An exceptionally bright flare from SGR 1806–20 and the origins of
... If observed from a great distance, only the brief, initial hard spike of the 27 December flare would be evident. Thus distant extragalactic magnetar flares (MFs) would resemble the mysterious shortduration GRBs31,32. These hard-spectrum events have long been recognized as a separate class of GRBs33– ...
... If observed from a great distance, only the brief, initial hard spike of the 27 December flare would be evident. Thus distant extragalactic magnetar flares (MFs) would resemble the mysterious shortduration GRBs31,32. These hard-spectrum events have long been recognized as a separate class of GRBs33– ...
Chemical abundances and winds of massive stars in M31: a Btype
... information on the distances of galaxies through the detailed study of the strengths of their radiatively driven winds using the wind momentum – luminosity relationship (hereafter WLR; Kudritzki et al. 1999). An investigation of the stellar wind properties of O-, B- and A-type supergiants in Local G ...
... information on the distances of galaxies through the detailed study of the strengths of their radiatively driven winds using the wind momentum – luminosity relationship (hereafter WLR; Kudritzki et al. 1999). An investigation of the stellar wind properties of O-, B- and A-type supergiants in Local G ...
Chemical abundances and winds of massive stars in M31: a B
... Numerous surveys have identified OB and WR stars beyond the Magellanic Clouds e.g. Massey et al. (1986); Moffat & Shara (1987), although little quantitative analysis has been carried out to date. The only detailed studies of WolfRayet stars beyond the Magellanic Clouds have been studies of late WN s ...
... Numerous surveys have identified OB and WR stars beyond the Magellanic Clouds e.g. Massey et al. (1986); Moffat & Shara (1987), although little quantitative analysis has been carried out to date. The only detailed studies of WolfRayet stars beyond the Magellanic Clouds have been studies of late WN s ...
A COMPREHENSIVE COMPARISON OF THE SUN TO
... above the solar value ( Table 3). This can also be done by a joint analysis of multiple parameters ( Table 2). If there are several subtle factors that have some influence over habitability, a quantitative joint analysis of the Sun’s properties may allow us to identify these factors without invoking ...
... above the solar value ( Table 3). This can also be done by a joint analysis of multiple parameters ( Table 2). If there are several subtle factors that have some influence over habitability, a quantitative joint analysis of the Sun’s properties may allow us to identify these factors without invoking ...
UvA-DARE (Digital Academic Repository)
... constellations in the night sky. The existence of such a disk was first postulated in the 18th century by Kant (1755). Although the protoplanetary disk around the Sun has long since been dispersed, part of its history can still be reconstructed through studying the meteoritic record that traces the ...
... constellations in the night sky. The existence of such a disk was first postulated in the 18th century by Kant (1755). Although the protoplanetary disk around the Sun has long since been dispersed, part of its history can still be reconstructed through studying the meteoritic record that traces the ...
99 Herculis: Host to a Circumbinary Polar
... To try and resolve this issue we obtained an adaptive optics image of 99 Her at L’ (3.8 µm) using the NIRC2 camera at Keck II on July 27, 2011, shown in Figure 3. We adopted the narrow camera (10 mas/pixel) and used a five-point dither pattern with three images obtained at each position consisting o ...
... To try and resolve this issue we obtained an adaptive optics image of 99 Her at L’ (3.8 µm) using the NIRC2 camera at Keck II on July 27, 2011, shown in Figure 3. We adopted the narrow camera (10 mas/pixel) and used a five-point dither pattern with three images obtained at each position consisting o ...
CO GAS INSIDE THE PROTOPLANETARY DISK CAVITY IN HD
... listed in Table 2, the observed emission from channels at velocities <+1.8 km s−1 and >+5.4 km s−1 is radiated by gas material contained in a radius of 140 AU (∼1 ), thus coming entirely from inside the dust-depleted cavity. We note that gas emission coming from very near the central star shows si ...
... listed in Table 2, the observed emission from channels at velocities <+1.8 km s−1 and >+5.4 km s−1 is radiated by gas material contained in a radius of 140 AU (∼1 ), thus coming entirely from inside the dust-depleted cavity. We note that gas emission coming from very near the central star shows si ...
Analytic Models for the Mechanical Structure of the Solar Core
... In the homogeneous ZAMS Sun, 1 + ne ≡ d ln P/d ln(P/ρ) is identical to 1 + N ≡ d ln P/d ln T ≡ 1/∇ and varies from the almost adiabatic value 2.52 at z = 0 to a maximum value 5.21 at z = 0.32 (r = 0.506 of ZAMS solar radius). Where the radiative zone meets the convective core, 1 + ne shows a discont ...
... In the homogeneous ZAMS Sun, 1 + ne ≡ d ln P/d ln(P/ρ) is identical to 1 + N ≡ d ln P/d ln T ≡ 1/∇ and varies from the almost adiabatic value 2.52 at z = 0 to a maximum value 5.21 at z = 0.32 (r = 0.506 of ZAMS solar radius). Where the radiative zone meets the convective core, 1 + ne shows a discont ...
Supernovae - University of Texas Astronomy Home Page
... A new chapter in this story was written by the Chandra X-Ray Observatory launched on July 23, 1999. After astronomers had searched for decades with other instruments, the Chandra Observatory found the compact object that was demanded to exist in the remnant of this massive star. Ironically, the very ...
... A new chapter in this story was written by the Chandra X-Ray Observatory launched on July 23, 1999. After astronomers had searched for decades with other instruments, the Chandra Observatory found the compact object that was demanded to exist in the remnant of this massive star. Ironically, the very ...
Beta Pictoris and Other Solar Systems
... initially to β Pic (cf. Artymowicz, 1997). However, the effects of radiation are quite similar in different systems (e. g., Artymowicz and Clampin, 1997). For instance, the luminosity differences between the stars will simply shift the ‘blow-out grain radius’ but will not change the characteristic s ...
... initially to β Pic (cf. Artymowicz, 1997). However, the effects of radiation are quite similar in different systems (e. g., Artymowicz and Clampin, 1997). For instance, the luminosity differences between the stars will simply shift the ‘blow-out grain radius’ but will not change the characteristic s ...
IAC_L3_thickdisk
... the disk, e.g. via Jeans equation. Is there more matter in the disk that we can account for from census of visible objects ? The tracer sample must be in equilibrium so the stars need to be older than a few Gyr. The last few estimates have used K dwarfs and K giants - probably OK but they do include ...
... the disk, e.g. via Jeans equation. Is there more matter in the disk that we can account for from census of visible objects ? The tracer sample must be in equilibrium so the stars need to be older than a few Gyr. The last few estimates have used K dwarfs and K giants - probably OK but they do include ...
The density of very massive evolved galaxies to z≃ 1.7
... densities are likely to be lower limits because of the incompleteness of our spectroscopic observations (13 spectra collected out of the 19 EROs in the field). In order to compare these densities with the local values, we integrated the K-band luminosity function (LF) of local early-type galaxies, d ...
... densities are likely to be lower limits because of the incompleteness of our spectroscopic observations (13 spectra collected out of the 19 EROs in the field). In order to compare these densities with the local values, we integrated the K-band luminosity function (LF) of local early-type galaxies, d ...
Conditions for water ice lines and Mars-mass
... Our main findings were that (1) super-Jovian planets at 5.2 AU around Sun-like stars have their H2 O ice lines between about 15 and 30 Jupiter radii (RJup ) during the late stages of accretion, when the final generation of moons form. This range is almost independent of the planetary mass (Mp ). (2) ...
... Our main findings were that (1) super-Jovian planets at 5.2 AU around Sun-like stars have their H2 O ice lines between about 15 and 30 Jupiter radii (RJup ) during the late stages of accretion, when the final generation of moons form. This range is almost independent of the planetary mass (Mp ). (2) ...
Presolar Cloud Collapse and the Formation and Early Evolution of
... Once a cloud begins to collapse as a result of ambipolar diffusion or triggering by a shock wave, supersonic inward motions develop and soon result in the formation of an optically thick first core, with a size on the order of 10 AU. This central core is supported primarily by the thermal pressure o ...
... Once a cloud begins to collapse as a result of ambipolar diffusion or triggering by a shock wave, supersonic inward motions develop and soon result in the formation of an optically thick first core, with a size on the order of 10 AU. This central core is supported primarily by the thermal pressure o ...
The Formation and Evolution of Massive Black Holes - Ira-Inaf
... MBHs become visible when they accrete gas directly from their surroundings, or, occasionally, when they disrupt an unlucky star passing too close by (20). The gravitational potential energy of the accreted mass is converted to radiation, making the black hole luminous. Luminous, accreting MBHs are g ...
... MBHs become visible when they accrete gas directly from their surroundings, or, occasionally, when they disrupt an unlucky star passing too close by (20). The gravitational potential energy of the accreted mass is converted to radiation, making the black hole luminous. Luminous, accreting MBHs are g ...
X-ray emission from supernova shock waves Tanja Kramer Nymark Department of Astronomy
... interaction with a circumstellar medium. In particular the reverse shock created by the interaction is investigated. In most Type IIL and Type IIn supernovae this shock is radiative, and due to the high temperature most of the radiation comes out as X-rays. A numerical model is presented which calcu ...
... interaction with a circumstellar medium. In particular the reverse shock created by the interaction is investigated. In most Type IIL and Type IIn supernovae this shock is radiative, and due to the high temperature most of the radiation comes out as X-rays. A numerical model is presented which calcu ...
a fresh catch of massive binaries in the cygnus ob2 association
... MT070 is noteworthy as the longest period system yet measured in Cyg OB2, with P = 6.2 yr. The other four systems have periods ranging between 4 and 73 days. MT174 is noteworthy for having a probable mass ratio q < 0.1, making it a candidate progenitor to a low-mass X-ray binary. These measurements ...
... MT070 is noteworthy as the longest period system yet measured in Cyg OB2, with P = 6.2 yr. The other four systems have periods ranging between 4 and 73 days. MT174 is noteworthy for having a probable mass ratio q < 0.1, making it a candidate progenitor to a low-mass X-ray binary. These measurements ...
Altair -- the ``hottest`` magnetically active star in X-rays
... brightness during our 2 × 2 exposures, that are separated by 14 days and cover in total roughly 35 h of observation time. In Fig. 1 we show the count rate in the 0.2–2.0 keV band as measured by the EPIC, i.e. summed PN and MOS, instrument in time-steps of half an hour. While clearly no strong flares ...
... brightness during our 2 × 2 exposures, that are separated by 14 days and cover in total roughly 35 h of observation time. In Fig. 1 we show the count rate in the 0.2–2.0 keV band as measured by the EPIC, i.e. summed PN and MOS, instrument in time-steps of half an hour. While clearly no strong flares ...
Radiation pressure from massive star clusters as a launching
... At early times, i.e. less than a few Myr after a massive star cluster forms, the forces acting on the surrounding material include only radiation pressure and shocked stellar winds. The first supernovae explode after about 4 Myr. Observations show that massive star clusters disrupt GMCs both in the ...
... At early times, i.e. less than a few Myr after a massive star cluster forms, the forces acting on the surrounding material include only radiation pressure and shocked stellar winds. The first supernovae explode after about 4 Myr. Observations show that massive star clusters disrupt GMCs both in the ...
The Milky Way and Andromeda galaxies in a constrained
... For Milky Way-mass galaxies, the most efficient feedback mechanism is believed to be that produced by stars, via the injection of energy into the interstellar medium during different phases of stellar evolution. In particular, various models for feedback from supernovae (SNe) have been included in simu ...
... For Milky Way-mass galaxies, the most efficient feedback mechanism is believed to be that produced by stars, via the injection of energy into the interstellar medium during different phases of stellar evolution. In particular, various models for feedback from supernovae (SNe) have been included in simu ...
Cygnus X-1
Cygnus X-1 (abbreviated Cyg X-1) is a well-known galactic X-ray source, thought to be a black hole, in the constellation Cygnus. It was discovered in 1964 during a rocket flight and is one of the strongest X-ray sources seen from Earth, producing a peak X-ray flux density of 6977229999999999999♠2.3×10−23 Wm−2 Hz−1 (7003230000000000000♠2.3×103 Jansky). Cygnus X-1 was the first X-ray source widely accepted to be a black hole and it remains among the most studied astronomical objects in its class. The compact object is now estimated to have a mass about 14.8 times the mass of the Sun and has been shown to be too small to be any known kind of normal star, or other likely object besides a black hole. If so, the radius of its event horizon is about 7004440000000000000♠44 km.Cygnus X-1 belongs to a high-mass X-ray binary system about 7019574266339685654♠6070 ly from the Sun that includes a blue supergiant variable star designated HDE 226868 which it orbits at about 0.2 AU, or 20% of the distance from the Earth to the Sun. A stellar wind from the star provides material for an accretion disk around the X-ray source. Matter in the inner disk is heated to millions of degrees, generating the observed X-rays. A pair of jets, arranged perpendicular to the disk, are carrying part of the energy of the infalling material away into interstellar space.This system may belong to a stellar association called Cygnus OB3, which would mean that Cygnus X-1 is about five million years old and formed from a progenitor star that had more than 7001400000000000000♠40 solar masses. The majority of the star's mass was shed, most likely as a stellar wind. If this star had then exploded as a supernova, the resulting force would most likely have ejected the remnant from the system. Hence the star may have instead collapsed directly into a black hole.Cygnus X-1 was the subject of a friendly scientific wager between physicists Stephen Hawking and Kip Thorne in 1975, with Hawking betting that it was not a black hole. He conceded the bet in 1990 after observational data had strengthened the case that there was indeed a black hole in the system. This hypothesis has not been confirmed due to a lack of direct observation but has generally been accepted from indirect evidence.