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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. GRB241120A: OHP/T193 optical observations
  2. GRB 241120A: CALET Gamma-Ray Burst Monitor detection
  3. EP241021a and EP241026b: Keck/LRIS spectroscopic observations
  4. EP trigger ID 01709065118: Keck/LRIS spectroscopic observations
  5. EP-WXT trigger 01709018832: Lick/Kast spectroscopy with the 3 m Shane telescope
  6. GRB 241120A: Mondy and AbAO optical observations
  7. EP241119a: Optical upper limits with Kinder observations
  8. EP trigger ID 01709122294: the X-ray transient is likely a stellar flare event
  9. EP241119a: GIT optical upper limits
  10. GRB 241113A: Possible ATCA Radio detection
  11. EP241119a : J-band observations with WINTER
  12. GRB 241120A: Fermi GBM Observation
  13. GRB 241114B: Insight-HXMT/HE detection
  14. Integral GRB241120.25: Global MASTER-Net observations report
  15. EP241119a: Global MASTER-Net observations report
  16. EP241119a: EP detection of a fast X-ray transient
  17. GRB241120A: a long GRB detected by INTEGRAL
  18. GRB 241120A: Fermi GBM Final Real-time Localization
  19. GRB 241115A: CALET Gamma-Ray Burst Monitor detection
  20. GRB 241112B: Mephisto further optical observations
  21. GRB 241119A: Fermi GBM Final Real-time Localization
  22. GRB 241030A: J-band observations
  23. GRB 241115a: PRIME near-infrared upper limits
  24. GRB 241117A: Swift/BAT-GUANO localization skymap of a burst
  25. LIGO/Virgo/KAGRA S241116cq: Upper limits from Swift/BAT-GUANO
  26. GRB 241115B: Fermi GBM Observation
  27. LIGO/Virgo/KAGRA S241114y: Updated Sky localization
  28. Fermi GRB 241118A: Global MASTER-Net observations report
  29. GRB 241118A: Fermi GBM Final Real-time Localization
  30. Updates to IceCube realtime alert system for muon tracks
  31. GRB 241117A: SVOM/GRM observation of a short burst with extended emission
  32. GRB 241117A: Fermi GBM Detection
  33. Fermi GRB 241117B: Global MASTER-Net observations report
  34. GRB 241117B: Fermi GBM Final Real-time Localization
  35. IceCube-Cascade 241116A: Upper limits from a search for additional neutrino events in IceCube
  36. LIGO/Virgo/KAGRA S241116cq: Updated Sky localization
  37. GRB 241115B: Swift/BAT-GUANO localization skymap of a long burst
  38. Fermi GRB 241117A: Global MASTER-Net observations report
  39. GRB 241117A: Fermi GBM Final Real-time Localization
  40. GRB 241115C: Fermi GBM Observation
  41. GRB 241115A: Swift-XRT afterglow detection
  42. LIGO/Virgo/KAGRA S241116cq: Identification of a GW compact binary merger candidate
  43. EP241115a/GRB 241115D: Optical upper limits with Kinder observations
  44. GRB 241115A: Mephisto upper limits
  45. GRB 241113B: Mephisto upper limits
  46. EP241115a/GRB 241115D: Swift/XRT follow-up observation
  47. GRB 241115D / EP 241115a: SVOM/GRM observation
  48. The EP-WXT trigger 01709120856 is likely a flaring star
  49. EP241113a: Swift XRT weak detection
  50. GRB 241115A: Fermi GBM Observation
  51. GRB 241115A: LCOGT Optical Upper Limits
  52. GRB 241115C: Swift/BAT-GUANO localization skymap of a burst
  53. Fermi GRB 241115B: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S241114bi: Updated Sky localization and EM Bright Classification
  55. EP241115a: Global MASTER-Net observations report
  56. GRB 241115B: Fermi GBM Final Real-time Localization
  57. LIGO/Virgo/KAGRA S241113p: Updated Sky localization
  58. EP241115a: EP detection of a fast X-ray transient
  59. EP241113a: No Detection in Fermi-GBM Observations
  60. Swift GRB 241115A: Global MASTER-Net observations report
  61. Fermi GRB 241115A: Global MASTER-Net observations report
  62. GRB 241115A: Swift detection of a burst
  63. GRB 241115A: Fermi GBM Final Real-time Localization
  64. EP 241113a: LBT possible optical counterpart
  65. GRB 241113B: KAIT Optical Afterglow Candidate
  66. LIGO/Virgo/KAGRA S241114bi: Upper limits from Fermi-GBM Observations
  67. LIGO/Virgo/KAGRA S241114bi: Coverage and upper limits from MAXI/GSC observations
  68. GRB 241113A: Swift-BAT refined analysis
  69. LIGO/Virgo/KAGRA S241114bi: Identification of a GW compact binary merger candidate
  70. GRB 241113A: PRIME near-infrared upper limits
  71. Fermi GRB 241114A: Global MASTER-Net observations report
  72. EP241113a: Global MASTER-Net observations report
  73. GRB 241114A: Fermi GBM Final Real-time Localization
  74. GRB 241113B: J-band upper limit from WINTER
  75. GRB 241113A: J-band observations with WINTER
  76. EP241113a : J-band observations with WINTER
  77. GRB 241030A: LCO optical observation
  78. GRB 241113B: Swift-XRT observations
  79. IceCube-241113A: Upper limits from a search for additional neutrino events in IceCube
  80. GRB 241113A: 1.6m Mephisto and 50cm array optical upper limits
  81. GRB 241113A: KAIT optical observations
  82. EP241113b: Global MASTER-Net observations report
  83. EP241113b/GRB 241113B: EP detection of GRB 241113B
  84. Fermi-LAT gamma-ray observations of IceCube-241113A
  85. GRB 241113B: SVOM/GRM observation
  86. EP241113a: EP on-board trigger and autonomous follow-up observation
  87. LIGO/Virgo/KAGRA S241114y: Identification of a GW compact binary merger candidate
  88. GRB 241113A: Swift-XRT refined Analysis
  89. EP241107a: SOAR upper limits
  90. GRB 241113A: Swift/UVOT Detection
  91. GRB 241113A: REM detection of the optical/NIR afterglow
  92. Konus-Wind detection of GRB 241107A (short/hard)
  93. LIGO/Virgo/KAGRA S241113p: Identification of a GW compact binary merger candidate
  94. Fermi Gamma-ray Burst Monitor trigger 753166198/241113201 is not a GRB
  95. GRB 241113B: Swift ToO observations
  96. GRB 241113A: LCO optical observations
  97. IceCube-241113A - IceCube observation of a high-energy neutrino candidate track-like event
  98. GRB 241112B: GMG Optical Upper Limit
  99. GRB 241113A: Enhanced Swift-XRT position
  100. GRB241113A: LCOGT (40-cm) optical counterpart detection

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