GRB Probes of the High-z Universe with EXIST (original) (raw)
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The High Energy Telescope on EXIST: Hunting High Redshift GRBs and other Exotic Transients
Proceedings of The Extreme sky: Sampling the Universe above 10 keV — PoS(extremesky2009)
The High Energy Telescope (HET) on EXIST is designed to locate high redshift Gamma-Ray Bursts (GRBs) and other rare transients fast (<10 sec) and accurately (< 20″) in order to allow rapid (<1-2 min) follow-up observations with onboard X-ray/optical/IR imaging and spectroscopy. The HET employs coded-aperture imaging with a 4.5 m 2 imaging CZT detector array and hybrid tungsten mask. The wide energy band coverage (5-600 keV) is optimal for capturing these transients and highly obscured AGN. The continuous scan with the wide field of view (90º × 70º at 10% coding fraction) increases the chance of capturing rare elusive events such as soft Gamma-ray repeaters and tidal disruption events of stars by dormant supermassive black holes. Sweeping nearly the entire sky every two orbits (3 hour), EXIST will also establish a finely-sampled long-term history of the X-ray variability of many X-ray sources, opening up a new time domain for variability studies. In light of the new EXIST design concept, we review the observing strategy to maximize the science return and report on our recent balloon flight test of a prototype for the CZT detectors needed for HET.
The Energetic X-ray Imaging Survey Telescope (EXIST)
Bulletin of the American Astronomical Society, 2009
The Energetic X-ray Imaging Survey Telescope (EXIST) is a proposed hard X-ray imaging all-sky deep survey mission recommended by the Report of the 2001 Decadal Survey. It is a strong candidate to be the Black Hole Finder Probe, one of the three "Einstein Probes" in the Beyond Einstein Program. In its new more evolved form, the EXIST mission now includes a simplified, but more sensitive, very large area and field of view imaging hard X-ray telescope as well as a 1.1m optical-NIR telescope (0.3-2.5microns) for rapid ( 100sec) followup imaging and spectra and thus prompt redshifts of high-z GRBs. The IRT will also permit identification and galaxy spectra for a significant fraction of the obscured AGNs detected in the EXIST full sky survey. The primary science objectives for EXIST are to: 1) study the earliest stars, re-ionization, and development of structure in the universe with prompt hard X-ray and prompt followup NIR measurements of GRBs at z >7, 2) constrain the accretion luminosity of the universe by measurements of high luminosity obscured AGN at z 0-2.5, low luminosity AGN at z <0.5 and dormant AGN (from tidal disruption events) at z <0.1, and 3) provide the most sensitive and wide-field measures of the transient universe with X-ray/OIR studies of Blazars, black hole transients and high energy variables with full-sky coverage every 3h, in synergy with GLAST and PanSTARRS, as well as LSST, JWST and other planned facilities. With >10X the area of Swift/BAT and much broader energy band, as well deep NIR coverage with a passively cooled mirror, EXIST greatly surpasses any previous or proposed mission for wide-field imaging and spectroscopy of GRBs and black holes on all scales.
The high energy telescope on EXIST
UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XVI, 2009
The Energetic X-ray Imaging Survey Telescope (EXIST) is a proposed next generation multi-wavelength survey mission. The primary instrument is a High Energy telescope (HET) that conducts the deepest survey for Gamma-ray Bursts (GRBs), obscured-accreting and dormant Supermassive Black Holes and Transients of all varieties for immediate followup studies by the two secondary instruments: a Soft X-ray Imager (SXI) and an Optical/Infrared Telescope (IRT). EXIST will explore the early Universe using high redshift GRBs as cosmic probes and survey black holes on all scales. The HET is a coded aperture telescope employing a large array of imaging CZT detectors (4.5 m 2 , 0.6 mm pixel) and a hybrid Tungsten mask. We review the current HET concept which follows an intensive design revision by the HET imaging working group and the recent engineering studies in the Instrument and Mission Design Lab at the Goddard Space Flight Center. The HET will locate GRBs and transients quickly (<10-30 sec) and accurately (< 20") for rapid (< 1-3 min) onboard followup soft X-ray and optical/IR (0.3-2.2 m) imaging and spectroscopy. The broad energy band (5-600 keV) and the wide field of view (~90º × 70º at 10% coding fraction) are optimal for capturing GRBs, obscured AGNs and rare transients. The continuous scan of the entire sky every 3 hours will establish a finely-sampled long-term history of many X-ray sources, opening up new possibilities for variability studies.
GRBs as Probes of the Early Universe with TSO
2019
Long gamma-ray bursts (GRBs) are the most luminous known electromagnetic radiation sources in the Universe for the 3 to 300 sec of their prompt flashes (isotropic X/ gamma-ray luminosities up to 10^53 ergs/sec). Their afterglows have first day rest-frame UV/optical absolute magnitudes AB = -30 to -23. This luminous continuum nUV-nIR back-light provides the ultimate probe of the SFR(z) back to the first Pop III to II.5 stars, expected to be massive and GRB progenitors. GRB afterglow spectra in the first 1 to 3 hours will directly measure their host galaxy ionization fraction x_i vs. z in the Epoch of Reionization (EOR), tracing the growth of structure. Only 28% of Swift GRBs have measured redshifts due to limited followup at R, J >21. Some ~25% of GRBs are optically dark due to dust absorption in their host galaxies, but those with low NH in their X-ray spectra are likely at z >7. Current 8-10m telescopes and coming ELTs cannot pursue optically dark GRBs promptly, nor can JWST ...
IKI GRB-FuN: observations of GRBs with small-aperture telescopes
2021
Gamma-ray bursts (GRBs) are the most energetic and mysterious events in the Universe, which are observed in all ranges of electromagnetic spectrum. Most valuable results about physics of GRB are obtained by optical observations. GRBs are initially detected in gamma-rays with poor localization accuracy, and an optical counterpart should be found. The faster the counterpart is found, the more it can give to physics. This first phase, as a rule, corresponds to an early afterglow. The next phases of the observations are multicolor photometry, polarimetry, spectroscopy, and few days later the search for a supernova or kilonova associated with the GRB, and finally, observations of the host galaxy. To manage the problem of fast optical observations, telescopes with a small aperture are suitable. They can have a large field of view, which is necessary to cover initial localizations of GRBs. The sensitivity of the telescope+detector may be sufficient to record statistically significant light...
Astrosat CZT Imager Observations of GRB 151006A: Timing, Spectroscopy, and Polarization Study
The Astrophysical Journal, 2016
AstroSat is a multi-wavelength satellite launched on 2015 September 28. The CZT Imager of AstroSat on its very first day of operation detected a long duration gamma-ray burst (GRB), namely GRB 151006A. Using the off-axis imaging and spectral response of the instrument, we demonstrate that theCZT Imager can localize this GRB correctly to about a few degrees, and it can provide, in conjunction with Swift, spectral parameters similar to thoseobtained from Fermi/GBM. Hence, the CZT Imager would be a useful addition to the currently operating GRB instruments (Swift and Fermi). Specifically, we argue that the CZT Imager will be most useful for the short hard GRBs by providing localization for those detected by Fermi and spectral information for those detected only by Swift. We also provide preliminary results on a new exciting capability of this instrument: theCZT Imager is able to identify Compton scattered events thereby providing polarization information for bright GRBs. GRB151006A, in spite of being relatively faint, shows hints of a polarization signal at 100-300 keV (though at a low significance level). We point out that theCZT Imager should provide significant time resolved polarization measurements for GRBs that have fluence threetimes higher than that of GRB151006A. We estimate that the number of such bright GRBs detectable by theCZT Imager is five to six per year. TheCZT Imager can also act as a good hard X-ray monitoring device for possible electromagnetic counterparts of gravitational wave events.
Optimizing the Search for High-z GRBs: The JANUS X-ray Coded Aperture Telescope
We discuss the optimization of gamma-ray burst (GRB) detectors with a goal of maximizing the detected number of bright high-redshift GRBs, in the context of design studies conducted for the X-ray transient detector on the JANUS mission. We conclude that the optimal energy band for detection of high-z GRBs is below about 30 keV. We considered both lobster-eye and coded aperture designs operating in this energy band. Within the available mass and power constraints, we found that the coded aperture mask was preferred for the detection of high-z bursts with bright enough afterglows to probe galaxies in the era of the Cosmic Dawn. This initial conclusion was confirmed through detailed mission simulations that found that the selected design (an X-ray Coded Aperture Telescope) would detect four times as many bright, high-z GRBs as the lobster-eye design we considered. The JANUS XCAT instrument will detect 48 GRBs with z > 5 and fluence S x > 3 × 10 −7 erg cm −2 in a two year mission.
The Astrophysical Journal, 2002
We present Very Large Telescope spectroscopic observations of the GRB 990705 host galaxy and highlight the benefits provided by the prompt phase features of gamma-ray bursts (GRBs) to derive the redshifts of the latter. In the host spectrum, we indeed detect an emission feature that we attribute to the [O ii] ll3726, 3729 doublet and derive an unambiguous redshift for this galaxy. This is in full agreement with z p 0.8424 ע 0.0002 the value previously derived using a transient absorption edge discovered in the X-ray spectrum z ∼ 0.86 ע 0.17 of GRB 990705. This burst is therefore the first GRB for which a reliable redshift was derived from the prompt phase emission itself, as opposed to redshift determinations performed using putative host galaxy emission lines or interstellar absorption lines in the GRB afterglows. Deep and high-resolution images of the host of GRB 990705 with the Space Telescope Imaging Spectrograph camera on board the Hubble Space Telescope reveal that the burst occurred in a nearly face-on Sc spiral galaxy typical of disk-dominated systems at . 0.75 ≤ z ≤ 1 Assuming a cosmology with km s Ϫ1 Mpc Ϫ1 , , and , we derive an absolute B magnitude H p 65 Q p 0.3 Q p 0.7 0 m l for this galaxy and a star formation rate yr Ϫ1 . Finally, we discuss the implications M p Ϫ21.75 SFR ≈ 5-8 M B ,