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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"

8485 results found.

  1. GRB 241025A: Swift detection of a burst with an optical counterpart
  2. GRB 241001A: ATCA radio observations
  3. EP241021a: No Detection in Fermi-GBM Observation
  4. EP241021a: Optical counterpart observations with the Liverpool Telescope
  5. EP241021a: GSP detects optical candidate counterpart
  6. EP241021a: Optical upper limits with Kinder observations
  7. IceCube-Cascade 241019A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 241018A/sb24101802: Mephisto optical upper limit
  9. GRB 241018A: REM optical/NIR upper limits
  10. GRB 241018A: NOT optical observations
  11. GRB 241018A: SVOM/VT follow-up and optical candidate
  12. GRB 241018A: LCO/0.4m optical upper limits
  13. GRB 241018A: Swift ToO observations
  14. GRB 241018A: X-ray afterglow candidate observed by MXT
  15. GRB 241017A: Swift-XRT observations
  16. GRB 241017A: Swift ToO observations
  17. IceCube alert 139977_2910365 retraction
  18. GRB 240916A: radio detection with the VLA
  19. GRB241013A: REM observations
  20. LIGO/Virgo/KAGRA S241009em: Updated Sky localization
  21. LIGO/Virgo/KAGRA S241011k: Updated Sky localization
  22. LIGO/Virgo/KAGRA S241011k: NED Galaxies in the Localization Volume
  23. LIGO/Virgo/KAGRA S241011k: Identification of a GW compact binary merger candidate
  24. GRB 241009A: GRANDMA optical upper limits
  25. LIGO/Virgo/KAGRA S241007bw: Updated Sky localization
  26. LIGO/Virgo/KAGRA S241009an: Updated Sky localization
  27. IceCube-241006A: Upper limits from a search for additional neutrino events in IceCube
  28. GRB 241010A: Swift detection of a burst with an optical counterpart
  29. GRB 241009A: Swift ToO observations
  30. LIGO/Virgo/KAGRA S241009l: Updated Sky localization
  31. LIGO/Virgo/KAGRA S241009em: Identification of a GW compact binary merger candidate
  32. GRB 241002B: Swift-XRT afterglow detection
  33. LIGO/Virgo/KAGRA S241009an: Identification of a GW compact binary merger candidate
  34. GRB 241002A: NOT optical upper limits
  35. LIGO/Virgo/KAGRA S241009l: Identification of a GW compact binary merger candidate
  36. LIGO/Virgo/KAGRA S241007bw: Identification of a GW compact binary merger candidate
  37. IceCube-241006A - IceCube observation of a high-energy neutrino candidate track-like event
  38. GRB 241006A: Swift detection of a burst
  39. LIGO/Virgo/KAGRA S241006k: Identification of a GW compact binary merger candidate
  40. LIGO/Virgo/KAGRA S241005bo: Retraction of GW compact binary merger candidate
  41. GRB 241002B: Swift-XRT observations
  42. GRB 241002B: Swift ToO observations
  43. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  44. GRB 241002C: Swift ToO observations
  45. Fermi-GBM Sub-Threshold Detection of GRB 241002D
  46. GRB 241002B: GOTO24gpc/AT 2024xbg follow-up observations update
  47. GRB 241002B: ULL-ASTRO-MASTER LCOGT 0.4m + QHY600 detection of the GOTO optical counterpart candidate AT 2024xbg / GOTO24gpc
  48. GRB 241002C: X-ray afterglow candidate observed by SVOM/MXT
  49. LIGO/Virgo/KAGRA S240925n: Updated Sky localization
  50. NuEm-240926A: Upper limits from a search for coincident neutrino events in IceCube
  51. LIGO/Virgo/KAGRA S241002e: Updated Sky localization
  52. GRB 241001A: GRANDMA and Kilonova-Catcher optical afterglow detection and upper limits
  53. GRB 241001A: Swift/UVOT Detection
  54. GRB 241002B: GOTO optical counterpart candidate
  55. GRB 241002C : Detection of a long soft transient by SVOM/ECLAIRs
  56. GRB 241001A: correction to GCN 37667
  57. GRB 241001A: Swift-XRT observations
  58. GRB241001A: optical afterglow candidate
  59. LIGO/Virgo/KAGRA S241002e: Identification of a GW compact binary merger candidate
  60. GRB 241002A: Swift detection of a burst
  61. LIGO/Virgo/KAGRA S240930du: Updated Sky localization
  62. GRB 241001A: Swift ToO observations
  63. EP240930a : KAIT optical upper limit
  64. GRB 241001A : Detection of a soft transient by ECLAIRs onboard SVOM
  65. EP240930a: GOTO optical upper limits
  66. LIGO/Virgo/KAGRA S240930du: Identification of a GW compact binary merger candidate
  67. IceCube-240929A: Upper limits from a search for additional neutrino events in IceCube
  68. LIGO/Virgo/KAGRA S240930df: 1 counterpart neutrino candidate event from an IceCube neutrino search
  69. LIGO/Virgo/KAGRA S240930aa: Identification of a GW compact binary merger candidate
  70. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  71. LIGO/Virgo/KAGRA S240921cw: Upper limits from Swift/BAT-GUANO
  72. LIGO/Virgo/KAGRA S240920dw: Upper limits from Swift/BAT-GUANO
  73. LIGO/Virgo/KAGRA S240919bn: Upper limits from Swift/BAT-GUANO
  74. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  75. LIGO/Virgo/KAGRA S240925n: Updated Sky localization and Source Classification
  76. LIGO/Virgo/KAGRA S240925n: Identification of a GW compact binary merger candidate
  77. LIGO/Virgo/KAGRA S240922df: Updated Sky localization
  78. LIGO/Virgo/KAGRA S240920dw: Updated Sky localization
  79. LIGO/Virgo/KAGRA S240921cw: Updated Sky localization
  80. LIGO/Virgo/KAGRA S240924a: Updated Sky localization
  81. LIGO/Virgo/KAGRA S240920bz: Updated Sky localization and Source Classification
  82. LIGO/Virgo/KAGRA S240923ct: Updated Sky localization and Source Classification
  83. LIGO/Virgo/KAGRA S240924a: Identification of a GW compact binary merger candidate
  84. LIGO/Virgo/KAGRA S240923ct: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo S240919bn: GOTO optical upper limits
  86. LIGO/Virgo/KAGRA S240922df: Identification of a GW compact binary merger candidate
  87. LIGO/Virgo/KAGRA S240921cw: Identification of a GW compact binary merger candidate
  88. Fermi GBM Sub-Threshold Detection of GRB240919A / EP240919a
  89. EP240919a / GRB 240919A: KAIT optical upper limit
  90. GRB 240414A: further radio observations with the VLA
  91. LIGO/Virgo/KAGRA S240920dw: Identification of a GW compact binary merger candidate
  92. GRB 240910A: radio detection with the VLA
  93. EP240919a: NOT and Gemini optical observations
  94. EP240919a: GOTO optical upper limits
  95. LIGO/Virgo/KAGRA S240920bz: Identification of a GW compact binary merger candidate
  96. LIGO/Virgo/KAGRA S240919bn: Updated Sky localization
  97. GRB 240918B: Fermi GBM Detection
  98. LIGO/Virgo/KAGRA S240917cb: Updated Sky localization and EM Bright Classification
  99. LIGO/Virgo/KAGRA S240916ar: Updated Sky localization and EM Bright Classification
  100. LIGO/Virgo/KAGRA S240919bn: Identification of a GW compact binary merger candidate

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