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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. EP240416a: Kinder optical counterpart candidate
  2. EP240416a: EP-WXT detection of a fast X-ray transient
  3. GRB 240414A: AbAO optical upprer limit
  4. GRB 240415A: Swift/UVOT Detection
  5. EP240413a: BOOTES-2/TELMA Optical Upper Limit
  6. GRB 240415A: Fermi GBM Observation
  7. GRB 240414A: GAD Observatory, La Spezia, Italy ,upper limit
  8. GRB 240415A: Earliest optical followup with the Kinder observations
  9. GRB 240414A: GMG observation
  10. EP 240414a: BOOTES-4/MET Optical Upper Limits
  11. EP240414a: EP-FXT follow-up observation
  12. GRB 240415A: Enhanced Swift-XRT position
  13. GRB 240415B: Swift ToO observations
  14. GRB 240415B: Swift/BAT-GUANO Correction
  15. GRB 240415B: Swift/BAT-GUANO arcminute localization of a short burst
  16. GRB 240415A: OHP/T193 optical observations
  17. GRB 240415A: optical afterglow detection from the INAF Asiago Observatory
  18. GRB 240415A: SAO RAS optical observations
  19. GRB 240415A: Mondy optical transient detection (photometry correction in GCN 36118 )
  20. GRB 240414A: Fermi GBM Observation
  21. Fermi GRB 240415A: Global MASTER-Net observations report
  22. GRB 240415A: Mondy optical transient detection
  23. GRB 240414A: Photometric observation from 2.2m CAHA
  24. IceCube-240412A: Upper limits from a search for additional neutrino events in IceCube
  25. GRB 240414A: Swift/UVOT Detection
  26. LXT 240402A/GRB 240402B: Swift follow-up observations
  27. GRB 240414A: Mondy optical observations
  28. GRB 240414B: Fermi GBM Final Real-time Localization
  29. GRB 240414A: AKO Optical Upper Limit
  30. X-ray transient EP 240414a - GTC spectroscopic observations
  31. GRB 240415A: Prompt Swift-XRT observations
  32. GRB 240415A: Swift detection of a burst
  33. GRB 240415A: Fermi GBM Final Real-time Localization
  34. EP240413a: Upper limits from GECAM-B Observation
  35. EP 240414a: NOT optical counterpart confirmation
  36. GRB 240414A: Swift-XRT refined Analysis
  37. GRB240414A : J-band upper limits from WINTER
  38. GRB 240414A: Enhanced Swift-XRT position
  39. GRB 240414A : OHP/T193 second epoch of optical follow-up and afterglow detection
  40. GRB 240414A: MarSEC Observatory, Vicenza, Italy, UPPER LIMIT
  41. LIGO/Virgo/KAGRA S240413p: No Counterparts in DDOTI/OAN Optical Observations
  42. EP240413A: GOTO optical upper limits
  43. GRB 240414A: Skynet Optical Afterglow Observations
  44. Fermi trigger No 734754044: Global MASTER-Net observations report
  45. Swift GRB 240414A: Global MASTER-Net observations report
  46. EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3
  47. IPN triangulation of GRB 240410A
  48. EP240413a: possible detection of the X-ray emission with EP-FXT after 14 hours
  49. EP240414a: EP-WXT detection of a fast X-ray transient
  50. IPN triangulation of GRB 240411A
  51. Fermi-LAT gamma-ray observations of IceCube-240412A
  52. GRB 240414A : MITSuME Akeno optical upper limits
  53. GRB 240414A: Redshift confirmation from GTC/OSIRIS+
  54. EP240413a: EP-WXT detection of a fast X-ray transient
  55. GRB 240414A : OHP/T193 redshift determination
  56. GRB 240414A : OHP/T193 optical counterpart detection
  57. GRB 240414A: Swift detection of a burst
  58. LIGO/Virgo/KAGRA S240413p: Updated Sky localization
  59. LIGO/Virgo/KAGRA S240413p: Global MASTER-Net observations report
  60. LIGO/Virgo/KAGRA S240413p: Zwicky Transient Facility observations
  61. EP240408a: GSP optical upper limit
  62. GRB 240411B: CrAO/ZTSh optical observations
  63. GRB 240411B: Kinder observations with Lulin observatory
  64. LIGO/Virgo/Kagra S240413p: NED Galaxies in the Localization Volume
  65. LIGO/Virgo/KAGRA S240413p: Identification of a GW compact binary merger candidate
  66. GRB 240411B: HiPERCAM/GTC observation
  67. IceCube Alert 240412.23: Global MASTER-Net observations report
  68. GRB 240411B: Swift-BAT refined analysis
  69. GRB 240411B: Swift-XRT refined Analysis
  70. IceCube-240412A - IceCube observation of a high-energy neutrino candidate track-like event
  71. GRB 240411B: 1.3m DFOT Optical observations
  72. GRB 240411A: GRBAlpha detection
  73. GRB 240411B: OHP/T193 optical observations
  74. GRB 240405A: Glowbug gamma-ray detection
  75. GRB 240411B: Enhanced Swift-XRT position
  76. GRB 240411B: LCO optical afterglow detection
  77. GRB 240411B: Swift detection of a burst
  78. GRB 240408B: GRBAlpha detection
  79. GRB 240411A: Fermi GBM Final Real-time Localization
  80. EP240408A: MASTER optical observations
  81. EP240408a: GROND detection of a candidate counterpart
  82. EP240408a: Upper limits from GECAM-B Observation
  83. EP240408a: Swift follow-up observation
  84. EP240408a: BOOTES-6/DPRT optical upper limit
  85. X-ray transient EP240315a: second epoch e-MERLIN radio observations
  86. GRB 240405A: GRBAlpha detection
  87. EP240408a: EP-WXT detection of a fast X-ray transient
  88. Swift Trigger 1220736: detection of 4U 1543-62.
  89. GRB 240408B: AstroSat CZTI detection
  90. IceCube-240327B: GRANDMA/Kilonova-Catcher observations of 4FGL J0555.9+0030 and optical upper limits
  91. Fermi GRB 240408A: Global MASTER-Net observations report
  92. GRB 240408A: Fermi GBM Final Real-time Localization
  93. GRB 240407A: BALROG localization (Fermi Trigger 734144396 / GRB 240407042)
  94. GRB 240402C: CALET Gamma-Ray Burst Monitor detection
  95. Fermi GRB 240407A: Global MASTER-Net observations report
  96. GRB 240407A: Fermi GBM Final Real-time Localization
  97. Fermi-LAT gamma-ray observations of IceCube-240327B
  98. Fermi-LAT gamma-ray observations of IceCube-240327A
  99. LXT 240402A/GRB 240402B: rest-frame energetics from Konus-Wind observation
  100. Fermi GRB 240405B: Global MASTER-Net observations report

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