From szena@ludens.elte.hu Thu Aug 10 02:26:11 1995 Received: from kyohou.c.u-tokyo.ac.jp by chianti.c.u-tokyo.ac.jp (4.1/2.7W-utc1.9) id AA07589; Thu, 10 Aug 95 02:26:11 JST Received: from ludens.elte.hu by kyohou.c.u-tokyo.ac.jp (5.64/2.7W-utc1.9) id AA06209; Thu, 10 Aug 95 02:15:44 +0900 Return-Path: Received: by ludens.elte.hu (MX V4.1 VAX) id 29; Wed, 09 Aug 1995 19:17:33 +0200 Sender: szena@ludens.elte.hu Date: Wed, 09 Aug 1995 19:17:32 +0200 From: szena@ludens.elte.hu To: iau174_abstract@chianti.c.u-tokyo.ac.jp Cc: szena@ludens.elte.hu Message-Id: <00994A15.3D9D0680.29@ludens.elte.hu> Subject: Poster abstract ON THE POSSIBLE CONTRIBUTION OF dK AND dM STARS TO THE TOTAL MASS OF STAR CLUSTERS G. SZECSENYI-NAGY Department of Astronomy Eotvos Lorand University Budapest, VIII. Ludovika ter 2. H-1083 HUNGARY ABSTRACT dK and dM class stars or red dwarfs are intrinsically faint and cool objects and this explains why these abundant celestial bodies have remained undiscovered for such a long time. Visual observers of the pre-photographic era were able to list only a handful of this species and even the shockingly fruitful technique of astronomical photography had not been too productive in this field of astronomy, since the photosensitive layers of the early photographic plates were not sensi- tive in the yellow-red range of the spectrum. Each of the red dwarfs registered before the use of modern astrophotographic equipments (fast cameras and plates of enhanced {red} sensitivity) belonged to the immediate vicinity of the sun. It means that only those stars had been detected and located which were not farther than about 5 pc. However they turned out to be the most common of the stars soon as methods of distance determination evolved and a reliable sample of the solar neighbourhood could be compiled. The next step arrived with the invention of the Schmidt optical system, which offered the possibility of the detection of very faint stars in unprecedently wide regions of the sky simultaneously. We learned that these faint sources fill the volume of open clusters and other stellar groups too. The discovery of flare stars (a subclass of red dwarfs) offered a very effective tool for collecting more and more data about the dK/dM population of stellar systems. Applying some of the basic equations of statistics we were able to demonstrate that the traditional methods had never allowed the detection of very faint and red members of the clusters. Optical and NIR observations of these objects during the last decades allowed to estimate statistically the most probable number and percentage of the red dwarf population. It turned out to be in the 65-80 % range i.e. the absolute majority of the stars in star clusters as well as in the solar vicinity belong to the red dwarf class. Stellar populations of significantly more distant regions can not be investigated making use of the conventional methods but the state of the art telescopes, detectors and methods open new doors of the cosmos. The capacity of some of the best devices in the extension of these studies to the distance range of the globular clusters of the Milky Way and even the Magellanic Clouds will be discussed to finish with. This study was supported by NSRF of Hungary Grant No. OTKA-T007595. From iau174 Thu Aug 10 22:26:36 1995 Received: by chianti.c.u-tokyo.ac.jp (4.1/2.7W-utc1.9) id AA15077; Thu, 10 Aug 95 22:26:35 JST Date: Thu, 10 Aug 95 22:26:35 JST From: iau174 Message-Id: <9508101326.AA15077@chianti.c.u-tokyo.ac.jp> To: makino Subject: [IAU 174 abstract 10 ] Status: R >From szena@ludens.elte.hu Thu Aug 10 22:23:44 1995 Received: from kyohou.c.u-tokyo.ac.jp by chianti.c.u-tokyo.ac.jp (4.1/2.7W-utc1.9) id AA15044; Thu, 10 Aug 95 22:23:44 JST Received: from ludens.elte.hu by kyohou.c.u-tokyo.ac.jp (5.64/2.7W-utc1.9) id AA06826; Thu, 10 Aug 95 22:13:15 +0900 Return-Path: Received: by ludens.elte.hu (MX V4.1 VAX) id 3; Thu, 10 Aug 1995 15:14:33 +0200 Sender: szena@ludens.elte.hu Date: Thu, 10 Aug 1995 15:14:32 +0200 From: szena@ludens.elte.hu To: iau174_abstract@chianti.c.u-tokyo.ac.jp Cc: szena@ludens.elte.hu Message-Id: <00994ABC.755F0940.3@ludens.elte.hu> Subject: abstract (final version) ON THE POSSIBLE CONTRIBUTION OF dK AND dM STARS TO THE TOTAL MASS OF STAR CLUSTERS G. SZECSENYI-NAGY Department of Astronomy Eotvos Lorand University Budapest, VIII. Ludovika ter 2. H-1083 HUNGARY ABSTRACT dK and dM class stars or red dwarfs are intrinsically faint and cool objects and this explains why these abundant celestial bodies have remained undiscovered for such a long time. Visual observers of the pre-photographic era were able to list only a handful of this species and even the shockingly fruitful technique of astronomical photography had not been too productive in this field of astronomy, since the photosensitive layers of the early photographic plates had extremely low QE in the yellow-red band of the spectrum. Each of the red dwarfs registered before the use of modern astrophotographic equipments (fast cameras and plates of enhanced {red} sensitivity) belonged to the immediate vicinity of the sun. It means that only those stars had been detected and located which were not farther than about 5 pc. However they turned out to be the most common of the stars soon as methods of distance determination evolved and a reliable sample of the solar neighbourhood could be compiled. The next step arrived with the invention of the Schmidt optical system, which offered the possibility of the detection of very faint stars in unprecedently wide regions of the sky simultaneously. We learned that these faint sources filled the volume of open clusters and other stellar groups too. The discovery of flare stars (a subclass of red dwarfs) offered a very effective tool for collecting more and more data about the dK/dM population of stellar systems. Applying some of the basic equations of statistics we were able to demonstrate that the traditional methods had never allowed the detection of the faintest (red) members of the clusters. Optical and NIR observations of these objects during the last decades allowed to estimate statistically the most probable number and percentage of the red dwarf population. Their contribution to the total membership is at least 65 % and more probably about three quarters. Consequently the absolute majority of the stars in star clusters, associations as well as in the solar vicinity belong to the red dwarf class. Stellar populations of significantly more distant regions can not be investigated making use of the conventional methods but the state of the art telescopes, detectors and methods open up new vistas to the universe. The capacity of the most prospective devices and sophisticated methods in the possible extension of these studies into the distance range of the globular clusters of the Milky Way and even the Magellanic Clouds will also be discussed. This study was supported by NSRF of Hungary Grant No. OTKA-T 7595.