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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"

26367 results found.

  1. GRB 250706A: SAO RAS optical observations
  2. EP250704A: NOWT Detection
  3. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  4. GRB250706B: Swift-XRT counterpart detection
  5. GRB 250706B: iTelescope optical observations
  6. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  7. GRB 250706B: SVOM/VT optical observation
  8. GRB 250706B: TRT bright optical counterpart detection
  9. GRB 250706A: GROWTH-India Telescope optical upper limit
  10. GRB 250706B: SVOM detection of a long burst
  11. GRB 250706A: Swift detection of a burst
  12. GRB 250704B: Swift-XRT refined Analysis
  13. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  14. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  15. GRB 250703A: EIRSAT-1 GMOD Detection
  16. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  17. GRB 250704B: Swift/UVOT Upper Limits
  18. GRB 250704A: Swift/UVOT Detection
  19. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  20. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  21. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  22. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  23. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  24. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  25. GRB 250702F: Kilonova-Catcher optical afterglow detection
  26. GRB 250702F: Monte Agliale Observatory optical observations
  27. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  28. EP250704a / GRB 250704B: JinShan optical observations
  29. EP250704a / GRB 250704B: SAO RAS optical observations
  30. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  31. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  32. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  33. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  34. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  35. EP250704a / GRB250704B: Swift-XRT counterpart detection
  36. GRB 250704A: Swift-XRT afterglow detection
  37. EP250704a / GRB 250704B - REM observations
  38. GRB 250702F: GROWTH-India Telescope optical observations
  39. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  40. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  41. EP250702a: WFST optical observations
  42. EP250704a: COLIBRÍ optical counterpart candidate
  43. EP250704a: Einstein Probe detection of an X-ray transient
  44. GRB 250704A: REM detection of the optical afterglow
  45. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  46. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  47. GRB 250704A: SVOM detection of a burst
  48. GRB 250702F: Swift/UVOT Detection
  49. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  50. GRB 250702F: Swift-XRT refined Analysis
  51. GRB 250702F: Fermi GBM Observation
  52. GRB 250702F: Leavitt Observatory optical observations
  53. GRB 250702F: AKO Optical Afterglow Detection
  54. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  55. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  56. GRB 250702F: Skynet Optical Observations
  57. GRB 250424A: VIRT Optical Upper Limit
  58. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  59. GRB 250702F: TRT Optical Observation
  60. GRB 250703A: DDOTI Optical Upper Limit
  61. GRB 250702F: REM optical afterglow detection
  62. EP250702a: Global MASTER-Net observations report
  63. GRB 250702F: DDOTI Optical Observation
  64. GRB 250702F: COLIBRÍ Observations of the Afterglow
  65. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  66. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  67. GRB 250702F: Enhanced Swift-XRT position
  68. GRB 250702F: NOT observations of the optical afterglow
  69. GRB 250702F: Swift detection of a burst with an optical counterpart
  70. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  71. GRB 250702A: Fermi GBM Detection
  72. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  73. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  74. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  75. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  76. GRB 250628B: Swift-XRT observations
  77. GRB 250628B: EP-FXT counterpart detection
  78. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  79. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  80. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  81. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  82. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  83. GRB 250628A: REM optical/NIR upper limits
  84. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  85. GRB 250628B: SVOM detection of a long burst
  86. GRB 250628A: VLT/X-shooter upper limits
  87. GRB 250628A: Swift/UVOT Upper Limits
  88. GRB 250628A: Swift-XRT refined Analysis
  89. GRB 250628A: Enhanced Swift-XRT position
  90. GRB 250628A: Swift detection of a burst
  91. GRB 250625A: Swift-BAT refined analysis
  92. GRB 250625A: Leavitt Observatory afterglow detection
  93. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  94. GRB 250625A: SVOM/C-GFT upper limit in early phase
  95. GRB 250625A: Swift/UVOT Upper Limits
  96. GRB 250625A: ABObservatory afterglow detection
  97. GRB 250625A: OHP/T193 optical detection
  98. GRB 250625A: COLIBRÍ optical observations
  99. GRB 250625A: Swift-XRT refined Analysis
  100. GRB 250625A: JinShan optical observations

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