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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. LIGO/Virgo/KAGRA S241009em: Identification of a GW compact binary merger candidate
  2. GRB 241009A : Detection of a long duration GRB by SVOM/ECLAIRs
  3. GRB 241008A: Fermi GBM Observation
  4. GRB 241008A: Fermi-LAT detection
  5. GRB 241002B: Swift-XRT afterglow detection
  6. LIGO/Virgo/KAGRA S241009an: Identification of a GW compact binary merger candidate
  7. GRB 241002A: NOT optical upper limits
  8. LIGO/Virgo/KAGRA S241009l: Identification of a GW compact binary merger candidate
  9. Fermi GRB 241008A: Global MASTER-Net observations report
  10. GRB 241008A: BALROG localization (Fermi Trigger 750117609 / GRB 241008917)
  11. GRB 241008A: Fermi GBM Final Real-time Localization
  12. IceCube-241006A: No candidates from the Zwicky Transient Facility
  13. GRB 241006A: GRANDMA optical upper limits
  14. EP240930a / GRB 240930B: CrAO ZTSH optical upper limit
  15. GRB 241002B: PRIME near-infrared detection in 3rd epoch
  16. Fermi-LAT Gamma-ray Observations of NuEm-240926A
  17. GRB 240910A: LBT optical observations
  18. EP trigger ID 01709065118: KAIT confirmation of the stellar flare
  19. GRB 241006A: Swift-XRT refined Analysis
  20. GRB 240821A: Host galaxy redshift from VLT/X-shooter
  21. GRB 241006A: PRIME near-infrared upper limits
  22. GRB 241006A: Swift/UVOT Upper Limits
  23. GRB 241006A: SVOM/VT follow-up and optical upper limit
  24. LIGO/Virgo/KAGRA S241007bw: Identification of a GW compact binary merger candidate
  25. IceCube Alert 241006.94: Global MASTER-Net observations report
  26. GRB 241001A: Swift-XRT afterglow detection
  27. GRB 241006A: Enhanced Swift-XRT position
  28. IceCube-241006A - IceCube observation of a high-energy neutrino candidate track-like event
  29. GRB 241006A: Swift detection of a burst
  30. Swift GRB241006.91: Global MASTER-Net observations report
  31. GRB 240930B: SVOM/C-GFT optical upper limit
  32. LIGO/Virgo/KAGRA S241006k: Identification of a GW compact binary merger candidate
  33. LIGO/Virgo/KAGRA S241005bo: Retraction of GW compact binary merger candidate
  34. Fermi trigger No 749721670: Global MASTER-Net observations report
  35. GRB 241004A: SVOM/GRM observation
  36. EP trigger ID 01709065118: the X-ray transient is likely a stellar flare event
  37. GRB 240930B / EP 240930a: SVOM/GRM observation
  38. GRB 241001A : ECLAIRs spectral analysis and XRF classification
  39. GRB 241002B: PRIME near-infrared detection in 2nd epoch
  40. GRB 241002B: Fermi GBM Observation
  41. Fermi trigger No 749735279: Global MASTER-Net observations report
  42. Fermi trigger No 749630753: Global MASTER-Net observations report
  43. Fermi trigger No 749693019: Global MASTER-Net observations report
  44. GRB 241002B: Swift-XRT observations
  45. GRB 241002C: SVOM/C-GFT optical upper limit
  46. GRB 241002A: Swift-BAT refined analysis
  47. GRB 241002B: Swift/BAT-GUANO localization skymap of a burst
  48. GRB 241002B: Swift ToO observations
  49. GRB 241002C: Swift-XRT observations confirm the source to be EI Eri
  50. Konus-Wind detection of GRB 240926A
  51. GRB 241002B: PRIME near-infrared detection
  52. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  53. GRB 241002C: Swift ToO observations
  54. Fermi-GBM Sub-Threshold Detection of GRB 241002D
  55. IPN triangulation of GRB 240930B / EP 240930a
  56. GRB 241001A : SVOM/VT optical detection
  57. GRB 241002B: GOTO24gpc/AT 2024xbg follow-up observations update
  58. GRB 241002D: SVOM/GRM observation
  59. GRB 241002B: ULL-ASTRO-MASTER LCOGT 0.4m + QHY600 detection of the GOTO optical counterpart candidate AT 2024xbg / GOTO24gpc
  60. GRB 240930B: CALET Gamma-Ray Burst Monitor detection
  61. GRB 241002C: X-ray afterglow candidate observed by SVOM/MXT
  62. GRB 240929A: SAO RAS, Mondy, and CrAO optical observations
  63. GRB 241002C : MITSuME Akeno optical upper limits
  64. LIGO/Virgo/KAGRA S240925n: Updated Sky localization
  65. NuEm-240926A: Upper limits from a search for coincident neutrino events in IceCube
  66. GRB241001A: REM optical/NIR upper limits
  67. LIGO/Virgo/KAGRA S241002e: Updated Sky localization
  68. GRB 241002A: Swift/UVOT Upper Limits
  69. EP240930a: Liverpool Telescope observations
  70. GRB 241002A: Swift-XRT refined Analysis
  71. GRB 241002A: LCOGT Optical Upper Limits
  72. GRB 241001A: GRANDMA and Kilonova-Catcher optical afterglow detection and upper limits
  73. GRB 241001A: Swift/UVOT Detection
  74. GRB 241001A: VLT/X-shooter redshift
  75. GRB 241002B: GOTO optical counterpart candidate
  76. EP trigger ID 01709064214: GOTO confirms detection as a flare star
  77. GRB 241002C : Detection of a long soft transient by SVOM/ECLAIRs
  78. GRB 241001A: correction to GCN 37667
  79. GRB 240929A: Liverpool Telescope prompt followup observations
  80. Fermi GRB 241002B: Global MASTER-Net observations report
  81. GRB 241001A: Swift-XRT observations
  82. EP trigger ID 01709064214: the X-ray transient is most likely a stellar flare event
  83. GRB 241002B: Fermi GBM Final Real-time Localization
  84. GRB241001A: optical afterglow candidate
  85. GRB 241002A: 1.5m OSN optical upper limit
  86. GRB 241002A: Enhanced Swift-XRT position
  87. GRB 241001A: BOOTES-6/DPRT optical upper limit
  88. LIGO/Virgo/KAGRA S241002e: Identification of a GW compact binary merger candidate
  89. GRB 241002A: Swift detection of a burst
  90. LIGO/Virgo/KAGRA S240930du: Updated Sky localization
  91. GRB 240930B: Fermi GBM Observation
  92. GRB 241001A: Swift ToO observations
  93. GRB 240930B: GRBAlpha detection
  94. GRB 240929A: GRBAlpha detection
  95. EP240930a : KAIT optical upper limit
  96. GRB 241001A : Detection of a soft transient by ECLAIRs onboard SVOM
  97. GRB 240930B: Swift/BAT-GUANO localization skymap of a burst
  98. EP240930a: EP-FXT follow-up observation update
  99. Fermi-LAT Gamma-ray Observations of IceCube-240929A
  100. EP240930a: GOTO optical upper limits

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