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22

It is not that it is blocked by the Sun, but that the duration of time for which it can be continuously observed was too small to be useful for the investigations performed in the paper. The object was observed by XMM-Newton, which has a highly eccentric ($e \sim 0.8$), 48-hour orbit arond the Earth. This is designed so that the satellite can stare for ...


19

Observations can be made using different parts of the electromagnetic spectrum. Many of them not within the range of the spectrum that can be made with optical telescopes. Other messengers than photons (e.g gravitational waves, neutrinos,...) can also be observed. Optical counterparts are observations made in the spectrum observable using optical ...


9

After a bit of searching, I found this blog page, which has several charts about various observatories, including this one: Image courtesy of Olaf Frohn under the Creative Commons Attribution-Share Alike 4.0 License. The majority are space-based, although the radio telescopes are largely land-based. They cover existing and future telescopes, at energies ...


7

Emission measure is (usually) used in X-ray and EUV astronomy, though I suppose also in cases of optically thin radio emission. It is defined as the square of the number density of free electrons integrated over the volume of the plasma. $${\rm EM} = \int n_e^2 \ dV$$ The flux of optically thin emission from a plasma (e.g. thermal bremsstrahlung) is then ...


7

The crusts of neutron stars will contain "super-heavy", neutron-rich nuclei. This is an inevitable consequence of the high density material, the accompanying degenerate electrons (that block $\beta$-decay) and what we know about nuclear physics. However, the only things that contribute to a neutron star's observable spectrum are materials within a few cm ...


6

GIFs too big to post here directly: 1, 2 NICER is all about time resolution and energy resolution and is used to collect the time and energy-resolved X-ray spectra from pulsars. It isn't an imaging telescope and so can't record "patches of the sky" like other devices can. The curved lines are the paths that the narrow field of view (FOV) of the NICER ...


4

Short answer, yes, the x-ray grazing incidence mirrors set up like this still function like a Cassegrain to minimize off-axis aberration. However, it is still different in that a classical Cassegrain uses a fast positive paraboloid and a slow negative hyperboloid. The Cassegrain design combines the paraboloid and hyperboloid to minimize off-axis aberrations ...


4

The answer can be found in the "Methods" section of the original Nature paper (Stefano et. al). I will try to give a brief sketch of what they did: First thing is, that the eclipsing object is not much larger that that of the emitting source. Only about 0.74 vs 0.43 Jupiter radii. This means you have not just an eclipsed point source, but two ...


4

If you go to the original article, you can see that it's something like this They have a plausible size for the X-ray-emitting source (that is, the X-ray-bright part of the accretion disk): $R = 2.5 \times 10^{9}$ cm, which is about 4 times the size of the Earth. (I think this comes from fitting the X-ray broadband spectrum before and after the putative ...


4

I think there is a missing piece of information. The BAT is a coded mask telescope. The imaging is done by photons passing through a mask and falling onto an array of 32768 detectors. http://swift.gsfc.nasa.gov/about_swift/bat_desc.html The "mask-weighted" light curve is produced after a complex ray tracing exercise using an estimate of the position of the ...


3

I think the answer is that it's primarily a matter of association on the sky, though there are some (weak) additional constraints. The first thing to note is that there are three observations that are associated on the sky: the X-ray emission (which has been known about since the mid 1990s), the newly detected 140 MHz LOFAR emission, and evidence for a ...


3

Conservation of mass? In a steady-state wind, the mass loss rate through each shell is the same. $$ \frac{dM}{dt} = - 4\pi r^2 \rho(r) v(r),$$ where $\rho$ and $v$ would be the density and velocity of a spherically symmetric wind, with a fixed mass-loss rate $\dot{M}$. Thus for a fixed wind speed you expect the density to fall as the square of the radius ...


3

The Hinode satellite has an active x-ray telescope that is routinely used to image the sun. And the NuSTAR extreme x-ray telescope can also be used for sun imaging (although its main job is looking for black holes) Here is the latest XRT image of Hinode There are also Extreme Ultraviolet telescopes (at 171Å that is less than an octave away from the ...


3

How does IXPE measure polarization? Short answer: Electrons in the detector are preferential emitted in the direction of the polarization of the incident photon and then detected. Quoting from NASA's IXPE: Polarization Detection page: IXPE will have three identical X-ray telescopes, with polarization detectors at each focus. The detectors, called Gas Pixel ...


2

Interesting question. I did a bit of reading and gave it some thought and and I can sort of give an answer, though I invite corrections and input from anyone more knowledgeable than me. First, those 2 galaxies are enormous. I didn't see specific sizes listed, but per this paper: 1.2-1.5 x 10^14 solar mass fossil group That's about 100 Andromeda ...


2

Long ago I was part of a group that flew high altitude balloons to study x-rays from pulsars etc. How much you detect and at what energy depends upon how much atmosphere is above your detector. Lower energy x-rays are absorbed more than higher energy x-rays. Realistically you won't detect anything except maybe the Sun at energies below 20 keV and at altitude ...


2

The physical difference between high- and low-mass X-ray binaries is that the latter has a donor star that fills its Roche lobe. Usually, the compact object is more massive than the donor star. Mass transfer occurs via Roche lobe overflow. In high-mass X-ray binaries usually the donor star is more massive than the compact object and mass transfer is via a ...


2

The source is Sco X-1. It is a point source of X-rays. I'll have get back to you on why it looks that way in chromoscope, but it looks incorrect to me.


2

The frequency is related to the redshift by $$\frac{\nu_{\rm obs}}{\nu_{\rm emit}} = \frac{1}{1+z}$$ Another useful relation is the fact that, for any redshift, $$\frac{I_{\nu}}{\nu^3} = {\rm constant}$$ where $I_{\nu}$ is the specific radiative intensity. The specific count rate (counts per area per time per energy interval) is proportional to $I_{\nu}/\...


2

X-Rays from the sun don't reach the Earth's surface, as our atmosphere is opaque to this kind of electromagnetic radiation. This is why X-Ray observatories like the Chandra telescope have to be placed in space. Thus it is excluded, that anybody having an ability to see X-Rays would see people's inner organs. The other issue is that in general, human ...


2

I am not an expert on the topic but probably you have to specify in your search which mass regime are you looking for (low or high mass x-ray binaries). Accretion time must be important and depends on the mass. High-mass stars are young (very short life) < $10^7$ years. This reference is quite old but probably helps a bit: The Average X-Ray Lifetime of ...


2

In this case itseems to mean that the depth of the line is 7 times its error bar below the continuum level. Impossible to answer. You say it can't be done, but the authors say that they fitted a Gaussian. You either use a rough estimate (attributable to Cayrel de Strobel 1988) of $$\Delta {\rm EW} \sim 1.5\frac{\sqrt{RP}}{{\rm SNR}},$$ where $R$ is the ...


2

Looking at the image, it appeared to be a supernova remnant, and sure enough when I plugged the coordinates into SkyMap, it identified NGC 6960, the Veil Nebula. The interaction of the hot ionized gas of the expanding supernova remnant with the interstellar medium produces radiation at many wavelengths. The Veil Nebula is almost 3 degrees across, while the ...


2

It would be very interesting if it happened, but such an event would be very rare. Black holes are relatively rare, and black hole binaries are rarer. All the black hole mergers that we have detected have been in distant galaxies. The chance of a black hole merger happening in our galaxy is quite low. Gravitational lensing occurs when a black hole (or other ...


2

I think the short answer is "You can't observe $z=0$ LyC leakers, but you can observe $z\sim0$ LyC leakers." No z = 0 leakers… Measuring the Lyman continuum (LyC) — i.e. photons capable of ionizing neutral hydrogen (HI) — is indeed very hard. The HI cross section to LyC is $$ \sigma_\mathrm{LyC} = \sigma_\mathrm{LL} \times \left( \frac{\lambda}{912\...


1

The bolometric correction is the difference between a bolometric magnitude and the magnitude in some band. $$BC = M_{\rm bol} - M_{5100} = -2.5\log\left(\frac{L_{\rm bol}}{L_{5100}}\right) $$ $$\log L_{\rm bol} = \log L_{5100} - 0.4BC \ ,$$ $$ \log L_{\rm bol} = \log L_{5100} +0.4\log L_{5100} - 21.2 \ ,$$ $$ \log L_{\rm bol} = 1.4(1.4 \log L_x -16.8) - 21....


1

Just to add an example to what has already been said by eshaya and Larz.Astro. Here is the spectrum of the Black Hole binary Cygnus X-1 in its hard and its soft state. The plot is taken from Gierlinski et al. 1999 . You see that the soft state consist of mostly thermal emission below 10 keV, while the hard state is dominated by non-thermal (comtonized) ...


1

Not only in X-ray astronomy (chemistry also and pretty much everything related to X-rays). If you have an X-ray spectrum, the region with photon energy > 5-10 Kev is called "hard" X-rays, less than that it is called "soft" X-rays. Wiki has a nice explanation for that (Energy Ranges): https://en.wikipedia.org/wiki/X-ray However, I find ...


1

Active galaxies are known to change state as seen by a change in slope of their X-ray and gamma-ray spectra. We say that a spectrum has become harder (or changed to its hard state) when the slope changes so that there are relatively more high energy photons, and it becomes softer when the ratio of low energy photons to high energy photons increases. The ...


1

The lifetime of an X-ray binary is pretty broad and it depends on the type of X-ray binary you are talking about. There are 3 main types of X-ray binaries: Low Mass X-ray Binaries Intermediate Mass X-ray Binaries High Mass X-ray Binaries The accretion process is drastically different for each of these types, which means that there is no broad lifetime of ...


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