scholarly journals FOC Observations of SN 1987A

1992 ◽  
Vol 9 ◽  
pp. 471-474
Author(s):  
N. Panagia
Keyword(s):  
Narrow Band ◽  
Hubble Space Telescope ◽  
Accurate Determination ◽  
Angular Size ◽  
Variable Stars ◽  
Light Curves ◽  
Absolute Size ◽  
Sn 1987A ◽  
Elliptical Ring

AbstractWe present and discuss the first images of SN 1987A obtained on day 1278 with the FOC on board the Hubble Space Telescope. The supernova is well detected and resolved spatially in the four observed bands. The UV luminosity of SN 1987A is found to be comparable to that emitted in the visible and infrared spectrum. Narrow-band [OUI] imaging reveals that the circumstellar nebula surrounding SN 1987A has the shape of a perfectly elliptical ring, implying an inclination of 43° ±3°. A comparison of the ring angular size with its absolute size derived from an analysis of the light curves of narrow UV lines measured with IUE, gives an accurate determination of the distance to SN 1987A, i.e. d(1987A) = 51.2±3.1 kpc. Allowing for the relative position of SN 1987A within the LMC, the distance to the center of the LMC turns out to be 50.1 ± 3.1 kpc. This value agrees very well with the determinations obtained from light curve analyses of variable stars.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

scholarly journals Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ring Rabs = (6.23 ± 0.08) x 1017 cm and an angular size R″ = 808 ± 17 mas, which give a distance to the supernova d(SN1987A) = 51.4 ± 1.2 kpc and a distance modulus m–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to be d(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus of m–M(LMC) = 18.58±0.05.

scholarly journals A Geometric Determination of the Distance to SN 1987A and the LMC

2005 ◽  
Vol 192 ◽  
pp. 585-592 ◽  
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A ◽  
Original Analysis

SummaryUsing the definitive reductions of the IUE light curves by [15] and an extensive set of HST images of SN 1987A we have repeated and improved our original analysis [8, 9] to derive a better determination of the distance to the supernova. In this way we have obtained an absolute size of the ring Rabs = (6.23 ± 0.08) × 1017 cm and an angular size R″ = 808 ± 17 mas, which give a distance to the supernova d(SN1987A) = 51.4±1.2 kpc and a distance modulus (m − M)sN1987A = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to be d(LMC) = 51.7±1.3 kpc, which corresponds to a distance modulus of (m − M)LMC = 18.56 ± 0.05.

scholarly journals A Precise Estimate of the Radius of HD 149026b

2008 ◽  
Vol 4 (S253) ◽  
pp. 466-469
Author(s):  
Philip Nutzman ◽  
David Charbonneau ◽  
Joshua N. Winn ◽  
Heather A. Knutson ◽  
Jonathan J. Fortney ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Stellar Mass ◽  
Radius Ratio ◽  
Light Curves ◽  
Heavy Elements ◽  
Precise Estimate ◽  
Extrasolar Planet ◽  
Orbital Inclination ◽  
Limb Darkening

AbstractWe present Spitzer 8 μm transit observations of the extrasolar planet system HD 149026b. At this wavelength, transit light curves are weakly affected by stellar limb-darkening, allowing for a simpler and more accurate determination of planetary parameters. We measure a planet-star radius ratio of Rp/R∗=0.05158±0.00077, and in combination with ground-based data and independent constraints on the stellar mass and radius, we derive an orbital inclination of i = 85°.4+0°.9−0°.8 and a planet radius of 0.755 ± 0.040 RJ. These measurements further support models in which the planet is greatly enriched in heavy elements.

Recent advances in X-ray astronomy

1967 ◽  
Vol 31 ◽  
pp. 439-453
Author(s):  
B. B. Rossi
Keyword(s):  
Accurate Determination ◽  
Angular Size ◽  
The State ◽  
Spectral Information ◽  
X Ray ◽  
Upper Limit ◽  
Recent Advances ◽  
Visible Object

In a review written in December 1965, the author of this report has summarized the state of observational X-ray astronomy at that time. Further data that have become available since then have produced important advances in several directions. New sources have been discovered, some of which have been tentatively identified with known galactic or extra-galactic objects. Evidence has been presented for variability of the X-ray flux received from at least one of the sources. New spectral information has been obtained. New observations of the strong X-ray source in Scorpius, Sco X-1, have greatly reduced the previous upper limit for its angular size and have provided a much more accurate determination of its celestial coordinates. This determination has led to the identification of Sco X-1 with a faint visible object whose peculiar properties had, until then, escaped the attention of astronomers.

scholarly journals Ground-Based and Space Observations of Interacting Binaries

2011 ◽  
Vol 7 (S282) ◽  
pp. 21-26
Author(s):  
Panagiotis G. Niarchos
Keyword(s):  
Binary Systems ◽  
Accurate Determination ◽  
Space Missions ◽  
Light Curves ◽  
Physical Parameters ◽  
Multi Wavelength ◽  
Low Mass ◽  
Space Observations

AbstractMulti-wavelength observational data, obtained from ground-based and space observations are used to compute the physical parameters of the observed Interacting Binaries (IBs) and study the interactions and physical processes in these systems. In addition, the database of IBs from ground-based surveys and space missions will provide light curves for many thousands of new binary systems for which extensive follow up ground-based observations can be carried out. In certain cases, light curves of superior quality will allow studies of fine effects of stellar activity and very accurate determination of stellar parameters. Moreover, many new discoveries of interesting systems are expected from ground-based all-sky surveys and space missions, including low mass binaries and star-planet binary systems. The most important current and future programs of observations of IBs from ground and space are presented.

Places of formation of young and moderately young stars

1967 ◽  
Vol 31 ◽  
pp. 323-329 ◽  
Author(s):  
Bengt Strömgren
Keyword(s):  
Spiral Structure ◽  
Narrow Band ◽  
Accurate Determination ◽  
Young Stars ◽  
Photoelectric Photometry ◽  
Peculiar Velocities ◽  
Stellar Ages ◽  
The Galaxy ◽  
Perseus Arm

Narrow-band photoelectric photometry can furnish classification indices allowing accurate determination of stellar ages. From these ages, together with well-determined space motions, the places of formation of stars, and their relationship to the spiral structure of the Galaxy, may be determined. This procedure has been successfully followed for 52 B8–B9 stars within 200 pc from the Sun. It turns out that seven of these have originated in the Perseus Arm, with local peculiar velocities of about 22 km/sec.A simple model is developed describing places of star formation in the Perseus Arm and velocities at formation. The distribution of space velocities and of ages for stars formed according to this model appears to be in agreement with observation.

scholarly journals First measurement of the total gravitational quadrupole moment of a black widow companion

2020 ◽  
Vol 494 (3) ◽  
pp. 4448-4453
Author(s):  
Guillaume Voisin ◽  
C J Clark ◽  
R P Breton ◽  
V S Dhillon ◽  
M R Kennedy ◽  
...  
Keyword(s):  
Quadrupole Moment ◽  
Accurate Determination ◽  
Light Curves ◽  
Orbital Eccentricity ◽  
Black Widow ◽  
Companion Star ◽  
Quadrupole Component ◽  
Timing Data ◽  
Orbital Precession

ABSTRACT We present the first measurement of the gravitational quadrupole moment of the companion star of a spider pulsar, namely the black widow PSR J2051–0827. To this end, we have re-analysed radio timing data using a new model that is able to account for periastron precession caused by tidal and centrifugal deformations of the star as well as by general relativity. The model allows for a time-varying component of the quadrupole moment, thus self-consistently accounting for the ill-understood orbital period variations observed in these systems. Our analysis results in the first detection of orbital precession in a spider system at $\dot{\omega } = -68{_{.}^{\circ}}6_{-0{_{.}^{\circ}}5}^{+0{_{.}^{\circ}}9}$ yr−1 and the most accurate determination of orbital eccentricity for PSR J2051–0827 with e = (4.2 ± 0.1) × 10−5. We show that the variable quadrupole component is about 100 times smaller than the average quadrupole moment $\bar{Q} = -2.2_{-1}^{+0.6} \times 10^{41} \ {\rm kg\,m^2}$. We discuss how accurate modelling of high-precision optical light curves of the companion star will allow its apsidal motion constant to be derived from our results.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

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