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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"
  1. GRB 231115A position consistent with M 82 galaxy
  2. GRB 231115A: Fermi GBM Final Real-time Localization
  3. LIGO/Virgo/KAGRA S231113bw: Updated Sky localization, EM Bright Classification, and Source Classification
  4. GRB 231111A: Swift-BAT refined analysis
  5. LIGO/Virgo/KAGRA S231113bw: Zwicky Transient Facility observations
  6. LIGO/Virgo/KAGRA S231114n: Updated Sky localization
  7. Fermi GRB 231114A: Global MASTER-Net observations report
  8. GRB 231113A (short): Glowbug gamma-ray detection
  9. GRB 231114A (short): Glowbug gamma-ray detection
  10. LIGO/Virgo/KAGRA S231113bw: GROWTH-India coverage and upper limits
  11. GECAM-B observation of a short burst from SGR J1555-5402
  12. GRB 231114A: Fermi GBM Final Localization
  13. LIGO/Virgo S231113bw: upper limits from AGILE/MCAL
  14. LIGO/Virgo/KAGRA S231114n: Identification of a GW compact binary merger candidate
  15. SGRJ1555-5402: Swift/BAT-GUANO arcminute localization of a SGR flare
  16. LIGO/Virgo/KAGRA S231113bw: Upper limits from Fermi-GBM Observations
  17. GRB 231110A: CALET Gamma-Ray Burst Monitor detection
  18. LIGO/Virgo/KAGRA S231113cd: Coverage and upper limits from MAXI/GSC observations
  19. LIGO/Virgo/KAGRA S231113bb: Updated Sky localization
  20. LIGO/Virgo/KAGRA S231113bw: Coverage and upper limits from MAXI/GSC observations
  21. LIGO/Virgo/KAGRA S231113bw: Identification of a GW compact binary merger candidate
  22. GRB 231110A: Swift-BAT refined analysis
  23. GRB231111A: MDM 2.4m Hiltner Telescope Observation
  24. GRB 231106A: Glowbug gamma-ray detection
  25. GRB 231111A: Xinglong-2.16m optical observations
  26. GRB 231110A: Swift-UVOT Upper Limits
  27. LIGO/Virgo/KAGRA S231113bb: Identification of a GW compact binary merger candidate
  28. GRB 231111A: Afterglow redshift from OSIRIS+/GTC
  29. GRB 231104A: VZLUSAT-2 detection
  30. GRB 231111A: TNG tentative redshift
  31. GRB 231110A: Glowbug gamma-ray detection
  32. GRB 231110A: AstroSat CZTI detection
  33. GRB 231111A NUTTelA-TAO / BSTI Early Measurements
  34. GRB 231111A: Leavitt Observatory optical observations
  35. GRB231111A: Optical follow-up observations with Mephisto
  36. GRB 231111A: GMG observation (correction)
  37. LIGO/Virgo/KAGRA S231112ag: Retraction of GW compact binary merger candidate
  38. GRB 231111A: GMG observation upper limit
  39. GRB 231106B: GRBAlpha detection
  40. GRB 231111A: Osservatorio Astronomico "Nastro Verde" optical observations with detection of an optical counterpart
  41. GRB 231110A: Terskol Zeiss-2000 optical upper limit
  42. GRB 231111A: Swift-XRT refined Analysis
  43. GRB 231111A: Mondy optical observations
  44. GRB 231111A: GECAM-C detection of a long burst (correction)
  45. GRB 231110A: GECAM-B detection (correction)
  46. GRB 231111A: Enhanced Swift-XRT position
  47. GRB 231111A: GECAM-C detection of a long burst
  48. GRB 231110A: GECAM detection
  49. GRB 231110A: GOTO optical upper limits
  50. GRB 231110A: SAO RAS optical observations
  51. GRB 231110A: Swift-XRT afterglow detection
  52. GRB231111A: YAHPT Observations
  53. GRB231111A: GIT confirmation of the optical afterglow
  54. GRB 231111A: MASTER OT earlier detection
  55. GRB 231111A: Nanshan/HMT optical observations
  56. GRB 231111A: Swift detection of a burst with an optical counterpart
  57. Swift GRB231111.60: Global MASTER-Net observations report
  58. GRB231110A: WFST Observation and upper limits
  59. Swift GRB231110.89: Global MASTER-Net observations report
  60. GRB 231110A: Swift detection of a burst
  61. LIGO/Virgo/KAGRA S231110g: Updated Sky localization
  62. LIGO/Virgo/KAGRA S231110g: Identification of a GW compact binary merger candidate
  63. GRB 231109A: Fermi GBM Final Localization
  64. IceCube-231103A: No candidates from the Zwicky Transient Facility
  65. LIGO/Virgo/KAGRA S231108u: Updated Sky localization
  66. Fermi trigger No 721204446: Global MASTER-Net observations report
  67. Fermi GRB 231108A: Global MASTER-Net observations report
  68. GRB 231108A: Fermi GBM Final Real-time Localization
  69. LIGO/Virgo/KAGRA O4 Landscape
  70. LIGO/Virgo/KAGRA S231108u: Identification of a GW compact binary merger candidate
  71. GRB 231106A: AstroSat CZTI detection
  72. GRB 231106A: CALET Gamma-Ray Burst Monitor detection
  73. GRB 231104A: Swift-BAT refined analysis
  74. Fermi trigger No 721006392: Global MASTER-Net observations report
  75. Fermi Gamma-ray Burst Monitor trigger 231107654 / 721064512 is not a GRB
  76. GRB 231104A: FRAM-ORM optical limit
  77. LIGO/Virgo/KAGRA S231102w: Upper limits from Swift/BAT-GUANO
  78. Fermi GRB 231106A: Global MASTER-Net observations report
  79. GRB 231104A: Wendelstein Optical/Infrared Observations
  80. GRB 231104A: NuSTAR Observation of the prompt emission
  81. GRB 231106A: Fermi GBM Final Real-time Localization
  82. GRB 231104A: 3.6m DOT optical upper limit
  83. IceCube-231103A: Upper limits from a search for additional neutrino events in IceCube
  84. LIGO/Virgo/KAGRA S231106y: one counterpart neutrino candidate from IceCube neutrino searches
  85. Fermi-LAT gamma-ray observations of IceCube-231103A
  86. GRB 231104A: NOT upper limit
  87. GRB 231104A: Fermi GBM Observation
  88. GRB 231104B: Fermi GBM Final Real-time Localization
  89. Fermi GRB 231103A: Global MASTER-Net observations report
  90. LIGO/Virgo/KAGRA S231104ac: Updated Sky localization
  91. GRB 231104A: AKO Upper Limit
  92. GRB 231104A: AstroSat CZTI detection
  93. GRB 231104A: Swift-XRT refined Analysis
  94. GRB 231104A: Fermi-LAT detection
  95. LIGO/Virgo/KAGRA S231104ac: Identification of a GW compact binary merger candidate
  96. GRB 231104A: Swift/UVOT Upper Limits
  97. GRB 231104A: Enhanced Swift-XRT position
  98. GRB231104A: LCOGT Optical Upper Limits
  99. GRB 231104A: Swift detection of a bright burst
  100. GRB 231104A: Fermi GBM Final Real-time Localization

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