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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

2747 results found.

  1. Chandra observations of GW170817 260 days since merger: first statistically significant evidence for an X-ray decay
  2. GRB 180418A GROND observations
  3. Chandra observations of GRB161219B 400 days after the explosion
  4. Swift Trigger 819301: possible GRB 180329A
  5. GRB 180324A: RATIR Optical Observations and Possible Afterglow Detection
  6. GRB 180316A: RATIR Optical Observations, Possible Re-brightening
  7. GRB 180224A: AbAO optical observations
  8. Swift trigger 811074 (possible GRB 180221A): Swift refined analysis
  9. GRB180221A: MASTER-OAFA optical observations
  10. Swift Trigger 811074: possible GRB 180221A
  11. Trigger 809374: Swift detection of a possible non-burst faint source
  12. Fermi-GBM Detection of possible burst from AXP CXOU J164710.2-455216/PSR J1647-4552
  13. LIGO/Virgo GW170817: Chandra X-ray Emission Continues to Rise ~156 Days Post-Merger
  14. GRB 180120A CALET Gamma-Ray Burst Monitor detection
  15. GRB180111A: Xinglong TNT possible optical detection
  16. GRB 180103A: LCO Sutherland 1-m telescope observations
  17. GRB 171209A: Swift/UVOT Analysis of the burst
  18. GRB 171209A: Swift detection of a burst
  19. LIGO/Virgo G298048: Brightening X-ray Emission from GW170817/GRB170817A/SSS17a
  20. LIGO/Virgo GW170817: Chandra X-ray brightening of the counterpart 108 days since merger
  21. GRB 171205A: Host galaxy photometric properties
  22. Possible blackbody component in the X-ray spectrum of GRB171205A
  23. Pan-STARRS follow-up of IceCube-171106A
  24. GRB 171123A: Swift detection of a burst
  25. GRB 171010A: possible SN component
  26. IceCube-171106A - IceCube observation of a high-energy neutrino candidate
  27. GRB 171030A: MASTER inspection of the IPN error box of the short GRB.
  28. GRB 171103A: Fermi GBM observation
  29. GRB 171010A: VLT spectroscopic identification of the associated SN 2017htp
  30. GRB 171030A: IPN error box through NSs probability merging rate map
  31. Swift trigger 781740: Further analysis from Swift and Fermi/GBM
  32. Fermi-GBM Detection of possible burst from AXP CXOU J164710.2-455216/PSR J1647-4552
  33. Swift trigger 779171 is probably a noise fluctuation
  34. IceCube-171015A - IceCube observation of a high-energy neutrino candidate event
  35. BAT trigger 778435 is not a GRB.
  36. GRB 171013A: Swift detection of a possible burst
  37. GRB 171010A: Swift/UVOT Detection
  38. GRB 171010A: ePESSTO NTT spectroscopic redshift
  39. GRB 171010A: OT, spectrum, and possible host galaxy
  40. LIGO/Virgo G298048: Mid-Infrared Spitzer/IRAC Observations at 3.6 and 4.5 microns
  41. Swift Trigger 775946 is a Galactic transient, not GRB 171003
  42. GRB 171003A: LT early optical observations
  43. GRB 170906C: 15 GHz upper limits from AMI
  44. LIGO/Virgo G298048: Summary of Pi of the Sky observations
  45. IceCube-170922A - IceCube observation of a high-energy neutrino candidate event
  46. LIGO/Virgo G298048: SRT observations of SSS17a in NGC 4993
  47. LIGO/Virgo G299232: Lulin Observations of Possible OTs
  48. LIGO/VIRGO G298048: Radio detection of SSS17a at 6 GHz with the VLA
  49. GRB 170902A: Swift detection of a burst or possible Galactic transient
  50. LIGO/Virgo G298048
  51. LIGO/Virgo G298048: Possible Plateau in Ks band revealed by continued Gemini-South observations
  52. LIGO/Virgo G299232: HAWC follow-up
  53. LIGO/Virgo G298048: Zadko Telescope 7 day observations of the OT candidate SSS17a/DLT17ck
  54. GRB 170827A: Swift-XRT refined Analysis
  55. LIGO/Virgo G299232: OVRO-LWA simultaneous low frequency radio observations of localization region
  56. LIGO/Virgo G299232/PGWB170825.55: MASTER Global-Net OT inside NGC1343 discovery
  57. LIGO/Virgo G299232 : Fermi-LAT search for high-energy gamma-ray counterpart
  58. LIGO/Virgo G298389: HAWC follow-up
  59. LIGO/Virgo G299232: AGILE MCAL detection of a short gamma-ray candidate
  60. LIGO/Virgo G297595: INTEGRAL pointed follow-up observations
  61. LIGO/Virgo G298048: MASTER Global-Net early optical observations and the Possible KiloNova SSS17a in NGC 4993 photometry and merging rate
  62. LIGO/Virgo G298048: HAWC follow-up
  63. LIGO/Virgo G298048: H.E.S.S. very-high energy gamma-ray follow-up
  64. LIGO/Virgo G298048: INTEGRAL pointed follow-up observations
  65. LIGO/Virgo G298936 : Fermi-LAT search for a high-energy gamma-ray counterpart
  66. LIGO/Virgo G298048: Continued VLA monitoring at 6 GHz
  67. LIGO/Virgo G298936: Identification of a GW Binary Black Hole Candidate
  68. LIGO/Virgo G298048: Global properties and star-formation rate of NGC 4993
  69. LIGO/Virgo G298048: observations of optical counterpart candidate with CHILESCOPE observatory
  70. LIGO/Virgo G298048: ASKAP observations of SSS17a and NGC 4993 at 1.345 GHz
  71. LIGO/Virgo G298048: Gemini-South Near-Infrared Spectroscopy
  72. LIGO/Virgo G298048: VLA observation at 15 GHz
  73. LIGO/Virgo G298048: observations of optical counterpart candidate with CHILESCOPE observatory
  74. LIGO/Virgo G298048: Zadko observations of the OT candidate SSS17a/DLT17ck
  75. LIGO/Virgo G298048: NuSTAR limits on X-ray emission
  76. LIGO/Virgo G298048: ASKAP follow up
  77. LIGO/Virgo G298048: Kanata/HONIR NIR photometry of the possible counterpart of G298048
  78. LIGO/Virgo G298389 : Fermi-LAT search for a high-energy gamma-ray counterpart
  79. LIGO/Virgo G298048: VLA observation at 6 GHz
  80. LIGO/Virgo G298048: Continued VLA observations
  81. LIGO/Virgo G298048: Possible X-ray detection with Swift
  82. LIGO/Virgo G298048: VLBA observations of the possible counterpart SSS17a in NGC 4993
  83. LIGO/Virgo G298048: Possible features in the spectrum of GW counterpart SSS17a
  84. LIGO/Virgo G298048: Rapid Evolution of Possible Counterpart
  85. LIGO/Virgo G298048: Observed fading of optical counterpart SSS17a
  86. LIGO/Virgo G298048: Continued observation for DLT17ck
  87. LIGO/Virgo G298048: Brightening of Possible Counterpart
  88. LIGO/Virgo G298048: Subaru HSC z-band photometry of the possible optical counterpart
  89. LIGO/Virgo G298048: Likelihood of SSS17a Being an Unrelated Extragalactic Transient in NGC 4993
  90. LIGO/Virgo G298048: REM optical/NIR observations
  91. LIGO/Virgo G298048: Pan-STARRS detections and izy photometry of the possible optical/NIR counterpart in NGC4993
  92. LIGO/Virgo G298048: Galaxy-Targeted Optical Followup With Las Cumbres Observatory
  93. LIGO/VIRGO G298048: The Potential Optical Counterpart in NGC 4993 Has Afterglow-Like Colors
  94. LIGO/Virgo G298048: Las Cumbres Observatory Detection of The Possible Optical Counterpart in NGC 4993
  95. LIGO/Virgo G298048: Inspection of archival HST data at the position of the potential optical counterpart
  96. LIGO/Virgo G298048 : Fermi-LAT search for a high-energy gamma-ray counterpart
  97. LIGO/Virgo G298048: correction to the luminosity distance reported in GCN 21509
  98. LIGO/Virgo G298048: Identification of a binary neutron star candidate coincident with Fermi GBM trigger 524666471/170817529
  99. LIGO/Virgo G298048: Fermi GBM trigger 524666471/170817529: LIGO/Virgo Identification of a possible gravitational-wave counterpart
  100. LIGO/Virgo G297595: REM optical/NIR observations

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