From Stardust to Planetesimals: Contributed Papers - NASA Lunar ...

More documents

Recommendations

Info

4. DISCUSSION AND CONCLUSIONSWe have shown that V351 Ori changed from a Herbig Ae star with strong photometricvariations to a almost non-variable one. Such a change had previously only beenobserved in the Herbig Ae star BN Ori around 1947 (Shevchenko et al. 1996). Afirst conclusion that can be drawn from the fact that we have actually been able toobserve such transitions in the relatively short period these stars have been observedsystematically, is that such transitions from Herbig Ae stars with strong photometricvariations to almost non-variable ones must occur quite often during the evolution ofsuch stars towards the main-sequence. This also implies that the reverse process mustoccur frequently.Since before .JD 2446000 the photometric variations of V351 Ori were caused bydust clouds orbiting the star, it seems that around this date some event started whicheither destroyed the dust in these clouds, or moved the dust clouds from our line ofsight. This event continued until JD 2448200, after which the star rapidly becamenearly constant in brightness. So far, we can only speculate about the cause of thisevent. It could be that it is correlated with a temporarily strong accretion of dustonto the star. Such an event will be accompanied by shock-fronts which create anextremely hot gaseous disk near the equatorial plane close to the star. This hotoptically thick gaseous disk blocked part of the visual and blue light of the star,causing a visual brightness decrease of about 0°'2. At the same time, this hot objectradiates ultraviolet energy superposed on that of the central star. This is causing theincrease of the ultraviolet brightness of the star. When the accretion of dust stops, thevisual and blue stellar light regain its maximum brightness, whereas the ultravioletcontribution of the hot disk disappears, and the ultraviolet brightness drops.Since all infrared observations of V351 Ori were made during the period in whichthe star still showed photometric variations, it is very important to obtain new infraredphotometry of this object. If the dust clouds close to the star have indeedaccreted onto the central star, we should expect to see a clear decrease of the infraredexcess of the star. Further optical monitoring of V351 Ori remains necessary to seewhether the dust clouds start to re-occur, in which case the star will become variableonce more.ReferencesBeckwith, S.V.W., Sargent, A.I., Chini, R.S., Gusten, R. 1990, A. J. 99, 924Chkhikvadze, J.N. 1990, Bull. Abastumani Astroph. Obs. 68, 43Kilkenny, D., Whittet, D.C.B., Davies, J.K., Evans, A., Bode, M.F., Robson, E.I.,Banfield, R.M. 1985, SAAO Circ. 9,55Koval'chuk, G.U. 1985, Kinem. Fizika Nebesn. Tel. 1, 30Kurucz, R.L. 1991, in Precision photometry: Astrophysics of the galaxy, ed. A.G.Davis Philip, A.R. Upgren, K.A..Janes, L. Davis press, Schenectady, New YorkShevchenko, V.S., Ezhkova, 0., Tjin A Djie, H.R.E., van den Ancker, M.E., Blondel,P.F.C., de Winter, D. 1996, Astr. Ap., in pressZajtseva, G.V. 1986, Astrofizika 25, 47136
DUST AROUND HERBIG AE STARS:ADDITIONAL CONSTRAINTS FROM THEIRPHOTOMETRIC AND POLARIMETRIC VARIABILITYN. A. KRIVOVA Institute of Astronomy, Nicholas Copernicus University,Torun, PolandV. B. IL'IN MPG Research Unit "Dust in Star-Forming Regions", Jena,Germany0. FISCHER Astrophysical Institute, Jena University, Jena, GermanyABSTRACT. For the Herbig Ae stars with Algol-like minima (UX Ori, WW Vul,etc), the effects of circumstellar dust include: excess infrared emission, anomalousultraviolet extinction, the "blueing" of the stars in minima accompanying by an increaseof intrinsic polarization. Using a Monte-Carlo code for polarized radiationtransfer we have simulated these effects and compared the results obtained for differentmodels with the observational data available. We found that the photometric andpolarimetric behaviour of the stars provided essential additional constraints on thecircumstellar dust models. The models with spheroidal shell geometry and compact(non-fluffy) dust grains do not appear to be able to explain all the data.1. INTRODUCTIONThe dust in the vicinity of Herbig Ae stars (HAe) is responsible for the majority of theobservational manifestations of the objects — excess emission in the infrared (IR),anomalous extinction in the ultraviolet (UV) and visual, and intrinsic polarization —and is thought to be a possible source material for the formation of planetesimalsand planets. For a numerous group of HAe stars with large (up to 2 mag) brightnessvariations (UX Ori, WW Vul, etc.), the "blueing" effect in the color-magnitude diagrams(CMD) and the increase of the intrinsic polarization are also observed in deepminima.The best studied objects of this group are BF Ori, UX Ori, WW Vul, and CQ Tau.Table 1 gives some observed parameters of the stars: visual magnitude in the brightstates (m), the range of the brightness falls (Am,,,,,,,), the polarization degree in thebright (Pb ) and faint (Pf ) states, and the degree of interstellar polarization (PIS).To simulate the observational effects mentioned above we apply spheroidal modelsof the shell. Our main intention here is to examine whether such models are able toaccount for the data available for the stars.37
Page 1 and 2: NASA Conference Publication 3343Fro
Page 3 and 4: PREFACEOn June 24 through 26, 1996,
Page 5 and 6: TABLE OF CONTENTSPreface...........
Page 7 and 8: The role of hydrogen in small amorp
Page 9: P PIC AND SIMILAR DISK-LIKE OBJECTS
Page 12 and 13: y linear deconvolution of the SSA i
Page 14 and 15: `planetesimals'. Those ones are spa
Page 16 and 17: o Variations of the size of the blo
Page 18 and 19: Table 1 Best-fitting model paramete
Page 20 and 21: 10-10SAO 179815 (HD 98800)10-1110-1
Page 22 and 23: 2. 0 Pic-like SYSTEMSOne of the gre
Page 24 and 25: Backman, D. E., and Paresce, F. 199
Page 27 and 28: PARTIALLY CRYSTALLINE SILICATE DUST
Page 29 and 30: 12D 100546 vs Forsterite (dashed) a
Page 31 and 32: HIGH RESOLUTION SPECTROSCOPY OF VEG
Page 33 and 34: accretion hypothesis, King (1994) i
Page 35 and 36: TRANSIENT ACCRETION EVENTS IN HERBI
Page 37 and 38: e ionized by the stellar radiation
Page 39: STAR FORMATION31
Page 42 and 43: 1980 1985 1990 19959.09.5®rIL10.01
Page 46 and 47: 2. SHELL MODELThe dusty envelope is
Page 48 and 49: — "Fluffiness" of dust particles.
Page 50 and 51: 2. OBSERVATIONSThe observations wer
Page 52 and 53: 1050.015^ ^o.,a •,o a0s0au0—5
Page 54 and 55: IMAGING POLARIZED DUST EMISSION IN
Page 56 and 57: Figure 3. The total intensity (left
Page 58 and 59: 0fvac = 0.3(dot), 0.5(dash), 0.7(li
Page 60 and 61: lo`lo'00axto-,00a10 -20lo-''10' to
Page 63 and 64: EXTERNALLY INDUCED EVAPORATION OF Y
Page 65 and 66: 0-6—7—8—9v -10OD0Dispersal Ra
Page 67: CIRCUMSTELLAR DUST59
Page 70 and 71: Table 1 SiC features and the Temper
Page 72 and 73: have very similar absorption featur
Page 74 and 75: mSE1 .-SE3 -SE4U NA iLtSE5 --SE6 SE
Page 76 and 77: 3. CARBON STARSSloan, Little-Mareni
Page 78 and 79: eferences therein). The arc dischar
Page 80 and 81: the time scale of their evolution:
Page 82 and 83: easily amended for any chemical spe
Page 84 and 85: 25002000a^a^H150010001 2 3 4r/Rstar
Page 86 and 87: 2. METHODThe stellar wind model is
Page 88 and 89: 0 0.04(a)3007EU200(b)0.03Ec 0.02^s0
Page 90 and 91: 0 CETIX = 8-9 µm ,(off dust featur
Page 92 and 93: Examining a number of grain types,
Page 95 and 96:
REVISED DEPLETIONS AND NEW CONSTRAI
Page 97 and 98:
- 1 -Table 1.__Revised stellar and
Page 99:
ReferencesAannestad, P. 1995, ApJ,
Page 102 and 103:
3.02.52.0CL1.51.00.50.03 4 5 61 /X
Page 104 and 105:
ReferencesAnderson, C.M. et al. 199
Page 106 and 107:
2.1. ExtinctionInfrared photometry
Page 109 and 110:
THE EXTINCTION PROPERTIES OFHEAVILY
Page 111 and 112:
3. ANALYSISUsing a Quantimet Q520 i
Page 113 and 114:
HAC: BAND GAP, PHOTOLUMINESCENCE, A
Page 115 and 116:
3.2. The 3.4 micron Absorption Band
Page 117 and 118:
THE ROLE OF HYDROGEN IN SMALL AMORP
Page 119 and 120:
R 100an'c30w 0 Wa.AE-50A 1C.q-t0.5x
Page 121 and 122:
OBSERVATIONS OF TWO NON-STANDARD GR
Page 123 and 124:
where VSGs break off larger grains
Page 125 and 126:
IRAS COLORS OF THE PLEIADESSEAN J.
Page 127 and 128:
4. IDENTIFICATION OF DENSE (MOLECUL
Page 129 and 130:
PAH EMISSION IN THE ORION BARJESSE
Page 131 and 132:
0.80.60.40.20.8N 0.60.4DN 0.2^ E b:
Page 133 and 134:
LABORATORY EXPERIMENTS ON THE REACT
Page 135 and 136:
500Cto 8+ + 0 ®> CgH8+ + CO400AvrA
Page 137 and 138:
433v02110 30 60 90 120 150 180 210F
Page 139 and 140:
PROCESSING OF ICY MANTLES IN PROTOS
Page 141 and 142:
tions of mixtures each provide exce
Page 143 and 144:
THE ICE AND SILICATE SPECTRAL FEATU
Page 145 and 146:
2.5Model C (a= 1µm)—f=0.2-'1 - -
Page 147 and 148:
EVIDENCE FOR THE EVOLUTION OF GRAIN
Page 149 and 150:
(a) Ih2FIRS,_I(h}p 56^LOo . o FIR4'
Page 151 and 152:
THE ABUNDANCES OF CHARGED PARTICLES
Page 153 and 154:
2.3. Grain Charge TransferIn order
Page 155 and 156:
THE PROTOSOLAR NEBULA147
Page 157 and 158:
CATALYSIS BY DUST GRAINS IN THE SOL
Page 159 and 160:
Figure 1 shows the steps involved i
Page 161 and 162:
(e.g., surface-catalyzed) ones. Thi
Page 163 and 164:
RESTRUCTURING OF DUST AGGREGATES IN
Page 165 and 166:
3. AN EXAMPLE CALCULATIONWe have in
Page 167 and 168:
EFFECT OF DUST COAGULATION DYNAMICS
Page 169 and 170:
NUMERICAL SIMULATIONS FOR SUM KERNE
Page 171 and 172:
SELF-CONSISTENT SIMULATION OF THE B
Page 173 and 174:
and a diffusivity Di = Tfi kT/mi. D
Page 175 and 176:
DUST COAGULATION IN PROTOPLANETARYA
Page 177 and 178:
Coogulction tit?- )e• zn /5139,5
Page 179 and 180:
SIZE SEGREGATION AND NUMBER DENSITY
Page 181 and 182:
10`1100.01 cm . . . . .0.1 cm . . .
Page 183 and 184:
FROM CHONDRULES TO PLANETESIMALS:SO
Page 185 and 186:
Figure 2. Regions of high particle
Page 187 and 188:
VORTICES AND PLANETESIMALSP. BARGE
Page 189 and 190:
c0UdWU)0 10 -1ULUiCROSSING * ` yAjr
Page 191 and 192:
THE ROLE OF VORTICES IN THE FORMATI
Page 193 and 194:
(a)(b)(c)606060Y40 ,^ Y40 OOY402020
Page 195 and 196:
THE GLOBAL PERSPECTIVE ON THE EVOLU
Page 197 and 198:
103102 ..........................10
Page 199 and 200:
TOWARD AN ASTROPHYSICAL THEORY OFCH
Page 201 and 202:
and the subsolar temperatureTsub..I
Page 203 and 204:
PLANETESIMAL FORMATION IN THE OUTER
Page 205 and 206:
3. SUBLIMATION, CONDENSATION, AND G
Page 207 and 208:
PLANETESIMALS AND COMETS199
Page 209 and 210:
THE MASS OF LARGE IMPACTORSM. G. PA
Page 211 and 212:
99 3JupiterNeptuneA0 20 — 0.00 0.
Page 213 and 214:
TIDAL BREAKUP OF ASTEROIDS BY THE E
Page 215 and 216:
Figure 2. Time sequence showing the
Page 217 and 218:
ON THE DYNAMICS OF THE ZODIACAL DUS
Page 219 and 220:
de Log U®ro 1 — E2dt aysw Ecos z
Page 221 and 222:
DUST AND SPUTTERED PARTICLE STREAMS
Page 223 and 224:
A"P -0.1s^nntU 8 -- -3.2- - 3.6-- 3
Page 225 and 226:
PRELIMINARY RESULTS OF OBSERVATIONS
Page 227 and 228:
4. ULYSSES COMET WATCH NETWORKIn 19
Page 229 and 230:
POROSITY AND PERMEABILITY OF CHONDR
Page 231 and 232:
from the dessi cation of such a "we
Page 233 and 234:
5. POROSITY MEASUREMENTS OF BULK CH
Page 235 and 236:
RAMAN SPECTRUM OF QUENCHEDCARBONACE
Page 237 and 238:
Raman shift (Acm -1)1000 1300 1600
Page 239 and 240:
AUTHOR INDEXAdamson, A.J. 101,131 G
Page 241 and 242:
SUBJECT INDEXabundances, cosmic 89a
Page 243 and 244:
plasma 216,218polarization 38, 39,
Page 245 and 246:
OBJECT INDEXAB Aur 20R Cas 15O Ceti
Page 247 and 248:
ADDRESSES OF PARTICIPANTS239
Page 249 and 250:
Nancy AgeorgesEmma BakesESONASA Ame
Page 251 and 252:
Max BernsteinJurgen BlumNASA Ames R
Page 253 and 254:
Connie ChangSimon ClemettHarvard Un
Page 255 and 256:
Jamie ElsilaMarina FomenkovaKalamaz
Page 257 and 258:
Mayo GreenbergUniv. of LeidenHuygen
Page 259 and 260:
Dan JudnickJohn F. Kerridge5702 Cal
Page 261 and 262:
John KulanderOliver LayP.O. Box 704
Page 263 and 264:
Vito MennellaDaffel MoonObservatori
Page 265 and 266:
Pendleton YvonneSun Hong RhieNASA A
Page 267 and 268:
Anneila SargentRussell ShipmanCalif
Page 269 and 270:
Prof. Stanislav SvirschevskyHead of
Page 271 and 272:
Christoffel WaelkensFrancis P. Wilk
Page 273:
REPORT DOCUMENTION PAGEForm Approve
show all

From Stardust to Planetesimals: Contributed Papers - NASA Lunar ...

Create successful ePaper yourself

Delete template?

Save as template?