
- J/A+A/429/1007
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Coordinates and photometry of very low mass objects near epsilon Ori are presented. The RIJHK photometry of these objects is consistent with membership of the young Ori OB Ib association. Time series observations of this region were carried out using the ESO/MPG WFI at the 2.2-m telescope on La Silla, from 18 to 22 December 2001. In the framework of this monitoring campaign, we obtained deep Cousins R- and I-band images, from which we derived coordinates (columns 2 and 3) as well as photometry in the R- and I-band (columns 4 and 5). Additional near-infrared photometry in J, H, K comes from the 2MASS database (columns 6--8). The cluster member selection is based on a (I,R-I) colour magnitude diagram. The (J-H) colours were used to reject contaminating field stars. The masses given in column 9 were estimated by comparing the near-infrared photometry with the evolutionary tracks of Baraffe et al. (1998A&A...337..403B), assuming an age of 5Myr.
- ID:
- ivo://CDS.VizieR/J/AN/325/705
- Title:
- RIJHKs of low-mass stars in sigma Ori
- Short Name:
- J/AN/325/705
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an RI photometric survey covering an area of 430 arcmin^2^ around the multiple star sigma Orionis. The observations were conducted with the 0.8m IAC-80 Telescope at the Teide Observatory. The survey limiting R and I magnitudes are 22.5 and 21, and completeness magnitudes 21 and 20, respectively. We have selected 53 candidates from the I vs. R-I colour-magnitude diagram (I=14-20) that follow the previously known photometric sequence of the cluster. Adopting an age of 2-4 Myr for the cluster, we find that these objects span a mass range from 0.35M_{sun}_ to 0.015M_{sun}_. We have performed J-band photometry of 52 candidates and K_s photometry for 12 of them, with the result that 50 follow the expected infrared sequence for the cluster, thus confirming with great confidence that the majority of the candidates are bona fide members. JHK_s photometry from the Two Micron All Sky Survey (2MASS, Cat. <II/246>) is available for 50 of the candidates and are in good agreement with our data. Out of 48 candidates, which have photometric accuracies better than 0.1mag in all bands, only three appear to show near-infrared excesses.
- ID:
- ivo://CDS.VizieR/J/MNRAS/401/1587
- Title:
- RIK photometry of far-IR sources in NGP
- Short Name:
- J/MNRAS/401/1587
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present follow-up observations of the far-infrared (FIR) sources at 90, 150 and 180um detected as part of the ISOPHOT EBL project, which has recently measured the absolute surface brightness of the cosmic infrared background (CIRB) radiation for the first time independently from COBE data. We have observed the fields at the North Galactic Pole region in the optical and near-IR, and complement these data with Sloan Digital Sky Survey photometry, and spectroscopy where available, and present identifications of the 25 FIR sources which reach down to ~150mJy in all three ISOPHOT bands. Identifications are done by means of full spectral energy density fitting to all sources in the FIR error circle areas.
