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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"

45450 results found.

  1. GRB 250702A: Fermi GBM Final Real-time Localization
  2. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  4. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  5. GRB 250628B: Swift-XRT observations
  6. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  7. GRB 250628B: SVOM/VT optical upper limit
  8. GRB 250628B: EP-FXT counterpart detection
  9. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  10. GRB 250627A: Insight-HXMT detection
  11. GRB 250627A: SVOM/GRM detection of a short burst
  12. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  13. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  15. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  16. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  17. GRB 250628A: REM optical/NIR upper limits
  18. GRB 250628C: Fermi GBM Final Real-time Localization
  19. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  20. GRB 250628B: SVOM detection of a long burst
  21. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  22. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  23. GRB 250628A: VLT/X-shooter upper limits
  24. GRB 250628A: Swift/UVOT Upper Limits
  25. GRB 250628A: Swift-XRT refined Analysis
  26. Fermi GRB 250626A: Global MASTER-Net observations report
  27. Swift GRB 250628A: Global MASTER-Net observations report
  28. GRB 250628A: Enhanced Swift-XRT position
  29. GRB 250628A: Swift detection of a burst
  30. GRB 250625A: Swift-BAT refined analysis
  31. GRB 250625A: Leavitt Observatory afterglow detection
  32. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  33. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  34. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  35. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  36. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  37. GRB 250626A: Fermi GBM Final Real-time Localization
  38. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  39. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  40. GRB 250625A: SVOM/C-GFT upper limit in early phase
  41. GRB 250625A: GECAM-B detection
  42. GRB 250625A: Swift/UVOT Upper Limits
  43. GRB 250625A: ABObservatory afterglow detection
  44. GRB 250625A: OHP/T193 optical detection
  45. GRB 250625A: COLIBRÍ optical observations
  46. GRB 250625A: Fermi-LAT detection
  47. GRB 250625A: Swift-XRT refined Analysis
  48. GRB 250625A: JinShan optical observations
  49. GRB250625A: Fermi GBM Observation
  50. Swift GRB 250625A: Global MASTER-Net observations report
  51. GRB 250625A: NOT z-band upper limit
  52. GRB 250625A: SVOM/VT optical confirmation
  53. GRB 250620B: Fermi GBM Observation
  54. GRB 250625A: SAO RAS possible optical afterglow
  55. GRB 250625A: Enhanced Swift-XRT position
  56. Fermi GRB 250625A: Global MASTER-Net observations report
  57. GRB 250625A: Swift detection of a burst
  58. GRB 250625A: Fermi GBM Final Real-time Localization
  59. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  60. GRB 250620A: AstroSat CZTI detection
  61. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  62. GRB 241018A: Maidanak optical observations
  63. GRB 250620C: AstroSat CZTI detection
  64. Fermi GRB 250624A: Global MASTER-Net observations report
  65. GRB 250624A: Fermi GBM Final Real-time Localization
  66. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  67. Fermi GRB 250623A: Global MASTER-Net observations report
  68. GRB 250623A: Fermi GBM Final Real-time Localization
  69. GRB 250521A: VZLUSAT-2 detection
  70. GRB 250617B: Swift-BAT refined analysis
  71. Fermi trigger No 772190032: Global MASTER-Net observations report
  72. Konus-Wind detection of GRB 250620C
  73. IPN triangulation of GRB 250620C (long/bright)
  74. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  75. GRB 250620C: SVOM/GRM observation
  76. GRB 250620A: SVOM/GRM observation of a short burst
  77. GRB250620A: Fermi GBM Observation
  78. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  79. Fermi GRB 250621A: Global MASTER-Net observations report
  80. GRB 250619B: Fermi GBM Observation
  81. GRB 250621A: Fermi GBM Final Real-time Localization
  82. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  83. GRB250620C: Fermi GBM Observation
  84. GRB 250506A - SVOM/ECLAIRs Refined analysis
  85. The EP-WXT trigger 01709179071 is likely a flaring star
  86. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  87. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  88. GRB 250620C: Fermi GBM Final Real-time Localization
  89. Fermi trigger No 772128434: Global MASTER-Net observations report
  90. GRB 250620B: Fermi GBM Final Real-time Localization
  91. GRB 250620A: Fermi GBM Final Real-time Localization
  92. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  93. GRB 250617B: Nickel telescope optical observations
  94. GRB 250619B: Fermi GBM Final Real-time Localization
  95. Fermi trigger No 772058337: Global MASTER-Net observations report
  96. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  97. GRB 250615A: Kilonova-Catcher optical upper limits
  98. GRB 250619A: Fermi GBM Final Real-time Localization
  99. GRB 250617B: Assy AZT-20 Optical Observations
  100. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis

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