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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 250129A: OHP/T193 optical and spectroscopy observations
  2. GRB 250129A: Early afterglow detection by LCO.
  3. GRB 250128B: OHP/T193 optical upper limit
  4. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  5. GRB 250129A: LCO optical observations
  6. GRB 250129A: NOT optical observations and redshift confirmation
  7. GRB 250129A: GOTO optical observations show brightening afterglow
  8. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  9. Swift GRB 250129A: Global MASTER-Net observations report
  10. GRB 250128B: Enhanced Swift-XRT position
  11. The EP-WXT trigger 01709131085 is likely a flaring star
  12. Fermi GRB 250128B: Global MASTER-Net observations report
  13. GRB 250129A: Swift detection of a burst with an optical counterpart
  14. Swift GRB 250129A: Global MASTER-Net OT detection
  15. GRB 250128B: Swift-XRT refined Analysis
  16. GRB 250128B: Fermi GBM Observation
  17. GRB 250128B: GOTO optical upper limit
  18. Swift GRB 250128B: Global MASTER-Net observations report
  19. EP250125a: Upper limits from Swift/BAT-GUANO
  20. GRB 250128B: LCO optical observations
  21. GRB 250128B: Swift detection of a short burst
  22. GRB 250128B: Fermi GBM Final Real-time Localization
  23. GRB 250127A: Swift-XRT observations
  24. GRB 250127B: DDOTI Upper Limit on the Afterglow
  25. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  26. GRB 250127A: EP-FXT afterglow detection
  27. Fermi GRB 250128A: Global MASTER-Net observations report
  28. GRB 250128A: Fermi GBM Final Real-time Localization
  29. GRB 250117A: Fermi GBM Observation
  30. Fermi GRB 250127B: Global MASTER-Net observations report
  31. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  32. GRB 250127A: SVOM/VT upper limit
  33. GRB 250127B: Fermi GBM Final Real-time Localization
  34. IPN triangulation of GRB 250119C
  35. GRB 250127A: Swift ToO observations
  36. GRB 250127A: LCO optical upper limit
  37. GRB 241223A: cubesat Avion detection
  38. GRB 250127A: SVOM detection of a long burst
  39. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  40. EP250125A: Non-detection from Fermi-GBM Observations
  41. GRB 250126A: MAXI/GSC detection
  42. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  43. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  44. GRB 250126A: Fermi GBM Final Real-time Localization
  45. GECAM-A detection of a bright burst from SGR 1E1841-045
  46. GRB 250118A: Fermi GBM Observation
  47. EP250125a: Optical upper limit with Kinder observations
  48. EP250125a: REM optical counterpart detection
  49. GRB 250119C: Fermi GBM Observation
  50. EP250125a: Swift/XRT detection of a fading counterpart
  51. EP250125a: a new X-ray transient detected by Einstein Probe
  52. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  53. The EP-WXT trigger 01709130758 is a false trigger
  54. The EP-WXT trigger 01709130758 is a false trigger
  55. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  56. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  57. IPN triangulation of a bright burst from SGR 1E1841-045
  58. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  59. EP250108a: AbAO, CMO and Terskol optical upper limits
  60. Konus-Wind detection of GRB 250118B
  61. GRB 250121A: Fermi GBM Observation
  62. IPN triangulation of GRB 250118B
  63. Konus-Wind detection of GRB 250119B
  64. IPN triangulation of GRB 250119B
  65. GRB 250122A: Fermi GBM Final Real-time Localization
  66. Improved IPN triangulation of GRB 250107C
  67. GRB 250114A: Swift-BAT refined analysis
  68. GRB 250121A: INTEGRAL/SPI-ACS detection
  69. GRB 250121A: Fermi-LAT detection
  70. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  71. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  72. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  73. GRB 250121A: Fermi GBM Final Real-time Localization
  74. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  75. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  76. GRB 250119B: Fermi GBM Observation
  77. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  78. Konus-Wind detection of GRB 250117A
  79. IPN triangulation of GRB 250117A (short)
  80. ATCA detection of possible radio counterpart to GRB 250114A
  81. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  82. GRB 250119B: INTEGRAL/SPI-ACS detection
  83. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  84. EP 250108A: Late-time optical observation by LCO
  85. GRB 250117A: SVOM/GRM observation of a short burst
  86. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  87. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  88. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  89. GRB 250119C: Fermi GBM Final Real-time Localization
  90. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  91. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  92. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  93. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  94. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  95. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  96. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  97. GRB 250117A: GECAM observation of a short burst
  98. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  99. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  100. GRB 250119B: Fermi GBM Final Real-time Localization

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