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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 / AT2023xvj: Updated GIT analysis
  2. GRB 231115A: archival Chandra X-ray observations
  3. GRB 231115A: Upper limits from a neutrino search with IceCube
  4. GRB 231115A: Kinder observations with Lulin observatory
  5. GRB231115A: GRANDMA Observations
  6. GRB 231115A: GOTO pre-burst limits of AT2023xvj
  7. GRB 231115A: Non-detection in low-latency of gravitational waves with LIGO/Virgo/KAGRA
  8. GRB 231115A: pre-burst ZTF upper limits for GRB optical counterpart candidate
  9. GRB 231106A: TESS identification of candidate optical counterpart
  10. GRB 231115A: MASTER optical observations
  11. GRB 231115A (short): Glowbug gamma-ray detection
  12. GRB 231115A: Fermi Observations of a probable Magnetar Giant Flare from M82
  13. GRB 231115A: archival HST observations
  14. Integral GRB231115.65: Global MASTER-Net observations report
  15. GRB 231115A: GROWTH-India discovery of a potential optical counterpart
  16. GRB 231115A: Swift ToO observations
  17. Fermi GRB 231115A: Global MASTER-Net observations report
  18. GRB 231115A: significance of INTEGRAL localization alignment with M82
  19. GRB 231115A: a short hard GRB detected by IBAS, poistionally coincident with M82
  20. GRB 231115A position consistent with M 82 galaxy
  21. GRB 231115A: Fermi GBM Final Real-time Localization
  22. LIGO/Virgo/KAGRA S231113bw: Updated Sky localization, EM Bright Classification, and Source Classification
  23. GRB 231111A: Swift-BAT refined analysis
  24. LIGO/Virgo/KAGRA S231113bw: Zwicky Transient Facility observations
  25. LIGO/Virgo/KAGRA S231114n: Updated Sky localization
  26. Fermi GRB 231114A: Global MASTER-Net observations report
  27. GRB 231113A (short): Glowbug gamma-ray detection
  28. GRB 231114A (short): Glowbug gamma-ray detection
  29. LIGO/Virgo/KAGRA S231113bw: GROWTH-India coverage and upper limits
  30. GECAM-B observation of a short burst from SGR J1555-5402
  31. GRB 231114A: Fermi GBM Final Localization
  32. LIGO/Virgo S231113bw: upper limits from AGILE/MCAL
  33. LIGO/Virgo/KAGRA S231114n: Identification of a GW compact binary merger candidate
  34. SGRJ1555-5402: Swift/BAT-GUANO arcminute localization of a SGR flare
  35. LIGO/Virgo/KAGRA S231113bw: Upper limits from Fermi-GBM Observations
  36. GRB 231110A: CALET Gamma-Ray Burst Monitor detection
  37. LIGO/Virgo/KAGRA S231113cd: Coverage and upper limits from MAXI/GSC observations
  38. LIGO/Virgo/KAGRA S231113bb: Updated Sky localization
  39. LIGO/Virgo/KAGRA S231113bw: Coverage and upper limits from MAXI/GSC observations
  40. LIGO/Virgo/KAGRA S231113bw: Identification of a GW compact binary merger candidate
  41. GRB 231110A: Swift-BAT refined analysis
  42. GRB231111A: MDM 2.4m Hiltner Telescope Observation
  43. GRB 231106A: Glowbug gamma-ray detection
  44. GRB 231111A: Xinglong-2.16m optical observations
  45. GRB 231110A: Swift-UVOT Upper Limits
  46. LIGO/Virgo/KAGRA S231113bb: Identification of a GW compact binary merger candidate
  47. GRB 231111A: Afterglow redshift from OSIRIS+/GTC
  48. GRB 231104A: VZLUSAT-2 detection
  49. GRB 231111A: TNG tentative redshift
  50. GRB 231110A: Glowbug gamma-ray detection
  51. GRB 231110A: AstroSat CZTI detection
  52. GRB 231111A NUTTelA-TAO / BSTI Early Measurements
  53. GRB 231111A: Leavitt Observatory optical observations
  54. GRB231111A: Optical follow-up observations with Mephisto
  55. GRB 231111A: GMG observation (correction)
  56. LIGO/Virgo/KAGRA S231112ag: Retraction of GW compact binary merger candidate
  57. GRB 231111A: GMG observation upper limit
  58. GRB 231106B: GRBAlpha detection
  59. GRB 231111A: Osservatorio Astronomico "Nastro Verde" optical observations with detection of an optical counterpart
  60. GRB 231110A: Terskol Zeiss-2000 optical upper limit
  61. GRB 231111A: Swift-XRT refined Analysis
  62. GRB 231111A: Mondy optical observations
  63. GRB 231111A: GECAM-C detection of a long burst (correction)
  64. GRB 231110A: GECAM-B detection (correction)
  65. GRB 231111A: Enhanced Swift-XRT position
  66. GRB 231111A: GECAM-C detection of a long burst
  67. GRB 231110A: GECAM detection
  68. GRB 231110A: GOTO optical upper limits
  69. GRB 231110A: SAO RAS optical observations
  70. GRB 231110A: Swift-XRT afterglow detection
  71. GRB231111A: YAHPT Observations
  72. GRB231111A: GIT confirmation of the optical afterglow
  73. GRB 231111A: MASTER OT earlier detection
  74. GRB 231111A: Nanshan/HMT optical observations
  75. GRB 231111A: Swift detection of a burst with an optical counterpart
  76. Swift GRB231111.60: Global MASTER-Net observations report
  77. GRB231110A: WFST Observation and upper limits
  78. Swift GRB231110.89: Global MASTER-Net observations report
  79. GRB 231110A: Swift detection of a burst
  80. LIGO/Virgo/KAGRA S231110g: Updated Sky localization
  81. LIGO/Virgo/KAGRA S231110g: Identification of a GW compact binary merger candidate
  82. GRB 231109A: Fermi GBM Final Localization
  83. IceCube-231103A: No candidates from the Zwicky Transient Facility
  84. LIGO/Virgo/KAGRA S231108u: Updated Sky localization
  85. Fermi trigger No 721204446: Global MASTER-Net observations report
  86. Fermi GRB 231108A: Global MASTER-Net observations report
  87. GRB 231108A: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA O4 Landscape
  89. LIGO/Virgo/KAGRA S231108u: Identification of a GW compact binary merger candidate
  90. GRB 231106A: AstroSat CZTI detection
  91. GRB 231106A: CALET Gamma-Ray Burst Monitor detection
  92. GRB 231104A: Swift-BAT refined analysis
  93. Fermi trigger No 721006392: Global MASTER-Net observations report
  94. Fermi Gamma-ray Burst Monitor trigger 231107654 / 721064512 is not a GRB
  95. GRB 231104A: FRAM-ORM optical limit
  96. LIGO/Virgo/KAGRA S231102w: Upper limits from Swift/BAT-GUANO
  97. Fermi GRB 231106A: Global MASTER-Net observations report
  98. GRB 231104A: Wendelstein Optical/Infrared Observations
  99. GRB 231104A: NuSTAR Observation of the prompt emission
  100. GRB 231106A: Fermi GBM Final Real-time Localization

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