6 research outputs found
Evolution of the afterglow optical spectral shape of GRB 201015A in the first hour: evidence for dust destruction
Instruments such as the ROTSE, TORTORA, Pi of the Sky, MASTER-net, and others
have recorded single-band optical flux measurements starting as early as
10 seconds after a gamma-ray burst trigger. The earliest
measurements of optical spectral shape have been made only much later,
typically on hour time scales, never starting less than a minute after trigger,
until now. Beginning only 58 seconds after the Swift BAT triggerred on
GRB201015A, we observed a sharp rise in flux to a peak, followed by an
approximate power law decay light curve, . Flux was
measured simultaneously in three optical filter bands, g', r', and i', using
our unique instrument mounted on the Nazarbayev University Transient Telescope
at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO). Our simultaneous
multi-band observations of the early afterglow show strong colour evolution
from red to blue, with a change in the optical log slope (after correction for
Milky Way extinction) of ; during this time the X-ray log slope
remained constant. We did not find evidence for a two-component jet structure
or a transition from reverse to forward shock that would explain this change in
slope. We find that the majority of the optical spectral slope evolution is
consistent with a monotonic decay of extinction, evidence of dust destruction.
If we assume that the optical log slope is constant throughout this period,
with the value given by the late-time slope, and we further assume an SMC-like
extinction curve, we derive a change in the local extinction
from 0.8 mag to 0.3 mag in
2500 s. This work shows that significant information about the early
emission phase (and possibly prompt emission, if observed early enough) is
being missed without such early observations with simultaneous multi-band
instruments.Comment: 7 pages, 3 figures. Submitted to MNRA
Evolution of the afterglow optical spectral shape of GRB 201015A in the first hour: evidence for dust destruction
Instruments such as the ROTSE, TORTORA, Pi of the Sky, MASTER-net, and others have recorded single-band optical flux measurements starting as early as 10 seconds after a gamma-ray burst trigger. The earliest measurements of optical spectral shape have been made only much later, typically on hour time scales, never starting less than a minute after trigger, until now. Beginning only 58 seconds after the Swift BAT triggerred on GRB201015A, we observed a sharp rise in flux to a peak, followed by an approximate power law decay light curve, . Flux was measured simultaneously in three optical filter bands, g', r', and i', using our unique instrument mounted on the Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO). Our simultaneous multi-band observations of the early afterglow show strong colour evolution from red to blue, with a change in the optical log slope (after correction for Milky Way extinction) of ; during this time the X-ray log slope remained constant. We did not find evidence for a two-component jet structure or a transition from reverse to forward shock that would explain this change in slope. We find that the majority of the optical spectral slope evolution is consistent with a monotonic decay of extinction, evidence of dust destruction. If we assume that the optical log slope is constant throughout this period, with the value given by the late-time slope, and we further assume an SMC-like extinction curve, we derive a change in the local extinction from 0.8 mag to 0.3 mag in 2500 s. This work shows that significant information about the early emission phase (and possibly prompt emission, if observed early enough) is being missed without such early observations with simultaneous multi-band instruments
On-sky silicon photomultiplier detector performance measurements for millisecond to sub-microsecond optical source variability studies
International audienc
Evolution of the afterglow optical spectral shape of GRB 201015A in the first hour: evidence for dust destruction
Instruments such as the ROTSE, TORTORA, Pi of the Sky, MASTER-net, and others have recorded single-band optical flux measurements starting as early as 10 seconds after a gamma-ray burst trigger. The earliest measurements of optical spectral shape have been made only much later, typically on hour time scales, never starting less than a minute after trigger, until now. Beginning only 58 seconds after the Swift BAT triggerred on GRB201015A, we observed a sharp rise in flux to a peak, followed by an approximate power law decay light curve, . Flux was measured simultaneously in three optical filter bands, g', r', and i', using our unique instrument mounted on the Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO). Our simultaneous multi-band observations of the early afterglow show strong colour evolution from red to blue, with a change in the optical log slope (after correction for Milky Way extinction) of ; during this time the X-ray log slope remained constant. We did not find evidence for a two-component jet structure or a transition from reverse to forward shock that would explain this change in slope. We find that the majority of the optical spectral slope evolution is consistent with a monotonic decay of extinction, evidence of dust destruction. If we assume that the optical log slope is constant throughout this period, with the value given by the late-time slope, and we further assume an SMC-like extinction curve, we derive a change in the local extinction from 0.8 mag to 0.3 mag in 2500 s. This work shows that significant information about the early emission phase (and possibly prompt emission, if observed early enough) is being missed without such early observations with simultaneous multi-band instruments
Evolution of the afterglow optical spectral shape of GRB 201015A in the first hour: evidence for dust destruction
Instruments such as the ROTSE, TORTORA, Pi of the Sky, MASTER-net, and others have recorded single-band optical flux measurements starting as early as 10 seconds after a gamma-ray burst trigger. The earliest measurements of optical spectral shape have been made only much later, typically on hour time scales, never starting less than a minute after trigger, until now. Beginning only 58 seconds after the Swift BAT triggerred on GRB201015A, we observed a sharp rise in flux to a peak, followed by an approximate power law decay light curve, . Flux was measured simultaneously in three optical filter bands, g', r', and i', using our unique instrument mounted on the Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO). Our simultaneous multi-band observations of the early afterglow show strong colour evolution from red to blue, with a change in the optical log slope (after correction for Milky Way extinction) of ; during this time the X-ray log slope remained constant. We did not find evidence for a two-component jet structure or a transition from reverse to forward shock that would explain this change in slope. We find that the majority of the optical spectral slope evolution is consistent with a monotonic decay of extinction, evidence of dust destruction. If we assume that the optical log slope is constant throughout this period, with the value given by the late-time slope, and we further assume an SMC-like extinction curve, we derive a change in the local extinction from 0.8 mag to 0.3 mag in 2500 s. This work shows that significant information about the early emission phase (and possibly prompt emission, if observed early enough) is being missed without such early observations with simultaneous multi-band instruments
Initial On-Sky Performance Testing of the Single-Photon Imager for Nanosecond Astrophysics (SPINA) System
International audienceThis work presents an initial on-sky performance measurement of the Single-Photon Imager for Nanosecond Astrophysics (SPINA) system, part of our Ultra-Fast Astronomy (UFA) program. We developed the SPINA system based on the position-sensitive silicon photomultiplier (PS-SiPM) detector to record both temporal and spatial information of detected photons. The initial on-sky testing of the SPINA system was conducted on UT 10 July, 2022, with the Nazarbayev University Transient Telescope at the Assy-Turgen Astrophysical Observatory (NUTTelA-TAO), studied stars with a wide range of brightness and a dark region of the sky without stars { < }18 mag. This on-sky testing yielded crucial calibration metrics for the SPINA system, demonstrating the SPINA system’s ability in rapid astronomical detections. Key findings include a spatial resolution of { < }232 ~\mu \text {m} , affected by atmospheric conditions; a background noise level of 1914 counts per second (cps) within this resolution element; and crosstalk probability of near the detector’s center while reaching at the edges. We derived a sensitivity of 17.45 Gaia BP magnitude in a 1-s exposure with no atmospheric extinction. Based on a false alarm rate of once per 100 nights, the SPINA system provides a transient sensitivity of 14.06 mag on a 10-ms window and a 15 photoelectron (P.E.) detection threshold for sub- time scale, limited by crosstalk. In addition, the SPINA system proved its capability to detect rapid alterations in the stellar profile: a variation of in the stellar profile full-width half-maximum (FWHM) under 20-ms exposure and change under 2-ms exposures, as well as capturing stellar light curves on the ms and scales