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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 S230521k: MASTER new OT discovery
  2. GRB 230523B: Name correction from GCN Circular 33859
  3. GRB 230523A: Swift/BAT-GUANO detection of a short hard burst
  4. LIGO/Virgo/KAGRA S230521k: Additional candidates from Zwicky Transient Facility
  5. Fermi Gamma-ray Burst Monitor trigger 706536788/230523509 is not a GRB
  6. GRB 230523A: Fermi GBM Final Real-time Localization
  7. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230523A
  8. LIGO/Virgo S230522n: Global MASTER-Net observations report
  9. LIGO/Virgo S230522a: Global MASTER-Net observations report
  10. LIGO/Virgo/KAGRA S230522n: Upper limits from IceCube neutrino search
  11. LIGO/Virgo/KAGRA S230518h: Swift/UVOT Upper Limits for MeerLICHT candidates: AT2023ixg and AT2023iyb
  12. LIGO/Virgo/KAGRA S230522a: 2 counterpart neutrino candidates from IceCube neutrino searches
  13. LIGO/Virgo S230521k: Global MASTER-Net observations report
  14. LIGO/Virgo/KAGRA S230521k: Zwicky Transient Facility observations
  15. GRB 230518B: VZLUSAT-2 detection
  16. Fermi Gamma-ray Burst Monitor trigger 706338208/230521211 is not a GRB
  17. LIGO/Virgo S230520ae: Global MASTER-Net observations report
  18. Fermi trigger No 706328428: Global MASTER-Net observations report
  19. IPN triangulation of GRB 230518A (short)
  20. Fermi trigger No 706331483: Global MASTER-Net observations report
  21. Fermi trigger No 706317104: Global MASTER-Net observations report
  22. GRB 230520A: CALET Gamma-Ray Burst Monitor detection
  23. GRB 230521A: Fermi GBM Final Real-time Localization
  24. LIGO/Virgo/KAGRA S230520ae: Identification of a GW compact binary merger candidate: End-to-End Test
  25. GRB 230520B is not a GRB
  26. GRB 230520B: Fermi GBM Final Real-time Localization
  27. LIGO/Virgo/KAGRA S230520ae: Upper limits from IceCube neutrino search
  28. LIGO/Virgo/KAGRA S230518h: ATCA follow-up of candidate counterparts
  29. LIGO/Virgo/KAGRA S230518h: GECKO tiling observations with KMTNet
  30. LIGO/Virgo/KAGRA S230518h: Swift/UVOT Upper Limits for Swope candidates: SSS23a, SSS23b and SSS23c
  31. GRB 230520A: MAXI/GSC detection
  32. LIGO/Virgo/KAGRA S230518h: ATLAS observations of the skymap
  33. LIGO/Virgo/KAGRA S230518h: Swope Search and Candidate Counterpart Identification
  34. GRB 230518A: Fermi GBM Observation
  35. LIGO/Virgo/KAGRA S230518h: Upper limits from Konus-Wind observations
  36. LIGO/Virgo S230518h: AGILE/MCAL observations
  37. GRB 230518A: Swift/BAT-GUANO detection
  38. LIGO/Virgo S230518h: Swift XRT observations, 8 X-ray sources
  39. LIGO/Virgo/KAGRA S230518h: Coverage and upper limits from MAXI/GSC observations
  40. GRB 230518A: Fermi GBM Final Real-time Localization
  41. Fermi Gamma-ray Burst Monitor trigger 706068974/230518095 is not a GRB
  42. LIGO/Virgo/Kagra S230518h: NED Galaxies in the Localization Volume
  43. LIGO/Virgo/KAGRA S230518h: AstroSat CZTI non-detection and upper limits
  44. LIGO/Virgo/KAGRA S230518h: Upper limits from Fermi-GBM Observations
  45. LIGO/Virgo S230518h: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S230518h: Updated Sky localization and EM Bright Classification
  47. LIGO/Virgo S230518h: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  48. LIGO/Virgo S230518h: Upper limits from IceCube neutrino search
  49. LIGO/Virgo/KAGRA S230518h: Identification of a GW compact binary merger candidate
  50. GRB 230513A: Zwicky Transient Facility continuous observations of a Fermi Short GRB (Trigger 705709044)
  51. GRB 230510B: GRBAlpha detection
  52. Fermi trigger No 706014351: Global MASTER-Net observations report
  53. GRB 230517A: BALROG localization (Fermi Trigger 706014351 / GRB 230517462)
  54. Improved IPN triangulation of GRB 230512A
  55. GRB 230517A: Fermi GBM Final Real-time Localization
  56. GRB 230510B: Fermi GBM detection
  57. Fermi trigger No 705952199: Global MASTER-Net observations report
  58. GRB 230516A: Fermi GBM Final Real-time Localization
  59. IPN triangulation of GRB 230511D (short)
  60. IPN triangulation of GRB 230512A
  61. GRB 230513A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705709044)
  62. GRB 230512A: Nanshan/NEXT non-detection of GRB afterglow candidate
  63. GRB 230512A: Zwicky Transient Facility non-detection of GRB afterglow candidate
  64. GRB 230512A: Liverpool Telescope observations
  65. GRB 230512A: GIT non detection of afterglow candidate
  66. GRB 230512A: Kitab possible afterglow candidate
  67. GRB 230512A: GRBAlpha detection
  68. GRB 230510A: GRBAlpha detection
  69. GRB 230513A: Fermi GBM Final Real-time Localization
  70. Fermi trigger No 705565670: Global MASTER-Net observations report
  71. Fermi-LAT gamma-ray observations of IceCube-230511A
  72. GRB 230510A: OHP/T193 and OHP/T120 optical observations
  73. GRB 230512A: Swift-XRT observations
  74. IceCube-230511A: Upper limits from a search for additional neutrino events in IceCube
  75. IceCube-Cascade 230511A: Upper limits from a search for additional neutrino events in IceCube
  76. GRB 230512A: GIT optical follow-up ZTF candidates
  77. GRB 230512A: Fermi GBM detection
  78. GRB 230512A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705565670)
  79. GRB 230430A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 704533643)
  80. GRB 230511D: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705537623)
  81. GRB 230512A: Tiled Swift observations
  82. GRB 230512A: Fermi-LAT detection
  83. GRB 230512A: AstroSat CZTI detection
  84. GRB 230512A: Fermi GBM Final Localization
  85. GRB 230510A: GIT optical upper limits
  86. GRB 230510A: LCOGT Optical Upper Limit
  87. GRB 230511D: Fermi GBM Final Real-time Localization
  88. GRB 230510A: Swift/UVOT Observations
  89. IceCube-230511A: IceCube observation of a high-energy neutrino candidate
  90. GRB 230510B: AstroSat CZTI detection
  91. GRB 230511C: Fermi GBM Final Localization
  92. Fermi trigger No 705503315: Global MASTER-Net observations report
  93. GRB 230511B: Fermi GBM Final Real-time Localization
  94. Fermi trigger No 705496510: Global MASTER-Net observations report
  95. GRB 230511A: Fermi GBM Final Real-time Localization
  96. GRB 230510A: Fermi GBM detection
  97. Fermi trigger No 705446499: Global MASTER-Net observations report
  98. GRB 230510A: Gaoyazi/GOT optical upper limit
  99. GRB 230510B: CALET Gamma-Ray Burst Monitor detection
  100. GRB 230510A: CALET Gamma-Ray Burst Monitor detection

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