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The Luminosity and Mass Functions of Low-Mass Stars in the Galactic Disk. I. The Calibration Region
We present measurements of the luminosity and mass functions of low-massstars constructed from a catalog of matched Sloan Digital Sky Survey(SDSS) and Two Micron All Sky Survey (2MASS) detections. Thisphotometric catalog contains more than 25,000 matched SDSS and 2MASSpoint sources spanning ~30 deg2 on the sky. We have obtainedfollow-up spectroscopy, complete to J = 16, of more than 500 low-massdwarf candidates within a 1 deg2 subsample, and thousands ofadditional dwarf candidates in the remaining 29 deg2. Thisspectroscopic sample verifies that the photometric sample is complete,uncontaminated, and unbiased at the 99% level globally, and at the 95%level in each color range. We use this sample to derive the luminosityand mass functions of low-mass stars over nearly a decade in mass (0.7 Msun > M * > 0.1 M sun). Theluminosity function of the Galactic disk is statistically consistentwith that measured from volume-complete samples in the solarneighborhood. We find that the logarithmically binned mass function isbest fit with an Mc = 0.29 log-normal distribution, with a90% confidence interval of Mc = 0.20-0.50. These 90%confidence intervals correspond to linearly binned mass functionspeaking between 0.27 M sun and 0.12 M sun, wherethe best fit MF turns over at 0.17 M sun. A power-law fit tothe entire mass range sampled here, however, returns a best fit ofα = 1.1 (where the Salpeter slope is α = 2.35); a brokenpower law returns α = 2.04 at masses greater than log M =-0.5 (M = 0.32 M sun), and α = 0.2 at lowermasses. These results agree well with most previous investigations,though differences in the analytic formalisms adopted to describe thosemass functions, as well as the range over which the data are fit, cangive the false impression of disagreement. Given the richness ofmodern-day astronomical data sets, we are entering the regime wherebystronger conclusions can be drawn by comparing the actual datapointsmeasured in different mass functions, rather than the results ofanalytic analyses that impose structure on the data a priori. Havingvalidated this method to generate a low-mass luminosity function frommatched SDSS/2MASS data sets, future studies will extend this techniqueto the entirety of the SDSS footprint.Based in part on observations obtained with the Apache Point Observatory3.5 m telescope, which is owned and operated by the AstrophysicalResearch Consortium.
| The effect of activity on stellar temperatures and radii
Context: Recent analyses of low-mass eclipsing binary stars haveunveiled a significant disagreement between the observations andpredictions of stellar structure models. Results show that theoreticalmodels underestimate the radii and overestimate the effectivetemperatures of low-mass stars but yield luminosities that accord withobservations. A hypothesis based upon the effects of stellar activitywas put forward to explain the discrepancies. Aims: In this paper westudy the existence of the same trend in single active stars and providea consistent scenario to explain systematic differences between activeand inactive stars in the H-R diagram reported earlier. Methods: Theanalysis is done using single field stars of spectral types late-K and Mand computing their bolometric magnitudes and temperatures throughinfrared colours and spectral indices. The properties of the stars insamples of active and inactive stars are compared statistically toreveal systematic differences. Results: After accounting for a numberof possible bias effects, active stars are shown to be cooler thaninactive stars of similar luminosity therefore implying a larger radiusas well, in proportions that are in excellent agreement with those foundfrom eclipsing binaries. Conclusions: The present results generalisethe existence of strong radius and temperature dependences on stellaractivity to the entire population of low-mass stars, regardless of theirmembership in close binary systems.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/478/507
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| The Palomar/MSU Nearby Star Spectroscopic Survey. III. Chromospheric Activity, M Dwarf Ages, and the Local Star Formation History
We present high-resolution echelle spectroscopy of 676 nearby M dwarfs.Our measurements include radial velocities, equivalent widths ofimportant chromospheric emission lines, and rotational velocities forrapidly rotating stars. We identify several distinct groups by theirHα properties and investigate variations in chromospheric activityamong early (M0-M2.5) and mid (M3-M6) dwarfs. Using a volume-limitedsample together with a relationship between age and chromosphericactivity, we show that the rate of star formation in the immediate solarneighborhood has been relatively constant over the last 4 Gyr. Inparticular, our results are inconsistent with recent large bursts ofstar formation. We use the correlation between Hα activity and ageas a function of color to set constraints on the properties of L and Tdwarf secondary components in binary systems. We also identify a numberof interesting stars, including rapid rotators, radial velocityvariables, and spectroscopic binaries. Observations were made at the 60inch telescope at Palomar Mountain, which is jointly owned by theCalifornia Institute of Technology and the Carnegie Institution ofWashington.
| An H-alpha survey of neglected Vyssotsky Catalog stars
Consideration is given to a significant number of Vyssotsky K- andM-dwarfs that have either no published radial velocity (71 stars), or avelocity based on a single measure (22), or with an uncertaintly greaterthan 5 km/s (19). An 'in flare' observation of Vys 250A compared to itsquiescent state, and an example of the double-lined phase of Vys 250Bare illustrated. Mean values from the observations are given in tabularform.
| The Palomar/MSU Nearby Star Spectroscopic Survey.II.The Southern M Dwarfs and Investigation of Magnetic Activity
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2799H&db_key=AST
| Space Motions of Low-Mass Stars. II: Radial Velocities
Radial velocities are presented for 53 dwarf K and M stars, eight ofwhich are radial velocity standards. This is the second list in aprogram to determine space motions for all of the stars in the McCormicklists of dwarf stars. The observations reported here differ from thoseof the first list in that they were made using the 1.88m David Dunlapreflector. One of the stars varies in radial velocity, consistent with aspectroscopic binary with a period of about 48 days. (SECTION: Stars)
| The Palomar/MSU Nearby-Star Spectroscopic Survey. I. The Northern M Dwarfs -Bandstrengths and Kinematics
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.1838R&db_key=AST
| Photometry of dwarf K and M stars
An observational program using UBVRI photometry is presented for 688stars from among the dwarf K and M stars already found spectroscopicallyby Vyssotsky (1958). Of these, 211 have not been observedphotometrically. These observations were obtained over a period ofseveral years at the Kitt Peak National Observatory using a GaAsphotomultiplier with an 0.9 m reflector. Based on night-to-nightvariations in the measures of individual stars, the internal errors maybe estimated to be roughly 0.01 mag for the colors and 0.015 for the Vmagnitudes. The photometric parallaxes reported for each star werecomputed in the manner discussed by Weis (1986).
| Preliminary Version of the Third Catalogue of Nearby Stars
Not Available
| Photovisual magnitudes of 418 dwarf M stars and 34 parallax stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61..219S&db_key=AST
| Dwarf M stars found spectrophotometrically .
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61..201V&db_key=AST
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | לינכס |
| התרוממות ימנית: | 07h35m21.88s |
| סירוב: | +54°50'59.1" |
| גודל גלוי: | 11.377 |
| מרחק: | 13.104 פארסק |
| תנועה נכונה: | -118.1 |
| תנועה נכונה: | 25.5 |
| B-T magnitude: | 13.437 |
| V-T magnitude: | 11.548 |
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