Van Biesbroeck Research Articles

Evolution of Low-Mass Stars. II. Effects of Primordial Deuterium Burning and a Nongray Surface Condition during Pre-Main Sequence Contraction

view Abstract Citations (17) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evolution of Low-Mass Stars. II. Effects of Primordial Deuterium Burning and a Nongray Surface Condition during Pre-Main Sequence Contraction Grossman, A. S. ; Mutschlecner, J. P. ; Pauls, T. A. Abstract The lifetime of the deuterium main sequence has been investigated for stars in the mass range 0.03-0.2 M0 at the composition X = 0.68, Y = 0.29, and Xn = 0.t9X 10- . The duration of the deuterium main sequence for an i/Hp ratio of I varies from 2.4 X 106 years at 0.2 M0 to 2.3 X t0 years at 0.03 M0* The theoretical I/Hp = I hydrogen main sequence has been determined, and we show that a 0.08 M0 star will reach a stable main-sequence phase in about S X 10 years. The mass limit for a star of this composition on the main sequence is between 0.07 and 0.08 M0. We also make the suggestion that van Biesbroeck's star might actually be a main-sequence member at or near the lower mass limit. Incorporated into the calculation of the surface boundary condition are nongray, flux-corrected model atmospheres which are used to approximate the thin outer radiative surface layers in the region of the photosphere. Water-vapor and CO opacity sources are included in these model atmospheres. The malor effect of the new surface condition is to shift the theoretical main sequence toward lower luminosities and effective temperatures. Publication: The Astrophysical Journal Pub Date: November 1970 DOI: 10.1086/150693 Bibcode: 1970ApJ...162..613G full text sources ADS | data products SIMBAD (1) Related Materials (4) Part 1: 1970ApJ...161..619G Part 3: 1971ApJ...164..475G Part 4: 1971ApJ...170..363G Part 5: 1973ApJ...180..195G

Orbit of Comet 1960 II (Burnham)

view Abstract Citations (4) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Orbit of Comet 1960 II (Burnham) van Biesbroeck, G. ; Marsden, B. G. Abstract An improved orbit has been calculated from almost 200 observations covering an arc of nearly six months. A systematic trend still remains in the residuals and this must be attributed to difficulties in measuring the comet when it was close to the earth, for it was then very diffuse. It would be hard to believe that the result- ing "original" slightly hyperbolic nature of the orbit is real, but the period of the comet is undoubtedly ex- tremely long a fact that appears to contradict the supposition from spectral evidence that this comet is very old. Publication: The Astronomical Journal Pub Date: October 1963 DOI: 10.1086/109182 Bibcode: 1963AJ.....68..566V full text sources ADS |

Mass and Nuclear Dimensions of Comet Wirtanen, 1957 VI.

The nucleus of the comet discovered on 16 March, 1956 by C. A. Wirtanen at the Lick Observatory was found to be double on 1 May 1957 by G. Van Biesbroeck with the 82-inch reflector of the McDonald Observatory. The two nuclei were separately measurable on plates obtained at Lick, at McDonald, and at the Flagstaff Station of the U. S. Naval Observatory during 1957,1958, and 1959. Results of astrometric measures of some 60 plates obtained at Flagstaff are presented. The available data indicate that disruption of the nucleus of the comet occurred within a few days of 1January 1957. The velocity of separation projected on the sky was about 1.5 m/sec. Under appropriate assumptions, dynamical information on the mass of Comet Wirtanen is obtained. Linear dimensions of the two nuclei are derived from photographic estimates of their respective brightuesses, a range of values of the albedo being assumed.

On the Nature of van Biesbroeck's Star +4 4048B.

view Abstract Citations (4) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Nature of van Biesbroeck's Star +4 4048B. Kumar, Shiv S. Abstract Van Biesbroeck's star BD t404048 (B) is the intrinsically faintest known star (Mv = 18.6). Kron has given a color temperature of about 20000K and color index (P- V) =2.33 for this star. It is most probably a star of late M spectral type. Making use of these data and the theory of stars of very low mass, the following tentative conclusions are made about its structure and evolution: (1) It is not a main sequence star; i.e., hydrogen burning is not the source of energy production inside it. It is contracting slowly. (2) Its mass is less than 0.07 Mo. (3) It is a degenerate star that is slowly approaching the black dwarf stage. However, the possibility of its being a main sequence star of mass -0.07 is not completely ruled out. Observational data for 726-8 and the unseen planetary companions, which are most probably degenerate stars of very low mass, are also discussed. Publication: The Astronomical Journal Pub Date: June 1963 DOI: 10.1086/108965 Bibcode: 1963AJ.....68..283K full text sources ADS |

Orbit of Comet 1954 V (Abell)

view Abstract Citations References (1) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Orbit of Comet 1954 V (Abell) van Biesbroeck, G. ; Marsden, B. G. Abstract Although the comet was not discovered until over a year past perihelion, a satisfactory representation of the 34 available observations has been made. The hyperbolic excess of the osculating orbit is 19 times its mean error, but the "original" orbit was found to be quite definitely elliptical. Publication: The Astronomical Journal Pub Date: April 1963 DOI: 10.1086/108941 Bibcode: 1963AJ.....68..212V full text sources ADS |

THREE-COLOR PHOTOELECTRIC OBSERVATIONS OF THE INTRINSICALLY FAINTEST STAR KNOWN

The faint companion of the M3 dwarf BD +4°4048, discovered by G. Van Biesbroeck, has the lowest luminosity of any known star. Interest in this unusual object was recently stimulated by Herbig's success in obtaining three spectrograms of it last year with the Crossley reflector.1 These indicated the presence of TiO bands in its spectrum, but it was concluded by Herbig that the spectral type corresponding to their strength was later than that of Wolf dM6e. The photographic absolute magnitude of Wolf 359 is about +18. 5,2 several magnitudes brighter than Van Biesbroeck's star. The spectroscopic observations suggest that BD +4°4048(B) may be no cooler than Wolf 359, although below a certain temperature, of course, the TiO bands would not be expected to increase steadily in strength with decreasing temperature. Thus photometric observations that might give information on the temperature of this very faint star should prove of considerable interest. Observations of this object were made recently by the writer with the photoelectric equipment of the Crossley reflector, and its magnitude was determined in the blue, yellow, and infrared spectral regions. The blue and yellow measurements were made with a refrigerated 19-stage multiplier having an Sb-Cs cathode, while the infrared measurement was made with a refrigerated 12-stage multiplier having a CsO-Ag cathode. Both multipliers were made in the laboratory of A. Lallemand in Paris, and were kindly furnished by him. The measurements were made by means of an ordinary d.c. direct-coupled, constant-deflection amplifier, and the photometer was modified by the Observatory instrument maker, Mr. Raymond Greeby, to permit work on invisible objects by offsetting from a nearby visible star. The magnitudes obtained are given in Table I. The P and

The mass of Neptune from a new orbit of its second satellite Nereid

view Abstract Citations (16) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The mass of Neptune from a new orbit of its second satellite Nereid van Biesbroeck, G. Abstract . An orbit correction for Nereid is obtained from 37 observations with the 8 -inch McDonald reflector in seven oppositions, 1949-1955. The reciprocal of Neptune's mass in terms of the sun's mass is found to be 18889 + 62. Publication: The Astronomical Journal Pub Date: October 1957 DOI: 10.1086/107532 Bibcode: 1957AJ.....62..272V full text sources ADS |

Traité de l' Astrolabe. Henri Michel

Previous articleNext article No AccessReviews Traité de l' Astrolabe . Henri Michel G. Van BiesbroeckG. Van Biesbroeck Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Isis Volume 39, Number 3Aug., 1948 Publication of the History of Science Society Article DOIhttps://doi.org/10.1086/348967 Views: 1Total views on this site Citations: 1Citations are reported from Crossref Copyright 1948 History of Science SocietyPDF download Crossref reports the following articles citing this article: George Sarton , and Frances Siegel Seventy-Third Critical Bibliography of the History and Philosophy of Science and of the History of Civilization (To November 1948), Isis 40, no.22 (Oct 2015): 124–193.https://doi.org/10.1086/349039

Total Solar Eclipse of May 20: Preliminary Reports

Contrary to all expectation, based on the usual weather conditions in May, the expeditions to the west coast of Africa to observe the total solar eclipse of May 20 were uniformly successful, whereas those to Brazil were upset by cloudy conditions. In Santiago in Chile, conditions were cloudy but observations were made from an aeroplane above the clouds. The corona was reported as of the minimum type with equatorial streamers and polar plumes—an unusual form so near sunspot maximum. At Araxá in Brazil, the Czechoslovak party and the Swedish party under Dr. Öhman were clouded out. At Bocayuva, the Finnish party was able to carry out its time observations for the geodetic programme. The party at the same place from the American Geographical Society, the Georgetown University, Washington, and the Yerkes Observatory reports only partial success owing to clouds. Dr. van Biesbroeck secured plates of the star-field around the sun for the Einstein effect, and photographs of the corona and of its spectrum; accurate time observations of the contacts were obtained. Photographs were taken from an A.A.F. B 17 plane flying at 30,000 ft.; also a programme of ionospheric observations was successfully carried through.

The light curve of comet 1942g.

Comet I942 (Whipple) showed more remarkable fluctuations in brightness than any comet heretofore studied. The light curve is based on 146 observations reduced to the author's "system f" which is the total brightness of the comet observed by him with a -21-inch finder. The author's observations are based on 708 estimates and are discussed in Contr butions from the Perk ns Observatory Xo. 19, 1943. Other observations used for the light curve are: Ashbrook ;1 Martinoff, Bakharev, Lange ;2 Miss Farnsworth and Miss Pillans (unpublished); and Van Biesbroeck (unpublished). The light curve from January 5 to July 3, 1943 shows a periodic variation in light with a period of about 30 days and the semi-amplitude diminishing from o.6 mag. in January to 0.2 mag. in June. Such a diminution of the amplitude was previously observed in Comets 1902 III and 1912 11.1 However, in the present case there was a rather sudden increase in brightness on about February 21. The comet then began decreasing in brightness but faster than before. The result is that it is impossible to represent the brightness of the comet by any one formula. Before February 10 and after April 15 the brightness can be expressed as follows: H= 6.6o 5logA $5logr periodicterm. Between these dates, however, the following formula represents the observed brightness: H = 4.00 Y 5logA Y ~logr Y periodicterm. In spite of the change in brightness by 1.40 mag. and the accelerated decrease in brightness, the length of the period of intrinsic variation and even the phase did not change at all. Sudden changes in the light curve have been found previously for Comets 1858 VI, 1862 III, and 1884 I. Comet 1942f is unique in the combination of a sudden change with a distinctly periodic variation preserved throughout its period of observation of half a year. It is also remarkable in the closeness of the times of the nearest approach to the earth, January 28, and perihelion passage, February 6, which places the theoretical maximum of brightness between these two dates, about a month before the actually observed maximum. There is also evidence of minor fluctuations in brightness of a semi- periodic character. I.fop. Astr. 51, 362, 1943. 2.Astr. Circ. Acad. Sci. U.S.S.R. Nos. 12 and `3, `943. 3.Contr. Perkins Obs. No. ifi, 1942. Perkins Observatory, Delaware, Ohio.

Discovery of Comet Giacobina-Zinner

AN I.A.U. telegram from Copenhagen announces that this comet was discovered by van Biesbroeck on October 15 at 1h. 17·1m. U.T. Its position is given as R.A. 16h. 21m. 27·4s., N. Dec. 1° 18′ 53″. It is described as diffuse with central condensation, magnitude 15. In the “Handbook of the British Astronomical Association, 1939”, the elements and ephemeris of this comet are given by Mr. F. R. Cripps, who applied the perturbations of Jupiter and Saturn to the 1933 elements. The comet is very close to the predicted position, and it is only necessary to make the corrections for perihelion passage 0·25d. later than that given in the “Handbook”.

Commission 26. (Double Stars.)

The President read the draft report. No objections being entered, this was adopted by the meeting.The President proposed an addition to the report. This was agreed to.The adoption of a single system of orbital elements was advocated by van den Bos, who reported on the correspondence which had taken place on this subject with the members. As the result of all answers received, a system of elements was proposed and adopted by the Committee.The President suggested that this be given in the report and van den Bos, at the request of van Biesbroeck, proposed that a full set of definitions and formulae be added. This was agreed to.

Commission 6. (Telegrams.)

Sir Frank Dyson submitted the following resolution, which was seconded by Prof. Van Biesbroeck, and carried:“The Commission recommends that the yearly subsidy of £66, granted since 1928 by the Union to the Central Bureau of Telegrams, be continued.”The President described some proposals of modifications to the European code which he thought desirable. By using time instead of arc for Right Ascension, and Declination instead of Polar Distance, anybody receiving a telegram would be able to read it directly, without any computations, whereas its security would remain sufficient. This code is, in the main, similar to one which Prof. Förster had suggested many years ago.

Commission 26. (Double Stars.)

It was agreed to send a message of congratulation to Dr R. G. Aitken on the occasion of the completion of the A .D.S., a copy of which was for inspection on the table of the chairman.Aside from minor alterations and additions which were discussed in reading the Draft Report, the Committee adopted this report as printed and designated a subcommittee for the purpose of working out a short list of double stars situated between + 10° and − 10° declination for the investigation of personal errors. C. P. Olivier, who initiated this proposal, will act as chairman of the sub-committee, which will include R. G. Aitken, H. N. Russell, and G. Van Biesbroeck.

Observations of comets (completed by G. Van Biesbroeck, with the assistance of Miss M.Calvert and Mrs. A. Pierce), (IV)

Observations of comets (completed by G. Van Biesbroeck, with the assistance of Miss M.Calvert and Mrs. A. Pierce), (IV)

Observations of comets (completed by G. Van Biesbroeck, with the assistance of Miss M.Calvert and Mrs. A. Pierce), (III)

Observations of comets (completed by G. Van Biesbroeck, with the assistance of Miss M.Calvert and Mrs. A. Pierce), (III)

Observations of comets (completed by G. Van Biesbroeck, with the assistance of Miss M.Calvert and Mrs. A. Pierce), (I)

Observations of comets (completed by G. Van Biesbroeck, with the assistance of Miss M.Calvert and Mrs. A. Pierce), (I)

Observations of comets (completed by G. Van Biesbroeck, with the assistance of Miss M.Calvert and Mrs. A. Pierce), (II)

Observations of comets (completed by G. Van Biesbroeck, with the assistance of Miss M.Calvert and Mrs. A. Pierce), (II)

Astronomical Topics

Comet Ryves, 1931c.—This comet was first seen by Mr. Ryves at Zaragoza on Aug. 10; he observed it almost daily up to Aug. 17, and noted that it was growing brighter. The only observation of position made elsewhere, so far as we know, was on Aug. 14 by Prof. G. van Biesbroeck, at Yerkes, who saw a tail one degree in length.

Astronomical Topics

New Bright Comet, 1931c.—Mr. P. M. Ryves, who is a fellow of the Royal Astronomical Society and a member of the British Astronomical Association, residing at Zaragoza, Spain, telegraphed to the U.A.I. Bureau at Copenhagen that he had discovered a comet of magnitude 5.5 approaching the sun. The following positions of Aug. 10 and 12 (which are probably only approximate) were obtained by him; that of Aug. 14 was obtained by Prof. G. van Biesbroeck at Yerkes Observatory, after receiving the announcement of the discovery: