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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"

26345 results found.

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

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