Садржај
Слике
Уплоадјуј своје слике
DSS Images Other Images
Везани чланци
Spitzer Survey of the Large Magellanic Cloud: Surveying the Agents of a Galaxy's Evolution (SAGE). I. Overview and Initial Results
We are performing a uniform and unbiased imaging survey of the LargeMagellanic Cloud (LMC; ~7deg×7deg) using theIRAC (3.6, 4.5, 5.8, and 8 μm) and MIPS (24, 70, and 160 μm)instruments on board the Spitzer Space Telescope in the Surveying theAgents of a Galaxy's Evolution (SAGE) survey, these agents being theinterstellar medium (ISM) and stars in the LMC. This paper provides anoverview of the SAGE Legacy project, including observing strategy, dataprocessing, and initial results. Three key science goals determined thecoverage and depth of the survey. The detection of diffuse ISM withcolumn densities >1.2×1021 H cm-2 permits detailed studies of dust processes in the ISM. SAGE'spoint-source sensitivity enables a complete census of newly formed starswith masses >3 Msolar that will determine the current starformation rate in the LMC. SAGE's detection of evolved stars withmass-loss rates >1×10-8 Msolaryr-1 will quantify the rate at which evolved stars injectmass into the ISM of the LMC. The observing strategy includes two epochsin 2005, separated by 3 months, that both mitigate instrumentalartifacts and constrain source variability. The SAGE data arenonproprietary. The data processing includes IRAC and MIPS pipelines anda database for mining the point-source catalogs, which will be releasedto the community in support of Spitzer proposal cycles 4 and 5. Wepresent initial results on the epoch 1 data for a region near N79 andN83. The MIPS 70 and 160 μm images of the diffuse dust emission ofthe N79/N83 region reveal a similar distribution to the gas emissions,especially the H I 21 cm emission. The measured point-source sensitivityfor the epoch 1 data is consistent with expectations for the survey. Thepoint-source counts are highest for the IRAC 3.6 μm band and decreasedramatically toward longer wavelengths, consistent with the fact thatstars dominate the point-source catalogs and the dusty objects detectedat the longer wavelengths are rare in comparison. The SAGE epoch 1point-source catalog has ~4×106 sources, and more areanticipated when the epoch 1 and 2 data are combined. Using Milky Way(MW) templates as a guide, we adopt a simplified point-sourceclassification to identify three candidate groups-stars without dust,dusty evolved stars, and young stellar objects-that offer a startingpoint for this work. We outline a strategy for identifying foreground MWstars, which may comprise as much as 18% of the source list, andbackground galaxies, which may comprise ~12% of the source list.
| A photometric study of 11 massive stars in the Magellanic Clouds
We present and discuss VBLUW photometry of eleven massive stars in theMagellanic Clouds: the SMC stars AzV 121, AzV 136 = HD 5277 = R 10, AzV197, AzV 310 = R 26 and AzV 369; the LMC stars GV 80 = HD 32034 = R 62,GV 91 = HDE 268 819, GV 346 = HDE 269661 = R 111, GV 352 = HDE 269697,GV 423 = HDE 269953 = R 150 and GV 460 = HDE 270111. Only one G0 Ia SMCsupergiant is found to be variable, whereas all members of the LMCsample show definite variability. We find that roughly aboveM/M\sun = 25, supergiants become photometrically unstable.The reddening-independent metal-index [B-L] is used to investigate themetallicity of the late-type supergiants in both galaxies relative tosimilar supergiants in the solar neighbourhood.
| Light variations of massive stars (α Cyg variables). XIX. The late-type supergiants R 59, HDE 268822, HDE 269355, HDE 269612 and HDE 270025 in the LMC
We present and discuss VBLUW photometry (Walraven system) of fivesupergiants in the LMC. For one well-known variable, the hypergiant R 59= HDE 268757 (G7 Ia+) also Hipparcos photometry and numerousvisual observations are available. The second variable is HDE 269612 (F0Ia), and a third one is HDE 268822 (F6 Ia). Two F6 Ia supergiants turnedout to be constant: HDE 269355 and HDE 270025.Partly based on observations obtained at the European SouthernObservatory at La Silla, Chile.
| Light variations of massive stars (alpha Cyg variables). XVIII. The B[e] supergiants S 18 in the SMC and R 66 = HDE 268835 and R 126 = HD 37974 in the LMC
We discuss photometric monitoring (VBLUW system) of three B[e]supergiants. All three objects appear to be variable. They are subjectto two (R 66 and R 126 in the LMC) and three (S 18 in the SMC) types oflight oscillations which range from a few days to years, and areprobably due to pulsations. We argue that a classification as alpha Cygvariables is justified. Their classification as mixed B[e]/S Dorvariables is less certain, though not impossible. Also based on othercases, a strong B[e]-S Dor variable connection seems to be present.Based on observations obtained at the European Southern Observatory atLa Silla, Chile.
| Light variations of massive stars (alpha Cygni variables). XVII. The LMC supergiants R 74 (LBV), R 78, HD 34664 = S 22 (B[e]/LBV), R 84 and R 116 (LBV?)
Multi-colour photometry (Walraven system) of five super- and hypergiantsin the LMC, viz. R 74, R 78, HD 34664, R 84 and R 116, is searched forvariability and periods, and discussed. Apart from R 84, of which theclaimed variability in the past must be due to a number of faint fieldstars at the edge of the apertures, all are variable. R 74 and HD 34664are weak-active LBVs with superimposed microvariations. HD 34664 is thesecond known B[e] star which is also an LBV. The first reported one is R4 in the SMC. This could alter some views on the evolutionary history ofB[e] stars and LBVs. R 78 is an alpha Cyg variable, but presumably noLBV. R 116 appears to be a close counterpart of the galactic ex-/dormantLBV zeta (1) Sco, also showing an intricate alpha Cyg-type multi-periodmicrovariability. Based on observations obtained at the EuropeanSouthern Observatory at La Silla, Chile}
| VBLUW photometry of fifteen alpha CYG variables (including LBVs) in the Galaxy, the LMC and the SMC
VBLUW photometry (Walraven system) of 15 alpha Cyg-type variables,(luminous massive stars), including 10 LBVs and one suspected LBV arepresented. Formulae are given to transform the V and V-B of the Walravensystem to V and B-V of the Johnson UBV system.
| Light variations of massive stars (alpha Cyg variables). XVI. The LMC supergiants R 85 (LBV) and R 110 (LBV) and the SMC supergiants R 42 and R 45
Multi-colour photometry of four variable supergiants in the LMC and SMC,viz. R 85, R 110, R 42 and R 45, is searched for periods, studied anddiscussed. The suspected LBV R 85 is undoubtedly an active LBV, thoughnot as spectacular as R 110. Their microvariations superimposed on the SDor-activity are analyzed as well as those exhibited by R 42 and R 45.Often, a period search is difficult because of the very complicatedmicro-variability. We suggest that this is caused by an intricatemulti-cyclic behaviour combined with stochastic processes. The length ofthe strongest cyclicity in the power spectrum of R 42 (128 d) is of theorder of the rotation periods of BA-type supergiants. In connection withour findings described in the present paper and the previous ones, wediscuss various competing theoretical models on the instability of alphaCyg variables, including the LBVs. Based on observations obtained at theEuropean Southern Observatory at La Silla, Chile (observing proposals55D-0317, 56D-0249, 57D-0133 and 58D-0118)
| Light variations of massive stars (alpha Cyg variables). XV. The LMC supergiants R99 (LBV), R103, R123 (LBV) and R128
VBLUW photometry (Walraven system) of the four variable LMC supergiantsR99, R103, R123 and R128 is analysed, searched for periods anddiscussed. Based on former and present photometry we conclude that twoof the three emission-line objects are undoubtedly active LBVs (R99 andR123), although not so spectacular. R123, like AG Car near minimumbrightness, shows a low amplitude S Dor activity with superimposed alphaCyg-type variations. Based on observations obtained at the EuropeanSouthern Observatory at La Silla, Chile
| Light variations of massive stars (α Cygni variables). XIV. The hypergiant WRA 977=BP CRU and the luminous blue variable (LBV) HDE 269582=HV 5495 in the LMC.
We present and discuss new multi-colour photometry of the massive X-raybinary and hypergiant WRA 977=BP Cru and the luminous blue variable(LBV) HDE 269582=HV 5495 in the LMC. The light variations of WRA 977 aretypical for a normal α Cyg variable and show an averagequasi-period of 11.90d over a time interval of 17yr. The distance couldbe as large as 7.7+/-2.3kpc. The light variations of HDE 298582=HV5495=MWC 112, showing a timescale of 1-2yr, have an amplitude of0.3-0.5mag. This points to an LBV near minimum light. The colourvariation is also typical for an LBV.
| Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...79S&db_key=AST
| An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
| Positional reference stars in the Magellanic Clouds
The equatorial coordinates are determined of 926 stars (mainly ofgalactic origin) in the direction of the Magellanic Clouds at the meanepoch T = 1978.4 with an overall accuracy characterized by the meanvalues of the O-C coordinates, Sa = 0.35 arcsec and Sd = 0.38 arcsec,calculated from the coordinates of the Perth reference stars. Thesevalues are larger than the accuracy expected for primary standard stars.They allow the new positions to be considered as those of reliablesecondary standard stars. The published positions correspond to anunquestionable improvement of the quality of the coordinates provided inthe current catalogs. This study represents an 'astrometric step' in thestarting of a 'Durchmusterung' of the Magellanic Clouds organized by deBoer (1988, 1989).
| Light variations of massive stars (Alpha Cygni variables). X - The F type supergiants G266 = HDE271182 = R92 and G322 = HDE269612 in the LMC
The results of VBLUW photometric observations of two massive variablestars in the LMC, the hypergiant G266 = HDE271182 = R92 (F8Ia/+/) andthe supergiant G322 = HDE269612 (FoIa) are presented and compared tothose for HD33486 star. Evidence is presented that indicates that thesemassive objects are no Cepheids, as was suggested by Grieve et al.(1985), but are Alpha Cyg variables. The highly unstable periods andlight curves recorded for both variables suggest that the observedinstability must be caused by a mechanism different from that acting inCepheids. The progressive change of light amplitudes and quasi-periodsfor massive stars from the left-hand to the right-hand side of the HRdiagram (Genderen, 1989) strongly suggests an evolutionary sequence fromO-type to G-type supergiants.
| The new long-period Cepheid G458 = HDE270100 in the Large Magellanic Cloud
VBLUW photometry of the long-period Cepheid in the LMC G458 = HD270100with a period P of 74.0 d is presented. The characteristics in the twocolor diagrams suggest that its metal abundance is higher than that forthe other LMC Cepheids. A theoretical HR diagram is presented whichindicates the fundamental blue edge, some P = constant lines for thesecond crossing, and the position of the two Cepheids G 458 and HV 2827.
| UBV (RI)c standard stars in the E- and F-regions and in the Magellanic Clouds - a revised catalogue.
Not Available
| An investigation of the micro-variations of highly luminous OBA stars (Alpha CYG variables). VI - The characteristics of the S DOR type stars R71 and AG CAR
The microvariations of R71 and AG Car when both were at minimumbrightness (1986-1987) were investigated based upon VBLUW photometry.For R71, a characteristic time scale of 14.3 d is found, and it is shownthat the amplitude, mean brightness, and colors stayed constant. Acharacteristic time scale of 13.8 d is found for AG Car, and it issuggested that the V-B and (B-V)j color indices of AG Car need to becorrected for the contribution of emission lines in the blue part of thespectrum. New reddenings obtained for the two stars are higher thanthose used previously.
| UBV(RI)c photometry of some standard sequences in the Harvard F regions and in the Magellanic Clouds
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1988MNRAS.231.1047M&db_key=AST
| Zero-Point Checks of Magellanic Cloud Sequences
Not Available
| A New Long-Period Cepheid in the LMC
Not Available
| Revised UBV photometry of Magellanic Cloud sequences
The old photometry of UBV secondary standards in the Magellanic Clouds(Cousins 1970) has been revised. New measurements made at Sutherland arepresented and analyzed.
| A distance modulus of the LMC from UVBY beta photometry of B supergiants
Stromgren four-color and H-beta photometry has been obtained for 44 Bsupergiants in the Large Magellanic Cloud. As expected, nearly one-halfof them have beta indices which suggest emission at H-beta. From 24stars which appear to be free from this emission, thebeta/c0/M(v) calibration of Balona and Shobbrook (1984),applied with a correction to the beta index for the mean radial velocityof the LMC stars, indicates a distance modulus of 18.8 + or - 0.3.
| An investigation of the micro-variations of highly luminous OBA type stars. III - The S DOR type star R 71 = HDE 169006 in the LMC
VBLUW photometry of the LMC S Dor type star R 71 = HDE 269006 ispresented and discussed. It appears that the star similar to other highluminous OB type stars shows optical micro variations. The lightamplitude is ≡0m.1 and the typical time scale≡20d. The star fits well into the PLC relation forvariable supergiants, suggesting that some type of pulsation is thecause. Contrary to a few other normal B type supergiants, the lightcurves of individual cycles are smooth and the V-B and B-L colours varyin anti-phase with each other. The largest colour variations usuallyoccur in the B-U viz. ≡0m.02 (the U band contains theBalmer jump).
| VBLUW photometry of Cepheids in the Magellanic Clouds made in 1971-1978
Light and color curves and the periods of 21 SMC and 20 LMC Cepheidsstudied with VBLUW photometry between 1971 and 1978 are discussed.Improved periods are given and their variations are addressed. Newformulas for the epochs of maximum light are given. Almost all theCepheids show period variations in the range of less than one percent upto a few percent. Only one Cepheid shows definite light curve changes,while two others may show changes in their light curves.
| A high-resolution optical survey of interstellar absorption lines toward globular clusters and extragalactic objects. II - Further data
A status report is given on an ongoing survey of narrow-line, visualabsorption components, which has been expanded to include lines of sightto the 3C 273 quasar, the nucleus of M87, and the NGC 1851, NGC 2808,and 47 Tuc globular cluster cores. The number density of components ofthe halo is calculated to lie between one-third and one per 100 kpc,though with substantial uncertainty. This estimate is held to beconsistent with the galactic halo interpretation of the origin of highcolumn density, quasar absorption-line systems.
| Long time baseline VBLUW photometry of four of the most luminous LMC supergiants HD 33579, HD 35343=S Dor, HDE 268757 and HDE 269006. I
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979A&AS...38..151V&db_key=AST
| Long-term light variations of four supergiants in the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/abs/1978A&A....64..243F
| Standard Stars for VRI Photometry with S25 Response Photocathodes
Not Available
| A Probable Periodicity in the Light Variation of the LMC Supergiant HD 33579
Photometry of the brightest supergiant of the LMC HD 33579 in 1971,1972, 1973 and 1974 shows evidence for a periodicity of around 90 days.The nature is probably pulsation.
| Radial velocities from objective-prism plates in the direction of the Large Magellanic Cloud. List of 398 stars, LMC members. List of 1434 galactic stars, in the LMC direction
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...13..173F&db_key=AST
| A Search for Light Variations in Some Supergiants in the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/abs/1971ApJ...169..281R
|
Додај нови чланак
Линкови у сродству са темом
Додај нови линк
Чланови следећих група \:
|
Посматрања и Астрометриски подаци
| Сазвежђа: | Златна риба |
| Ректацензија: | 05h05m06.66s |
| Deклинација: | -68°05'11.2" |
| Apparent магнитуда: | 7.848 |
| Даљина: | 495.05 parsecs |
| Proper motion RA: | 8 |
| Proper motion Dec: | 3.6 |
| B-T magnitude: | 7.822 |
| V-T magnitude: | 7.846 |
Каталог и designations:
|
