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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"

32546 results found.

  1. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  2. GRB 250702F: TRT Optical Observation
  3. GRB 250703A: DDOTI Optical Upper Limit
  4. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  5. GRB 250702F: REM optical afterglow detection
  6. EP250702a: Global MASTER-Net observations report
  7. GRB 250702F: DDOTI Optical Observation
  8. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  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. Fermi GRB 250702E: Global MASTER-Net observations report
  12. Fermi GRB 250702B: Global MASTER-Net observations report
  13. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  14. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  15. GRB 250702F: NOT observations of the optical afterglow
  16. GRB 250702F: MASTER optical afterglow observation
  17. Fermi GRB 250702F: Global MASTER-Net observations report
  18. Fermi GRB 250702C: Global MASTER-Net observations report
  19. GRB 250702F: GOTO optical counterpart detection
  20. GRB 250702F: Swift detection of a burst with an optical counterpart
  21. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  22. Konus-Wind detection of GRB 250627A
  23. IPN triangulation of GRB 250627A (short)
  24. GRB 250702A: Fermi GBM Detection
  25. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  26. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  27. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  28. GRB 250628B: Swift-XRT observations
  29. GRB 250628B: SVOM/VT optical upper limit
  30. GRB 250628B: EP-FXT counterpart detection
  31. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  32. GRB 250627A: Insight-HXMT detection
  33. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  34. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  35. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  36. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  37. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  38. GRB 250628A: REM optical/NIR upper limits
  39. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  40. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  41. GRB 250628A: VLT/X-shooter upper limits
  42. GRB 250628A: Swift/UVOT Upper Limits
  43. Fermi GRB 250626A: Global MASTER-Net observations report
  44. Swift GRB 250628A: Global MASTER-Net observations report
  45. GRB 250625A: Swift-BAT refined analysis
  46. GRB 250625A: Leavitt Observatory afterglow detection
  47. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  48. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  49. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  50. GRB 250625A: SVOM/C-GFT upper limit in early phase
  51. GRB 250625A: GECAM-B detection
  52. GRB 250625A: Swift/UVOT Upper Limits
  53. GRB 250625A: ABObservatory afterglow detection
  54. GRB 250625A: OHP/T193 optical detection
  55. GRB 250625A: COLIBRÍ optical observations
  56. GRB 250625A: Fermi-LAT detection
  57. GRB 250625A: JinShan optical observations
  58. GRB250625A: Fermi GBM Observation
  59. Swift GRB 250625A: Global MASTER-Net observations report
  60. GRB 250625A: NOT z-band upper limit
  61. GRB 250625A: SVOM/VT optical confirmation
  62. GRB 250620B: Fermi GBM Observation
  63. GRB 250625A: SAO RAS possible optical afterglow
  64. Fermi GRB 250625A: Global MASTER-Net observations report
  65. GRB 250625A: Swift detection of a burst
  66. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  67. GRB 250620A: AstroSat CZTI detection
  68. GRB 241018A: Maidanak optical observations
  69. GRB 250620C: AstroSat CZTI detection
  70. Fermi GRB 250624A: Global MASTER-Net observations report
  71. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  72. Fermi GRB 250623A: Global MASTER-Net observations report
  73. GRB 250521A: VZLUSAT-2 detection
  74. GRB 250617B: Swift-BAT refined analysis
  75. Konus-Wind detection of GRB 250620C
  76. IPN triangulation of GRB 250620C (long/bright)
  77. GRB 250620C: SVOM/GRM observation
  78. GRB 250620A: SVOM/GRM observation of a short burst
  79. GRB250620A: Fermi GBM Observation
  80. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  81. Fermi GRB 250621A: Global MASTER-Net observations report
  82. GRB 250619B: Fermi GBM Observation
  83. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  84. GRB 250506A - SVOM/ECLAIRs Refined analysis
  85. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  86. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  87. GRB 250617B: Nickel telescope optical observations
  88. GRB 250615A: Kilonova-Catcher optical upper limits
  89. GRB 250617B: Assy AZT-20 Optical Observations
  90. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  91. Fermi GRB 250617A: Global MASTER-Net observations report
  92. GRB 250615A/EP250615a: FTW optical and NIR observations
  93. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  94. GRB 250617B: Swift/UVOT Detection
  95. GRB 250617B: Kilonova-Catcher optical afterglow detection
  96. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  97. GRB 250617B: COLIBRÍ optical observations
  98. GRB 250617B: NOT NIR observations of the afterglow
  99. GRB 250617B: SVOM/VT optical observation
  100. GRB 250617B: NUTTelA-TAO early time optical observations

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