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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"

32508 results found.

  1. GRB 250108A: Swift ToO observations
  2. GRB 250107A: Fermi GBM Observation
  3. GRB 241228B: Fermi-LAT detection
  4. Fermi GRB 250107B: Global MASTER-Net observations report
  5. GRB 250107A: Swift ToO observations
  6. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  7. GRB 250106A: SVOM/VT 2nd optical deep observation
  8. GRB 250101A: J band upper limit by SYSU 80cm telescope
  9. GRB 250106A: NOT optical observations
  10. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  11. GRB 250103B: REM optical/NIR upper limits
  12. GRB 250101A: REM optical/NIR counterpart detection
  13. GRB 250106A: Swift-XRT observations
  14. GRB 250106A: SVOM/VT optical candidate
  15. GRB 250106A: Swift ToO observations
  16. GRB 241229A: SVOM/VT optical upperlimit
  17. GRB 250103B: LCO/1m optical afterglow candidate detection
  18. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  19. GRB 250103A: Swift-XRT observations
  20. GRB 250101A: 1.3m DFOT optical afterglow detection
  21. GRB 241229A: 1.3m DFOT upper limit
  22. GRB 241228B: 1.3m DFOT Optical observations
  23. GRB 241228A: 1.3m DFOT upper limit
  24. GRB 250103A: NOT spectroscopic redshift
  25. GRB 250103B:SVOM/VT optical counterpart
  26. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  27. GRB 250103A: Montarrenti Observatory optical detection
  28. GRB 250101A: further LCOGT optical afterglow observations
  29. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  30. GRB 250103A: NOT optical observations
  31. GRB 250103A: TSHAO optical upper limit
  32. GRB 250103A: Fermi GBM Observation
  33. GRB 250103B: LCOGT Optical Upper Limit
  34. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  35. Swift GRB 250103B: Global MASTER-Net observations report
  36. GRB 250103A: SVOM/VT optical counterpart confirmation
  37. EP250101a: Liverpool Telescope optical upper limit
  38. GRB 250103A: Swift ToO observations
  39. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  40. GRB 250101a: Liverpool Telescope optical follow-up
  41. GRB 250103B: SVOM detection of a long burst
  42. GRB 250103A: Xinglong 2.16m Optical Candidate
  43. Fermi GRB 250102A: Global MASTER-Net observations report
  44. GRB 250101B: SVOM/GRM observation
  45. GRB 250103A: GOTO optical upper limit
  46. GRB 250103A: SVOM/C-GFT optical upper limit
  47. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  48. EP241231b: optical upper limit with the Liverpool Telescope
  49. EP250101a: Xinglong optical upper limit
  50. GRB 250101A: Swift-BAT refined analysis
  51. GRB 250101A: further SAO RAS optical observations
  52. GRB 250101A: LCO optical counterpart detection
  53. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  54. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  55. GRB 250101A: Swift/UVOT Detection
  56. GRB 250101A: 1.6m Mephisto multi-band optical followup
  57. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  58. GRB 250101A: LCOGT optical afterglow detection
  59. GRB 250101A: OASDG optical observations
  60. Fermi GRB 250101B: Global MASTER-Net observations report
  61. GRB 250101A: SAO RAS observations of optical brightening
  62. GRB 250101A: AKO Optical Afterglow Detection
  63. GRB 250101A: SAO RAS optical observations
  64. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  65. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  66. GRB 250101A: SVOM/C-GFT early optical observations
  67. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  68. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  69. GRB 250101A: Nanshan/HMT optical observations
  70. GRB 250101A : GIT optical detection
  71. GRB 250101A: GMG Optical Observation
  72. GRB 241217a/EP241217b: ATCA Radio Detection
  73. EP241217a: VLA Radio Detection

  74. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  75. GRB 241229B: Continued CrAO ZTSh observations
  76. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  77. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  78. LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
  79. GRB 241229A: EP-FXT X-ray afterglow confirmation
  80. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  81. GRB 241229B: SVOM/GRM observation
  82. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  83. EP241217A: J band upper limit by SYSU 80cm telescope
  84. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  85. GRB 241229B: SAO RAS optical upper limit
  86. GRB 241228B: SAO RAS optical observations
  87. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  88. GRB 241229A: SAO RAS optical observations
  89. GRB 241229B: SVOM/VT optical candidate
  90. GRB 241229A: Swift-XRT observations
  91. Konus-Wind detection of GRB 241228A
  92. GRB 241229A: EP-FXT afterglow candidates
  93. EP240702a: 7DT Optical upper limits
  94. GRB 240606B: 7DT Optical upper limits
  95. LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
  96. GRB 241229B: Swift-BAT refined analysis
  97. LIGO/Virgo/KAGRA S241225v: Updated Sky localization
  98. LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
  99. GRB241229B: UVOT upper limits
  100. GRB 241228B: D50 optical detection

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