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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 241105A: VLT/FORS2 spectroscopic redshift z = 2.681
  2. GRB 241104A: Swift-XRT observations
  3. GRB 240511A: LCO upper limits
  4. GRB 241104A: Fermi GBM Observation
  5. GRB 241104A: The SVOM/VT candidate in GCN circular 38086 is not an astrophysical source
  6. GRB 241105A: Swift ToO observations
  7. GRB 241105A: Swift/BAT-GUANO arcminute localization of a short burst
  8. GRB 241104A: Swift ToO observations
  9. GRB 241104A: NOT optical non-detection
  10. GRB 241105A: GOTO tentative optical counterpart candidate
  11. Fermi GRB 241105A: Global MASTER-Net observations report
  12. GRB 241104A: SVOM/VT optical candidate
  13. GRB 241105A: Fermi GBM Final Real-time Localization
  14. GRB 241104A/EP241104a: Optical upper limits with Kinder observations
  15. GRB 241104A: COLIBRÍ Upper Limits on the Optical Counterpart
  16. GRB 241104A: SVOM/GRM observation
  17. EP241104a: EP detection of GRB 241104A X-ray emission
  18. GRB 241010A: host galaxy redshift z = 0.977
  19. EP241101a NUTTelA-TAO / BSTI Measurements 2024-11-02
  20. GRB 241104A : Detection and localization by SVOM/ECLAIRs
  21. GRB 240821A: further radio observations with the VLA
  22. Fermi GRB 241104A: Global MASTER-Net observations report
  23. GRB 241104A: Fermi GBM Final Real-time Localization
  24. GRB 241030A: GRBAlpha detection
  25. EP241101a: EP-FXT observations update
  26. EP241103a: GIT optical upper limit
  27. EP241021a: OHP/T193 further optical observations
  28. LIGO/Virgo/KAGRA S241104a: Retraction of GW compact binary merger candidate
  29. Fermi trigger No 752365806: Global MASTER-Net observations report
  30. LIGO/Virgo/KAGRA S241102br: OHP/T193 optical observations
  31. LIGO/Virgo/KAGRA S241102cy: Updated Sky localization
  32. EP241103a: GOTO optical upper limit
  33. LIGO/Virgo/KAGRA S241102br: Updated Sky localization
  34. EP241101a: Possible detection of an optical counterpart with FTW
  35. EP241103a: Swift XRT detection and improved X-ray position
  36. EP241021a: continued SOAR observations
  37. EP241101a: Optical upper limits with Kinder observations
  38. EP241101a: OHP/T193 optical observations
  39. EP241103a: Gemini optical limits
  40. EP241103a: EP observation update
  41. LIGO/Virgo/KAGRA S241102br: MASTER observations and OT detection
  42. LIGO/Virgo/KAGRA S241102br: EP-WXT X-ray follow-up and flux limits
  43. GRB 241030A: Swift-UVOT observations of the optical prompt flare
  44. EP241103a: GSP optical upper limit
  45. EP241103A: LCO optical observations
  46. EP241103a: Global MASTER-Net observations report
  47. EP241103a: an X-ray transient detected by Einstein Probe
  48. GRB 241030A: Rapid release of TESS data.
  49. EP241101a: Global MASTER-Net observations report
  50. GRB 241029A: GRBAlpha detection
  51. EP241101a: BOOTES-7 optical upper limit
  52. LIGO/Virgo/KAGRA S241101ee: Updated Sky localization
  53. S241102cy: Identification of a GW compact binary merger candidate
  54. LIGO/Virgo/KAGRA S241102br: NED Galaxies in the Localization Volume
  55. LIGO/Virgo/KAGRA S241102br: Identification of a GW compact binary merger candidate
  56. Kinder optical follow-up observations of EP241021a, EP241026b, and EP241030a/GRB241030A
  57. GRB241030A: OHP/T193 optical observations
  58. EP241030a: Futher EP-FXT observation of the X-ray Afterglow of GRB 241030A
  59. EP241101a: EP-WXT detection of a fast X-ray transient
  60. Swift GRB 241101A: Global MASTER-Net observations report
  61. GRB 241101A: FRAM-ORM optical limit
  62. LIGO/Virgo/KAGRA S241101ee: Identification of a GW compact binary merger candidate
  63. GRB 241030A/EP241030a: TNOT observations of the optical counterpart
  64. EP241021a: Upper limit from Konus-Wind observations
  65. GRB 241101A: Swift-BAT refined analysis
  66. GRB 241030A: further SAO RAS optical observations
  67. GRB 241030A: Optical Observations via Virtual Telescope Project
  68. EP241021a: Liverpool Telescope optical follow-up observations
  69. GRB 241030B: Swift-XRT refined Analysis
  70. GRB 241026A: SAO RAS optical observations
  71. GRB 241030A / EP241030a: GMG possible spectroscopic redshift at z ~ 1.4
  72. EP241030a: EP/FXT observation of GRB 241030A X-ray Afterglow
  73. GRB 241101A: Swift detection of a burst
  74. GRB 241030B: NUTTelA-TAO / BSTI Optical Limits (duplicate submission of 38023)
  75. GRB 241030B: NUTTelA-TAO / BSTI Optical Limits
  76. EP241021a: OHP/T193 optical observations
  77. GRB 241030A: Palomar 1-m telescope COSMOS optical observations
  78. GRB 241030B: Montarrenti Observatory optical upper limit
  79. GRB 241030A / EP241030a: FTW Optical and NIR observations of the optical counterpart
  80. EP241026b: Liverpool Telescope optical follow-up
  81. Fermi trigger No 752083996: Global MASTER-Net observations report
  82. GRB 241030A: SAO RAS optical observations
  83. GRB 241030A: Fermi GBM Observation
  84. EP241021a: AMI-LA radio detection
  85. GRB 241030B : GIT optical upper limits
  86. GRB 241030B: LCOGT Optical Upper Limits
  87. GRB 241030B: Swift-BAT refined analysis
  88. GRB 241030A: Swift-BAT refined analysis
  89. GRB 241029A: COLIBRI Detection of the Optical Counterpart
  90. GRB 241030B: Swift/UVOT Detection
  91. EP EP241030a: Global MASTER-Net observations report
  92. GRB 241029A: LCO optical detection
  93. Fermi trigger No 752006065: Global MASTER-Net observations report
  94. GRB 241030B: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.82
  95. Swift GRB241030.77: Global MASTER-Net observations report
  96. GRB 241030B: SVOM/GRM observation
  97. GRB 241030B : MITSuME Akeno optical upper limits
  98. GRB 241030A: COLIBRI Continuing Detection of the Afterglow
  99. GRB 241030B: SVOM/VT optical afterglow observations
  100. GRB 241030B: COLIBRÍ Upper Limits on the Optical Counterpart

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