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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"

26354 results found.

  1. GRB 250706B: SVOM detection of a long burst
  2. GRB 250706A: Swift detection of a burst
  3. GRB 250704B: Swift-XRT refined Analysis
  4. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  5. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  6. GRB 250703A: EIRSAT-1 GMOD Detection
  7. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  8. GRB 250704B: Swift/UVOT Upper Limits
  9. GRB 250704A: Swift/UVOT Detection
  10. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  11. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  12. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  13. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  14. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  15. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  16. GRB 250702F: Kilonova-Catcher optical afterglow detection
  17. GRB 250702F: Monte Agliale Observatory optical observations
  18. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  19. EP250704a / GRB 250704B: JinShan optical observations
  20. EP250704a / GRB 250704B: SAO RAS optical observations
  21. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  22. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  23. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  24. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  25. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  26. EP250704a / GRB250704B: Swift-XRT counterpart detection
  27. GRB 250704A: Swift-XRT afterglow detection
  28. EP250704a / GRB 250704B - REM observations
  29. GRB 250702F: GROWTH-India Telescope optical observations
  30. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  31. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  32. EP250702a: WFST optical observations
  33. EP250704a: COLIBRÍ optical counterpart candidate
  34. EP250704a: Einstein Probe detection of an X-ray transient
  35. GRB 250704A: REM detection of the optical afterglow
  36. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  37. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  38. GRB 250704A: SVOM detection of a burst
  39. GRB 250702F: Swift/UVOT Detection
  40. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  41. GRB 250702F: Swift-XRT refined Analysis
  42. GRB 250702F: Fermi GBM Observation
  43. GRB 250702F: Leavitt Observatory optical observations
  44. GRB 250702F: AKO Optical Afterglow Detection
  45. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  46. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  47. GRB 250702F: Skynet Optical Observations
  48. GRB 250424A: VIRT Optical Upper Limit
  49. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  50. GRB 250702F: TRT Optical Observation
  51. GRB 250703A: DDOTI Optical Upper Limit
  52. GRB 250702F: REM optical afterglow detection
  53. EP250702a: Global MASTER-Net observations report
  54. GRB 250702F: DDOTI Optical Observation
  55. GRB 250702F: COLIBRÍ Observations of the Afterglow
  56. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  57. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  58. GRB 250702F: Enhanced Swift-XRT position
  59. GRB 250702F: NOT observations of the optical afterglow
  60. GRB 250702F: Swift detection of a burst with an optical counterpart
  61. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  62. GRB 250702A: Fermi GBM Detection
  63. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  64. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  65. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  66. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  67. GRB 250628B: Swift-XRT observations
  68. GRB 250628B: EP-FXT counterpart detection
  69. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  70. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  71. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  74. GRB 250628A: REM optical/NIR upper limits
  75. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  76. GRB 250628B: SVOM detection of a long burst
  77. GRB 250628A: VLT/X-shooter upper limits
  78. GRB 250628A: Swift/UVOT Upper Limits
  79. GRB 250628A: Swift-XRT refined Analysis
  80. GRB 250628A: Enhanced Swift-XRT position
  81. GRB 250628A: Swift detection of a burst
  82. GRB 250625A: Swift-BAT refined analysis
  83. GRB 250625A: Leavitt Observatory afterglow detection
  84. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  85. GRB 250625A: SVOM/C-GFT upper limit in early phase
  86. GRB 250625A: Swift/UVOT Upper Limits
  87. GRB 250625A: ABObservatory afterglow detection
  88. GRB 250625A: OHP/T193 optical detection
  89. GRB 250625A: COLIBRÍ optical observations
  90. GRB 250625A: Swift-XRT refined Analysis
  91. GRB 250625A: JinShan optical observations
  92. GRB250625A: Fermi GBM Observation
  93. GRB 250620B: Fermi GBM Observation
  94. GRB 250625A: SAO RAS possible optical afterglow
  95. GRB 250625A: Enhanced Swift-XRT position
  96. GRB 250625A: Swift detection of a burst
  97. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  98. GRB 241018A: Maidanak optical observations
  99. GRB 250620C: AstroSat CZTI detection
  100. Fermi GRB 250624A: Global MASTER-Net observations report

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