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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 231117A: LDT Confirmation of Optical Fading
  2. GRB 231117A: Wendelstein Confirmation of Fading of the Optical Afterglow
  3. GRB 231118B: CALET Gamma-Ray Burst Monitor detection
  4. GRB 231117A: CALET Gamma-Ray Burst Monitor detection
  5. 231118A: Swift-UVOT Detection
  6. GRB231117A: Swift-UVOT detection
  7. GRB 231117A : MITSuME Akeno optical afterglow candidate detection
  8. GRB 231118B: Fermi GBM observation
  9. GRB 231118A: Fermi GBM observation
  10. LIGO/Virgo/KAGRA S231119ab: Coverage and upper limits from MAXI/GSC observations
  11. GRB 231120A: Fermi GBM Final Real-time Localization
  12. GRB 231117A: Swift-XRT refined Analysis
  13. GRB 231118A: Swift-XRT refined Analysis
  14. GRB 231118A: MeerLICHT afterglow detection
  15. LIGO/Virgo/KAGRA S231119u: One counterpart neutrino candidate from IceCube neutrino searches
  16. GRB 231117A: OHP/T120 optical observations
  17. GRB 231118A: VLT/X-shooter redshift
  18. Fermi trigger No 722039659: Global MASTER-Net observations report
  19. GRB 231117A: Pan-STARRS1 follow-up confirms rapid fading
  20. LIGO/Virgo/KAGRA S231119u: Identification of a GW compact binary merger candidate
  21. GRB 231117A: MAAO 0.7-m telescope optical upper limit
  22. GRB 231117A: AKO Follow-Up Observation
  23. GRB 231117A: GECAM-C detection
  24. GRB 231118A: AstroSat CZTI detection
  25. GRB 231115A: Upper limit from CALET Gamma-Ray Burst Monitor
  26. GRB 231117A: 10 GHz VLA detection
  27. GRB 231118A: Las Cumbres optical detection
  28. GRB 231118B: BALROG localization (Fermi Trigger 722039659 / GRB 231118940)
  29. GRB 231118B: Fermi GBM Final Real-time Localization
  30. GRB 231118A: LCOGT Optical Observations
  31. GRB 231118A: MASTER OT observation
  32. GRB 231118A: Continued Skynet Observations
  33. Swift GRB231118.72: Global MASTER-Net observations report
  34. GRB 231118A: Enhanced Swift-XRT position
  35. GRB 231117A: Kinder observations with Lulin observatory for AT 2023yba without fading in r band
  36. GRB 231118A: Swift-XRT position
  37. GRB 231118A: Skynet Optical Afterglow Discovery
  38. GRB 231117A: SOAR/Goodman imaging of the afterglow
  39. GRB 231118A: Swift detection of a burst
  40. GRB 231118A: Fermi GBM Final Real-time Localization
  41. GRB 231117A: Lowell Discovery Telescope Observations
  42. GRB 231117A: ePESSTO+ host galaxy redshift confirmation
  43. GRB 231117A: ATCA detection of a radio counterpart
  44. LIGO/Virgo/KAGRA S231118an: Identification of a GW compact binary merger candidate
  45. GRB 231117A: GRBAlpha detection
  46. LIGO/Virgo/KAGRA S231118ab: Identification of a GW compact binary merger candidate
  47. GRB 231117A: Keck spectroscopy of afterglow candidate
  48. GRB 231115A: Wendelstein Optical/Infrared Observations
  49. GRB 231115A: JinShan optical upper limits
  50. LIGO/Virgo/KAGRA S231118d: Identification of a GW compact binary merger candidate
  51. GRB 231117A: GIT optical follow-up
  52. GRB 231117A: LT observations consistent with fading
  53. GRB 231117A: Keck observations indicate presence of optical afterglow in z~0.3-0.5 galaxy
  54. GRB 231117A: REM optical and NIR early-time observations
  55. GRB231117A: AGILE/MCAL analysis
  56. GRB 231117A: AKO Optical Upper Limit
  57. GRB 231117A: afterglow candidate detection from Kinder observations with Lulin observatory
  58. Swift GRB 231117A: Global MASTER-Net observations report
  59. GRB 231117A (short): Glowbug gamma-ray detection
  60. GRB 231117A: ATLAS non-detection of an optical counterpart
  61. Konus-Wind detection of GRB 231117A (short/hard)
  62. GRB 231115A : OHP/T120 optical upper limit
  63. GRB 231115A: optical observations from INAF observatories
  64. GRB 231117A : MITSuME Akeno optical upper limits
  65. GRB 231117A: AGILE detection of a bright short burst
  66. GRB 231117A: Enhanced Swift-XRT position
  67. GRB 231117A: GOTO optical upper limits
  68. GRB 231117A: AstroSat CZTI detection of a bright short burst
  69. GRB 231117A: Swift detection of a bright short burst
  70. GRB 231115A: Non-detection of radio emission with CHIME/FRB
  71. GRB 231111A: Swift/UVOT Detection
  72. MAGIC observation of GRB 231115A, a possible magnetar giant flare
  73. GRB231115A: Liverpool Telescope imaging
  74. GRB 231115A: NuSTAR Follow-Up Observations
  75. GRB 231115A: Swift/BAT-GUANO detection of a short burst
  76. GRB 231115A: Swift-XRT and Swift-UVOT observations
  77. Fermi GRB 231116A: Global MASTER-Net observations report
  78. Konus-Wind detection of GRB 231115A (a probable Magnetar Giant Flare from M82)
  79. GRB 231115A: AGILE/MCAL upper limits
  80. GRB 231115A: Insight-HXMT/HE detection
  81. GRB 231115A: GBM/Fermi Observations of a probable Giant Flare of Magnetar
  82. GRB 231116A: Fermi GBM Final Real-time Localization
  83. GRB 231115A : MITSuME Akeno and Okayama optical upper limits
  84. GRB 231115A: Gaoyazi/GOT follow-up and archival observations
  85. GRB 231115A / AT2023xvj: Updated GIT analysis
  86. GRB 231115A: archival Chandra X-ray observations
  87. GRB 231115A: Upper limits from a neutrino search with IceCube
  88. GRB 231115A: Kinder observations with Lulin observatory
  89. GRB231115A: GRANDMA Observations
  90. GRB 231115A: GOTO pre-burst limits of AT2023xvj
  91. GRB 231115A: Non-detection in low-latency of gravitational waves with LIGO/Virgo/KAGRA
  92. GRB 231115A: pre-burst ZTF upper limits for GRB optical counterpart candidate
  93. GRB 231106A: TESS identification of candidate optical counterpart
  94. GRB 231115A: MASTER optical observations
  95. GRB 231115A (short): Glowbug gamma-ray detection
  96. GRB 231115A: Fermi Observations of a probable Magnetar Giant Flare from M82
  97. GRB 231115A: archival HST observations
  98. Integral GRB231115.65: Global MASTER-Net observations report
  99. GRB 231115A: GROWTH-India discovery of a potential optical counterpart
  100. GRB 231115A: Swift ToO observations

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