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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"

26507 results found.

  1. GRB 250702F: Skynet Optical Observations
  2. GRB 250424A: VIRT Optical Upper Limit
  3. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  4. GRB 250702F: TRT Optical Observation
  5. GRB 250703A: DDOTI Optical Upper Limit
  6. GRB 250702F: REM optical afterglow detection
  7. EP250702a: Global MASTER-Net observations report
  8. GRB 250702F: DDOTI Optical Observation
  9. GRB 250702F: COLIBRÍ Observations of the Afterglow
  10. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  11. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  12. GRB 250702F: Enhanced Swift-XRT position
  13. GRB 250702F: NOT observations of the optical afterglow
  14. GRB 250702F: Swift detection of a burst with an optical counterpart
  15. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  16. GRB 250702A: Fermi GBM Detection
  17. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  18. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  19. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  20. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  21. GRB 250628B: Swift-XRT observations
  22. GRB 250628B: EP-FXT counterpart detection
  23. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  24. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  25. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  26. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  27. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  28. GRB 250628A: REM optical/NIR upper limits
  29. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  30. GRB 250628B: SVOM detection of a long burst
  31. GRB 250628A: VLT/X-shooter upper limits
  32. GRB 250628A: Swift/UVOT Upper Limits
  33. GRB 250628A: Swift-XRT refined Analysis
  34. GRB 250628A: Enhanced Swift-XRT position
  35. GRB 250628A: Swift detection of a burst
  36. GRB 250625A: Swift-BAT refined analysis
  37. GRB 250625A: Leavitt Observatory afterglow detection
  38. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  39. GRB 250625A: SVOM/C-GFT upper limit in early phase
  40. GRB 250625A: Swift/UVOT Upper Limits
  41. GRB 250625A: ABObservatory afterglow detection
  42. GRB 250625A: OHP/T193 optical detection
  43. GRB 250625A: COLIBRÍ optical observations
  44. GRB 250625A: Swift-XRT refined Analysis
  45. GRB 250625A: JinShan optical observations
  46. GRB250625A: Fermi GBM Observation
  47. GRB 250620B: Fermi GBM Observation
  48. GRB 250625A: SAO RAS possible optical afterglow
  49. GRB 250625A: Enhanced Swift-XRT position
  50. GRB 250625A: Swift detection of a burst
  51. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  52. GRB 241018A: Maidanak optical observations
  53. GRB 250620C: AstroSat CZTI detection
  54. Fermi GRB 250624A: Global MASTER-Net observations report
  55. GRB 250521A: VZLUSAT-2 detection
  56. GRB 250617B: Swift-BAT refined analysis
  57. Fermi trigger No 772190032: Global MASTER-Net observations report
  58. IPN triangulation of GRB 250620С (long/bright)
  59. GRB 250620C: SVOM/GRM observation
  60. GRB 250620A: SVOM/GRM observation of a short burst
  61. GRB250620A: Fermi GBM Observation
  62. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  63. GRB 250619B: Fermi GBM Observation
  64. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  65. GRB250620C: Fermi GBM Observation
  66. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  67. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  68. Fermi trigger No 772128434: Global MASTER-Net observations report
  69. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  70. GRB 250617B: Nickel telescope optical observations
  71. GRB 250615A: Kilonova-Catcher optical upper limits
  72. GRB 250617B: Assy AZT-20 Optical Observations
  73. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  74. Fermi GRB 250617A: Global MASTER-Net observations report
  75. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  76. GRB 250617B: Swift/UVOT Detection
  77. GRB 250617B: Kilonova-Catcher optical afterglow detection
  78. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  79. GRB 250617B: COLIBRÍ optical observations
  80. GRB 250617B: NOT NIR observations of the afterglow
  81. GRB 250617B: Swift-XRT refined Analysis
  82. GRB 250617B: NUTTelA-TAO early time optical observations
  83. GRB 250617B: Enhanced Swift-XRT position
  84. GRB 250617B: Fermi GBM Observation
  85. GRB 250615A: Swift-BAT refined analysis
  86. GRB 250617B: SAO RAS optical observations
  87. GRB 250617B: Swift detection of a burst with an optical counterpart
  88. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  89. EP#01709178975: Swift-XRT counterpart detection
  90. EP-WXT trigger 01709178975: GOTO optical upper limit
  91. GRB 250615A / EP250615a: AstroSat CZTI detection
  92. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  93. GRB 250615A: COLIBRÍ optical upper limit
  94. GRB 250615A: DDOTI Optical Upper Limit
  95. GRB 250615A: Swift/UVOT Upper Limits
  96. GRB 250615A: Swift-XRT refined Analysis
  97. sb25061207/SVOM: T120 OHP optical upper limit
  98. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  99. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  100. GRB 250615A: Enhanced Swift-XRT position

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