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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: Lowell Discovery Telescope Observations
  2. GRB 231117A: ePESSTO+ host galaxy redshift confirmation
  3. GRB 231117A: ATCA detection of a radio counterpart
  4. LIGO/Virgo/KAGRA S231118an: Identification of a GW compact binary merger candidate
  5. GRB 231117A: GRBAlpha detection
  6. LIGO/Virgo/KAGRA S231118ab: Identification of a GW compact binary merger candidate
  7. GRB 231117A: Keck spectroscopy of afterglow candidate
  8. GRB 231115A: Wendelstein Optical/Infrared Observations
  9. GRB 231115A: JinShan optical upper limits
  10. LIGO/Virgo/KAGRA S231118d: Identification of a GW compact binary merger candidate
  11. GRB 231117A: GIT optical follow-up
  12. GRB 231117A: LT observations consistent with fading
  13. GRB 231117A: Keck observations indicate presence of optical afterglow in z~0.3-0.5 galaxy
  14. GRB 231117A: REM optical and NIR early-time observations
  15. GRB231117A: AGILE/MCAL analysis
  16. GRB 231117A: AKO Optical Upper Limit
  17. GRB 231117A: afterglow candidate detection from Kinder observations with Lulin observatory
  18. Swift GRB 231117A: Global MASTER-Net observations report
  19. GRB 231117A (short): Glowbug gamma-ray detection
  20. GRB 231117A: ATLAS non-detection of an optical counterpart
  21. Konus-Wind detection of GRB 231117A (short/hard)
  22. GRB 231115A : OHP/T120 optical upper limit
  23. GRB 231115A: optical observations from INAF observatories
  24. GRB 231117A : MITSuME Akeno optical upper limits
  25. GRB 231117A: AGILE detection of a bright short burst
  26. GRB 231117A: Enhanced Swift-XRT position
  27. GRB 231117A: GOTO optical upper limits
  28. GRB 231117A: AstroSat CZTI detection of a bright short burst
  29. GRB 231117A: Swift detection of a bright short burst
  30. GRB 231115A: Non-detection of radio emission with CHIME/FRB
  31. GRB 231111A: Swift/UVOT Detection
  32. MAGIC observation of GRB 231115A, a possible magnetar giant flare
  33. GRB231115A: Liverpool Telescope imaging
  34. GRB 231115A: NuSTAR Follow-Up Observations
  35. GRB 231115A: Swift/BAT-GUANO detection of a short burst
  36. GRB 231115A: Swift-XRT and Swift-UVOT observations
  37. Fermi GRB 231116A: Global MASTER-Net observations report
  38. Konus-Wind detection of GRB 231115A (a probable Magnetar Giant Flare from M82)
  39. GRB 231115A: AGILE/MCAL upper limits
  40. GRB 231115A: Insight-HXMT/HE detection
  41. GRB 231115A: GBM/Fermi Observations of a probable Giant Flare of Magnetar
  42. GRB 231116A: Fermi GBM Final Real-time Localization
  43. GRB 231115A : MITSuME Akeno and Okayama optical upper limits
  44. GRB 231115A: Gaoyazi/GOT follow-up and archival observations
  45. GRB 231115A / AT2023xvj: Updated GIT analysis
  46. GRB 231115A: archival Chandra X-ray observations
  47. GRB 231115A: Upper limits from a neutrino search with IceCube
  48. GRB 231115A: Kinder observations with Lulin observatory
  49. GRB231115A: GRANDMA Observations
  50. GRB 231115A: GOTO pre-burst limits of AT2023xvj
  51. GRB 231115A: Non-detection in low-latency of gravitational waves with LIGO/Virgo/KAGRA
  52. GRB 231115A: pre-burst ZTF upper limits for GRB optical counterpart candidate
  53. GRB 231106A: TESS identification of candidate optical counterpart
  54. GRB 231115A: MASTER optical observations
  55. GRB 231115A (short): Glowbug gamma-ray detection
  56. GRB 231115A: Fermi Observations of a probable Magnetar Giant Flare from M82
  57. GRB 231115A: archival HST observations
  58. Integral GRB231115.65: Global MASTER-Net observations report
  59. GRB 231115A: GROWTH-India discovery of a potential optical counterpart
  60. GRB 231115A: Swift ToO observations
  61. Fermi GRB 231115A: Global MASTER-Net observations report
  62. GRB 231115A: significance of INTEGRAL localization alignment with M82
  63. GRB 231115A: a short hard GRB detected by IBAS, poistionally coincident with M82
  64. GRB 231115A position consistent with M 82 galaxy
  65. GRB 231115A: Fermi GBM Final Real-time Localization
  66. LIGO/Virgo/KAGRA S231113bw: Updated Sky localization, EM Bright Classification, and Source Classification
  67. GRB 231111A: Swift-BAT refined analysis
  68. LIGO/Virgo/KAGRA S231113bw: Zwicky Transient Facility observations
  69. LIGO/Virgo/KAGRA S231114n: Updated Sky localization
  70. Fermi GRB 231114A: Global MASTER-Net observations report
  71. GRB 231113A (short): Glowbug gamma-ray detection
  72. GRB 231114A (short): Glowbug gamma-ray detection
  73. LIGO/Virgo/KAGRA S231113bw: GROWTH-India coverage and upper limits
  74. GECAM-B observation of a short burst from SGR J1555-5402
  75. GRB 231114A: Fermi GBM Final Localization
  76. LIGO/Virgo S231113bw: upper limits from AGILE/MCAL
  77. LIGO/Virgo/KAGRA S231114n: Identification of a GW compact binary merger candidate
  78. SGRJ1555-5402: Swift/BAT-GUANO arcminute localization of a SGR flare
  79. LIGO/Virgo/KAGRA S231113bw: Upper limits from Fermi-GBM Observations
  80. GRB 231110A: CALET Gamma-Ray Burst Monitor detection
  81. LIGO/Virgo/KAGRA S231113cd: Coverage and upper limits from MAXI/GSC observations
  82. LIGO/Virgo/KAGRA S231113bb: Updated Sky localization
  83. LIGO/Virgo/KAGRA S231113bw: Coverage and upper limits from MAXI/GSC observations
  84. LIGO/Virgo/KAGRA S231113bw: Identification of a GW compact binary merger candidate
  85. GRB 231110A: Swift-BAT refined analysis
  86. GRB231111A: MDM 2.4m Hiltner Telescope Observation
  87. GRB 231106A: Glowbug gamma-ray detection
  88. GRB 231111A: Xinglong-2.16m optical observations
  89. GRB 231110A: Swift-UVOT Upper Limits
  90. LIGO/Virgo/KAGRA S231113bb: Identification of a GW compact binary merger candidate
  91. GRB 231111A: Afterglow redshift from OSIRIS+/GTC
  92. GRB 231104A: VZLUSAT-2 detection
  93. GRB 231111A: TNG tentative redshift
  94. GRB 231110A: Glowbug gamma-ray detection
  95. GRB 231110A: AstroSat CZTI detection
  96. GRB 231111A NUTTelA-TAO / BSTI Early Measurements
  97. GRB 231111A: Leavitt Observatory optical observations
  98. GRB231111A: Optical follow-up observations with Mephisto
  99. GRB 231111A: GMG observation (correction)
  100. LIGO/Virgo/KAGRA S231112ag: Retraction of GW compact binary merger candidate

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