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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"

26482 results found.

  1. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  2. GRB 250702F: radio detection with the VLA
  3. IceCube-250706A: EP-FXT follow-up observations
  4. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  5. GRB 250706B/C: Fermi-LAT detection
  6. IceCube-250706A: Global MASTER-Net observations report
  7. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  8. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  9. GRB 250706B: Swift/UVOT Detection
  10. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  11. GRB 250702F: GRANDMA observations
  12. GRB 250706A: Swift-XRT refined Analysis
  13. GRB 250706B: refined SVOM/MXT data analysis
  14. GRB 250706A: Swift/UVOT Upper Limits
  15. GRB 250706B: REM optical observations
  16. GRB 250706A: REM optical/NIR observations
  17. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  18. IceCube-250416A: DDOTI Optical Upper Limit
  19. IceCube-250706A: COLIBRÍ optical upper limits
  20. GRB 250706A: JinShan optical upper limits
  21. GRB 250706A: SAO RAS optical observations
  22. EP250704A: NOWT Detection
  23. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  24. GRB250706B: Swift-XRT counterpart detection
  25. GRB 250706B: iTelescope optical observations
  26. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  27. GRB 250706B: SVOM/VT optical observation
  28. GRB 250706B: TRT bright optical counterpart detection
  29. GRB 250706A: GROWTH-India Telescope optical upper limit
  30. GRB 250706B: SVOM detection of a long burst
  31. GRB 250706A: Swift detection of a burst
  32. GRB 250704B: Swift-XRT refined Analysis
  33. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  34. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  35. GRB 250703A: EIRSAT-1 GMOD Detection
  36. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  37. GRB 250704B: Swift/UVOT Upper Limits
  38. GRB 250704A: Swift/UVOT Detection
  39. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  40. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  41. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  42. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  43. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  44. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  45. GRB 250702F: Kilonova-Catcher optical afterglow detection
  46. GRB 250702F: Monte Agliale Observatory optical observations
  47. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  48. EP250704a / GRB 250704B: JinShan optical observations
  49. EP250704a / GRB 250704B: SAO RAS optical observations
  50. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  51. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  52. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  53. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  54. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  55. EP250704a / GRB250704B: Swift-XRT counterpart detection
  56. GRB 250704A: Swift-XRT afterglow detection
  57. EP250704a / GRB 250704B - REM observations
  58. GRB 250702F: GROWTH-India Telescope optical observations
  59. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  60. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  61. EP250702a: WFST optical observations
  62. EP250704a: COLIBRÍ optical counterpart candidate
  63. EP250704a: Einstein Probe detection of an X-ray transient
  64. GRB 250704A: REM detection of the optical afterglow
  65. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  66. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  67. GRB 250704A: SVOM detection of a burst
  68. GRB 250702F: Swift/UVOT Detection
  69. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  70. GRB 250702F: Swift-XRT refined Analysis
  71. GRB 250702F: Fermi GBM Observation
  72. GRB 250702F: Leavitt Observatory optical observations
  73. GRB 250702F: AKO Optical Afterglow Detection
  74. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  75. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  76. GRB 250702F: Skynet Optical Observations
  77. GRB 250424A: VIRT Optical Upper Limit
  78. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  79. GRB 250702F: TRT Optical Observation
  80. GRB 250703A: DDOTI Optical Upper Limit
  81. GRB 250702F: REM optical afterglow detection
  82. EP250702a: Global MASTER-Net observations report
  83. GRB 250702F: DDOTI Optical Observation
  84. GRB 250702F: COLIBRÍ Observations of the Afterglow
  85. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  86. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  87. GRB 250702F: Enhanced Swift-XRT position
  88. GRB 250702F: NOT observations of the optical afterglow
  89. GRB 250702F: Swift detection of a burst with an optical counterpart
  90. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  91. GRB 250702A: Fermi GBM Detection
  92. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  93. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  94. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  96. GRB 250628B: Swift-XRT observations
  97. GRB 250628B: EP-FXT counterpart detection
  98. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  99. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  100. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate

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