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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"

26343 results found.

  1. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  2. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  3. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  4. GRB 250702F: Kilonova-Catcher optical afterglow detection
  5. GRB 250702F: Monte Agliale Observatory optical observations
  6. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  7. EP250704a / GRB 250704B: JinShan optical observations
  8. EP250704a / GRB 250704B: SAO RAS optical observations
  9. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  10. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  11. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  12. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  13. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  14. EP250704a / GRB250704B: Swift-XRT counterpart detection
  15. GRB 250704A: Swift-XRT afterglow detection
  16. EP250704a / GRB 250704B - REM observations
  17. GRB 250702F: GROWTH-India Telescope optical observations
  18. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  19. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  20. EP250702a: WFST optical observations
  21. EP250704a: COLIBRÍ optical counterpart candidate
  22. EP250704a: Einstein Probe detection of an X-ray transient
  23. GRB 250704A: REM detection of the optical afterglow
  24. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  25. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  26. GRB 250704A: SVOM detection of a burst
  27. GRB 250702F: Swift/UVOT Detection
  28. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  29. GRB 250702F: Swift-XRT refined Analysis
  30. GRB 250702F: Fermi GBM Observation
  31. GRB 250702F: Leavitt Observatory optical observations
  32. GRB 250702F: AKO Optical Afterglow Detection
  33. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  34. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  35. GRB 250702F: Skynet Optical Observations
  36. GRB 250424A: VIRT Optical Upper Limit
  37. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  38. GRB 250702F: TRT Optical Observation
  39. GRB 250703A: DDOTI Optical Upper Limit
  40. GRB 250702F: REM optical afterglow detection
  41. EP250702a: Global MASTER-Net observations report
  42. GRB 250702F: DDOTI Optical Observation
  43. GRB 250702F: COLIBRÍ Observations of the Afterglow
  44. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  45. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  46. GRB 250702F: Enhanced Swift-XRT position
  47. GRB 250702F: NOT observations of the optical afterglow
  48. GRB 250702F: Swift detection of a burst with an optical counterpart
  49. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  50. GRB 250702A: Fermi GBM Detection
  51. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  52. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  53. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  54. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  55. GRB 250628B: Swift-XRT observations
  56. GRB 250628B: EP-FXT counterpart detection
  57. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  58. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  59. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  60. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  62. GRB 250628A: REM optical/NIR upper limits
  63. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  64. GRB 250628B: SVOM detection of a long burst
  65. GRB 250628A: VLT/X-shooter upper limits
  66. GRB 250628A: Swift/UVOT Upper Limits
  67. GRB 250628A: Swift-XRT refined Analysis
  68. GRB 250628A: Enhanced Swift-XRT position
  69. GRB 250628A: Swift detection of a burst
  70. GRB 250625A: Swift-BAT refined analysis
  71. GRB 250625A: Leavitt Observatory afterglow detection
  72. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  73. GRB 250625A: SVOM/C-GFT upper limit in early phase
  74. GRB 250625A: Swift/UVOT Upper Limits
  75. GRB 250625A: ABObservatory afterglow detection
  76. GRB 250625A: OHP/T193 optical detection
  77. GRB 250625A: COLIBRÍ optical observations
  78. GRB 250625A: Swift-XRT refined Analysis
  79. GRB 250625A: JinShan optical observations
  80. GRB250625A: Fermi GBM Observation
  81. GRB 250620B: Fermi GBM Observation
  82. GRB 250625A: SAO RAS possible optical afterglow
  83. GRB 250625A: Enhanced Swift-XRT position
  84. GRB 250625A: Swift detection of a burst
  85. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  86. GRB 241018A: Maidanak optical observations
  87. GRB 250620C: AstroSat CZTI detection
  88. Fermi GRB 250624A: Global MASTER-Net observations report
  89. GRB 250521A: VZLUSAT-2 detection
  90. GRB 250617B: Swift-BAT refined analysis
  91. Fermi trigger No 772190032: Global MASTER-Net observations report
  92. IPN triangulation of GRB 250620С (long/bright)
  93. GRB 250620C: SVOM/GRM observation
  94. GRB 250620A: SVOM/GRM observation of a short burst
  95. GRB250620A: Fermi GBM Observation
  96. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  97. GRB 250619B: Fermi GBM Observation
  98. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  99. GRB250620C: Fermi GBM Observation
  100. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst

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