Skip to main content
New! BOOM Notices and Schema v7.0.0. See news and announcements

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"

27401 results found.

  1. Swift GRB250114A: Global MASTER-Net OT detection
  2. GRB 250114A: LCO optical observations
  3. GRB 250114A: TRT optical observations
  4. GRB 250114A: Swift detection of a burst with an optical counterpart
  5. GRB 250101A: Terskol Zeiss-2000 optical observations
  6. EP250108a / AT 2025kg: SAO RAS optical observations
  7. EP241021a: SMA radio observation
  8. GRB 250113A: SVOM/GRM observation of a long burst
  9. GRB 250107A: VZLUSAT-2 detection
  10. EP250109b: optical upper limits with the Liverpool Telescope
  11. GRB 250106A: Swift-XRT afterglow detection
  12. EP250111a: KAIT optical observations
  13. GRB 250109A / EP250109a: Mephisto optical upper limits
  14. EP250108a: Mephisto detection
  15. EP250111a: Mondy optical observation
  16. EP250108a / AT 2025kg: LCO optical observations
  17. EP250108a / AT 2025kg: Swift UVOT detections
  18. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  19. EP250111a: NOT likely optical counterpart
  20. GRB 250101B: Fermi GBM Observation
  21. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  22. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  23. GRB 250108A: Swift/XRT afterglow fading
  24. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  25. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  26. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  27. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  28. GRB 250101A: CMO RC-500 optical observations
  29. GRB 250109A: Fermi GBM Observation
  30. EP250108a: NOT optical observations
  31. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  32. GRB 250109a: GMG Optical Upper Limit
  33. EP250109a: Swift/UVOT non-detection
  34. IPN triangulation of GRB 250107D (short/hard)
  35. EP250108a: Liverpool Telescope likely optical counterpart
  36. GRB 250108B: Swift-BAT refined analysis
  37. GRB 250108B: 1.3m DFOT upper limit
  38. GRB 250108B: REM optical/NIR upper limits
  39. GRB 250101A: Terskol K-800 optical observations
  40. EP250109a: Swift/XRT non-detection
  41. GRB 250108A: Swift/UVOT Upper Limits
  42. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  43. GRB 250108A: NOT optical upper limit
  44. EP250108a: EP-WXT detection of an X-ray transient
  45. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  46. GRB 250108B: Swift-XRT refined Analysis
  47. GRB 250103A: 1.6m Mephisto optical observations
  48. GRB 250108A: Swift-XRT afterglow detection
  49. GRB 250108A:SVOM/VT optical candidate
  50. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  51. GRB 250108B: Swift/UVOT Upper Limits
  52. GRB 250103A: Swift-XRT afterglow detection
  53. GRB 250108B: Enhanced Swift-XRT position
  54. GRB 250108B: Swift detection of a burst
  55. GRB 250107A: Fermi GBM Observation
  56. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  57. GRB 250106A: SVOM/VT 2nd optical deep observation
  58. GRB 250101A: J band upper limit by SYSU 80cm telescope
  59. EPWXT01709129925: Xinglong optical observations
  60. GRB 250106A: NOT optical observations
  61. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  62. GRB 250103B: REM optical/NIR upper limits
  63. GRB 250101A: REM optical/NIR counterpart detection
  64. GRB 250106A: Swift-XRT observations
  65. GRB 250106A: SVOM/VT optical candidate
  66. The EP-WXT trigger 01709129925 is likely a flaring star
  67. GRB 250103B: Swift-XRT refined Analysis
  68. GRB 250103B: LCO/1m optical afterglow candidate detection
  69. GRB 250103A: Bassano Bresciano Observatory upper limit
  70. GRB 250103A: Swift-XRT observations
  71. GRB 250101A: 1.3m DFOT optical afterglow detection
  72. GRB 241229A: 1.3m DFOT upper limit
  73. GRB 241228B: 1.3m DFOT Optical observations
  74. GRB 241228A: 1.3m DFOT upper limit
  75. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  76. GRB 250103A: Montarrenti Observatory optical detection
  77. GRB 250101A: further LCOGT optical afterglow observations
  78. GRB 250103A: TSHAO optical upper limit
  79. GRB 250103A: Fermi GBM Observation
  80. GRB 250103B: LCOGT Optical Upper Limit
  81. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  82. EP250101a: Liverpool Telescope optical upper limit
  83. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  84. GRB 250101a: Liverpool Telescope optical follow-up
  85. GRB 250103B: Swift detection of a burst
  86. GRB 250103A: Xinglong 2.16m Optical Candidate
  87. GRB 250101B: SVOM/GRM observation
  88. GRB 250103A: GOTO optical upper limit
  89. GRB 250103A: SVOM/C-GFT optical upper limit
  90. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  91. EP241231b: optical upper limit with the Liverpool Telescope
  92. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  93. GRB 250103A: SVOM detection of a long burst
  94. EP250101a: Xinglong optical upper limit
  95. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  96. GRB 250101A: Swift-BAT refined analysis
  97. GRB 250101A: further SAO RAS optical observations
  98. GRB 250101A: LCO optical counterpart detection
  99. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  100. GRB 250101A: Swift/UVOT Detection

Advanced

Download all Circulars as a .tar.gz archive:
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov