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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. Fermi GRB 241207B: Global MASTER-Net observations report
  2. GRB 241207B: Swift/BAT-GUANO localization skymap of a short burst
  3. Fermi Gamma-ray Burst Monitor trigger 755277791/241207641 is not a GRB
  4. GRB 241201A: AstroSat CZTI detection
  5. GRB 241206A: DDOTI Upper Limit on the Afterglow
  6. AT2024adec: X-ray Upper Limits from EP-FXT Observation
  7. AT2024adec: X-ray Upper Limits from EP-FXT Observation
  8. EP241206a: BOOTES Global Network optical limits
  9. GRB 241207C: MASTER optical observations
  10. Fermi trigger No 755225799: Global MASTER-Net observations report
  11. GRB 241207C: Tiled Swift observations
  12. GRB 241207C: MAXI/GSC detection
  13. GRB 241207B: Fermi GBM Final Real-time Localization
  14. Fermi trigger No 755277791: Global MASTER-Net observations report
  15. Fermi GRB 241207A: Global MASTER-Net observations report
  16. EP241206a: Global MASTER-Net observations report
  17. EP241206a: EP detection of a fast X-ray transient
  18. GRB 241206A: Fermi GBM observation
  19. GRB 241206C: SVOM/GRM observation of a likely short burst
  20. GRB 241207A: Fermi GBM Final Real-time Localization
  21. GRB 241206A: Swift/BAT-GUANO localization skymap of a burst
  22. GRB 241206B: SVOM/MXT observations: a probable flare from the QSO 1ES 1959+650
  23. GRB 241206B: GWAC-F50A optical upper limit
  24. GRB 241206B: SVOM/ECLAIRs detection of a long soft transient
  25. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift
  26. Fermi GRB 241206A: Global MASTER-Net observations report
  27. GRB 241206A: Fermi GBM Final Real-time Localization
  28. EP241201a: 1.6m Mephisto Optical Upper Limits
  29. GRB 241204A: COLIBRÍ Optical Upper Limit
  30. EP241202b: KAIT optical upper limit
  31. LIGO/Virgo/KAGRA S241125n: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  32. GRB 241204A: DDOTI Upper Limits on the Afterglow
  33. GRB 241204A: Fermi GBM Observation
  34. Fermi GRB 241204A: Global MASTER-Net observations report
  35. GRB 241130A: CALET Gamma-Ray Burst Monitor detection
  36. GRB 241128A : RAPAS follow-up observations
  37. GRB 241201A: GRBAlpha detection
  38. GRB 241204A: Fermi-LAT detection
  39. EP241202b: Upper limits from Fermi-GBM Observations
  40. IceCube-241127A: No transient candidates from the Zwicky Transient Facility
  41. EP241202b: Kinder optical counterpart candidate
  42. Fermi-GBM Sub-Threshold Detection of GRB 241128A
  43. GRB 241113B : RAPAS follow-up observation
  44. EP241201a: EP-FXT follow-up observations
  45. Konus-Wind detection of GRB 241130A
  46. EP241202b: Global MASTER-Net observations report
  47. EP241201a: BOOTES-5 optical upper limit
  48. EP241202b: EP detection of a fast X-ray transient
  49. EP241201a: NOT optical observations
  50. IPN triangulation of GRB 241130A
  51. GRB 241130A: EIRSAT-1 GMOD Detection
  52. GRB 241128A: Swift/UVOT Upper Limits
  53. GRB 241130A: Fermi GBM Detection
  54. IceCube-241127A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 241129A: Swift/BAT-GUANO localization skymap of a burst
  56. EP241201a: Kinder optical counterpart candidate
  57. LIGO/Virgo/KAGRA S241102br: GRAWITA wide-field optical observations
  58. EP241201a: Global MASTER-Net observations report
  59. EP241201a: EP detection of a fast X-ray transient
  60. The EP-WXT trigger 01709126243 is not a real source
  61. GRB 241127B: detection of a long GRB by SVOM/ECLAIRs
  62. GRB241201B: Fermi GBM Final Localization
  63. GRB241201B: Fermi GBM Final Localization
  64. LIGO/Virgo/KAGRA S241201ac: Updated Sky localization
  65. EP241126a: SOAR observations of the optical counterpart
  66. Fermi GRB 241201A: Global MASTER-Net observations report
  67. GRB 241201A: BALROG localization (Fermi Trigger 754757764 / GRB 241201622)
  68. GRB 241130A: Fermi GBM Final Real-time Localization
  69. GRB 241130A: Fermi GBM Final Real-time Localization
  70. EP241126a: 1.6m Mephisto Optical Upper Limits
  71. GRB 241201A: Fermi GBM Final Real-time Localization
  72. LIGO/Virgo/KAGRA S241201ac: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S241130be: Updated Sky localization
  74. Fermi trigger No 754701230: Global MASTER-Net observations report
  75. IPN triangulation of GRB 241128B
  76. Konus-Wind detection of GRB 241114B
  77. LIGO/Virgo/KAGRA S241130n: Updated Sky localization
  78. LIGO/Virgo/KAGRA S241125n: GRANDMA Optical Upper Limits
  79. GRB 241128A: AbAO optical upper limit
  80. LIGO/Virgo/KAGRA S241127aj: Updated Sky localization
  81. LIGO/Virgo/KAGRA S241130be: Identification of a GW compact binary merger candidate
  82. LIGO/Virgo/KAGRA S241129aa: Updated Sky localization
  83. LIGO/Virgo/KAGRA S241130n: Identification of a GW compact binary merger candidate
  84. SVOM/GRM observation of a short burst from soft gamma repeater Kes 73
  85. GRB 241128C: SVOM/GRM observation
  86. GRB 241128B: SVOM/GRM observation
  87. GRB 241128A: Swift-BAT refined analysis
  88. GRB 241127A: Swift-BAT refined analysis
  89. EP241126a: NOT optical observations
  90. GRB 241127A: PRIME near-infrared detection
  91. GRB 241128A: Mondy optical observations
  92. GRB 241128A: GRANDMA and Kilonova-Catcher Optical Afterglow Detections and Upperlimits
  93. Swift-XRT observations of IceCube -241127A
  94. Swift GRB 241128A: Global MASTER-Net observations report
  95. Fermi-LAT gamma-ray observations of IceCube-241127A
  96. EP241126a: SVOM/VT observations
  97. LIGO/Virgo/KAGRA S241129aa: Identification of a GW compact binary merger candidate
  98. GRB 241128A: Swift-XRT refined Analysis
  99. GRB 241129A: Fermi GBM Final Real-time Localization
  100. GRB 241128A: Enhanced Swift-XRT position

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