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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 241206A: Global MASTER-Net observations report
  2. GRB 241206A: Fermi GBM Final Real-time Localization
  3. EP241201a: 1.6m Mephisto Optical Upper Limits
  4. GRB 241204A: COLIBRÍ Optical Upper Limit
  5. EP241202b: KAIT optical upper limit
  6. LIGO/Virgo/KAGRA S241125n: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  7. GRB 241204A: DDOTI Upper Limits on the Afterglow
  8. GRB 241204A: Fermi GBM Observation
  9. Fermi GRB 241204A: Global MASTER-Net observations report
  10. GRB 241130A: CALET Gamma-Ray Burst Monitor detection
  11. GRB 241128A : RAPAS follow-up observations
  12. GRB 241201A: GRBAlpha detection
  13. GRB 241204A: Fermi-LAT detection
  14. EP241202b: Upper limits from Fermi-GBM Observations
  15. IceCube-241127A: No transient candidates from the Zwicky Transient Facility
  16. EP241202b: Kinder optical counterpart candidate
  17. Fermi-GBM Sub-Threshold Detection of GRB 241128A
  18. GRB 241113B : RAPAS follow-up observation
  19. EP241201a: EP-FXT follow-up observations
  20. Konus-Wind detection of GRB 241130A
  21. EP241202b: Global MASTER-Net observations report
  22. EP241201a: BOOTES-5 optical upper limit
  23. EP241202b: EP detection of a fast X-ray transient
  24. EP241201a: NOT optical observations
  25. IPN triangulation of GRB 241130A
  26. GRB 241130A: EIRSAT-1 GMOD Detection
  27. GRB 241128A: Swift/UVOT Upper Limits
  28. GRB 241130A: Fermi GBM Detection
  29. IceCube-241127A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 241129A: Swift/BAT-GUANO localization skymap of a burst
  31. EP241201a: Kinder optical counterpart candidate
  32. LIGO/Virgo/KAGRA S241102br: GRAWITA wide-field optical observations
  33. EP241201a: Global MASTER-Net observations report
  34. EP241201a: EP detection of a fast X-ray transient
  35. The EP-WXT trigger 01709126243 is not a real source
  36. GRB 241127B: detection of a long GRB by SVOM/ECLAIRs
  37. GRB241201B: Fermi GBM Final Localization
  38. GRB241201B: Fermi GBM Final Localization
  39. LIGO/Virgo/KAGRA S241201ac: Updated Sky localization
  40. EP241126a: SOAR observations of the optical counterpart
  41. Fermi GRB 241201A: Global MASTER-Net observations report
  42. GRB 241201A: BALROG localization (Fermi Trigger 754757764 / GRB 241201622)
  43. GRB 241130A: Fermi GBM Final Real-time Localization
  44. GRB 241130A: Fermi GBM Final Real-time Localization
  45. EP241126a: 1.6m Mephisto Optical Upper Limits
  46. GRB 241201A: Fermi GBM Final Real-time Localization
  47. LIGO/Virgo/KAGRA S241201ac: Identification of a GW compact binary merger candidate
  48. LIGO/Virgo/KAGRA S241130be: Updated Sky localization
  49. Fermi trigger No 754701230: Global MASTER-Net observations report
  50. IPN triangulation of GRB 241128B
  51. Konus-Wind detection of GRB 241114B
  52. LIGO/Virgo/KAGRA S241130n: Updated Sky localization
  53. LIGO/Virgo/KAGRA S241125n: GRANDMA Optical Upper Limits
  54. GRB 241128A: AbAO optical upper limit
  55. LIGO/Virgo/KAGRA S241127aj: Updated Sky localization
  56. LIGO/Virgo/KAGRA S241130be: Identification of a GW compact binary merger candidate
  57. LIGO/Virgo/KAGRA S241129aa: Updated Sky localization
  58. LIGO/Virgo/KAGRA S241130n: Identification of a GW compact binary merger candidate
  59. SVOM/GRM observation of a short burst from soft gamma repeater Kes 73
  60. GRB 241128C: SVOM/GRM observation
  61. GRB 241128B: SVOM/GRM observation
  62. GRB 241128A: Swift-BAT refined analysis
  63. GRB 241127A: Swift-BAT refined analysis
  64. EP241126a: NOT optical observations
  65. GRB 241127A: PRIME near-infrared detection
  66. GRB 241128A: Mondy optical observations
  67. GRB 241128A: GRANDMA and Kilonova-Catcher Optical Afterglow Detections and Upperlimits
  68. Swift-XRT observations of IceCube -241127A
  69. Swift GRB 241128A: Global MASTER-Net observations report
  70. Fermi-LAT gamma-ray observations of IceCube-241127A
  71. EP241126a: SVOM/VT observations
  72. LIGO/Virgo/KAGRA S241129aa: Identification of a GW compact binary merger candidate
  73. GRB 241128A: Swift-XRT refined Analysis
  74. GRB 241129A: Fermi GBM Final Real-time Localization
  75. GRB 241128A: Enhanced Swift-XRT position
  76. GRB 241128A: NOT optical observations
  77. GRB 241128A: LCO optical detection
  78. GRB 241128A: 1.5m OSN optical afterglow detection
  79. LIGO/Virgo S241127aj: GRANDMA/FRAM-CTA-N Observations
  80. Fermi trigger No 754492985: Global MASTER-Net observations report
  81. GRB 241128A: Swift-XRT afterglow detection
  82. GRB 241128A: Swift detection of a burst
  83. GRB 241127A: GRANDMA and Kilonova-Catcher optical afterglow detections
  84. GRB 241127A: Swift/UVOT Detection
  85. GRB 241127A: Swift-XRT refined Analysis
  86. GRB 241127A: SVOM/GRM observation
  87. GRB 241127A: Enhanced Swift-XRT position
  88. LIGO/Virgo/KAGRA S241127aj: Updated Sky localization
  89. The EP-WXT trigger 01709125191 is not a real source
  90. GRB 241127A: LCOGT (40-cm) optical counterpart detection
  91. Swift GRB241127.91: Global MASTER-Net OT detection
  92. EP241126a: WFST Observations
  93. LIGO/Virgo/KAGRA S241125n: Update on Coincidence False Alarm Method
  94. IceCube Alert 241127.59: Global MASTER-Net observations report
  95. GRB 241127A: Swift detection of a burst with an optical counterpart
  96. Swift GRB241127.91: Global MASTER-Net observations report
  97. Swift GRB241127.91: Global MASTER-Net OT detection
  98. LIGO/Virgo/KAGRA S241125n: Preliminary flux estimate and spectral analysis of the Swift/BAT-GUANO candidate counterpart
  99. LIGO/Virgo/KAGRA S241125n: Swift-UVOT Upper Limits
  100. IceCube-241127A: IceCube observation of a high-energy neutrino candidate track-like event

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