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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. LIGO/Virgo/KAGRA S231119u: Updated Sky localization and Source Classification
  2. LIGO/Virgo/KAGRA S231118ab: Updated Sky localization and Source Classification
  3. LIGO/Virgo/KAGRA S231118d: Updated Sky localization and Source Classification
  4. GRB 231118A: VZLUSAT-2 detection
  5. GRB 231117A: AMI-LA radio observations
  6. GRB 231118A: Swift-BAT refined analysis
  7. Konus-Wind detection of GRB 231020A
  8. GRB 231117A: LDT Confirmation of Optical Fading
  9. GRB 231117A: Wendelstein Confirmation of Fading of the Optical Afterglow
  10. GRB 231118B: CALET Gamma-Ray Burst Monitor detection
  11. GRB 231117A: CALET Gamma-Ray Burst Monitor detection
  12. 231118A: Swift-UVOT Detection
  13. GRB231117A: Swift-UVOT detection
  14. GRB 231117A : MITSuME Akeno optical afterglow candidate detection
  15. GRB 231118B: Fermi GBM observation
  16. GRB 231118A: Fermi GBM observation
  17. LIGO/Virgo/KAGRA S231119ab: Coverage and upper limits from MAXI/GSC observations
  18. GRB 231120A: Fermi GBM Final Real-time Localization
  19. GRB 231117A: Swift-XRT refined Analysis
  20. GRB 231118A: Swift-XRT refined Analysis
  21. GRB 231118A: MeerLICHT afterglow detection
  22. LIGO/Virgo/KAGRA S231119u: One counterpart neutrino candidate from IceCube neutrino searches
  23. GRB 231117A: OHP/T120 optical observations
  24. GRB 231118A: VLT/X-shooter redshift
  25. Fermi trigger No 722039659: Global MASTER-Net observations report
  26. GRB 231117A: Pan-STARRS1 follow-up confirms rapid fading
  27. LIGO/Virgo/KAGRA S231119u: Identification of a GW compact binary merger candidate
  28. GRB 231117A: MAAO 0.7-m telescope optical upper limit
  29. GRB 231117A: AKO Follow-Up Observation
  30. GRB 231117A: GECAM-C detection
  31. GRB 231118A: AstroSat CZTI detection
  32. GRB 231115A: Upper limit from CALET Gamma-Ray Burst Monitor
  33. GRB 231117A: 10 GHz VLA detection
  34. GRB 231118A: Las Cumbres optical detection
  35. GRB 231118B: BALROG localization (Fermi Trigger 722039659 / GRB 231118940)
  36. GRB 231118B: Fermi GBM Final Real-time Localization
  37. GRB 231118A: LCOGT Optical Observations
  38. GRB 231118A: MASTER OT observation
  39. GRB 231118A: Continued Skynet Observations
  40. Swift GRB231118.72: Global MASTER-Net observations report
  41. GRB 231118A: Enhanced Swift-XRT position
  42. GRB 231117A: Kinder observations with Lulin observatory for AT 2023yba without fading in r band
  43. GRB 231118A: Swift-XRT position
  44. GRB 231118A: Skynet Optical Afterglow Discovery
  45. GRB 231117A: SOAR/Goodman imaging of the afterglow
  46. GRB 231118A: Swift detection of a burst
  47. GRB 231118A: Fermi GBM Final Real-time Localization
  48. GRB 231117A: Lowell Discovery Telescope Observations
  49. GRB 231117A: ePESSTO+ host galaxy redshift confirmation
  50. GRB 231117A: ATCA detection of a radio counterpart
  51. LIGO/Virgo/KAGRA S231118an: Identification of a GW compact binary merger candidate
  52. GRB 231117A: GRBAlpha detection
  53. LIGO/Virgo/KAGRA S231118ab: Identification of a GW compact binary merger candidate
  54. GRB 231117A: Keck spectroscopy of afterglow candidate
  55. GRB 231115A: Wendelstein Optical/Infrared Observations
  56. GRB 231115A: JinShan optical upper limits
  57. LIGO/Virgo/KAGRA S231118d: Identification of a GW compact binary merger candidate
  58. GRB 231117A: GIT optical follow-up
  59. GRB 231117A: LT observations consistent with fading
  60. GRB 231117A: Keck observations indicate presence of optical afterglow in z~0.3-0.5 galaxy
  61. GRB 231117A: REM optical and NIR early-time observations
  62. GRB231117A: AGILE/MCAL analysis
  63. GRB 231117A: AKO Optical Upper Limit
  64. GRB 231117A: afterglow candidate detection from Kinder observations with Lulin observatory
  65. Swift GRB 231117A: Global MASTER-Net observations report
  66. GRB 231117A (short): Glowbug gamma-ray detection
  67. GRB 231117A: ATLAS non-detection of an optical counterpart
  68. Konus-Wind detection of GRB 231117A (short/hard)
  69. GRB 231115A : OHP/T120 optical upper limit
  70. GRB 231115A: optical observations from INAF observatories
  71. GRB 231117A : MITSuME Akeno optical upper limits
  72. GRB 231117A: AGILE detection of a bright short burst
  73. GRB 231117A: Enhanced Swift-XRT position
  74. GRB 231117A: GOTO optical upper limits
  75. GRB 231117A: AstroSat CZTI detection of a bright short burst
  76. GRB 231117A: Swift detection of a bright short burst
  77. GRB 231115A: Non-detection of radio emission with CHIME/FRB
  78. GRB 231111A: Swift/UVOT Detection
  79. MAGIC observation of GRB 231115A, a possible magnetar giant flare
  80. GRB231115A: Liverpool Telescope imaging
  81. GRB 231115A: NuSTAR Follow-Up Observations
  82. GRB 231115A: Swift/BAT-GUANO detection of a short burst
  83. GRB 231115A: Swift-XRT and Swift-UVOT observations
  84. Fermi GRB 231116A: Global MASTER-Net observations report
  85. Konus-Wind detection of GRB 231115A (a probable Magnetar Giant Flare from M82)
  86. GRB 231115A: AGILE/MCAL upper limits
  87. GRB 231115A: Insight-HXMT/HE detection
  88. GRB 231115A: GBM/Fermi Observations of a probable Giant Flare of Magnetar
  89. GRB 231116A: Fermi GBM Final Real-time Localization
  90. GRB 231115A : MITSuME Akeno and Okayama optical upper limits
  91. GRB 231115A: Gaoyazi/GOT follow-up and archival observations
  92. GRB 231115A / AT2023xvj: Updated GIT analysis
  93. GRB 231115A: archival Chandra X-ray observations
  94. GRB 231115A: Upper limits from a neutrino search with IceCube
  95. GRB 231115A: Kinder observations with Lulin observatory
  96. GRB231115A: GRANDMA Observations
  97. GRB 231115A: GOTO pre-burst limits of AT2023xvj
  98. GRB 231115A: Non-detection in low-latency of gravitational waves with LIGO/Virgo/KAGRA
  99. GRB 231115A: pre-burst ZTF upper limits for GRB optical counterpart candidate
  100. GRB 231106A: TESS identification of candidate optical counterpart

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