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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"

43077 results found.

  1. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  2. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  5. GRB 250628A: REM optical/NIR upper limits
  6. GRB 250628C: Fermi GBM Final Real-time Localization
  7. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  8. GRB 250628B: SVOM detection of a long burst
  9. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  10. GRB 250628A: VLT/X-shooter upper limits
  11. GRB 250628A: Swift/UVOT Upper Limits
  12. GRB 250628A: Swift-XRT refined Analysis
  13. Fermi GRB 250626A: Global MASTER-Net observations report
  14. Swift GRB 250628A: Global MASTER-Net observations report
  15. GRB 250628A: Enhanced Swift-XRT position
  16. GRB 250628A: Swift detection of a burst
  17. GRB 250625A: Swift-BAT refined analysis
  18. GRB 250625A: Leavitt Observatory afterglow detection
  19. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  20. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  21. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  22. GRB 250626A: Fermi GBM Final Real-time Localization
  23. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  24. GRB 250625A: SVOM/C-GFT upper limit in early phase
  25. GRB 250625A: GECAM-B detection
  26. GRB 250625A: Swift/UVOT Upper Limits
  27. GRB 250625A: ABObservatory afterglow detection
  28. GRB 250625A: OHP/T193 optical detection
  29. GRB 250625A: COLIBRÍ optical observations
  30. GRB 250625A: Fermi-LAT detection
  31. GRB 250625A: Swift-XRT refined Analysis
  32. GRB 250625A: JinShan optical observations
  33. GRB250625A: Fermi GBM Observation
  34. Swift GRB 250625A: Global MASTER-Net observations report
  35. GRB 250625A: NOT z-band upper limit
  36. GRB 250625A: SVOM/VT optical confirmation
  37. GRB 250620B: Fermi GBM Observation
  38. GRB 250625A: SAO RAS possible optical afterglow
  39. GRB 250625A: Enhanced Swift-XRT position
  40. Fermi GRB 250625A: Global MASTER-Net observations report
  41. GRB 250625A: Swift detection of a burst
  42. GRB 250625A: Fermi GBM Final Real-time Localization
  43. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  44. GRB 250620A: AstroSat CZTI detection
  45. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  46. GRB 241018A: Maidanak optical observations
  47. GRB 250620C: AstroSat CZTI detection
  48. Fermi GRB 250624A: Global MASTER-Net observations report
  49. GRB 250624A: Fermi GBM Final Real-time Localization
  50. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  51. Fermi GRB 250623A: Global MASTER-Net observations report
  52. GRB 250623A: Fermi GBM Final Real-time Localization
  53. GRB 250521A: VZLUSAT-2 detection
  54. GRB 250617B: Swift-BAT refined analysis
  55. Fermi trigger No 772190032: Global MASTER-Net observations report
  56. Konus-Wind detection of GRB 250620C
  57. IPN triangulation of GRB 250620C (long/bright)
  58. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  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. Fermi GRB 250621A: Global MASTER-Net observations report
  64. GRB 250619B: Fermi GBM Observation
  65. GRB 250621A: Fermi GBM Final Real-time Localization
  66. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  67. GRB250620C: Fermi GBM Observation
  68. GRB 250506A - SVOM/ECLAIRs Refined analysis
  69. The EP-WXT trigger 01709179071 is likely a flaring star
  70. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  71. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  72. GRB 250620C: Fermi GBM Final Real-time Localization
  73. Fermi trigger No 772128434: Global MASTER-Net observations report
  74. GRB 250620B: Fermi GBM Final Real-time Localization
  75. GRB 250620A: Fermi GBM Final Real-time Localization
  76. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  77. GRB 250617B: Nickel telescope optical observations
  78. GRB 250619B: Fermi GBM Final Real-time Localization
  79. Fermi trigger No 772058337: Global MASTER-Net observations report
  80. GRB 250615A: Kilonova-Catcher optical upper limits
  81. GRB 250619A: Fermi GBM Final Real-time Localization
  82. GRB 250617B: Assy AZT-20 Optical Observations
  83. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  84. Fermi GRB 250617A: Global MASTER-Net observations report
  85. GRB 250615A/EP250615a: FTW optical and NIR observations
  86. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  87. GRB 250617B: Swift/UVOT Detection
  88. GRB 250617B: Kilonova-Catcher optical afterglow detection
  89. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  90. GRB 250617B: COLIBRÍ optical observations
  91. GRB 250617B: NOT NIR observations of the afterglow
  92. GRB 250617B: Swift-XRT refined Analysis
  93. GRB 250617B: SVOM/VT optical observation
  94. GRB 250617B: NUTTelA-TAO early time optical observations
  95. Fermi trigger No 771886893: Global MASTER-Net observations report
  96. Swift GRB 250617B: Global MASTER-Net observations report
  97. GRB 250617B: GOTO optical upper limit
  98. GRB 250617B: Enhanced Swift-XRT position
  99. GRB 250617B: Fermi GBM Observation
  100. GRB 250615A: Swift-BAT refined analysis

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