scholarly journals Characterization of M dwarfs using optical mid-resolution spectra for exploration of small exoplanets

2020 ◽  
Author(s):  
Yohei Koizumi ◽  
Masayuki Kuzuhara ◽  
Masashi Omiya ◽  
Teruyuki Hirano ◽  
John Wisniewski ◽  
...  
Keyword(s):  
Sample Selection ◽  
Optical Spectra ◽  
Average Error ◽  
Spectral Energy ◽  
M Dwarfs ◽  
Energy Distributions ◽  
Fitting Procedures ◽  
Optical Region ◽  
Selection For

Abstract We present the optical spectra of 338 nearby M dwarfs, and compute their spectral types, effective temperatures (Teff), and radii. Our spectra were obtained using several optical spectrometers with spectral resolutions that range from 1200 to 10000. As many as 97% of the observed M-type dwarfs have a spectral type of M3–M6, with a typical error of 0.4 subtype, among which the spectral types M4–M5 are the most common. We infer the Teff of our sample by fitting our spectra with theoretical spectra from the PHOENIX model. Our inferred Teff is calibrated with the optical spectra of M dwarfs whose Teff have been well determined with the calibrations that are supported by previous interferometric observations. Our fitting procedures utilize the VO absorption band (7320–7570 Å) and the optical region (5000–8000 Å), yielding typical errors of 128 K (VO band) and 85 K (optical region). We also determine the radii of our sample from their spectral energy distributions. We find most of our sample stars have radii of <0.6 R⊙, with the average error being 3%. Our catalog enables efficient sample selection for exoplanet surveys around nearby M-type dwarfs.

Tìm kiếm đĩa tàn dư xung quanh các sao lùn kiểu phổ M-trễ nằm trong vùng lân cận Mặt Trời

2019 ◽  
Vol 15 (9) ◽  
pp. 43
Author(s):  
Nguyễn Thành Đạt ◽  
Phan Bảo Ngọc
Keyword(s):  
Spectral Energy ◽  
Archival Data ◽  
Debris Disks ◽  
M Dwarfs ◽  
Energy Distributions ◽  
Infrared Excess ◽  
Low Mass ◽  
M Dwarf ◽  
Infrared Survey ◽  
Infrared Data

In this paper, we present our search for debris disks in a sample of nearby late-M dwarfs based on infrared data of the Wide Infrared Survey Explorer. Using archival data, we constructed spectral energy distributions of these targets to detect their infrared excess. We detected infrared excess only in one target. This late-M dwarf is an excellent benchmark for further study of disks around very low-mass objects.

scholarly journals Photometric characterization of multiple populations in star clusters: the impact of the first dredge-up

2020 ◽  
Vol 492 (3) ◽  
pp. 3459-3464 ◽  
Author(s):  
Maurizio Salaris ◽  
Chris Usher ◽  
Silvia Martocchia ◽  
Emanuele Dalessandro ◽  
Nate Bastian ◽  
...  
Keyword(s):  
Star Clusters ◽  
Light Element ◽  
Element Abundance ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Multiple Populations ◽  
Red Giant ◽  
The Impact

ABSTRACT The existence of star-to-star light-element abundance variations (multiple populations, MPs) in massive Galactic and extragalactic star clusters older than about 2 Gyr is by now well established. Photometry of red giant branch (RGB) stars has been and still is instrumental in enabling the detection and characterization of cluster MPs, through the appropriate choices of filters, colours, and colour combinations that are mainly sensitive to N and – to a lesser degree – C stellar surface abundances. An important issue not yet properly addressed is that the translation of the observed widths of the cluster RGBs to abundance spreads must account for the effect of the first dredge-up on the surface chemical patterns, hence on the spectral energy distributions of stars belonging to the various MPs. We have filled this gap by studying theoretically the impact of the dredge-up on the predicted widths of RGBs in clusters hosting MPs. We find that for a given initial range of N abundances, the first dredge-up reduces the predicted RGB widths in N-sensitive filters compared to the case when its effect on the stellar spectral energy distributions is not accounted for. This reduction is a strong function of age and has also a dependence on metallicity. The net effect is an underestimate of the initial N-abundance ranges from RGB photometry if the first dredge-up is not accounted for in the modelling, and also the potential determination of spurious trends of N-abundance spreads with age.

scholarly journals CARMENES input catalogue of M dwarfs

2020 ◽  
Vol 642 ◽  
pp. A115 ◽  
Author(s):  
C. Cifuentes ◽  
J. A. Caballero ◽  
M. Cortés-Contreras ◽  
D. Montes ◽  
F. J. Abellán ◽  
...  
Keyword(s):  
Parameter Determination ◽  
Spectral Energy ◽  
M Dwarfs ◽  
Energy Distributions ◽  
Multiple Systems ◽  
New Era ◽  
Virtual Observatory Tools ◽  
Absolute Magnitudes ◽  
The Impact ◽  
Input Catalogue

Context. The relevance of M dwarfs in the search for potentially habitable Earth-sized planets has grown significantly in the last years. Aims. In our on-going effort to comprehensively and accurately characterise confirmed and potential planet-hosting M dwarfs, in particular for the CARMENES survey, we have carried out a comprehensive multi-band photometric analysis involving spectral energy distributions, luminosities, absolute magnitudes, colours, and spectral types, from which we have derived basic astrophysical parameters. Methods. We have carefully compiled photometry in 20 passbands from the ultraviolet to the mid-infrared, and combined it with the latest parallactic distances and close-multiplicity information, mostly from Gaia DR2, of a sample of 2479 K5 V to L8 stars and ultracool dwarfs, including 2210 nearby, bright M dwarfs. For this, we made extensive use of Virtual Observatory tools. Results. We have homogeneously computed accurate bolometric luminosities and effective temperatures of 1843 single stars, derived their radii and masses, studied the impact of metallicity, and compared our results with the literature. The over 40 000 individually inspected magnitudes, together with the basic data and derived parameters of the stars, individual and averaged by spectral type, have been made public to the astronomical community. In addition, we have reported 40 new close multiple systems and candidates (ρ <  3.3 arcsec) and 36 overluminous stars that are assigned to young Galactic populations. Conclusions. In the new era of exoplanet searches around M dwarfs via transit (e.g. TESS, PLATO) and radial velocity (e.g. CARMENES, NIRPS+HARPS), this work is of fundamental importance for stellar and therefore planetary parameter determination.

scholarly journals Spectral Energy Distributions for Disk and Halo M Dwarfs

2000 ◽  
Vol 535 (2) ◽  
pp. 965-974 ◽  
Author(s):  
S. K. Leggett ◽  
F. Allard ◽  
Conard Dahn ◽  
P. H. Hauschildt ◽  
T. H. Kerr ◽  
...  
Keyword(s):  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
M Dwarfs ◽  
Energy Distributions

scholarly journals AVOCADO: A Virtual Observatory Census to Address Dwarfs Origins

2010 ◽  
Vol 6 (S277) ◽  
pp. 230-233
Author(s):  
Rubén Sánchez-Janssen ◽  
Keyword(s):  
Structural Parameters ◽  
Spectral Energy ◽  
Virtual Observatory ◽  
Energy Distributions ◽  
Public Data ◽  
Virtual Observatory Tools ◽  
Formation And Evolution ◽  
Stellar Masses ◽  
Evolutionary Paths

AbstractDwarf galaxies are by far the most abundant of all galaxy types, yet their properties are still poorly understood–especially due to the observational challenge that their intrinsic faintness represents. AVOCADO aims at establishing firm conclusions on their formation and evolution by constructing a homogeneous, multiwavelength dataset for a statistically significant sample of several thousand nearby dwarfs (−18 < Mi < −14). Using public data and Virtual Observatory tools, we have built GALEX+SDSS+2MASS spectral energy distributions that are fitted by a library of single stellar population models. Star formation rates, stellar masses, ages and metallicities are further complemented with structural parameters that can be used to classify them morphologically. This unique dataset, coupled with a detailed characterization of each dwarf's environment, allows for a fully comprehensive investigation of their origins and to track the (potential) evolutionary paths between the different dwarf types.

scholarly journals Liquid-Mirror Telescope Surveys

1998 ◽  
Vol 11 (1) ◽  
pp. 464-467
Author(s):  
P. Hickson
Keyword(s):  
Integration Time ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Ccd Cameras ◽  
Photometric Redshifts ◽  
Rotating Liquid ◽  
Liquid Mirrors ◽  
Under Construction ◽  
Optical Telescopes ◽  
Mirror Telescope

Abstract Recent advances in the technology of rotating liquid-mirrors now make feasible the construction of large optical telescopes for dedicated survey programs. Two three-metre-class astronomical telescopes have been built and asix-metre telescope is under construction. These instruments observe in zenith-pointing mode, using drift-scanning CCD cameras to record continuous imaging of a strip of sky typically 20 arcmin wide. This enables them to observe of order 100 square degrees of sky with an integration time of a few minutes per night. Data can be co-added from night to night in order to increase the depth of the survey. Liquid-mirror telescopes are particularly wellsuited to surveys using broad or intermediate bandwidth filters to obtain photometric redshifts and spectral energy distributions for faint galaxies and quasars.

scholarly journals Erratum: ProSpect: generating spectral energy distributions with complex star formation and metallicity histories

2020 ◽  
Vol 500 (3) ◽  
pp. 2859-2860
Author(s):  
A S G Robotham ◽  
S Bellstedt ◽  
C del P Lagos ◽  
J E Thorne ◽  
L J Davies ◽  
...  
Keyword(s):  
Star Formation ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions

scholarly journals Molecular Envelopes of Planetary Nebulae and Proto-Planetary Nebulae

1994 ◽  
Vol 140 ◽  
pp. 152-153
Author(s):  
Sun Kwok
Keyword(s):  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
High Rate ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Energy Distributions ◽  
Cool Component ◽  
Dust Envelope ◽  
Peak Energy

As stars evolve up the asymptotic giant branch (AGB), they begin to lose mass at a high rate, and in the process they create extended circumstellar molecular envelopes. Since the transition from AGB to planetary nebula stages is of the order of 1000 yr, the remnant of such molecular envelopes should still be observable in pro to-planetary nebulae (PPN) and planetary nebulae (PN). Recent ground-based survey of cool IRAS sources have discovered ~30 candidates of PPN (Kwok 1992). These sources show the characteristic “double-peak” energy distribution. The cool component is due to the remnant of the AGB dust envelope, and the hot component represents the reddened photosphere. The fact that the two components are clearly separated suggests that the dust envelope is well detached from the photosphere. Radiative transfer model fits to the spectral energy distributions of PPN suggest a typical separation of ~1 arc sec between the dust envelope and the photosphere, and such “hole-in-the-middle” structure can be mapped by millimeter interferometry in CO.

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