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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 231118A: Continued Skynet Observations
  2. Swift GRB231118.72: Global MASTER-Net observations report
  3. GRB 231118A: Enhanced Swift-XRT position
  4. GRB 231117A: Kinder observations with Lulin observatory for AT 2023yba without fading in r band
  5. GRB 231118A: Swift-XRT position
  6. GRB 231118A: Skynet Optical Afterglow Discovery
  7. GRB 231117A: SOAR/Goodman imaging of the afterglow
  8. GRB 231118A: Swift detection of a burst
  9. GRB 231118A: Fermi GBM Final Real-time Localization
  10. GRB 231117A: Lowell Discovery Telescope Observations
  11. GRB 231117A: ePESSTO+ host galaxy redshift confirmation
  12. GRB 231117A: ATCA detection of a radio counterpart
  13. LIGO/Virgo/KAGRA S231118an: Identification of a GW compact binary merger candidate
  14. GRB 231117A: GRBAlpha detection
  15. LIGO/Virgo/KAGRA S231118ab: Identification of a GW compact binary merger candidate
  16. GRB 231117A: Keck spectroscopy of afterglow candidate
  17. GRB 231115A: Wendelstein Optical/Infrared Observations
  18. GRB 231115A: JinShan optical upper limits
  19. LIGO/Virgo/KAGRA S231118d: Identification of a GW compact binary merger candidate
  20. GRB 231117A: GIT optical follow-up
  21. GRB 231117A: LT observations consistent with fading
  22. GRB 231117A: Keck observations indicate presence of optical afterglow in z~0.3-0.5 galaxy
  23. GRB 231117A: REM optical and NIR early-time observations
  24. GRB231117A: AGILE/MCAL analysis
  25. GRB 231117A: AKO Optical Upper Limit
  26. GRB 231117A: afterglow candidate detection from Kinder observations with Lulin observatory
  27. Swift GRB 231117A: Global MASTER-Net observations report
  28. GRB 231117A (short): Glowbug gamma-ray detection
  29. GRB 231117A: ATLAS non-detection of an optical counterpart
  30. Konus-Wind detection of GRB 231117A (short/hard)
  31. GRB 231115A : OHP/T120 optical upper limit
  32. GRB 231115A: optical observations from INAF observatories
  33. GRB 231117A : MITSuME Akeno optical upper limits
  34. GRB 231117A: AGILE detection of a bright short burst
  35. GRB 231117A: Enhanced Swift-XRT position
  36. GRB 231117A: GOTO optical upper limits
  37. GRB 231117A: AstroSat CZTI detection of a bright short burst
  38. GRB 231117A: Swift detection of a bright short burst
  39. GRB 231115A: Non-detection of radio emission with CHIME/FRB
  40. GRB 231111A: Swift/UVOT Detection
  41. MAGIC observation of GRB 231115A, a possible magnetar giant flare
  42. GRB231115A: Liverpool Telescope imaging
  43. GRB 231115A: NuSTAR Follow-Up Observations
  44. GRB 231115A: Swift/BAT-GUANO detection of a short burst
  45. GRB 231115A: Swift-XRT and Swift-UVOT observations
  46. Fermi GRB 231116A: Global MASTER-Net observations report
  47. Konus-Wind detection of GRB 231115A (a probable Magnetar Giant Flare from M82)
  48. GRB 231115A: AGILE/MCAL upper limits
  49. GRB 231115A: Insight-HXMT/HE detection
  50. GRB 231115A: GBM/Fermi Observations of a probable Giant Flare of Magnetar
  51. GRB 231116A: Fermi GBM Final Real-time Localization
  52. GRB 231115A : MITSuME Akeno and Okayama optical upper limits
  53. GRB 231115A: Gaoyazi/GOT follow-up and archival observations
  54. GRB 231115A / AT2023xvj: Updated GIT analysis
  55. GRB 231115A: archival Chandra X-ray observations
  56. GRB 231115A: Upper limits from a neutrino search with IceCube
  57. GRB 231115A: Kinder observations with Lulin observatory
  58. GRB231115A: GRANDMA Observations
  59. GRB 231115A: GOTO pre-burst limits of AT2023xvj
  60. GRB 231115A: Non-detection in low-latency of gravitational waves with LIGO/Virgo/KAGRA
  61. GRB 231115A: pre-burst ZTF upper limits for GRB optical counterpart candidate
  62. GRB 231106A: TESS identification of candidate optical counterpart
  63. GRB 231115A: MASTER optical observations
  64. GRB 231115A (short): Glowbug gamma-ray detection
  65. GRB 231115A: Fermi Observations of a probable Magnetar Giant Flare from M82
  66. GRB 231115A: archival HST observations
  67. Integral GRB231115.65: Global MASTER-Net observations report
  68. GRB 231115A: GROWTH-India discovery of a potential optical counterpart
  69. GRB 231115A: Swift ToO observations
  70. Fermi GRB 231115A: Global MASTER-Net observations report
  71. GRB 231115A: significance of INTEGRAL localization alignment with M82
  72. GRB 231115A: a short hard GRB detected by IBAS, poistionally coincident with M82
  73. GRB 231115A position consistent with M 82 galaxy
  74. GRB 231115A: Fermi GBM Final Real-time Localization
  75. LIGO/Virgo/KAGRA S231113bw: Updated Sky localization, EM Bright Classification, and Source Classification
  76. GRB 231111A: Swift-BAT refined analysis
  77. LIGO/Virgo/KAGRA S231113bw: Zwicky Transient Facility observations
  78. LIGO/Virgo/KAGRA S231114n: Updated Sky localization
  79. Fermi GRB 231114A: Global MASTER-Net observations report
  80. GRB 231113A (short): Glowbug gamma-ray detection
  81. GRB 231114A (short): Glowbug gamma-ray detection
  82. LIGO/Virgo/KAGRA S231113bw: GROWTH-India coverage and upper limits
  83. GECAM-B observation of a short burst from SGR J1555-5402
  84. GRB 231114A: Fermi GBM Final Localization
  85. LIGO/Virgo S231113bw: upper limits from AGILE/MCAL
  86. LIGO/Virgo/KAGRA S231114n: Identification of a GW compact binary merger candidate
  87. SGRJ1555-5402: Swift/BAT-GUANO arcminute localization of a SGR flare
  88. LIGO/Virgo/KAGRA S231113bw: Upper limits from Fermi-GBM Observations
  89. GRB 231110A: CALET Gamma-Ray Burst Monitor detection
  90. LIGO/Virgo/KAGRA S231113cd: Coverage and upper limits from MAXI/GSC observations
  91. LIGO/Virgo/KAGRA S231113bb: Updated Sky localization
  92. LIGO/Virgo/KAGRA S231113bw: Coverage and upper limits from MAXI/GSC observations
  93. LIGO/Virgo/KAGRA S231113bw: Identification of a GW compact binary merger candidate
  94. GRB 231110A: Swift-BAT refined analysis
  95. GRB231111A: MDM 2.4m Hiltner Telescope Observation
  96. GRB 231106A: Glowbug gamma-ray detection
  97. GRB 231111A: Xinglong-2.16m optical observations
  98. GRB 231110A: Swift-UVOT Upper Limits
  99. LIGO/Virgo/KAGRA S231113bb: Identification of a GW compact binary merger candidate
  100. GRB 231111A: Afterglow redshift from OSIRIS+/GTC

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