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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"

22063 results found.

  1. GRB 240421B: Swift/UVOT Upper Limits
  2. Fermi GRB 240421A: Global MASTER-Net observations report
  3. EP240420a: TNT upper limit to its optical counterpart
  4. EP240420a: Xinglong decaying optical counterpart
  5. EP240420a: Nanshan optical counterpart observations
  6. EP240420a: NOT optical counterpart candidate and potential host
  7. Fermi trigger No 735280430: Global MASTER-Net observations report
  8. GRB240418A - Candidate afterglow from NIRES
  9. IceCube Alert 240419.98: Global MASTER-Net observations report
  10. GRB 240419B: Swift/UVOT Upper Limits
  11. GRB 240419A: Swift/UVOT Upper Limits
  12. GRB 240419B: optical afterglow from the NOT
  13. EP240414a: Near-IR observations with NIRES and WINTER
  14. Swift GRB 240419B: Global MASTER-Net observations report
  15. Swift GRB 240419A: Global MASTER-Net observations report
  16. GRB 240418A: Swift/UVOT Upper Limits
  17. GRB 240419A: REM NIR afterglow detection
  18. GRB 240411B: Swift/UVOT Detection
  19. GRB 240419A: VLT/UVES redshift of z = 5.178
  20. GRB 240419A: VLT optical afterglow detection
  21. Fermi trigger No 735089036: Global MASTER-Net observations report
  22. EP240416a: J-band observations with WINTER
  23. GRB 240418A: TSHAO Zeiss-1000 optical upper limit
  24. GRB 240418A: NOT optical upper limits
  25. GRB 240411A: GOTO early optical upper limits
  26. Swift GRB240418.85: Global MASTER-Net observations report
  27. EP240417a: EP-WXT detection of a fast X-ray transient
  28. Fermi GRB 240417A: Global MASTER-Net observations report
  29. LIGO/Virgo/KAGRA S240413p: X-ray upper limits from EP-WXT for the candidate AGN counterpart
  30. EP240414a: GSP detects optical candidate counterpart AT2024gsa
  31. LIGO/Virgo/KAGRA S240413p: DECam GW-MMADS candidates
  32. EP240414a: Pan-STARRS detects re-brightening of the candidate counterpart AT2024gsa
  33. LIGO/Virgo/KAGRA S240413p: historical ATLAS and ZTF observations of the candidate AGN counterpart
  34. LIGO/Virgo/KAGRA S240413p: STEP - T80S Search and Candidate Counterpart Identification
  35. EP240416A: MASTER optical observations
  36. EP240416a: Kinder optical counterpart candidate
  37. EP240416a: EP-WXT detection of a fast X-ray transient
  38. GRB 240414A: AbAO optical upprer limit
  39. GRB 240415A: Swift/UVOT Detection
  40. GRB 240414A: GAD Observatory, La Spezia, Italy ,upper limit
  41. GRB 240415A: Earliest optical followup with the Kinder observations
  42. GRB 240415B: Swift ToO observations
  43. GRB 240415B: Swift/BAT-GUANO Correction
  44. GRB 240415B: Swift/BAT-GUANO arcminute localization of a short burst
  45. GRB 240415A: OHP/T193 optical observations
  46. GRB 240415A: optical afterglow detection from the INAF Asiago Observatory
  47. GRB 240415A: SAO RAS optical observations
  48. Fermi GRB 240415A: Global MASTER-Net observations report
  49. GRB 240415A: Mondy optical transient detection
  50. GRB 240414A: Photometric observation from 2.2m CAHA
  51. GRB 240414A: Swift/UVOT Detection
  52. LXT 240402A/GRB 240402B: Swift follow-up observations
  53. GRB 240414A: Mondy optical observations
  54. X-ray transient EP 240414a - GTC spectroscopic observations
  55. GRB 240415A: Prompt Swift-XRT observations
  56. EP 240414a: NOT optical counterpart confirmation
  57. GRB240414A : J-band upper limits from WINTER
  58. GRB 240414A : OHP/T193 second epoch of optical follow-up and afterglow detection
  59. GRB 240414A: MarSEC Observatory, Vicenza, Italy, UPPER LIMIT
  60. LIGO/Virgo/KAGRA S240413p: No Counterparts in DDOTI/OAN Optical Observations
  61. EP240413A: GOTO optical upper limits
  62. GRB 240414A: Skynet Optical Afterglow Observations
  63. Fermi trigger No 734754044: Global MASTER-Net observations report
  64. Swift GRB 240414A: Global MASTER-Net observations report
  65. EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3
  66. Fermi-LAT gamma-ray observations of IceCube-240412A
  67. GRB 240414A : OHP/T193 redshift determination
  68. GRB 240414A : OHP/T193 optical counterpart detection
  69. LIGO/Virgo/KAGRA S240413p: Global MASTER-Net observations report
  70. LIGO/Virgo/KAGRA S240413p: Zwicky Transient Facility observations
  71. EP240408a: GSP optical upper limit
  72. GRB 240411B: CrAO/ZTSh optical observations
  73. GRB 240411B: Kinder observations with Lulin observatory
  74. LIGO/Virgo/Kagra S240413p: NED Galaxies in the Localization Volume
  75. GRB 240411B: HiPERCAM/GTC observation
  76. IceCube Alert 240412.23: Global MASTER-Net observations report
  77. GRB 240411B: 1.3m DFOT Optical observations
  78. GRB 240411B: OHP/T193 optical observations
  79. GRB 240411B: LCO optical afterglow detection
  80. EP240408A: MASTER optical observations
  81. EP240408a: GROND detection of a candidate counterpart
  82. EP240408a: Swift follow-up observation
  83. X-ray transient EP240315a: second epoch e-MERLIN radio observations
  84. EP240408a: EP-WXT detection of a fast X-ray transient
  85. IceCube-240327B: GRANDMA/Kilonova-Catcher observations of 4FGL J0555.9+0030 and optical upper limits
  86. Fermi GRB 240408A: Global MASTER-Net observations report
  87. Fermi GRB 240407A: Global MASTER-Net observations report
  88. Fermi-LAT gamma-ray observations of IceCube-240327B
  89. Fermi-LAT gamma-ray observations of IceCube-240327A
  90. Fermi GRB 240405B: Global MASTER-Net observations report
  91. LXT 240402A/GRB 240402B: GECAM-C refined analysis
  92. Swift satellite resumes pointed science observations
  93. X-ray transient LXT 240402A: WFST optical upper limits​
  94. IceCube-240327B: GRANDMA observations of 4FGL J0555.9+0030
  95. GRB/FXT 240402B: VLT/FORS2 optical afterglow candidate
  96. LXT 240402A: EP-FXT detection of the X-ray afterglow
  97. Fermi GRB 240404A: Global MASTER-Net observations report
  98. LXT 240402A: MASTER optical observations with AGN in error-box
  99. X-ray transient LXT 240402A: LEIA detection
  100. Fermi trigger No 733808041: Global MASTER-Net observations report

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