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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"

26481 results found.

  1. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  2. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  3. GRB 250628A: REM optical/NIR upper limits
  4. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  5. GRB 250628B: SVOM detection of a long burst
  6. GRB 250628A: VLT/X-shooter upper limits
  7. GRB 250628A: Swift/UVOT Upper Limits
  8. GRB 250628A: Swift-XRT refined Analysis
  9. GRB 250628A: Enhanced Swift-XRT position
  10. GRB 250628A: Swift detection of a burst
  11. GRB 250625A: Swift-BAT refined analysis
  12. GRB 250625A: Leavitt Observatory afterglow detection
  13. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  14. GRB 250625A: SVOM/C-GFT upper limit in early phase
  15. GRB 250625A: Swift/UVOT Upper Limits
  16. GRB 250625A: ABObservatory afterglow detection
  17. GRB 250625A: OHP/T193 optical detection
  18. GRB 250625A: COLIBRÍ optical observations
  19. GRB 250625A: Swift-XRT refined Analysis
  20. GRB 250625A: JinShan optical observations
  21. GRB250625A: Fermi GBM Observation
  22. GRB 250620B: Fermi GBM Observation
  23. GRB 250625A: SAO RAS possible optical afterglow
  24. GRB 250625A: Enhanced Swift-XRT position
  25. GRB 250625A: Swift detection of a burst
  26. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  27. GRB 241018A: Maidanak optical observations
  28. GRB 250620C: AstroSat CZTI detection
  29. Fermi GRB 250624A: Global MASTER-Net observations report
  30. GRB 250521A: VZLUSAT-2 detection
  31. GRB 250617B: Swift-BAT refined analysis
  32. Fermi trigger No 772190032: Global MASTER-Net observations report
  33. IPN triangulation of GRB 250620С (long/bright)
  34. GRB 250620C: SVOM/GRM observation
  35. GRB 250620A: SVOM/GRM observation of a short burst
  36. GRB250620A: Fermi GBM Observation
  37. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  38. GRB 250619B: Fermi GBM Observation
  39. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  40. GRB250620C: Fermi GBM Observation
  41. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  42. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  43. Fermi trigger No 772128434: Global MASTER-Net observations report
  44. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  45. GRB 250617B: Nickel telescope optical observations
  46. GRB 250615A: Kilonova-Catcher optical upper limits
  47. GRB 250617B: Assy AZT-20 Optical Observations
  48. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  49. Fermi GRB 250617A: Global MASTER-Net observations report
  50. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  51. GRB 250617B: Swift/UVOT Detection
  52. GRB 250617B: Kilonova-Catcher optical afterglow detection
  53. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  54. GRB 250617B: COLIBRÍ optical observations
  55. GRB 250617B: NOT NIR observations of the afterglow
  56. GRB 250617B: Swift-XRT refined Analysis
  57. GRB 250617B: NUTTelA-TAO early time optical observations
  58. GRB 250617B: Enhanced Swift-XRT position
  59. GRB 250617B: Fermi GBM Observation
  60. GRB 250615A: Swift-BAT refined analysis
  61. GRB 250617B: SAO RAS optical observations
  62. GRB 250617B: Swift detection of a burst with an optical counterpart
  63. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  64. EP#01709178975: Swift-XRT counterpart detection
  65. EP-WXT trigger 01709178975: GOTO optical upper limit
  66. GRB 250615A / EP250615a: AstroSat CZTI detection
  67. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  68. GRB 250615A: COLIBRÍ optical upper limit
  69. GRB 250615A: DDOTI Optical Upper Limit
  70. GRB 250615A: Swift/UVOT Upper Limits
  71. GRB 250615A: Swift-XRT refined Analysis
  72. sb25061207/SVOM: T120 OHP optical upper limit
  73. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  74. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  75. GRB 250615A: Enhanced Swift-XRT position
  76. GRB 250615A: Swift detection of a burst
  77. Fermi trigger No 771718064: Global MASTER-Net observations report
  78. sb25061207: Mephisto optical upper limits
  79. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  80. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  81. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  82. sb25061218: Swift-XRT observations
  83. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  84. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  85. sb25061207: EP-FXT follow-up observation and afterglow candidate
  86. GRB 250612B: Fermi GBM Observation
  87. EP250612a: SVOM/VT optical candidate
  88. GRB 250612C: Fermi GBM Observation
  89. sb25061218: SVOM detection of a X-ray transient
  90. sb25061207: Swift-XRT observations
  91. EP250612a/GRB 250612B: JinShan optical upper limit
  92. sb25061207: SVOM/VT optical counterpart
  93. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  94. GRB 250610B: Swift-XRT refined Analysis
  95. EP250610a: Upper limit from Fermi-GBM Observations
  96. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  97. EP250612a: Einstein Probe detection of an X-ray transient
  98. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  99. sb25061207: SVOM detection of a X-ray transient
  100. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854

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