- ID:
- ivo://CDS.VizieR/J/other/Ap/44.335
- Title:
- M stars in Cepheus region
- Short Name:
- J/other/Ap/44.33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a spectral classification of 257 M stars observed in the Cepheus region are given. Their equatorial coordinates, photographic stellar magnitudes, and spectral subtypes were determined. These stars are giants and supergiants, in all probability. None of them appear in a catalog of variable stars. It is assumed that variability might be detected in many of them upon further study. Fifty-two of the stars have been identified with infrared sources. In addition to the originally published data, magnitudes, positions, cross-identifications and notes have been added in May 2002. (see the "History" section below)
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- ID:
- ivo://CDS.VizieR/J/ApJS/240/31
- Title:
- M-subdwarf research. I. LAMOST DR4 spectra obs.
- Short Name:
- J/ApJS/240/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We propose a revision of the system developed by Lepine+ (2007ApJ...669.1235L) for spectroscopic M-subdwarf classification. Based on an analysis of subdwarf spectra and templates from Savcheva+ (2014ApJ...794..145S), we show that the CaH1 feature originally proposed by Gizis (1997, J/AJ/113/806) is important in selecting reliable cool subdwarf spectra. This index should be used in combination with the [TiO5, CaH2+CaH3] relation provided by Lepine+ to avoid misclassification results. In the new system, the dwarf-subdwarf separators are first derived from a sample of more than 80000 M dwarfs and a "labeled" subdwarf subsample, and these objects are all visually identified from their optical spectra. Based on these two samples, we refit the initial [TiO5, CaH1] relation and propose a new [CaOH, CaH1] relation supplementing the [TiO5, CaH1] relation to reduce the impact of uncertainty in flux calibration on classification accuracy. In addition, we recalibrate the {zeta}TiO/CaH parameter defined in Lepine+ to enable its successful application to Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectra. Using this new system, we select candidates from LAMOST Data Release 4 and finally identify a set of 2791 new M-subdwarf stars, covering the spectral sequence from type M0 to M7. This sample contains a large number of objects located at low Galactic latitudes, especially in the Galactic anti-center direction, expanding beyond previously published halo- and thick disk-dominated samples. Besides, we detect magnetic activity in 141 objects. We present a catalog for this M-subdwarf sample, including radial velocities, spectral indices and errors, and activity flags, with a compilation of external data (photometric and Gaia Data Release 2 astrometric parameters).
- ID:
- ivo://CDS.VizieR/J/ApJS/243/28
- Title:
- M-type star magnetic activities from LAMOST & Kepler
- Short Name:
- J/ApJS/243/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a statistical study of magnetic activities of M-type stars by combining the spectra of LAMOST DR5 with light curves from the Kepler and K2 missions. We mainly want to study the relationship between chromospheric activity and flares, and their relations of magnetic activity and rotation period. We have obtained the maximum catalog of 516688 M-type stellar spectra of 480912 M stars from LAMOST-DR5 and calculated their equivalent widths of chromospheric activity indicators (H{alpha}, H{beta}, H{gamma}, H{delta}, CaII H&K, and HeI D3). Using the H{alpha} indicator, 40464 spectra of 38417 M stars show chromospheric activity, and 1791 of these 5499 M-type stars with repeated observations have H{alpha} variability. We used an automatic detection plus visual inspection method to detect 17432 flares on 8964 M-type stars from the catalog by cross-matching LAMOST DR5 and the Kepler and K2 databases. We used the Lomb-Scargle method to calculate their rotation periods. We find that the flare frequency is consistent with the ratio of activities of these chromospheric activity indicators as a function of spectral type in M0-M3. We find the equivalent widths of H{alpha} and CaII H have a significant statistical correlation with the flare amplitude in M-type stars. We confirm that the stellar flare is affected by both the stellar magnetic activity and the rotation period. Finally, using the H{alpha} equivalent width equal to 0.75{AA} and using the rotation period equal to 10 days as the threshold for the M-type stellar flare time frequency are almost equivalent.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/8
- Title:
- M-type stars in LAMOST DR5
- Short Name:
- J/ApJS/244/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new catalogs of M giant and M dwarf stars from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) data release 5 (DR5). In total, 39796 M giants and 501152 M dwarfs are identified from the classification pipeline. The template-fitting results contain M giants with 7 temperature subtypes from M0 to M6, M dwarfs with 18 temperature subtypes from K7.0 to M8.5, and 12 metallicity subclasses from dMr to usdMp. We cross-matched our M-type catalog with the Two Micron All-Sky Survey (2MASS) and Wide-field Infrared Survey Explorer (WISE) catalog to obtain infrared magnitude and colors. Adopting the distances derived from the parallaxes in Gaia DR2, the M_G_ versus (G_bp_-G_rp_)_0_ diagram shows that there are also early-type stars and white dwarf-M dwarf binaries included in our M-type stars sample, with a contamination rate of about 4.6% for M giants and 0.48% for M dwarfs. We found that CaH spectral indices are an efficient selection criteria for carbon stars. A total of 289 carbon stars were identified from the M giants sample, and further confirmed by LAMOST spectra.
- ID:
- ivo://CDS.VizieR/J/ApJ/728/48
- Title:
- Multicolor eclipse data for 6 new binaries
- Short Name:
- J/ApJ/728/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery and characterization of six new M dwarf eclipsing binary systems. The 12 stars in these eclipsing systems have masses spanning 0.38-0.59M_{sun}_ and orbital periods of 0.6-1.7 days, with typical uncertainties of ~0.3% in mass and ~0.5%-2.0% in radius. Combined with six known systems with high-precision measurements, our results reveal an intriguing trend in the low-mass regime. For stars with M=0.35-0.80M_{sun}_, components in short-period binary systems (P<~1 day; 12 stars) have radii which are inflated by up to 10% ({mu}=4.8+/-1.0%) with respect to evolutionary models for low-mass main-sequence stars, whereas components in longer-period systems (>1.5 days; 12 stars) tend to have smaller radii ({mu}=1.7+/-0.7%).
- ID:
- ivo://CDS.VizieR/J/AJ/159/139
- Title:
- Multiple M dwarf stars with Robo-AO and Gaia DR2
- Short Name:
- J/AJ/159/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze observations from Autonomous laser-adaptive-optics for few-meter-class telescopes (Robo-AO)'s field M dwarf survey taken on the 2.1m Kitt Peak telescope and perform a multiplicity comparison with Gaia DR2. Through its laser-guided, automated system, the Robo-AO instrument has yielded the largest adaptive optics M dwarf multiplicity survey to date. After developing an interface to visually identify and locate stellar companions, we selected 11 low-significance Robo-AO detections for follow-up on the Keck II telescope using NIRC2. In the Robo-AO survey we find 553 candidate companions within 4" around 534 stars out of 5566 unique targets, most of which are new discoveries. Using a position cross-match with DR2 on all targets, we assess the binary recoverability of Gaia DR2 and compare the properties of multiples resolved by both Robo-AO and Gaia. The catalog of nearby M dwarf systems and their basic properties presented here can assist other surveys which observe these stars, such as the NASA Transiting Exoplanet Survey Satellite (TESS) mission.
- ID:
- ivo://CDS.VizieR/J/ApJ/843/31
- Title:
- MUSCLES Treasury Survey. IV. M dwarf UV fluxes
- Short Name:
- J/ApJ/843/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Characterizing the UV spectral energy distribution (SED) of an exoplanet host star is critically important for assessing its planet's potential habitability, particularly for M dwarfs, as they are prime targets for current and near-term exoplanet characterization efforts and atmospheric models predict that their UV radiation can produce photochemistry on habitable zone planets different from that on Earth. To derive ground-based proxies for UV emission for use when Hubble Space Telescope (HST) observations are unavailable, we have assembled a sample of 15 early to mid-M dwarfs observed by HST and compared their nonsimultaneous UV and optical spectra. We find that the equivalent width of the chromospheric Ca II K line at 3933{AA}, when corrected for spectral type, can be used to estimate the stellar surface flux in ultraviolet emission lines, including HI Ly{alpha}. In addition, we address another potential driver of habitability: energetic particle fluxes associated with flares. We present a new technique for estimating soft X-ray and >10MeV proton flux during far-UV emission line flares (Si IV and He II) by assuming solar-like energy partitions. We analyze several flares from the M4 dwarf GJ 876 observed with HST and Chandra as part of the MUSCLES Treasury Survey and find that habitable zone planets orbiting GJ 876 are impacted by large Carrington-like flares with peak soft X-ray fluxes >=10^-3^W/m^2^ and possible proton fluxes ~10^2^-10^3^pfu, approximately four orders of magnitude more frequently than modern-day Earth.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/2192
- Title:
- NCJM catalog of M dwarfs
- Short Name:
- J/MNRAS/457/2192
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop a method to identify the spectroscopic signature of unresolved L-dwarf ultracool companions, which compares the spectra of candidates and their associated control stars using spectral ratio differences and residual spectra. We present SpeX prism-mode spectra (0.7-2.5 micron) for a pilot sample of one hundred and eleven mid M dwarfs, including twenty-eight which were previously identified as candidates for unresolved ultracool companionship (a sub-sample from Cook et al. 2016; paper 1) and eighty-three single M dwarfs which were optically colour-similar to these candidates (which we use as `control stars'). We identify four candidates with evidence for near-infrared excess. One of these (WISE J100202.50+074136.3) shows strong evidence for an unresolved L dwarf companion in both its spectral ratio difference and its residual spectra, two most likely have a different source for the near-infrared excess, and the other may be due to spectral noise. We also establish expectations for a null result (i.e. by searching for companionship signatures around the M dwarf control stars), as well as determining the expected outcome for ubiquitous companionship (as a means of comparison with our actual results), using artificially generated unresolved M+L dwarf spectra. The results of these analyses are compared to those for the candidate sample, and reasonable consistency is found. With a full follow-up program of our candidates sample from paper 1, we might expect to confirm up to 40 such companions in the future, adding extensively to the known desert population of M3-M5 dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/791/54
- Title:
- Nearby M Dwarfs parameters
- Short Name:
- J/ApJ/791/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Comparisons between the planet populations around solar-type stars and those orbiting M dwarfs shed light on the possible dependence of planet formation and evolution on stellar mass. However, such analyses must control for other factors, i.e., metallicity, a stellar parameter that strongly influences the occurrence of gas giant planets. We obtained infrared spectra of 121 M dwarfs stars monitored by the California Planet Search and determined metallicities with an accuracy of 0.08 dex. The mean and standard deviation of the sample are -0.05 and 0.20 dex, respectively. We parameterized the metallicity dependence of the occurrence of giant planets on orbits with a period less than two years around solar-type stars and applied this to our M dwarf sample to estimate the expected number of giant planets. The number of detected planets (3) is lower than the predicted number (6.4), but the difference is not very significant (12% probability of finding as many or fewer planets). The three M dwarf planet hosts are not especially metal rich and the most likely value of the power-law index relating planet occurrence to metallicity is 1.06 dex per dex for M dwarfs compared to 1.80 for solar-type stars; this difference, however, is comparable to uncertainties. Giant planet occurrence around both types of stars allows, but does not necessarily require, a mass dependence of ~1 dex per dex. The actual planet-mass-metallicity relation may be complex, and elucidating it will require larger surveys like those to be conducted by ground-based infrared spectrographs and the Gaia space astrometry mission.
- ID:
- ivo://CDS.VizieR/J/AJ/144/99
- Title:
- Near-IR spectroscopy of 36 late M dwarfs
- Short Name:
- J/AJ/144/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of 36 late M dwarfs obtained with the KeckII/NIRSPEC in the J band at a resolution of ~20000. We have measured projected rotational velocities, absolute radial velocities, and pseudo-equivalent widths of atomic lines. Twelve of our targets did not have previous measurements in the literature. For the other 24 targets, we confirm previously reported measurements. We find that 13 stars from our sample have vsini below our measurement threshold (12km/s) whereas four of our targets are fast rotators (vsini>30km/s). As fast rotation causes spectral features to be washed out, stars with low projected rotational velocities are sought for radial velocity surveys. At our intermediate spectral resolution, we have confirmed the identification of neutral atomic lines reported in McLean et al. We also calculated pseudo-equivalent widths of 12 atomic lines. Our results confirm that the pseudo-equivalent width of KI lines is strongly dependent on spectral types. We observe that the pseudo-equivalent width of FeI and MnI lines remains fairly constant with later spectral type. We suggest that these lines are particularly suitable for deriving metallicities for late M dwarfs.
