Observational Astronomy - Science topic

If you already know the RVs you could try this:

Watch out the RV's sign you input.

Cool project! Reproducing the first detection of the 21 cm line by Ewen and Purcell in 1951.

But why re-invent the wheel, in software terms? CASA (https://casa.nrao.edu/ ) is the "industry standard" software for radio astronomy data analysis. Works on Linux and Mac OSX, with an iPython interface. And it's free.

Your horn antenna data could be analysed in CASA in the same way as "single dish" data - the only real difference is that a horn has poorer angular resolution (larger beamwidth) than a parabolic dish of the same collecting aperture.

Thank you very much for your answer P. G. Wannier sir. Your suggestions are very helpful.

Sir Franz-Josef Hambsch, I don't have the experimental facility. My work is limited to predicting reaction pathways for the detected (or possible detection) using computational quantum chemistry.  whatever spectroscopy  I need is to understand the papers on the observations of new molecules and the other experimantal works performed on the same systems.

First a small correction: in the middle column the "value" is not in Pi but in radians/2 (as the plot shows).

Now if you have here those two time series (or signals), TSI and SST, each of them with some spectral content (frequencies) revealed by the Fourier transform of their own auto-correlation function, the Fourier transform of the cross-correlation function gives the cross-spectrum. Its amplitude shows those frequencies that are present in both signals (the plot could have been helpful if present) and its phase (your plot) shows the delay or lag of one signal behind the other at that particular frequency. For example a phase lag of Pi (180 deg) means that the signals are in opposition (when one goes/is up the other goes/is down or a difference in time of a half of that particular period, the case of the 6.6 years period with a lag of approx 3.3 years) and a phase lag of Pi/2 (90 deg) mean that the signals are in quadrature (when one is at its extremum the other crosses zero, almost the case of the 43 years period with a lag of approx. 12 years).

As of which units are used, radians are closer to scientific notation, degrees are closer to common sense but years (as fraction of period) seems to me more relevant.

Kartick:  The question title should be "What is the possible origin of high energy Cosmic Neutrinos?"  because the attached article bears exclusively high energy neutrinos (>>MeV), so excluding the most numerous ones, the cosmic backgroung neutrinos that you mentioned made ~1 sec after the big bang by the electron-positron anihilations.

Yes, in principle, it's possible, and the many near central line observations of past eclipses might also be used. Since LRO is in a polar orbit, the LRO lunar limb data are still better at the poles, but the mission has gone on long enough to cover the equatorial regions quite well, also. Kaguya was not in orbit long enough to do that. Anyway, it will be interesting to compare results at the 2017 Aug. eclipse, from both near the limits and from near the center.

The discrepancy is not understood and is being investigated. Most likely, it is caused by a local parallax offset of (bright?) Pleiades stars in the Hipparcos Catalogue.

More precisely, I offered it as just one possible observational reason that might explain the pattern. My comments were:

I have no skin in this game of cosmology, but was drawn to present an observer's viewpoint. If anyone with intimate knowledge of SDSS can really answer this, that would be interesting.

 Dear Thierry De Mees,

I have downloaded your book "Gravitomagnetism/Coriolis Gravity Theory" and will spend my winter break reading through it. As I recall, in the past, Voyager images lead researchers towards the Coriolis effect as an explanation for the Great Red Spot on Jupiter. Thank you.

Sincerely, 

Terry R. Fisher

Since the 1990s, the vast majority of amateur telescopes have been made in China or Taiwan, and sold under various brand names in different territories. (Japan held that role up to the 1980s).

The big Chinese manufacturers include Synta, and Kunming's United Optics - the latter are a bit higher in quality in my experience. Taiwanese manufacturers include GSO (Guan Sheng Optical) and William Optics - both are very good in quality.

In North America, these products end up under the Orion, Celestron, Meade, Astro Tech, Explore Scientific, iOptron, and other brand names. In Europe, and sometimes Canada, they are also sold as Skywatcher, Bresser, TS (Teleskop Service), Altair, and more.

If you are starting off in amateur sky watching, there are very good telescopes to be found in all those lines.

With more money comes more choice, and that final extra 5-10% of optical and mechanical quality. Higher end products come from more diverse sources, and are usually actually made by the business which brands them. Examples include the catadioptric telescopes from Meade and Celestron (USA), the Maksutov telescopes from Intes and Intes Micro (Russia), and apochromatic refractors from many manufacturers such as Takahashi, Vixen and Borg (Japan); TeleVue, TEC and Astro-Physics (USA); TMB and APM (Germany); and Officina Stellare (Italy).

This is a slightly dated but still good list, ranking telescopes by type and price bracket:

Victor

I proposed an inhomogeneous model where the universe is super-organized around a mega black hole like a giant galaxy. In this case dark energy is the result insufficient dark matter at this larger scale. If matter was pulled in conservation laws would accelerate the system and increase dark energy. Certainly until these aspects are better understood we must explore all avenues.

Schumann resonances are ELF electromagnetic resonances in the ground-ionosphere cavity which are excited by lightning strokes. Schumann resonances  cannot be used to detect solar activity. Various types of electromagnetic signatures of solar activity are frequently observed in the MHz frequency band and are known under the generic name of solar radio bursts.

Atiqa

For direct download of Landsat level 1 EVI product already derived for you and other products you can use ESPA Bulk order. The link is provided here: http://espa.cr.usgs.gov/ordering/new, But before downloading or odering data you have to provide the scenes you are interested in in a text file, so you can use earth explorer or glovis to identify the scenes you are interested in.

I hope this helps

Please read the paper, may be helpful for you.  A new approach to the correction of

I guess you are asking for spatial resolution?

In the mid-IR:

1) VISIR at the ESO/VLT gets to 0.045"/pixel, diffraction limited imaging atigh sensitivity in the two mid-IR atmospheric windows N & Q bands

2) MIRI aboard the JWST will give 0.11"/pixel at 7 micron

3) METIS at the E-ELT will provide Nyquist sampling at diffraction limit 3 & 8 micron

In the near-IR:

1) NACO at the VLT focus gives a resolution close to diffraction limit of the 8m telescope (0.08"/pixel). Using Adaptive optics may improve or lower these figures.

2) NIRCAM on-board the JWST will provide 0.033"/pixel in the 1-2 micron range, and 0.065"/pixel in the 2-5 micron range.

Hope that helps, but again, most of the information can be found in the weg.

All the best,

Patrice

This functionally is no different than any observing project, whether you use multiple telescopes simultaneously or sequentially. We use standards for exactly that reason. The magnitude I obtain and publish has to be reproducible by others with different instrumentation. That can be tricky, but there are plenty of standards to use (often in the same field as the target star: look at the AAVSO APASS standards).

Timing becomes important when working on combining data from different instruments taken at the same time, but that is not difficult with modern equipment. I do work using simultaneous spectroscopic and photometric observations for variable stars, albeit with targets of much longer periods.

One question. Is there a reason you are trying to get data in more than one filter while looking at asteroseismology? It looks like many studies choose to stick with just B, since these are hot stars. For example this HUGE study: http://adsabs.harvard.edu/abs/2005MNRAS.358..651K

Good luck with the project.

Most of CCDs have high sensitivity. It is important for obtaining of faint signal. CMOS sensors can be appropriate for bright objects.

There is another way to find IR spectrum of hot water  by yourself through the well-known software LBLRTM (one software for atmosphere). It is not difficult to run the software LBLRTM.

In principle, you can calculate exposure by using the on-line calculators that you can find in most of the web sites of the major telescopes. By the way, the right exposure depends from a lot of parameters such as seeing, position of the field you are interested for respect to the Moon, presence of bright objects near to your target, etc. Thus, the best is to start with the computed exposure, than repeat the observation until you have the best result. Once you obtaind a satisfactory photometry of your object, take a record of the exposure time you used, in order to avoid to waste time next time you will take photometry of the same object or of a similar one in the same sky conditions.

Thank you very much for the answers, I'll detaily check all possibilities. Best regards.

Thank you for your answer, Nainan. Best wishes

not completely sure what your asking, but the simplest way to determine the center for any aperture on a star or galaxy is to simply make small movements and "peak up" on the observed flux.

You do this first for bright sources so you can calibrate your fiber apertures and as long as the telescope doesn't flex between different positions, you should be okay.

hi reynan,

check out these references:

basically, there is a large amplitude vertical wave. when the wave brings air up, it forms clouds (the festoons). when it brings air down, it creates 5-micron hot spots, sometimes also called dark projections.

the actual shape of the festoons has not been modeled in detail, i don't think. but i would agree with you that it is related to change in wind speed (horizontal wind shear).

Try this - its old , but was pretty deep

but there are several more recent CCD based surveys as well

This question is critical for those of us who observe occultations of stars by asteroids. Before ESA's HIPPARCOS mission, special efforts were needed to obtain astrometry that was good enough to predict these events. With the subsequent catalogs that are ultimately based on HIPPARCOS results for their reference frame, our work has blossomed, but as we move farther from the 1991 mean HIPPARCOS epoch, the errors in proper motions are accumulating and limiting what we can do. The best catalogs are FK6 and HIP2, but of course they have relatively few stars. For the large number of fainter stars, we use UCAC4 (and UCAC2 before that), but also check PPMX and PPMXL for differences for individual stars, and sometimes we need to use those other catalogs. 2MASS is not accurate enough for our work.

David Dunham, International Occultation Timing Association

The asteroid scenario - or something similar - looks like an interesting ingredient to initiate the thermonuclear runaway. What I heard from the classical nova scenario is a continuing accretion of material from a companion star. This would mean essentially the outer enveloppe by Roche lobe overflow or the stellar wind, in both cases essentially gaseous material. The mass accretion rate is, if I remember correctly, relatively low (on the order of 10^-10 solar masses per year). Whatsoever, it looks like a very slow, steady accretion. Then the temperature on the bottom of the accretion layer increases also gradually and very slowly (something like 10^4 years at least between two outbursts) at ~constant density, because the bottom layer is electron-degenerate. A thermonuclear runaway is somehow at hand when one looks at the p + 12C reaction, which starts the CNO cycle on a C,O white dwarf. Just to give a number: going e.g. from 6 to 7 million Kelvin changes the reaction cross section by a factor of 40. Anyway, I would guess that at some point the ignition of the thermonuclear runaway could be helped by a kick (a blob of material in the accretion - or why not an asteroid for example?). You are right John, there must be a lot of stuff around in the system and it would inevitably be accreted from time to time on the white dwarf. But I don't think that this is included in the nova outburst simulations, next time I cross one of these nova specialists I'll ask. Thanks John, for this contribution.

Dear Webber, the sun must get rid of a huge flux of energy from the interior. When this energy is transported by convection and/or radiation, the sun is hotter inside than out. At the photosphere almost all the flux of radiation suddenly escapes as there is little material above it to stop the outflow. Most of this energy is emitted in "continua" (bound-free and free-free transitions), in the Sun these come mostly from the H- molecule (proton + 2 electrons). In certain wavelengths there is extra blockage of light from bound-bound transitions (e.g. the n=2 to n-3 levels of hydrogen). If the temperature decreases outwards on average, the light we then see comes from places higher up on average where the temperature is lower- so the light is darker. This is why "lines" appear in absorption in the photosphere.

The chromosphere is a very strange place where some 1 part in 100,000 of the energy of the sun is used to change the temperature, about 0.1 of this is then used to heat the corona. If you have a spectral line that is very opaque it will form higher up still than the photosphere- and if the temperature (more particularly the source function) is higher than the photosphere underneath it will appear in emission.

The photosphere emits almost nothing at UV and X ray wavelengths, so there is nothing there to start with that can be absorbed. It's like looking away from the Sun into space- there is almost no light "from beneath". Then you see strong emission lines and emission continua. Spectra of the Sun therefore show emission at UV and X ray wavelengths and absorption at visible and infrared wavelengths. Some lines form in both photosphere and chromosphere- for example Ca II H and K in the near UV. In these lines you see deep, wide photospheric absorption with a small chromospheric emission in the very core. These cores are related to the (variable) amount of the 1 in 100,000 part of the sun's radiation that comes from mechanical heating, such as by shock waves and magnetic field dissipation. These are active research areas. Stars show very similar behavior.

I hope this helps.

Phil

Hi Webber, there are advantages and disadvantages of observations of the corona from the ground during eclipses and from space. For ground-based observations, we usually do not have a problem with the amount of data (no restrictions imposed by the telemetry), and we can study the corona in the visible light where the signal is relatively strong. Hence, we can get movies of the corona with exceptionally high time resolution (e.g. milliseconds). It is important, e.g. for MHD coronal seismology, when we use observations of magnetohydrodynamic (MHD) waves to probe the plasma of the corona. However, eclipses are rare, their locations are scattered around the globe, and the observations are affected by the atmospheric conditions. Also, the duration of an eclipse is a few minutes only. Thus, observations during eclipses may miss interesting and important events, e.g. flares and CMEs. On the other hand, observations of the corona from space in the EUV band (e.g., with the AIA instrument on SDO) are available 24/7. But, the time resolution of AIA is 12 s - much worse than from ground. Thus, both methods of the study of the solar corona are important and compliment each other.

Dear Webber,

to solve the problem, one needs to be aware of the fact that there are two types of Cepheids.

- The "classical" ones which are young(er), brighter and confined to the Galactic disk ("Type I Cepheid").

- If the Cepheid resides in a Galactic globular cluster, it is part of the old GC/Galactic halo population and a "Type II Cepheid". These objects follow a different period-luminosity relation than the classical Cepheids.

See also:

Hope this helps,

Ylva.

Agreed, The apparent temperature is reduced by a factor (1+z), but can then be corrected by determining z from the spectral lines. So a straightforward answer is yes, the *continuous spectrum* appears cooler. However a temperature determined from line ratios or other stellar atmosphere analyses that relied on discrete line strengths would still give the "right" answer.

Thank you for the information. Can you recommend me concrete observer/spectroscopist from mentioned observatory?

What Anne suggested is an interesting thing, be sure to keep an eye out. There's another one if you're interested: you could investigate the site of rather recent GRB 130427A in Leo. There's a strong chance of a rather spectacular SN happening. And while you're waiting, there is noticeable burst afterglow in the visual spectrum, which though by no means as exciting, is also in the range of your instrument. Do take a look. ;)