Early Observations and Detection of GRB 180812A

06 July 2018

Last night we observed the optical counterpart of the long gamma-ray burst GRB 180812A which was detected by the Neil Gehrels Swift Observatory.

COATLI slewed quickly to the burst coordinates, and our first exposure started 43.1 seconds after the burst detection or 11.6 seconds after receiving the automatic alert.

The counterpart was bright, and we detected it in our first few images at w ≈ 17.4, brightening gradually to w ≈ 17.2 at about 160 seconds, and then fading rapidly. We reported our results in a GCN Circular.

Our observations of GRB 180812A.

Our image of the field of GRB 180812A. The red circle is the region with a 90% probability of containing the GRB, derived from Swift/XRT detection. We detect the optical counterpart. The image is about 2 arcmin to a side.

This burst could not have been observed by our sister project RATIR because of its northern declination (+75 degrees). However, it was observed by the BOOTES-5/JGT telescope also at the Observatorio Astronómico Nacional starting about 10 seconds after our observations.


Observations and Detection of GRB 180806A

07 August 2018

Most of our observations of gamma-ray bursts are initiated automatically when the COATLI control system receives a automatic notification from the Neil Gehrels Swift Observatory.

Our observations of GRB 180806A last night were exceptional. One of our team members woke up early and checked email. There was a message from our colleague Vladimir Lipunov noting that his team had found a possible optical counter part to a gamma-ray burst detected by the Fermi Gamma-ray Space Telescope. Our team member immediately interrupted routine observations and programmed an observation of the possible counterpart.

We detected the counterpart at w = 20.0 ± 0.2 (later refined to w = 20.22 ± 0.05) and confirmed fading compared to Lipunov’s earlier observation. We reported our results in a GCN Circular.

Subsequent observations in X-rays by Swift confirmed that this indeed was the counterpart of GRB 180606A.

Our observations of GRB 180806A.

Our image of the possible counterpart of GRB 180806A. The red circle shows the position of the possible counterpart found by the MASTER team. The image is about 3 arcmin to a side.


Observations of GRB 180805B

06 August 2018

Last night we observed the field of the short gamma-ray burst GRB 180805B which was detected by the Neil Gehrels Swift Observatory.

This was not one of our quick responses; the GRB occurred just after sunrise in Mexico, so our observations were from 19 to 23 hours after the burst.

We did not detect any optical counterpart to a limiting magnitude of w > 22.5 (5σ), and reported this in a GCN Circular.

Our observations of GRB 180805B.

Our image of the field of GRB 180805B. The red circle is the region with a 90% probability of containing the GRB, derived from Swift/XRT detection. The image is about 2 arcmin to a side.


First COATLI Science Paper Submitted!

02 August 2018

The first paper containing COATLI science observations has been submitted to MNRAS and arXiv! The paper is lead by Dan Perley and is an investigation into the mysterious transient AT2018cow. COATLI contributed photometry in BVRI.


Observations and Detection of GRB 180720B

22 July 2018

Last night we observed the optical counterpart of the long gamma-ray burst GRB 180720B which was detected by the Neil Gehrels Swift Observatory.

The burst occurred shortly after sunrise in Mexico on 21 July 2018. The optical counterpart was initially very bright: it was observed at R ≈ 9.4 at very early times by colleagues using a telescope in Japan. We monitored the burst with COATLI on subsequent nights. We detected the optical counterpart in observations from 2018 July 22 at w = 20.07 ± 0.02, and reported this in a GCN Circular.

Our observations of GRB 180720B.

Our image of the field of GRB 180720B. The red circle is the region with a 90% probability of containing the GRB, derived from Swift/XRT detection. We detect the optical counterpart, on the northern edge of the Swift/XRT region. The image is about 2.3 arcmin to a side.


Observations of GRB 180715A

16 July 2018

Last night we observed the field of the short gamma-ray burst GRB 180715A which was detected by the Neil Gehrels Swift Observatory.

Unusually, Swift was not able to quickly slew to the position of the GRB to observe in X-rays with XRT. Yet more unusually, once it was able to slew, no obvious X-ray counterpart was detected. However, XRT did detect five faint sources in the vicinity of the GRB, and one of these might correspond to the GRB afterglow. This result was published almost 30 hours after the burst.

Our observations of GRB 180715A were not one of our quick responses; the GRB occurred during the day in Mexico, so our observations were from 10 to 14 hours after the burst. Furthermore, we initially weren’t sure what they were telling us. With only BAT observations from Swift, the uncertainty in the position of the GRB is about 3 arcmin in radius (90%). We saw no bright source in that region, but the afterglow could have been hiding in the glare of the nearby magnitude 8 star HD 139840.

However, once the Swift team had published the coordinates of the five faint X-ray sources, we were able to confirm that absence of coincident optical sources to w > 22.3 (5σ), and reported this in a GCN Circular.

Our observations of GRB 180706A.

Our image of the field of GRB 180715A. The blue circle is the region with a 90% probability of containing the GRB, derived from Swift/BAT detection. The five red circles are the Swift/XRT faint sources. The bright star is HD 139840. The image is about 9 arcmin to a side.


Early Observations of GRB 180709A

09 July 2018

Last night we observed the field of the long gamma-ray burst GRB 180709A which was detected by the Neil Gehrels Swift Observatory.

COATLI slewed quickly to the burst coordinates, and our first exposure started 65.4 seconds after the burst detection or 14.5 seconds after receiving the automatic alert.

We did not detect the optical counterpart to a limiting magnitude of w > 21.3 (3σ), and reported this in a GCN Circular.

Our observations of GRB 180709A.

Our image of the field of GRB 180719A. The red circle is the region with a 90% probability of containing the GRB, derived from Swift/XRT detection. We do not detect the optical counterpart. The image is about 2.4 arcmin to a side.

This burst could not have been observed by our sister project RATIR because of its northern declination (+60 degrees).


Early Observations and Detection of GRB 180706A

06 July 2018

July continues as June ended. Last night we observed the optical counterpart of the long gamma-ray burst GRB 180706A which was detected by the Neil Gehrels Swift Observatory.

COATLI slewed quickly to the burst coordinates, and our first exposure started 46.4 seconds after the burst detection or 29.5 seconds after receiving the automatic alert.

The counterpart was bright, and we detected it in our first few images at w = 18.73 ± 0.08, and reported this in a GCN Circular. Fading was confirmed by colleagues using a telescope in Kazakstan.

Our observations of GRB 180706A.

Our image of the field of GRB 180706A. The red circle is the region with a 90% probability of containing the GRB, derived from Swift/XRT detection. We detect the optical counterpart. The image is about 2.3 arcmin to a side.

Our observations of this burst were interesting for a couple of reasons.

First, the speed of our response. The burst was detected by Swift at 01:24 PDT. One of our team members was up working, and was able to confirm the detection in our real-time pipeline reduction at 01:44 PDT, even before we received the Swift discovery GCN by email at 01:51 PDT. Nevertheless, we waited for the Swift GCN in order to confirm the identity and nature of this GRB, and sent our GCN Circular at 02:03 PDT.

Second, the GRB occurred under the pole! We started observing at +66 degrees of declination and an hour angle of +7.5 hours and finished observations at an hour angle of +10.5 hours.

This burst could not have been observed by our sister project RATIR because of its northern declination (+66 degrees) and HA (+7.5 hours and increasing).


Early Observations and Detection of GRB 180626A

26 June 2018

June contines to be a busy month. Last night we observed the optical counterpart of the gamma-ray burst GRB 180626A which was detected by the Neil Gehrels Swift Observatory.

COATLI slewed quickly to the burst coordinates, and our first exposure started 33.7 seconds after the burst detection or 17.9 seconds after receiving the automatic alert.

The counterpart was quite faint, but nevertheless we managed to obtain a marginal detection at w = 21.4 ± 0.9, and reported this in a GCN Circular. This is our deepest detection to date.

Our observations of GRB 180626A.

Our image of the field of GRB 180626A. The red circle is the region with a 90% probability of containing the GRB, derived from Swift/XRT detection. We detect the optical counterpart. The image is about 2.3 arcmin to a side.

The image quality is still degraded by wind shake and poor mirrors — our final image had a FWHM of about 2.8 arcsec. Once we achieve seeing-limited images we expect to be able to take images that are about a factor of 3 deeper.


The Mysterious Transient AT2018cow/ATLAS18qqn

21 June 2018

Last night we observed the mysterious bright transient source AT2018cow/ATLAS18qqn with COATLI. This transient was discovered by the ATLAS group in a nearby galaxy at a distance of about 60 Mpc, and its nature is not at all clear.

We detected the transient at r ≈ 14.9, saw it fade by about 0.1 magnitudes during the night, and have reported our observations as an ATel. We plan to keep monitoring.

Our observations of AT2018cow.

Our image of the field of AT2018cow/ATLAS18qqn. The image has about 30 minutes of exposure in R and is about 6 arcmin to a side.


Early Observations and Detection of GRB 180620A

20 June 2018

Last night we observed the optical counterpart of the gamma-ray burst GRB 180620A which was detected by the Neil Gehrels Swift Observatory.

COATLI slewed quickly to the burst coordinates, and our first exposure started 39.2 seconds after the burst detection or 21.1 seconds after receiving the automatic alert.

We detected the counterpart at w ≈ 17.5, saw a rapid initial fade in brightness, then a flare, and then a slower fade during the next three hours. We have reported our observations as a GCN Circular.

Our observations of GRB 180620A.

Our image of the field of GRB 180620A. The red circle is the region with a 90% probability of containing the GRB, derived from Swift/XRT detection. We detect the optical counterpart. The image is about 2.3 arcmin to a side.

We are writing a research article combining our early data with the deeper data we obtained with RATIR.


Shutter Failure

18 April 2018

The shutter failed open on the night of 18 April 2018 UTC. Carlos Tejada and Tomás Calvario checked it the next day and found that a spider had taken up residence! After removing the spider, the shutter is working normally again.

The spider in the shutter.

The spider in the shutter.


Early Observations and Detection of GRB 180205A

5 February 2018

Last night we observed the optical counterpart of the gamma-ray burst GRB 180205A with was detected by the Neil Gehrels Swift Observatory.

COATLI slewed quickly to the burst coordinates, and our first exposure started 6.5 seconds after receiving the automatic alert. Unfortunately, a problem with satellite telemetry mean that the automatic alert was delayed, so the first exposure started 212.8 seconds after the burst detection.

We detected the counterpart at w ≈ 15.6.

We are writing a research article comparing our optical data to the X-ray and gamma-ray data obtained by Swift and Fermi.