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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 241207A: Fermi GBM Final Real-time Localization
  2. GRB 241206A: Swift/BAT-GUANO localization skymap of a burst
  3. GRB 241206B: SVOM/MXT observations: a probable flare from the QSO 1ES 1959+650
  4. GRB 241206B: GWAC-F50A optical upper limit
  5. GRB 241206B: SVOM/ECLAIRs detection of a long soft transient
  6. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift
  7. Fermi GRB 241206A: Global MASTER-Net observations report
  8. GRB 241206A: Fermi GBM Final Real-time Localization
  9. EP241201a: 1.6m Mephisto Optical Upper Limits
  10. GRB 241204A: COLIBRÍ Optical Upper Limit
  11. EP241202b: KAIT optical upper limit
  12. LIGO/Virgo/KAGRA S241125n: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  13. GRB 241204A: DDOTI Upper Limits on the Afterglow
  14. GRB 241204A: Fermi GBM Observation
  15. Fermi GRB 241204A: Global MASTER-Net observations report
  16. GRB 241130A: CALET Gamma-Ray Burst Monitor detection
  17. GRB 241128A : RAPAS follow-up observations
  18. GRB 241201A: GRBAlpha detection
  19. GRB 241204A: Fermi-LAT detection
  20. EP241202b: Upper limits from Fermi-GBM Observations
  21. IceCube-241127A: No transient candidates from the Zwicky Transient Facility
  22. EP241202b: Kinder optical counterpart candidate
  23. Fermi-GBM Sub-Threshold Detection of GRB 241128A
  24. GRB 241113B : RAPAS follow-up observation
  25. EP241201a: EP-FXT follow-up observations
  26. Konus-Wind detection of GRB 241130A
  27. EP241202b: Global MASTER-Net observations report
  28. EP241201a: BOOTES-5 optical upper limit
  29. EP241202b: EP detection of a fast X-ray transient
  30. EP241201a: NOT optical observations
  31. IPN triangulation of GRB 241130A
  32. GRB 241130A: EIRSAT-1 GMOD Detection
  33. GRB 241128A: Swift/UVOT Upper Limits
  34. GRB 241130A: Fermi GBM Detection
  35. IceCube-241127A: Upper limits from a search for additional neutrino events in IceCube
  36. GRB 241129A: Swift/BAT-GUANO localization skymap of a burst
  37. EP241201a: Kinder optical counterpart candidate
  38. LIGO/Virgo/KAGRA S241102br: GRAWITA wide-field optical observations
  39. EP241201a: Global MASTER-Net observations report
  40. EP241201a: EP detection of a fast X-ray transient
  41. The EP-WXT trigger 01709126243 is not a real source
  42. GRB 241127B: detection of a long GRB by SVOM/ECLAIRs
  43. GRB241201B: Fermi GBM Final Localization
  44. GRB241201B: Fermi GBM Final Localization
  45. LIGO/Virgo/KAGRA S241201ac: Updated Sky localization
  46. EP241126a: SOAR observations of the optical counterpart
  47. Fermi GRB 241201A: Global MASTER-Net observations report
  48. GRB 241201A: BALROG localization (Fermi Trigger 754757764 / GRB 241201622)
  49. GRB 241130A: Fermi GBM Final Real-time Localization
  50. GRB 241130A: Fermi GBM Final Real-time Localization
  51. EP241126a: 1.6m Mephisto Optical Upper Limits
  52. GRB 241201A: Fermi GBM Final Real-time Localization
  53. LIGO/Virgo/KAGRA S241201ac: Identification of a GW compact binary merger candidate
  54. LIGO/Virgo/KAGRA S241130be: Updated Sky localization
  55. Fermi trigger No 754701230: Global MASTER-Net observations report
  56. IPN triangulation of GRB 241128B
  57. Konus-Wind detection of GRB 241114B
  58. LIGO/Virgo/KAGRA S241130n: Updated Sky localization
  59. LIGO/Virgo/KAGRA S241125n: GRANDMA Optical Upper Limits
  60. GRB 241128A: AbAO optical upper limit
  61. LIGO/Virgo/KAGRA S241127aj: Updated Sky localization
  62. LIGO/Virgo/KAGRA S241130be: Identification of a GW compact binary merger candidate
  63. LIGO/Virgo/KAGRA S241129aa: Updated Sky localization
  64. LIGO/Virgo/KAGRA S241130n: Identification of a GW compact binary merger candidate
  65. SVOM/GRM observation of a short burst from soft gamma repeater Kes 73
  66. GRB 241128C: SVOM/GRM observation
  67. GRB 241128B: SVOM/GRM observation
  68. GRB 241128A: Swift-BAT refined analysis
  69. GRB 241127A: Swift-BAT refined analysis
  70. EP241126a: NOT optical observations
  71. GRB 241127A: PRIME near-infrared detection
  72. GRB 241128A: Mondy optical observations
  73. GRB 241128A: GRANDMA and Kilonova-Catcher Optical Afterglow Detections and Upperlimits
  74. Swift-XRT observations of IceCube -241127A
  75. Swift GRB 241128A: Global MASTER-Net observations report
  76. Fermi-LAT gamma-ray observations of IceCube-241127A
  77. EP241126a: SVOM/VT observations
  78. LIGO/Virgo/KAGRA S241129aa: Identification of a GW compact binary merger candidate
  79. GRB 241128A: Swift-XRT refined Analysis
  80. GRB 241129A: Fermi GBM Final Real-time Localization
  81. GRB 241128A: Enhanced Swift-XRT position
  82. GRB 241128A: NOT optical observations
  83. GRB 241128A: LCO optical detection
  84. GRB 241128A: 1.5m OSN optical afterglow detection
  85. LIGO/Virgo S241127aj: GRANDMA/FRAM-CTA-N Observations
  86. Fermi trigger No 754492985: Global MASTER-Net observations report
  87. GRB 241128A: Swift-XRT afterglow detection
  88. GRB 241128A: Swift detection of a burst
  89. GRB 241127A: GRANDMA and Kilonova-Catcher optical afterglow detections
  90. GRB 241127A: Swift/UVOT Detection
  91. GRB 241127A: Swift-XRT refined Analysis
  92. GRB 241127A: SVOM/GRM observation
  93. GRB 241127A: Enhanced Swift-XRT position
  94. LIGO/Virgo/KAGRA S241127aj: Updated Sky localization
  95. The EP-WXT trigger 01709125191 is not a real source
  96. GRB 241127A: LCOGT (40-cm) optical counterpart detection
  97. Swift GRB241127.91: Global MASTER-Net OT detection
  98. EP241126a: WFST Observations
  99. LIGO/Virgo/KAGRA S241125n: Update on Coincidence False Alarm Method
  100. IceCube Alert 241127.59: Global MASTER-Net observations report

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