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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

32716 results found.

  1. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  2. GRB 250627A: Insight-HXMT detection
  3. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  4. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  5. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  6. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  7. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  8. GRB 250628A: REM optical/NIR upper limits
  9. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  10. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  11. GRB 250628A: VLT/X-shooter upper limits
  12. GRB 250628A: Swift/UVOT Upper Limits
  13. Fermi GRB 250626A: Global MASTER-Net observations report
  14. Swift GRB 250628A: Global MASTER-Net observations report
  15. GRB 250625A: Swift-BAT refined analysis
  16. GRB 250625A: Leavitt Observatory afterglow detection
  17. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  18. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  19. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  20. GRB 250625A: SVOM/C-GFT upper limit in early phase
  21. GRB 250625A: GECAM-B detection
  22. GRB 250625A: Swift/UVOT Upper Limits
  23. GRB 250625A: ABObservatory afterglow detection
  24. GRB 250625A: OHP/T193 optical detection
  25. GRB 250625A: COLIBRÍ optical observations
  26. GRB 250625A: Fermi-LAT detection
  27. GRB 250625A: JinShan optical observations
  28. GRB250625A: Fermi GBM Observation
  29. Swift GRB 250625A: Global MASTER-Net observations report
  30. GRB 250625A: NOT z-band upper limit
  31. GRB 250625A: SVOM/VT optical confirmation
  32. GRB 250620B: Fermi GBM Observation
  33. GRB 250625A: SAO RAS possible optical afterglow
  34. Fermi GRB 250625A: Global MASTER-Net observations report
  35. GRB 250625A: Swift detection of a burst
  36. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  37. GRB 250620A: AstroSat CZTI detection
  38. GRB 241018A: Maidanak optical observations
  39. GRB 250620C: AstroSat CZTI detection
  40. Fermi GRB 250624A: Global MASTER-Net observations report
  41. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  42. Fermi GRB 250623A: Global MASTER-Net observations report
  43. GRB 250521A: VZLUSAT-2 detection
  44. GRB 250617B: Swift-BAT refined analysis
  45. Konus-Wind detection of GRB 250620C
  46. IPN triangulation of GRB 250620C (long/bright)
  47. GRB 250620C: SVOM/GRM observation
  48. GRB 250620A: SVOM/GRM observation of a short burst
  49. GRB250620A: Fermi GBM Observation
  50. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  51. Fermi GRB 250621A: Global MASTER-Net observations report
  52. GRB 250619B: Fermi GBM Observation
  53. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  54. GRB 250506A - SVOM/ECLAIRs Refined analysis
  55. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  56. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  57. GRB 250617B: Nickel telescope optical observations
  58. GRB 250615A: Kilonova-Catcher optical upper limits
  59. GRB 250617B: Assy AZT-20 Optical Observations
  60. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  61. Fermi GRB 250617A: Global MASTER-Net observations report
  62. GRB 250615A/EP250615a: FTW optical and NIR observations
  63. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  64. GRB 250617B: Swift/UVOT Detection
  65. GRB 250617B: Kilonova-Catcher optical afterglow detection
  66. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  67. GRB 250617B: COLIBRÍ optical observations
  68. GRB 250617B: NOT NIR observations of the afterglow
  69. GRB 250617B: SVOM/VT optical observation
  70. GRB 250617B: NUTTelA-TAO early time optical observations
  71. Swift GRB 250617B: Global MASTER-Net observations report
  72. GRB 250617B: GOTO optical upper limit
  73. GRB 250617B: Fermi GBM Observation
  74. GRB 250615A: Swift-BAT refined analysis
  75. GRB 250617B: Fermi GBM Final Localization
  76. GRB 250617B: Ondrejov D50 optical afterglow detection
  77. GRB 250617B: SAO RAS optical observations
  78. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  79. IPN triangulation of GRB 250612C (short/hard)
  80. Konus-Wind detection of GRB 250615A / EP250615a
  81. GRB 250615A / EP250615a: AstroSat CZTI detection
  82. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  83. GRB 250615A: COLIBRÍ optical upper limit
  84. GRB 250615A: DDOTI Optical Upper Limit
  85. GRB 250615A: Swift/UVOT Upper Limits
  86. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  87. sb25061207/SVOM: T120 OHP optical upper limit
  88. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  89. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  90. GRID detection of GRB 250612C
  91. sb25061207: Mephisto optical upper limits
  92. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  93. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  94. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  95. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  96. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  97. sb25061207: EP-FXT follow-up observation and afterglow candidate
  98. GRB 250612B: Fermi GBM Observation
  99. EP250612a / GRB 250612B: SVOM/VT optical candidate
  100. EP250612a: Global MASTER-Net observations report

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