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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"

3797 results found.

  1. EP250220a: 1.6m Mephisto observations
  2. SVOM trigger sb25022102 is not an astrophysical event
  3. SVOM/sb25022102: SVOM detection of an X-ray transient
  4. GRB 250221A: Swift detection of a burst with an optical counterpart
  5. Swift GRB250221.15: Global MASTER-Net observations report
  6. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  7. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  8. Fermi GRB 250217A: Global MASTER-Net observations report
  9. EP250215a: Global MASTER-Net observations report
  10. Fermi GRB 250212A: Global MASTER-Net observations report
  11. Fermi trigger No 760945500: Global MASTER-Net observations report
  12. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  13. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  14. EP250207b: Global MASTER-Net observations report
  15. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  16. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  17. IceCube Alert 250207.09: Global MASTER-Net observations report
  18. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  19. GRB 250207B: Swift-XRT observations
  20. GRB 250207B: Tiled Swift observations
  21. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  22. GRB 250207B: MAXI/GSC detection
  23. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  24. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  25. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  26. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  27. Konus-Wind detection of GRB 250202B
  28. IPN triangulation of GRB 250202B
  29. GRB 250202B: NuSTAR detection of the prompt emission
  30. GRB 250202B: Fermi GBM Detection
  31. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  32. GRB 250202B: Fermi GBM Final Real-time Localization
  33. GRB 250129A: 1.3m DFOT Optical observations
  34. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  35. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  36. Fermi GRB 250128B: Global MASTER-Net observations report
  37. Fermi GRB 250127B: Global MASTER-Net observations report
  38. IPN triangulation of GRB 250119C
  39. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  40. GRB 250126A: MAXI/GSC detection
  41. GRB 250114A: Swift-BAT refined analysis
  42. GRB 250101A: Terskol Zeiss-2000 optical observations
  43. EP250111a: Mondy optical observation
  44. EP250111a: Global MASTER-Net observations report
  45. GRB 250108B: 1.3m DFOT upper limit
  46. EP250109a: Global MASTER-Net observations report
  47. EP250108a: Global MASTER-Net observations report
  48. Fermi GRB 250107B: Global MASTER-Net observations report
  49. Fermi trigger No 757753930: Global MASTER-Net observations report
  50. GRB 250103A: Fermi GBM Observation
  51. GRB 250103A: SVOM/C-GFT optical upper limit
  52. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  53. GRB 250101A: OASDG optical observations
  54. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  55. GRB 241228B: SAO RAS optical observations
  56. Konus-Wind detection of GRB 241228A
  57. GRB 241229B: Swift-BAT refined analysis
  58. Fermi GRB 241228B: Global MASTER-Net observations report
  59. GRB 241228A: Fermi GBM Observation
  60. GRB 241228B: TRT optical counterpart confirmation
  61. GRB 241228A: Swift detection of a burst
  62. Fermi trigger No 756678579: Global MASTER-Net observations report
  63. GRB 241217A/EP241217b: SOAR afterglow detection
  64. GRB 241217A/EP241217B: Fermi-GBM Sub-Threshold Detection
  65. EP241217a: refined EP-WXT analysis and EP-FXT follow-up observations
  66. GRB 241217A: refined SVOM/MXT data analysis. Long lasting X-ray emission.
  67. EP241217a: Liverpool Telescope optical follow-up
  68. EP241217a: Global MASTER-Net observations report
  69. GRB 241217A: GMG Optical Upper Limit
  70. GRB 241217A : SVOM/ECLAIRs,GRM,MXT detection of a long burst with a bright X-ray afterglow candidate
  71. GRB 241213B: Swift-XRT observations
  72. GRB 241213B: Tiled Swift observations
  73. GRB 241213B: CALET Gamma-Ray Burst Monitor detection
  74. GRB 241213B: MAXI/GSC detection
  75. EP241208a: Global MASTER-Net observations report
  76. Fermi GRB 241209E: Global MASTER-Net observations report
  77. Fermi GRB 241209A: Global MASTER-Net observations report
  78. GRB 241207C: MASTER optical observations
  79. GRB 241207C: Tiled Swift observations
  80. GRB 241207C: MAXI/GSC detection
  81. Fermi GRB 241206A: Global MASTER-Net observations report
  82. Fermi GRB 241204A: Global MASTER-Net observations report
  83. Fermi GRB 241201A: Global MASTER-Net observations report
  84. LIGO/Virgo/KAGRA S241201ac: Identification of a GW compact binary merger candidate
  85. GRB 241127A: Swift-BAT refined analysis
  86. GRB 241026A: radio detection with the VLA
  87. GRB241120A: OHP/T193 optical observations
  88. GRB 241120A: Mondy and AbAO optical observations
  89. Fermi GRB 241118A: Global MASTER-Net observations report
  90. LIGO/Virgo/KAGRA S241114bi: Coverage and upper limits from MAXI/GSC observations
  91. EP241113a: Global MASTER-Net observations report
  92. Fermi trigger No 753166198: Global MASTER-Net observations report
  93. Fermi-GBM Sub-Threshold Detection of GRB 241112B
  94. GRB 241112B: SVOM/GRM observation
  95. GRB 241112B : detection of a long GRB by SVOM/ECLAIRs
  96. Fermi trigger No 752990530: Global MASTER-Net observations report
  97. Fermi trigger No 752878030: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S241109bn: Coverage and upper limits from MAXI/GSC observations
  99. EP241107a: AKO Optical Afterglow Follow-Up Observations
  100. GRB 240511A: LCO upper limits

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