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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: Fermi Observations of a probable Magnetar Giant Flare from M82
  2. GRB 231115A: archival HST observations
  3. Integral GRB231115.65: Global MASTER-Net observations report
  4. GRB 231115A: GROWTH-India discovery of a potential optical counterpart
  5. GRB 231115A: Swift ToO observations
  6. Fermi GRB 231115A: Global MASTER-Net observations report
  7. GRB 231115A: significance of INTEGRAL localization alignment with M82
  8. GRB 231115A: a short hard GRB detected by IBAS, poistionally coincident with M82
  9. GRB 231115A position consistent with M 82 galaxy
  10. GRB 231115A: Fermi GBM Final Real-time Localization
  11. LIGO/Virgo/KAGRA S231113bw: Updated Sky localization, EM Bright Classification, and Source Classification
  12. GRB 231111A: Swift-BAT refined analysis
  13. LIGO/Virgo/KAGRA S231113bw: Zwicky Transient Facility observations
  14. LIGO/Virgo/KAGRA S231114n: Updated Sky localization
  15. Fermi GRB 231114A: Global MASTER-Net observations report
  16. GRB 231113A (short): Glowbug gamma-ray detection
  17. GRB 231114A (short): Glowbug gamma-ray detection
  18. LIGO/Virgo/KAGRA S231113bw: GROWTH-India coverage and upper limits
  19. GECAM-B observation of a short burst from SGR J1555-5402
  20. GRB 231114A: Fermi GBM Final Localization
  21. LIGO/Virgo S231113bw: upper limits from AGILE/MCAL
  22. LIGO/Virgo/KAGRA S231114n: Identification of a GW compact binary merger candidate
  23. SGRJ1555-5402: Swift/BAT-GUANO arcminute localization of a SGR flare
  24. LIGO/Virgo/KAGRA S231113bw: Upper limits from Fermi-GBM Observations
  25. GRB 231110A: CALET Gamma-Ray Burst Monitor detection
  26. LIGO/Virgo/KAGRA S231113cd: Coverage and upper limits from MAXI/GSC observations
  27. LIGO/Virgo/KAGRA S231113bb: Updated Sky localization
  28. LIGO/Virgo/KAGRA S231113bw: Coverage and upper limits from MAXI/GSC observations
  29. LIGO/Virgo/KAGRA S231113bw: Identification of a GW compact binary merger candidate
  30. GRB 231110A: Swift-BAT refined analysis
  31. GRB231111A: MDM 2.4m Hiltner Telescope Observation
  32. GRB 231106A: Glowbug gamma-ray detection
  33. GRB 231111A: Xinglong-2.16m optical observations
  34. GRB 231110A: Swift-UVOT Upper Limits
  35. LIGO/Virgo/KAGRA S231113bb: Identification of a GW compact binary merger candidate
  36. GRB 231111A: Afterglow redshift from OSIRIS+/GTC
  37. GRB 231104A: VZLUSAT-2 detection
  38. GRB 231111A: TNG tentative redshift
  39. GRB 231110A: Glowbug gamma-ray detection
  40. GRB 231110A: AstroSat CZTI detection
  41. GRB 231111A NUTTelA-TAO / BSTI Early Measurements
  42. GRB 231111A: Leavitt Observatory optical observations
  43. GRB231111A: Optical follow-up observations with Mephisto
  44. GRB 231111A: GMG observation (correction)
  45. LIGO/Virgo/KAGRA S231112ag: Retraction of GW compact binary merger candidate
  46. GRB 231111A: GMG observation upper limit
  47. GRB 231106B: GRBAlpha detection
  48. GRB 231111A: Osservatorio Astronomico "Nastro Verde" optical observations with detection of an optical counterpart
  49. GRB 231110A: Terskol Zeiss-2000 optical upper limit
  50. GRB 231111A: Swift-XRT refined Analysis
  51. GRB 231111A: Mondy optical observations
  52. GRB 231111A: GECAM-C detection of a long burst (correction)
  53. GRB 231110A: GECAM-B detection (correction)
  54. GRB 231111A: Enhanced Swift-XRT position
  55. GRB 231111A: GECAM-C detection of a long burst
  56. GRB 231110A: GECAM detection
  57. GRB 231110A: GOTO optical upper limits
  58. GRB 231110A: SAO RAS optical observations
  59. GRB 231110A: Swift-XRT afterglow detection
  60. GRB231111A: YAHPT Observations
  61. GRB231111A: GIT confirmation of the optical afterglow
  62. GRB 231111A: MASTER OT earlier detection
  63. GRB 231111A: Nanshan/HMT optical observations
  64. GRB 231111A: Swift detection of a burst with an optical counterpart
  65. Swift GRB231111.60: Global MASTER-Net observations report
  66. GRB231110A: WFST Observation and upper limits
  67. Swift GRB231110.89: Global MASTER-Net observations report
  68. GRB 231110A: Swift detection of a burst
  69. LIGO/Virgo/KAGRA S231110g: Updated Sky localization
  70. LIGO/Virgo/KAGRA S231110g: Identification of a GW compact binary merger candidate
  71. GRB 231109A: Fermi GBM Final Localization
  72. IceCube-231103A: No candidates from the Zwicky Transient Facility
  73. LIGO/Virgo/KAGRA S231108u: Updated Sky localization
  74. Fermi trigger No 721204446: Global MASTER-Net observations report
  75. Fermi GRB 231108A: Global MASTER-Net observations report
  76. GRB 231108A: Fermi GBM Final Real-time Localization
  77. LIGO/Virgo/KAGRA O4 Landscape
  78. LIGO/Virgo/KAGRA S231108u: Identification of a GW compact binary merger candidate
  79. GRB 231106A: AstroSat CZTI detection
  80. GRB 231106A: CALET Gamma-Ray Burst Monitor detection
  81. GRB 231104A: Swift-BAT refined analysis
  82. Fermi trigger No 721006392: Global MASTER-Net observations report
  83. Fermi Gamma-ray Burst Monitor trigger 231107654 / 721064512 is not a GRB
  84. GRB 231104A: FRAM-ORM optical limit
  85. LIGO/Virgo/KAGRA S231102w: Upper limits from Swift/BAT-GUANO
  86. Fermi GRB 231106A: Global MASTER-Net observations report
  87. GRB 231104A: Wendelstein Optical/Infrared Observations
  88. GRB 231104A: NuSTAR Observation of the prompt emission
  89. GRB 231106A: Fermi GBM Final Real-time Localization
  90. GRB 231104A: 3.6m DOT optical upper limit
  91. IceCube-231103A: Upper limits from a search for additional neutrino events in IceCube
  92. LIGO/Virgo/KAGRA S231106y: one counterpart neutrino candidate from IceCube neutrino searches
  93. Fermi-LAT gamma-ray observations of IceCube-231103A
  94. GRB 231104A: NOT upper limit
  95. GRB 231104A: Fermi GBM Observation
  96. GRB 231104B: Fermi GBM Final Real-time Localization
  97. Fermi GRB 231103A: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S231104ac: Updated Sky localization
  99. GRB 231104A: AKO Upper Limit
  100. GRB 231104A: AstroSat CZTI detection

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