- ID:
- ivo://CDS.VizieR/J/AJ/154/124
- Title:
- M dwarfs-long-term photometric variability
- Short Name:
- J/AJ/154/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report findings from a long-term photometric variability study of M dwarfs carried out at the SMARTS 0.9 m telescope at the Cerro Tololo Inter-American Observatory. As part of a multi-faceted effort to investigate the range of luminosities of M dwarfs of a given color on the Hertzsprung-Russell Diagram, 76 M dwarfs have been observed for 3-17 years in the Johnson-Kron-Cousins V band. We find that stars elevated above the center of the main sequence distribution tend to have higher levels of variability, likely caused by magnetic activity, than their fainter counterparts below the center. This study provides insight into how the long-term magnetic activity of these stars may be affecting their sizes, luminosities, and thus positions on the H-R Diagram.
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1732. M dwarfs with IR excess
- ID:
- ivo://CDS.VizieR/J/ApJ/794/146
- Title:
- M dwarfs with IR excess
- Short Name:
- J/ApJ/794/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) spectroscopic catalog, we searched the WISE AllWISE catalog to investigate the occurrence of warm dust, as inferred from IR excesses, around field M dwarfs (dMs). We developed SDSS/WISE color selection criteria to identify 175 dMs (from 70841) that show IR flux greater than the typical dM photosphere levels at 12 and/or 22{mu}m, including seven new stars within the Orion OB1 footprint. We characterize the dust populations inferred from each IR excess and investigate the possibility that these excesses could arise from ultracool binary companions by modeling combined spectral energy distributions. Our observed IR fluxes are greater than levels expected from ultracool companions (>3{sigma}). We also estimate that the probability the observed IR excesses are due to chance alignments with extragalactic sources is <0.1%. Using SDSS spectra we measure surface gravity-dependent features (K, Na, and CaH 3) and find <15% of our sample indicates low surface gravities. Examining tracers of youth (H{alpha}, UV fluxes, and Li absorption), we find <3% of our sample appear young, indicating we are observing a population of field stars >~1Gyr, likely harboring circumstellar material. We investigate age-dependent properties probed by this sample, studying the disk fraction as a function of Galactic height. The fraction remains small and constant to |Z|~700pc and then drops, indicating little to no trend with age. Possible explanations for disks around field dMs include (1) collisions of planetary bodies, (2) tidal disruption of planetary bodies, or (3) failed planet formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/L21
- Title:
- Measured photometry of SN 2014J from HST
- Short Name:
- J/ApJ/788/L21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The wavelength dependence of the extinction of Type Ia SN 2014J in the nearby galaxy M82 has been measured using UV to near-IR photometry obtained with the Hubble Space Telescope, the Nordic Optical Telescope, and the Mount Abu Infrared Telescope. This is the first time that the reddening of an SN Ia is characterized over the full wavelength range of 0.2-2 {mu}m. A total-to-selective extinction, R_V_>= 3.1, is ruled out with high significance. The best fit at maximum using a Galactic type extinction law yields R_V_=1.4+/-0.1. The observed reddening of SN 2014J is also compatible with a power-law extinction, A_{lambda}_/A_V_=({lambda}/{lambda}_V_)^p^ as expected from multiple scattering of light, with p=-2.1+/-0.1. After correcting for differences in reddening, SN 2014J appears to be very similar to SN 2011fe over the 14 broadband filter light curves used in our study.
- ID:
- ivo://CDS.VizieR/J/other/RAA/18.126
- Title:
- Membership catalog for M12 (NGC6218) stars
- Short Name:
- J/other/RAA/18.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using astrometric techniques developed by Anderson et al., we determine proper motions (PMs) in the ~14.60x16.53arcmin^2^ area of the kinematically "thick-disk" globular cluster M12. The cluster's proximity and sparse nature makes it a suitable target for ground-based telescopes. Archive images with time gap of ~11.1-years were observed with the wide-field imager (WFI) mosaic camera mounted on the ESO 2.2m telescope. The median value of PM error in both components is ~0.7mas/yr for the stars having V<=20mag. PMs are used to determine membership probabilities and to separate field stars from the cluster sample. In electronic form, a membership catalog of 3725 stars with precise coordinates, PMs and BV RI photometry is being provided. One of the possible applications of the catalog is demonstrated by gathering the membership information of the variable stars, blue stragglers and X-ray sources reported earlier in the cluster's region.
1735. Members of IC 2391
- ID:
- ivo://CDS.VizieR/J/A+AS/126/357
- Title:
- Members of IC 2391
- Short Name:
- J/A+AS/126/357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New 4-colour BV(RI)_KC_ CCD photometry to a limiting magnitude of V=~19 is presented for 1428 objects observed towards the direction of the young, open cluster IC 2391. We observed 36 (2'x3') fields within 17arcmin of the nominal cluster core. By fitting the theoretical isochrones of D'Antona & Mazzitelli (1994ApJS...90..467D) to a combination of colour-magnitude and colour-colour diagrams, we have identified 17 stars as probable cluster members with a further 85 stars as possible members. The brightness distribution of low-mass members is compared with the luminosity function observed for the Pleiades and we estimate that the contamination due to background giants should be small.
- ID:
- ivo://CDS.VizieR/J/AJ/130/1065
- Title:
- Members of the Sculptor dwarf spheroidal galaxy
- Short Name:
- J/AJ/130/1065
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a wide-field survey of the Sculptor dwarf spheroidal galaxy are presented. Our aims were to obtain an accurate map of the outer structure of Sculptor and to determine the level of interaction between this system and the Galaxy. Photometry was obtained in two colors down to the magnitude limits of V=20 and I=19, covering a 3.1{deg}x3.1{deg} area centered on Sculptor.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/87
- Title:
- Members of the young open cluster IC 2395
- Short Name:
- J/ApJ/832/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new deep UBVRI images and high-resolution multi-object optical spectroscopy of the young (~6-10Myr old), relatively nearby (800pc) open cluster IC 2395. We identify nearly 300 cluster members and use the photometry to estimate their spectral types, which extend from early B to middle M. We also present an infrared imaging survey of the central region using the IRAC and MIPS instruments on board the Spitzer Space Telescope, covering the wavelength range from 3.6 to 24{mu}m. Our infrared observations allow us to detect dust in circumstellar disks originating over a typical range of radii from ~0.1 to ~10 au from the central star. We identify 18 Class II, 8 transitional disk, and 23 debris disk candidates, respectively, 6.5%, 2.9%, and 8.3% of the cluster members with appropriate data. We apply the same criteria for transitional disk identification to 19 other stellar clusters and associations spanning ages from ~1 to ~18Myr. We find that the number of disks in the transitional phase as a fraction of the total with strong 24{mu}m excesses ([8]-[24]>=1.5) increases from (8.4+/-1.3)% at ~3Myr to (46+/-5)% at ~10Myr. Alternative definitions of transitional disks will yield different percentages but should show the same trend.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/11
- Title:
- Member stars in the MW satellite Tucana III
- Short Name:
- J/ApJ/838/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Magellan/IMACS spectroscopy of the recently discovered Milky Way satellite Tucana III (Tuc III). We identify 26 member stars in Tuc III from which we measure a mean radial velocity of v_hel_=-102.3+/-0.4(stat.)+/-2.0(sys.)km/s, a velocity dispersion of 0.1_-0.1_^+0.7^km/s, and a mean metallicity of [Fe/H]=-2.42_-0.08_^+0.07^. The upper limit on the velocity dispersion is {sigma}<1.5km/s at 95.5% confidence, and the corresponding upper limit on the mass within the half-light radius of Tuc III is 9.0x10^4^M_{sun}_. We cannot rule out mass-to-light ratios as large as 240M_{sun}_/L_{sun}_ for Tuc III, but much lower mass-to-light ratios that would leave the system baryon-dominated are also allowed. We measure an upper limit on the metallicity spread of the stars in Tuc III of 0.19dex at 95.5% confidence. Tuc III has a smaller metallicity dispersion and likely a smaller velocity dispersion than any known dwarf galaxy, but a larger size and lower surface brightness than any known globular cluster. Its metallicity is also much lower than those of the clusters with similar luminosity. We therefore tentatively suggest that Tuc III is the tidally stripped remnant of a dark matter-dominated dwarf galaxy, but additional precise velocity and metallicity measurements will be necessary for a definitive classification. If Tuc III is indeed a dwarf galaxy, it is one of the closest external galaxies to the Sun. Because of its proximity, the most luminous stars in Tuc III are quite bright, including one star at V=15.7 that is the brightest known member star of an ultra-faint satellite.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/90
- Title:
- Merging galaxies with tidal tails in COSMOS to z=1
- Short Name:
- J/ApJ/832/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tidal tails are created in major mergers involving disk galaxies. It remains to be explored how the tidal tails trace the assembly history of massive galaxies. We identify a sample of 461 merging galaxies with long tidal tails, from 35076 galaxies mass-complete at M*>=10^9.5^M_{sun}_ and 0.2<=z<=1, based on Hubble Space Telescope/ACS F814W imaging data and public catalogs of the COSMOS field. The long tails refer to those with length equal to or greater than the diameter of their host galaxies. The mergers with tidal tails are selected using our novel A_O_-D_O_ technique for strong asymmetric features, along with visual examination. Our results show that the fraction of tidal-tailed mergers evolves mildly with redshift, as ~(1+z)^2.0+/-0.4^, and becomes relatively higher in less-massive galaxies, out to z=1. With a timescale of 0.5Gyr for the tidal-tailed mergers, we obtain that the occurrence rate of such mergers follows 0.01+/-0.007(1+z)^2.3+/-1.4^Gyr^-1^, and corresponds to ~0.3 events since z=1, as well as roughly one-third of the total budget of major mergers from the literature. For disk-involved major mergers, nearly half of them have undergone a phase with long tidal tails.
- ID:
- ivo://CDS.VizieR/J/ApJ/727/14
- Title:
- Merging galaxy cluster A2255 in mid-IR
- Short Name:
- J/ApJ/727/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the mid-infrared (MIR) observation of a nearby galaxy cluster, A2255, by the AKARI space telescope. Using AKARI's continuous wavelength coverage between 3 and 24um and the wide field of view, we investigate the properties of cluster member galaxies to see how the infall of the galaxies, the cluster substructures, and the cluster-cluster merger influence their evolution. We show that the excess of MIR (~11um) flux is a good indicator for discriminating galaxies at different evolutionary stages and for dividing galaxies into three classes accordingly: strong MIR-excess (N3-S11>0.2) galaxies that include both unobscured and obscured star-forming galaxies; weak MIR-excess (-2.0<N3-S11<-1.2) galaxies that are quiescent, old (>5Gyr) galaxies where the MIR emission arises mainly from the circumstellar dust around AGB stars; and intermediate MIR-excess (-1.2<N3-S11<0.2) galaxies in between the two classes that are less than a few Gyr old past the prime star formation activity. With the MIR-excess diagnostics, we investigate how local and cluster-scale environments affect the individual galaxies. We derive the total star formation rate (SFR) and the specific SFR of A2255 using the strong MIR-excess galaxies.
